Temporal And Spatial Distribution Of Lightning And Its Correlation With Nitrogen Dioxide Concentration In Guangdong Province

In order to understand and grasp the law of climate change and related parameters of lightning in Guangdong,one of the sources of natural disasters,temporal and spatial distribution of lightning in Guangdong Province from 2007 to 2016 was analyzed deeply by using spatial overlay and geostatistical analysis of Arc GIS.Combining the spatial and temporal distribution of precipitation and its causes in Guangdong Province,the influence of precipitation on lightning and the relationship between them were studied.Based on the topography and urban development,the physical environment characteristics of lightning in Guangdong were systematically analyzed.The purpose was to explore the causes and power sources of the differences and commonalities in the spatial and temporal distribution of lightning in Guangdong.Using the atmospheric nitrogen dioxide concentration data from Environmental Control Station to analyze the spatial and temporal distribution characteristics of nitrogen dioxide in Guangdong from 2014 to 2017.In addition,the correlation analysis method was used to research the influence of lightning on the concentration of nitrogen dioxide by selecting a major weather event before the rainy season,which could provide a reference for the prediction and evaluation of nitrogen dioxide pollution.The main research results are as follows.(1)The lightning of Guangdong Province had certain regularity in temporal distribution,with obvious characteristics of inter-annual distribution,monthly distribution and daily distribution.In recent ten years,the cloud-to-ground lightning density in Guangdong had been increasing gradually.Lightning activities were mainly concentrated in summer and autumn,from April to September,whose lightning frequency accounted for 97.48%of the annual lightning.The daily distribution of lightning activity was characterized by single peak,which was concentrated from afternoon to evening.From 13:00 to 21:00,the lightning frequency accounted for more than 70%of the whole day's lightning,and the peak appeared at 17:00.The lightning of Guangdong Province had certain regularity in spatial distribution.Lightning active area was mainly located in the Pearl River Delta,and gradually decreased from the center to the outside.The average lightning density of eight prefecture-level cities in Guangdong was higher than that of the whole province in recent ten years.Among them,the lightning density in Guangzhou was the highest.The lightning centroid was basically located in the Pearl River Delta,mainly in Guangzhou.(2)The lightning of Guangdong Province was greatly affected by precipitation,topography and urban development level of underlying surface.In recent ten years,the average precipitation in Guangdong was about 1826.4 mm.The precipitation from April to September accounted for more than 3/4 of the annual precipitation.These months were also the high-risk months of lightning.There was a good spatial consistency between the high rainfall area and the high cloud-to-ground lightning density area located inside the mainland.The terrain of the Pearl River Delta was flat,surrounded by mountains on three sides and facing the sea in the south.The trumpet-like terrain was conducive to the rise of ocean water vapor,and frontal thunderstorms were prone to occur when cold air came.It was the most active area of lightning.Due to the special sea-land distribution and the influence of the northern mountains,there was also a sub-high value area of lightning activity in Leizhou Peninsula.The Pearl River Delta region with a high level of economic development in Guangdong Province was a region with high cloud-to-ground lightning density,and it was also the region where lightning centroid of Guangdong Province was located in the past ten years.(3)The temporal and spatial distribution of nitrogen dioxide concentration in Guangdong Province had regularity.The concentration of nitrogen dioxide in Guangdong Province has a "U" structure in temporal distribution.Its changing trend was to lower first and then increase.Nitrogen dioxide concentration was highest in January and December,while the lowest concentration appeared in June.In spatial distribution,the high value area of nitrogen dioxide concentration was mainly located in the central Pearl River Delta region,at the junction of Foshan and Guangzhou.In general,the concentration of nitrogen dioxide varied from high to low from the central region to the periphery.(4)In order to study the influence of lightning on the concentration of nitrogen dioxide,a large-scale squall line process affecting the province in April 2016 was selected as an example to compare and correlate lightning and nitrogen dioxide data from time and space scales.The results showed that the trend of lightning frequency and nitrogen dioxide concentration was the same during the weather process,showing a straight upward trend.There was a lead-lag correlation between lightning and the concentration of nitrogen dioxide.The nitrogen dioxide concentration peaked 16 hours after the peak of lightning.At a confidence level of 0.99,the correlation between the two data was significant.The research results could provide a basis for accurate prediction and evaluation of atmospheric environmental quality.(5)The spatial distribution of nitrogen dioxide in Guangdong Province was the result of the combination of meteorological conditions and underlying surface pollution sources.The concentration of nitrogen dioxide could be controlled by exerting the role of natural environment of atmosphere,reducing the concentration of nitrogen dioxide by artificial precipitation,combining climatic conditions in reasonable regional planning,and controlling human's emission sources of nitrogen dioxide.