Analyses of rainfall extremes in East Africa based on observations from rain gauges and climate change simulations by CORDEX RCMs
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Date
2020
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Climate Dynamics
Abstract
This study derived twelve Extreme Rainfall Indices (ERIs) such as the Maximum Dry Spell (MDS) and Maximum Wet
Spell (MWS) from daily rainfall observed over the period 1961–1990 at nine locations across East Africa. Capacity of six
CO-ordinated Regional Climate Downscaling EXperiment (CORDEX) Africa Regional Climate Models (RCMs) driven
by twenty six Climate Model Intercomparison Project phase 5 (CMIP5) General Circulation Models (GCMs) to reproduce
the observed ERIs with respect to long-term mean and trends was evaluated. Four RCMs and their five driving GCMs were
further analyzed with respect to ERIs. Ensemble means of the RCMs’ biases in simulating trends in several ERIs were of
magnitudes above 50%. On average, biases in reproducing long-term mean were smaller than those for trends in ERIs. The
difference between the performances of RCMs and GCMs depended on the selected RCM–GCM pair. The ensemble means
of the RCMs reproduced observed ERIs better than the individual RCMs corroborating that the use of multi-model ensembles
can boost credibility of climate change simulations and projections. The RCMs performed better than their driving
GCMs in reproducing MDS. The biases of both the RCMs and GCMs were smaller in reproducing the MWS than MDS.
Nonetheless, in reproducing observed MWS, the ensemble mean of RCMs’ biases was slightly larger than that of the driving
GCMs indicating possible adding up of the uncertainties from the GCMs and RCMs. Suggested RCMs’ improvements
regarding aerosol impacts on rainfall include adding missing constituents (like nitrate), and refining the crudely represented
components. RCMs also require high resolution description (in both space and time) of land use types, land surface covers
and characteristics as well as landscape heterogeneity. The GCMs to be used as the initial and lateral boundary conditions
for the RCMs require improvement in their representation of key dynamical and thermodynamical feedbacks in the Tropical
Indian Ocean.
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Keywords
CORDEX RCMs, Climate change, East african rainfall, Trend analysis, Climate change indices, CMIP5 GCMs
Citation
Onyutha, C. (2020). Analyses of rainfall extremes in East Africa based on observations from rain gauges and climate change simulations by CORDEX RCMs. Climate Dynamics, 54(11), 4841-4864. https://doi.org/10.1007/s00382-020-05264-9