Diurnal Rainfall Variation in Northeast Brazil

Abstract

The diurnal rainfall variation in northeast Brazil is investigated for the period 1961?70. Most coastal areas are found to experience a nocturnal maximum in rainfall activity. probably due to convergence between the mean onshore flow and the offshore land breeze. Areas 100?300 km inland experience a daytime maximum, associated with the development and inland advance of the sea breeze. The diurnal rainfall variability, at most interior locations, seems to be, due to mountain-valley breezes. Seasonal variations am noted for areas of the north coast of Brazil. Soure, located near the mouth of the Amazon River, experiences a nocturnal maximum between January and May, and an afternoon maximum between June and September. Evidence is presented which shows that this seasonal variation is linked to the seasonal variation in the low-level mean now. Seasonal variations in the mew monthly rainfall for eastern coastal areas am shown to correlate well with the intensity of the land breeze, which is represented by the difference between the mean sea surface temperature and the mean air temperature over land.