EFFECT OF LAND USE/ LAND COVERS CHANGE ON RADAR REFLECTIVITY BASED CONVECTIVE PRECIPITATION IN SOUTH FLORIDA

Development of urban heat island and increase of sensible heat flux above the urban center could spatially shift and diurnally accelerate sea breeze convergence thereby altering convective precipitation in south Florida. This study investigates the effect of land use /land cover change on warm season convective rainfall by using radar reflectivity in south Florida for the first time. Weather Surveillance Radar (WSR-88D) expresses its backscattered energy in terms of decibels of reflectivity (dBZ), which estimates the size of the hydrometeor target and can be used to separate convective rainfall from stratiform type.

Frequency and magnitudes of seventeen years (1996-2012) of high resolution radar reflectivity data from Miami station (KAMX) for three afternoon hours of summer months: June, July, and August are analyzed. Reflectivity values≥40 dBZ are selected, because 40 dBZ is considered as the most common reflectivity threshold for convective rain. Synoptically active weather days are removed from the analysis so that any change in thunderstorms pattern through time and space reflects only the effects of surface induced convection. Land use/ land cover change of south Florida during the same temporal range as of radar data and a comparative analysis thereafter indicates that medium and high intensity developed urban covers tend to enhance the convective activity, hence increasing the frequency and intensity of thunderstorms.