The performance of regional climate models driven by various general circulation models in reproducing observed rainfall over East Africa

Assamnew, Abera Debebe; Tsidu, Gizaw Mengistu

doi:10.1007/s00704-020-03357-3

Cited by 20 publications

(13 citation statements)

References 66 publications

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“…There is no systematic improvement in the precipitation simulation when increasing resolution from 27-km to 9-km, and results are similar to GCMs and regional models with non-CP resolutions (e.g., James et al 2018, Assamnew andTsidu 2020). Improvement comes when the convective parameterization is no longer needed at 3-km resolution and precipitating systems are resolved by the model's governing equations, in agreement with van Lipzig et al ( 2022).…”

Section: A Regional Distribution and Diurnal Cycling Of Boreal Fall P...supporting

confidence: 79%

Understanding the Regionality and Diurnal Cycles of Precipitation in the Lake Victoria Basin during Boreal Fall

Cook

Vizy

2022

Preprint

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The diurnal cycle of rainfall in the Lake Victoria Basin of East Africa results from the super positioning of regional circulations driven by lake/land temperature differences and topography in the presence of the large-scale flow. Analysis of a triple-nested regional model simulation with a convective-permitting inner domain shows how these elements combine to produce the observed regionality of precipitation, including diurnal cycling, in boreal fall. A single diurnal rainfall peak occurs throughout the basin, but the time of maximum rainfall varies within the basin. The rainy period over the lake begins with precipitation over the northern part of the lake near 02Z (0500 LT), so it is not simply nighttime rain driven by lake/land breezes. Onset of the rainy period occurs only when low geopotential heights over the relatively warm lake cause a southward branch of the Turkana Jet to form. The formation of the jet depends on nighttime cooling over the Eastern Rift Mountains, which acts to direct the large-scale, moist flow around the topography. Topography also plays a role in the daytime rainy period over land in the Lake Victoria Basin. Moist divergence over the lake supports convergence and precipitation over the shore regions. Precipitation rates are twice the magnitude over the eastern shore compared with the western shore because daytime warming of the high elevations of the Eastern Rift Mountains allows the large-scale easterly flow to go over the mountains. This easterly flow converges with the lake/land circulation and doubles precipitation rates over the eastern shore.

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Section: A Regional Distribution and Diurnal Cycling Of Boreal Fall P...supporting

confidence: 79%

Understanding the Regionality and Diurnal Cycles of Precipitation in the Lake Victoria Basin during Boreal Fall

Cook

Vizy

2022

Preprint

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“…Given the fact that simulations of the climatic state of a particular area or the whole world by global climate models differ due to different factors, such as initial and boundary conditions, related climate variables, and physical structure, it is vital to evaluate the performance of different models to replicate observed climate. Previous studies have been carried out over East Africa to assess the historical simulations of the CMIP phase 5 (CMIP5) models in simulating precipitation, and some notable biases have been indicated (Yang et al ., 2015b; Mumo and Yu, 2019; Ongoma et al ., 2019; Onyutha et al ., 2019; Assamnew and Tsidu, 2020; Ayugi et al ., 2020). For instance, the CMIP5 models highly overestimated the OND precipitation but underestimated the MAM precipitation (Yang et al ., 2015b; Mumo and Yu, 2019; Ongoma et al ., 2019; Onyutha et al ., 2019).…”

Section: Introductionmentioning

confidence: 99%

Coupled Model Intercomparison Project phase 6 evaluation and projection of East African precipitation

Makula

Zhou

2021

Intl Journal of Climatology

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This study evaluates the performance of 43 Coupled Model Intercomparison Project phase 6 (CMIP6) models in reproducing annual cycle, climatology, and trend of observed precipitation over East Africa during 1950–2014. The results show that the CMIP6 models display good performance in simulating the annual cycle (i.e., bimodal pattern) of East African precipitation; however, most models and the multimodel ensemble mean (ENSEM) underestimate the March to May (MAM) precipitation while overestimating the October to December (OND) precipitation. Spatially, most models seem to perform relatively better in simulating OND precipitation compared to MAM season, despite wet (dry) biases over most parts of East Africa with the wettest (driest) biases over the Lake Victoria basin (southeastern Tanzania) during OND (MAM). The metrics have shown that nine models (i.e., MPI‐ESM1‐2‐HR, AWI‐CM‐1‐MR, MPI‐ESM1‐2‐LR, IPSL‐CM6A‐LR, CAS‐ESM2‐0, BCC‐CSM2‐MR, NorESM2‐LM, CESM2‐WACCM, and CMCC‐CM2‐SR5) outperform the other individual models during both OND and MAM. Compared with individual models, the ENSEM better agrees with the observation. Besides, the ENSEM and most models can reproduce the increasing trend in OND precipitation as observed over East Africa. However, for the secular change of MAM precipitation, given that half of the models show increasing trends, the ENSEM simulation produces an inconsistent trend with the observation. The ensemble of the above nine models with better performance projects an increase of precipitation averaged over East Africa in both MAM and OND by the end of the 21st century, with larger changes under SSP5‐8.5 than under SSP2‐4.5. Spatially, the largest percentage increase in MAM precipitation is projected to occur in central Tanzania and northwestern Kenya, while southeastern Tanzania shows the greatest percentage decrease. The projected percentage increases in OND precipitation are larger in the northeastern highlands of Tanzania and northwest Kenya.

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“…Test for consistency of rainfall record by using Double mass curve : A graph ( Fig. 6 ) comparing the cumulative catch at the interest rain gauges versus the cumulative catches of one or more gauges in places that have seen comparable hydro-meteorological occurrences and are recognized to be consistent is called a double-mass curve (Equation (2) ) [ 29 , 30 ].

where : Px - Adjusted Rainfall of station, Px ’ - Observed Rainfall at station x, tan α′ - The slope of the adjusted mass curve, tan α – The slope of the Original mass curve.…”

Section: Methodsmentioning

confidence: 99%

“…The ratio of root mean square error to observation standard deviation (RSR) : It serves as an error index indicator [ 29 ]. RSR has a value between zero and one, with the lower value, closer to zero, suggesting better model representation and one indicating poor model performance (Kwakye et al, 2022).…”

Section: Methodsmentioning

confidence: 99%

Multi-purpose reservoir operation concomitant with estimating hydropower potential using multifarious hydrological models

Meskr,

Mohammed,

Ayalew

et al. 2024

Heliyon

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The performance of regional climate models driven by various general circulation models in reproducing observed rainfall over East Africa

Cited by 20 publications

References 66 publications

Understanding the Regionality and Diurnal Cycles of Precipitation in the Lake Victoria Basin during Boreal Fall

Understanding the Regionality and Diurnal Cycles of Precipitation in the Lake Victoria Basin during Boreal Fall

Coupled Model Intercomparison Project phase 6 evaluation and projection of East African precipitation

Multi-purpose reservoir operation concomitant with estimating hydropower potential using multifarious hydrological models

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