Tendência de índices climáticos de temperatura do ar e precipitação para o Estado do Rio Grande do Sul

Abstract

The present work had as the aim the analysis of trends of climate indices obtained from series of interpolated and observed daily data of rainfall and average air temperature, from 1980 to 2013, for the State of Rio Grande do Sul. Eleven indices of precipitation and fourteen indices of air temperature were evaluated. The evaluation of trends was performed through the application of the methodologies of Mann-Kendall (Mann, 1945; Kendall, 1975) and Sen’s Slope (1968). Between the indices of precipitation determined, for the indices R10mm, R20mm, CDD and PRCPTOT significant trends were not identified, while for CWD, Rx1Day, RX5Day, R50mm, R95p and SDII significant trends were identified in a reduced number of stations. With respect to air temperature, the indices SU25, DTR, FD0, TNMed, TXMed, TN10p, TN90p, TNn, TNx, TR20, TX10p, TX90p, TXn and TXx were determined. Significant trends were obtained for all the indices studied. The results obtained indicate a different behavior on the Central portion and Southwest and Northwest regions of the State. In this region, a trend of increase was observed for SU25 and TR20, which indicate the number of days with maximum temperatures above 25ºC and the number of days with minimum temperature above 20ºC, respectively, increase of TX90p and TN90p, percentiles that represent hot days and nights, besides the increase of the average annual maximum temperature, TXMed. Increases were also identified for the highest annual maximum temperature, TXx, and the highest annual minimum temperature, TNx, while for the same region, TNn, the lowest annual minimum temperature, presented a trend of decrease. For the other indices, trends of increase and decrease were obtained, with distinct distribution on the rest of the surveyed area.