Response of the intensity of explosively developing extratropical cyclones to the cold eddy associated with the Kuroshio large meander

Abstract:

It is well known that the Kuroshio often takes the large mender path to the south of Japan. The Kuroshio large mender (KLM) have persisted since August 2017. The KLM is associated with a cyclonic cold-core eddy, causing the decrease in the sea surface temperature (SST). Recent climatological studies pointed that the SST variation induced by the KLM affects the intensity of extratropical cyclones passing over the Kuroshio region. However, we have a limited understanding of physical processes related to the response of individual cyclones to the KLM-induced SST variation. To gain insight into the processes, we highlighted several extratropical cyclones rapidly developing around the Kuroshio region and conducted multiple cloud-resolving numerical experiments in which the SST around the KLM region was modified. The results derived from the numerical experiments showed that the deepening of the central pressure of the cyclones is systematically suppressed with the decrease in the SST around the KLM. The KLM-induced cold SST anomalies suppress the surface sensible and latent heat fluxes, then decreasing temperature and water vapor contents near the surface. This decreased temperature enhances near-surface baroclinicity because it increases the meridional thermal gradient, which is inconsistent with the response of the intensity of the cyclones to the SST anomalies. On the other hand, the decreased water vapor content weakens latent heating within the cyclone system, which is consistent with the response of the cyclone intensity seen in our experiments. These results strongly suggest that the diabatic process plays a vital role in the response of the cyclone intensity to the KLM-induced SST variation.