• Alpert, P., 1986: Mesoscale indexing of the distribution of orographic precipitation over high mountains. J. Climate Appl. Meteor., 25 , 532545.

    • Search Google Scholar
    • Export Citation
  • Asencio, N., J. Stein, M. Chong, and F. Gheusi, 2003: Analysis and simulation of local and regional conditions for the rainfall over the Lago Maggiore Target Area during MAP IOP 2b. Quart. J. Roy. Meteor. Soc., 129 , 565586.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., and M. J. Miller, 1993: The Betts–Miller scheme. The Representation of Cumulus Convection in Numerical Models, Meteor. Monogr., No. 46, Amer. Meteor. Soc., 107–121.

  • Binder, P., and C. Schär, Eds. 1996: MAP design proposal. MeteoSwiss, 75 pp. [Available from the MAP Programme Office, MeteoSwiss, CH-8044, Zurich, Switzerland.].

  • Blackadar, A. K., 1979: High resolution models of the planetary boundary layer. Adv. Environ. Sci. Eng., 1 , 5085.

  • Bougeault, P., and Coauthors, 2001: The MAP special observing period. Bull. Amer. Meteor. Soc., 82 , 433462.

  • Bousquet, O., and B. F. Smull, 2003: Observations and impacts of upstream blocking during a widespread orographic precipitation event. Quart. J. Roy. Meteor. Soc., 129 , 391410.

    • Search Google Scholar
    • Export Citation
  • Buzzi, A., N. Tartaglione, and P. Marguzzi, 1998: Numerical simulations of the 1994 Piedmont flood: Role of orography and moist processes. Mon. Wea. Rev., 126 , 23692383.

    • Search Google Scholar
    • Export Citation
  • Chen, S. H., and Y-L. Lin, 2005a: Orographic effects on a conditionally unstable flow over an idealized three-dimensional mesoscale mountain. Meteor. Atmos. Phys., 88 , 121.

    • Search Google Scholar
    • Export Citation
  • Chen, S. H., and Y-L. Lin, 2005b: Effects of moist Froude number and CAPE on a conditionally unstable flow over a mesoscale mountain. J. Atmos. Sci., 62 , 331350.

    • Search Google Scholar
    • Export Citation
  • Chu, C-M., and Y-L. Lin, 2000: Effects of orography on the generation and propagation of mesoscale convective systems in a two-dimensional conditionally unstable flow. J. Atmos. Sci., 57 , 38173837.

    • Search Google Scholar
    • Export Citation
  • Doswell III, C. A., R. Romero, and S. Alonso, 1998: A diagnostic study of three heavy precipitation episodes in the western Mediterranean region. Wea. Forecasting, 13 , 560581.

    • Search Google Scholar
    • Export Citation
  • Dudhia, J., 1993: A nonhydrostatic version of the Penn State–NCAR Mesoscale Model: Validation tests and simulation of an Atlantic cyclone and cold front. Mon. Wea. Rev., 121 , 14931513.

    • Search Google Scholar
    • Export Citation
  • Frei, C., and E. Häller, 2001: Mesoscale precipitation analysis from MAP SOP rain-gauge data. MAP Newsletter, No. 15, MeteoSwiss, Zurich, Switzerland, 257–260.

  • Gheusi, F., and J. Stein, 2003: Small-scale rainfall mechanisms for an idealized convective southerly flow over the Alps. Quart. J. Roy. Meteor. Soc., 129 , 18191840.

    • Search Google Scholar
    • Export Citation
  • Grell, G. A., 1993: Prognostic evaluation of assumptions used by cumulus parameterizations. Mon. Wea. Rev., 121 , 764787.

  • Lin, Y-L., R. D. Farley, and H. D. Orville, 1983: Bulk parameterization of the snow field in a cloud model. J. Climate Appl. Meteor., 22 , 4063.

    • Search Google Scholar
    • Export Citation
  • Lin, Y-L., S. Chiao, T-A. Wang, M. L. Kaplan, and R. P. Weglarz, 2001: Some common ingredients for heavy orographic rainfall and their potential application for prediction. Wea. Forecasting, 16 , 633660.

    • Search Google Scholar
    • Export Citation
  • Medina, S., and R. A. Houze, 2003: Air motions and precipitation growth in Alpine storms. Quart. J. Roy. Meteor. Soc., 129 , 345372.

  • Neiman, P. J., F. M. Ralph, A. B. White, D. E. Kingsmill, and P. O. G. Persson, 2002: The statistical relationship between upslope flow and rainfall in California’s coastal mountains: Observations during CALJET. Mon. Wea. Rev., 130 , 14681492.

    • Search Google Scholar
    • Export Citation
  • Reeves, H. D., and Y-L. Lin, 2004: Effects of diabatic cooling on the formation of convective system upstream of the Apennines during MAP IOP-8. Preprints, 11th Conf. on Mountain Meteorology, Bartlett, NH, Amer. Meteor. Soc., CD-ROM, 13.1.

  • Rottman, J. W., and R. B. Smith, 1989: A laboratory model of severe downslope winds. Tellus, 41A , 401415.

  • Rotunno, R., and R. Ferretti, 2001: Mechanisms of intense Alpine rainfall. J. Atmos. Sci., 58 , 17321749.

  • Rotunno, R., and R. Ferretti, 2003: Orographic effects on rainfall in MAP cases IOP2B and IOP8. Quart. J. Roy. Meteor. Soc., 129 , 373390.

    • Search Google Scholar
    • Export Citation
  • Smith, R. B., 1979: The influence of mountains on the atmosphere. Advances in Geophysics, Vol. 21, Academic Press, 87–230.

  • Smith, R. B., 1985: On severe downslope winds. J. Atmos. Sci., 42 , 25972603.

  • Stein, J., 2004: Exploration of some convective regimes over the Alpine orography. Quart. J. Roy. Meteor. Soc., 130 , 481502.

  • Tao, W-K., and J. Simpson, 1993: Goddard Cumulus Ensemble Model. Part I. Terr. Atmos. Oceanic Sci., 4 , 3572.

  • Tripoli, G. J., G. Panegrossi, A. Mugnai, S. Dietrich, and E. Smith, 2000: Orographically induced flash floods on the northern Italian coast. Preprints, 9th Conf. on Mountain Meteorology, Aspen, CO, Amer. Meteor. Soc., 336–339.

  • Van Tuyl, A. H., and J. A. Young, 1982: Numerical simulation of nonlinear jet streak adjustment. Mon. Wea. Rev., 110 , 20382054.

  • Wolyn, P. G., and T. B. McKee, 1989: Deep stable layers in the intermountain western United States. Mon. Wea. Rev., 117 , 461472.

  • Zängl, G., 2003: The impact of upstream blocking, drainage flow and the geostrophic pressure gradient on the persistence of cold pools. Quart. J. Roy. Meteor. Soc., 129 , 117137.

    • Search Google Scholar
    • Export Citation
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Formation Mechanisms for Convection over the Ligurian Sea during MAP IOP-8

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  • 1 Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina
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Abstract

The dynamical impacts of an unusually strong stable layer that developed over the Po Valley and northern Ligurian Sea during Mesoscale Alpine Program (MAP) intensive observation period 8 (IOP-8) on the formation of convection over the Ligurian Sea are explored. Based on numerically simulated equivalent potential temperature, wind vectors, and by a trajectory analysis of parcels both beneath and above the stable layer, it is shown that the stable layer behaved as a material surface or “effective mountain” to the airstreams impinging on it from the south. Additional analyses show that the leading edge of the stable layer was collocated with maxima in upward motion and a strong positive moisture flux. Hence, it was further argued and demonstrated through inspection of soundings upstream of the cold dome and trajectory analyses that lifting by the stable layer enhanced convective activities over the Ligurian Sea. Finally, processes contributing to the maintenance of the stable layer during IOP-8 were explored. It was found that the differential advection of a warm, less stable air mass on top of a cooler, more stable air mass helped maintain the stable layer. The Ligurian Apennines made a secondary contribution to the stagnation of the cool air in the Po Valley by partially blocking this air mass from exiting the valley to the south.

Corresponding author address: Dr. Yuh-Lang Lin, Dept. of Marine, Earth, and Atmospheric Sciences, 1125 Jordan Hall, Faucette Drive, NCSU, Raleigh, NC 27695-8208. Email: yl_lin@ncsu.edu

Abstract

The dynamical impacts of an unusually strong stable layer that developed over the Po Valley and northern Ligurian Sea during Mesoscale Alpine Program (MAP) intensive observation period 8 (IOP-8) on the formation of convection over the Ligurian Sea are explored. Based on numerically simulated equivalent potential temperature, wind vectors, and by a trajectory analysis of parcels both beneath and above the stable layer, it is shown that the stable layer behaved as a material surface or “effective mountain” to the airstreams impinging on it from the south. Additional analyses show that the leading edge of the stable layer was collocated with maxima in upward motion and a strong positive moisture flux. Hence, it was further argued and demonstrated through inspection of soundings upstream of the cold dome and trajectory analyses that lifting by the stable layer enhanced convective activities over the Ligurian Sea. Finally, processes contributing to the maintenance of the stable layer during IOP-8 were explored. It was found that the differential advection of a warm, less stable air mass on top of a cooler, more stable air mass helped maintain the stable layer. The Ligurian Apennines made a secondary contribution to the stagnation of the cool air in the Po Valley by partially blocking this air mass from exiting the valley to the south.

Corresponding author address: Dr. Yuh-Lang Lin, Dept. of Marine, Earth, and Atmospheric Sciences, 1125 Jordan Hall, Faucette Drive, NCSU, Raleigh, NC 27695-8208. Email: yl_lin@ncsu.edu

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