engleski

Sensitivity of heavy precipitation to physical parameterizations in a regional climate model

Heavy precipitation affected the coastal mountainous region in Croatia during the first HyMeX Special Observation period in autumn 2012. The aim is to examine the impact of physical parameterization schemes of regional climate model (RCM) on heavy precipitation, an area in which research is still limited. For the parametrization tests we used daily precipitation from spectraly nudged RCM ALADIN-Climate version 6.3 (ALD6) driven by ERA-Interim reanalysis over the Med-CORDEX domain. Several simulations are carried out with parameter changes in convection scheme (entrainment and aerodynamical drag), microphysics, radiation, turbulence and dynamics. Precipitation analysis system MESCAN, avaliable on 5.5 km resolution every 6 h, was used as reference dataset. For the verification of the results a quality object-based measure SAL is used. SAL method takes into account the structure (S), the amplitude (A) and the location (L) of the precipitation field. Regardless the experiment or referent run, the SAL results are similar in terms of sign for S and A component, and ALD6 is overestimating the precipitation amount by creating too large and/or too flat objects. By tuning each parameter, in terms of a prior sensitivity to convection, the overall results show improvement of the L and S component, but A increases i.e. the overestimation of the precipitation amount increases. Still more experiments are needed to optimize the model performance over such complex terrain.

regional climate modeling, physical parameterizations, extreme precipitation

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