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- Title
Lijundros trukmė ir meteorologinės bei sinoptinės formavimosi sąlygos Lietuvoje.
- Authors
Gečaitė, Indrė; Rimkus, Egidijus
- Abstract
An analysis of freezing precipitation parameters in Lithuania in 1961-2010 is presented. Their spatial distribution and distribution throughout the year as well as diurnal cycle were analysed. Favourable synoptic and meteorological conditions for freezing precipitation formation were determined. Also, an analysis of the phenomenon duration changes during the study period was made. The statistical significance of the observed trends was examined using the Mann--Kendall test. Data of 18 Lithuanian meteorological stations for the period 1961-2010 were used. The mean cold season freezing precipitation duration in 1961- 2010 in Lithuania was 75 hours (Fig. 1). The highest values of freezing precipitation parameters were determined in the Šemaičiai Highland. Western Lithuania can be characterized as having the least duration of this phenomenon. During the study period the absolute maximum duration was fixed in the Laukuva station (926 hours, 1995-1996). The longest mean freezing precipitation duration occurred in the 1969-1970 cold season (Table 1). The spatial distribution of freezing precipitation duration depends on meteorological conditions and the geographical characteristics of a station such as absolute height and orientation to the predominant air mass advection. The analysis has shown that freezing precipitation in Lithuania can occur in October-April. The longest duration was determined in December--January (Fig. 2). The most frequent freezing precipitation was registered at night (3-7 h) and the least in the afternoon (12-18 h) (Fig. 3). The most favourable synoptic conditions for freezing precipitation formation are warm and warm-occluded fronts when in the atmosphere a layer of positive temperature occurs and temperature inversion is present. In such cases, inversion was determined at 1 000 hPa level (53%). Usually, freezing precipitation was formed when the air temperature was 1- -3 °C, at high relative humidity (>95%), SE, S, SW wind directions and a low wind speed (1-4 m/s) (Figs. 4-6). The mean duration of freezing precipitation decreased on average by 45 hours during the study period. The largest negative changes were observed in Dotnuva (115 hours) and Biržai (100 hours). Only in the most eastern part of Lithuania (Dūkštas) the tendencies of freezing precipitation duration indices were positive (Fig. 7). The most negative trends were observed in January and December.
- Subjects
LITHUANIA; FREEZING precipitation; CIRCADIAN rhythms; CLIMATE change; METEOROLOGICAL stations; SEASONS; HUMIDITY; UPPER air temperature; AIR masses
- Publication
Geografija, 2011, Vol 47, Issue 2, p71
- ISSN
1392-1096
- Publication type
Article