Temporal and Spatial Distribution Characteristics of Lightning Activity over the Pacific Ocean and Adjacent Land and Its Relationship with AOD and CAPE

Based on LIS/OTD gridded lightning climatology data,ERA5 reanalysis data,and MODIS atmosphere monthly global products,we examined latitudinal and daily variations of lightning activity over land,offshore areas,open sea,and all marine areas(i.e.,the aggregate of open sea and offshore areas)for different seasons over the Pacific Ocean and the adjacent land areas at 65°N-50°S,99°E-78°W,and analysed the relationships of lightning activity with CAPE(Convective Available Potential Energy)and AOD(Aerosol Optical Depth).At any given latitude,the lightning density is the highest over land,followed by offshore areas,all marine areas and the open sea in sequence.The lightning density over land is approximately an order of magnitude greater than that over all marine areas.Lightning activity over land,offshore areas,open sea,and all marine areas varies with season.The diurnal variation of lightning density over land has a single-peak pattern.Over the offshore area,open sea,and all marine areas,lightning densities have two maxima per day.The magnitude of the daily variation in mean lightning density is the largest over land and the smallest over the open sea.The lightning density over the Pacific Ocean and adjacent land areas is significantly and positively correlated with CAPE.The correlation is the strongest over land and the weakest over the open sea.Cloud Base Height(CBH)may affect the efficiency of CAPE conversion to updraft.CAPE has a positive effect on lightning activity and has a greater impact on land than on the ocean.Over the sea,both CAPE and AOD can contribute to lightning activity,but the magnitudes of the influence of CAPE and AOD on lightning activity remain to be determined.Lightning activity over land and sea is a result of the combined action of AOD and CAPE.