Dynamical Downscaling of Austral Summer Climate Forecasts over Southern Africa Using a Regional Coupled Model

J. V. Ratnam*, S. K. Behera, S. B. Ratna, C. J.W. De Rautenbach, C. Lennard, J. J. Luo, Y. Masumoto, K. Takahashi, T. Yamagata

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The prediction skill of dynamical downscaling is evaluated for climate forecasts over southern Africa using the Advanced ResearchWeather Research and Forecasting (WRF) model. As a case study, forecasts for the December-February (DJF) season of 2011/12 are evaluated. Initial and boundary conditions for the WRF model were taken from the seasonal forecasts of the Scale Interaction Experiment-Frontier Research Center for Global Change (SINTEX-F) coupled general circulation model. In addition to sea surface temperature (SST) forecasts generated by nine-member ensemble forecasts of SINTEX-F, theWRFwas also configured to use SST generated by a simple mixed layer Price-Weller-Pinkel ocean model coupled to the WRF model. Analysis of the ensemble mean shows that the uncoupled WRF model significantly increases the biases (errors) in precipitation forecasted by SINTEX-F. When coupled to a simple mixed layer ocean model, the WRF model improves the spatial distribution of precipitation over southern Africa through a better representation of the moisture fluxes. Precipitation anomalies forecasted by the coupled WRF are seen to be significantly correlated with the observed precipitation anomalies over South Africa, Zimbabwe, southern Madagascar, and parts of Zambia and Angola. This is in contrast to the SINTEX-F global model precipitation anomaly forecasts that are closer to observations only for parts of Zimbabwe and South Africa. Therefore, the dynamical downscaling with the coupled WRF adds value to the SINTEX-F precipitation forecasts over southern Africa. However, the WRF model yields positive biases (.28C) in surface air temperature forecasts over the southern African landmass in both the coupled and uncoupled configurations because of biases in the net heat fluxes.

Original languageEnglish
Pages (from-to)6015-6032
Number of pages18
JournalJournal of Climate
Volume26
Issue number16
DOIs
Publication statusPublished - 2013 Aug
Externally publishedYes

ASJC Scopus subject areas

  • Atmospheric Science

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