Abstract
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.
Highlights
The West African climate is influenced by the monsoon system, which is organized around key elements such as the monsoon flow in the lower layers, the African Easterly Jet (AEJ) in the middle layers, the Tropical
The Tropical Easterly Jet (TEJ) is a zonal wind generally located around 5–10◦ N; it is fed on a large scale by the Indian monsoon via the upper branch of Walker’s cell, and reinforced over Africa by the upper branch of Hadley’s cell [8,9]
We first validated the simulation of the standard version of the RegCM4 model before investigating the West African monsoon behavior in warm years
Summary
The West African climate is influenced by the monsoon system, which is organized around key elements such as the monsoon flow in the lower layers (a southwesterly wind), the African Easterly Jet (AEJ) in the middle layers (an east–west wind at 700 hPa), the Tropical. The Tropical Easterly Jet (TEJ) is a zonal wind generally located around 5–10◦ N; it is fed on a large scale by the Indian monsoon via the upper branch of Walker’s cell (zonal transport of energy, from east to west), and reinforced over Africa by the upper branch of Hadley’s cell [8,9]. It results from the thermal gradient between the Indian Ocean and Southeast Asia [10].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
