Page 35 - 《高原气象》2022年第6期

高 原 气 象 41 卷
1398

Influence of the Qinghai-Xizang Plateau Spring Snow Cover Variation

on the Boreal Summer Intraseasonal Oscillation

CAO Yanchao，WANG Xiaochun
（School of Marine Sciences，Nanjing University of Information Science and Technology，Nanjing 210044，Jiangsu，China）

Abstract：Snow cover over the Qinghai-Xizang Plateau（QXP）is an important physical factor that affects the
Asian monsoon system through atmospheric circulation. The boreal summer intraseasonal oscillation（BSISO，
including a 30~60-day BSISO mode named BSISO1 and a 10~30-day BSISO mode called BSISO2）is an essen‐
tial part of the monsoon system，its convection and circulation anomalies can affect the local precipitation by
changing the background conditions of the weather system. In this study，the snow depth data from 1981 to 2016
provided by the Northwest Institute of Eco-Environment and Resources，Chinese Academy of Sciences was used
to analyze the influence of the Qinghai-Xizang Plateau snow depth anomaly on BSISO. The results show that the
convective activities related to BSISO1 is enhanced（reduced）in the Bay of Bengal and the Maritime Continent
and reduced（enhanced）in the South China Sea and the Western North Pacific region when the Qinghai-Xizang
Plateau with more（less）snow cover. The convective activity related to BSISO2 is enhanced（reduced）in the
northern Indian Ocean，Maritime Continent，the East China Sea，and the South China Sea region，and reduced
（enhanced）in the Northwest Pacific. The snow cover over the plateau can affect the convective activity of
BSISO1 by influencing the background field of Asian summer monsoon and humidity. When the plateau has
more（less）snow in spring，the vertical northeast wind shear between 200 hPa and 850 hPa is enhanced（re‐
duced）in the North Indian Ocean region，and the humidity gradient between the northern Indian Ocean and the
Bay of Bengal increases（decreases），which is（not）in favor of the propagation of convective activities related
with BSISO1 to the Bay of Bengal and Maritime Continent region. At the same time，the decrease of water vapor
in the Maritime Continent region is not in favor of the propagation of convective activities related with BSISO1
to the South China Sea and the Western North Pacific.
Key words：Inter-annual variability；boreal summer intraseasonal oscillation；Qinghai-Xizang Plateau snow
cover anomaly