Changes in the frequency and persistence of the Vangengeim-Girs macro-circulation forms in the period 1979–2023
Changes in the frequency and persistence of the Vangengeim-Girs macro-circulation forms in the period 1979–2023

Summary/Abstract: The significantly faster increase in Arctic temperature compared to the global average is causing changes in wind patterns in the mid-latitudes of the upper troposphere. Studies suggest possible changes in the geometry of wind fields, evident in the waviness of geopotential lines or in a series of discrete circulation patterns. This study aligns with the latter research focus. The objective of the analysis is to estimate long-term trends in the Vangengeim-Girs (V-G) macroforms from 1979 to 2023, and since 1999, which is considered a breaking point in the course of Arctic warming. Trend coefficients were estimated for the 45-year period and in moving 21-year window for characteristics describing V-G forms variability. The results indicate a nonlinear trend in the annual frequency of W and E forms, the number of E episodes, and the duration of C and W episodes. Other parameters maintained a consistent direction of change (+/−) throughout the study period: frequency of C(+), number of W(+), C(+), WEC(+) episodes, duration of WEC(−) and E(−). Processes indicating an increase in meridionality include the decline in W frequency after 2005, the rise in E frequency after 2003, the increase in C frequency and the number of C episodes from 1979 to 2023, and the rise in the number of E episodes along with a significant decline in W episode duration after 1999. Additionally, significant trends in the increase (decrease) in the number (duration) of all episodes suggest an increase in day-to-day circulation variability.

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