Variabilidade da radiação solar no Nordeste do Brasil com base em dados observados e do NCEP/NCAR.

Abstract

The main objective this work was to assess the time-series trends of net shortwave radiation (Ras), net longwave radiation (Rn) and Rh from the NCEP/NCAR database. Also, 1t was used to measure annual time series of global solar radiation (Rs) and class A pan evaporation (Epan) for two stations located m the semi-arid region of northeasten Brazil. Long-term variability of NCEP/NCAR Reanalysis and observed data at surface 1s assessed by Mann-Kendall test at p<0.01 and p<0.05 significance levels. The time-series in net radiation, net shortwave radiation and net longwave radiation, based on NCEP/NCAR Reanalysis, showed a reduction through the 1948-1987 period. It was observed inverse pattern from 1988 to 2006 with positive trend for these variables. On decadal analyze for both periods, 1t was observed statically significant trends at 1 and 5% probability level. The analyzed variables presented negative trends, which are statically significant at 1 and 5% probability level by Mann-Kendall test for the whole period of study, mainly on west and lest areas of northeastern region of Brazil. Results also indicate that both global solar radiation and class A pan evaporation at Petrolina, PE and Juazeiro, BA, had an accentuate decrease though study period. The decreasing trends im observed data at surface, as well as the NCEP/NCAR Reanalysis data suggest that the decrease 1n solar radiation mn a large area, which can be attributed to the global dimming effect.