A Diagnostic Study of Moist Potential Vorticity Generation in an Extratropical Cyclone

Zuohao Cao; G.W.K. Moore

doi:10.1007/s00376-998-0036-2

Impact Factor: 5.8

Volume 15 Issue 2

Apr. 1998

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Article > ADVANCES IN ATMOSPHERIC SCIENCES > 1998 > 15(2): 152-166

A Diagnostic Study of Moist Potential Vorticity Generation in an Extratropical Cyclone

1.
Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7,Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7

doi: 10.1007/s00376-998-0036-2

Abstract
References
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Abstract:
Moist potential voracity (MPV) and Its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if the flow is three-dimensional and the air is unsaturated. Moist potential vorticity can be generated through the combined effects of gradients in the potential temperature and moisture fields. The diagnosis of MPV generation in an extratropical cy-clone was performed with the ECMWF objectively analyzed fields for a system that developed during February 1992. It was found that at various stages during the development of the cyclone, negative MPV was generated: at the north end of the cold front; along the occluded front and the cold front; and in the region of the warm core. This pattern of negative MPV generation is in excellent agreement with the predictions of previous theoretical and numerical studies. After the cyclone ceased to deepen, the region of negative MPV generated in the cyclone was horizontally adverted in-to a saturated area. The area of negative MPV generated both along the occluded front in this case study and in the region of the bent-back warm front in a numerical simulation showed a mesoscale structure with a width of about 200-500 km. It was found that the intrusion of moist or dry air into baroclinic zones was important for MPV genera-tion. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gra-dients led to significant MPV production.
- Moist potential vorticity (MPV) generation,
- Extratropical cyclones
References

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Manuscript History

Manuscript received: 10 April 1998

Manuscript revised: 10 April 1998

通讯作者: 陈斌, bchen63@163.com

1.
沈阳化工大学材料科学与工程学院沈阳 110142

A Diagnostic Study of Moist Potential Vorticity Generation in an Extratropical Cyclone

1. Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7,Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7

Manuscript received: 1998-04-10
Manuscript revised: 1998-04-10

Abstract: Moist potential voracity (MPV) and Its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if the flow is three-dimensional and the air is unsaturated. Moist potential vorticity can be generated through the combined effects of gradients in the potential temperature and moisture fields. The diagnosis of MPV generation in an extratropical cy-clone was performed with the ECMWF objectively analyzed fields for a system that developed during February 1992. It was found that at various stages during the development of the cyclone, negative MPV was generated: at the north end of the cold front; along the occluded front and the cold front; and in the region of the warm core. This pattern of negative MPV generation is in excellent agreement with the predictions of previous theoretical and numerical studies. After the cyclone ceased to deepen, the region of negative MPV generated in the cyclone was horizontally adverted in-to a saturated area. The area of negative MPV generated both along the occluded front in this case study and in the region of the bent-back warm front in a numerical simulation showed a mesoscale structure with a width of about 200-500 km. It was found that the intrusion of moist or dry air into baroclinic zones was important for MPV genera-tion. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gra-dients led to significant MPV production.

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