Climate Dynamics

, Volume 46, Issue 9–10, pp 2883–2895 | Cite as

CMIP5 model simulations of Ethiopian Kiremt-season precipitation: current climate and future changes

  • Laifang Li
  • Wenhong Li
  • Tristan Ballard
  • Ge Sun
  • Marc Jeuland
Article
  • 286 Downloads

Abstract

Kiremt-season (June–September) precipitation provides a significant water supply for Ethiopia, particularly in the central and northern regions. The response of Kiremt-season precipitation to climate change is thus of great concern to water resource managers. However, the complex processes that control Kiremt-season precipitation challenge the capability of general circulation models (GCMs) to accurately simulate precipitation amount and variability. This in turn raises questions about their utility for predicting future changes. This study assesses the impact of climate change on Kiremt-season precipitation using state-of-the-art GCMs participating in the Coupled Model Intercomparison Project Phase 5. Compared to models with a coarse resolution, high-resolution models (horizontal resolution <2°) can more accurately simulate precipitation, most likely due to their ability to capture precipitation induced by topography. Under the Representative Concentration Pathway (RCP) 4.5 scenario, these high-resolution models project an increase in precipitation over central Highlands and northern Great Rift Valley in Ethiopia, but a decrease in precipitation over the southern part of the country. Such a dipole pattern is attributable to the intensification of the North Atlantic subtropical high (NASH) in a warmer climate, which influences Ethiopian Kiremt-season precipitation mainly by modulating atmospheric vertical motion. Diagnosis of the omega equation demonstrates that an intensified NASH increases (decreases) the advection of warm air and positive vorticity into the central Highlands and northern Great Rift Valley (southern part of the country), enhancing upward motion over the northern Rift Valley but decreasing elsewhere. Under the RCP 4.5 scenario, the high-resolution models project an intensification of the NASH by 15 (3 × 105 m2 s−2) geopotential meters (stream function) at the 850-hPa level, contributing to the projected precipitation change over Ethiopia. The influence of the NASH on Kiremt-season precipitation becomes more evident in the future due to the offsetting effects of two other major circulation systems: the East African Low-level Jet (EALLJ) and the Tropical Easterly Jet (TEJ). The high-resolution models project a strengthening of the EALLJ, but a weakening of the TEJ. Future changes in the EALLJ and TEJ will drive this precipitation system in opposite directions, leading to small or no net changes in precipitation in Ethiopia.

Keywords

Ethiopian Kiremt-season precipitation CMIP5 model simulations Climate change impact North Atlantic subtropical high 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Laifang Li
    • 1
    • 5
  • Wenhong Li
    • 1
  • Tristan Ballard
    • 2
  • Ge Sun
    • 3
  • Marc Jeuland
    • 4
  1. 1.Earth and Ocean Sciences, Nicholas School of the EnvironmentDuke UniversityDurhamUSA
  2. 2.Environmental Sciences, Trinity College of Arts and SciencesDuke UniversityDurhamUSA
  3. 3.Eastern Forest Environmental Threat Assessment CenterUSDA Forest ServiceRaleighUSA
  4. 4.Sanford School of Public Policy and Duke Global Health InstituteDuke UniversityDurhamUSA
  5. 5.Physical Oceanography DepartmentWoods Hole Oceanographic InstitutionWoods HoleUSA

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