scholarly journals Sensitivity study of the Regional Climate Model RegCM4 to different convective schemes over West Africa

2018 ◽  
Author(s):  
Brahima Koné ◽  
Arona Diedhiou ◽  
N'datchoh Evelyne Touré ◽  
Mouhamadou Bamba Sylla ◽  
Filippo Giorgi ◽  
...  
Keyword(s):  
West Africa ◽  
Land Surface ◽  
Climate Model ◽  
West African ◽  
Climate System ◽  
Surface Model ◽  
Spatial And Temporal Variability ◽  
The West ◽  
Taylor Diagram ◽  
African Climate

Abstract. The latest version of RegCM4 with CLM4.5 as land surface scheme was used to assess the performance and the sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West Africa domain from November 2002 to December 2004, at spatial resolution of 50 km × 50 km and involved five (5) convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using respectively data from the Climate Research Unit (CRU) and Global Precipitation Climatology Project (GPCP) during June to September (rainy season). Quantitative assessment of the sensitivity tests were carried out using the mean bias, the pattern correlation coefficient, the root mean square difference, the probability density function of the temperature bias and the Taylor diagram. Results revealed a better performance of the configuration with Emanuel convection scheme to simulate the spatial and temporal variability of the temperature and the precipitation. Therefore, the configuration of RegCM4 with CLM4.5 as land surface model and implementing Emanuel convective scheme is recommended for the study of the West African climate system.

scholarly journals Sensitivity study of the regional climate model RegCM4 to different convective schemes over West Africa

2018 ◽  
Vol 9 (4) ◽  
pp. 1261-1278 ◽  
Author(s):  
Brahima Koné ◽  
Arona Diedhiou ◽  
N'datchoh Evelyne Touré ◽  
Mouhamadou Bamba Sylla ◽  
Filippo Giorgi ◽  
...  
Keyword(s):  
West Africa ◽  
Land Surface ◽  
West African ◽  
Cold Bias ◽  
The West ◽  
Land Surface Scheme ◽  
African Climate ◽  
Sensitivity Studies ◽  
Surface Scheme ◽  
Convective Scheme

Abstract. The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system.

scholarly journals Advances in Climate Processes, Feedbacks, Variability and Change for the West African Climate System

2012 ◽  
Vol 2012 ◽  
pp. 1-3
Author(s):  
Gregory S. Jenkins ◽  
Alessandra Giannini ◽  
Amadou Gaye ◽  
Andrea Sealy
Keyword(s):  
West African ◽  
Climate System ◽  
The West ◽  
African Climate

scholarly journals Review of Recent Developments and the Future Prospective in West African Atmosphere/Land Interaction Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Yongkang Xue ◽  
Aaron Boone ◽  
Christopher M. Taylor
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
West African ◽  
Surface Processes ◽  
Surface Model ◽  
African Region ◽  
Land Surface Processes ◽  
Interaction Studies ◽  
African Climate ◽  
The Future

This paper reviews West African land/atmosphere interaction studies during the past decade. Four issues are addressed in this paper: land data development, land/atmosphere interactions at seasonal-interannual scales, mesoscale studies, and the future prospective. The development of the AMMA Land Surface Model Intercomparison Project has produced a valuable analysis of the land surface state and fluxes which have been applied in a number of large-scale African regional studies. In seasonal-interannual West African climate studies, the latest evidence from satellite data analyses and modeling studies confirm that the West African region has a climate which is particularly sensitive to land surface processes and there is a strong coupling between land surface processes and regional climate at intraseasonal/seasonal scales. These studies indicate that proper land surface process representations and land status initialization would substantially improve predictions and enhance the predictability of West African climate. Mesoscale studies have revealed new understanding of how soil moisture heterogeneity influences the development of convective storms over the course of the diurnal cycle. Finally, several important issues regarding the future prospective are briefly addressed.

The response of land-atmosphere interactions and the atmospheric circulation across West Africa to intraseasonal variability

2021 ◽  
Author(s):  
Joshua Talib ◽  
Christopher Taylor ◽  
Cornelia Klein ◽  
Bethan L. Harris ◽  
Seonaid R. Anderson ◽  
...  
Keyword(s):  
West Africa ◽  
Land Surface ◽  
Rainfall Variability ◽  
Regional Scale ◽  
West African Monsoon ◽  
Precipitation Variability ◽  
West African ◽  
Monsoon Circulation ◽  
The West ◽  
Surface Response

<p>Across West Africa rain-fed agriculture fulfils approximately 80% of the food needs of the population and employs 60% of the workforce. It is therefore critical to understand the effects of intraseasonal rainfall variability across West Africa. Previous work has shown that land-atmosphere interactions across West Africa can influence daily variability in deep convection characteristics and the impact of 10-25 day precipitation variability. Using earth observations and reanalyses, this study investigates the land surface response to 20-200 day precipitation variability and its impact on land-atmosphere interactions and the West African monsoon.</p><p>                Surprisingly, even though the sensitivity of the land surface across the Sahel to strong convection is short-lived (days) and daily precipitation patterns are strongly heterogeneous, a coherent regional-scale land surface response to 20-200 day precipitation variability is observed. This sensitivity of the land surface affects land-atmosphere interactions on a regional scale and perturbs the West African monsoon circulation. For example, during sub-seasonal periods of low rainfall, soil moisture significantly decreases across the Sahel and land surface temperatures increase by up to 2°C. Surface drying and warming across the Sahel is associated with an intensified heat low and a northward shift of low-level monsoon westerlies. During periods of high rainfall, the surface moistens and cools, which is associated with a high pressure tendency across the Sahel. This high pressure tendency dampens the heat low circulation across West Africa and reduces regional moisture fluxes. We show that the land surface response to 20-200 day rainfall variability across West Africa can have a significant impact on the monsoon circulation. This suggests that improving the representation of land-surface processes across West Africa has the potential to improve sub-seasonal forecast predictability and enhance early warning systems.</p>

scholarly journals The West African climate system: a review of the AMMA model inter-comparison initiatives

2011 ◽  
Vol 12 (1) ◽  
pp. 116-122 ◽  
Author(s):  
P. M. Ruti ◽  
J. E. Williams ◽  
F. Hourdin ◽  
F. Guichard ◽  
A. Boone ◽  
...  
Keyword(s):  
West African ◽  
Climate System ◽  
The West ◽  
System A ◽  
African Climate

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 The Effects of Satellite-Derived Vegetation Cover Variability on Simulated Land–Atmosphere Interactions in the NAMS

2005 ◽  
Vol 18 (1) ◽  
pp. 21-40 ◽  
Author(s):  
Toshihisa Matsui ◽  
Venkataraman Lakshmi ◽  
Eric E. Small
Keyword(s):  
Soil Moisture ◽  
Vegetation Cover ◽  
Land Surface ◽  
Vegetation Index ◽  
Climate Model ◽  
Monsoon Season ◽  
Stress Index ◽  
Surface Model ◽  
Spatial And Temporal Variability ◽  
Moist Convection

Abstract Substantial evolution of Normalized Difference Vegetation Index (NVDI)-derived vegetation cover (Fg) exists in the southwestern United States and Mexico. The intraseasonal and wet-/dry-year fluctuations of Fg are linked to observed precipitation in the North American monsoon system (NAMS). The manner in which the spatial and temporal variability of Fg influences the land–atmosphere energy and moisture fluxes, and associated likelihood of moist convection in the NAMS regions, is examined. For this, the regional climate model (RCM) is employed, with three different Fg boundary conditions to examine the influence of intraseasonal and wet-/dry-year vegetation variability. Results show that a strong link exists between evaporative fraction (EF), surface temperature, and relative humidity in the boundary layer (BL), which is consistent with a positive soil moisture feedback. However, contrary to expectations, higher Fg does not consistently enhance EF across the NAMS region. This is because the low soil moisture values simulated by the land surface model (LSM) yield high canopy resistance values throughout the monsoon season. As a result, the experiment with the lowest Fg yields the greatest EF and precipitation in the NAMS region, and also modulates regional atmospheric circulation that steers the track of tropical cyclones. In conclusion, the simulated influence of vegetation on land–atmosphere exchanges depends strongly on the canopy stress index parameterized in the LSM. Therefore, a reliable dataset, at appropriate scales, is needed to calibrate transpiration schemes and to assess simulated and realistic vegetation–atmosphere interactions in the NAMS region.

scholarly journals Sensitivity of the West African hydrological cycle in ORCHIDEE to infiltration processes

2008 ◽  
Vol 12 (6) ◽  
pp. 1387-1401 ◽  
Author(s):  
T. d'Orgeval ◽  
J. Polcher ◽  
P. de Rosnay
Keyword(s):  
Sensitivity Analysis ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Land Surface Model ◽  
West African ◽  
Surface Model ◽  
Deep Soil ◽  
The West ◽  
Semi Arid ◽  
Infiltration Processes

Abstract. The aim of this article is to test the sensitivity of the West African hydrological cycle to infiltration processes and to river reinfiltration pathways. This is done through sensitivity experiments to both inputs and paramterization settings of the ORCHIDEE Land-Surface Model. The parameterizations to take into account the effects of flat areas, ponds and floodplains on surface infiltration, and the effect of roots and deep-soil compactness on infiltration are first described. The sensitivity analysis to parameterization settings shows that the surface infiltration processes have a stronger impact in the soudano-sahelian region and more generally in semi-arid African regions, whereas the rootzone and deep-soil infiltration also play a role in the guinean and intermediate regions between arid and humid ones. In the equatorial and semi-humid regions, infiltration processes generally play a minor role. The infiltration parameterizations may explain part of the difference between simulated and observed river discharge in semi-arid and intermediate basins. The sensitivity analysis to the Land-Surface Model inputs shows that different sources of uncertainty might also explain part of the error. Indeed, the precipitation forcing in the whole West African region, the long-term storage in the soudano-sahelian region, the soil types in the guinean region and the vegetation types in the equatorial region are significant sources of errors. Therefore, observations and analyses of small scale infiltration processes as well as continuous measurements of river discharges in West Africa are essential to ensure the reliability of future calibration for the infiltration parameterizations.

Investigating the West African Climate System Using Global/Regional Climate Models

2002 ◽  
Vol 83 (4) ◽  
pp. 583-595 ◽  
Author(s):  
Gregory S. Jenkins ◽  
Andre Kamga ◽  
Adamou Garba ◽  
Arona Diedhiou ◽  
Vernon Morris ◽  
...  
Keyword(s):  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Models ◽  
West African ◽  
Climate System ◽  
The West ◽  
African Climate
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