Long-term precipitation variability on thunderstorm days in Poland (1951–2000)

The paper discusses the frequency of precipitation, broken down into amount categories, on thunderstorm days in Poland during the period 1951–2000. The authors looked at the number of thunderstorm days with precipitation versus the total thunderstorm days. Frequencies of certain precipitation totals on thunderstorm days were determined for various Polish regions, as well as long-term and annual precipitation variabilities. Daily precipitation and thunderstorm observation records from 47 Polish weather stations were used in the study. Precipitation on thunderstorm days was broken down into the following categories: dry day or trace precipitation, 0.1–10.0 mm, 10.1–20.0 mm, 20.1–30.0 mm, and more than 30.0 mm. These categories were studied for variability in five thunderstorm regions in Poland. The study revealed at that precipitation occurred on most of the thunderstorm days in the second half of the 20th century in Poland (on average 85% of cases). On 63% of thunderstorm days there was between 0.1 and 10.0 mm of rain. Cases of more than 30.0 mm of precipitation were very rare (2.7%) and were recorded mostly in mountainous areas. Annual frequencies of the various precipitation categories were similar across all of the regions. There was more variability in the long-term view, but in most cases no clear trend could be established. Slight decrease in number of thunderstorm days without precipitation (statistically significant in regions II and III) and an increase in days with the lowest precipitation, 0.1–10.0 mm (statistically significant in region V) was stated.