[A-CG46] Science in the Arctic Region

[ACG46-P10] Climatological Characteristics of Atmospheric Rivers over Northern Eurasia during Summer

*Fukutomi Yoshiki¹, Hironari Kanamori¹, Tetsuya Hiyama¹ (1.Institute for Space-Earth Environmental Reasearch, Nagoya University)

Keywords:Northern Eurasia, Atmospheric Rivers, Precipitation Systems , Arctic Frontal Zone, Synoptic-scale Disturbances , Atmospheric Hydrological Cycle

Atmospheric rivers (ARs) have been regarded as a synoptic precipitation producing system which forms a sharp and narrow band structure of strong moisture transport. They tend to be accompanied by development of extratropical cyclones, fronts, and cloud bands which produce heavy precipitation and flooding in the mid-latitude continental coastal regions. It might be expected that ARs induce high-impact weather events also in the higher-latitude continental inland regions. This study examines structure and characteristics of ARs over northern Eurasia during the 43 summer seasons (JJA 1979−2021). Main focus is on the characterization of the continental ARs that are responsible for hydrometeorological impacts in Siberia. The AR events are objectively detected by applying a hierarchical cluster analysis to vertically integrated water vapor transport which intensity exceeds a specific criterion. The resulting AR patterns are classified into five distinct types over northern Eurasia. Relationships between ARs, extratropical cyclones, frontal activity, and cloudiness are investigated on the five AR types by using composite analysis on JRA-55-based atmospheric variables, gridded precipitation analysis (MSWEPv2.8), and satellite-based cloud amount data (ISCCP-H). The ARs are further characterized as inland type and Arctic coastal type. The inland ARs tend to penetrate eastward and northeastward into the warm frontal zone accompanied by the extratropical cyclone development in the western and northwestern side of the ARs. Intense precipitation bands are aligned to the warm frontal zones associate with the inland ARs. The coastal ARs are more zonally oriented and their axis is almost parallel to warm frontal zones. A zonally elongated warm frontal zone occurs associated with extratropical cyclone activity over the Arctic coastal region. An enhanced precipitation band is collocated with the warm frontal zone which axis is located to the north of the AR axis. Activities of deep convective cloud and nimbostratus cloud are enhanced within the precipitation band. They can be main precipitating clouds in the well-developed AR precipitation band over northern Eurasia.