5:15 PM - 7:15 PM
[ACG36-P12] Seasonal and latitudinal differences in the relationship between Atmospheric River intensity and extratropical cyclone strength in East Asia
Keywords:Atmospheric Rivers, Extratropical Cyclones
Atmospheric Rivers (ARs), which are considered to be the cause of heavy rainfall and flooding along the west coast of North America in winter, are often identified in the warm sector of Extratropical Cyclones (ECs) and are focused in the precold frontal low-level jet regions. However, previous studies have shown that Neither the location nor the intensity of an AR over the western coast of North America in winter can be simply determined by an EC. Such knowledge of the relationship between an AR and an EC remains shallow outside the west coast of North America. Similarly, in East Asia, some ARs organized by ECs have been shown to induce heavy rainfall. Clarifying the quantitative relationship between ARs and ECs is important to help understand the mechanism of AR formation and to provide a basis for predicting future heavy rainfall events due to ARs. However, studies on the interrelationship between AR and EC in East Asia are lacking. Therefore, in this study, we focus on ECs in East Asia and examine the statistical relationship between the EC strength and the AR intensity and location in East Asia, and focus on seasonal and regional differences.
Following previous studies, we detected ARs and ECs using the integrated water vapor flux and sea level pressure (SLP) from the Japanese 55-year reanalysis from 1981 to 2020, respectively. We also defined the ARs associated with the EC. The AR intensity is defined as the maximum water vapor flux in the AR, and the EC strength is defined as the difference between the EC central pressure and the SLP area mean at 5° north-south and 20° east-west from the EC center. The AR intensity and EC strength were then compared for each season and latitude zone.
As a result, the EC strength associated with AR tended to be greater and AR intensity tended to increase with EC strength, but the relationship varied by season and latitude. In all seasons at 20~30°N, the relationship between AR intensity and EC strength is clear. The same was true for 30~40°N in summer. At high latitudes (40~50°N) in all seasons, the relationship is unclear. AR intensity is proportional to the EC strength, but the EC strength is not the only factor controlling AR intensity.
Following previous studies, we detected ARs and ECs using the integrated water vapor flux and sea level pressure (SLP) from the Japanese 55-year reanalysis from 1981 to 2020, respectively. We also defined the ARs associated with the EC. The AR intensity is defined as the maximum water vapor flux in the AR, and the EC strength is defined as the difference between the EC central pressure and the SLP area mean at 5° north-south and 20° east-west from the EC center. The AR intensity and EC strength were then compared for each season and latitude zone.
As a result, the EC strength associated with AR tended to be greater and AR intensity tended to increase with EC strength, but the relationship varied by season and latitude. In all seasons at 20~30°N, the relationship between AR intensity and EC strength is clear. The same was true for 30~40°N in summer. At high latitudes (40~50°N) in all seasons, the relationship is unclear. AR intensity is proportional to the EC strength, but the EC strength is not the only factor controlling AR intensity.