Integrated warm-wet trends over the Tibetan Plateau in recent decades

The integrated warm-wet trends over the Tibetan Plateau (TP) have posed a vital influence on human society and natural ecosystem in recent decades. However, there is currently a lack of in-depth research on the trends over the TP. In this study, CN05.1 high-resolution grid data and ERA5 reanalysis data were analyzed to explore temporal and spatial changes of the integrated warm-wet trends over the TP during 1961-2020 based on temperature, precipitation and the new defined Warm-Wet index (WWI). The results are shown as follow: (1) Temporally, annual surface mean temperature (0.34°C per decade), precipitation (0.73% per decade), latent heat flux (0.08W·m^-2 per decade), and sensible heat flux (0.19W·m^-2 per decade) have overall increased over the TP. Further, defined by the above climate variables, WWI has increased in the most regions from 1960s to 1980s, then the variations have become relatively mild in the following two decades. (2) Spatially, WWI has finally formed a pattern of significant increase in the semi-humid region and eastern semi-arid region and significant decrease in the humid region, which is similar to precipitation. Noticeably, arid region, semi-arid region, and semi-humid region have all experienced significant increase of WWI but humid regions have experienced decrease. That is, the relatively dry regions over the TP have become warmer-wetter but the relatively wet regions have become warmer-drier. (3) In addition, seasonal asymmetric has been revealed, and winter has experienced the most significant warming-wetting in spite of the smallest values of temperature and precipitation in climatology. (4) Finally, among all independent variables, precipitation contributes the most to the variations of WWI over the entire TP, while temperature is crucial in the arid region and surface heat flux plays an important role in the humid region. Our findings may provide additional insights regarding the risk evaluation over the TP, and the proposed framework to evaluate the trends over different climate zones could also offer a meaningful guide to other regions.