Abstract
Dynamic numerical models of the atmosphere are the main tools used for weather and climate forecasting as well as climate projections. Thus, this work evaluated the systematic errors and areas with large uncertainties in precipitation over the South American continent (SAC) based on regional climate simulations with the weather research and forecasting (WRF) model. Ten simulations using different convective, radiation, and microphysical schemes, and an ensemble mean among them, were performed with a resolution of 50 km, covering the CORDEX-South America domain. First, the seasonal precipitation variability and its differences were discussed. Then, its annual cycle was investigated through nine sub-domains on the SAC (AMZN, AMZS, NEBN, NEBS, SE, SURU, CHAC, PEQU, and TOTL). The Taylor Diagrams were used to assess the sensitivity of the model to different parameterizations and its ability to reproduce the simulated precipitation patterns. The results showed that the WRF simulations were better than the ERA-interim (ERAI) reanalysis when compared to the TRMM, showing the added value of dynamic downscaling. For all sub-domains the best result was obtained with the ensemble compared to the satellite TRMM. The largest errors were observed in the SURU and CHAC regions, and with the greatest dispersion of members during the rainy season. On the other hand, the best results were found in the AMZS, NEBS, and TOTL regions.
Highlights
We focus on cumulus parameterization (CU), radiation parameterization (RA) and microphysics (MP), while planetary boundary layer (PBL) (Mellor–Yamada–Janjic; MYJ) [31,32], surface layer (Monin–Obukhov Janjic; MOJ) [33,34] and land surface (Noah LSM) [35] schemes were kept fixed for all model configurations
This study evaluated the systematic errors and areas with large uncertainties in a simulated precipitation over the South American continent
The analyses through Taylor diagrams showed that, in all sub-domains, the ensemble of all experiments was the best option, with results consistent with those from the satellite data obtained from Tropical Rainfall Measuring Mission (TRMM)
Summary
This study was conducted in a climate perspective (a 2-year simulation) instead of a weather forecast approach, which is the most frequent use of WRF Despite this period being short compared to the usual climate timescale of 30-years, it does not prejudice the main goal of this study i.e., to find out which set of parameterizations is better suited to South America. A similar study was made by [27], who applied the dynamical downscaling technique in the WRF model over the MED-CORDEX domain for a period of one year (2002), to investigate and validate the performance of different physics parameterizations This study fills this gap and contributes toward the CORDEX effort over this region for subsequent climate modeling in future experiments. Many users of the WRF model carry out research on different regions of the SAC and, our results can serve as a comparative reference
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