Future change in precipitation seasonality over the Horn of Africa in high-resolution simulation

Abstract

<p>Extreme weather creating a widespread humanitarian crisis over East Africa in recent decades. The seasonal cycle of precipitation over the Horn of Africa (HOA) shows bimodality with long rain and short rain. Most of the models fail to capture biannual rainfall seasonal cycles, due to circulation response to unrealistically dominate the annual mean. The Community Earth System Model (CESM) high-resolution model simulation has been employed to study the sensitivity. Precipitation distribution over HOA shows regional variations where most of the region show the bimodal distribution and the intrinsically complex. This bimodality is nominally associated with tropical rain belt, but topography and SST-forcing also play an important role in influencing the timing and intensity of seasonal rainfall. The results show that overall rainfall seasonality is increased, with intensification over high elevation. Precise representation of rainfall seasonal cycle over HOA adds confidence for future projected changes in seasonality. An important question is whether and how the seasonal cycle over HOA responds to anthropogenic forcing. We show that the future change in precipitation seasonal cycle and accumulation over HOA can be explained by the surface ocean process which module SSTs along the coastline of Somalia. The moisture convergence over low elevation land is basically regulated through the north-south SST gradient. In conclusion, future global warming leads to the intensified seasonal cycle of precipitation with a projected increase in the short rain season over east Africa. Further analysis demonstrates how topography modulates the seasonality of HOA.</p>