356
M. Kejna et al.
course, the driest month in terms of relative humidity was May (69%), and the most
humid—December (89%) (Fig. 15.6).
Atmospheric precipitation plays an important role in the environment, being as it
is part of the cycle of water and various chemical substances and supplies surface and
groundwater. Precipitation in the majority of the area of Poland is rather small. In
the central part of the country—the lowlands—annual precipitation does not exceed
550 mm [25]. At Koniczynka the mean annual precipitation total was 550.7 mm in
the years 1994–2017. Precipitation is a weather element that reveals a high variability
over time: the mean annual values may be different in different years. In 2001 and
2017, the precipitation totals were greater than 700 mm (762.0 mm and 727.2 mm,
respectively), whereas in 1997, 2005 and 2015 they were less than 450 mm, with
respective values amounting to just 444.4 mm, 413.0 mm and 437.3 mm. Such fluctuations may result in water excess or shortage in the ecosystem. At Koniczynka,
meteorological droughts [25] and hydrological droughts were frequent. In the annual
course, the precipitation total was smallest in February (26.3 mm) and biggest
(94.8 mm) in July (Fig. 15.6). The summer maximum was due to storm rainfalls. In
the multi-annual period, there is a slightly growing trend in precipitation total. It is
similar in NW Poland, where most stations showed a slight upward trend (1951–2000)
[26]. In the analysed period, the number of precipitation days revealed a statistically
significant growing trend (+17.04 days/10 years).
Snow cover is formed through snowfalls, but its development and duration also
depend on air temperature. The mean depth of snow cover in the lowland part of
Poland in the years 1970/1971–1999/2000 ranged from less than 6 cm in the west
to more than 12 cm in the north-east [25]. In the multi-year period (1960/1961–
2009/2010) in Poland, there was a slight falling trend in the snow cover depth, but
the changes were generally statistically insignificant [27, 28]. Similarly, the snow
cover depth at Koniczynka was also a little reduced (−0.43 cm/10 years) and was
statistically insignificant (p < 0.05).
The mean wind speed in Poland is low and amounts to 3–4 m·s
−1 in most parts of
the country [23, 25]. Over the multi-annual period of 1951–2005 in Central Europe
wind speed had a growing trend [29]. On the one hand, a higher wind speed ensures
better airing and improves air quality conditions. On the other hand, more frequent
high winds may cause damage to the economy and environment. In the years 1995–
2017 at Koniczynka, the wind speed trend was slightly upward, but statistically
insignificant. In the annual course, the lowest atmospheric dynamics were found in
the summer (July 2.7 m·s
−1 ), and the highest mean wind speeds were observed from
January to March (3.9 m·s
−1 )—Fig. 15.6.
15.5 Water Flow Variability in the Struga Toru ´
nska
The hydrological regime of a river depends on a number of factors. The runoff is
determined by the amount and distribution of precipitation in a year and the duration and thickness of the snow cover. Air temperature is also relevant, as it affects
M. Kejna et al.
course, the driest month in terms of relative humidity was May (69%), and the most
humid—December (89%) (Fig. 15.6).
Atmospheric precipitation plays an important role in the environment, being as it
is part of the cycle of water and various chemical substances and supplies surface and
groundwater. Precipitation in the majority of the area of Poland is rather small. In
the central part of the country—the lowlands—annual precipitation does not exceed
550 mm [25]. At Koniczynka the mean annual precipitation total was 550.7 mm in
the years 1994–2017. Precipitation is a weather element that reveals a high variability
over time: the mean annual values may be different in different years. In 2001 and
2017, the precipitation totals were greater than 700 mm (762.0 mm and 727.2 mm,
respectively), whereas in 1997, 2005 and 2015 they were less than 450 mm, with
respective values amounting to just 444.4 mm, 413.0 mm and 437.3 mm. Such fluctuations may result in water excess or shortage in the ecosystem. At Koniczynka,
meteorological droughts [25] and hydrological droughts were frequent. In the annual
course, the precipitation total was smallest in February (26.3 mm) and biggest
(94.8 mm) in July (Fig. 15.6). The summer maximum was due to storm rainfalls. In
the multi-annual period, there is a slightly growing trend in precipitation total. It is
similar in NW Poland, where most stations showed a slight upward trend (1951–2000)
[26]. In the analysed period, the number of precipitation days revealed a statistically
significant growing trend (+17.04 days/10 years).
Snow cover is formed through snowfalls, but its development and duration also
depend on air temperature. The mean depth of snow cover in the lowland part of
Poland in the years 1970/1971–1999/2000 ranged from less than 6 cm in the west
to more than 12 cm in the north-east [25]. In the multi-year period (1960/1961–
2009/2010) in Poland, there was a slight falling trend in the snow cover depth, but
the changes were generally statistically insignificant [27, 28]. Similarly, the snow
cover depth at Koniczynka was also a little reduced (−0.43 cm/10 years) and was
statistically insignificant (p < 0.05).
The mean wind speed in Poland is low and amounts to 3–4 m·s
−1 in most parts of
the country [23, 25]. Over the multi-annual period of 1951–2005 in Central Europe
wind speed had a growing trend [29]. On the one hand, a higher wind speed ensures
better airing and improves air quality conditions. On the other hand, more frequent
high winds may cause damage to the economy and environment. In the years 1995–
2017 at Koniczynka, the wind speed trend was slightly upward, but statistically
insignificant. In the annual course, the lowest atmospheric dynamics were found in
the summer (July 2.7 m·s
−1 ), and the highest mean wind speeds were observed from
January to March (3.9 m·s
−1 )—Fig. 15.6.
15.5 Water Flow Variability in the Struga Toru ´
nska
The hydrological regime of a river depends on a number of factors. The runoff is
determined by the amount and distribution of precipitation in a year and the duration and thickness of the snow cover. Air temperature is also relevant, as it affects