Assessment of RegCM4.3 over the CORDEX South America domain: sensitivity analysis for physical parameterization schemes

Abstract

ABSTRACT: In mid-2012, the Abdus Salam International Centre for Theoretical Physics (ICTP)released version 4.3 of the Regional Climate Model (RegCM4.3). This version includes a new sur-face scheme, the Common Land Model (CLM); a new planetary boundary layer (PBL) scheme, theUniversity of Washington PBL (UW-PBL); and new convection schemes including Tiedtke, andMixed1 and Mixed2—with Grell (MIT) over the land and MIT (Grell) over the ocean for Mixed1(Mixed2). These implementations suggest the necessity of an evaluation study to determine thebest configuration of RegCM4.3 for simulating the climate of South America (SA). The main moti-vation is to come up with the best configurations of RegCM4.3 over the SA domain for use in theCoordinated Regional Downscaling Experiment (CORDEX) project. We analyzed 7 simulations forthe period 1990−2000. The control simulation used the Biosphere−Atmosphere Transfer Scheme(BATS), Holtslag for the PBL and Mixed1 for cumulus convection. In the other simulations wechanged these schemes using the new RegCM4.3 options. The evaluation of the simulations wascarried out in 3 groups: (1) sensitivity to convection (Mixed1, MIT and Tiedtke), (2) sensitivity tothe PBL (Holtslag and UW-PBL) and (3) sensitivity to surface processes (BATS and CLM). Consid-ering all of SA, the results show that precipitation is better simulated with the schemes of thecontrol simulation, while for air temperature, better results were obtained using the MIT cumulusscheme together with the CLM scheme. In summary, we recommend 2 configurations for theCORDEX project over SA: (1) the schemes used in the control simulation and (2) the MIT schemefor cumulus convection, Holtslag for the PBL, and CLM for surface interaction processes.KEY WORDS: South America · RegCM4.3 · CORDEX · Simulation · Precipitation · Temperature ·Evapotranspiration