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CMIP5 model simulations of Ethiopian Kiremt-season precipitation: current climate and future changes
Abstract
© 2015, Springer-Verlag Berlin Heidelberg.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.
Type
Journal articlePermalink
https://hdl.handle.net/10161/10253Published Version (Please cite this version)
10.1007/s00382-015-2737-4Publication Info
Li, Laifang; Li, W; Ballard, Tristan; Ge Sun; & Jeuland, Marc (2016). CMIP5 model simulations of Ethiopian Kiremt-season precipitation: current climate
and future changes. Climate Dynamics, 46(9-10). pp. 2883-2895. 10.1007/s00382-015-2737-4. Retrieved from https://hdl.handle.net/10161/10253.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Wenhong Li
Associate Professor of Climate
Dr. Li's research interests focus primarily on climate dynamics, land-atmosphere interaction,
hydroclimatology, and climate modeling. Her current research is to understand how
the hydrological cycle changes in the current and future climate and their impacts
on the ecosystems, subtropical high variability and change, unforced global temperature variability,
and climate and health issues.

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