The Diurnal Variability of Florida Rainfall

Abstract

The diurnal variation of precipitation over the Florida peninsula is investigated on the basis of harmonic analysis of hourly rainfall data. Hourly data on the frequency of three categories of precipitation events for around 70 stations in Florida were processed, generating statistics of amplitude and phase of the diurnal precipitation cycle at each station. Results are shown for all stations for the seasonal totals and for a selected cross section of stations for the detailed monthly totals. During the winter months a small morning maximum occurs in the northwest shifting abruptly to early afternoon across the northern panhandle. Most of the state during the remainder of the year depicts afternoon maxima. Interesting exceptions occur in the northwest and the Keys. The amplitude of the afternoon maximum decreases toward coastal areas suggesting that nocturnal rainfall decreases the relative importance of the afternoon maximum at these locations. It is suggested that the character of the harmonic analysis for individual locations is related to probable effects of the location of the sea breeze convergence zone and the influence of extratropical disturbances such as quasi-stationary fronts. The large-scale flow is decisive to the timing and onset of precipitation, a fact that emerges even in the absence of wind stratification of the data. Most locations throughout the state do not show any significant semi-diurnal character in their data and results for the diurnal precipitation cycle remain relatively consistent through all categories of precipitation.