2018 Volume 96A Pages 67-76
Does the presence of cities enhance precipitation? It is an issue that needs to be addressed. This study focuses on the thermal excess in cities and attempts to determine the influence of this parameter on atmospheric instability, which constitutes the background condition for convective precipitation. A simple analytical approach involving the calculation of the daytime evolution of the mixed layer over a homogeneous ground surface was developed. The calculations were based on the data from the ensemble average of observations. Using these calculations, the convective available potential energy (CAPE) was obtained for two idealized geographic areas: one with urban land cover and the other with rural land cover. Urban heat excess, which was 200 W m−2 greater than rural area, increased CAPE value by 75 % comparing to the rural CAPE value of 513 J kg−1. Cities can produce stratification in the atmosphere that is favorable for convective precipitation.