scholarly journals West African Monsoon in State-of-the-Science Regional Climate Models

10.5772/55140 ◽  
2013 ◽  
Author(s):  
M. B. ◽  
I. Diallo ◽  
J. S.
Keyword(s):  
Climate Models ◽  
Regional Climate ◽  
West African Monsoon ◽  
Regional Climate Models ◽  
West African ◽  
African Monsoon ◽  
State Of The Science

scholarly journals Influence of the representation of convection on the mid-Holocene West African Monsoon

2021 ◽  
Vol 17 (4) ◽  
pp. 1665-1684
Author(s):  
Leonore Jungandreas ◽  
Cathy Hohenegger ◽  
Martin Claussen
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Monsoon Season ◽  
West African Monsoon ◽  
West African ◽  
Global Climate Models ◽  
African Monsoon ◽  
Monsoonal Precipitation

Abstract. Global climate models experience difficulties in simulating the northward extension of the monsoonal precipitation over north Africa during the mid-Holocene as revealed by proxy data. A common feature of these models is that they usually operate on grids that are too coarse to explicitly resolve convection, but convection is the most essential mechanism leading to precipitation in the West African Monsoon region. Here, we investigate how the representation of tropical deep convection in the ICOsahedral Nonhydrostatic (ICON) climate model affects the meridional distribution of monsoonal precipitation during the mid-Holocene by comparing regional simulations of the summer monsoon season (July to September; JAS) with parameterized and explicitly resolved convection. In the explicitly resolved convection simulation, the more localized nature of precipitation and the absence of permanent light precipitation as compared to the parameterized convection simulation is closer to expectations. However, in the JAS mean, the parameterized convection simulation produces more precipitation and extends further north than the explicitly resolved convection simulation, especially between 12 and 17∘ N. The higher precipitation rates in the parameterized convection simulation are consistent with a stronger monsoonal circulation over land. Furthermore, the atmosphere in the parameterized convection simulation is less stably stratified and notably moister. The differences in atmospheric water vapor are the result of substantial differences in the probability distribution function of precipitation and its resulting interactions with the land surface. The parametrization of convection produces light and large-scale precipitation, keeping the soils moist and supporting the development of convection. In contrast, less frequent but locally intense precipitation events lead to high amounts of runoff in the explicitly resolved convection simulations. The stronger runoff inhibits the moistening of the soil during the monsoon season and limits the amount of water available to evaporation in the explicitly resolved convection simulation.

scholarly journals Investigating West African Monsoon Features in Warm Years Using the Regional Climate Model RegCM4

Atmosphere ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 23 ◽  
Author(s):  
Ibrahima Diba ◽  
Moctar Camara ◽  
Arona Diedhiou
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
West African ◽  
Heat Fluxes ◽  
Guinea Coast ◽  
African Monsoon ◽  
Model Driven ◽  
Warm Spell

This study investigates the changes in West African monsoon features during warm years using the Regional Climate Model version 4.5 (RegCM4.5). The analysis uses 30 years of datasets of rainfall, surface temperature and wind parameters (from 1980 to 2009). We performed a simulation at a spatial resolution of 50 km with the RegCM4.5 model driven by ERA-Interim reanalysis. The rainfall amount is weaker over the Sahel (western and central) and the Guinea region for the warmest years compared to the coldest ones. The analysis of heat fluxes show that the sensible (latent) heat flux is stronger (weaker) during the warmest (coldest) years. When considering the rainfall events, there is a decrease of the number of rainy days over the Guinea Coast (in the South of Cote d’Ivoire, of Ghana and of Benin) and the western and eastern Sahel during warm years. The maximum length of consecutive wet days decreases over the western and eastern Sahel, while the consecutive dry days increase mainly over the Sahel band during the warm years. The percentage of very warm days and warm nights increase mainly over the Sahel domain and the Guinea region. The model also simulates an increase of the warm spell duration index in the whole Sahel domain and over the Guinea Coast in warm years. The analysis of the wind dynamic exhibits during warm years a weakening of the monsoon flow in the lower levels, a strengthening in the magnitude of the African Easterly Jet (AEJ) in the mid-troposphere and a slight increase of the Tropical Easterly Jet (TEJ) in the upper levels of the atmosphere during warm years.

scholarly journals Dynamics of the West African Monsoon Jump

2007 ◽  
Vol 20 (21) ◽  
pp. 5264-5284 ◽  
Author(s):  
Samson M. Hagos ◽  
Kerry H. Cook
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
Lower Troposphere ◽  
West African ◽  
Moisture Convergence ◽  
The West ◽  
African Monsoon ◽  
Sahel Region ◽  
Continental Interior

Abstract The observed abrupt latitudinal shift of maximum precipitation from the Guinean coast into the Sahel region in June, known as the West African monsoon jump, is studied using a regional climate model. Moisture, momentum, and energy budget analyses are used to better understand the physical processes that lead to the jump. Because of the distribution of albedo and surface moisture, a sensible heating maximum is in place over the Sahel region throughout the spring. In early May, this sensible heating drives a shallow meridional circulation and moisture convergence at the latitude of the sensible heating maximum, and this moisture is transported upward into the lower free troposphere where it diverges. During the second half of May, the supply of moisture from the boundary layer exceeds the divergence, resulting in a net supply of moisture and condensational heating into the lower troposphere. The resulting pressure gradient introduces an inertial instability, which abruptly shifts the midtropospheric meridional wind convergence maximum from the coast into the continental interior at the end of May. This in turn introduces a net total moisture convergence, net upward moisture flux and condensation in the upper troposphere, and an enhancement of precipitation in the continental interior through June. Because of the shift of the meridional convergence into the continent, condensation and precipitation along the coast gradually decline. The West African monsoon jump is an example of multiscale interaction in the climate system, in which an intraseasonal-scale event is triggered by the smooth seasonal evolution of SSTs and the solar forcing in the presence of land–sea contrast.

Land surface coupling in regional climate simulations of the West African monsoon

2009 ◽  
Vol 33 (6) ◽  
pp. 869-892 ◽  
Author(s):  
Allison L. Steiner ◽  
Jeremy S. Pal ◽  
Sara A. Rauscher ◽  
Jason L. Bell ◽  
Noah S. Diffenbaugh ◽  
...  
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
West African Monsoon ◽  
West African ◽  
The West ◽  
African Monsoon ◽  
Climate Simulations ◽  
Surface Coupling

scholarly journals West African monsoon precipitation impacted by the South Eastern Atlantic biomass burning aerosol outflow

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
F. Solmon ◽  
N. Elguindi ◽  
M. Mallet ◽  
C. Flamant ◽  
P. Formenti
Keyword(s):  
Biomass Burning ◽  
Climate Modeling ◽  
Global Climate ◽  
Regional Climate ◽  
Regional Scale ◽  
West African Monsoon ◽  
Regional Climate Modeling ◽  
West African ◽  
African Monsoon ◽  
Low Cloud

AbstractThe West African Monsoon (WAM) is a complex system depending on global climate influences and multiple regional environmental factors. Central and Southern African biomass-burning (SABB) aerosols have been shown to perturb WAM during episodic northward inter-hemispheric transport events, but a possible dynamical connection between the core of the SABB aerosol outflow and the WAM system remains unexplored. Through regional climate modeling experiments, we show that SABB aerosols can indeed impact WAM dynamics via two competitive regional scale and inter-hemispheric dynamical feedbacks originating from (i) enhanced diabatic heating occurring in the Southeastern Atlantic low-cloud deck region, and (ii) aerosol and cloud-induced sea surface temperature cooling. These mechanisms, related to aerosol direct, semi-direct, and indirect effects, are shown to have different seasonal timings, resulting in a reduction of June to September WAM precipitation, while possibly enhancing late-season rainfall in WAM coastal areas.

scholarly journals West African Monsoon (WAM) and Atlantic Cold Tongue (ACT) onsets using Regional Climate Model

2017 ◽  
Vol 12 (15) ◽  
pp. 142-154
Author(s):  
Benjamin KOUASSI K. ◽  
DIAWARA Adama ◽  
Yves KOUADIO K. ◽  
YOROBA Fidele ◽  
TOUALY Elisee
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
West African ◽  
Cold Tongue ◽  
African Monsoon ◽  
Atlantic Cold Tongue

scholarly journals Understanding the West African Monsoon from the analysis of diabatic heating distributions as simulated by climate models

2017 ◽  
Vol 9 (1) ◽  
pp. 239-270 ◽  
Author(s):  
G. M. Martin ◽  
P. Peyrillé ◽  
R. Roehrig ◽  
C. Rio ◽  
M. Caian ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Climate Models ◽  
West African Monsoon ◽  
West African ◽  
The West ◽  
African Monsoon
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