{"title":"Contribution of winter upwelling in the Gulf of Finland to lake-effect snow in Estonia","authors":"Ü. Suursaar, Helve Meitern","doi":"10.5200/baltica.2021.2.1","DOIUrl":null,"url":null,"abstract":"The aim of the study was to analyse the sequence of winter (“warm”) upwelling and lake-effect snow (LES) events that deposited up to 50 cm of snow along the North Estonian coast in January–February 2021. Based on weather and aerological data, four episodes of LES were documented. Heavy, localized lake-effect enhanced precipitation occurred along a 30–50 km wide coastal strip bordering the Gulf of Finland when a cold air mass from the north advected over the warmer, unfrozen sea surface. A temperature difference of up to 20°C was revealed between the air mass temperatures measured at the 850 hPa level and at the sea surface. The LES events, in turn, were preceded by upwelling in the southern Gulf of Finland, which was generated by persisting easterly winds. Even when occasionally interrupted by a wind change, the upwelled water still kept sea surface temperature (SST) in the southern half of the Gulf higher, as documented by the water temperature records from the coastal stations of Estonia, SST and salinity imagery retrieved from the SatBaltyk system, and sea ice distribution charts. Differently from summer (cold) upwelling, winter upwelling brought up warmer (2–4°C) water from the sub-surface layers replacing the already cooled down (0–1°C) surface water. Thus, winter upwelling enhanced LES in two ways. Firstly, by not letting the Gulf freeze over, and therefore by providing a fetch. And secondly, by increasing the SST (and therefore also the 850 hPa level – surface temperature difference) by up to 4°C.","PeriodicalId":55401,"journal":{"name":"Baltica","volume":"1 1","pages":""},"PeriodicalIF":0.5000,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Baltica","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5200/baltica.2021.2.1","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 2
Abstract
The aim of the study was to analyse the sequence of winter (“warm”) upwelling and lake-effect snow (LES) events that deposited up to 50 cm of snow along the North Estonian coast in January–February 2021. Based on weather and aerological data, four episodes of LES were documented. Heavy, localized lake-effect enhanced precipitation occurred along a 30–50 km wide coastal strip bordering the Gulf of Finland when a cold air mass from the north advected over the warmer, unfrozen sea surface. A temperature difference of up to 20°C was revealed between the air mass temperatures measured at the 850 hPa level and at the sea surface. The LES events, in turn, were preceded by upwelling in the southern Gulf of Finland, which was generated by persisting easterly winds. Even when occasionally interrupted by a wind change, the upwelled water still kept sea surface temperature (SST) in the southern half of the Gulf higher, as documented by the water temperature records from the coastal stations of Estonia, SST and salinity imagery retrieved from the SatBaltyk system, and sea ice distribution charts. Differently from summer (cold) upwelling, winter upwelling brought up warmer (2–4°C) water from the sub-surface layers replacing the already cooled down (0–1°C) surface water. Thus, winter upwelling enhanced LES in two ways. Firstly, by not letting the Gulf freeze over, and therefore by providing a fetch. And secondly, by increasing the SST (and therefore also the 850 hPa level – surface temperature difference) by up to 4°C.
期刊介绍:
BALTICA is an international periodical journal on Earth sciences devoted to the Baltic countries region and the Baltic Sea problems. This edition as a Yearbook is established in 1961 by initiative of Academician Vytautas Gudelis. Since 1993, an Editor-in-Chief of the journal became Academician Algimantas Grigelis. BALTICA is published biannually (in June and December) in cooperation with geoscientists of the circum-Baltic States.
BALTICA is publishing original peer-reviewed papers of international interests on various Earth sciences issues. The particular emphasis is given to Quaternary geology, climate changes and development of ecosystems, palaeogeography, environmental geology, as well as stratigraphy, tectonics, sedimentology and surface processes with relevance to the geological history of the Baltic Sea and land areas. Journal emphasizes modern techniques, methodology and standards. The journal structure comprises original articles, short reviews, information, bibliography.