CLIMATOLOGY OF DRY AND WET HEAT AND COLD WAVES OF DIFFERENT INTENSITY

Abstract

The article discusses the results of a statistical analysis of increases and decreases in the average daily air temperature, presented as waves of heat and cold. By a wave of heat (cold) we mean a change in the average daily air temperature by three degrees or more that lasted for at least two days. If a wave of heat (cold) was interrupted by one day of cooling (warming) or isothermy, such cases were considered a single wave. All waves were divided into dry and wet. A wave was considered wet if there was precipitation on at least one day during the development of this wave. We calculated the frequency of occurrence, duration of dry and wet waves, and the number of days with precipitation for each wave. The analysis was carried out for waves of different intensities. On average, the number of warm and cold waves per year is the same. Approximately the same number of warm and cold waves occur in winter and summer. In spring, heat waves prevail over cold waves, while in autumn the trend is opposite. The average duration of a wave is 4 days. The more intense the wave, the longer its duration. The majority of waves are wet. Precipitation accompanies 85% of heat waves and 75% of cold waves. Precipitation falls on about half the days of the wave’s duration. Cold waves are quite often interrupted by one-day increases in the average daily temperature. It is during these days that precipitation is observed. Synoptic analysis has shown that such cases of one-day ‘interruption’ of cold waves are associated with active processes of cyclogenesis on cold fronts. Wave formation at the cold front stimulates precipitation.