engleski

Heavy precipitation events and atmospheric instability

The heavy precipitation events (HPEs) present a challenge for regional climate models (RCMs) mostly due to parameterized physical processes, especially convection. The aim is to examine the atmospheric stratification and instability in RCM before HPEs during the HyMeX campaign, in autumn 2012, which affected the coastal mountainous region of Croatia. The RCM is spectrally nudged ALADIN-Climate version 6.3 driven by ERA-Interim reanalysis over the Med-CORDEX domain. Additionally, three experiments were conducted with parameter changes in physical parameterization schemes, specifically the convection scheme (entrainment and aerodynamical drag), microphysics, radiation, turbulence, and dynamics. Vertical profiles of temperature and humidity from the model were examined and compared with radio sounding measurements from the Zadar station. Also, the thermodynamic (CAPE, CAPE3, CIN, K-index, LI) and kinematic indices (vertical wind shear) were analyzed. All simulations show smoother profiles of temperature and humidity not capturing sharp changes in some layers. However, the temperature profiles are very close to observed for most of the IOPs and very similar between experiments. For humidity profiles, the situation is more complex and results vary depending on the IOP and atmospheric level. Results for thermodynamic indices show different discrepancies depending on the IOP mainly due to the mismatched timings of convection initialization and maximum intensity of convection between experiments and observations. Results for the vertical wind shear in several layers for most IOPs show very good agreement with observed values.

heavy precipitation event, CNRM-ALADIN, Dinaric Alps, HyMeX, Med-CORDEX, regional climate model, atmospheric instability

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