Spatial patterns of diurnal lightning activity in southern Africa during austral summer

摘要

In the present study we used harmonic analysis to investigate the spatial distribution of diurnal patterns of hourly lightning flash activity during the months of January and February from 1998 to 2013 in southern Africa. The data were obtained from the Tropical Rainfall Measuring Mission dataset collected through a lightning imaging sensor. The spatial distribution of lightning activity during the austral summer season was mostly concentrated over land, with the highest total lightning activity observed over the Congo and Zambezi river basins. The strength of the diurnal cycle was mainly determined by the presence of warm and cold ocean currents along the coastal areas, and the presence of the St Helena high pressure cell, along with local level processes including land sea breeze convergence, local topography, and surface heating processes. The strength of the diurnal cycle was relatively weaker in the interior of the study area across the Kalahari Desert and Democratic Republic of Congo. The peak lightning activity across most of the study area occurred in the afternoon hours, while a nocturnal peak was observed in the case of the limited maritime activity in the Atlantic Ocean.