Changes in rainfall patterns due to the growth of an urban area

Abstract

The changes in rainfall patterns, which evolve during the growth in size of a tropical urban area, are studied by means of model simulations. The urban area is located along a coastline. The simulated rainfall is produced by mesoscale disturbances during the rainy season when the prevailing wind is weak and when the sky is not cloudy. These disturbances are generated by differential heating associated with differences in the thermal properties of the sea, urban and rural surfaces. Simulations of the rainfall during a 24-hour period are made for different sizes of the urban area corresponding to different stages in the growth of urban area. One of the simulations corresponds to a condition before the beginning of the urbanization (urban area is zero).
The results of the simulations indicate that the increase in the urban size produces changes in the rainfall amount, as well as the timing and the location of rainfall occurrence. For relatively small urban areas, the total accumulated rainfall remains approximately the same for different sizes of the urban area. The corresponding total for large urban areas is greater due to the fact that the rainfall bands are wider. With regard to the time of occurrence, urbanization results in an earlier occurrence of rain; it also results in an earlier ending. In regard to the location, rainfall occurs farther from the coast as the urban size increases.