Avaliação da precipitação estimada pelo satélite GPM para a bacia hidrográfica do rio Sapucaí

Abstract

In Brazil, the number of rainfall stations on the surface is still low and is not enough to represent the spatio-temporal variability of rainfall throughout the territory. Therefore, a good option to overcome this lack of data is the use of satellite precipitation estimates. Therefore, this study aimed to validate, through statistical methods, the daily precipitation estimated by the Global Precipitation Measurement (GPM) satellite for the Sapucaí River Basin, using four methodologies: point by pixel - original data, without going through no processing; pixel to point – debiased satellite data; pixel by pixel – interpolated station data; average in the area – average in the sub-areas of Alto, Medio and Baixo Sapucaí. The data used in the validation came from rainfall stations of the National Agency for Water and Basic Sanitation (ANA). The results found for the point to-pixel methodology for the complete series, summer and winter, indicated the existence of a moderate average correlation, with errors varying from magnitude of 3 to 10 mm day-1 and with an average tendency to overestimate the GPM in in relation to ANA data. The same occurred for the pixel-to-point method, where the results were very similar, in addition, a correction in the precipitation frequency was observed through this methodology. The pixel-by-pixel method presented higher statistical results, compared to the previous ones, and even increased the surface data coverage. However, the averaging methodology in the area was the one that obtained the best results: high correlation, coefficient of determination above 60% and lower magnitude of errors. Overall, in both cases the GPM showed an average tendency to overestimate the ANA data, but it proved to be viable for use in studies, mainly as a way to meet the need for data in places without records.