Page 47 - 《高原气象》2022年第5期

高 原 气 象 41 卷
1140

The Relationship between the Increase of Extreme Snowfall in

Winter of Central Asia and the Enhancement of Two
SST Modes in the North Atlantic

LI Shuangshuang，ZHANG Jie，CHEN Zhiheng
（Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster
of Ministry of Education，Nanjing University of Information Science & Technology，Nanjing 210044，Jiangsu，China）

Abstract：On the basis of the daily precipitation data from 1979 to 2018 provided by the Climate Prediction Cen‐
ter（CPC），the global reanalysis data from the European Centre for Medium-Range Weather Forecasts（EC‐
MWF）and the sea surface temperature（SST）data from National Oceanic and Atmospheric Administration（NO‐
AA），this study analyzes the spatial and temporal variation of extreme snowfall in Central Asia and its relation‐
ship with the North Atlantic SST. Results are verified by sensitivity test through the CAM5. 1 module of the Com‐
munity Earth System Model CESM1. 0. 4. The results show that：the spatial distribution of extreme snowfall in
winter of Central Asia is extremely uneven. Extreme snowfall mainly occurs in Kazakhstan，Kyrgyzstan，Tajiki‐
stan and northern Xinjiang，and there is less extreme snowfall in the desert regions of Uzbekistan，Turkmenistan
and southern Xinjiang；four extreme snowfall indices show significant increasing trend in Central Asia and all cli‐
mate subregions. And the highest rate of interannual variation is the key southern subregion represented by Tien‐
shan mountain. The increased frequency of extreme snowfall in the key southern subregion corresponds to the en‐
hancement of the two wave trains along the North Atlantic jet and the Asian-African jet. The wave sources locate
over the subtropical North Atlantic and the tropical North Atlantic，and corresponding the North Atlantic SST
“uniform”and“tri-polar”modes. Since 2000，the increased subtropical（tropical）SST and the first two modes
indices are helpful for the westward extension of the Asian-African jet，and docking with the North Atlantic jet，
which strengthens the energy dispersion downstream along the two jets and the two wave trains，which in turn
leads to the strengthening of the cyclone anomaly in the Balkhash Lake and the anticyclone anomaly in the north‐
ern Arabian Sea，both of which enhance the southwest water vapor transport from the Arabian Sea as well as the
convergence in southern Central Asia，these factors increase the extreme snowfall events since 2000. The results
of CESM verfity the effect of the subtropical and tropical North Atlantic SST through wave trains and vortex
anomalies on extreme snowfall.
Key words：Arid Central Asia；extreme snowfall；North Atlantic SST；uniform；tri-polar