NUMERICAL MODELING OF HEAVY SUMMER RAINFALLS WITH DIFFERENT GRID SPACING OF THE REGULAR GRID STEP

Abstract

Climate warming is causing an increase in the total moisture content on the planet and in the number of heavy rainfall cases. Many of these result in severe flooding, victims, and destruction of infrastructure. The aim of the study is to establish the possibility of improving the quality of heavy precipitation forecasting by reducing the step of the computational grid in the mathematical model of the atmosphere. The article presents the results of a study of extreme summer precipitation in the Ural Kama region for the period from 1979 to 2015. The statistical characteristics of 37 precipitation cases with an intensity of more than 50 mm in 12 hours were analyzed. Computational experiments were performed on the WRF-ARW regional atmospheric model. The meteorological conditions for the occurrence of heavy rain in town of Gubakha with an extreme intensity of 114,5 mm in 12 hours were taken as a special case for the study. A qualitative assessment of the simulation results showed that for the selected case, the model correctly reproduced the general structure of heavy rains, but significantly shifted it eastward. A quantitative assessment of the forecast quality was conducted for numerical forecast of heavy precipitation based on the WRF-ARW model at a grid step of 3 km and 7,2 km. The quality of the model was evaluated based on the forecast accuracy not only at the measurement point but also in the vicinity within a radius of 50 km. It was found that there was no significant improvement in the quality of the forecast of high-intensity precipitation when switching to a smaller grid step according to both the first and second assessment methods. The results obtained can be taken into account when preparing forecasts of heavy rains occurrence and when developing flood forecast techniques.