Abstract
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.
Highlights
Agriculture in West Africa relies mainly on rainfall and is strongly dependent on the West African monsoon
The onset, cessation and the amount of expected precipitation associated with the West African monsoon are of great importance for farmers, and accurate simulation and prediction of rainfall and temperature are crucial for various sectors, such as agriculture, energy and health, and for decisionmakers
This study investigates the performance of RegCM4CLM4.5 over West Africa using different convection schemes to identify the “best” configuration option for the region
Summary
Agriculture in West Africa relies mainly on rainfall and is strongly dependent on the West African monsoon. Compared with the previous version (RegCM3; Pal et al, 2007), the latest release (RegCM4) has been improved with substantial development of the software code and the physical representations (Giorgi et al, 2012) and with the introduction of CLM (version 3.5 and 4.5) as an option to describe land surface processes It was the Biosphere–Atmosphere Transfer Scheme (BATS; Dickinson et al, 1993) only that was used as a land surface model. Komkoua et al (2016) found that the last release of RegCM implementing Grell as a convective scheme with the Arakawa–Schubert closure assumption is more suitable to downscale the diurnal cycle of rainfall over Central Africa None of these studies have attempted to investigate a sensitivity study of the regional climate model RegCM4 to the convective scheme over West Africa with CLM4.5 as the land surface model.
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