Assessment of gridded precipitation and air temperature products for the State of Acre, southwestern Amazonia, Brazil

This paper evaluated the precision and accuracy of two gridded monthly precipitation products (P-GPCC/V6 from the Global Precipitation Climatology Centre and P-UDEL/V3.01 from the University of Delaware—UDEL) and two monthly air temperature products (T-GHCN/V2 from the Global Historical Climatology Network and T-UDEL/V3.01 from UDEL) for the State of Acre, in southwestern Amazonia, northern Brazil. As reference, we used monthly climate series of these elements from January 1971 to December 2000, recorded at five conventional weather stations (CWS) of the Instituto Nacional de Meteorologia (INMET). Data were compared by linear regression; the coefficient of determination (r²); Willmott's index of agreement (d); Camargo's performance index (c); the root-mean-square error (RMSE); mean systematic error (MSE); and unsystematic error (MSE_u). Moreover, a trend analysis of the products at a seasonal and annual scale was performed. Regarding rainfall, it was found that GPCC as well as UDEL represents the mean and variability of rainfall throughout the series, but the performance of the product of GPCC was more homogenous and generally applicable for all stations. In relation to the air temperature standards, the precision of GHCN and UDEL was low, but the accuracy was moderate, according to statistical methods.