The field of Н500 geopotential height over the central part of the second natural synoptic region in January during 1950–2019 is analysed to determine regime characteristics of the Okhotsk tropospheric cyclone and its role in the formation of air temperature anomalies over the eastern coast of Asia. A mechanism of occurrence of extreme surface air temperatures using this technique is presented. Extremely low air temperature in the area of the minimum and related deep through are formed during the years when the Н500 minimum is localized over the Sea of Okhotsk. A methodology for constructing ellipses approximating the Н500 level lines in a small neighborhood of the Н500 minimum is developed, the ellipse characteristics are calculated, and their relation to the tropospheric cyclone evolution is analysed. The characteristics of the ellipses constructed in the neighborhood of the geopotential height minimum outside the Sea of Okhotsk significantly differ from those of the ellipses over the Sea of Okhotsk. A high compression of the ellipses towards the major axis is reported when the Far Eastern through intensity is reduced. In this case, an outflow of warm oceanic air masses to the Sea of Okhotsk is observed. The location of the Н500 minimum and the characteristics of the ellipses located within the center circle may be used to explain reasons for dramatic changes in air temperature in the study region. Keywords: Оkhotsk tropospheric cyclone, Н500 minima centers, extreme surface air temperature, ellipse characteristics
Сахалинский научно-исследовательский институт рыбного хозяйства и океанографии (ФГБНУ «СахНИРО»), г. Южно-Сахалинск 2 Тихоокеанский научно-исследовательский рыбохозяйственный центр (ФГБНУ «ТИНРО-Центр»), г. Владиво сток 3 Институт прикладной математики ДВО РАН (ФГБУН «ИПМ ДВО РАН»), г. Владивосток
Trend significance is evaluated and periodicities are revealed for time series of the sea surface temperature in the North-West Pacific. The dominant periods are selected using Fourier method under the assumption of linear trend existing over sufficiently large fluctuations. On the background of rapid warming in the 1983-2014, increasing fluctuations of summer SST were observed, with 7-year cycle domination, which were gradually shifted to August-September. Patterns of atmospheric circulation preceding to events of extreme thermal regime in summer are identified using the method of interval recognition: the extreme warm thermal regimes are formed mainly by subtropical anticyclones having a tendency to strengthen, and the extreme cold regimes are conditioned by strengthening of summer monsoon in its first stage.
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