Response of rapidly developing extratropical cyclones to sea surface temperature variations over the western Kuroshio–Oyashio confluence region

• Published in: Journal of geophysical research. Atmospheres 2016-04, Vol.121 (8), p.3843-3858
• Main Authors: Hirata, Hidetaka, Kawamura, Ryuichi, Kato, Masaya, Shinoda, Taro
• Format: Article
• Language: English
• Subjects: Anomalies; Asymmetric structures; Asymmetry; Belt conveyors; Brackish; cold conveyor belt; Confluence; Cyclones; Dry air; Drying; explosively developing extratropical cyclone; Extratropical cyclones; Geophysics; Heat transfer; inner structure of explosive cyclone; Latent heat; Latent heat release; Marine; Moisture; moisture supply from warm currents; Oceans; Sea level; Sea level pressure; Sea surface; Sea surface temperature; Sea surface temperature anomalies; Sea surface temperature variations; SST variation over the Kuroshio–Oyashio confluence region; Strong winds; Surface temperature; Temperature; Temperature variations; Variation; Wind
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2015JD024391

The dynamical response of rapidly developing extratropical cyclones to sea surface temperature (SST) variations over the western Kuroshio–Oyashio confluence (WKOC) region was examined by using regional cloud‐resolving simulations. This study specifically highlights an explosive cyclone that occurred in early February 2014 and includes a real SST experiment (CNTL run) and two sensitivity experiments with warm and cool SST anomalies over the WKOC region (warm and cool runs). The results derived from the CNTL run indicated that moisture supply from the ocean was enhanced when the dry air associated with the cold conveyor belt (CCB) overlapped with warm currents. Further, the evaporated moisture contributed substantially to latent heat release over the bent‐back front with the aid of the CCB, leading to cyclone intensification and strengthening of the asymmetric structure around the cyclone's center. Such successive processes were more active in the warm run than in the cool run. The dominance of the zonally asymmetric structure resulted in a difference in sea level pressure around the bent‐back front between the two runs. The WKOC SST variations have the potential to affect strong wind distributions along the CCB through modification of the cyclone's inner system. Additional experiments with two other cyclones showed that the cyclone response to the WKOC SST variations became evident when the CCB north of the cyclone's center overlapped with that region, confirming that the dry nature of the CCB plays an important role in latent heat release by allowing for larger moisture supply from the ocean. Key Points Moisture supply from warm currents influences the development and inner structure of explosive cyclones Midlatitude SST variations can modulate the inner structures of cyclones Midlatitude SST variations can affect strong wind distributions associated with cyclones