Characterization of the rainy season in Burkina Faso and it’s representation by regional climate models

Abstract

West African monsoon is one of the most challenging climate components to model. Five regional climate models (RCMs) were run over the West African region with two lateral boundary conditions, ERA-Interim re-analysis and simulations from two general circulation models (GCMs). Two sets of daily rainfall data were generated from these boundary conditions. These simulated rainfall data are analyzed here in comparison to daily rainfall data collected over a network of ten synoptic stations in Burkina Faso from 1990 to 2004. The analyses are based on a description of the rainy season throughout a number of it's characteristics. It was found that the two sets of rainfall data produced with the two driving data present significant biases. The RCMs generally produce too frequent low rainfall values (between 0.1 and 5 mm/ day) and too high extreme rainfalls (more than twice the observed values). The high frequency of low rainfall events in the RCMs induces shorter dry spells at the rainfall thresholds of 0.1-1 mm/day. Altogether, there are large disagreements between the models on the simulate season duration and the annual rainfall amounts but most striking are their differences in representing the distribution of rainfall intensity. It is remarkable that these conclusions are valid whether the RCMs are driven by re-analysis or GCMs. In none of the analyzed rainy season characteristics, a significant improvement of their representation can be found when the RCM is forced by the re-analysis, indicating that these deficiencies are intrinsic to the models.

Hydrological Impacts of the Changes in Simulated Rainfall Fields on Nakanbe Basin in Burkina Faso

“…Nakanbe basin covers a surface of about 15% of Burkina Faso (44,000 km 2 ) and overlaps the central part of the country from the North to the South (Figure 1). The basin is distributed over the three main climate zones that characterized Burkina Faso climate: the Sahelian climate with annual rainfall amount between 300 mm and 600 mm, the Sub-Sahelian climate with annual rainfall amount between 600 and 900 mm and the north Sudanese climate with annual rainfall amount between 900 mm and 1200 mm [14]. Our study focuses on the Sahelian part of the basin (an area of about 22,000 km 2 ), which constitutes the upstream of Wayen hydrometric station ( Figure 1).…”

“…The data are constituted with rainfall, temperature, and the potential evapotranspiration. The interpolated climate data at the spatial resolution of 0.5° × 0.5° over 1971-2009 period comes from four data sources: IRD, CRU [23], WATCH [24] and in situ data (observations) from the ten synoptic stations of Burkina Faso [14]. The observed data from the synoptic stations concerned the main climate parameters (rainfall, temperature, humidity, insolation and wind) and cover the period from 1961 to 2009.…”

“…An assessment of the representativeness [23] of all the interpolated or processed data (IRD, CRU, WATCH) showed that these data are relevant in the region. The climate simulations are produced by five regional climate models (RCMs) run under the intermediate climate change scenario of A1B over the 1961-2050 period [14]: CCLM, HadRM3P, RACMO, RCA and REMO. The simulations have been done by ESEMBLE in the framework of AMMA (African Monsoon Multidisciplinary Analysis) [14].…”

“…The climate simulations are produced by five regional climate models (RCMs) run under the intermediate climate change scenario of A1B over the 1961-2050 period [14]: CCLM, HadRM3P, RACMO, RCA and REMO. The simulations have been done by ESEMBLE in the framework of AMMA (African Monsoon Multidisciplinary Analysis) [14]. The daily simulated data at the spatial resolution of 50 km × 50 km are available for free download at the ENSEMBLE data portail [25].…”

“…On the other hand, climate change conditions over the future period under the different IPCC scenarios [13] is expected to modify the rainfall regime over the Sahel [14]. However, the changes in annual rainfall amount (the main characteristic of the rainy season) over the West African Sahel for the horizon of the 2050s in comparison to the 1961-2000 period depend on the climate models [15][16][17][18].…”