Monitoring Agricultural Drought in Poland - Monitoring and Predicting Agricultural Drought: A Global Study - page 172

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Line
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0.8
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Norm
PgEn

Fig ure 13.1 Production of the main crops in Poland.

highly susceptible to droughts. Regions located above 54°N are in the zone
of Baltic Sea climate characterized by higher rainfall (600-700 mm) and
hence are less prone to drought than the rest of Poland. The distribution
of drought-prone areas is shown in figure 13.3.
Droughts occurred 19 times in Poland during 20th century (i.e., once
every 4-5 years; Slota et al., 1992). These droughts can be linked to the
processes of air circulation over Europe and the adjacent ocean. Thermal-
humidity anomalies caused droughts in 1977, 1983, 1989, and 1992 (the
year of the great European drought). In 1992, drought affected more than
90 % of the land, and the total precipitation was 40-50% below normal.
Th is severe drought was caused by translocation of very warm, dry tropical
m asses of air in the beginning of summer, which increased evapotranspira-
tio n and reduced precipitation, forming long dry spells. In addition, poor
dr ainage, accelerated land development, and acid rains also contributed to
oc currence of poor yields and agricultural droughts in Poland.

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D rought Monitoring Methods
To study agricultural droughts in Poland, a special index was constructed
which was found to be a better indicator of drought than the precipitation
alone. The index is defined as EP/P veg , where EP is potential evapotranspira-
tion and P veg is the average sum of rainfall during vegetation period (April-