Quantifying the Contribution of Recycled Moisture to Precipitation in Temperate Glacier Region, Southeastern Tibetan Plateau, China

Abstract

Recycled moisture is an important indicator of the renewal capacity of regional water resources. Due to the existence of Yulong Snow Mountain, Lijiang in Yunnan Province, southeast of the Qinghai-Tibet Plateau, China, is the closest ocean glacier area to the equator in Eurasia. Daily precipitation samples were collected from 2017 to 2018 in Lijiang to quantify the effect of sub-cloud evaporation and recycled moisture on precipitation combined with the d-excess model during monsoon and non-monsoon periods. The results indicated that the d-excess values of precipitation fluctuated between −35.6‰ and 16.0‰, with an arithmetic mean of 3.5‰. The local meteoric water line (LMWL) was δD = 7.91δ¹⁸O + 2.50, with a slope slightly lower than the global meteoric water line (GMWL). Sub-cloud evaporation was higher during the non-monsoon season than during the monsoon season. It tended to peak in March and was primarily influenced by the relative humidity. The source of the water vapour affected the proportion of recycled moisture. According to the results of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the main sources of water vapour in Lijiang area during the monsoon period were the southwest and southeast monsoons. During the non-monsoon period, water vapour was transported by a southwesterly flow. The recycled moisture in Lijiang area between March and October 2017 was 10.62%. Large variations were observed between the monsoon and non-monsoon seasons, with values of 5.48% and 25.65%, respectively. These differences were primarily attributed to variations in the advection of water vapour. The recycled moisture has played a supplementary role in the precipitation of Lijiang area