• Awaka, J., , T. Iguchi, , and K. Okamoto, 1998: Early results on rain type classification by the Tropical Rainfall Measuring Mission (TRMM) precipitation radar. Proc., Eighth URSI Commission F Open Symp., Aveiro, Portugal, URSI, 143–146.

  • Cecil, D. J., , and E. J. Zipser, 2002: Reflectivity, ice scattering, and lightning characteristics of hurricane eyewalls and rainbands. Part II: Intercomparison of observations. Mon. Wea. Rev., 130 , 785801.

    • Search Google Scholar
    • Export Citation
  • Cecil, D. J., , E. J. Zipser, , and S. W. Nesbitt, 2002: Reflectivity, ice scattering, and lightning characteristics of hurricane eyewalls and rainbands. Part I: Quantitative description. Mon. Wea. Rev., 130 , 769784.

    • Search Google Scholar
    • Export Citation
  • Christian, H. J., and Coauthors, 1999: The Lightning Imaging Sensor. Proc. 11th Int. Conf. on Atmospheric Electricity, Guntersville, AL, International Commission on Atmospheric Electricity, 746–749.

  • Dodge, P., , R. W. Burpee, , and F. D. Marks Jr., 1999: The kinematic structure of hurricane with sea level pressure less than 900 mb. Mon. Wea. Rev., 127 , 9871004.

    • Search Google Scholar
    • Export Citation
  • Emanuel, K. A., 2005: Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436 , 686688.

  • Hasegawa, A., , and S. Emori, 2005: Tropical cyclones and associated precipitation over the western North Pacific in present and doubled CO2 climates simulated by a T106 atmospheric GCM. SOLA, 1 , 145148.

    • Search Google Scholar
    • Export Citation
  • Hood, R. E., and Coauthors, 2006: Classification of tropical oceanic precipitation using high-altitude aircraft microwave and electric field measurements. J. Atmos. Sci., 63 , 218233.

    • Search Google Scholar
    • Export Citation
  • Houze Jr., R. A., 1977: Structure and dynamics of a tropical squall-line system. Mon. Wea. Rev., 105 , 15401567.

  • Houze Jr., R. A., 1982: Cloud clusters and large-scale vertical motions in the tropics. J. Meteor. Soc. Japan, 60 , 396410.

  • Houze Jr., R. A., 1989: Observed structure of mesoscale convective systems and implications for large-scale heating. Quart. J. Roy. Meteor. Soc., 115 , 425461.

    • Search Google Scholar
    • Export Citation
  • Houze Jr, R. A., 1993: Cloud Dynamics. Academic Press, 337 pp.

  • Houze Jr., R. A., 2004: Mesoscale convective systems. Rev. Geophys., 42 .RG4003, doi:10.1029/2004RG000150.

  • Houze Jr., R. A., , and C. A. Leary, 1976: Comparison of convective mass and heat transports in tropical easterly waves computed by two methods. J. Atmos. Sci., 33 , 424429.

    • Search Google Scholar
    • Export Citation
  • Iguchi, T., , T. Kozu, , R. Meneghini, , J. Awaka, , and K. Okamoto, 2000: Rain-profiling algorithm for the TRMM precipitation radar. J. Appl. Meteor., 39 , 20382052.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., 1984a: Mesoscale and convective-scale characteristics of mature hurricanes. Part I: General observations by research aircraft. J. Atmos. Sci., 41 , 12681286.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., 1984b: Mesoscale and convective-scale characteristics of mature hurricanes. Part II: Inner core structure of Hurricane Allen (1980). J. Atmos. Sci., 41 , 12871311.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., , and M. A. LeMone, 1989: Vertical velocity characteristics of oceanic convection. J. Atmos. Sci., 46 , 621640.

  • Jorgensen, D. P., , E. J. Zipser, , and M. A. LeMone, 1985: Vertical motions in intense hurricanes. J. Atmos. Sci., 42 , 839856.

  • Kempf, N. M., , and E. P. Krider, 2003: Cloud-to-ground lightning and surface rainfall during the great flood of 1993. Mon. Wea. Rev., 131 , 11401149.

    • Search Google Scholar
    • Export Citation
  • Knutson, T. R., , and R. E. Tuleya, 2004: Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. J. Climate, 17 , 34773495.

    • Search Google Scholar
    • Export Citation
  • Kummerow, C., , W. Barnes, , T. Kozu, , J. Shiue, , and J. Simpson, 1998: The Tropical Rainfall Measuring Mission (TRMM) sensor package. J. Atmos. Oceanic Technol., 15 , 809817.

    • Search Google Scholar
    • Export Citation
  • Kummerow, C., and Coauthors, 2000: The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. J. Appl. Meteor., 39 , 19651982.

    • Search Google Scholar
    • Export Citation
  • Leary, C. A., , and R. A. Houze Jr., 1979: Melting and evaporation of hydrometeors in precipitation from the anvil clouds of deep tropical convection. J. Atmos. Sci., 36 , 669679.

    • Search Google Scholar
    • Export Citation
  • Leary, C. A., , and R. A. Houze Jr., 1980: The contribution of mesoscale motion to the mass and heat fluxes of an intense tropical convective system. J. Atmos. Sci., 37 , 784796.

    • Search Google Scholar
    • Export Citation
  • LeMone, M. A., , and E. J. Zipser, 1980: Cumulonimbus vertical velocity events in GATE. Part I: Diameter, intensity and mass flux. J. Atmos. Sci., 37 , 24442457.

    • Search Google Scholar
    • Export Citation
  • Lin, J., , B. Mapes, , M. Zhang, , and M. Newman, 2004: Stratiform precipitation, vertical heating profiles, and the Madden–Julian oscillation. J. Atmos. Sci., 61 , 296309.

    • Search Google Scholar
    • Export Citation
  • Lonfat, M., , F. D. Marks Jr., , and S. S. Chen, 2004: Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager: A global perspective. Mon. Wea. Rev., 132 , 16451660.

    • Search Google Scholar
    • Export Citation
  • Lucas, C., , E. J. Zipser, , and M. A. LeMone, 1994: Vertical velocity in oceanic convective off tropical Australia. J. Atmos. Sci., 51 , 31833193.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., , and R. A. Houze Jr., 1993: Cloud clusters and superclusters over the oceanic warm pool. Mon. Wea. Rev., 121 , 13981415.

  • Marks Jr., F. D., 1985: Evolution of the structure of precipitation in Hurricane Allen (1980). Mon. Wea. Rev., 113 , 909930.

  • Marks Jr, F. D., 2003: State of the science: Radar view of tropical cyclones. Cloud Systems, Hurricanes, and the Tropical Rainfall Measuring Mission (TRMM): A Tribute to Dr. Joanne Simpson, Meteor. Monogr., No. 51, Amer. Meteor. Soc., 33–74.

    • Search Google Scholar
    • Export Citation
  • Marks Jr., F. D., , and R. A. Houze Jr., 1987: Inner core structure of Hurricane Alicia from airborne Doppler radar observations. J. Atmos. Sci., 44 , 12961317.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., , P. Moore, , and V. Idone, 1999: Convective structure of hurricanes as revealed by lightning locations. Mon. Wea. Rev., 127 , 520534.

    • Search Google Scholar
    • Export Citation
  • Morita, J., , Y. N. Takayabu, , S. Shige, , and Y. Kodama, 2006: Analysis of rainfall characteristics of the Madden–Julian oscillation using TRMM satellite data. Dyn. Atmos. Oceans, 42 , 107126.

    • Search Google Scholar
    • Export Citation
  • Oouchi, K., , J. Yoshimura, , H. Yoshimura, , R. Mizuta, , S. Kusunoki, , and A. Noda, 2006: Tropical cyclone climatology in a global-warming climate as simulated in a 20 km-mesh global atmospheric model: Frequency and wind intensity analyses. J. Meteor. Soc. Japan, 84 , 259276.

    • Search Google Scholar
    • Export Citation
  • Petersen, W. A., , and S. A. Rutledge, 1998: On the relationship between cloud-to-ground lightning and convective rainfall. J. Geophys. Res., 103 , 1402514040.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , and R. F. Adler, 1981: Tropical cyclone rainfall characteristics as determined from a satellite passive microwave radiometer. Mon. Wea. Rev., 109 , 506521.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , R. F. Adler, , and H. F. Pierce, 2000: Contribution of tropical cyclones to the North Pacific climatological rainfall as observed from satellites. J. Appl. Meteor., 39 , 16581678.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , R. F. Adler, , and H. F. Pierce, 2001: Contribution of tropical cyclones to the North Atlantic climatological rainfall as observed from satellites. J. Appl. Meteor., 40 , 17851800.

    • Search Google Scholar
    • Export Citation
  • Schumacher, C., , and R. A. Houze Jr., 2003: The TRMM precipitation radar’s view of shallow, isolated rain. J. Appl. Meteor., 42 , 15191524.

    • Search Google Scholar
    • Export Citation
  • Shige, S., , Y. N. Takayabu, , W-K. Tao, , and D. E. Johnson, 2004: Spectral retrieval of latent heating profiles from TRMM PR data. Part I: Development of a model-based algorithm. J. Appl. Meteor., 43 , 10951113.

    • Search Google Scholar
    • Export Citation
  • Sugi, M., , A. Noda, , and N. Sato, 2002: Influence of the global warming on tropical cyclone climatology: An experiment with the JMA global model. J. Meteor. Soc. Japan, 80 , 249272.

    • Search Google Scholar
    • Export Citation
  • Szoke, E. J., , E. J. Zipser, , and D. P. Jorgensen, 1986: A radar study of convective cells in mesoscale systems in GATE. Part I: Vertical profile statistics and comparison with hurricanes. J. Atmos. Sci., 43 , 182197.

    • Search Google Scholar
    • Export Citation
  • Takahashi, T., 1978: Riming electrification as a charge mechanism in thunderstorms. J. Atmos. Sci., 35 , 15361548.

  • Takahashi, T., 1984: Thunderstorm electrification—A numerical study. J. Atmos. Sci., 41 , 25412558.

  • Takayabu, Y. N., 2002: Spectral representation of rain profiles and diurnal variations observed with TRMM PR over the equatorial area. Geophys. Res. Lett., 29 .1584, doi:10.1029/2001GL014113.

    • Search Google Scholar
    • Export Citation
  • Takayabu, Y. N., 2006: Rain-yield per flash calculated from TRMM PR and LIS data and its relationship to the contribution of tall convective rain. Geophys. Res. Lett., 33 .L18705, doi:10.1029/2006GL027531.

    • Search Google Scholar
    • Export Citation
  • Wang, K-Y., , and S-A. Liao, 2006: Lightning, radar reflectivity, infrared brightness temperature, and surface rainfall during the 2–4 July 2004 severe convective system over Taiwan area. J. Geophys. Res., 111 .D05206, doi:10.1029/2005JD006411.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., , G. J. Holland, , J. A. Curry, , and H-R. Chang, 2005: Changes in tropical cyclone number, duration, and intensity in a warming environment. Science, 309 , 18441846.

    • Search Google Scholar
    • Export Citation
  • Williams, E. R., , S. A. Rutledge, , S. C. Geotis, , N. Renno, , E. Rasmussen, , and T. Rickenbach, 1992: A radar and electrical study of tropical hot towers. J. Atmos. Sci., 49 , 13861395.

    • Search Google Scholar
    • Export Citation
  • Yuter, S. E., , and R. A. Houze Jr., 1998: The natural variability of precipitating clouds over the western Pacific warm pool. Quart. J. Roy. Meteor. Soc., 124 , 5399.

    • Search Google Scholar
    • Export Citation
  • Zipser, E. J., 1977: Mesoscale and convective-scale downdrafts as distinct components of squall-line structure. Mon. Wea. Rev., 105 , 15681589.

    • Search Google Scholar
    • Export Citation
  • Zipser, E. J., , and M. A. LeMone, 1980: Cumulonimbus vertical velocity events in GATE. Part II: Synthesis and model core structure. J. Atmos. Sci., 37 , 24582469.

    • Search Google Scholar
    • Export Citation
  • View in gallery

    Time series of the best-track data every 6 h. The composites of individual best-track data, which are normalized with the mean length for each stage of each class, are shown in class (a) 1, (b) 2, (c) 3, and (d) 4. All time series are denoted by gray lines and mean time series by black line. Vertical lines indicate the section of each stage. Tropical cyclones observed by TRMM satellite once at least from December 1997 to December 2003 are analyzed.

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    The numbers of center positions obtained from the best-track data every 6 h, and the numbers of TRMM TC observations, according to latitudinal regions from 35°S to 35°N. Analysis duration is from January 1998 to December 2003.

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    Histograms of (a) pixel numbers and (b) rain amounts binned into rain rates over ocean. Rain rates are shown in dBR scale of 10 × log10(rain rate). The rightmost bin includes rain rates over 24 dBR. Thick lines and thin lines denote distributions of TCs and the equatorial mean, respectively. Solid lines and dashed lines denote stratiform rain and convective rain, respectively.

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    Contribution to the total near-surface rainfall from RTH over (a) ocean and (b) land. Lines are depicted as in Fig. 3.

  • View in gallery

    Spectral representations of rain profiles in the equatorial mean for (a) oceanic convective, (b) continental convective, (c) oceanic stratiform, and (d) continental stratiform, which are basically the same as in Takayabu (2002), but with the reclassification of shallow isolated rain from stratiform to convective after Schumacher and Houze (2003). Rain profiles at the nadir pixels observed by PR are accumulated in the equatorial region from January 1998 to December 2000, and then sorted with RTH. Colors represent conditional mean rain-rate profiles for each fixed RTH value. Ordinate axis indicates altitudes, and abscissa indicates cumulative frequencies. (a) and (c) The same as Fig. 2 of Shige et al. (2004).

  • View in gallery

    The same as Fig. 5, but for TCs. Seven pixels around the nadir are utilized.

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    Radial distributions of mean rain rates derived by (a) PR and (b) TMI at the mature stage. Mean rain rate is obtained from unconditionally averaging rain rate over each 10-km-wide annular region. Solid lines with error bars denote composites for classes 4 (c4), 3 (c3), and 2 (c2), respectively. A line without error bars is for the average over classes 2–4. Error bars show the 90% confidence intervals.

  • View in gallery

    The radial distributions of SRR derived by PR at the (top) developing, (middle) mature, and (bottom) decaying. SRR is the percentage of total stratiform rain in the total rainfall over each annular region. Lines with open circles, filled circles, and open triangles denote distributions of class 4, 3, and 2, respectively. Gray lines are for the average over classes 2–4.

  • View in gallery

    Radial distributions of the contribution to the total near-surface rainfall from RTH at the mature stage, for class (top) 2, (middle) 3, and (bottom) 4. Distributions of (left) convective rain and (right) stratiform rain. The contributions are denoted by shaded colors.

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    Radial distributions of (a) flash rates and (b) RPF. Flash rate is number of observed flashes divided by observed time, and RPF is ratio of mean rain rate to flash rate in each annular region. Lines are depicted as in Fig. 8.

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    Fig. A1. Histograms of rain amounts binned into rain rates for TCs over ocean with version 6 data. Rain rates are shown in dBR scale of 10 × log10(rain rate). The rightmost bin includes rain rates over 24 dBR. Thick lines and thin lines denote distributions of TCs and the equatorial mean, respectively. Solid lines and dashed lines denote stratiform rain and convective rain, respectively. Analysis duration is from December 1997 to December 2003.

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A Statistical Study on Rain Characteristics of Tropical Cyclones Using TRMM Satellite Data

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  • 1 Center for Climate System Research, University of Tokyo, Kashiwa, Chiba, Japan
  • | 2 Center for Climate System Research, University of Tokyo, Kashiwa, Chiba, and Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
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Abstract

Three-dimensional rain characteristics of tropical cyclones (TCs) are statistically quantified, using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2003. Tropical cyclones are classified into four maximum intensity classes (<34, 34–64, 64–128, and ≥128 kt) and three stages (developing, mature, and decaying). First, rain characteristics of TCs are compared with those of the equatorial (10°N–10°S) mean. A notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 52%, while it is 44% for the equatorial oceanic mean and 46% for the Madden–Julian oscillation in its mature phase. Stronger rain is observed in TCs both for convective and stratiform rain. Second, radial rain characteristics of TCs suggest that the region 0–60 km can be classified as “the inner core,” and 60–500 km as “the rainband.” The inner core is characterized with small SRR, very high rain-top height, and a large flash rate, indicating the vigor of convective activity. In contrast, the rainband is characterized with large SRR and relatively large rain yield per flash, indicating a large rainfall amount with a moderate convective activity. An important implication of this study is that TCs are listed in the high end of tropical oceanic organized rain systems, in terms of the organization levels of rain. Last, we use the above composite results to calculate the rainfall contribution of TCs to total annual rainfall between 35°N and 35°S as 3.3% ± 0.1%.

Corresponding author address: Chie Yokoyama, Center for Climate System Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan. Email: yokoyama@ccsr.u-tokyo.ac.jp

Abstract

Three-dimensional rain characteristics of tropical cyclones (TCs) are statistically quantified, using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2003. Tropical cyclones are classified into four maximum intensity classes (<34, 34–64, 64–128, and ≥128 kt) and three stages (developing, mature, and decaying). First, rain characteristics of TCs are compared with those of the equatorial (10°N–10°S) mean. A notable finding here is that the average stratiform rain ratio (SRR), which is the contribution from stratiform rain in the total rainfall, of TCs is 52%, while it is 44% for the equatorial oceanic mean and 46% for the Madden–Julian oscillation in its mature phase. Stronger rain is observed in TCs both for convective and stratiform rain. Second, radial rain characteristics of TCs suggest that the region 0–60 km can be classified as “the inner core,” and 60–500 km as “the rainband.” The inner core is characterized with small SRR, very high rain-top height, and a large flash rate, indicating the vigor of convective activity. In contrast, the rainband is characterized with large SRR and relatively large rain yield per flash, indicating a large rainfall amount with a moderate convective activity. An important implication of this study is that TCs are listed in the high end of tropical oceanic organized rain systems, in terms of the organization levels of rain. Last, we use the above composite results to calculate the rainfall contribution of TCs to total annual rainfall between 35°N and 35°S as 3.3% ± 0.1%.

Corresponding author address: Chie Yokoyama, Center for Climate System Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan. Email: yokoyama@ccsr.u-tokyo.ac.jp

1. Introduction

Precipitation of tropical cyclones (TCs) often causes extensive damage to society. Marks (2003) emphasized that a comprehensive understanding of TC precipitation climatology is essential in order to improve quantitative precipitation forecasts of TCs, but it has not been really investigated in all TC basins. Tropical Rainfall Measuring Mission (TRMM) satellite data are therefore useful to address this issue. TRMM has observed rain over the entire 35°N–35°S latitude band since December 1997, so that more detailed distributions of TC rain can be studied. Lonfat et al. (2004) showed both radial and azimuthal distributions of TC rain significantly varied according to basins and intensities, utilizing TRMM Microwave Imager (TMI) data.

TC rain consists of a convective regime in the eyewall and both stratiform and convective rain in the outer region (Jorgensen 1984a, b; Marks 1985; Marks and Houze 1987). Dodge et al. (1999) showed that Hurricane Gilbert in 1988 consisted of inner and outer eyewalls, a stratiform region between the eyewalls, and an outer region that included a few rainbands but mostly stratiform rain. Marks (1985) suggested that the contribution of the eyewall rain to the total rainfall within 111 km of the center was constant and near 40%, during the evolution of Hurricane Allen in 1980.

Mature mesoscale convective systems (MCSs) such as cloud clusters and squall lines also consist of convective and large stratiform rain areas (e.g., Houze 1989), and TCs are similar to MCSs in that sense. For squall lines observed during the Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE), stratiform rain contributed about 40% of the total rainfall on average (Houze 1977). In addition, Zipser (1977) emphasized that stratiform clouds in organized systems were not thin cirrus but clouds with 6–10-km thickness. Jorgensen and LeMone (1989) showed that TC rainbands over the ocean were similar to oceanic MCSs during the Taiwan Area Mesoscale Experiment (TAMEX) program and GATE, but were much weaker than midlatitude thunderstorms, in terms of updraft in the convective core defined by LeMone and Zipser (1980). The difference is also shown in profiles of radar reflectivity (Szoke et al. 1986). Other studies consistently showed that convective activity was relatively modest in TC rainbands (Zipser and LeMone 1980; Jorgensen et al. 1985; Lucus et al. 1994; Cecil et al. 2002).

In this study, we put emphasis on the stratiform rain ratio (SRR), which is defined as the ratio of the stratiform rainfall to the total rainfall, as one index used to characterize the rain in TCs. The first reason is because it is suggested that the stratiform region plays an important role in organizing MCSs. Yuter and Houze (1998) and Houze (2004) suggested that the large stratiform region was sustained by the environment, which can maintain continuous formation of convective cells. Houze (2004) also suggested that the mesoscale convective vortices in the stratiform region of the MCSs could sometimes become the origin of TC circulations. Studies of the stratiform region have the potential to understand the environment of TCs and MCSs. Therefore, a very important problem is what kind of environment controls SRR. Second, latent heating profiles in the stratiform region are different from those of convective region (e.g., Houze 1982). Houze (1982) showed that condensation heating was dominant thorough the whole depth of the troposphere in convective regions. In stratiform regions, on the other hand, it was shown that condensation heating occurred aloft and cooling associated with the evaporation and melting occurred below the cloud base, which is found near the melting level. For these reasons, stratiform rain is given much attention in this study. The first TRMM satellite-borne precipitation radar (PR) allows us to observe three-dimensional rain both over ocean and over land consistently, and to obtain the statistics of stratiform rain. Three-dimensional observations of rain enable us a more explicit classification of rain types into convective and stratiform than before. It is also an advantage of TRMM that we can analyze rain utilizing various sensors such as the TMI and the Lightning Imaging Sensor (LIS) that are on board together with PR.

TC rain has been studied by various methods. Hood et al. (2006) analyzed passive microwave observations at four frequencies and the electric field information to identify the convective rain region. They also utilized the technique to discuss a variety of precipitation types of Hurricane Bonnie in 1998. Wang and Liao (2006) concluded that high-level reflectivity, very low cloud-top temperatures, and intensive intracloud lightning were produced by a strong updraft in Typhoon Mindulle in 2004. Molinari et al. (1999) showed that more lightning was produced in outer rainbands than eyewalls or inner rainbands. Cecil et al. (2002) analyzed radar reflectivity, ice scattering, and lightning derived from TRMM to show that the inner rainband region yielded the weakest convective signatures. Cecil and Zipser (2002) examined the relationship between these characteristics to show a schematic depicting vertical microphysical profiles in eyewall and outer rainband regions.

On the other hand, there is a growing interest on the future change of TC numbers and intensities in association with global warming (e.g., Knutson and Tuleya 2004; Emanuel 2005; Webster et al. 2005). Global warming experiments using general circulation models (GCMs) are often performed to study this issue. Sugi et al. (2002) and Oouchi et al. (2006) simulated a decrease of frequency of TCs, while Hasegawa and Emori (2005) simulated an increase of TC rainfall. However, “TCs” in GCMs may not be necessarily realistic, because “convection” must be parameterized in very coarse grids of GCMs. To examine the ability of GCMs to simulate a TC rain, quantitative validation is essential. As one of such statistics, the contribution of TC rainfall that Rodgers et al. (2000, 2001) estimated over the North Pacific and North Atlantic Oceans can be utilized. However, the contribution of TC rainfall over the entire tropics has not yet been examined.

The first objective of this study is to describe statistically the three-dimensional rain structure and characteristics of TC rain using TRMM PR, TMI, and LIS data. First of all, we compare rain characteristics of TCs with those of the average rain between 10°N and 10°S (hereinafter the equatorial mean). Second, we analyze how the characteristics of rain vary radially, according to TCs classes and stages. Third, we estimate the contribution of TCs to the total rainfall in the entire TRMM region. To study rain characteristics of TCs, we utilize statistics such as SRR and rain-top height (RTH) used by Takayabu (2002) and rain yield per flash (RPF) proposed by Williams et al. (1992), calculated with TRMM data in the entire TRMM region by Takayabu (2006). RPF, which is rainfall divided by the number of flashes, can be a good index for rain regimes (Petersen and Rutledge 1998; Takayabu 2006).

2. Data

a. TRMM data

Since December 1997, TRMM has observed rain with multiple sensors. There is an advantage of utilizing TRMM satellite to obtain three-dimensional rain structures in the entire region between 35°N and 35°S. In this study, we utilize data derived from the PR, TMI, and LIS. Details of PR and TMI algorithms are given in Iguchi et al. (2000) and Kummerow et al. (1998, 2000). Rain-detected pixels are classified into stratiform, convective, or other rain, according to the PR2A23 algorithm (Awaka et al. 1998). Note that shallow and isolated “stratiform rain” is all reclassified as convective rain in this study, following Schumacher and Houze (2003).

LIS is an optical sensor used to detect both intracloud and cloud-to-ground lightning, with a horizontal resolution of 3–6 km and a field of view of 550 × 550 km2. Almost all locations observed by LIS are viewed for about 90 s. Latitude, longitude, and view time are provided for each individual pixel with a flash. From the information, we can calculate the flash rate by dividing the number by the view time in a given area, and then investigate its relationship with rain derived from PR and TMI. Details of LIS are found in Christian et al. (1999).

We utilize PR2A25, version 5, and TMI2A12, version 5, data from the TRMM Tropical Cyclones Database for the analysis of TC rain. Note that version 5 data are no longer the current version, and version 6 data are now available. However, we speculate that version 5 data provide a more distinct classification of convective and stratiform rain than version 6 in the case of TCs. The histograms of rain amount binned into rain rates for TCs with version 6 data are shown in the appendix. The stratiform histograms considerably overlap the convective one for version 6 data (Fig. A1) compared to version 5 data (Fig. 3b, thick lines). Therefore, we use version 5 data in this study.

The TC database is produced by the Japan Aerospace Exploration Agency (JAXA)/Earth Observation Research and application Center (EORC). The procedure by the JAXA/EORC to extract the TC data is as follows. First, contiguous rain areas are detected with PR data. When one such area is within ±5° latitude and longitude of any other areas, the largest rectangular rain area including all areas is considered as one rain area. Then, if a TC center exists in a rectangular region within ±5° latitude and longitude of the rectangular rain area during 6 h before or after the full-orbit observation time, the region is cut out as a TC region from full-orbit path data. This procedure of JAXA/EORC for creating the TC database utilizes the positional information of TCs from the University of Hawaii (see information online at http://www.solar.ifa.hawaii.edu/Tropical/). Note that these track data are not used in this study. Instead, we used the best-track data described in the following subsection.

In this study, TRMM TC data for the period from December 1997 to December 2003 were utilized, which consist of 563 TCs (including tropical depressions) or 3703 snapshots. In addition, full-orbit PR2A25, version 5, data from January 1998 to July 2001 were utilized for the analysis of mean characteristics of rain from 35°N to 35°S. As for the flash numbers, TRMM LIS data from January 1998 to December 2003 were used.

b. The best-track data

In this study, the positions and times of TC centers and maximum sustained velocities every 6 h are obtained from the best-track data prepared by the Joint Typhoon Warning Center (JTWC), the National Hurricane Center (NHC), and the Central Pacific Hurricane Center (CPHC). The data from JTWC are used for the northwestern Pacific, the North Indian Ocean, the South Indian Ocean, and the South Pacific, and the data from NHC are used for the northeastern Pacific and the North Atlantic. The data from CPHC are utilized for the north-central Pacific. The maximum 1-min mean sustained wind speeds are provided by all agencies. The analysis period is from December 1997 to December 2003.

3. Methodology

We classify TCs into four classes, depending on the largest maximum sustained velocity attained during each TC life cycle (hereinafter υpk): class 1 (υpk < 34 kt), class 2 (34 kt ≤ υpk < 64 kt), class 3 (64 kt ≤ υpk < 128 kt), and class 4 (υpk ≥ 128 kt). The threshold of 34 kt is the division between tropical depression and tropical storm, and that of 64 kt transitions to hurricanes and typhoons. Only class 2–4 data are used for most analyses, because the sampled number of class-1 TCs is small.

We next determine three life stages for each TC as developing, mature, and decaying. The mature stage is defined as the period when the instantaneous maximum sustained velocity exceeds the threshold of 80% of υpk for each TC. The periods before and after the mature stage are called developing and decaying stages, respectively. In the case that a TC develops again after the first decaying stage, we treat the first stage and the second stage of the TC as two separate TCs.

Note that we divide TCs into classes according to the largest maximum sustained velocity in their life cycle, which is different from usual TC classifications. For example, a weak TC may belong to a strong class, if it develops into the strong TC later on. We utilize this unusual approach in order to understand the characteristics of each life cycle of potentially strong or weak TCs.

Figure 1 shows composites of the maximum sustained velocity from the best-track data, which are normalized with the mean length for each stage of each class. Tropical cyclones observed by the TRMM satellite at least once from December 1997 to December 2003 are utilized. After classifying TCs into classes, we make composites into the mean length of each stage. Table 1 shows mean life cycles and the numbers of TC occurrences for each class. The snapshot numbers of the TRMM TC database are also indicated. There is no difference between the numbers for PR and TMI. It is found that the developing stage and the decaying stage are longer for stronger TCs.

Rain characteristics of TCs are analyzed with two steps. The first step compares rain characteristics of TCs with those of the equatorial region mean. Figure 2 shows the latitudinal number distribution of the TC center positions obtained from the best-track data every 6 h, and that of TRMM TC observations. Few TCs are found between 10°N and 10°S. It is reported that half of the total area of moderately cold (<235 K) cloud consists of cloud clusters larger than 105 km2 in the tropical region (Mapes and Houze 1993). Because rain strongly correlates with cloud area (Houze 1993), it can be assumed that most of the tropical rain is associated with cloud clusters and squall lines, especially over the ocean.

The second step is to quantify radial variations of rain characteristics for each class and each stage. We divide the TC area into 10-km bins from the center within a 500-km radius, and then obtain azimuthal averages of various values in each bin.

Rain rate, SRR, and RTH derived from PR, and lightning flash rate and RPF derived from LIS and PR are utilized to represent rain characteristics in this study. RTH is defined as the highest altitude with a threshold of 0.3 mm h−1 in the rain-detected pixel. RPF is the ratio of the rain rate to the lightning flash rate in the region.

4. Rain characteristics of TCs

a. Comparing rain characteristics of TCs with those of the equatorial mean

Histograms of rain rates represent basic rain characteristics. Lonfat et al. (2004) used TMI data to show probability density functions of rain rates within a 500-km radius of the storm center. In their study, rain rates most frequently appeared around 1 mm h−1, and TCs in stronger categories had peaks at stronger rates. Utilizing the advantage of TRMM PR data, we examine rain rates of stratiform and convective rain separately, and compare the characteristics of TCs with those of the equatorial mean. Note that a comparison with the characteristics of the 25°N–25°S mean, which is the general rainfall in the regions where TCs normally occurs, is also important. Because the plots for the 25°N–25°S mean are very similar to those of the equatorial mean (not shown), we only show the 10°N–10°S mean in the following discussion.

Figure 3a shows histograms of pixel numbers binned into rain rates for class 2–4 TCs over ocean and for the equatorial oceanic mean. The percentage of stratiform pixels and convective pixels in the total rain-detected pixels are separately plotted according to rain rates. Rain rates are shown in dBR scale or 10 × log10(rain rate). With TCs, the peak rate of stratiform rain is about 0 dBR (1 mm h−1), which is consistent with Lonfat et al. (2004). Both TCs and the equatorial oceanic mean consist of large numbers of stratiform rain pixels, which reflects the characteristics of organized rain systems. The ratio of the total stratiform pixel numbers to the total convective pixel numbers are about 5 for TCs, while the ratio is about 3 for the equatorial oceanic mean. The peak rate of stratiform rain for the equatorial mean is found at −2 dBR (0.63 mm h−1). The stratiform rain rates are generally larger in TCs compared to the equatorial oceanic mean. For convective rain, TCs have nearly the same peak rate as the equatorial oceanic mean. However, the second peak of weak convective rain around 0 dBR (1 mm h−1) found in the equatorial oceanic mean is not observed in TCs. It is speculated that this peak corresponds to the rain that is reclassified from shallow and isolated stratiform rain to convective rain, following Schumacher and Houze (2003).

Next, we examine histograms of rain amounts binned into rain rates over the ocean (Fig. 3b). The percentages of stratiform rain amount and convective rain amount in the total rainfall over the ocean are separately plotted according to rain rates. It is notable that stratiform rain makes a larger contribution than convective rain in TCs, contrasting to the equatorial oceanic mean. The largest contribution to the total stratiform rain in TCs is from 6 to 7 dBR (4.0–5.0 mm h−1) bins, while that in the equatorial oceanic mean is from 4 to 5 dBR (2.5–3.2 mm h−1) bins. In other words, TCs have a larger contribution from stronger stratiform rain compared to the equatorial oceanic mean. At the same time, vigorous convective rain above 20 dBR (100 mm h−1) also makes a relatively large contribution in TCs over ocean, which is scarce in the equatorial oceanic mean.

Several case studies (Marks 1985; Marks and Houze 1987) indicated that stratiform rain accounted for 60%–62% of the total rainfall within a 111-km radius of the TC center. On the other hand, the mean SRR of typical squall lines was reported as being about 30%–50% (Houze 1977; Leary and Houze 1979), which is smaller than the mean SRR of TCs. Takayabu (2002) emphasized the usefulness of utilizing SRR derived from PR data in order to characterize the rainfall. Takayabu (2002) found that the SRR at 2–4-km altitude over the equatorial ocean between 10°N and 10°S was 48% in amount and the stratiform pixel ratio (SPR) was 76% for the same region. [These values are modified with the reclassification of shallow isolated rain from stratiform to convective after Schumacher and Houze (2003).] Here we compare these values at the near surface. As for TCs, the mean SRR is found as 52%, which is 8% larger than the value of 44% over the equatorial oceanic mean between 10°N and 10°S. As for the area, the mean SPR for the TCs is 80%, which is larger than the equatorial oceanic mean of 73%.

RTH observation from space became newly available with TRMM. Figure 4 shows contribution histograms of RTH to the total near-surface rainfall counted in 0.25-km bins both over ocean and over land. As already seen in Fig. 3b, stratiform rain makes a larger contribution than convective rain in TCs. Large contributions are found from the stratiform rain with about 7.5-km RTH and from the convective rain with about 8.5-km RTH in TCs both over ocean and over land. In other words, RTH of TCs is concentrated in the range of 7–9 km. In the equatorial mean, on the other hand, each peak is not sharp compared to TCs, and a large land–sea contrast of tall convective rain is also found. There are large contributions of rain with a broad range of RTH in the equatorial mean, such as shallow rain over ocean and tall rain above ∼12 km over land. In addition, the histograms for the 25°N–25°S mean are similar to those for the equatorial mean.

The spectral representation of rain profiles is also useful for quantifying rain structures in three dimensions (e.g., Houze and Leary 1976; Leary and Houze 1980). Takayabu (2002) accumulated rain profiles at the nadir observed by PR in the equatorial region from January 1998 to December 2000, which were divided into four patterns according to rain type (either convective or stratiform) and surface condition (either ocean or land), and then sorted rain profiles with RTH. Colors represent conditional mean rain-rate profiles for each fixed RTH value. The ordinate axis indicates altitudes, and the abscissa indicates cumulative frequencies. Utilizing this diagram, we can know what shape the average rain profiles has for a given RTH, and where it is in the order of RTH. Figure 5 is basically the same as that in Takayabu (2002), but with the reclassification of shallow isolated rain from the stratiform type to the convective type after Schumacher and Houze (2003). Note that Figs. 5a,c are the same figures as Fig. 2 in Shige et al. (2004). Figure 6 is illustrated for TCs over the ocean following Takayabu (2002), although we utilize seven pixels around the nadir to increase the number of samples.

The most notable difference is that TCs have much stronger convective and stratiform rain than the equatorial oceanic mean for the same RTH. In the profiles of convective rain with ∼9-km RTH, for example, TCs have 17–19 mm h−1 at 2–4 km, while the equatorial oceanic mean has 11–13 mm h−1. In the stratiform profiles with ∼8-km RTH, TCs have rain above 3.6 mm h−1 at 2–4 km, which is stronger than that of the equatorial oceanic mean.

In the equatorial diagram over land (Fig. 5b), there is a larger amount of vigorous convective rain compared with the ocean (Fig. 5a). On the other hand, the diagrams for TCs are very similar over land and over ocean. These results indicate that vigorous convective rain of TCs over land is different from that of the equatorial continental rain systems such as thunderstorms, and has more similarity to that of TCs over ocean.

b. Analyzing radial distributions of rain characteristics of TCs

Radial distributions of mean rain rates of TCs have been studied in many previous works (e.g., Rodgers and Adler 1981; Marks 1985; Lonfat et al. 2004). Figures 7a,b depict radial distributions of mean rain rates at the mature stage derived by TMI and PR, respectively. Note that the TMI plot includes TMI pixels that are outside the PR swath. All distributions are qualitatively similar to each other. They show several typical characteristics of TCs. For example, the existence of the eye is indicated in the TC center where the local minimum value of mean rain rate exists. The peaks of rain rates in the eyewall are also found within ∼50 km of the center in both distributions. However, TMI-derived mean rain rates are larger than PR-derived rates over all, and the peak rate is found ∼10 km farther from the TC center with TMI compared to that with PR. Especially in the 110–240-km region of class 4-TCs, TMI-derived rates are larger than 2 times the PR-derived rates. Even for weaker class TCs, the ratios of TMI-derived rates to PR-derived rates in the same region are always over 1.5. This result is consistent with the suggestion of Lonfat et al. (2004) that TMI-derived rates may be larger than rates derived from the previous radar studies in the outer region. We speculate that a possible reason for this problem is because version 5 TMI rain is more sensitive to the ice-scattering particles in the deep stratiform region. We also recalculated these distributions with the version 6 data (not shown). PR rain was significantly larger than TMI rain with this revision.

Next, Fig. 8 shows radial distributions of SRR, which is the percentage of the stratiform rain against the total rainfall in each radial bin. Clearly, TCs consist of two parts—the central part with smaller SRR and the outer part with larger SRR. In this study, we define three regions in terms of the average SRR at the mature stage. The region inside of ∼60 km is defined as the “inner core,” where the average SRR is smaller than the equatorial oceanic mean value of 44%. On the other hand, the region outside of ∼60-km radius is defined as the “rainband,” where SRR is larger than 44%. Particularly for class 4 and class 3, TCs have especially large SRRs (over 60%) in the regions of the 80–230-km radius and 90–140-km radius, respectively. These regions will be called inner rainband. Actually, these definitions give a 20–30-km gap between the “inner core” and the “inner rainbands.” This “average transition zone” would be a mix of eyewalls in some cases and rainbands in others, because the eyewall radius varies dramatically from case to case.

SRR also changes with stages. SRR in the rainband is slightly small at the developing stage, compared with other stages. At the mature stage, very large SRR in the inner rainband and very small SRR in the inner core are observed especially for class-4 TCs. Interestingly, stronger class TCs have larger SRR (exceeding 70%) in the inner rainband at the mature stage. At the decaying stage, the SRR contrast between the inner and the outer rainbands becomes smaller.

Radial distributions of the contribution to the total near-surface rainfall at the mature stage binned with the RTH are shown in Fig. 9. The contribution is counted in each 10-km radial range. A large contrast between the inner core and the rainband is found in all classes. In the inner core, convective rain with 8–12-km RTH makes a large contribution. On the other hand, stratiform rain with 6–9-km RTH makes a large contribution in the rainband. It is interesting to find a transition zone in the region between 50 and 100 km, where there is a substantial shift from the inner-core convection to the rainband stratiform rainfall. The contrast between the inner core and the rainband is found to be larger in stronger classes that have more stratiform rain in the inner rainband. Interestingly, in the outer rainband in stronger classes, tall convective rain (e.g., RTH > 12 km) makes a smaller contribution, but instead modest convective rain with 7–9-km RTH makes a larger contribution. This feature is especially well defined in class-4 TCs. As a result, stronger classes have more rain with 7–9-km RTH both for stratiform and convective rain in the rainband. The result is consistent with the concentrated contribution of RTH shown in Fig. 4a.

At last, the relationship between rain and lightning is investigated. Lightning activity is closely related to cloud microphysics. Takahashi (1978, 1984) showed that a coexistence of small ice particles, large graupel, and supercooled water is necessary for the electrification of clouds. Strong updraft is essential to the existence of graupel and supercooled water above, which means that the number of flashes should accompany tall convective rain with a large RTH. We show radial distributions of flash rate and RPF of TCs in Fig. 10. The former value is obtained by dividing the number of observed flashes by the observed time of LIS. The latter RPF is the ratio of mean rain rate to flash rate in each radial bin. Here, these analyses are not separated into life stages, because there are not enough samples.

Figure 10a shows radial distributions of flash rates. Large flash rate is observed in the inner core, but it is small in the rainband. In previous studies, Molinari et al. (1999) showed that flash density was larger in the 200–300-km radius region than the 0–60-km radius region. As discussed by Cecil et al. (2002), the difference from Molinari et al. (1999) may also result from an increased ratio of in-cloud and cloud-to-ground flashes in the eyewall, and difference of the sample size. Interestingly, stronger classes have larger flash rates in the inner core, but smaller flash rates in the rainband, especially in the inner rainband.

Figure 10b shows radial distributions of RPF. RPF is a rain amount normalized with the lightning flash numbers, which indicates characteristics of rain instead of its amount (e.g., Williams et al. 1992; Petersen and Rutledge 1998). Takayabu (2006) calculated global tropical RPF with TRMM PR and LIS data and confirmed that RPF well represents the rain characteristics such as the “oceanic regime” and the “continental regime” of rain, and found the existence of transition zones with intermediate RPF values. In TCs, significantly larger RPF is found in the inner rainband than other regions. The mean RPF (gray line) ranges from 0.1 × 1010 to 0.6 × 1010 kilograms per flash. The value is comparable to the oceanic mean RPF value of 0.2 × 1010 kilograms per flash (Takayabu 2006) in the region between 36°N and 36°S. Although the value of Takayabu (2006) is based on TRMM PR version 6 data, we confirm that RPF of TCs for version 6 is larger than that for version 5 (not shown), so that the RPF of TCs should be even more distinctively larger than the oceanic mean value for version 5. For reference, Kempf and Krider (2003) used the ground-based observational data during June–August 1993 to show that seasonal mean RPF over the Upper Mississippi River basin was 1.3 × 105 meters cubed per flash, which is about 1.3 × 108 kilograms per flash.

It is notable that stronger-class TCs have very large RPF, which reaches 3.2 × 1010 kilograms per flash in the inner rainband. Large RPF reflects the fact that TC inner rainband regions are dominated by stratiform rain, as we have already seen with SRR.

5. Contribution of TCs to the total rainfall

It is important to quantify the fraction of TC rainfall in the global rainfall. Such quantification is useful, for example, in validating GCM performances in terms of TC rainfall. At last in this section, the contribution of TCs with 500-km radius is estimated against the total annual rainfall over the entire TRMM region between 35°N and 35°S. To calculate the TC rain contribution, PR-derived radial distributions of mean rain rates (e.g., Fig. 5b) and the best-track data are used from January 1998 to December 2000.

TC rainfall is estimated with the following formula:
i1520-0493-136-10-3848-eq1
where r is the radial bin number from the center to 500 km; RRr,stage,class is the mean rain rate in each 10-km radial bin, stage, and class; Sr is the area of each radial bin; Tstage,class is the mean lifetime in each class and stage; and Nclass is the number of occurrence of TCs in each class. Both Tstage,class and Nclass are obtained from the best-track data (Table 2).

Consequently, annual mean rainfall of 2.6 × 1023 mm3 yr−1 and TC rainfall of (8.6 ± 0.4) × 1021 mm3 yr−1 are obtained in the region between 35°N and 35°S. This statistics are reliable at the 90% confidence level. This confidence interval considers the problem for sampling PR pixels, but not for sampling individual TCs. Thus, the contribution of TC rainfall in the 35°N–35°S region is estimated as 3.3 ± 0.1%. The breakdown is as follows: class-4 TCs account for 0.64% ± 0.04%, class-3 TCs for 1.7% ± 0.06%, and class-2 TCs for 0.96% ± 0.05%. Previous works (Rodgers et al. 2000, 2001) used microwave data derived by SSM/I and estimated that the contribution of TC rainfall was 7% in the North Pacific and 4% in the North Atlantic. The primary reason of their larger value is considered as that their analysis is based only on the TC active seasons (June–November) and regions. In addition, there may be a difference resulting from the different estimates from radar and microwave measurements. Because the issue of the discrepancy between PR- and TMI-derived rain rates is beyond the scope of this study, it is left for future studies.

6. Summary and discussion

In this study, we statistically analyzed three-dimensional rain characteristics of TCs, using TRMM PR, TMI, and LIS data. Tropical cyclones were classified into four classes and three stages, depending on the largest maximum sustained velocity attained during each life cycle.

First, rain characteristics of TCs were compared with those of the equatorial mean. Stratiform rain made a larger contribution than convective rain for TCs, but not for the equatorial mean. The mean SRR was 52%, which was 8% larger than the equatorial oceanic mean value of 44%. The largest contribution in TCs came from the stratiform rain with the intensity of 6–7 dBR (4.0–5.0 mm h−1), which was stronger than the equatorial oceanic mean. At the same time, vigorous convective rain above 20 dBR (100 mm h−1) also made a relatively large contribution to the total rainfall of TCs. RTH of TCs contributing most to the total near-surface rainfall is found at ∼7.5 km for the stratiform rain and at ∼8.5 km for the convective rain. RTH of TCs was more concentrated in the range of 7–9 km than the equatorial area mean.

Next, we analyzed radial variations of rain characteristics of TCs. We defined the region inside of the ∼60-km radius as the inner core, where SRR was smaller than the equatorial oceanic mean value of 44%. The region outside of the 60-km radius was defined as the rainband, where SRR was larger than 44%. Especially for class 4 and class 3, TCs had very large SRR over 60% in the bins of 80–230- and 90–140-km radius, respectively. These regions were defined as the inner rainband.

In the inner core, mean rain-rate distributions showed the existence of the eye and the eyewall, although it is smoothed out compared to the case studies. SRR was small and flash rates were large, which was consistent with a large contribution of tall convective rain with 8–12-km RTH. Stronger classes had more significant characteristics of the inner core. In the rainband, SRR was larger than the equatorial oceanic mean value of 44%, and RPF was as large as 0.1–0.6 (×1010) killograms per flash on average. Consistently, large contributions were observed from the stratiform rain with 6–9-km RTH and modest convective rain with 7–9-km RTH there. Interestingly, stronger classes had larger contributions from the modest convective rain.

Especially in the inner rainband, both SRR and RPF were very large, and flash rates were small, compared with the outer rainband. Stratiform rain with 7–9-km RTH made the largest contribution to the total near-surface rainfall in the inner rainband. Stronger classes had larger SRR up to 70% at the mature stage in class 4, and larger RPF that attained 3.2 × 1010 kilograms per flash in class 4. They also had more stratiform rain with 7–9-km RTH. In addition, stronger classes had smaller flash rates in the inner rainband. These characteristics consistently indicated that stratiform rain was more dominant in the inner rainband than other regions of TCs. It was also indicated that stronger classes had more stratiform rain, especially at the mature stage. Interestingly, the contrast of characteristics between the inner core and the inner rainband was larger in stronger classes.

Above results show that TCs have the characteristics of better-organized rain systems than the equatorial mean. The mean is bulk statistics, so that we need to confirm that TCs are really better organized than other organized rain systems. Lin et al. (2004) indicated that SRR increased in the mature phase of Madden–Julian oscillation (MJO), utilizing data from the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). So, we compared SRR of TCs with that of the mature phase of MJO analyzed by Morita et al. (2006) utilizing TRMM PR data. From their results, it is estimated that SRR is about 46% in the mature of MJO, which is still smaller than that of TCs (52%).

Last, the contribution of the TCs to the total rainfall was estimated between 35°N and 35°S, using both the radial distribution of mean rain rates derived by PR and the best-track data. As a result, TC rainfall accounted for about 3.3% ± 0.1% of the total annual rainfall. We can utilize such statistical quantity to validate the GCM in terms of the performance of TC rainfall.

Consequently, TC rain is basically similar to the equatorial oceanic mean rain, which mostly consists of organized systems such as cloud clusters, in the manner that the active convection sustains very large stratiform rain area. However, TCs have stronger convective rain in the inner core as well as stronger stratiform rain in the rainband than cloud clusters. At the same time, stratiform rain makes a larger contribution to the total rainfall than convective rain in TCs, contrasting to the equatorial mean. Much stratiform rain can be maintained without the tallest convective rain in the rainband of TCs. On the other hand, the most vigorous convective rain makes a large contribution in the inner core. Consequently, a huge area of stratiform rain is maintained with the most vigorous eyewall rain. This result suggests that a TC as a whole has a huge mesoscale structure that is favorable for maintaining a large amount of stratiform rain with the same amount of convection. Among them, stronger-class TCs have the most significant TC characteristics.

An important implication of this study is that rain characteristics of TCs are listed in the high end of tropical oceanic organized rain systems, such as cloud clusters, in terms of the organization levels, and the stronger TCs are their extremes.

Acknowledgments

The JAXA/EORC Tropical Cyclone Database (version 1.2) was provided by the Earth Observation Research and Application Center, Japan Aerospace Exploration Agency. The authors are indebted to Dr. T. Iguchi and Dr. N. Takahashi for discussions on PR2A25 data and to Prof. T. Ushio at the University of Osaka for his help in obtaining TRMM LIS data. We also express our hearty gratitude to Prof. J. L. Chan at the City University of Hong Kong for reading the manuscript and providing helpful comments and suggestions. Thanks are extended to Dr. D. J. Cecil and an anonymous reviewer for their valuable review comments. This work is supported by the TRMM JRA5 of Japan Aerospace Exploration Agency (JAXA) and the Global Environment Research Fund (S-5-2) of the Ministry of the Environment, Japan.

REFERENCES

  • Awaka, J., , T. Iguchi, , and K. Okamoto, 1998: Early results on rain type classification by the Tropical Rainfall Measuring Mission (TRMM) precipitation radar. Proc., Eighth URSI Commission F Open Symp., Aveiro, Portugal, URSI, 143–146.

  • Cecil, D. J., , and E. J. Zipser, 2002: Reflectivity, ice scattering, and lightning characteristics of hurricane eyewalls and rainbands. Part II: Intercomparison of observations. Mon. Wea. Rev., 130 , 785801.

    • Search Google Scholar
    • Export Citation
  • Cecil, D. J., , E. J. Zipser, , and S. W. Nesbitt, 2002: Reflectivity, ice scattering, and lightning characteristics of hurricane eyewalls and rainbands. Part I: Quantitative description. Mon. Wea. Rev., 130 , 769784.

    • Search Google Scholar
    • Export Citation
  • Christian, H. J., and Coauthors, 1999: The Lightning Imaging Sensor. Proc. 11th Int. Conf. on Atmospheric Electricity, Guntersville, AL, International Commission on Atmospheric Electricity, 746–749.

  • Dodge, P., , R. W. Burpee, , and F. D. Marks Jr., 1999: The kinematic structure of hurricane with sea level pressure less than 900 mb. Mon. Wea. Rev., 127 , 9871004.

    • Search Google Scholar
    • Export Citation
  • Emanuel, K. A., 2005: Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436 , 686688.

  • Hasegawa, A., , and S. Emori, 2005: Tropical cyclones and associated precipitation over the western North Pacific in present and doubled CO2 climates simulated by a T106 atmospheric GCM. SOLA, 1 , 145148.

    • Search Google Scholar
    • Export Citation
  • Hood, R. E., and Coauthors, 2006: Classification of tropical oceanic precipitation using high-altitude aircraft microwave and electric field measurements. J. Atmos. Sci., 63 , 218233.

    • Search Google Scholar
    • Export Citation
  • Houze Jr., R. A., 1977: Structure and dynamics of a tropical squall-line system. Mon. Wea. Rev., 105 , 15401567.

  • Houze Jr., R. A., 1982: Cloud clusters and large-scale vertical motions in the tropics. J. Meteor. Soc. Japan, 60 , 396410.

  • Houze Jr., R. A., 1989: Observed structure of mesoscale convective systems and implications for large-scale heating. Quart. J. Roy. Meteor. Soc., 115 , 425461.

    • Search Google Scholar
    • Export Citation
  • Houze Jr, R. A., 1993: Cloud Dynamics. Academic Press, 337 pp.

  • Houze Jr., R. A., 2004: Mesoscale convective systems. Rev. Geophys., 42 .RG4003, doi:10.1029/2004RG000150.

  • Houze Jr., R. A., , and C. A. Leary, 1976: Comparison of convective mass and heat transports in tropical easterly waves computed by two methods. J. Atmos. Sci., 33 , 424429.

    • Search Google Scholar
    • Export Citation
  • Iguchi, T., , T. Kozu, , R. Meneghini, , J. Awaka, , and K. Okamoto, 2000: Rain-profiling algorithm for the TRMM precipitation radar. J. Appl. Meteor., 39 , 20382052.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., 1984a: Mesoscale and convective-scale characteristics of mature hurricanes. Part I: General observations by research aircraft. J. Atmos. Sci., 41 , 12681286.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., 1984b: Mesoscale and convective-scale characteristics of mature hurricanes. Part II: Inner core structure of Hurricane Allen (1980). J. Atmos. Sci., 41 , 12871311.

    • Search Google Scholar
    • Export Citation
  • Jorgensen, D. P., , and M. A. LeMone, 1989: Vertical velocity characteristics of oceanic convection. J. Atmos. Sci., 46 , 621640.

  • Jorgensen, D. P., , E. J. Zipser, , and M. A. LeMone, 1985: Vertical motions in intense hurricanes. J. Atmos. Sci., 42 , 839856.

  • Kempf, N. M., , and E. P. Krider, 2003: Cloud-to-ground lightning and surface rainfall during the great flood of 1993. Mon. Wea. Rev., 131 , 11401149.

    • Search Google Scholar
    • Export Citation
  • Knutson, T. R., , and R. E. Tuleya, 2004: Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. J. Climate, 17 , 34773495.

    • Search Google Scholar
    • Export Citation
  • Kummerow, C., , W. Barnes, , T. Kozu, , J. Shiue, , and J. Simpson, 1998: The Tropical Rainfall Measuring Mission (TRMM) sensor package. J. Atmos. Oceanic Technol., 15 , 809817.

    • Search Google Scholar
    • Export Citation
  • Kummerow, C., and Coauthors, 2000: The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. J. Appl. Meteor., 39 , 19651982.

    • Search Google Scholar
    • Export Citation
  • Leary, C. A., , and R. A. Houze Jr., 1979: Melting and evaporation of hydrometeors in precipitation from the anvil clouds of deep tropical convection. J. Atmos. Sci., 36 , 669679.

    • Search Google Scholar
    • Export Citation
  • Leary, C. A., , and R. A. Houze Jr., 1980: The contribution of mesoscale motion to the mass and heat fluxes of an intense tropical convective system. J. Atmos. Sci., 37 , 784796.

    • Search Google Scholar
    • Export Citation
  • LeMone, M. A., , and E. J. Zipser, 1980: Cumulonimbus vertical velocity events in GATE. Part I: Diameter, intensity and mass flux. J. Atmos. Sci., 37 , 24442457.

    • Search Google Scholar
    • Export Citation
  • Lin, J., , B. Mapes, , M. Zhang, , and M. Newman, 2004: Stratiform precipitation, vertical heating profiles, and the Madden–Julian oscillation. J. Atmos. Sci., 61 , 296309.

    • Search Google Scholar
    • Export Citation
  • Lonfat, M., , F. D. Marks Jr., , and S. S. Chen, 2004: Precipitation distribution in tropical cyclones using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager: A global perspective. Mon. Wea. Rev., 132 , 16451660.

    • Search Google Scholar
    • Export Citation
  • Lucas, C., , E. J. Zipser, , and M. A. LeMone, 1994: Vertical velocity in oceanic convective off tropical Australia. J. Atmos. Sci., 51 , 31833193.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., , and R. A. Houze Jr., 1993: Cloud clusters and superclusters over the oceanic warm pool. Mon. Wea. Rev., 121 , 13981415.

  • Marks Jr., F. D., 1985: Evolution of the structure of precipitation in Hurricane Allen (1980). Mon. Wea. Rev., 113 , 909930.

  • Marks Jr, F. D., 2003: State of the science: Radar view of tropical cyclones. Cloud Systems, Hurricanes, and the Tropical Rainfall Measuring Mission (TRMM): A Tribute to Dr. Joanne Simpson, Meteor. Monogr., No. 51, Amer. Meteor. Soc., 33–74.

    • Search Google Scholar
    • Export Citation
  • Marks Jr., F. D., , and R. A. Houze Jr., 1987: Inner core structure of Hurricane Alicia from airborne Doppler radar observations. J. Atmos. Sci., 44 , 12961317.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., , P. Moore, , and V. Idone, 1999: Convective structure of hurricanes as revealed by lightning locations. Mon. Wea. Rev., 127 , 520534.

    • Search Google Scholar
    • Export Citation
  • Morita, J., , Y. N. Takayabu, , S. Shige, , and Y. Kodama, 2006: Analysis of rainfall characteristics of the Madden–Julian oscillation using TRMM satellite data. Dyn. Atmos. Oceans, 42 , 107126.

    • Search Google Scholar
    • Export Citation
  • Oouchi, K., , J. Yoshimura, , H. Yoshimura, , R. Mizuta, , S. Kusunoki, , and A. Noda, 2006: Tropical cyclone climatology in a global-warming climate as simulated in a 20 km-mesh global atmospheric model: Frequency and wind intensity analyses. J. Meteor. Soc. Japan, 84 , 259276.

    • Search Google Scholar
    • Export Citation
  • Petersen, W. A., , and S. A. Rutledge, 1998: On the relationship between cloud-to-ground lightning and convective rainfall. J. Geophys. Res., 103 , 1402514040.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , and R. F. Adler, 1981: Tropical cyclone rainfall characteristics as determined from a satellite passive microwave radiometer. Mon. Wea. Rev., 109 , 506521.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , R. F. Adler, , and H. F. Pierce, 2000: Contribution of tropical cyclones to the North Pacific climatological rainfall as observed from satellites. J. Appl. Meteor., 39 , 16581678.

    • Search Google Scholar
    • Export Citation
  • Rodgers, E. B., , R. F. Adler, , and H. F. Pierce, 2001: Contribution of tropical cyclones to the North Atlantic climatological rainfall as observed from satellites. J. Appl. Meteor., 40 , 17851800.

    • Search Google Scholar
    • Export Citation
  • Schumacher, C., , and R. A. Houze Jr., 2003: The TRMM precipitation radar’s view of shallow, isolated rain. J. Appl. Meteor., 42 , 15191524.

    • Search Google Scholar
    • Export Citation
  • Shige, S., , Y. N. Takayabu, , W-K. Tao, , and D. E. Johnson, 2004: Spectral retrieval of latent heating profiles from TRMM PR data. Part I: Development of a model-based algorithm. J. Appl. Meteor., 43 , 10951113.

    • Search Google Scholar
    • Export Citation
  • Sugi, M., , A. Noda, , and N. Sato, 2002: Influence of the global warming on tropical cyclone climatology: An experiment with the JMA global model. J. Meteor. Soc. Japan, 80 , 249272.

    • Search Google Scholar
    • Export Citation
  • Szoke, E. J., , E. J. Zipser, , and D. P. Jorgensen, 1986: A radar study of convective cells in mesoscale systems in GATE. Part I: Vertical profile statistics and comparison with hurricanes. J. Atmos. Sci., 43 , 182197.

    • Search Google Scholar
    • Export Citation
  • Takahashi, T., 1978: Riming electrification as a charge mechanism in thunderstorms. J. Atmos. Sci., 35 , 15361548.

  • Takahashi, T., 1984: Thunderstorm electrification—A numerical study. J. Atmos. Sci., 41 , 25412558.

  • Takayabu, Y. N., 2002: Spectral representation of rain profiles and diurnal variations observed with TRMM PR over the equatorial area. Geophys. Res. Lett., 29 .1584, doi:10.1029/2001GL014113.

    • Search Google Scholar
    • Export Citation
  • Takayabu, Y. N., 2006: Rain-yield per flash calculated from TRMM PR and LIS data and its relationship to the contribution of tall convective rain. Geophys. Res. Lett., 33 .L18705, doi:10.1029/2006GL027531.

    • Search Google Scholar
    • Export Citation
  • Wang, K-Y., , and S-A. Liao, 2006: Lightning, radar reflectivity, infrared brightness temperature, and surface rainfall during the 2–4 July 2004 severe convective system over Taiwan area. J. Geophys. Res., 111 .D05206, doi:10.1029/2005JD006411.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., , G. J. Holland, , J. A. Curry, , and H-R. Chang, 2005: Changes in tropical cyclone number, duration, and intensity in a warming environment. Science, 309 , 18441846.

    • Search Google Scholar
    • Export Citation
  • Williams, E. R., , S. A. Rutledge, , S. C. Geotis, , N. Renno, , E. Rasmussen, , and T. Rickenbach, 1992: A radar and electrical study of tropical hot towers. J. Atmos. Sci., 49 , 13861395.

    • Search Google Scholar
    • Export Citation
  • Yuter, S. E., , and R. A. Houze Jr., 1998: The natural variability of precipitating clouds over the western Pacific warm pool. Quart. J. Roy. Meteor. Soc., 124 , 5399.

    • Search Google Scholar
    • Export Citation
  • Zipser, E. J., 1977: Mesoscale and convective-scale downdrafts as distinct components of squall-line structure. Mon. Wea. Rev., 105 , 15681589.

    • Search Google Scholar
    • Export Citation
  • Zipser, E. J., , and M. A. LeMone, 1980: Cumulonimbus vertical velocity events in GATE. Part II: Synthesis and model core structure. J. Atmos. Sci., 37 , 24582469.

    • Search Google Scholar
    • Export Citation

APPENDIX

Contribution Histograms of TC Rain Rate for Version 6

Histograms of rain amounts binned into rain rates of TCs over ocean are recalculated with the PR version 6 data (Fig. A1). Figure A1 is corresponding to Fig. 3b (thick lines) with version 5 data. The percentages of stratiform rain amount and convective rain amount in the total rainfall over ocean are separately plotted according to rain rates. For version 6 data, stratiform rain over ∼10 dBR (10 mm h−1) increases, so that the histograms of convective and stratiform are overlapped to each other.

Fig. 1.
Fig. 1.

Time series of the best-track data every 6 h. The composites of individual best-track data, which are normalized with the mean length for each stage of each class, are shown in class (a) 1, (b) 2, (c) 3, and (d) 4. All time series are denoted by gray lines and mean time series by black line. Vertical lines indicate the section of each stage. Tropical cyclones observed by TRMM satellite once at least from December 1997 to December 2003 are analyzed.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 2.
Fig. 2.

The numbers of center positions obtained from the best-track data every 6 h, and the numbers of TRMM TC observations, according to latitudinal regions from 35°S to 35°N. Analysis duration is from January 1998 to December 2003.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 3.
Fig. 3.

Histograms of (a) pixel numbers and (b) rain amounts binned into rain rates over ocean. Rain rates are shown in dBR scale of 10 × log10(rain rate). The rightmost bin includes rain rates over 24 dBR. Thick lines and thin lines denote distributions of TCs and the equatorial mean, respectively. Solid lines and dashed lines denote stratiform rain and convective rain, respectively.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 4.
Fig. 4.

Contribution to the total near-surface rainfall from RTH over (a) ocean and (b) land. Lines are depicted as in Fig. 3.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 5.
Fig. 5.

Spectral representations of rain profiles in the equatorial mean for (a) oceanic convective, (b) continental convective, (c) oceanic stratiform, and (d) continental stratiform, which are basically the same as in Takayabu (2002), but with the reclassification of shallow isolated rain from stratiform to convective after Schumacher and Houze (2003). Rain profiles at the nadir pixels observed by PR are accumulated in the equatorial region from January 1998 to December 2000, and then sorted with RTH. Colors represent conditional mean rain-rate profiles for each fixed RTH value. Ordinate axis indicates altitudes, and abscissa indicates cumulative frequencies. (a) and (c) The same as Fig. 2 of Shige et al. (2004).

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 6.
Fig. 6.

The same as Fig. 5, but for TCs. Seven pixels around the nadir are utilized.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 7.
Fig. 7.

Radial distributions of mean rain rates derived by (a) PR and (b) TMI at the mature stage. Mean rain rate is obtained from unconditionally averaging rain rate over each 10-km-wide annular region. Solid lines with error bars denote composites for classes 4 (c4), 3 (c3), and 2 (c2), respectively. A line without error bars is for the average over classes 2–4. Error bars show the 90% confidence intervals.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 8.
Fig. 8.

The radial distributions of SRR derived by PR at the (top) developing, (middle) mature, and (bottom) decaying. SRR is the percentage of total stratiform rain in the total rainfall over each annular region. Lines with open circles, filled circles, and open triangles denote distributions of class 4, 3, and 2, respectively. Gray lines are for the average over classes 2–4.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 9.
Fig. 9.

Radial distributions of the contribution to the total near-surface rainfall from RTH at the mature stage, for class (top) 2, (middle) 3, and (bottom) 4. Distributions of (left) convective rain and (right) stratiform rain. The contributions are denoted by shaded colors.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Fig. 10.
Fig. 10.

Radial distributions of (a) flash rates and (b) RPF. Flash rate is number of observed flashes divided by observed time, and RPF is ratio of mean rain rate to flash rate in each annular region. Lines are depicted as in Fig. 8.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

i1520-0493-136-10-3848-fa01

Fig. A1. Histograms of rain amounts binned into rain rates for TCs over ocean with version 6 data. Rain rates are shown in dBR scale of 10 × log10(rain rate). The rightmost bin includes rain rates over 24 dBR. Thick lines and thin lines denote distributions of TCs and the equatorial mean, respectively. Solid lines and dashed lines denote stratiform rain and convective rain, respectively. Analysis duration is from December 1997 to December 2003.

Citation: Monthly Weather Review 136, 10; 10.1175/2008MWR2408.1

Table 1.

Mean life cycles and the numbers of TC occurrences for each class are shown from the best-track data. The snapshot numbers of TRMM TC database are also indicated. Tropical cyclones observed by TRMM satellite once at least from December 1997 to December 2003 are analyzed. Note that TC with two mature stages is considered as two TCs. There is no difference between the numbers for PR and TMI.

Table 1.
Table 2.

The numbers of TC occurrences and mean lengths of each life stages of each class TCs are shown from the best-track data. All TCs from January 1998 to December 2000 are analyzed, whether TRMM satellite observed or not. Note that TC with 2 mature stages is considered as 2 TCs.

Table 2.
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