华南地区对流性和大尺度降水特征分析

Characteristics Analysis of Convective Precipitation and Large-scale Precipitation in South China based on ERA5 Data

华南是中国年降水量最多的区域之一。在全球变暖的背景下,降水在区域和尺度上已发生较大的变化,干湿季降水的范围在扩大,华南区域性极端降水事件的影响范围呈显著上升趋势,但不同的降水类型变化及影响并不相同。为进一步了解华南地区不同类型降水在全球变暖背景下如何响应变化,本文基于ERA5再分析降水资料采用线性相关、趋势分析、小波分析等方法研究了1960-2022年华南地区对流性降水和大尺度降水特征。研究表明:(1)华南冬季以大尺度降水为主,其他季节以对流性降水为主。(2)华南对流性降水和大尺度降水在冬季均呈增加趋势,其他季节对流性降水大部分呈减少趋势。冬季华南对流性降水在20世纪80年代至21世纪初存在较为显著的2~4年周期变化;春季对流性降水在20世纪90年代至21世纪初存在由偏多转偏少的年代际特征;在秋季,显著的周期变化主要在20世纪90年代以前。大尺度降水周期变化特征除冬季外,其余季节均与对流性降水较为一致。(3)广东和广西4-10月的总降水主要是对流性降水产生(对流性降水占总降水的65%左右),8月占比最多(广东71.8%,广西69.0%);海南前汛期对流性降水占比(5月最高80%以上)明显高于后汛期,即使进入秋冬季,对流性降水占比依然维持在50%左右。(4)海南对流性降水和大尺度降水的日变化强度最强,广西的对流性降水强度最弱。广东、广西和海南的降水最强时段分别发生在13:00(北京时,下同)-17:00、15:00-17:00和14:00-16:00。大尺度降水广东集中在09:00-17:00;广西地区从04:00开始加强,午后开始减弱,最强时段为10:00前后;海南在8月前最强时段为12:00-17:00,9月下旬后最强时段为15:00-16:00。综上分析可见,不同季节不同类型的降水表现特征并不相同,因此今后降水研究中有必要继续考虑不同类型降水的影响。

South China(SC)is one of the regions with the most annual precipitation in China.Under the background of global warming,there had been significant changes in precipitation at regional and scale levels,the area of dry-and wet-season precipitation was expanding,and regional extreme precipitation events showed a significant upward trend in SC,but the changes and impacts of different types of precipitation were not the same.To better understand how different types of precipitation in SC respond to global warming,this paper investigated the characteristics of convective precipitation(CP)and large-scale precipitation(LSP)in SC based on ERA5 reanalysis precipitation dataset from 1960 to 2022 using linear correlation,trend analysis and wavelet analysis.The results showed that:(1)SC was dominated by LSP in winter while CP in other seasons.(2)CP and LSP in SC showed an increasing trend in winter,but most of CP showed a decreasing trend in other seasons.CP in SC had a relatively significant 2~4 years cycle from the 1980s to the beginning of the 21st century in winter,as well as there was an interdecadal characteristic of shifting from more to less in the 1990s to the beginning of the 21st century in spring,but the significant cyclical variations were mainly found in the period before the 1990s in autumn.In all seasons except winter,the changes in LSP were consistent with CP.(3)The total precipitation(TP)from April to October in Guangdong and Guangxi was mainly CP(CP accounts for about 65%of TP),with the largest proportion in August(71.8%in Guangdong and 69.0%in Guangxi).On the other hand,the proportion of CP in the first rainy season(up to 80%in May)was significantly higher than in the second rainy season in Hainan.Additionally,the proportion of CP remained at about 50%even in autumn and winter.(4)The diurnal variation intensity of CP and LSP was strongest in Hainan while the intensity of CP was the weakest in Guangxi.The peak periods of the strongest precipitation in Guangdong,Guangxi,and Hainan occured respectively from 13:00 to 17:00(Beijing time,the sameas followed),15:00 to 17:00,and 14:00 to 16:00.The LSP peaked between 09:00 and 17:00 in Guangdong,and it started to strengthen from 04:00 and weakened in the afternoon,with the strongest period around 10:00 in Guangxi,for Hainan,the strongest period was 12:00-17:00 before August,but 15:00-16:00 after late September.In conclusion,the characteristics of precipitation varied with different seasons and types.Therefore,it was necessary to continue considering the impact of different types of precipitation in future research.