Study of the Extreme Thermal Conditions for the Sofia Region—Preliminary Results

The environmental thermal comfort is one of the issues not only these days, but also in the future, concerning the results from the climate projections. The objective of this paper is to study the human discomfort in winter and summer in Sofia and its surroundings. Weather Research and Forecasting (WRF) model numerical simulations were used to calculate two characteristics called indexes, of the thermal environmental properties from the human point of view. They estimate the deviation of the environmental conditions from the human thermal comfort. The first one—Wind Chill index describes the thermal discomfort in low temperatures (winter), depending on air temperature and wind speed. The second one—Heat Index describes the deviation from the summer thermal comfort in high air temperatures (summer), depending on the air temperature and relative humidity. Numerical experiments with combination of different parameterization schemes for atmospheric boundary layer and microphysical processes were carried out. Model performance for the temperature, wind speed and relative humidity were used for estimation of the best model options for calculation of the Wind Chill and Heat Index in the corresponding conditions when they are applicable.