Numerical Modeling of Extreme Wind Profiles Measured with SODAR in a Coastal Area

Abstract

The extreme wind events could be dangerous and can cause significant infrastructure damages, economic losses and even loss of human life. Therefore, the results of research in this field are of great importance for decision-making purposes related to better management and reduction of risks. Effective and accurate systems for observations and forecasting of hazardous meteorological events are society requirements for the prevention of socio-economic costs. The mesoscale numerical simulations in coastal areas are challenging research task due to the theoretical description intricacy of the Atmospheric Boundary Layer (ABL) processes. The variability of atmospheric stratification and meteorological fields in horizontal and vertical direction in complex orography impose the necessity of continuous improvement of the parametrizations in numerical simulations on one side and high-resolution data for evaluation, on the other side. In this study we use sodar measurements (MFAS SCINTEC) at the Black sea coast in Bulgaria to evaluate the performance of the Weather Research and Forecasting (WRF) mesometeorological model to represent the evolution of vertical wind field structure during extreme wind conditions. The acoustic sounding with high vertical (10 m) and temporal (10 min) resolution was performed at Ahtopol for a long-term period: August 2008-October 2016. A reference extreme wind speed profile was obtained applying criteria for “rare” events of the Intergovernmental Panel on Climate Change (IPCC). The WRF simulations were run on the Supercomputer System “AVITOHOL” at the Institute of Information and Communication Technologies – Bulgarian Academy of Sciences (IICT – BAS). The model was used with fine horizontal grid of 1 km with the local ABL scheme of Mellor-Yamada-Janjic (MYJ) for a period with extreme wind events. The numerical simulations were evaluated through Pearson’s correlation coefficients between sodar measurements and model simulations of wind profiles. The results are important for the appropriate choice of WRF setup to deal with extreme wind synoptic situations on Bulgarian coastal site.