The dynamics of cyclones in the twentyfirst century: the Eastern Mediterranean as an example

Abstract

The Mediterranean region is projected to be significantly affected by climate change through warming and drying. The Eastern Mediterranean (EM) is particularly vulnerable since the bulk of the precipitation in the region is associated with a specific circulation pattern, known as Cyprus Low (CL). Here, we study the influence of increased greenhouse gases on the average properties and dynamics of CLs, using a regional semi-objective synoptic classification. The classification is applied to NCEP/NCAR reanalysis data for the present day (1986–2005) as well as to eight CMIP5 models for the present day and for the end of the century (2081–2100; RCP8.5). This is complemented by a dynamical systems analysis, which is used to investigate changes in the dynamics and intrinsic predictability of the CLs. Finally, a statistical downscaling algorithm, based on past analogues, is applied to eighteen rain stations over Israel, and is used to project precipitation changes associated with CLs. Significant changes in CL properties are found under climate change. The models project an increase in CL meridional pressure gradient (0.5–1.5 hPa/1000 km), which results primarily from a strong increase in the pressure over the southern part of the study region. Our results further point to a decrease in CL frequency (− 35%, as already noted in an earlier study) and persistence (− 8%). Furthermore, the daily precipitation associated with CL occurrences over Israel for 2081–2100 is projected to significantly reduce (− 26%). The projected drying over the EM can be partitioned between a decrease in CL frequency (~ 137 mm year−1) and a reduction in CL-driven daily precipitation (~ 67 mm year−1). The models further indicate that CLs will be less predictable in the future.