A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

Abstract

We used the regional climate model RegCM3 to investigate the role of the swamps of southern Sudan in affecting the climate of the surrounding region. Towards this end, we first assessed the performance of a high resolution version of the model over northern Africa. RegCM3 shows a good skill in simulating the climatology of rainfall and temperature patterns as well as the related circulation features during the summer season, outperforming previous coarser resolution applications of the model over this region. Sensitivity experiments reveal that, relative to bare soil conditions, the swamps act to locally modify the surface energy budget primarily through an increase of surface latent heat flux. Existence of the swamps leads to lower ground temperature (up to 2°C), a larger north-south temperature gradient, and increased local rainfall (up to 40 %). Of particular importance is the impact on rainfall in the surrounding regions. The swamps have almost no impact on the rainfall over the source region of the Nile in Ethiopia or in the Sahel region; however, they favor wetter conditions over central Sudan (up to 15 %) in comparison to the bare desert soil conditions.

Simulating the connections of ENSO and the rainfall regime of East Africa and the upper Blue Nile region using a climate model of the Tropics

“…Also, the monsoon rain belt appears narrower in the model than in the observational data sets, as indicated by the negative precipitation biases north and south of the main rain belt. In general, the performance of our Reg-TB configuration appears to be in line with previous studies performed using the RegCM system in various configurations and domains (Sun et al, 1999;Pal et al, 2007;Anyah and Semazzi, 2007;Sylla et al, 2010b;Steiner et al, 2009;Zaroug et al, 2013) or with other regional modelling systems (e.g., Vizy and Cook, 2002;Nikulin et al, 2012;Paeth et al, 2005;Gallée et al, 2004;Flaounas et al, 2010;Druyan et al, 2008).…”

“…The model tends to overestimate the OLR over the Congo Basin (Fig. 4b) as a result of an underestimation of cloudiness over this region, a result which is in line with previous applications of the model (Zaroug et al, 2013;Sylla et al, 2010a, b). Slight overestimates are found over the Sahara and the Greater Horn of Africa (Fig.…”

“…For example, the model captured well the rain belt, as well as the peaks over the Ethiopian, Guinea and Cameroon Highlands. In fact, this simulation even outperformed in some aspects previous applications of this model over the region (Sylla et al, 2010b, Zaroug et al, 2013. In addition, the lower-level and largescale circulation features affecting the monsoon (TEJ, AEJ) were realistically captured.…”

The Impact of Climate Change on Water Resource Availability in a Trans-Boundary Basin in West Africa: The Case of Sassandra

“…The basic strategy has been to use the GCMs to simulate the response of the global circulation to large-scale forcings and the RCM to (a) account for sub-GCM grid scale forcings (e.g., complex topographical features and land cover heterogeneities) in a physically based way and (b) enhance the simulation of atmospheric circulations and climatic variables at fine spatial scales. This technique therefore constitutes the most appropriate tool to generate regional climate change data for West Africa and has been used extensively over the region (e.g., [30][31][32][33][34]). For more details about the CMIP5 models, see Taylor et al [35].…”

Simulation of present-day precipitation over India using a regional climate model

“…In fact, most of the studies have focused on mean precipitation climatology, examining in particular the ability of RCMs to improve, variability, interactions between the different dynamical features affecting the monsoon, land use changes, fine-scale topography, monsoon circulation, and El Niño Southern Oscillation (ENSO) dynamics on future climate over monsoonal (Paeth et al 2009;Sylla et al 2009Sylla et al , 2012Mariotti et al 2011;Zaroug et al 2013) areas.…”