ESTONIAN ENVIRONMENTAL REVIEW 2009

o
C
Ristna
-22.9/-28.4
Vilsandi
-21.1/-28.6
Sõrve
-3.0
-18.2/-29.5
Pakri
-26.2/-29.7
Tallinn
-26.9/-32.2
Lääne-Nigula
Kuusiku
-27.7/-40.6
-26.6/-33.8
Türi
-28.5/-37.6
Virtsu
-26.4/-33.7
-28.4/-34.5
Viljandi
Pärnu
-29.7/-34.7
Kihnu
-25.6/-32.4
Narva-Jõesuu
Kunda
-29.7/-42.6
-28.8/-34.9
Jõhvi
-31.5/-41.0
Väike-Maarja
-30.2/-36.2
Tiirikoja
Jõgeva -32.0/-39.6
-30.7/-40.2
Tõravere
-29.3/-38.2
Valga
Võru
-31.2/-40.5 -31.0/-40.5
Map 4.1. Average air temperature in February 2005–2008 (pink areas) and absolute minimum air temperature in 2005–2008 (to the
left of the slash) and in 1961–2004 (to the right of the slash). Data: EMHI.
4.1.2. Precipitation
Even though the average amount of precipitation in
Estonia in the years 1961–2008 is characterised by a rising
trend (figure 4.3), it cannot be considered reliable due to
the large amount of deviation. Here it can be noted that in
just the last four years there were two years with extreme
precipitation conditions – 2006 and 2008. The former was
a very dry year and the latter one of the wettest.
Precipitation in the warm period makes up the bulk of
the annual precipitation total. The amount of precipitation
in the years 2005–2008 was largest in August exceeding
the average total of August precipitation in 1961–2004
by 37%. Also in January the amount of precipitation was
larger than average.
The greatest precipitation amount fell in the southwestern
and western part of the Estonian mainland;
considerable amount of precipitation fell also in the Jõhvi
area. In Jõhvi also a new precipitation record for a 24-hour
period was set – 116 mm on 21 August 2008 (map 4.2).
4.1.3. Water levels and flow rates
Weather pattern and precipitation amounts caused
fluctuation of the water level and flow rate in water bodies.
A strong storm occurred on 9–11 January 2005 (winds
gusting to 33–38 m/s), and in Pärnu the sea level rose to
275 cm over the Kronstadt datum. The same storm resulted
in a sudden surge in the water level of rivers in northern
and south-western Estonia, which exceeded previously
recorded winter levels. Precipitation at the end of August
and September 2008 had saturated the soil with water
to the point that flooding was to have occurred even in
conditions of average precipitation.
On the other hand, in the summer months of 2006 and
2007, water levels were lower than average. 2006 was an
especially dry year: Lake Peipsi was 56 cm lower than the
long-term average level, Lake Võrtsjärv, consequently
75 cm. In 2008, the lakes began to be replenished due to
the surfeit of water in the rivers and by December, the
level of Lake Võrtsjärv was nearly a metre higher than
the long-term average.
Short-term fluctuations in the water regime of rivers
occur, but the long-term linear trend of the annual average
flow rate of rivers (1922–2008) does not show clear
signs of increase or decrease. Analysis of the data has
found that wet and dry periods alternate in approximately
25–30 year cycles. This leads to the supposition that a wet
cycle has now begun.
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