scholarly journals Radiative and climatic effects of dust over West Africa, as simulated by a regional climate model

2012 ◽  
Vol 52 ◽  
pp. 97-113 ◽  
Author(s):  
F Solmon ◽  
N Elguindi ◽  
M Mallet
Keyword(s):  
West Africa ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Climatic Effects

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 Evaluation of the Rossby Centre Regional Climate Model Rainfall Simulations over West Africa Using Large-Scale Spatial and Temporal Statistical Metrics

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 802 ◽  
Author(s):  
Gnim Tchalim Gnitou ◽  
Tinghuai Ma ◽  
Guirong Tan ◽  
Brian Ayugi ◽  
Isaac Kwesi Nooni ◽  
...  
Keyword(s):  
West Africa ◽  
Boundary Conditions ◽  
Data Quality ◽  
Regional Climate Model ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Global Climate Models ◽  
Observational Uncertainty ◽  
Ensemble Mean

Climate models are usually evaluated to understand how well the modeled data reproduce specific application-related features. In Africa, where multisource data quality is an issue, there is a need to assess climate data from a general perspective to motivate such specific types of assessment, but mostly to serve as a basis for data quality enhancement activities. In this study, we assessed the Rossby Centre Regional Climate Model (RCA4) over West Africa without targeting any application-specific feature, while jointly evaluating its boundary conditions and accounting for observational uncertainties. Results from this study revealed that the RCA4 signal highly modifies the boundary conditions (global climate models (GCMs) and reanalysis data), resulting in a significant reduction of their biases in the dynamically downscaled outputs. The results, with respect to the observational ensemble members, are in line with the differences between the observation datasets. Among the RCA4 simulations, the ensemble mean outperformed all individual simulations regardless of the statistical metric and the reference data used. This indicates that the RCA4 adds value to GCMs over West Africa, with no influence of observational uncertainty, and its ensemble mean reduces model-related uncertainties.

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.

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