Istorinių audrų Lietuvoje atmosferos cirkuliacijos sąlygos

• Main Author: Bernatavičius, Karolis Augustas
• Other Authors: Stankūnavičius, Gintautas
• Format: Bachelor Thesis
• Language: Lithuanian; English
• Published: Institutional Repository of Vilnius University 2018
• Subjects: Norwegian Sea; Iceland
• Online Access: http://vu.lvb.lt/VU:ELABAETD35994591&prefLang=en_US

Atmospheric Circulation Patterns of Historical Storms in Lithuania In this study, atmospheric circulation patterns of historical storms in Lithuania are analysed from the middle of 19th century to the present. Reliability of storms were verified by confirming that their wind speed exceeds 10 m/s and the wind direction is from 220° to 320°. After verifying whether they match these conditions, a number of 7 cases of Storms were discarded. Storms were grouped by 500 hPa geopotential height anomalies and fell into six classes - a, b, c, d, e, f. Six storms fell in ‘a’ class, twelve – in ‘b’ class, nine – in ‘c’ class, six – in ‘d’ class, one – in ‘e’ class, two – in ‘f’ class. Classified composite maps of geopotential height in 500 hPa level shows the distribution of the average geopotential height anomalies in decameters. The biggest similarity in all storms classes between maps are of negative anomaly field near the center of Scandinavian Peninsula and Gulf of Bothnia. Another similarity is of positive anomaly. Center part of prevailing positive anomaly is located in Atlantic Ocean in all storms classes except for b class, which center part of prevailing positive anomaly is located in South of Europe. High pressure systems in composite maps vary slightly. Low pressure systems in composite maps changes rapidly. According to storms classes ‘a’, ‘c’ and ‘d’ low pressure systems move from North West of Norwegian Sea deep into the land. In storm class ‘b’ low pressure systems move from West of Iceland into the land. According to NAOO/ESRL significance level is 0,950, correlation coefficient that is bigger than 0,453 is statistically significant when there is more than 14 numbers in a sequence. The biggest number of insignificant correlation coefficient cases has NOA/NAOs ¬ 7 cases, NAO/GBI ¬ 6 cases and GBI/NAOs ¬5 cases. NAO/NAOs and GBI/NAOs index correlation coefficient is similar to one another but with different number signs, when one coefficient is getting bigger the other is getting smaller and vice versa. That is also shown by average index difference in 14 days when storm is developing. When GBI index is getting bigger NAO and NAOs index is getting smaller and vice versa.