Changes in extreme precipitation in Texas

An increase in global temperature leads to the intensification of a hydrologic cycle, which, in turn, affects spatiotemporal characteristics of precipitation. The distribution of precipitation plays an important role in water resources planning at regional and local scales. In this study, the state of Texas was used as a study area. Five kinds of annual precipitation extremes, based on the annual maximum (1, 7, and 30 days) and on the threshold level (95th and 97.5 percentiles), were analyzed. Applying the extreme value theory, a generalized extreme value distribution was fitted to these extremes, and quantiles were calculated for the preclimatic change period (1925-1964) and the postclimatic change period (1965-2005) to understand the possible changes in frequency patterns in terms of both spatial and temporal scales. Furthermore, the trend analysis of extreme precipitation was performed using the Mann-Kendall test for preclimatic and postclimatic change periods to determine possible increasing or decreasing patterns. On the basis of the quantiles obtained for different return periods using 1 day extreme precipitation on an annual scale, mixed results were observed. The stations with higher quantiles, based on 1 day extreme events during the preclimatic period, were located mostly in the subtropical subhumid regions, whereas those during the postclimatic change period were located in most of the climatic zones. Similarly, results based on other extreme variables showed that the changes in the temporal and spatial characteristics of quantiles as well as increasing or decreasing patterns were observed at different locations during preclimatic and postclimatic change periods.