Interannual Variability of Sub-Saharan Africa Rainfall in a High-Resolution Coupled Climate Model

The ability of a new high resolution (T382) version of the National Centers for Environmental Prediction coupled atmosphere-ocean climate forecast system version 2 (CFSv2), to reproduce the interannual variability of precipitation in Sub-Saharan Africa and associated teleconnections is examined. The model hereafter called CFST382 was developed by the Indian Institute of Tropical Meteorology. The analysis is for the period 1981-2009. The satellite based Global Precipitation Climatology Project (GPCP) data is used as proxy for observed rainfall and to validate the models. We examine rainfall patterns during the four main seasons in DJF, MAM, JAS, and OND. The model is able to reproduce the basic state of the climate despite considerable differences in the representation of the intensities and locations of the rainfall. Biases in the model are presented. The spatially averaged values of standard deviation are lower than that observed. However, the model is able to reproduce to some extent the main features of the precipitation maximum variability. The areas of highest variability are generally depicted, but with deficiencies in the amplitudes and locations. Teleconnections in the model are investigated by first conducting an EOF in the precipitation anomaly fields and then by performing a regression of the first or second EOF time series onto the global SST. Focusing on JAS rainfall season, the model is able to depict the dipole pattern between the Sahel and the Gulf of Guinea rainfall, and to some extent the upward trend in Sahel rainfall over the latest decade in the period. The relationship to SST is also examined. The observed influence of tropical north Atlantic SST on the Sahel rainfall is reasonably represented. For DJF and OND southern and eastern Africa rainfall, the prominence of the Indian Ocean dipole mode and SST gradients between the Pacific warm pool and the Indian Ocean is well captured. The CFST382 model performance is compared with that of CFSv2 and the NMME models, and results are presented.