| China has a vast territory,spanning multiple latitudes and longitudes.There are also differences between coastal area and inland areas.In addition,the terrain is different and the topography is complex.Therefore,meteorological elements such as temperature and precipitation vary greatly in different regions,forming a variety of climates in China.Under the background of current climate change,the study of precipitation change and its mechanism has always been a hot issue in climate change research.In this paper,precipitation is divided into two categories:non-persistent precipitation and persistent precipitation.A new definition method is used to redefine extreme precipitation based on process cumulative rainfall.After analyzing the changes of two types of extreme precipitation in China,the northwest China(NWC)and the Yangtze-Huai River Valley(YHRV)were selected as typical arid and humid region in China for further research.The new method is used to define the regional non-persistent extreme precipitation(RNPEP)and regional persistent extreme precipitation(RPEP)processes,and the circulation of each level is analyzed.The similarities and differences of circulation configuration of different types of precipitation and different regions are compared and analyzed.Furthermore,the self-organizing map(SOM)method is used to output the dynamic factor-large-scale circulation pattern affecting the warm season extreme precipitation in NWC and YHRV into 20 types with 5×4 output nodes.The favorable circulation patterns for the NWC and YHRV were selected,and the changes of dynamic and thermal factors on precipitation were quantitatively evaluated.The main conclusion are summarized as follow:(1)From the spatial distribution pattern of non-continuous and persistent extreme precipitation trends nationwide,Non-sustained extreme precipitation tends to increase in most parts of China.Only a few sites are decreasing;However,persistent extreme precipitation shows an increasing trend in the middle and lower reaches of the Yangtze River Basin and parts of the South China coast.From the changes in precipitation structure,it can be seen that extreme precipitation in some parts of Northeast China,most of North China,Fujian-Jiangxi,Sichuan to Yunnan tends to appear in a non-sustainable form,while In the northeast of China,the middle and lower reaches of the Yangtze River,the northwest region and Guangdong-Guangxi,extreme precipitation tends to appear in a sustainable form.(2)From the distribution of precipitation changes in Northwest China,there is a clear trend of wetting in Northwest China,especially in Xinjiang.From the perspective of changes in various types of precipitation in the northwest region,the precipitation in the northwest region may tend to appear in a sustained and extreme form in the future.Non-sustained extreme precipitation in the Northwest Territories,which may be mainly caused by thermal convection or other causes;The dynamic effect of high and low layers is one of the reasons for the continuous extreme precipitation in the northwest region.(3)The precipitation in the Jianghuai River Basin is mainly continuous precipitation,and the proportion of continuous precipitation in each station has reached more than 60%.From the perspective of the change of contribution rate,the contribution of extreme precipitation to total precipitation is mainly increased,and the precipitation in the Jianghuai River Basin may tend to appear more in the form of extreme precipitation in the future.Its unsustainable extreme precipitation is less affected by the high-level dynamic action,On the 500 h Pa level,it is located in front of the high-altitude trough,which is conducive to the upward movement in this area,but the system is relatively shallow and cannot last for a long time,so it appears as non-persistent extreme precipitation.The mutual configuration of high and low layers of continuous extreme precipitation is conducive to the occurrence and maintenance of precipitation in this region,and the dynamic effect of large-scale circulation is one of the reasons for the occurrence of continuous extreme precipitation in this region.(4)The extreme precipitation in Northwest China is affected by the 500 h Pa altitude field,the sea level pressure field and the low-level water vapor transport field.The contribution of dynamic factors favoring circulation control to extreme precipitation changes in Northwest China was not obvious.However,the heat factor under favorable circulation control may be one of the reasons for the increase in persistent extreme precipitation in this region.The two types of extreme precipitation in northwest China are mainly caused by vertical dynamic terms related to upward movement,and the evaporation term and thermal term of both types of precipitation have increased to a certain extent,which confirms that global warming has a certain degree of impact on extreme precipitation in northwest China.(5)The favorable circulation pattern of the Jianghuai River Basin is mainly manifested as EAP type,and the formation of a mid-latitude low trough between the high Okhotsk sea resistance and the western Pacific subtropical high,coupled with the convergence of sea level pressure and low-level water vapor,is conducive to the occurrence of sustained extreme precipitation in this region.For the Jianghuai Basin,the dynamic factor term related to circulation is one of the reasons for the extreme precipitation change,and the thermal factor under the control of favorable circulation is not the main reason for the precipitation change in this area. |
