High‐resolution regional climate modeling for the Volta region of West Africa

Abstract

[1] The Volta region is a climate-sensitive semiarid to subhumid region in West Africa. To investigate the impact of expected global climate change on regional water availability, regional climate modeling was performed. Two time slices (1991-2000 and 2030-2039) of the ECHAM4 scenario IS92a were dynamically downscaled with MM5 to a spatial resolution of 9 km. The quality of MM5 simulations in reproducing regional climate was assessed using reanalysis data for initial and boundary conditions. Although an underestimation of coastal rainfall was detected, sufficient accuracy in the Volta Basin could be achieved. The regional climate simulations show an annual mean temperature increase of 1.2-1.3°C in the Volta region. This temperature change significantly exceeds interannual variability. A mean annual change in precipitation from À20% to +50% ($ À150 to +200 mm) is simulated, with a spatial mean increase of 5% ($45 mm). In the rainy season, rainfall predominantly increases, whereas a strong decrease is found for April, which is connected to a delay in the onset of the rainy season. In addition, interannual variability in the Volta region increases in the early stage of the rainy season. The climate change signals in infiltration excess and evapotranspiration show a nonlinear response to precipitation change. Aridity, expressed by the de Martonne aridity index, does not change significantly. The change signal in precipitation predominantly lies within the range of interannual variability. In contrast, the decrease in April exceeds interannual variability in the Sahel region.Citation: Jung, G., and H. Kunstmann (2007), High-resolution regional climate modeling for the Volta region of West Africa,

Smallholder adaptation to climate change: dynamics and limits in Northern Ghana

“…Climate models for the region project that the shift in the onset of the rainy season will continue further in the coming decades. According to these projections, between 2030 and 2039 the rainy season might only start in June or even later in Northern Ghana (Jung and Kunstmann 2007). For Northern Ghana and Southern Burkina Faso (Laux et al 2008: 130), it is estimated that the average onset of the rainy season 2 may shift from the 140th day (estimated average for to up to the 171st day (estimated average for 2001-2040) of the Julian calendar.…”

The WASCAL high-resolution regional climate simulation ensemble for West Africa: concept, dissemination and assessment

“…First high-resolution RCM studies over West Africa were conducted by Jung and Kunstmann (2007) using the mesoscale meteorological model MM5 (Grell et al, 1994) at 9 km resolution for two time slices, 1991-2000 and 2030-2039, over a comparably small region covering the Volta Basin. They showed an annual mean temperature increase of around 1.3 • C in the Volta region, significantly exceeding the interannual variability, and a mean annual change in precipitation from −20 to +50 %.…”

The WASCAL high-resolution regional climate simulation ensemble for West Africa: concept, dissemination, assessment

“…Uncertainties also 30 rise from the sparse observational network and the considerable differences in the derived gridded observation products for the region, against which models are validated and calibrated (Sylla et al, 2013). First high-resolution RCM studies over West Africa were conducted by Jung and Kunstmann (2007) using the mesoscale meteorological model MM5 (Grell et al, 1994) at 9 km resolution for two time slices 1991-2000 and 2030-2039 over a comparably small region covering the Volta Basin. They showed an annual mean temperature increase of around 1.3…”