Contribution of Recycled Moisture to Precipitation: A Modified D‐Excess‐Based Model

Defining moisture sources and evolution of precipitation is of significance for further exploration of complex hydro‐climatic interactions, especially under global warming with alternations of evapotranspiration capacity and precipitation moisture source structure. As a sensitive indicator, d‐excess has been widely used to quantify the proportion of recycled vapor to precipitation (fre). However, existing d‐excess‐based models ignore to take transpiration vapor into account and the calculated fre tends to be lower than the true value, thus underestimating the importance of recycled vapor in precipitation. Herein, the existing model was modified with transpiration vapor considered and applied in Guyuan, China located in a monsoon marginal zone with complex precipitation moisture sources. After modification, the estimated annual average fre was increased from 7.5% to 14.8%, well calibrating the existing model. This study highlights the contribution of transpiration vapor to precipitation and provides more information on the formation and evolution of precipitation to better serve future hydro‐climatic research. Plain Language Summary In the context of global warming, remarkable changes have occurred in the evapotranspiration capacity and precipitation, which inevitably caused a series of alternations to the hydrological and atmospheric cycles. Defining the moisture sources of precipitation and its evolution in the atmosphere is of great significance for further exploration of complex interactions between hydrology and climate change. Recently, increasing studies have emphasized the importance of recycled vapor derived from local evapotranspiration to precipitation. As a sensitive indicator, d‐excess has been widely used to quantify the proportion of recycled vapor in precipitation (or called the recycling ratio). However, existing d‐excess‐based models for determining the recycling ratio ignore to take the transpiration vapor into account, and the calculated ratio tends to be lower than the true value, thus underestimating the important role of recycled vapor in precipitation. In this study, the existing model was modified by considering the contribution of transpiration vapor and applied well in Guyuan, China located in a monsoon marginal zone with complex precipitation moisture sources. This study highlights the importance of the transpiration vapor contribution to local precipitation and provides more information on the formation and evolution of precipit