Quasigeostrophic Forcing of Ascent in the Occluded Sector of Cyclones and the Trowal Airstream

Jonathan E. Martin Department of Atmospheric and Oceanic Sciences, University of Wisconsin—Madison, Madison, Wisconsin

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Abstract

A numerical model-based analysis of the quasigeostrophic forcing for ascent in the occluded quadrant of three cyclones is presented based upon a natural coordinate partitioning of the Q vector into its along- and across-isentrope components, Qs and Qn, respectively. The Qn component describes the geostrophic contribution to the rate of change of the magnitude of pθ (traditional frontogenesis), whereas the Qs component describes the geostrophic contribution to the rate of change of direction of pθ (rotational frontogenesis). It is shown that convergence of Qs simultaneously creates the isobaric thermal ridge characteristic of the thermal structure of occluded cyclones and provides the predominant dynamical support for ascent within the occluded quadrant. The absence of significant Qn convergence there suggests that quasigeostrophic (Q-G) frontogenesis plays a subordinate role both in forcing vertical motions and in affecting three-dimensional structural changes in the occluded sector of post-mature phase midlatitude cyclones.

A cyclonically ascending, cloud- and precipitation-producing airstream that originates in the warm-sector boundary layer and flows through the trowal portion of the occluded structure is supported by the upward vertical motions implied by the identified Q-G forcing. This airstream is referred to as the “trowal airstream” and it is shown to be responsible for the production of the “wrap around” cloud and precipitation commonly associated with occluded systems. The relationship of the trowal airstream to previously identified cloud and precipitation producing airflows in cyclones is discussed.

Corresponding author address: Dr. Jonathan E. Martin, Dept. of Atmospheric and Oceanic Sciences, University of Wisconsin—Madison, 1225 W. Dayton St., Madison, WI 53706.

Abstract

A numerical model-based analysis of the quasigeostrophic forcing for ascent in the occluded quadrant of three cyclones is presented based upon a natural coordinate partitioning of the Q vector into its along- and across-isentrope components, Qs and Qn, respectively. The Qn component describes the geostrophic contribution to the rate of change of the magnitude of pθ (traditional frontogenesis), whereas the Qs component describes the geostrophic contribution to the rate of change of direction of pθ (rotational frontogenesis). It is shown that convergence of Qs simultaneously creates the isobaric thermal ridge characteristic of the thermal structure of occluded cyclones and provides the predominant dynamical support for ascent within the occluded quadrant. The absence of significant Qn convergence there suggests that quasigeostrophic (Q-G) frontogenesis plays a subordinate role both in forcing vertical motions and in affecting three-dimensional structural changes in the occluded sector of post-mature phase midlatitude cyclones.

A cyclonically ascending, cloud- and precipitation-producing airstream that originates in the warm-sector boundary layer and flows through the trowal portion of the occluded structure is supported by the upward vertical motions implied by the identified Q-G forcing. This airstream is referred to as the “trowal airstream” and it is shown to be responsible for the production of the “wrap around” cloud and precipitation commonly associated with occluded systems. The relationship of the trowal airstream to previously identified cloud and precipitation producing airflows in cyclones is discussed.

Corresponding author address: Dr. Jonathan E. Martin, Dept. of Atmospheric and Oceanic Sciences, University of Wisconsin—Madison, 1225 W. Dayton St., Madison, WI 53706.

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  • Atkinson, B. W., and P. A. Smithson, 1974: Meso-scale circulations and rainfall patterns in an occluding depression. Quart. J. Roy. Meteor. Soc.,100, 3–22.

  • Barnes, S. L., and B. R. Colman, 1993: Quasigeostrophic diagnosis of cyclogenesis associated with a cutoff extratropical cyclone—The Christmas 1987 storm. Mon. Wea. Rev.,121, 1613–1634.

  • Bjerknes, J., and H. Solberg, 1922: Life cycle of cyclones and the polar front theory of atmospheric circulation. Geofys. Publ.,3, 1–18.

  • Browning, K., 1990: Organization of clouds and precipitation in extratropical cyclones. Extratropical Cyclones: The Erik Palmén Memorial Volume, C. W. Newton and E. O. Holopainen, Eds., Amer. Meteor. Soc., 129–151.

  • ——, and T. W. Harrold, 1969: Air motion and precipitation growth in a wave depression. Quart. J. Roy. Meteor. Soc.,95, 288–309.

  • Carlson, T. N., 1980: Airflow through midlatitude cyclones and the comma cloud pattern. Mon. Wea. Rev.,108, 1498–1509.

  • Chen, C., and W. R. Cotton, 1983: A one-dimensional simulation of the stratocumulus capped mixed layer. Bound.-Layer Meteor.,25, 289–321.

  • Cotton, W. R., G. J. Tripoli, R. M. Rauber, and E. A. Mulvihill, 1986:Numerical simulation of the effects of varying ice crystal nucleation rates and aggregation processes on orographic snowfall. J. Climate Appl. Meteor.,25, 1658–1680.

  • Crocker, A. M., W. L. Godson, and C. M. Penner, 1947: Frontal contour charts. J. Meteor.,4, 95–99.

  • Eliassen, A., 1962: On the vertical circulation in frontal zones. Geofys. Publ.,24, 147–160.

  • Emanuel, K. A., 1991: A scheme for representing cumulus convection in large-scale models. J. Atmos. Sci.,48, 2313–2335.

  • Flatau, P., G. J. Tripoli, J. Verlinde, and W. R. Cotton, 1989: The CSU RAMS cloud microphysical module: General theory and code documentation. Tech. Rep. 451, Dept. of Atmospheric Science, Colorado State University, 88 pp. [Available from Dept. of Atmospheric Science, Colorado State University, Fort Collins, CO 80523.].

  • Galloway, J. L., 1958: The three-front model: Its philosophy, nature, construction and use. Weather,13, 3–10.

  • ——, 1960: The three-front model, the developing depression and the occluding process. Weather,15, 293–309.

  • Godson, W. L., 1951: Synoptic properties of frontal surfaces. Quart. J. Roy. Meteor. Soc.,77, 633–653.

  • Harrold, T. W., 1973: Mechanisms influencing the distribution of precipitation within baroclinic disturbances. Quart. J. Roy. Meteor. Soc.,99, 232–251.

  • Holton, J. R., 1992: An Introduction to Dynamical Meteorology. 3d ed. Academic Press, 511 pp.

  • Hoskins, B. J., and M. A. Pedder, 1980: The diagnosis of middle latitude synoptic development. Quart. J. Roy. Meteor. Soc.,106, 707–719.

  • ——, I. Draghici, and H. C. Davies, 1978: A new look at the ω-equation. Quart. J. Roy. Meteor. Soc.,104, 31–38.

  • Iskenderian, H., 1988: Three-dimensional airflow and precipitation structure in a nondeepening cyclone. Wea. Forecasting,3, 18–32.

  • Jewell, R., 1981: Tor Bergeron’s first year in the Bergen School: Towards an historical appreciation. Weather and Weather Maps:A Volume Dedicated to the Memory of Tor Bergeron. Vol. 10, Contributions to Current Research in Geophysics, G. H. Lilequist, Ed., Birkhauser Verlag, 474–490.

  • Keyser, D., M. J. Reeder, and R. J. Reed, 1988: A generalization of Petterssen’s frontogenesis function and its relation to the forcing of vertical motion. Mon. Wea. Rev.,116, 762–780.

  • ——, B. D. Schmidt, and D. G. Duffy, 1992: Quasigeostrophic vertical motions diagnosed from along- and cross-isentrope components of the Q vector. Mon. Wea. Rev.,120, 731–741.

  • Kurz, M., 1988a: Development of cloud distribution and relative motions during the mature and occlusion stage of a typical cyclone development. Preprints, Palmén Memorial Symp. on Extratropical Cyclones, Helsinki, Finland, Amer. Meteor. Soc., 201–204.

  • ——, 1988b: Intercorrelations between cyclogenesis and frontogenesis during a typical development in the westerlies. Preprints, Palmén Memorial Symp. on Extratropical Cyclones, Helsinki, Finland, Amer. Meteor. Soc., 223–226.

  • ——, 1992: Synoptic diagnosis of frontogenetic and cyclogenetic processes. Meteor. Atmos. Phys.,48, 77–91.

  • Martin, J. E., 1998a: The structure and evolution of a continental winter cyclone. Part I: Frontal structure and the classical occlusion process. Mon. Wea. Rev.,126, 303–328.

  • ——, 1998b: The structure and evolution of a continental winter cyclone. Part II: Frontal forcing of an extreme snow event. Mon. Wea. Rev.,126, 329–347.

  • ——, 1998c: On the deformation term in the quasigeostrophic omega equation. Mon. Wea. Rev.,126, 2000–2007.

  • Mass, C. F., and D. M. Schultz, 1993: The structure and evolution of a simulated midlatitude cyclone over land. Mon. Wea. Rev.,121, 889–917.

  • Morris, R. M., 1972: The trowal, an important feature of frontal analysis. Meteor. Mag.,101, 150–153.

  • Namias, J., 1939: The use of isentropic analysis in short term forecasting. J. Aeronaut. Sci.,6, 295–298.

  • National Climatic Data Center, 1996: Storm Data. Vol. 38, No. 10, 135 pp. [Available from National Climatic Data Center, Asheville, NC 28801.].

  • ——, 1997a: Storm Data. Vol. 39, No. 3, 169 pp. [Available from National Climatic Data Center, Asheville, NC 28801.].

  • ——, 1997b: Storm Data. Vol. 39, No. 4, 206 pp. [Available from National Climatic Data Center, Asheville, NC 28801.].

  • Penner, C. M., 1955: A three-front model for synoptic analyses. Quart. J. Roy. Meteor. Soc.,81, 89–91.

  • Reed, R. J., Y.-H. Kuo, and S. Low-Nam, 1994: An adiabatic simulation of the ERICA IOP 4 storm: An example of quasi-ideal frontal cyclone development. Mon. Wea. Rev.,122, 2688–2708.

  • Rotunno, R., W. C. Skamarock, and C. Snyder, 1994: An analysis of frontogenesis in numerical simulations of baroclinic waves. J. Atmos. Sci.,51, 3373–3398.

  • Sadourny, R., 1975: The dynamics of finite-difference models of the shallow-water equations. J. Atmos. Sci.,32, 680–689.

  • Sawyer, J. S., 1956: The vertical circulation at meteorological fronts and its relation to frontogenesis. Proc. Roy. Soc. London,234A, 346–362.

  • Schultz, D., and C. Mass, 1993: The occlusion process in a midlatitude cyclone over land. Mon. Wea. Rev.,121, 918–940.

  • Sutcliffe, R. C., 1947: A contribution to the problem of development. Quart. J. Roy. Meteor. Soc.,73, 370–383.

  • Tremback, C. J., and R. Kessler, 1985: A surface temperature and moisture parameterization for use in mesoscale numerical models. Preprints, Seventh Conf. on Numerical Weather Prediction, Montreal, PQ, Canada, Amer. Meteor. Soc., 355–358.

  • ——, J. Powell, W. R. Cotton, and R. A. Pielke, 1987: The forward-in-time upstream advection scheme: Extension to higher orders. Mon. Wea. Rev.,115, 540–555.

  • Trenberth, K. E., 1978: On the interpretation of the diagnostic quasi-geostrophic omega equation. Mon. Wea. Rev.,106, 131–137.

  • Tripoli, G. J., 1992a: An explicit three-dimensional nonhydrostatic numerical simulation of a tropical cyclone. Meteor. Atmos. Phys.,49, 229–254.

  • ——, 1992b: A nonhydrostatic numerical model designed to simulate scale interaction. Mon. Wea. Rev.,120, 1342–1359.

  • Wernli, H., 1997: A Lagrangian-based analysis of extratropical cyclones. Part II: A detailed case study. Quart. J. Roy. Meteor. Soc.,123, 1677–1706.

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