Seasonal and Regional Patterns of Future Temperature Extremes: High‐Resolution Dynamic Downscaling Over a Complex Terrain

Abstract

The combined impacts of projected/simulated climate change and variability on temperature extremes over a complex topographical terrain along the eastern Mediterranean are assessed in this study. High-resolution dynamical temperature downscaling is conducted for the past (2008) and the near future (until 2050) during eight extreme hot and dry years under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5). The Weather Research and Forecasting (WRF) model is used for the downscaling process with two nested resolutions of 9 and 3 km, forced by the global High-Resolution Atmospheric Model (HiRAM) at a resolution of 25 km. Climate indices resultant from daily simulated temperature illustrate considerable changes in daily maximum summer and minimum winter temperature extremes during the future simulated years in comparison with the historic 2008 selected as reference and control period. While average yearly temperatures increase in both scenarios and most regions as expected, the seasonal variability is forecasted to intensify even more significantly resulting in colder winter and warmer summer conditions. Moreover, the interseasonal variability was most pronounced in the years with the highest averaged temperatures. A notable increase in the annual incidence of hot nights and heat wave events relative to 2008 conditions is also expected. The orographic complexity resulted in significant regional differences, with the most affected regions experiencing more than a doubling of extreme indices during the hottest and driest years of near-future decades. This strong spatial variability highlights the need for high-resolution downscaling.Intergovernmental Panel on Climate Change (IPCC) (2013) defines an extreme climatic event as one that is rare (i.e., falling on the extremes of a probability density function) at a particular place and time of year. In Key Points:• A downscaled GCM predicts exacerbated seasonal swings in Lebanon, including decreasing winter and spring temperatures and increasing temperature in summer and fall • Projections of increases in maximum summer temperatures and extreme heat indices are severe over the study area • Regional differences in impact over the focus area's complex terrain are very significant, require high-resolution downscaling El-Fadel, M. (2018). Seasonal and regional patterns of future temperature extremes: High-resolution dynamic downscaling over a complex terrain.

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