Abstract. In the current work we present six hindcast Weather Research and Forecasting (WRF) simulations for the EURO-CORDEX domain with different configurations in microphysics, convection and radiation for the time period 1990–2008. All regional model simulations are forced by the ERA-Interim reanalysis and have the same spatial resolution (0.44°). These simulations are evaluated for surface temperature, precipitation, short- and longwave downward radiation at the surface and total cloud cover. The analysis of the WRF ensemble indicates systematic biases in both temperature and precipitation linked to different physical mechanisms for the summer and winter season. Overestimation of total cloud cover and underestimation of downward shortwave radiation at the surface, mostly when using Grell–Devenyi convection and the CAM radiation scheme, intensifies the negative summer temperature bias in northern Europe (max −2.5 °C). Conversely, a strong positive downward shortwave summer bias in central (40–60%) and southern Europe mitigates the systematic cold bias in WRF over these regions, signifying a typical case of error compensation. Maximum winter cold bias is over north-eastern Europe (−2.8 °C); this location is indicative of land–atmosphere rather than cloud-radiation interactions. Precipitation is systematically overestimated in summer by all model configurations, especially the higher quantiles, which are associated with summertime deep cumulus convection. The Kain–Fritsch convection scheme produces the larger summertime precipitation biases over the Mediterranean. Winter precipitation is reproduced with lower biases by all model configurations (15–30%). The results of this study indicate the importance of evaluating not only the basic climatic parameters of interest for climate change applications (temperature-precipitation), but also other components of the energy and water cycle, in order to identify the sources of systematic biases, possible compensatory or masking mechanisms and suggest methodologies for model improvement.

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 surface scheme, the Common Land Model (CLM); a new planetary boundary layer (PBL) scheme, the University of Washington PBL (UW-PBL); and new convection schemes including Tiedtke, and Mixed1 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 the best configuration of RegCM4.3 for simulating the climate of South America (SA). The main motivation is to come up with the best configurations of RegCM4.3 over the SA domain for use in the Coordinated Regional Downscaling Experiment (CORDEX) project. We analyzed 7 simulations for the 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 we changed these schemes using the new RegCM4.3 options. The evaluation of the simulations was carried out in 3 groups: (1) sensitivity to convection (Mixed1, MIT and Tiedtke), (2) sensitivity to the PBL (Holtslag and UW-PBL) and (3) sensitivity to surface processes (BATS and CLM). Considering all of SA, the results show that precipitation is better simulated with the schemes of the control simulation, while for air temperature, better results were obtained using the MIT cumulus scheme together with the CLM scheme. In summary, we recommend 2 configurations for the CORDEX project over SA: (1) the schemes used in the control simulation and (2) the MIT scheme for cumulus convection, Holtslag for the PBL, and CLM for surface interaction processes.KEY WORDS: South America · RegCM4.3 · CORDEX · Simulation · Precipitation · Temperature · Evapotranspiration Resale or republication not permitted without written consent of the publisherClim Res 60: [215][216][217][218][219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234] 2014 lysis (e.g. NCEP, ERA-Interim) to be used as initial and boundary conditions in RCMs, for a range of applications. In particular, for South America (SA), RCMs began to be utilized in the 2000s to simulate the observed features of the present climate (Chou et al. 2000, Menéndez et al. 2001, Nobre et al. 2001. The use of RCMs increased in recent years, encompassing objectives such as: investigation of the RCMs' ability to simulate the climate (Nicolini et al. 2002, Seth & Rojas 2003, Fernandez et al. 2006a; the use of different initial and boundary condition forcing (Seth & Rojas 2003); validation of the simulated diurnal cycle of the precipitation (da Rocha et al. 2009); comparison of the simulated interannual variability of the climate with observations (Misra et al. 2002, Fernandez et al. 2006b); investigation of the ability of RCMs to simulate specific atmospheric systems climatology (Reboita et al. 2010a); and exploration of future climate scenarios (Nuñez et al. 2009, Maren...

No abstract

No abstract