DIURNAL-VARIATIONS IN ARIZONA MONSOON LIGHTNING DATA

Lightning flash data for Arizona from the Bureau of Land Management's magnetic detection finder network are analyzed for the 1989 and 1990 summer monsoon seasons. Results from harmonic analysis reveal a strong diurnal cycle in the frequency of lightning flashes. In much of the state, the time of maximum occurs in the mid-to-late afternoon period. However, in the large valley of central Arizona, the time of maximum lightning frequency is closer to midnight. These results from the emerging lightning flash database should be useful in (a) further evaluating the role of various mechanisms responsible for the nocturnal convective regime of central Arizona, (b) verifying existing and future numerical models of precipitation processes in the region, and (c) preparing and evaluating forecasts of summertime convective events in Arizona.