P46     Effect of the land surface hydrologic processes on land-air interactions in Taiwan using WRF-Noah and WRF-NoahMP.

Tzu-Ying, Chen, and Fang-Yi Cheng, Graduate institute of Atmospheric Physics, National Central University, Taiwan

The land surface hydrologic processes such as surface/subsurface runoff and soil-groundwater interaction strongly affect soil moisture. In order to understand how the land surface hydrologic processes affect the land-air interactions in Taiwan, the WRF model coupled with two land surface models (Noah and Noah-MP) were applied. The major difference between the two LSMs is that a free drainage is specified as the lower boundary condition in Noah LSM while the Noah-MP considers the dynamic interactions between the soil and the aquifer. Moreover, Noah-MP LSM adopts semi-tile approach to calculate energy fluxes from vegetated and bare land separately, while Noah LSM combines surface layer of vegetation and soil surface, over which surface energy fluxes are computed.

The study period is from 1 August to 10 August 2015 during which a moderate intensity typhoon made a landfall in Taiwan. Before the influence of the typhoon, the atmospheric conditions were relatively dry and calm and soils were also dry. Unlike Noah LSM, Noah-MP LSM considers the groundwater exchanging processes between the aquifer and the soils. With the upward water flux from the aquifer, the Noah-MP LSM simulates higher soil moisture and higher latent heat flux. The increased moisture in the atmosphere before typhoon landing, which further affects the rainfall simulation.