Page 137 - 《高原气象》2022年第6期

高 原 气 象 41 卷
1500

Varation Characteristics Causes of Autumn Rain in Westem China

MEI Shuangli ，CHEN Shangfeng 2
1
（1. National Meteorological Center，Beijing 100081，China；
2. Center for Monsoon System Research，Institute of Atmospheric Physics，Chinese Academy of Sciences，Beijing 100029，China）

Abstract：Based on 373 stations precipitation data in West China and National Centers for Environmental Predic‐
tion/National Center for Atmospheric Research（NCEP/NCAR）reanalysis data，variation characteristics of au‐
tumn rain in Western China are investigated，and associated atmospheric circulation systems affecting autumn
rain in Western China and their interactiovemechanism are explored in this study. The results show that there are
significant interannual variation characteristics of autumn rain in Western China. When more rainfall occurs in au‐
tumn in West China，there is an abnormal anticyclone at the low troposphere over the northern Philippines，and
the associated southerly wind anomalies to the west side of this anticyclone anomaly carry warmer and wetter wa‐
ter vapor from northern Arabian Sea-Indian Peninsula-northern Bay of Bengal-China Peninsula to Western China.
At the same time，the positive geopotential height anomaly，representing enhanced blocking activities，is ob‐
served over Europe，and the negative geopotential height anomaly，indicating enhanced low trough，is observed
near Lake Balcosh in the middle troposphere. Therefore，this anomalous circulation configuration is conducive to
the outbreak of cold air from higher latitude southward to West China. A clear atmospheric circulation teleconnec‐
tion which plays an important role in the maintenance and development of blocking high in Europe and low-pres‐
sure trough near Lake Balcosh as well as circulation anomalies over East Asia，is seen over mid-high latitudes of
Eurasia in the upper troposphere. Further analysis shows that the suppressed convection activities near the Philip‐
pines and Taiwan Island and the southern equatorial Indian Ocean play an important role in the maintenance of
the anomalous anticyclone in the northern Philippines. On the other hand，when there is less rainfall in autumn in
West China，the Eurasian wave train anomaly causes the positive height potential anomaly in Balkash Lake，
which is not conducive to the establishment of low trough and the activity of cold air in West China. The active
convection in the northern Philippines and the Equatorial East Indian Ocean and the negative height anomaly of
Northeast Asia caused by Eurasian wave train lead to the formation of north wind anomaly in West China，which
is unfavourable for the northward movement of warm air，and the divergence of water vapor flux in West China
is unfavourable for precipitation. In shore，this configuration is not beneficial to precipitation. Therefore，the re‐
sults in this study have certain application value for improving the understanding of the characteristics and mecha‐
nism of interannual variation of autumn rain in Western China and further improving its prediction level.
Key words：Autumn rain of West China；interannual variation；tropical convection；wave train