Recent intensification of short-term concurrent hot and dry extremes over the Pearl River basin, China

Ongoing climate warming is largely affecting the frequency and magnitude of short-term climatic extremes in many regions of the world, causing significant damage to the environment and society. Here, based on the long-term (1980-2010) meteorological observations and reanalysis products, we investigated the spatio-temporal evolutions of short-term concurrent hot and dry extreme (SCHDE) events over the Pearl River basin, a typical humid and subtropical basin in southern China. We also explored the physical mechanisms of SCHDE and its relationship with a series of hydrometeorological variables and large-scale climate indices. The results indicate an intensification of SCHDE over the study basin during the study period, especially for the period 1997-2010. SCHDE occurs mostly in the northeastern and western regions and shows a statistically significant increasing trend mainly in the midwestern and southeast regions, which is mainly associated with an increased temperature (T-air), drying trend in soil moisture (SM), and a sharp increasing trend in evapotranspiration (ET). The contribution of T-air variability to the SCHDE variability is largest (57.27%), followed by SM (28.43%) and ET (14.30%). In addition to T-air, SM deficit before the onset also plays an important role in the SCHDE occurrence. Furthermore, the SCHDE variability tends to be more sensitive to the SM deficits in the high-altitude areas than in the low-altitude areas. Besides, wavelet transform analysis results indicate that the cold phase of ENSO tends to trigger a higher risk of SCHDE events, while El Nino Modoki events have different influences on the variations of SCHDE during different warm/cold phases over the Pearl River basin.