Large-scale atmospheric circulation and global sea surface temperature associations with Horn of Africa June-September rainfall
MetadataShow full item record
This study uses correlation, regression, and composite analyses for the period 1970–1999 to explore the relationships between the June–September rainfall in the Horn of Africa (especially Ethiopian) and large-scale regional atmospheric circulation patterns across Africa and the Atlantic and Indian Oceans, and global sea surface temperature (SST) anomalies. Abundant rainfall in the Horn of Africa is associated with enhanced westerlies across western and central Africa. These westerlies are produced by a stronger north-east directed mean sea level pressure (MSLP) gradient resulting from MSLP intensification over the Gulf of Guinea and deepening of the monsoon trough across the Arabian Peninsula. This is reflected by a strong correlation (−0.71) between 5-day (pentad) Ethiopian rainfall and the Gulf of Guinea minus the Arabian Peninsula MSLP difference. This correlation decreases to − 0.39 when the seasonal cycles are removed from both time series. A wet Horn of Africa monsoon is also associated with deep moist air extending up to mid-troposphere and large water vapour transport convergence across much of Ethiopia, a strong Somali low-level jet, and a strong tropical easterly jet (TEJ).Although there are large changes in TEJ strength, the position of the jet axis shows little variation between wet and dry events. Associated with the TEJ, the strongest upper level divergence occurs at 100 hPa, where the raw/de-seasonalized zonal wind speed correlates negatively (−0.71/− 0.23) with the corresponding Ethiopian rainfall at the pentad time-scale. Furthermore, SSTs over the equatorial Pacific, Indian, and southern Atlantic Oceans correlate strongly with contemporary Ethiopian summer rainfall. In general, Ethiopian rainfall is suppressed during El Niño and enhanced during La Niña. This identification and documentation of the regional atmospheric circulation patterns and global SST anomalies directly linked to rainfall variability over Ethiopia/Horn of Africa, are crucial for developing statistical prediction schemes and designing climate model simulations for the region on intra-seasonal to inter-annual time-scales.
Showing items related by title, author, creator and subject.
Seasonal-to-Interannual Variability of Ethiopia/Horn of Africa Monsoon. Part I: Associations of Wavelet-Filtered Large-Scale Atmospheric Circulation and Global Sea Surface TemperatureSegele, Z.; Lamb, P.; Leslie, Lance (2009)Horn of Africa rainfall varies on multiple time scales, but the underlying climate system controls on this variability have not been examined comprehensively. This study therefore investigates the linkages between ...
Understanding the association between climate variability and the Nile's water level fluctuations and water storage changes during 1992–2016Khaki, M.; Awange, Joseph; Forootan, E.; Kuhn, Michael (2018)With the construction of the largest dam in Africa, the Grand Ethiopian Renaissance Dam (GERD) along the Blue Nile, the Nile is back in the news. This, combined with Bujagali Dam on the White Nile are expected to bring ...
Evaluation and adaptation of a regional climate model for the Horn of Africa: rainfall climatology and interannual variabilitySegele, Z.; Leslie, Lance; Lamb, P. (2009)This study evaluates the ability of the Abdus Salam International Center for Theoretical Physics (ICTP) version 3 Regional Climate Model (RegCM3) to reproduce the observed rainfall amounts and distribution over the ...