[A-CG52] Science in the Arctic Region

[ACG52-17] Structure and evolution of atmospheric rivers along the Eurasian Arctic frontal zone during summer

*Yoshiki Fukutomi¹, Tetsuya Hiyama¹ (1.Institute for Space-Earth Environmental Reasearch, Nagoya University)

Keywords:Arctic frontal zone, Northern Eurasia, Atmopheric River, Intraseasonal variability, Atmospherc hydrological cycle

This study examines structure and characteristics of ARs which progress along the Eurasian Arctic frontal zone (AFZ). The roles and origin of the ARs are determined by using atmospheric reanalysis (JRA-3Q) and gauge-satellite observed precipitation (MSWEPv2.8) data over 45 summers (June-August) from 1979 to 2023. Combined empirical orthogonal function (cEOF) analysis is performed on daily integrated water vapor transport (IVT) vectors in the Arctic coastal region (65-77.5N, 60-140E) to identify a primary AR pattern. The AR pattern is defined by a leading cEOF mode and the resulting principal component time series is used to detect daily AR events. A total of 79 AR events are detected to construct composite fields of various atmospheric elements. Composite analysis results reveal the structure and evolution of large-scale circulation patterns associated with the AR development along the AFZ. The composite AR pattern exhibits a zonally oriented narrow band of IVT which is well-defined by values exceeding 150 kg/m/s. Northeastward directing AR-IVT vectors indicate that the AR is responsible for moisture intrusion from the northern Eurasia into the Arctic basin. The AR produces precipitation in the western and central Siberian sector of the AFZ. An intraseasonal Rossby wave train arcing across the North Atlantic-Arctic basin generates intense IVT that forms AR along the AFZ. A trough-ridge couplet as part of the wave train amplifies over northwestern Eurasia through Rossby wave energy dispersion. The amplified trough-ridge couplet facilitates the development of northeastward IVT flux that favors the AR formation in the western and central Siberian sector. The precipitation associated with the AR is produced by synoptic-scale waves propagating along the AFZ. The intraseasonal wave train provides favorable conditions for the baroclinic development of the synoptic-scale waves which create extratropical cyclones involving precipitating fronts linked to the AR.