Statistical Characteristics of Blocking High in the Ural Mountains during Winters and Relationship with Changes in Sea Surface Temperature and Sea Ice

Abstract

A blocking high in the Ural Mountains, which is recognized as the third major blocking high area in the northern hemisphere, describes a deep warm high-pressure system superimposed on the westerly belt. Based on the ERA-5 daily reanalysis data (the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis global climate dataset) and using the Tibaldi and Molteni (TM) method, we selected 43 blocking high events in the Ural Mountains during the extended winters of 1979–2020 and analyzed their atmospheric circulation characteristics and influencing factors. Our findings revealed a downward trend in the frequency of occurrence of blocking highs in the Ural Mountains in winter, most of them were short-lived; furthermore, the frequency and duration of these occurrences generally followed a 3–4 years oscillating cycle. The synthetic results of the geopotential height (HGT) anomaly field and the surface air temperature (SAT) anomaly field of these 43 extended wintertime blocking high events in the Ural Mountains region showed that during the development of a blocking high, the central intensity of the positive anomalies in the Ural Mountains region first increased and then weakened, while the central intensity and meridional span of the negative anomalies in the Eurasian mid-latitudes of the SAT anomaly field increased continuously. In addition, abnormally high sea surface temperature (SST) in the North Atlantic sea area and abnormal reduction of sea ice (SI) in the Barents-Kara Sea and the Chukchi Sea in autumn had a significant impact on the wintertime formation of Ural Mountains blocking highs. In contrast, in autumn, the abnormal reduction of SI in the Barents-Kara and Chukchi Seas might also have led to the westward positioning of Ural Mountains blocking highs.