The multi-dimensional anomaly characteristics of the western Pacific subtropical high during the development of the 2022 major drought in the Yangtze River Basin
The western Pacific subtropical high(WPSH)is a deep circulation system that affects weather and climate changes in China.Previous studies showed that the WPSH anomaly effects on extreme high temperature and drought events in the Yangtze River Basin,but mainly focused on the influence of one-dimensional anomaly such as zonal anomaly.At the same time,the development of high temperature and drought events also require the continuous anomaly of the WPSH.Under the influence of climate warming,the spatial distribution of the WPSH has four-dimensional anomalies,including meridional,zonal,thickness and area anomalies.Therefore,the one-dimension anomaly is not sufficient to describe its influence as the main controlling circulation factor on extreme high temperature and drought events.In 2022,a rare major drought occurred in the Yangtze River Basin,which was formed by the extreme low precipitation and high temperature from late summer to mid-autumn,and connected with the winter drought.The most distinctive features were extreme high temperature and drought in August.To reveal the influence of the multi-dimensional anomalies characteristics of the WPSH on the major drought in the Yangtze River Basin,we overcome limitation associated with one-dimensional anomaly analysis by focusing on the multi-dimensional anomalies characteristics of the WPSH during the development of this drought event.Our results showed that the westward anomaly is most significant feature at 500 hPa during August without obvious meridional anomaly.It covered largest area over the same period in the Yangtze River Basin.While extending vertically from lower layer to upper layer at 400-200 hPa,where the WPSH connected with South Asian High formed high-pressure dams,which resisted convergence of warm humid air from the ocean and cold air from the middle and high latitudes of the north.So the WPSH thickness was extremely deep,and aggravated the extreme high temperature and drought.By comparing multi-dimensional anomalies characteristics of the WPSH during different drought years in August,three types of influence on drought in the Yangtze River Basin can be identified.Firstly,non-sustainable temporal impact was observed in 2010,when spatial anomalies lasted for a short time,lead to onset of flash drought.Secondly,non-sustainable spatial impact was seen in 1998.Although spatial anomalies were not significant(meridional anomaly was southward with shallow thickness),prolonged duration resulted in more severe drought compared to non-sustainable temporal type.Thirdly,multi-dimensional anomalies persistence exemplified by 2022,when the WPSH exhibited abnormal long-lasting spatial anomalies(zonal anomaly was westward,the area was abnormally large,and the thickness was abnormally deep),the extreme high temperature and severe drought were most critical among these three types.Compared multi-dimensional anomalies with one-dimensional ones revealed that former better reflected complex impacts on processes related to extreme high temperature and drought.This study provides scientific support for understanding multi-dimensional anomalies characteristics of the WPSH and improving drought prediction techniques and addressing major drought challenges within the context of climate warming.
2022Yangtze River Basinmajor droughtwestern Pacific subtropical highmulti-dimensional anomaly characteristics
NETL
NSTL
万方数据
