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 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 Feedback of observed interannual vegetation change: a regional climate model analysis for the West African monsoon

2016 ◽  
Vol 48 (9-10) ◽  
pp. 2837-2858 ◽  
Author(s):  
Cornelia Klein ◽  
Jan Bliefernicht ◽  
Dominikus Heinzeller ◽  
Ursula Gessner ◽  
Igor Klein ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Vegetation Change ◽  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
Model Analysis ◽  
West African ◽  
The West ◽  
African Monsoon

scholarly journals Improving the Simulation of the West African Monsoon Using the MIT Regional Climate Model

2014 ◽  
Vol 27 (6) ◽  
pp. 2209-2229 ◽  
Author(s):  
Eun-Soon Im ◽  
Rebecca L. Gianotti ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Regional Climate Model ◽  
Land Surface ◽  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
Convective Cloud ◽  
West African ◽  
The West ◽  
African Monsoon ◽  
Convection Schemes

Abstract This paper presents an evaluation of the performance of the Massachusetts Institute of Technology (MIT) regional climate model (MRCM) in simulating the West African monsoon. The MRCM is built on the Regional Climate Model, version 3 (RegCM3), but with several improvements, including coupling of Integrated Biosphere Simulator (IBIS) land surface scheme, a new surface albedo assignment method, new convective cloud and convective rainfall autoconversion schemes, and a modified scheme for simulating boundary layer height and boundary layer clouds. To investigate the impact of these more physically realistic representations when incorporated into MRCM, a series of experiments were carried out implementing two land surface schemes [IBIS with a new albedo assignment, and the Biosphere–Atmosphere Transfer Scheme (BATS)] and two convection schemes (Grell with the Fritsch–Chappell closure, and Emanuel in both the default form and modified with the new convective cloud cover and a rainfall autoconversion scheme). The analysis primarily focuses on comparing the rainfall characteristics, surface energy balance, and large-scale circulations against various observations. This work documents significant sensitivity in simulation of the West African monsoon to the choices of the land surface and convection schemes. Despite several deficiencies, the simulation with the combination of IBIS and the modified Emanuel scheme with the new convective cloud cover and a rainfall autoconversion scheme shows the best performance with respect to the spatial distribution of rainfall and the dynamics of the monsoon. The coupling of IBIS leads to representations of the surface energy balance and partitioning that show better agreement with observations compared to BATS. The IBIS simulations also reasonably reproduce the dynamical structures of the West African monsoon circulation.

scholarly journals Simulation of the West African monsoon onset using the HadGEM3-RA regional climate model

2014 ◽  
Vol 43 (3-4) ◽  
pp. 575-594 ◽  
Author(s):  
Ismaïla Diallo ◽  
Caroline L. Bain ◽  
Amadou T. Gaye ◽  
Wilfran Moufouma-Okia ◽  
Coumba Niang ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
West African Monsoon ◽  
Monsoon Onset ◽  
West African ◽  
The West ◽  
African Monsoon

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.

scholarly journals Coupling between the Atlantic cold tongue and the West African monsoon in boreal spring and summer

2011 ◽  
Vol 116 (C4) ◽  
Author(s):  
Guy Caniaux ◽  
Hervé Giordani ◽  
Jean-Luc Redelsperger ◽  
Françoise Guichard ◽  
Erica Key ◽  
...  
Keyword(s):  
West African Monsoon ◽  
West African ◽  
Cold Tongue ◽  
The West ◽  
African Monsoon ◽  
Boreal Spring ◽  
Atlantic Cold Tongue
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