Convection-Permitting Simulation of a Heavy Rainfall Event in Armenia Using the WRF Model

On 2 July 2016 afternoon a heavy rainfall (52.8 mm) was observed over southwestern part of Armenia, at Talin station. High-frequency radar observations and Weather Research and Forecasting (WRF) model output show that initiation of earliest convection occurred over Aragats mountain massif around noon due to low-level convergence of thermally induced upslope winds. Further convective development was affected by generation of secondary convection as a result of interaction between cold pool outflows from developed convective cells and upslope winds. The high-resolution WRF run (3 km) using NSSL two-moment cloud microphysics parametrization and the European Centre for Medium-Range Weather Forecasts operational model forcing data best reproduces the location, timing, magnitude, and microphysical structure of the observed convective rainfall among six WRF microphysical schemes tested in this study. Radar observations show that cold cloud process typical for continental-type deep convection was observed in Armenia. The NSSL includes the double-moment microphysics schemes for both warm and cold cloud processes, which might be a reason for improved simulation of observed heavy rainfall event in Armenia. Using the coarser resolution ERA5 analysis forcing data in the WRF model leads to simulation of earlier rainfall peaks at Talin station and spurious convective rainfall areas. The WRF model forced by the Global Data Assimilation System Final analysis from the National Centers for Environmental Prediction, even run at 3-km resolution, is not able to reproduce the accurate location of convection and rainfall over the study area.