Observed changes in extreme precipitation over the Tienshan Mountains and associated large-scale climate teleconnections

Abstract

Under global warming, extreme hydrological events are experiencing increasingly violent fluctuations. Investigating changes in the intensity and frequency of extreme precipitation (EP) events is particularly critical for understanding the hydrological response to climate change. Based on high-precision and long-term daily grid precipitation data obtained from Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE), 25 EP indices were examined for the Tienshan Mountains region of Central Asia (TMCA). Here, the relationship between EP and associated large-scale climate teleconnections is revealed by using a series of approaches such as trend analysis and the geographical detector method (GMD), a statistical tool to measure and attribute spatial stratified heterogeneity. The results show an overall increase in EP during 1951–2014, as reflected in the 25 indices. Furthermore, the number of consecutive dry days (CDD) decreased from 87.02 to 69.35 while the number of consecutive wet days (CWD) increased from 3.89 to 4.61. Meanwhile, the increasing trend of total precipitation (PRCPTOT) was 18.43 mm/10a, and changes in EP frequency were shown to increase with event rareness. For R95p, the observed changes in frequency are 34.46%, but these jump to 96.58% for R99p. Moreover, the study also notes that changes in EP are elevation-dependent, with middle altitude areas (1500–3500 m) being most sensitive to change rates. As well, the study reveals that the occurrence of EP responds non-linearly to climatic teleconnections, and that the combined effect of two factors generally make much larger contributions to EP than the summation of individual factors. Further analyses indicate strong zonal circulation at 500 hPa, 1000 hPa potential height increases airflow from west to east. And the weakening of the East Asian Summer Monsoon accompanied by the westward extension of the western Pacific subtropical high and the increase in Mongolian anticyclone activity all bring sufficient exogenous water vapor from the North Atlantic and Indian Ocean to the TMCA.