Abstract
AbstractMultiple observational data sets and atmosphere‐only simulations from the Coupled Model Intercomparison Project Phase 5 are analyzed to characterize recent rainfall variability and trends over Africa focusing on 1983–2010. Data sets exhibiting spurious variability, linked in part to a reduction in rain gauge density, were identified. The remaining observations display coherent increases in annual Sahel rainfall (29 to 43 mm yr−1 per decade), decreases in March–May East African rainfall (−14 to −65 mm yr−1 per decade), and increases in annual Southern Africa rainfall (32 to 41 mm yr−1 per decade). However, Central Africa annual rainfall trends vary in sign (−10 to +39 mm yr−1 per decade). For Southern Africa, observed and sea surface temperature (SST)‐forced model simulated rainfall variability are significantly correlated (r~0.5) and linked to SST patterns associated with recent strengthening of the Pacific Walker circulation.
Highlights
Changes in rainfall patterns can have profound societal consequences, across Africa where rainfall plays a crucial role in sustaining livelihoods and economic development
A reduction in rain gauge density across Central Africa is linked to an artificial reduction in precipitation which appears to affect the African Rainfall Climatology (ARC) data set and to some degree the Center Merged Analysis of Precipitation (CMAP) data set
Since these data sets are outliers compared to the remaining observational and model-based estimates with regard to Africa-wide rainfall they were not considered in our assessment of regional trends
Summary
Changes in rainfall patterns can have profound societal consequences, across Africa where rainfall plays a crucial role in sustaining livelihoods and economic development. The development of several long-term satellite-based data sets tailored for African research and climate monitoring [e.g., Novella and Thiaw, 2013; Maidment et al, 2014] has provided an opportunity to assess recent changes in African precipitation. We examine Africa-wide precipitation variability and trends as portrayed by an array of observational data sets and CMIP5 atmosphere-only model simulations to characterize and understand robust changes in African rainfall during the last three decades (1983–2014). Climate model simulations forced by observed SSTs and sea ice and historical radiative forcings from the CMIP5 data set [Taylor et al, 2012] are exploited (see Table S1) These atmosphere-only (Atmospheric Model Intercomparison Project version 5 (AMIP5)) simulations (available until the end of 2008) demonstrate skill in reproducing observed interannual rainfall variability over tropical land [Liu et al, 2012]. Throughout, deseasonalized time series were obtained by calculating the difference between each monthly value and the respective monthly rainfall climatology
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