Climatological Features of the Global Tropical Subsidence Region Based on Satellite Observations

Consisting of subtropical highs and tropical buffer zone, the global tropical subsidence region is the subsidence branches of Hadley cell, Walker circulation and monsoon circulation which are important com-ponents of the global general circulation. This region is closely connected with Asian monsoon. Based on long-term satellite observations of OLR (Outgoing Longwave Radiation) and HIRS-Tbl2 (the bright tem-perature from High-resolution Infra-red Radiation Sounder Channel 12 (6.7μm)), the climatological fea-tures over the global tropical subsidence region are studied in this paper and the main findings are as follows:1) Based on the physical meaning of satellite observed HIRS-12 and comparison with the satellite ob?served OLR and climatological maps of conventional observations of geopotential height and vertical veloc?ity at 500 hPa from NCEP / NCAR reanalysis data, it was found that HIRS-12 might be the best indicator of the global tropical subsidence region from the satellite observations.2) Using satellite observed HIRS-12, some new climatological features were revealed, especially those related with Asian monsoon.3) Comparing the climatological characteristics of tropical subsidence regions between both hemi-spheres, it was found that the circulation in the Northern Hemisphere is more complicated and much closely related with monsoon circulation than that in the Southern Hemisphere. Sudden decay of subsidence movement before monsoon onsets over the South China Sea revealed by HIRS-12 suggested that in the future study of Asian monsoon, it should be paid attention to not only the development of convection but also the variation of tropical subsidence region. It is very useful to monitor the convective and subsidence movements in the tropics by using OLR and HIRS-Tbl2 have been observed from satellite.