• Aiyyer, A. R., , and J. Molinari, 2003: Evolution of mixed Rossby–gravity waves in idealized MJO environments. J. Atmos. Sci., 60, 28372855, doi:10.1175/1520-0469(2003)060<2837:EOMRWI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Bolton, D., 1980: Application of the Miles theorem to forced linear perturbations. J. Atmos. Sci., 37, 16391642, doi:10.1175/1520-0469(1980)037<1639:AOTMTT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Boyd, J. P., 1978a: The effects of latitudinal shear on equatorial waves. Part I: Theory and methods. J. Atmos. Sci., 35, 22362258, doi:10.1175/1520-0469(1978)035<2236:TEOLSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Boyd, J. P., 1978b: The effects of latitudinal shear on equatorial waves. Part II: Applications to the atmosphere. J. Atmos. Sci., 35, 22592267, doi:10.1175/1520-0469(1978)035<2259:TEOLSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chang, C. P., , V. F. Morris, , and J. M. Wallace, 1970: A statistical study of easterly waves in the western Pacific: July–December 1964. J. Atmos. Sci., 27, 195201, doi:10.1175/1520-0469(1970)027<0195:ASSOEW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, G., 2012: A comparison of the transition of equatorial waves between two types of ENSO events in a multilevel model. J. Atmos. Sci., 69, 23642378, doi:10.1175/JAS-D-11-0292.1.

    • Search Google Scholar
    • Export Citation
  • Chen, G., , and R. Huang, 2009: Interannual variations in mixed Rossby–gravity waves and their impacts on tropical cyclogenesis over the western North Pacific. J. Climate, 22, 535549, doi:10.1175/2008JCLI2221.1.

    • Search Google Scholar
    • Export Citation
  • Chen, G., , and C.-H. Sui, 2010: Characteristics and origin of quasi-biweekly oscillation over the western North Pacific during boreal summer. J. Geophys. Res., 115, D14113, doi:10.1029/2009JD013389.

    • Search Google Scholar
    • Export Citation
  • Chen, G., , and C.-Y. Tam, 2012: A new perspective on the excitation of low-tropospheric mixed Rossby–gravity waves in association with energy dispersion. J. Atmos. Sci., 69, 13971403, doi:10.1175/JAS-D-11-0331.1.

    • Search Google Scholar
    • Export Citation
  • Chen, G., , and C. Chou, 2014: Joint contribution of multiple equatorial waves to tropical cyclogenesis over the western North Pacific. Mon. Wea. Rev., 142, 7993, doi:10.1175/MWR-D-13-00207.1.

    • Search Google Scholar
    • Export Citation
  • Davies, H. C., 1979: Phase-lagged wave-CISK. Quart. J. Roy. Meteor. Soc., 105, 325353, doi:10.1002/qj.49710544402.

  • Dickinson, M., , and J. Molinari, 2002: Mixed Rossby–gravity waves and western Pacific tropical cyclogenesis. Part I: Synoptic evolution. J. Atmos. Sci., 59, 21832196, doi:10.1175/1520-0469(2002)059<2183:MRGWAW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Dunkerton, T. J., , and M. P. Baldwin, 1995: Observation of 3–6-day meridional wind oscillations over the tropical Pacific, 1973–1992: Horizontal structure and propagation. J. Atmos. Sci., 52, 15851601, doi:10.1175/1520-0469(1995)052<1585:OODMWO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Feng, T., , G. H. Chen, , R. H. Huang, , and X. Y. Shen, 2014: Large-scale circulation patterns favourable to tropical cyclogenesis over the western North Pacific and associated barotropic energy conversions. Int. J. Climatol., 34, 216227, doi:10.1002/joc.3680.

    • Search Google Scholar
    • Export Citation
  • Frank, W. M., , and P. E. Roundy, 2006: The role of tropical waves in tropical cyclogenesis. Mon. Wea. Rev., 134, 23972417, doi:10.1175/MWR3204.1.

    • Search Google Scholar
    • Export Citation
  • Fu, B., , T. Li, , M. S. Peng, , and F. Weng, 2007: Analysis of tropical cyclogenesis in the western North Pacific for 2000 and 2001. Wea. Forecasting, 22, 763780, doi:10.1175/WAF1013.1.

    • Search Google Scholar
    • Export Citation
  • Ge, X., , T. Li, , and X. Zhou, 2007: Tropical cyclone energy dispersion under vertical shears. Geophys. Res. Lett., 34, L23807, doi:10.1029/2007GL031867.

    • Search Google Scholar
    • Export Citation
  • Ge, X., , T. Li, , Y. Wang, , and M. S. Peng, 2008: Tropical cyclone energy dispersion in a three-dimensional primitive equation model: Upper-tropospheric influence. J. Atmos. Sci., 65, 22722289, doi:10.1175/2007JAS2431.1.

    • Search Google Scholar
    • Export Citation
  • Han, Y., , and B. Khouider, 2010: Convectively coupled waves in a sheared environment. J. Atmos. Sci., 67, 29132942, doi:10.1175/2010JAS3335.1.

    • Search Google Scholar
    • Export Citation
  • Hayashi, Y., 1970: A theory of large-scale equatorial waves generated by condensation heat and accelerating. J. Meteor. Soc. Japan, 48, 140160.

    • Search Google Scholar
    • Export Citation
  • Holland, G. J., 1995: Scale interaction in the western Pacific monsoon. Meteor. Atmos. Phys., 56, 5779, doi:10.1007/BF01022521.

  • Holton, J. R., 1971: A diagnostic model for equatorial wave disturbances: The role of vertical shear of the mean zonal wind. J. Atmos. Sci., 28, 5564, doi:10.1175/1520-0469(1971)028<0055:ADMFEW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Holton, J. R., 2004: An Introduction to Dynamic Meteorology. 4th ed. Elsevier Academic Press, 535 pp.

  • Huang, P., , and R. Huang, 2011: Climatology and interannual variability of convectively coupled equatorial waves activity. J. Climate, 24, 44514465, doi:10.1175/2011JCLI4021.1.

    • Search Google Scholar
    • Export Citation
  • Kanamitsu, M., , W. Ebisuzaki, , J. Woollen, , S.-K. Yang, , J. J. Hnilo, , M. Fiorino, , and G. L. Potter, 2002: NCEP–DOE AMIP-II reanalysis (R-2). Bull. Amer. Meteor. Soc., 83, 16311643, doi:10.1175/BAMS-83-11-1631.

    • Search Google Scholar
    • Export Citation
  • Kiladis, G. N., , J. Dias, , and M. Gehne, 2016: The relationship between equatorial mixed Rossby–gravity and eastward inertio-gravity waves. Part I. J. Atmos. Sci., 73, 21232145, doi:10.1175/JAS-D-15-0230.1.

    • Search Google Scholar
    • Export Citation
  • Krouse, K. D., , A. H. Sobel, , and L. M. Polvani, 2008: On the wavelength of the Rossby waves radiated by tropical cyclones. J. Atmos. Sci., 65, 644654, doi:10.1175/2007JAS2402.1.

    • Search Google Scholar
    • Export Citation
  • Kuo, H.-C., , J.-H. Chen, , R. T. Williams, , and C. P. Chang, 2001: Rossby waves in zonally opposing mean flow: Behavior in Northwest Pacific summer monsoon. J. Atmos. Sci., 58, 10351050, doi:10.1175/1520-0469(2001)058<1035:RWIZOM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lane, T. P., , M. J. Reeder, , and T. L. Clark, 2001: Numerical modeling of gravity wave generation by deep tropical convection. J. Atmos. Sci., 58, 12491274, doi:10.1175/1520-0469(2001)058<1249:NMOGWG>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lau, K.-H., , and N.-C. Lau, 1990: Observed structure and propagation characteristics of tropical summertime synoptic scale disturbances. Mon. Wea. Rev., 118, 18881913, doi:10.1175/1520-0493(1990)118,1888:OSAPCO.2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lau, K.-H., , and N.-C. Lau, 1992: The energetics and propagation dynamics of tropical summertime synoptic-scale disturbances. Mon. Wea. Rev., 120, 25232539, doi:10.1175/1520-0493(1992)120,2523:TEAPDO.2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Li, T., 2006: Origin of the summertime synoptic-scale wave train in the western North Pacific. J. Atmos. Sci., 63, 10931102, doi:10.1175/JAS3676.1.

    • Search Google Scholar
    • Export Citation
  • Liebmann, B., , and H. H. Hendon, 1990: Synoptic-scale disturbances near the equator. J. Atmos. Sci., 47, 14631479, doi:10.1175/1520-0469(1990)047<1463:SSDNTE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Liebmann, B., , and C. A. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77, 12751277.

    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., 1974: Wave-CISK in the tropics. J. Atmos. Sci., 31, 156179, doi:10.1175/1520-0469(1974)031<0156:WCITT>2.0.CO;2.

  • Lipps, F. B., 1970: Barotropic stability and tropical disturbances. Mon. Wea. Rev., 98, 122131, doi:10.1175/1520-0493(1970)098<0122:BSATD>2.3.CO;2.

    • Search Google Scholar
    • Export Citation
  • Livezey, R. E., , and W. Y. Chen, 1983: Statistical field significance and its determination by Monte Carlo techniques. Mon. Wea. Rev., 111, 4659, doi:10.1175/1520-0493(1983)111<0046:SFSAID>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Maloney, E. D., , and D. L. Hartmann, 2001: The Madden–Julian oscillation, barotropic dynamics, and North Pacific tropical cyclone formation. Part I: Observations. J. Atmos. Sci., 58, 25452558, doi:10.1175/1520-0469(2001)058<2545:TMJOBD>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., 2000: Convective inhibition, subgrid-scale triggering energy, and stratiform instability in a toy tropical wave model. J. Atmos. Sci., 57, 15151535, doi:10.1175/1520-0469(2000)057<1515:CISSTE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., , K. Lombardo, , and D. Vollaro, 2007: Tropical cyclogenesis within an equatorial Rossby wave packet. J. Atmos. Sci., 64, 13011317, doi:10.1175/JAS3902.1.

    • Search Google Scholar
    • Export Citation
  • NCEP/NWS/NOAA/DOC, 2000: NCEP/DOE Reanalysis 2 (R2). Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, accessed 11 August 2015. [Available online at http://rda.ucar.edu/datasets/ds091.0/.]

  • Nitta, T., , and M. Yanai, 1969: A note on the barotropic instability of the tropical easterly current. J. Meteor. Soc. Japan, 47, 127130.

    • Search Google Scholar
    • Export Citation
  • Nitta, T., , and Y. Takayabu, 1985: Global analysis of the lower tropospheric disturbances in the tropics during the northern summer of the FGGE year part II: Regional characteristics of the disturbances. Pure Appl. Geophys. (PAGEOPH), 123, 272292, doi:10.1007/BF00877023.

    • Search Google Scholar
    • Export Citation
  • NOAA/OAR/ESRL/PSD, 1996: NOAA interpolated outgoing longwave radiation (OLR). NOAA/ESRL/Physical Sciences Division, Data Management, accessed 5 February 2015.[Available online at http://www.esrl.noaa.gov/psd/data/gridded/data.interp_OLR.html.]

  • Park, M. S., , H. S. Kim, , C. H. Ho, , R. L. Elsberry, , and M. I. Lee, 2015: Tropical Cyclone Mekkhala’s (2008) formation over the South China Sea: Mesoscale, synoptic-scale, and large-scale contributions. Mon. Wea. Rev., 143, 88110, doi:10.1175/MWR-D-14-00119.1.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., , and Ž. Fuchs, 2007: Convectively coupled gravity and moisture modes in a simple atmospheric model. Tellus, 59A, 627640, doi:10.1111/j.1600-0870.2007.00268.x.

    • Search Google Scholar
    • Export Citation
  • Reed, R. J., , and E. E. Recker, 1971: Structure and properties of synoptic-scale wave disturbances in the equatorial western Pacific. J. Atmos. Sci., 28, 11171133, doi:10.1175/1520-0469(1971)028<1117:SAPOSS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Schreck, C. J., , J. Molinari, , and K. I. Mohr, 2011: Attributing tropical cyclogenesis to equatorial waves in the western North Pacific. J. Atmos. Sci., 68, 195209, doi:10.1175/2010JAS3396.1.

    • Search Google Scholar
    • Export Citation
  • Schreck, C. J., , J. Molinari, , and A. Aiyyer, 2012: A global view of equatorial waves and tropical cyclogenesis. Mon. Wea. Rev., 140, 774788, doi:10.1175/MWR-D-11-00110.1.

    • Search Google Scholar
    • Export Citation
  • Serra, Y. L., , G. N. Kiladis, , and M. F. Cronin, 2008: Horizontal and vertical structure of easterly waves in the Pacific ITCZ. J. Atmos. Sci., 65, 12661284, doi:10.1175/2007JAS2341.1.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., , and C. S. Bretherton, 1999: Development of synoptic-scale disturbances over the summertime tropical northwest Pacific. J. Atmos. Sci., 56, 31063127, doi:10.1175/1520-0469(1999)056<3106:DOSSDO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., , J. Nilsson, , and L. M. Polvani, 2001: The weak temperature gradient approximation and balanced tropical moisture waves. J. Atmos. Sci., 58, 36503665, doi:10.1175/1520-0469(2001)058<3650:TWTGAA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Tai, K.-S., , and Y. Ogura, 1987: An observational study of easterly waves over the eastern Pacific in the northern summer using FGGE data. J. Atmos. Sci., 44, 339361, doi:10.1175/1520-0469(1987)044<0339:AOSOEW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Takayabu, Y. N., , and T. Nitta, 1993: 3–5 day-period disturbances coupled with convection over the tropical Pacific Ocean. J. Meteor. Soc. Japan, 71, 221246.

    • Search Google Scholar
    • Export Citation
  • Tam, C. Y., , and T. Li, 2006: The origin and dispersion characteristics of the observed tropical summertime synoptic-scale waves over the western Pacific. Mon. Wea. Rev., 134, 16301646, doi:10.1175/MWR3147.1.

    • Search Google Scholar
    • Export Citation
  • Wallace, J. M., 1971: Spectral studies of tropospheric wave disturbances in the tropical western Pacific. Rev. Geophys., 9, 557612, doi:10.1029/RG009i003p00557.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and X. Xie, 1996: Low-frequency equatorial waves in vertically sheared zonal flow. Part I: Stable waves. J. Atmos. Sci., 53, 449467, doi:10.1175/1520-0469(1996)053<0449:LFEWIV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., , and H.-R. Chang, 1988: Equatorial energy accumulation and emanation regions: Impacts of a zonally varying basic state. J. Atmos. Sci., 45, 803829, doi:10.1175/1520-0469(1988)045<0803:EEAAER>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., , and H.-R. Chang, 1998: Atmospheric wave propagation in heterogeneous flow: Basic flow controls on tropical–extratropical interaction and equatorial wave modification. Dyn. Atmos. Oceans, 27, 91134, doi:10.1016/S0377-0265(97)00003-1.

    • Search Google Scholar
    • Export Citation
  • Wheeler, M., , and G. N. Kiladis, 1999: Convectively coupled equatorial waves: Analysis of clouds and temperature in the wavenumber–frequency domain. J. Atmos. Sci., 56, 374399, doi:10.1175/1520-0469(1999)056<0374:CCEWAO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wu, L., , Z. Wen, , R. Huang, , and R. Wu, 2012: Possible linkage between the monsoon trough variability and the tropical cyclone activity over the western North Pacific. Mon. Wea. Rev., 140, 140150, doi:10.1175/MWR-D-11-00078.1.

    • Search Google Scholar
    • Export Citation
  • Wu, L., , Z. Wen, , T. Li, , and R. Huang, 2014: ENSO-phase dependent TD and MRG wave activity in the western North Pacific. Climate Dyn., 42, 12171227, doi:10.1007/s00382-013-1754-4.

    • Search Google Scholar
    • Export Citation
  • Wu, L., , Z. Wen, , and R. Wu, 2015a: Influence of the monsoon trough on westward-propagating tropical waves over the western North Pacific. Part I: Observations. J. Climate, 28, 71087127, doi:10.1175/JCLI-D-14-00806.1.

    • Search Google Scholar
    • Export Citation
  • Wu, L., , Z. Wen, , and R. Wu, 2015b: Influence of the monsoon trough on westward-propagating tropical waves over the western North Pacific. Part II: Energetics and numerical experiments. J. Climate, 28, 93329349, doi:10.1175/JCLI-D-14-00807.1.

    • Search Google Scholar
    • Export Citation
  • Xie, X., , and B. Wang, 1996: Low-frequency equatorial waves in vertically sheared zonal flow. Part II: Unstable waves. J. Atmos. Sci., 53, 35893605, doi:10.1175/1520-0469(1996)053,3589:LFEWIV.2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Xu, Y., , T. Li, , and M. Peng, 2013: Tropical cyclogenesis in the western North Pacific as revealed by the 2008–09 YOTC data. Wea. Forecasting, 28, 10381056, doi:10.1175/WAF-D-12-00104.1.

    • Search Google Scholar
    • Export Citation
  • Xu, Y., , T. Li, , and M. Peng, 2014: Roles of the synoptic-scale wave train, the intraseasonal oscillation, and high-frequency eddies in the genesis of Typhoon Manyi (2001). J. Atmos. Sci., 71, 37063722, doi:10.1175/JAS-D-13-0406.1.

    • Search Google Scholar
    • Export Citation
  • Yang, G.-Y., , B. Hoskins, , and J. Slingo, 2003: Convectively coupled equatorial waves: A new methodology for identifying wave structures in observational data. J. Atmos. Sci., 60, 16371654, doi:10.1175/1520-0469(2003)060<1637:CCEWAN>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Zhang, M., , and M. A. Geller, 1994: Selective excitation of tropical atmospheric waves in wave-CISK: The effect of vertical wind shear. J. Atmos. Sci., 51, 353368, doi:10.1175/1520-0469(1994)051<0353:SEOTAW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Zhou, X., , and B. Wang, 2007: Transition from an eastern Pacific upper-level mixed Rossby–gravity wave to a western Pacific tropical cyclone. Geophys. Res. Lett., 34, L24801, doi:10.1029/2007GL031831.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 55 55 13
PDF Downloads 32 32 10

Synoptic-Scale Waves in Sheared Background Flow over the Western North Pacific

View More View Less
  • 1 China Meteorological Administration–Nanjing University Joint Laboratory for Climate Prediction Studies, Institute for Climate and Global Change Research, School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • | 2 Guy Carpenter Asia-Pacific Climate Impact Center, School of Energy and Environment, City University of Hong Kong, Hong Kong, China
  • | 3 Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • | 4 China Meteorological Administration–Nanjing University Joint Laboratory for Climate Prediction Studies, Institute for Climate and Global Change Research, School of Atmospheric Sciences, Nanjing University, Nanjing, China
© Get Permissions
Restricted access

Abstract

Tropical depression (TD)-type waves are the dominant mode of synoptic-scale fluctuations over the western North Pacific. By applying spatiotemporal filters to the observed OLR data and the NCEP–DOE AMIP-II reanalysis data for 1979–2013, this study reveals the characteristics and energetics of convectively coupled TD-type waves under the effects of different circulation patterns in association with vertical wind shear. Results exhibit that different ambient sheared flows significantly affect the vertical structure of westward-propagating TD-type waves, with a lower-tropospheric mode in an easterly sheared background and an upper-tropospheric mode in a westerly sheared background. Energetic diagnoses demonstrate that when the disturbance is trapped in the lower (upper) level by easterly (westerly) shear, the horizontal mean flow in the lower (upper) level favors wave growth by converting energy from the shear of the zonal mean flow (from the convergence of the meridional mean flow). During the penetration of a westward-propagating synoptic-scale disturbance from a westerly sheared flow into an easterly sheared flow, the upper-level disturbance decays, and the lower-level disturbance intensifies. Meanwhile, the upper-level kinetic energy is transferred downward, but the effect induces the wave growth only confined to the midlevels. Consequently, the low-level growth of the westward-propagating upper-level synoptic-scale disturbance is mainly attributed to the barotropic conversion of horizontal mean flow in the lower troposphere.

Corresponding author address: Prof. Xiu-Qun Yang, School of Atmospheric Sciences, Nanjing University, 163 Xianlin Avenue, Nanjing 210023, China. E-mail: xqyang@nju.edu.cn

Abstract

Tropical depression (TD)-type waves are the dominant mode of synoptic-scale fluctuations over the western North Pacific. By applying spatiotemporal filters to the observed OLR data and the NCEP–DOE AMIP-II reanalysis data for 1979–2013, this study reveals the characteristics and energetics of convectively coupled TD-type waves under the effects of different circulation patterns in association with vertical wind shear. Results exhibit that different ambient sheared flows significantly affect the vertical structure of westward-propagating TD-type waves, with a lower-tropospheric mode in an easterly sheared background and an upper-tropospheric mode in a westerly sheared background. Energetic diagnoses demonstrate that when the disturbance is trapped in the lower (upper) level by easterly (westerly) shear, the horizontal mean flow in the lower (upper) level favors wave growth by converting energy from the shear of the zonal mean flow (from the convergence of the meridional mean flow). During the penetration of a westward-propagating synoptic-scale disturbance from a westerly sheared flow into an easterly sheared flow, the upper-level disturbance decays, and the lower-level disturbance intensifies. Meanwhile, the upper-level kinetic energy is transferred downward, but the effect induces the wave growth only confined to the midlevels. Consequently, the low-level growth of the westward-propagating upper-level synoptic-scale disturbance is mainly attributed to the barotropic conversion of horizontal mean flow in the lower troposphere.

Corresponding author address: Prof. Xiu-Qun Yang, School of Atmospheric Sciences, Nanjing University, 163 Xianlin Avenue, Nanjing 210023, China. E-mail: xqyang@nju.edu.cn
Save