The basic characteristics of cloud water, precipitation, and the dependence of precipitation efficiency (PE) on the influencing factors over the Tibetan Plateau (TP) are investigated. Results found that the liquid water path shows a significant downward trend in winter over the TP, and the ice water path shows a significant upward trend in the pre-monsoon and winter seasons and a significant downward trend in the monsoon season in the western TP from 1998 to 2015. In the eastern TP, the precipitation in the monsoon season also shows a significant downward trend, which may be related to the weakening of the South Asian monsoon. Results have determined that precipitation depends more on the ice water cloud than on the liquid water cloud over the TP. Moreover, the convective available potential energy (CAPE) and the low-tropospheric relative humidity (RH) are two environmental factors that have a prominent influence on the PE. During the monsoon season, higher CAPE and RH were conducive to a larger PE over the TP. The results suggest that the CAPE has a positive effect on the PE, which means that the PE is directly dependent on the convective precipitation, mainly due to the frequent convective activity and dominant convective precipitation over the TP.

中文翻译：

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青藏高原云降水效率及其影响因素

研究了青藏高原（TP）上空云水、降水的基本特征以及降水效率（PE）对影响因素的依赖性。结果发现，青藏高原冬季液态水路径呈明显下降趋势，青藏高原西部前季风和冬季冰水路径呈明显上升趋势，季风季节呈明显下降趋势。 1998～2015年，青藏高原东部季风季降水也呈现明显下降趋势，可能与南亚季风减弱有关。结果已经确定降水更多地取决于冰水云而不是青藏高原上的液态水云。而且，对流有效势能 (CAPE) 和低对流层相对湿度 (RH) 是对 PE 有显着影响的两个环境因素。在季风季节，较高的 CAPE 和 RH 有利于比 TP 更大的 PE。结果表明，CAPE对PE具有正向影响，即PE直接依赖于对流降水，主要是由于青藏高原上空频繁的对流活动和主导的对流降水。