scholarly journals On the Fine-Scale Topography Regulating Changes in Atmospheric Hydrological Cycle and Extreme Rainfall over West Africa in a Regional Climate Model Projections

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
M. B. Sylla ◽  
A. T. Gaye ◽  
G. S. Jenkins
Keyword(s):  
West Africa ◽  
Regional Climate Model ◽  
Extreme Events ◽  
Large Scale ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
High Elevation ◽  
Climate Change Signal ◽  
Gulf Of Guinea

The ICTP-RegCM3 is used to downscale at 40 km projections from ECHAM5 over West Africa during the mid and late 21st Century. The results show that while ECHAM5 projects wetter climate along the Gulf of Guinea and drier conditions along the Sahel, RegCM3 produces contrasting changes for low-elevation (negative) and high-elevation (positive) terrains more marked during the second period. These wetter conditions in the uplands result from an intensification of the atmospheric hydrological cycle arising as a consequence of more frequent and denser rainy days and leading to larger intensity and more extreme events. Examination of the large-scale dynamics reveal that these conditions are mostly driven by increased low-level moisture convergence which produces elevated vertical motion above Cameroun’s mountainous areas favoring more atmospheric instability, moisture, and rainfall. This regulation of climate change signal by high-elevation terrains is feasible only in RegCM3 as the driving ECHAM5 is smoothing along all the Gulf of Guinea. This consolidates the need to use regional climate model to investigate the regional and local response of the hydrological cycle, the daily rainfall and extreme events to the increasing anthropogenic GHG warming for suitable impact studies specifically over region with complex topography such as West Africa.

scholarly journals A Nonlinear Response of Sahel Rainfall to Atlantic Warming

2013 ◽  
Vol 26 (18) ◽  
pp. 7080-7096 ◽  
Author(s):  
Naresh Neupane ◽  
Kerry H. Cook
Keyword(s):  
West Africa ◽  
Nonlinear Response ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Gulf Of Guinea ◽  
Easterly Wind ◽  
Low Level ◽  
Guinean Coast ◽  
Sahel Rainfall

Abstract The response over West Africa to uniform warming of the Atlantic Ocean is analyzed using idealized simulations with a regional climate model. With warming of 1 and 1.5 K, rainfall rates increase by 30%–50% over most of West Africa. With Atlantic warming of 2 K and higher, coastal precipitation increases but Sahel rainfall decreases substantially. This nonlinear response in Sahel rainfall is the focus of this analysis. Atlantic warming is accompanied by decreases in low-level geopotential heights in the Gulf of Guinea and in the large-scale meridional geopotential height gradient. This leads to easterly wind anomalies in the central Sahel. With Atlantic warming below 2 K, these easterly anomalies support moisture transport from the Gulf of Guinea and precipitation increases. With Atlantic warming over 2 K, the easterly anomalies reverse the westerly flow over the Sahel. The resulting dry air advection into the Sahel reduces precipitation. Increased low-level moisture provides moist static energy to initiate convection with Atlantic warming at 1.5 K and below, while decreased moisture and stable thermal profiles suppress convection with additional warming. In all simulations, the southerly monsoon flow onto the Guinean coast is maintained and precipitation in that region increases. The relevance of these results to the global warming problem is limited by the focus on Atlantic warming alone. However, confident prediction of climate change requires an understanding of the physical processes of change, and this paper contributes to that goal.

scholarly journals IMPACTS OF LAND COVER AND GREENHOUSE GAS (GHG) CONCENTRATION CHANGES ON THE HYDROLOGICAL CYCLE IN AMAZON BASIN: A REGIONAL CLIMATE MODEL STUDY

2015 ◽  
Vol 15 ◽  
Author(s):  
Vinícius Machado Rocha ◽  
Francis Wagner Silva Correia ◽  
Prakki Satyamurty ◽  
Saulo Ribeiro De Freitas ◽  
Demerval Soares Moreira ◽  
...  
Keyword(s):  
Land Cover ◽  
Regional Climate Model ◽  
Greenhouse Gas ◽  
Amazon Basin ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
Model Study ◽  
Concentration Changes

On the added value of the regional climate model REMO in the assessment of climate change signal over Central Africa

2017 ◽  
Vol 49 (11-12) ◽  
pp. 3813-3838 ◽  
Author(s):  
Thierry C. Fotso-Nguemo ◽  
Derbetini A. Vondou ◽  
Wilfried M. Pokam ◽  
Zéphirin Yepdo Djomou ◽  
Ismaïla Diallo ◽  
...  
Keyword(s):  
Climate Change ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Central Africa ◽  
Added Value ◽  
Climate Change Signal

scholarly journals Introducing an Irrigation Scheme to a Regional Climate Model: A Case Study over West Africa

2014 ◽  
Vol 27 (15) ◽  
pp. 5708-5723 ◽  
Author(s):  
Marc P. Marcella ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Heat Flux ◽  
Land Cover ◽  
West Africa ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Vegetation Model ◽  
Irrigation Scheme ◽  
Dynamic Vegetation Model ◽  
Niger River

Abstract This article presents a new irrigation scheme and biome to the dynamic vegetation model, Integrated Biosphere Simulator (IBIS), coupled to version 3 of the Regional Climate Model (RegCM3-IBIS). The new land cover allows for only the plant functional type (crop) to exist in an irrigated grid cell. Irrigation water (i.e., negative runoff) is applied until the soil root zone reaches relative field capacity. The new scheme allows for irrigation scheduling (i.e., when to apply water) and for the user to determine the crop to be grown. Initial simulations show a large sensitivity of the scheme to soil texture types, how the water is applied, and the climatic conditions over the region. Application of the new scheme is tested over West Africa, specifically Mali and Niger, to simulate the potential irrigation of the Niger River. A realistic representation of irrigation of the Niger River is performed by constraining the land irrigated by the annual flow of the Niger River and the amount of arable land in the region as reported by the Food and Agriculture Organization of the United Nations (FAO). A 30-yr simulation including irrigated cropland is compared to a 30-yr simulation that is identical but with no irrigation of the Niger. Results indicate a significant greening of the irrigated land as evapotranspiration over the crop fields largely increases—mostly via increases in transpiration from plant growth. The increase in the evapotranspiration, or latent heat flux (by 65–150 W m−2), causes a significant decrease in the sensible heat flux while surface temperatures cool on average by nearly 5°C. This cooling is felt downwind, where average daily temperatures outside the irrigation are reduced by 0.5°–1.0°C. Likewise, large increases in 2-m specific humidity are experienced across the irrigated cropland (on the order of 5 g kg−1) but also extend farther north and east, reflecting the prevailing surface southwesterlies. Changes (decreases) in rainfall are found only over the irrigated lands of west Mali. The decrease in rainfall can be explained by the large surface cooling and collapse of the boundary layer (by approximately 500 m). Both lead to a reduction in the triggering of convection as the convective inhibition, or negative buoyant energy, is never breached. Nevertheless, the new scheme and land cover allows for a novel line of research that can accurately reflect the effects of irrigation on climate and the surrounding environment using a dynamic vegetation model coupled to a regional climate model.

Internal variability in a regional climate model over West Africa

2007 ◽  
Vol 30 (2-3) ◽  
pp. 191-202 ◽  
Author(s):  
Emilie Vanvyve ◽  
Nicholas Hall ◽  
Christophe Messager ◽  
Stéphanie Leroux ◽  
Jean-Pascal van Ypersele
Keyword(s):  
West Africa ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Internal Variability

scholarly journals How Does a Regional Climate Model Modify the Projected Climate Change Signal of the Driving GCM: A Study over Different CORDEX Regions Using REMO

Atmosphere ◽  
2013 ◽  
Vol 4 (2) ◽  
pp. 214-236 ◽  
Author(s):  
Claas Teichmann ◽  
Bastian Eggert ◽  
Alberto Elizalde ◽  
Andreas Haensler ◽  
Daniela Jacob ◽  
...  
Keyword(s):  
Climate Change ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Climate Change Signal

scholarly journals Diagnosing Land–Atmosphere Interaction from a Regional Climate Model Simulation over West Africa

2010 ◽  
Vol 11 (2) ◽  
pp. 467-481 ◽  
Author(s):  
Bart J. J. M. van den Hurk ◽  
Erik van Meijgaard
Keyword(s):  
Soil Moisture ◽  
Regional Climate Model ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
West African ◽  
The West ◽  
Near Surface ◽  
Monsoon Area ◽  
Atmosphere Interaction

Abstract Land–atmosphere interaction at climatological time scales in a large area that includes the West African Sahel has been explicitly explored in a regional climate model (RegCM) simulation using a range of diagnostics. First, areas and seasons of strong land–atmosphere interaction were diagnosed from the requirement of a combined significant correlation between soil moisture, evaporation, and the recycling ratio. The northern edge of the West African monsoon area during June–August (JJA) and an area just north of the equator (Central African Republic) during March–May (MAM) were identified. Further analysis in these regions focused on the seasonal cycle of the lifting condensation level (LCL) and the convective triggering potential (CTP), and the sensitivity of CTP and near-surface dewpoint depressions HIlow to anomalous soil moisture. From these analyses, it is apparent that atmospheric mechanisms impose a strong constraint on the effect of soil moisture on the regional hydrological cycle.

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