Added Value of a Convection Permitting Model in Simulating Atmospheric Water Cycle Over the Asian Water Tower.

The Tibetan Plateau (TP) is known as Asian Water Tower and its atmospheric water cycle has been a lasting challenge to climate modeling community. Here, we compare two sets of the Met Office Unified Model simulations—one is a convection‐parameterized version (large‐scale model; LSM) and the other is a convection‐permitting model (CPM) simulation. The added value of the CPM in terms of atmospheric water cycle process is analyzed, including external moisture transport, fraction of atmospheric water vapor converting to precipitation and the precipitation recycle ratio. Results show that the simulated TP precipitation and evaporation for the summer of 2009 is significantly improved in the CPM. First, the overestimation of atmospheric water cycle by LSM is improved in CPM due to a reasonable representation of the fraction of atmospheric water vapor converting to precipitation. The overestimation of precipitation recycle ratio also indicates the LSM generates excessive convection compared to the CPM and therefore has a larger wet bias over the TP. Second, a better simulation of local precipitation has feedback on the circulation. Compared with the LSM, the less moisture convergence in the CPM is dominated by the stronger outflow through the eastern edge of the TP rather than the weaker inflow, implying the upscale effects of the resolved moist convection on the moisture transport over the TP. Our results imply that the CPM is a useful tool in the reproduction of moisture transport and atmospheric water cycle process over the Asian Water Tower and other regions of the world with complex topography. Plain Language Summary: The atmospheric water cycle over the Tibetan Plateau (TP, also as known as the Asian Water Tower) has been a challenge to climate models with convection parameterization. Benefiting from the high enough resolution, convection‐permitting model (CPM) can explicitly resolve the deep convection and therefore reduce the bias related with the convection parameterization scheme. Here, we compare a CPM with its low resolution version that employs convection‐parameterization in simulating atmospheric water cycle process over the TP. We find the precipitation and evaporation over the TP is significantly improved in the CPM. There is more water vapor flowing out of the TP and less water vapor in the atmosphere converting into the precipitation in the CPM, resulting in a reduced wet bias. CPM is free from the constrains of the convection parameterization scheme and therefore depicts the atmospheric water cycle over the TP better. Key Points: The convection‐permitting model (CPM) better reproduces precipitation over the Tibetan Plateau than convection‐parameterized model (large‐scale model [LSM])The overestimation of atmospheric water cycle by LSM is improved in CPM simulationThe interaction between large‐scale circulation and convection further reduces moisture convergence and wet bias in the CPM [ABSTRACT FROM AUTHOR]