Global and regional climate predictions

Contributions: UiO (WP Leader: Berntsen), ICTP, collaborating institutes in Subequatorial Africa
Main purpose: Produce and assess high resolution climate change projections for sub-equatorial Africa, with emphasis on changes in temperature, precipitation and the hydrologic cycle. Existing projections for Africa are mostly based on global climate models with coarse resolution (MMD dataset, see above). We will improve the projections by going to finer resolution. Furthermore, we will also improve aerosol-cloud interactions.
The main bulk of WP1 will be devoted to the completion of projections of future climate to be used as input by the hydrological model in WP2. First we will test a new aerosol-cloud scheme for ice clouds (Storelvmo et al., 2008) in CAM3-Oslo, which are important in the formation of precipitation in sub-equatorial Africa. We will then complete some selected global time-slice simulations with CAM4 at relatively high resolution for the period 1990-2030 using prescribed sea surface temperatures (SST) from the IPCC scenario runs. We will use  0.9°x1.25° resolution for the CAM4 model simulations. We will use SSTs from the A1B emission scenario experiments conducted with the CCSM in the IPCC AR4 dataset. Since the different scenarios yield similar results for climate projections until 2030 (IPCC, 2007a), which is the year of focus in SoCoCA, the choice of scenario is not critical. Next we will run the RegCM3 model to downscale the CAM4 results. The downscaling is important to take into account regional topographic, land use and aerosol effects properly and to provide the input data for the hydrological model on a spatial scale more consistent for modelling hydrological catchments. The RegCM3 will be run for the entire sub-equatorial African continent at a 25 km resolution. Finally we will further zoom in on a limited region, which is the region to be studied also in WP2, WP3 and WP4, including Malawi, Botswana and areas of South Africa at a model resolution of 10 km resolution that will be used as input to the hydrological model.

Activities and milestones:

1.1: Sensitivity tests of improved aerosol-cloud scheme for ice clouds in CAM3-Oslo
1.2: Temperature and precipitation distributions for Africa based on a CAM4 and CAM3-Oslo for the period 1990-2030 adopting one of the IPCC emission scenarios (most likely A1B)
1.3: Temperature and precipitation distributions for sub-equatorial Africa based on the RegCM3 at 25 km resolution
1.4: Temperature and precipitation distributions for Malawi, Botswana and areas of South Africa based on the RegCM3 at 10 km resolution