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Abstract:
Driven by four global circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble (CNRM-CM5, GFDL-ESM2M, EC-EARTH, and MPI-ESM-LR), the future seasonal changes (2041-2060) of clear-air turbulence in five strength categories (light, light-to-moderate, moderate, moderate-to-severe, and severe) at three altitude levels (200 hPa, 250 hPa, and 300 hPa) over East Asia are projected with Regional Climate Model (RCM) Weather Research and Forecasting (WRF), as well as 21 clear-air turbulence diagnostics. The RCM simulations are carried out under the Representative Concentration Pathway 8.5 (RCP 8.5) scenario and the second phase of the Coordinated Regional Downscaling Experiment East Asia (CORDEX-EA-II) framework. Evaluation results show that RCM can well reproduce the spatial distribution of high-level climatological characteristics and clear-air turbulence diagnostics over East Asia at present climate background (1981-2000). Prediction results show that the stronger the turbulence strength categories, the more significant percentage changes in the occurrence frequency of the turbulence in each season; meanwhile, the most significant increment appears in winter, whereas the smallest increment appears in summer. The magnitude of turbulence increment is generally larger at 200 hPa and 250 hPa than at 300 hPa, decreasing magnitude with reducing altitude in summer and autumn, and largest/smallest magnitude at 250 hPa/300 hPa in spring and winter. The frequency increment in northern regions is more significant than in southern regions. Additionally, a more considerable increment appears in Northeast China than in Northwest China at all levels; however, it is a more significant increment in Southwest China than in Southeast China at 250 hPa and 300 hPa. It should be noted that the enhanced vertical wind shear in the mid-latitudes of East Asia in the future might be one of the important reasons for the increment of clear-air turbulence.
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