Projecting Temperature Climate Extremes at Regional to Urban Scales

The CELSIUS project aims to provide new climate change projections for Middle East/North Africa (MENA), including the eastern Mediterranean and Cyprus, at improved spatial precision and emphasis on temperature extremes and the warming over urban areas.

The WRF model was used as a regional climate model (RCM) to dynamically downscale, first, meteorological re-analyses from ECMWF in a series of multi-physics simulations over the MENA region. An optimal for this region WRF model configuration was obtained, by selecting the best performing (in comparison to observations) physical parametrisations set-up (with emphasis on the land surface and the boundary layer). This model set-up was used in multi-decadal simulations to downscale, to 24 km, for the recent past and the mid-21st century, climate fields from the CIMP5 global climate models forced by the RCP4.5 and RCP8.5 IPCC emissions scenarios (spefically, for 2, 3 and 4 degree Celsius global warming levels). The boundary conditions from the CCSM4 global climate model were selected among those CIMP5 models that represent more realistically temperature extremes during the recent past and predict the strongest heat extremes for the future. Another nested downscaling with the WRF followed, down to 16 km over the MENA region and down to 4 km over the eastern Mediterranean/Middle East (EMME) sub-region, with the bulk urban parameterization, in order take into account, at some degree, the urban heat island effect. The modelled urban heating was analysed for selected cities around the region (including Nicosia and Limassol for Cyprus) and especially in the context of humid heat conditions approaching the dangerous (30 Degrees Celsius) and intolerable (35 degrees Celsius) for humans levels of the wet-bulb temperature (an indicator of both warm and humid conditions).