Sensitivity of The Summer Precipitation Simulated With WRF Model To Planetary Boundary Layer Parameterization Over The Tibetan Plateau and Its Downstream Areas

Abstract

This study examines the sensitivity of simulated precipitation to planetary boundary layer (PBL) schemes over the Tibetan Plateau (TP) and the Yangtze River Valley (YRV). The summer precipitation from 15 June to 30 July 2010 is simulated with the Weather Research and Forecasting (WRF) model over these areas. Three PBL parameterization schemes, Mellor-Yamada-Janji? (MYJ), Yonsei University (YSU), and Medium-Range Forecast (MRF) are compared in the simulation. The simulated hourly precipitation overestimates the observed precipitation, and the simulation of MRF scheme is more close to the observation. In general, the WRF model shows good (poor) ability in simulating the diurnal cycle of precipitation over the TP (the upper YRV). Although the WRF model simulates a two-peak pattern different from the observed one-peak pattern in the middle YRV, both of them are generally close in trend. The choice of PBL parameterization schemes affects not only the amplitude of the precipitation but also the phase of diurnal cycle, and MRF scheme simulates better in precipitation amount than YSU and MYJ schemes. Among the three PBL schemes, the hourly PBL height of MYJ scheme is higher than those of MRF and YSU schemes. All the three PBL schemes present a similar diurnal cycle of PBL height, and the differences of PBL heights are responsible for the discrepancies in the simulated precipitation amounts. The three largest lakes in the central TP result in three large centers of the minimum PBL heights and of the average hourly PBL heights at the same locations, which are responsible for the maximum centers in the simulated precipitation in the central TP.