Characteries of Boreal Autumn Hadley Circulation over the Asian Domain and Its Relationship with Tropical SST

Abstract

Using the Hadley Centre Sea Ice and Sea Surface Temperature dataset and NCEP reanalysis data during 1979 -2020， this paper analyzes the characteries of boreal autumn Hadley circulation （HC） over the Asian domain and its relationship with tropical sea surface temperature.The results find that the autumn regional HC is equatorial asymmetric in the last 42 years， with ascending branch located near the equator and sinking branch in the subtropical.The first model （EOF1） accounts for 59%， and the spatial distribution of the autumn regional HC is equatorial asymmetric， with the northern cell is dominant and larger than the southern cell.The ascending branch located to the south of the equator， The time distribution shows an interannual variation and it’s related to the ENSO （El Niño-Southern Oscillation）.During the La Niña events， the Tropical Indian Ocean （TIO） exists the significant negative anomaly and the abnormal cooling in the northern Indian Ocean is greater than that in the southern Indian Ocean， which leads to the anomalous meridional gradient in the TIO.It promotes the formation of EOF1.The EOF2 accounts for 15%， and the spatial distribution in the EOF2 shows that the southern cell is consistent with the region HC ascending branch range.The temporal distribution shows an increasing trend.The range of the rising branch is related to the warming trend of the TIO southern and northern hemispheres in the Asian monsoon region.The warming rate of the northern TIO is faster than the southern TIO， resulting in regional HC ascending scope of the north.

Keywords

• regional hadley circulation
• la niña events
• enso
• sea surface temperature
• tropical indian ocean