Sensitivity of the numerical weather forecast fields to the variations in St. Petersburg surface parameters
E.M. Ladokhina1,2,3, K.G. Rubinshtein1,4, A.V. Kulyushina2,5
1Hydrometeorological Centre of Russia, Moscow, Russia
2Limited Liability Company В«MicroStep-Mis», St. Petersburg, Russia
3North-West Department of Hydrometeorology and Environmental Monitoring, St. Petersburg, Russia
4Nuclear Safety Institute, Russian Academy of Sciences, Moscow, Russia
5Udmurt State University, Izhevsk, Russia
Keywords: numerical weather prediction, WRF-ARW, St. Petersburg, physical parameters of underlying surface, urban heat island
Abstract
The influence of physical parameters, which describe the St. Petersburg surface properties in the WRF-ARW model, on the forecast of surface meteorological elements is studied. The results are estimated for the cases June 14-22, 2015, when intense positive temperature anomaly occurred in St. Petersburg in comparison with the surroundings. The parameters were chosen from the analysis of similar studies for several cities of the world. Experiments with serial variations in the parameters selected showed that decrease in the surface albedo, soil moisture content, and surface emissivity and an increase in the roughness length improved the forecast quality for the city in comparison with a control experiment. In final experiment, the concurrent variations in the urban surface physical parameters, in accordance with the results of serial experiments, significantly improved the simulation of the city’s thermal anomaly in the model. In the time periods corresponding to the intense urban heat island occurrence, the difference in the surface temperatures between the control and final forecasts could attain 2 °C for the St. Petersburg model area. Under certain synoptic conditions, the variations in the urban surface parameters in the model affect the forecast of meteorological fields within a radius of 150 km from the center of the metropolis.
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