Temporal And Spatial Distribution Characteristics Of Nighttime Precipitation In China And Its Influence On Air Quality

Nocturnal rainfall is a special kind of rainfall phenomenon,and the specific causes are related to the climatic factors such as monsoon and mesoscale convective system,as well as the geographical environment such as terrain.The research on nocturnal rainfall in the domestic and overseas focuses on the analysis of the temporal and spatial characteristics of rainfall in typical night rain areas and the impact of mesoscale convective systems on the causes of night rain.Few studies have analyzed the characteristics of different night rain phenomena at the national level and explored the differences.In order to learn the connection and difference of the night rain phenomenon,this study is of great significance to master and analyze the night rain resources in China.Because of its unique time of occurrence and formation mechanism,the interaction of night rain with environmental factors shows different characteristics from total daily rainfall or daytime rainfall.This article takes the rain cloud removal process as an entry point,explores the impact of nocturnal rainfall on air quality,and provides new ideas and methods for our future air pollution control.Based on the meteorological observation data from 1959-2018 and the atmospheric pollution observation data from 2014-2018,this paper studies the temporal and spatial distribution characteristics of night rainfall in China from a national scale,compares the temporal and spatial distribution characteristics of night rain in different regions,and explores the night rain in different regions.The connection and difference of the phenomena try to explain the regional characteristics of the cause of night rain;by studying the characteristics of the time change of night rain in China,the time evolution of night rain resources is clarified,and the specific reasons for the spatial and temporal changes of night rain are explored in combination with spatial analysis.The effect of night rain on the removal of under-clouds is analyzed.By studying the effect of night rain on the removal of atmospheric particulate matter(PM2.5,PM10),it attempts to evaluate the effect of night rain on the removal of atmospheric particulate matter,providing new ideas for our future air pollution control.And methods.The specific conclusions and recommendations of this article are as follows:(1)China's areas with abundant night rain resources are widely distributed throughout the country,but there are areas where night rain is concentrated within the night rain area;(2)Sichuan Basin,Yunnan-Guizhou Plateau and Qinghai-Tibet Plateau,etc.The main difference between a typical night rain area and atypical night rain such as the Pearl River Delta is the daily variation of precipitation.The precipitation in the night rain area shows a single peak and single valley distribution on a single day.The peak occurs at night instead of the typical night rain area.The night rain showed a distribution of double peaks and single valleys on a single day,and the peak appeared in the morning and afternoon;(3)The typical night rain area showed a slight decrease in the total amount of night rain on the time scale,and the distribution of night rain became more and more even throughout the year.Rain is happening more and more,and it has a single-peak elevation effect.There is an optimal altitude corresponding to the highest night rain rate;(4)Nocturnal rain has a good ability to remove atmospheric particles,especially for larger-sized particles,and with the increase of night rain intensity,the rainfall time increases,and the removal effect is better;(5)Nocturnal rain removes atmospheric particles.There is a minimum removal rainfall and a significant hysteresis effect in the removal effect.The minimum removal rainfall and lag days in each city are different due to different environmental factors.All in all,this study basically understands the spatiotemporal distribution characteristics of nocturnal rainfall in China,and proves the superiority of nocturnal rainfall to remove atmospheric particulate matter,analyzes the threshold and hysteresis of nocturnal rainfall to remove atmospheric particulate matter quantitatively,and lays a foundation for further research on nocturnal rainfall.