{"title":"Blocking Indices in the Northern Hemisphere: Assessments for 2020 and Trends of Long-Term Changes","authors":"L. K. Kleshchenko, E. Ya. Rankova","doi":"10.1134/s0001433823140098","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>In this article, episodes of potential blocking in the Northern Hemisphere (40°–75° N) are determined based on the analysis of deviations of the H500 geopotential at the nodes of a regular geographic grid from their midlatitude values. The cumulative calendar season/year duration of blocking episodes is considered as the <i>TD</i> blocking index. The spatial distribution of seasonal/annual <i>TD</i> indices and their anomalies in 2020 are analyzed (up to 160 days). The highest values of the annual <i>TD</i> index in 2020 were observed on the European continent in the zone 50°–57.5° N (up to 160 days). Anomalies of the <i>TD</i> index in European Russia (ER) and in Western Siberia amounted to +30 days; in the northern regions of Eastern Siberia they lasted more than +40 days. In the Western Hemisphere, positive anomalies in the annual <i>TD</i> index were observed in the East Pacific Ocean south of 50° N (for more than +50 days). Negative anomalies covered the central regions of North America (up –80 days). According to estimates in active blocking sectors, in the first half of 2020, blocking in the European sector (10° W–60° E; 50°–65° N) was weakened relative to the multiyear average. In the summer and autumn seasons, positive anomalies of blocking indices were noted in this region. In the North American sector (100°–160° W; 50°–65° N), negative anomalies were observed in all seasons except for spring. Estimates of the linear trend of blocking indices at the nodes of the regular grid and in general in the latitudinal belt and its sectors were analyzed for 1949–2020 and 1976–2020. On average, negative trends prevailed in all seasons, but the spatial distribution of the trend coefficients varied from season to season. The trend of the annual duration of blocking episodes in the latitude zone 50°–65° N is 1.0 days/10 years and is statistically significant at a 1% level.</p>","PeriodicalId":54911,"journal":{"name":"Izvestiya Atmospheric and Oceanic Physics","volume":"84 1","pages":""},"PeriodicalIF":0.9000,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Izvestiya Atmospheric and Oceanic Physics","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1134/s0001433823140098","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"METEOROLOGY & ATMOSPHERIC SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
In this article, episodes of potential blocking in the Northern Hemisphere (40°–75° N) are determined based on the analysis of deviations of the H500 geopotential at the nodes of a regular geographic grid from their midlatitude values. The cumulative calendar season/year duration of blocking episodes is considered as the TD blocking index. The spatial distribution of seasonal/annual TD indices and their anomalies in 2020 are analyzed (up to 160 days). The highest values of the annual TD index in 2020 were observed on the European continent in the zone 50°–57.5° N (up to 160 days). Anomalies of the TD index in European Russia (ER) and in Western Siberia amounted to +30 days; in the northern regions of Eastern Siberia they lasted more than +40 days. In the Western Hemisphere, positive anomalies in the annual TD index were observed in the East Pacific Ocean south of 50° N (for more than +50 days). Negative anomalies covered the central regions of North America (up –80 days). According to estimates in active blocking sectors, in the first half of 2020, blocking in the European sector (10° W–60° E; 50°–65° N) was weakened relative to the multiyear average. In the summer and autumn seasons, positive anomalies of blocking indices were noted in this region. In the North American sector (100°–160° W; 50°–65° N), negative anomalies were observed in all seasons except for spring. Estimates of the linear trend of blocking indices at the nodes of the regular grid and in general in the latitudinal belt and its sectors were analyzed for 1949–2020 and 1976–2020. On average, negative trends prevailed in all seasons, but the spatial distribution of the trend coefficients varied from season to season. The trend of the annual duration of blocking episodes in the latitude zone 50°–65° N is 1.0 days/10 years and is statistically significant at a 1% level.
期刊介绍：
Izvestiya, Atmospheric and Oceanic Physics is a journal that publishes original scientific research and review articles on vital issues in the physics of the Earth’s atmosphere and hydrosphere and climate theory. The journal presents results of recent studies of physical processes in the atmosphere and ocean that control climate, weather, and their changes. These studies have possible practical applications. The journal also gives room to the discussion of results obtained in theoretical and experimental studies in various fields of oceanic and atmospheric physics, such as the dynamics of gas and water media, interaction of the atmosphere with the ocean and land surfaces, turbulence theory, heat balance and radiation processes, remote sensing and optics of both media, natural and man-induced climate changes, and the state of the atmosphere and ocean. The journal publishes papers on research techniques used in both media, current scientific information on domestic and foreign events in the physics of the atmosphere and ocean.
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