Projected changes in extreme snowfall events over the Tibetan Plateau based on a set of RCM simulations

Extreme snowfall events over the Tibetan Plateau (TP) cause considerable damage to local society and natural ecosystems. In this study, the authors investigate the projected changes in such events over the TP and its surrounding areas based on an ensemble of a set of 21st century climate change projections using a regional climate model, RegCM4. The model is driven by five CMIP5 global climate models at a grid spacing of 25 km, under the RCP4.5 and RCP8.5 pathways. Four modified ETCCDI extreme indices—namely, SNOWTOT, S1mm, S10mm, and Sx5day—are employed to characterize the extreme snowfall events. RegCM4 generally reproduces the spatial distribution of the indices over the region, although with a tendency of overestimation. For the projected changes, a general decrease in SNOWTOT is found over most of the TP, with greater magnitude and better cross-simulation agreement over the eastern part. All the simulations project an overall decrease in S1mm, ranging from a 25% decrease in the west and to a 50% decrease in the east of the TP. Both S10mm and Sx5day are projected to decrease over the eastern part and increase over the central and western parts of the TP. Notably, S10mm shows a marked increase (more than double) with high cross-simulation agreement over the central TP. Significant increases in all four indices are found over the Tarim and Qaidam basins, and northwestern China north of the TP. The projected changes show topographic dependence over the TP in the latitudinal direction, and tend to decrease/increase in low-/high-altitude areas.

摘要

基于RegCM4区域气候模式的气候变化预估试验数据, 开展了青藏高原及其周边地区极端降雪事件的未来变化研究. 结果表明, 总降雪量在高原大部分地区呈减少趋势, 降雪日数在高原也将明显减少, 尤其是在东部. 大雪日数和五日最大降雪量在高原东部将减少, 而在中部和西部明显增加. 在高原周边的塔里木和柴达木盆地及中国西北地区, 极端降雪事件同样增加显著. 极端降雪事件在高原上呈现出东西方向上的地形依赖性, 在低/高海拔地区呈减少/增加趋势.