Abstract
(1) Background: The degree to which local precipitation is supplied by recycled moisture is a reflection of land surface–atmosphere interactions and a potentially significant climate feedback mechanism. This study tries to figure out the water cycle and precipitation mechanism at a mountainous region and then provides a reference for similar mountainous regions outside China. (2) Methods: The dual-isotopes and Bayes-based program MixSIAR is used to assess contributions of advected, transpirated and evaporated vapor to local precipitation. (3) Results: The average percent contribution of recycled moisture (i.e., the sum of surface evaporated vapor and transpirated vapor) to local precipitation at the Qilian Mountains during 2017 plant growing season is about 37% (the upper quartile and the lower quartile was 30% and 43%, respectively). (4) Conclusions: Although the contribution of advection vapor dominated during the plant growing season, the contribution of recycled moisture is also important in such an alpine region. Furthermore, the commonly used simple linear mixing models often yield contributions greater than 100% or less than 0% and are likely to underestimate the contribution of recycled moisture to local precipitation. Although the alternative Bayesian model is not perfect, either, it is still a big improvement.
Highlights
Precipitation over a terrestrial region is usually considered to be derived from three main sources, i.e., water vapor advected into the region by air mass motion and water vapor supplied by surface evaporation and vegetation transpiration from the land surface of the region
It can be seen that the local precipitation during the growing season in the Qilian Mountains was mainly supplied by advected water vapor
The Bayesian model was first used to calculate the contribution of different water vapor to local precipitation
Summary
Precipitation over a terrestrial region is usually considered to be derived from three main sources, i.e., water vapor advected into the region by air mass motion and water vapor supplied by surface evaporation and vegetation transpiration from the land surface of the region. The recycled moisture or recycled precipitation is defined as water vapor that is produced by surface evaporation and vegetation transpiration within a region and falls again as precipitation within the same region [1,2,3]. The relative contribution of recycled moisture to total precipitation, called the recycling ratio, provides a potentially diagnostic measurement that describes land surface processes and land surface–atmosphere interactions and is of great significance in the study of hydrological cycle. Recycled moisture by evapotranspiration is probably the most important mechanism sustaining rainfall for continental catchments, in semiarid areas [7]
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