Validating the Sensitivity of a Regional Climate Model to Land Surface Parameterization Schemes for East Asian Summer Monsoon

Abstract:

Land surface processes play an important role in East Asian Summer Monsoon (EASM), and its parameterization schemes may cause uncertainty of dynamic downscaling in regional climate model (RCM) for EASM. In this study we investigated the sensitivity of RCM to land surface parameterization (LSP) schemes for long-term simulations of EASM. Simulations for 22-year EASM using Weather Research and Forecasting (WRF) Model coupled with four different LSP schemes (Noah-MP, CLM4, Pleim-Xiu and SSiB; Four simulations are named Sim-Noah, Sim-CLM, Sim-PX and Sim-SSiB respectively) were conducted. The 22-year averaged spatial distribution and intensity of downscaling large-scale circulation, precipitation and 2-m temperature were compared with ERA-Interim/ observations. Results show that the downscaling ability of RCM for EASM is sensitive to LSP scheme. Furthermore, RCM does add more information than reanalysis/GCM-products. And Sim-PX and Sim-SSiB show closer to observation than Sim-Noah and Sim-CLM for monsoon precipitation and 2-m temperature. To clarify the physical and dynamic mechanisms of the sensitivity, the differences of energy budgets and their atmospheric effects between Ens-Noah-CLM (ensemble mean averaging Sim-Noah and Sim-CLM) and Ens-PX-SSiB (ensemble mean averaging Sim-PX and Sim-SSiB) were compared. We found that the intensity of SH flux over Asian continent in Ens-Noah-CLM is stronger than that in Ens-PX-SSiB, which induces the higher tropospheric temperature over land. The land-sea thermal contrast will be influenced. Then the adaptive modulation of GHT gradients affects wind flow (through geostrophic balance), especially at lower-level. As a result, the simulation of large-scale circulation, monsoon precipitation and 2-m temperature are influenced accordingly.