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Climate indices

Climate refers to the multiannual nature of the weather, its typical changes, as well as daily and yearly fluctuations. The assessment of climate change involves using various climate indices, which generalise the accumulated meteorological data and allow to compare climate in various places of the world. Provided below, there are several climate indices, which reflect the changes taking place in Lithuania.

Lithuania, like the rest of the world, feels an increase in air temperature: the numbers of warm summer days with maximum air temperature above than 25 °C have notably increased since 1961 (Fig. 1).

Fig. 1 Number of warm summer days (number of days per year, when Tmax > 25 °C): a) Klaipėda; b) Vilnius.


Our country is also increasingly experiencing cases of tropical nights, when the air temperature at the coolest hours of the night does not fall below 20 ºC (Fig. 2). This phenomenon used to be quite rare before 1990 and some of the meteorological stations had never recorded such nights at all.


Fig. 2 Number of tropical nights (when Tmin ≥ 20 °C): a) Klaipėda; b) Vilnius.


Increasing average air temperature means fewer days with negative temperature during the cold season as well (Fig. 3).


Fig. 3 The number of days with negative air temperature: a) Klaipėda; b) Vilnius.


Changes include not only air temperature, but also the amount and distribution of precipitation. The changes in the amount of precipitation in Lithuania are insignificant, but the cases of intensive precipitation, featuring 20 mm and more in a day, are becoming more frequent. (Fig. 4)


Fig. 4 The number of days with precipitation of ≥ 20 mm in a day: a) Klaipėda; b) Vilnius.


Tendencies of climate change, notable in Lithuania, reflect the climate change all over the world. The average global temperature since the late 19th c. has increased by 0.85 °C and there are notable changes in the water cycle as well with some regions becoming dryer and vice versa. You can read more on the climate change at climate change.