Study on the Dynamic Process of the Onset of South China Sea Summer Monsoon

+ Author Affiliations + Find other works by these authors
  • Funds:

    Supported by the National Key Programme for Developing Basic Sciences (2007CB411800).

PDF

  • By using the NCEP/NCAR reanalysis data from 1958 to 1997, we first looked into the atmospheric flow conditions in the one month immediately prior to the onset of the South China Sea summer monsoon (SCSSM) each year. A monthly-averaged zonal basic flow of 40-yr composite was then calculated. The stability of Rossby wave in the basic flow was studied based on the spherical barotropic vorticity equation. Furthermore, the spectral function expansion method was adopted to de ne and compute the evolvement of a developing wave packet. The results indicate that there exists barotropic instability of spherical Rossby wave in the climatically-averaged flow eld before the SCSSM onset. The instability is triggered by the westerly jet stream in the Southern Hemisphere, and the strongest instable perturbation lies to the south of the westerly jet stream. The peak of the developing spherical Rossby wave packet propagates from mid and high latitudes to low latitudes, though not crossing the equator, spurring the cumulus convection in the tropical zones. The eruption of the cumulus convection and its spread to monsoon regions help to speed up the adjustment of the general circulation and the SCSSM onset. It is concluded that elements that contribute to the SCSSM onset are on global scale, albeit the onset itself looks like a local phenomenon.
  • 加载中
  • 加载中
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Study on the Dynamic Process of the Onset of South China Sea Summer Monsoon

  • 1. Institute of Meteorology,PLA University of Science and Technology,Nanjing 211101;
    Institute of Meteorology,PLA University of Science and Technology,Nanjing 211101;
    Institute of Meteorology,PLA University of Science and Technology,Nanjing 211101
Funds: Supported by the National Key Programme for Developing Basic Sciences (2007CB411800).

Abstract: By using the NCEP/NCAR reanalysis data from 1958 to 1997, we first looked into the atmospheric flow conditions in the one month immediately prior to the onset of the South China Sea summer monsoon (SCSSM) each year. A monthly-averaged zonal basic flow of 40-yr composite was then calculated. The stability of Rossby wave in the basic flow was studied based on the spherical barotropic vorticity equation. Furthermore, the spectral function expansion method was adopted to de ne and compute the evolvement of a developing wave packet. The results indicate that there exists barotropic instability of spherical Rossby wave in the climatically-averaged flow eld before the SCSSM onset. The instability is triggered by the westerly jet stream in the Southern Hemisphere, and the strongest instable perturbation lies to the south of the westerly jet stream. The peak of the developing spherical Rossby wave packet propagates from mid and high latitudes to low latitudes, though not crossing the equator, spurring the cumulus convection in the tropical zones. The eruption of the cumulus convection and its spread to monsoon regions help to speed up the adjustment of the general circulation and the SCSSM onset. It is concluded that elements that contribute to the SCSSM onset are on global scale, albeit the onset itself looks like a local phenomenon.

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return