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

被引：5

作者：

Cao Z. ^{[1
,2
]}

Moore G.W.K. ^{[1
]}

机构：

[1] Department of Physics, University of Toronto, Toronto

[2] Climate Processes Earth Observ. A., 4905 Dufferin Street, Downsview

来源：

Advances in Atmospheric Sciences | 1998年 / 15卷 / 2期

关键词：

Extratropical cyclones; Moist potential vorticity (MPV) generation;

D O I：

10.1007/s00376-998-0036-2

中图分类号：

学科分类号：

摘要：

Moist potential vorticity (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 cyclone 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 advected into 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 generation. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gradients led to significant MPV production.

引用

页码：152 / 166

页数：14

共 28 条

[11]

(1992) The Description of the ECMWF/WCRP Level III-A Global Atmospheric Data Archive, , Available from the European Center for Medium Range Weather Forecasts

[12]

Emanuel, K.A., Inertial instability and mesoscale convective systems, Part I: Linear theory of inertial instability in rotating viscous fluids (1979) J. Atmos. Sci., 36, pp. 2425-2449

[13]

Hanesiak, J.M., Stewart, R.E., Szeto, K.K., The structure, water budget and radiational features of a high latitude warm front (1997) J. Atmos. Sci., , in press

[14]

Hobbs, P.V., Organization and structure of clouds and precipitation on the mesoscale and microscale in cyclonic storms (1978) Rev. Geophys. Space Phys., 16, pp. 741-755

[15]

Houze, R.A., Hobbs, P.V., Biswas, K.R., Davis, W.M., Mesoscale rainbands in extratropical cyclones (1976) Mon. Wea. Rev., 104, pp. 868-878

[16]

Innocentini, V., Neto, E.D.S.C., A numerical study of the role of humidity in the updraft driven by moist slantwise convection (1992) J. Atmos. Sci., 49, pp. 1092-1106

[17]

Matejka, T.J., Houze, R.A., Hobbs, P.V., Microphysics and dynamics of clouds associated with mesoscale rainbands in extratropical cyclones (1980) J. Roy. Meteor. Soc., 106, pp. 29-56

[18]

Miller, J.E., On the concept of frontogenesis (1948) J. Meteor., 5, pp. 169-171

[19]

Parsons, D.B., Hobbs, P.V., The mesoscale and microscale structure and organization of clouds and precipitation in mid-latitude cyclones. XI: Comparisons between observational and theoretical aspects of rainbands (1983) J. Atmos. Sci., 40, pp. 2377-2397

[20]

Persson, P.O.G., Simulations of the potential vorticity structure and budget of Fronts 87 IOP8 (1995) Q. J. R. Met. Soc., 121, pp. 1041-1081

← 1 2 3 →