Український гідрометеорологічний журнал (Dec 2022)
Application of climatological approach to determine the temperature of radiation fogs formation
Abstract
The effectiveness of a radiation fog forecast is determined by the accuracy of a forecast for two values – temperature of fog formation and minimum air temperature. The accuracy of the first measurement significantly depends on a degree of adaptability of a forecast method to specific factors affecting the formation of fogs – orthography, local circulations, seasons, time of day, temperature-humidity stratification in the boundary layer of the atmosphere, etc. Taking into account each of them in a specific point will dictate its characteristics, whereas use of non-adapted fog forecasting methods will reduce their effectiveness. The article suggests an approach that makes it possible to carry out a comparative analysis of the prognostic value of the fog formation temperature and its average value pertaining to a specific point, season and time of day. In order to implement the studied approach the research considered a daily-annual repeatability of fogs at Kyiv station over 2012-2020. Based on this an average temperature of fog formation for each combination of month and time of day was determined according to actual observation data and, for the purpose of comparison, according to the Sanders method that uses data from radio sounding of the atmosphere as its baseline. The results of the analysis of the structure of the fog repeatability distribution allowed approximation of the daily-annual distribution of fog formation temperature via polynomial functions and a harmonic two-dimensional oscillator. Based on the selected efficiency criterion it was determined, via sequential selection, that the polynomial approximation of the data indicating the actual temperature of fog formation during the year is the most effective method. Obtaining an analytical form of the probability distribution function of daily and annual values of the fog formation temperature allows us to plot graphs of its daily variability for any month of the year. Such result makes it possible to control emissions of forecast values of fog formation temperature for a specific point, season and time of day, which will increase the effectiveness of the existing ways of making the forecasts in question.
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