The frequency of occurrence of extreme and detrimental meteorological conditions for vegetation of crops in Poland (1971–2010)

Abstract

Abstract The frequency of occurrence of extreme and detrimental meteorological conditions for vegetation of crops in Poland (1971-2010). The subject, and aim of this study is the comparison of the frequency of occurrence of thermal, precipitation and pluvio-thermal conditions detrimental to agriculture in Poland during two periods: 1971-2000 and 1981-2010, constituting the former, and the current climate normal, respectively. Each month of the vegetation period (April-October) was, in accordance with the current accounts carried out by agriculture correspondents, assigned to one of the following categories: favorable for vegetation, dry, dry and cool, cool, cool and humid, humid, dry and hot. An identical classification of meteorological vegetation conditions was also carried out for months characterized by extreme air temperature and precipitation values. Extreme values were defined as those monthly temperature mean values, and monthly precipitation totals, the probability of exceeding of which is lower than 10%, i.e. their probability of occurrence, or the socalled recurrence interval, is once every 10 years. The differences existing between the analyzed 30-year periods, can be attributed to the present day climate change - a significant increase in air temperature in April, June, July, and August, with a lack of significant precipitation trends. In the two compared periods, an increase in the number of extreme months from 74 to 82 was stated. The biggest changes during the extreme months were observed for precipitation deficits combined with hot air temperatures, namely, an increase from 15 to 29 months. In general, all the analyzed months of the vegetation period showed an increase in dry months (90 to 105 cases) and a decrease in cool months (44 to 24 cases).