A Numerical Experiment on the Nocturnal Low Level Jet Over the Kanto Plain

Kimura, Fujio; Arakawa, S.

doi:10.2151/jmsj1965.61.6_848

Cited by 49 publications

(29 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Kimura and Arakawa (1983), and Kondo and Mizuno (1990) showed that the wind gained speed over the southeastern part of the Kanto plain for 5-10 m s À1 southwesterly geostrophic flow. The primary factor in this kind of low-level jet formation was the mechanical effect of the mountains in central Japan upon synoptic-scale winds.…”

Section: B Features Of the Wind Fieldmentioning

confidence: 98%

Vertical Structure of Local Fronts Observed in Kanto, Japan

Seino¹,

Yoshikado

Kobayashi

et al. 2003

Journal of the Meteorological Society of Japan

View full text Add to dashboard Cite

This paper focuses on two cases of a local front that formed ahead of a synoptic cold front under a southwesterly inflow in the Kanto region.Vertical sounding data provided by an observation network of the Tsukuba Area Precipitation Studies (TAPS) enabled a detailed investigation of the mesoscale structure in the vicinity of the local front from its formation through dissipation. Despite some differences in synoptic features, the local front exhibited essential similarities in vertical structure between the two cases, as well as in horizontal structure. The local front, with WSW-ENE orientation, was well defined even in the daytime. A stable layer with a thickness of about 400 m formed on the cold side of the developed local front. As in the upper layer of warm inflow, southwesterly winds prevailed in this stable layer, except for the lowest 50-200 m. The maintenance mechanism of the local front is discussed. The evolution of the local front largely depends on the development of the stable layer on its cold side. In both cases, frontal formation began in the nighttime. A nocturnal cooling on the land surface contributed to forming a cold air mass on the northern side of the local front. In addition, the southwesterly inflow caused warming just above the surface-based cooling layer, which intensified the stratification. Furthermore, the observed vertical structure suggests that the locally modified circulation affected the frontal evolution. Two orographic effects on the circulation, 1) intensification of the inflow over the eastern part, and 2) downslope wind over the western part, both related to the mountains in the west of the Kanto region are expected. Especially, the downslope wind can reasonably explain the daytime persistence of the local front through the enhancement of stratification by adiabatic warming, and resultant influences on the mass transport.

show abstract

Section: B Features Of the Wind Fieldmentioning

confidence: 98%

Vertical Structure of Local Fronts Observed in Kanto, Japan

Seino¹,

Yoshikado

Kobayashi

et al. 2003

Journal of the Meteorological Society of Japan

View full text Add to dashboard Cite

show abstract

“…The model was developed by Kimura and Arakawa 3) and modified by Kimura and Kuwagata. 4) LCM is a three dimensional, non-hydrostatic, primitive equation model with a terrain following a coordinate system.…”

Section: Appendix 1 Model Description (1) Atmospheric Model (Local Cmentioning

confidence: 99%

Ocean Model Coupling with Atmospheric Model for Prediction of Radioactivity Contaminant Dispersion in Emergency

Lee

Kobayashi

Chino

et al. 2005

Journal of Nuclear Science and Technology

View full text Add to dashboard Cite

In order to predict the atmospheric and oceanic dispersion of radionuclides due to a nuclear accident, a coupling model between mesoscale atmosphere and ocean were proposed. And we have carried out several numerical experiments under different atmospheric conditions. The results are summarized as follows: (1) Wind stress transferred through the sea surface does not always have an influence on every area in the ocean, but the influence of wind stress on mean current variation is not negligible, especially over shallow water. (2) Sea surface winds tend to have a greater impact on the dispersion of radioactivity contaminants than normal sea currents. (3) The calculation time for the CPU is about 15% less for this combination system than for systems without the coupling library Stampi.

show abstract

“…The governing equations and numerical scheme of the model are the same as those developed by Kikuchi et al (1981), and modified by Kimura and Arakawa (1983). The governing equations are Boussinesq hydrostatic equations written in a terrain-following coordinate system, as follows: The radiation condition given by Orlanski (1976) is adopted for windward and leeward lateral boundaries.…”

Section: Numerical Modelmentioning

confidence: 99%

A Numerical Study on the Kármán Vortex Generated by Divergence of Momentum Flux in Flow Past an Isolated Mountain

Kang

Kimura

Takahashi

1998

Journal of the Meteorological Society of Japan

Self Cite

View full text Add to dashboard Cite

We investigated formation mechanism of vortex streets in the lee of mountains by using a threedimensional numerical model. The model is based upon the hydrostatic Boussinesq equations in which the vertical turbulent mixing is parameterized using the level 2.5 model of Mellor and Yamada (1982), but the horizontal viscosity is assumed constant.Karman vortex streets can form even without surface friction in a constant ambient flow with uniform stratification. The flow in the lee of the mountain is decelerated due to divergence of the total vertical momentum flux associated with mountain drag. The divergence of momentum flux can be explained by the wave saturation theory given by Lindzen (1981) with some modification. Simulations in this study show that the momentum flux in the lower levels is much larger than the saturated momentum flux, whereas it is almost equal to the saturation value at the upper levels as expected from the saturation theory. This means that large flux divergence is produced between surface layer and upper levels (about 2.5km). As a result, the mean flow is decelerated behind the mountain and the horizontal wind shear forms. When the decelerated flow has a strong enough horizontal shear, the Karman vortex will form due to an absolute instability as mentioned by Schar and Durran (1997).In case of a three-dimensional, bell-shaped mountain, the wave breaking occurs if the Froude number (FT=U/Nh) is less than about 0.8, while a Karman vortex forms if FT is less than about 0.22. The results of the momentum budget calculated by the hydrostatic model are almost the same as nonhydrostatic results as long as the horizontal scale of the mountain is larger than 10 km. A well developed Karman vortex similar to the hydrostatic one was simulated in the nonhydrostatic case. Therefore, we conclude that the hydrostatic assumption is adequate to investigate the origin of the Karman vortex from the viewpoint of momentum budget.

show abstract

A Numerical Experiment on the Nocturnal Low Level Jet Over the Kanto Plain

Cited by 49 publications

References 16 publications

Vertical Structure of Local Fronts Observed in Kanto, Japan

Vertical Structure of Local Fronts Observed in Kanto, Japan

Ocean Model Coupling with Atmospheric Model for Prediction of Radioactivity Contaminant Dispersion in Emergency

A Numerical Study on the Kármán Vortex Generated by Divergence of Momentum Flux in Flow Past an Isolated Mountain

Contact Info

Product

Resources

About

A Numerical Experiment on the Nocturnal Low Level Jet Over the Kanto Plain

Cited by 49 publications

References 16 publications

Vertical Structure of Local Fronts Observed in Kanto, Japan

Vertical Structure of Local Fronts Observed in Kanto, Japan

Ocean Model Coupling with Atmospheric Model for Prediction of Radioactivity Contaminant Dispersion in Emergency

A Numerical Study on the K&aacute;rm&aacute;n Vortex Generated by Divergence of Momentum Flux in Flow Past an Isolated Mountain

Contact Info

Product

Resources

About

A Numerical Study on the Kármán Vortex Generated by Divergence of Momentum Flux in Flow Past an Isolated Mountain