Quantifying the contribution of oceanic evaporation to tropical cyclone development with WRF-age 

Global warming is accelerating the global water cycle. On a short temporal scale, such acceleration may modify weather regimes and, thus, potentially increase the number of compound weather and climate events. Among them, tropical cyclones can bring destructive high winds, torrential rain, storm surges and occasionally tornadoes in association with a variety of hazards, especially in coastal urban regions. In this study, we apply a newly developed WRF-age model, i.e., the Weather Research and Forecasting model enhanced with an age-weighted water tracking approach, to a coastal urban region in Southeast China. The source and transport of atmospheric water vapor in one Northwest Pacific Ocean cyclone, here, Hato in August 2017, are exemplarily examined by means of tracking oceanic evaporation. Two indices, i.e., the contribution ratio and the atmospheric water residence time, are used to better understand how much and how fast the oceanic evaporation contributes to the development of tropical cyclone Hato. Our simulation results show that, within 24 hours, the contribution ratio of the tagged oceanic evaporation to the total water vapor researches up to around 25%. In addition, the spatial pattern of the atmospheric water residence time shows that the oceanic evaporation below the rainbands of Hato (around 9 hours) fuels faster in its development than the oceanic evaporation from the surrounding region (15 hours). These findings emphasize the important role of oceanic evaporation to tropical cyclone development. Our study demonstrates that the WRF-age model can be applied to quantify the acceleration of tropical cyclone development under global warming.