Kinetic Energy Budget Analysis on the Development of a Meso-β-Scale Vortex Causing Heavy Rainfall, Observed over Aomori Prefecture in Northern Japan on 11 November 2007

Abstract

On 11 November 2007, record heavy rainfall was observed over Aomori Prefecture in northern Japan. Numerical simulations were performed using a non-hydrostatic model with a horizontal resolution of 5 km (5km-NHM) to clarify the formation mechanisms of this heavy rainfall. The results revealed that a meso-β scale vortical disturbance (MβV) originated over the offshore area with strong horizontal wind shear southeast of Aomori Prefecture at 0600 UTC 11 November. The MβV traveled north-northwestward over the sea and landed in Aomori Prefecture at 1200 UTC. The heavy rainfall was caused by convective systems associated with the MβV.A kinetic energy budget analysis was conducted using the results of 5km-NHM to account for the development of the MβV. Eddy kinetic energy (EKE) increased with time, while mean kinetic energy decreased. This relation implies that the MβV developed in association with kinetic energy conversion from the mean part to the eddy part. Horizontal shear below a height of 1 km played a key role in EKE production, and vertical advection by mean and perturbation flows transported EKE produced in the lower layers to the upper layers. The vertical shear and buoyancy did not significantly contribute to the EKE increase. The pressure gradient force normal to the shear line also contributed to EKE production by accelerating horizontal wind speed. A sensitivity experiment without diabatic heating indicates that convective activities affected the development and maintenance of horizontal shear, which significantly contributed to the MβV development.

Characteristics and environmental conditions of quasi‐stationary convective clusters during the warm season in Japan

“…The environmental conditions necessary to develop QSCSs, particularly during the Baiu season, are characterized by a larger moisture content (Kato, ; Hirockawa and Kato, ). Higher environmental moisture may be a common feature for MCS events over East Asia; for example, Meng et al () showed that precipitable water is higher for the MCSs in east China than for those in the USA.…”

Contributing Factors of the Heavy Rainfall Event at Amami-Oshima Island, Japan, on 20 October 2010

“…Numerous studies of these events (e.g., Syono et al 1959;Ogura et al 1985;Watanabe and Ogura 1987;Nagata and Ogura 1991;Ishihara et al 1995;Kato 1998; Kato and Goda 2001;Kato 2006) have clarified the formation and maintenance mechanisms of heavy rainfall events during the Baiu season. However, heavy rainfall events occurring outside the Baiu season have been little studied (e.g., Seko et al 1999;Tsuguchi and Sakakibara 2005;Hirockawa and Kato 2012), and their formation and maintenance mechanisms are less well understood.…”