This study uses the International Center for Theoretical Physics(ICTP)Regional Climate Model version 5(RegCM5.0)to investigate the impact of the Fouta Djallon topography on the mean surface climate of West Africa with...This study uses the International Center for Theoretical Physics(ICTP)Regional Climate Model version 5(RegCM5.0)to investigate the impact of the Fouta Djallon topography on the mean surface climate of West Africa with a focus on the June–September(JJAS)season.Two experiments were conducted:a control simulation with current topography(REF)and a sensitivity simulation with flattened terrain(FLAT).Results show that reducing the elevation leads to decreased rainfall and increased temperatures,particularly over the Guinea Coast and the modified topographic region.Rainfall decreases by approximately 4.59%in the Guinea Coast sub-zone,while it slightly increases by about 2.76%in the Sahel.The most significant rainfall reduction,exceeding 20%,occurs over the flattened area.Temperature rises across both regions,with the strongest warming over the Fouta Jallon region.This pattern is likely due to the suppression of orographic uplift,which enhances the southwesterly monsoon flow from the Atlantic Ocean and causes a northward shift of the Intertropical Convergence Zone(ITCZ)into the Sahel.The findings highlight the key role of Fouta Jallon topography on the West African climate system.展开更多
Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature a...Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature and precipitation were analyzed. The purpose of this study is to assess the performance of RegCM4 coupled with the new CLM4.5 Land</span><span style="font-family:""> </span><span style="font-family:Verdana;">surface scheme and the standard one named BATS in order to find the best configuration of RegCM4 over West African. This study could improve our understanding of the sensitivity of land surface model in West Africa climate simulation, and provide relevant information to RegCM4 users. The results show fairly realistic restitution of West Africa’s climatology and indicate correlations of 0.60 to 0.82 between the simulated fields (BATS and CLM4.5) for precipitation. The substitution of BATS surface scheme by CLM4.5 in the model configuration, leads mainly to an improvement of precipitation over the Atlantic Ocean, however, the impact is not sufficiently noticeable over the continent. While the CLM4.5 experiment restores the seasonal cycles and spatial distribution, the biases increase for precipitation and temperature. Positive biases already existing with BATS are amplified over some sub-regions. This study concludes that temporal localization (seasonal effect), spatial distribution (grid points) and magnitude of precipitation and temperature (bias) are not simultaneously improved by CLM4.5. The introduction of the new land surface scheme CLM4.5, therefore, leads to a performance of the same order as that of BATS, albeit with a more detailed formulation.展开更多
基金supported by the Institut de Recherche pour le Développement (IRD), France (UMR IGE Imputation, Grant no. 252RA5)the Laboratoire Mixte International NEXUS (LMI-NEXUS) (Abidjan, Côte d'Ivoire)
文摘This study uses the International Center for Theoretical Physics(ICTP)Regional Climate Model version 5(RegCM5.0)to investigate the impact of the Fouta Djallon topography on the mean surface climate of West Africa with a focus on the June–September(JJAS)season.Two experiments were conducted:a control simulation with current topography(REF)and a sensitivity simulation with flattened terrain(FLAT).Results show that reducing the elevation leads to decreased rainfall and increased temperatures,particularly over the Guinea Coast and the modified topographic region.Rainfall decreases by approximately 4.59%in the Guinea Coast sub-zone,while it slightly increases by about 2.76%in the Sahel.The most significant rainfall reduction,exceeding 20%,occurs over the flattened area.Temperature rises across both regions,with the strongest warming over the Fouta Jallon region.This pattern is likely due to the suppression of orographic uplift,which enhances the southwesterly monsoon flow from the Atlantic Ocean and causes a northward shift of the Intertropical Convergence Zone(ITCZ)into the Sahel.The findings highlight the key role of Fouta Jallon topography on the West African climate system.
文摘Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature and precipitation were analyzed. The purpose of this study is to assess the performance of RegCM4 coupled with the new CLM4.5 Land</span><span style="font-family:""> </span><span style="font-family:Verdana;">surface scheme and the standard one named BATS in order to find the best configuration of RegCM4 over West African. This study could improve our understanding of the sensitivity of land surface model in West Africa climate simulation, and provide relevant information to RegCM4 users. The results show fairly realistic restitution of West Africa’s climatology and indicate correlations of 0.60 to 0.82 between the simulated fields (BATS and CLM4.5) for precipitation. The substitution of BATS surface scheme by CLM4.5 in the model configuration, leads mainly to an improvement of precipitation over the Atlantic Ocean, however, the impact is not sufficiently noticeable over the continent. While the CLM4.5 experiment restores the seasonal cycles and spatial distribution, the biases increase for precipitation and temperature. Positive biases already existing with BATS are amplified over some sub-regions. This study concludes that temporal localization (seasonal effect), spatial distribution (grid points) and magnitude of precipitation and temperature (bias) are not simultaneously improved by CLM4.5. The introduction of the new land surface scheme CLM4.5, therefore, leads to a performance of the same order as that of BATS, albeit with a more detailed formulation.
