The atmospheric circulation patterns during dry periods in LithuaniaThe study was supported by the Lithuanian-Swiss cooperation programme to reduce economic and social disparities within the enlarged European Union under project agreement No. CH-3-ŠMM-01/05

• Published in: Oceanologia Vol. 56; no. 2; pp. 223 - 239
• Main Authors: Rimkus, Egidijus, Kažys, Justas, Valiukas, Donatas, Stankūnavičius, Gintautas
• Format: Journal Article
• Language: Polish
• Published: Elsevier Urban & Partner Sp. z o.o 2014
• Subjects: Atmospheric circulation; Droughts; Hydrothermal coefficient; NAO and AO; TMI blocking index; Atmospheric circulation; TMI blocking index; Hydrothermal coefficient; NAO and AO; Droughts
• ISSN: 0078-3234
• DOI: 10.5697/oc.56-2.223

This paper reveals the atmospheric circulation patterns during dry periods in Lithuania. The research covers the period from 1961 to 2010. Atmospheric circulation features were analysed using the Hess and Brezowski classification of macro-circulation forms, NAO and AO indices, a 500hPa geopotential height field and the Tibaldi-Molteni blocking index. Different phases of the dry period (developing, persisting and attenuation) were evaluated individually. Also, the regional differences of dry period formation were investigated. In general dry periods are determined by a decrease in zonal and an increase in meridional circulation forms as well as the atmospheric blocking process over the Baltic region longitudinal belt 0–20 days prior to the start of the dry period. An especially strong shift from general circulation patterns are observed during the developing phase of a dry period. Drought persistence in the Baltic region is almost always predetermined by strong anticyclonic circulation. Most drought development stages are associated with negative NAO/AO phases