张杰教授团队在亚洲干旱区降水和极端降水影响因子研究方面取得新进展，相关成果发表在Journal of Climate期刊。
亚洲干旱区降水和极端降水呈现增加趋势，尤其是在中亚65˚E以东地区。影响极端降水增加的可能物理机制：1）欧亚大陆上空50˚N附近准定常波列振幅增加，导致巴尔喀什湖附近长波槽加深，促进高纬巴伦支海和喀拉海地区的水汽和西南暖湿水汽向中亚东部输送并在槽前辐合上升；2）NAO (North Atlantic Oscillation, NAO)和EA/WR (East Atlantic/Western Russia, EA/WR)负位相年代际加强是影响上述准定常波列异常的关键环流因子；3）欧亚大陆上空两组天气尺度的瞬变波通过增加准定常波列振幅、中亚东部地区的瞬变涡旋和瞬变扰动动能，加强中亚东部气旋异常，加深巴尔喀什湖长波槽，促进中亚南部暖湿水汽和天气尺度瞬变涡沿槽前西南气流向中亚东部输送；4）异常环流促进天山地区极端降水发生，天山地形抬升激发更多的天气尺度瞬变涡，并沿着巴尔喀什湖槽继续向北输送影响哈萨克斯坦东北部极端降水增加；5）另外，春末青藏高原西部积雪减少，导致夏季土壤湿度降低，非绝热加热增加以及纬向温度梯度减小，有利于南亚高压和亚非急流向北延伸，促使偏南水汽向北输送，增强极端降水发生。
Figure 1. Schematic diagram to illustrate the physical processes associated with the increased extreme precipitation in ECA. When extreme precipitation increases, the increased SST in the high-latitude North Atlantic modified the quasi-stationary wave train, guided the cyclonic anomaly in CA, deepened the Lake Balkhash trough, enhanced the anticyclonic anomaly in western Eurasia, and advected moisture southward. Two synoptic transient wave trains strengthen the amplitude of the quasi-stationary waves and guide transient eddies in eastern CA. The induced transient eddy and deepened Lake Balkhash trough strengthened positive meridional vorticity advection and local positive vorticity was strengthened by the terrain of the Tianshan, which promoted ascending motions, guiding the southerly warm moisture and further increasing extreme precipitation in ECA.
Figure 2. Schematic diagram summarizing two physical processes for the TP glacier/snow cover (TP/SC): 1) the effect on the meridional water vapor flux (Qv) through the meridional wind V and subtropical jet stream (JS) and the zonal temperature gradient dT, and 2) the effect on the wave trough/ridge through the TP mode of the South Asian high (TP-SAH), due to increasing diabatic heating (HF) and the contribution to precipitation P in the Asian drylands.
论文信息：
[1] Zhang, J., Ma, Q., Chen, H., et al., 2021. Increasing warm-season precipitation in Asian drylands and response to reducing spring snow cover over the Tibetan Plateau. Journal of Climate, 34,3129-3144.
[2] Ma, Q., Zhang, J., Ma, Y., et al., 2021. How Do Multiscale Interactions Affect Extreme Precipitation in Eastern Central Asia?.Journal of Climate, 34,7475-7491.
