Editorial Type:
Article
Article Type:
Research Article

Radar Characteristics of Precipitation Features in the EPIC and TEPPS Regions of the East Pacific

R. Cifelli Colorado State University, Fort Collins, Colorado

Search for other papers by R. Cifelli in
Current site
Google Scholar
PubMed Close
,
S. W. Nesbitt Colorado State University, Fort Collins, Colorado

Search for other papers by S. W. Nesbitt in
Current site
Google Scholar
PubMed Close
,
S. A. Rutledge Colorado State University, Fort Collins, Colorado

Search for other papers by S. A. Rutledge in
Current site
Google Scholar
PubMed Close
,
W. A. Petersen University of Alabama in Huntsville, Huntsville, Alabama

Search for other papers by W. A. Petersen in
Current site
Google Scholar
PubMed Close
, and
S. Yuter North Carolina State University, Raleigh, North Carolina

Search for other papers by S. Yuter in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Apr 2007
DOI:
https://doi.org/10.1175/MWR3340.1
Page(s):
1576–1595
Restricted access

Abstract

Ship-based radar data are used to compare the structure of precipitation features in two regions of the east Pacific where recent field campaigns were conducted: the East Pacific Investigation of Climate Processes in the Coupled Ocean–Atmosphere System (EPIC-2001; 10°N, 95°W) in September 2001 and the Tropical Eastern Pacific Process Study (TEPPS; 8°N, 125°W) in August 1997. Corresponding July–September 1998–2004 Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) data are also used to provide context for the field campaign data. An objective technique is developed to identify precipitation features in the ship and TRMM PR data and to develop statistics on horizontal and vertical structure and precipitation characteristics. Precipitation features were segregated into mesoscale convective system (MCS) and sub-MCS categories, based on a contiguous area threshold of 1000 km2 (these features were required to have at least one convective pixel), as well as an “other” (NC) category. Comparison of the satellite and field campaign data showed that the two datasets were in good agreement for both regions with respect to MCS features. Specifically, both the satellite and ship radar data showed that approximately 80% of the rainfall volume in both regions was contributed by MCS features, similar to results from other observational datasets. EPIC and TEPPS MCSs had similar area distributions but EPIC MCSs tended to be more vertically developed and rain heavier than their TEPPS counterparts. In contrast to MCSs, smaller features (NCs and sub-MCSs) sampled by the ship radar in both regions showed important differences compared with the PR climatology. In the EPIC field campaign, a large number of small (<100 km2), shallow (radar echo tops below the melting level) NCs and sub-MCSs were sampled. A persistent dry layer above 800 mb during undisturbed periods in EPIC may have been responsible for the high occurrence of these features. Also, during the TEPPS campaign, sub-MCSs were larger and deeper with respect to the TRMM climatology, which may have been due to the higher than average SSTs during 1997–98 when TEPPS was conducted. Despite these differences, it was found that for sizes greater than about 100 km2, EPIC precipitation features had 30-dBZ echos at higher altitudes and also had higher rain rates than similar sized TEPPS features. These results suggest that ice processes play a more important role in rainfall production in EPIC compared with TEPPS.

Corresponding author address: Robert Cifelli, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371. Email: rob@atmos.colostate.edu

Abstract

Ship-based radar data are used to compare the structure of precipitation features in two regions of the east Pacific where recent field campaigns were conducted: the East Pacific Investigation of Climate Processes in the Coupled Ocean–Atmosphere System (EPIC-2001; 10°N, 95°W) in September 2001 and the Tropical Eastern Pacific Process Study (TEPPS; 8°N, 125°W) in August 1997. Corresponding July–September 1998–2004 Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) data are also used to provide context for the field campaign data. An objective technique is developed to identify precipitation features in the ship and TRMM PR data and to develop statistics on horizontal and vertical structure and precipitation characteristics. Precipitation features were segregated into mesoscale convective system (MCS) and sub-MCS categories, based on a contiguous area threshold of 1000 km2 (these features were required to have at least one convective pixel), as well as an “other” (NC) category. Comparison of the satellite and field campaign data showed that the two datasets were in good agreement for both regions with respect to MCS features. Specifically, both the satellite and ship radar data showed that approximately 80% of the rainfall volume in both regions was contributed by MCS features, similar to results from other observational datasets. EPIC and TEPPS MCSs had similar area distributions but EPIC MCSs tended to be more vertically developed and rain heavier than their TEPPS counterparts. In contrast to MCSs, smaller features (NCs and sub-MCSs) sampled by the ship radar in both regions showed important differences compared with the PR climatology. In the EPIC field campaign, a large number of small (<100 km2), shallow (radar echo tops below the melting level) NCs and sub-MCSs were sampled. A persistent dry layer above 800 mb during undisturbed periods in EPIC may have been responsible for the high occurrence of these features. Also, during the TEPPS campaign, sub-MCSs were larger and deeper with respect to the TRMM climatology, which may have been due to the higher than average SSTs during 1997–98 when TEPPS was conducted. Despite these differences, it was found that for sizes greater than about 100 km2, EPIC precipitation features had 30-dBZ echos at higher altitudes and also had higher rain rates than similar sized TEPPS features. These results suggest that ice processes play a more important role in rainfall production in EPIC compared with TEPPS.

Corresponding author address: Robert Cifelli, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371. Email: rob@atmos.colostate.edu

Save
Cover Monthly Weather Review
Monthly Weather Review

  • Berg, W., C. Kummerow, and C. A. Morales, 2002: Differences between east and west Pacific rainfall systems. J. Climate, 15 , 3659–3672.

    • Search Google Scholar
    • Export Citation

  • Cetrone, J., and R. A. Houze Jr., 2006: Characteristics of tropical convection over the ocean near Kwajalein. Mon. Wea. Rev., 134 , 834–853.

    • Search Google Scholar
    • Export Citation

  • Cheng, C-P., and R. A. Houze Jr., 1979: The distribution of convective and mesoscale precipitation in GATE radar echo patterns. Mon. Wea. Rev., 107 , 1370–1381.

    • Search Google Scholar
    • Export Citation

  • Cifelli, R., S. A. Rutledge, D. J. Boccippio, and T. Matejka, 1996: Horizontal divergence and vertical velocity retrievals from Doppler radar and wind profiler observations in tropical convection. J. Atmos. Oceanic Technol., 13 , 948–966.

    • Search Google Scholar
    • Export Citation

  • DeMott, C. A., and S. A. Rutledge, 1998: The vertical structure of TOGA COARE convection. Part I: Radar echo distributions. J. Atmos. Sci., 55 , 2730–2747.

    • Search Google Scholar
    • Export Citation

  • Houze Jr., R. A., 1993: Cloud Dynamics. Academic Press, 573 pp.

  • Houze Jr., R. A., and C-P. Cheng, 1977: Radar characteristics of tropical convection observed during GATE: Mean properties and trends over the summer season. Mon. Wea. Rev., 105 , 964–980.

    • Search Google Scholar
    • Export Citation

  • Iguchi, T., and R. Meneghini, 1994: Intercomparison of single-frequency methods for retrieving a vertical rain profile from airborne or spaceborne radar data. J. Atmos. Oceanic Technol., 11 , 1507–1516.

    • 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 , 2038–2052.

    • Search Google Scholar
    • Export Citation

  • Janowiak, J. E., P. A. Arkin, P. Xie, M. L. Morrissey, and D. R. Legates, 1995: An examination of the east Pacific ITCZ rainfall distribution. J. Climate, 8 , 2810–2823.

    • Search Google Scholar
    • Export Citation

  • Johnson, R. H., T. M. Rickenbach, S. A. Rutledge, P. E. Ciesielski, and W. H. Schubert, 1999: Trimodal characteristics of tropical convection. J. Climate, 12 , 2397–2418.

    • 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 , 809–817.

    • Search Google Scholar
    • Export Citation

  • Loehrer, S. M., T. A. Edmands, and J. A. Moore, 1996: TOGA COARE upper-air sounding data archive: Development and quality control procedures. Bull. Amer. Meteor. Soc., 77 , 2651–2671.

    • Search Google Scholar
    • Export Citation

  • López, R. E., 1977: The lognormal distribution and cumulus cloud populations. Mon. Wea. Rev., 105 , 865–872.

  • López, R. E., 1978: Internal structure and development processes of C-Scale aggregates of cumulus clouds. Mon. Wea. Rev., 106 , 1488–1494.

    • Search Google Scholar
    • Export Citation

  • Mapes, B. E., and J. Lin, 2005: Doppler radar observations of mesoscale wind divergence in regions of tropical convection. Mon. Wea. Rev., 133 , 1808–1824.

    • Search Google Scholar
    • Export Citation

  • Mapes, B. E., T. T. Warner, M. Xu, and A. J. Negri, 2003: Diurnal patterns of rainfall in northwestern South America. Part I: Observations and context. Mon. Wea. Rev., 131 , 799–812.

    • Search Google Scholar
    • Export Citation

  • Mechoso, C. R., and Coauthors, 1995: The seasonal cycle over the tropical Pacific in coupled ocean–atmosphere general circulation models. Mon. Wea. Rev., 123 , 2825–2838.

    • Search Google Scholar
    • Export Citation

  • Mohr, C. G., L. J. Miller, R. L. Vaughan, and H. W. Frank, 1986: The merger of mesoscale datasets into a common Cartesian format for efficient and systematic analyses. J. Atmos. Oceanic Technol., 3 , 143–161.

    • Search Google Scholar
    • Export Citation

  • Molinari, J., D. Vollaro, S. Skubis, and M. Dickenson, 2000: Origins and mechanisms of eastern Pacific tropical cyclogenesis: A case study. Mon. Wea. Rev., 128 , 125–139.

    • Search Google Scholar
    • Export Citation

  • Nesbitt, S. W., E. J. Zipser, and D. J. Cecil, 2000: A census of precipitation features in the Tropics using TRMM: Radar, ice scattering, and lightning observations. J. Climate, 13 , 4087–4106.

    • Search Google Scholar
    • Export Citation

  • Nesbitt, S. W., R. Cifelli, and S. A. Rutledge, 2006: Storm morphology and rainfall characteristics of TRMM precipitation features. Mon. Wea. Rev., 134 , 2702–2721.

    • Search Google Scholar
    • Export Citation

  • Newell, R. E., J. W. Kidson, D. G. Vincent, and G. J. Boer, 1974: The General Circulation of the Tropical Atmosphere. Vol. 2. MIT Press, 371 pp.

    • Search Google Scholar
    • Export Citation

  • Patterson, V. L., M. D. Hudlow, P. J. Pytlowaney, F. P. Richards, and J. D. Hoff, 1979: GATE radar rainfall processing system. NOAA Tech. Memo. EDIS 26, Washington, DC, 34 pp. [Available from the National Technical Information Service, Sills Building, 5285 Port Royal Rd., Springfield, VA 22161.].

  • Petersen, W. A., R. Cifelli, D. J. Boccippio, S. A. Rutledge, and C. Fairall, 2003: Convection and easterly wave structure in the eastern Pacific warm pool during EPIC-2001. J. Atmos. Sci., 60 , 1754–1773.

    • Search Google Scholar
    • Export Citation

  • Petersen, W. A., H. J. Christian, and S. A. Rutledge, 2005: TRMM observations of the global relationship between ice water content and lightning. Geophys. Res. Lett., 32 .L14189, doi:10.1029/2005GL023236.

    • Search Google Scholar
    • Export Citation

  • Raymond, D. J., G. B. Raga, C. S. Bretherton, J. Molinari, C. López-Carillo, and Z. Fuchs, 2003: Convective forcing in the intertropical convergence zone east Pacific. J. Atmos. Sci., 60 , 2064–2082.

    • Search Google Scholar
    • Export Citation

  • Raymond, D. J., and Coauthors, 2004: EPIC2001 and the coupled ocean–atmosphere system of the tropical east Pacific. Bull. Amer. Meteor. Soc., 85 , 1341–1354.

    • Search Google Scholar
    • Export Citation

  • Rickenbach, T. M., and S. A. Rutledge, 1998: Convection in TOGA COARE: Horizontal scale, morphology, and rainfall production. J. Atmos. Sci., 55 , 2715–2729.

    • Search Google Scholar
    • Export Citation

  • Serra, Y. L., and R. A. Houze Jr., 2002: Observations of variability on synoptic timescales in the east Pacific ITCZ. J. Atmos. Sci., 59 , 1723–1743.

    • Search Google Scholar
    • Export Citation

  • Short, D. A., and K. Nakamura, 2000: TRMM radar observations of shallow precipitation over the tropical oceans. J. Climate, 13 , 4107–4124.

    • Search Google Scholar
    • Export Citation

  • Short, D. A., P. A. Kucera, B. S. Ferrier, J. C. Gerlach, S. A. Rutledge, and O. W. Thiele, 1997: Shipboard radar rainfall patterns within the TOGA COARE IFA. Bull. Amer. Meteor. Soc., 78 , 2817–2836.

    • Search Google Scholar
    • Export Citation

  • Steiner, M., R. A. Houze Jr., and S. E. Yuter, 1995: Climatological characteristics of three-dimensional storm structure from operational radar and raingauge data. J. Appl. Meteor., 34 , 1978–2007.

    • Search Google Scholar
    • Export Citation

  • Sui, C-H., K-M. Lau, Y. N. Takayabu, and D. A. Short, 1997: Diurnal variations in tropical oceanic cumulus convection during TOGA COARE. J. Atmos. Sci., 54 , 639–655.

    • Search Google Scholar
    • Export Citation

  • Vincent, D. G., and A. H. Fink, 2001: Tropical cyclone environments over the northeastern and northwestern Pacific based on ERA-15 analyses. Mon. Wea. Rev., 129 , 1928–1948.

    • Search Google Scholar
    • Export Citation

  • Wang, C., and D. B. Enfield, 2001: The tropical western hemisphere warm pool. Geophys. Res. Lett., 28 , 1635–1638.

  • Wang, C., and D. B. Enfield, 2003: A further study of the tropical Western Hemisphere warm pool. J. Climate, 16 , 1476–1493.

  • Xie, P., and P. A. Arkin, 1996: Analyses of global monthly precipitation using gauge observations, satellite estimates, and numerical model predictions. J. Climate, 9 , 840–858.

    • Search Google Scholar
    • Export Citation

  • Xie, S-P., H. Xu, W. S. Kessler, and M. Nonaka, 2005: Air–sea interaction over the eastern Pacific warm pool: Gap winds, thermocline dome, and atmospheric convection. J. Climate, 18 , 5–20.

    • Search Google Scholar
    • Export Citation

  • Yuter, S. E., and R. A. Houze Jr., 1995: Three-dimensional kinematic and microphysical evolution of Florida cumulonimbus. Part II: Frequency distributions of vertical velocity, reflectivity, and differential reflectivity. Mon. Wea. Rev., 123 , 1941–1963.

    • Search Google Scholar
    • Export Citation

  • Yuter, S. E., and R. A. Houze Jr., 2000: The 1997 Pan American Climate Studies Tropical Eastern Pacific Process Study. Part I: ITCZ region. Bull. Amer. Meteor. Soc., 81 , 451–481.

    • Search Google Scholar
    • Export Citation

  • Zuidema, P., B. Mapes, J. Lin, C. Fairall, and G. Wick, 2006: The interaction of clouds and dry air in the eastern tropical Pacific. J. Climate, 19 , 4531–4544.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 269 67 2
PDF Downloads 163 49 4