The Missing Link between Terrain-Induced Potential Vorticity Banners and Banded Convection

Simon K. Siedersleben Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria

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Alexander Gohm Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria

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Abstract

On 1 February 2014, the southern side of the Alps was affected by a severe snowstorm that forced authorities to issue the highest level of avalanche danger in southern parts of Austria. The northern side of the Alps was mostly dry. Nevertheless, radar imagery captured the evolution of quasi-steady convective cloud bands over the northern Alpine foreland with a remarkable length of up to 300 km. This study illuminates the processes that generated these cloud bands based on numerical simulations. The storm was associated with a deep large-scale trough that caused strong southwesterly cross-Alpine flow, orographic precipitation on the southern side, and foehnlike subsidence on the northern side of the Alps. Orographic potential vorticity (PV) banners developed at small-scale topographic features embedded in the Alps and extended downstream over the northern Alpine foreland. Convective cloud bands were aligned parallel to these PV banners. They formed in an environment of inertial instability (negative absolute vorticity) and conditional instability. Sensitivity experiments reveal that the structure and size of these cloud bands are strongly sensitive to the small-scale terrain roughness. Removing small-scale topographic features suppresses the formation of orographic vorticity banners, which in turn suppresses the development of cloud bands. These results suggest that the release of inertial instability at negative orographic vorticity banners was crucial for establishing circulations and associated uplift that triggered conditional instability. To summarize, inertial instability was most likely responsible for the banded structure and conditional instability for the convective nature of these cloud bands.

Denotes Open Access content.

Corresponding author address: Simon K. Siedersleben, Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innrain 52f, Innsbruck 6020, Austria. E-mail: simon.siedersleben@gmail.com

Abstract

On 1 February 2014, the southern side of the Alps was affected by a severe snowstorm that forced authorities to issue the highest level of avalanche danger in southern parts of Austria. The northern side of the Alps was mostly dry. Nevertheless, radar imagery captured the evolution of quasi-steady convective cloud bands over the northern Alpine foreland with a remarkable length of up to 300 km. This study illuminates the processes that generated these cloud bands based on numerical simulations. The storm was associated with a deep large-scale trough that caused strong southwesterly cross-Alpine flow, orographic precipitation on the southern side, and foehnlike subsidence on the northern side of the Alps. Orographic potential vorticity (PV) banners developed at small-scale topographic features embedded in the Alps and extended downstream over the northern Alpine foreland. Convective cloud bands were aligned parallel to these PV banners. They formed in an environment of inertial instability (negative absolute vorticity) and conditional instability. Sensitivity experiments reveal that the structure and size of these cloud bands are strongly sensitive to the small-scale terrain roughness. Removing small-scale topographic features suppresses the formation of orographic vorticity banners, which in turn suppresses the development of cloud bands. These results suggest that the release of inertial instability at negative orographic vorticity banners was crucial for establishing circulations and associated uplift that triggered conditional instability. To summarize, inertial instability was most likely responsible for the banded structure and conditional instability for the convective nature of these cloud bands.

Denotes Open Access content.

Corresponding author address: Simon K. Siedersleben, Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innrain 52f, Innsbruck 6020, Austria. E-mail: simon.siedersleben@gmail.com
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  • Aebischer, U., and C. Schär, 1998: Low-level potential vorticity and cyclogenesis to the lee of the Alps. J. Atmos. Sci., 55, 186207, doi:10.1175/1520-0469(1998)055<0186:LLPVAC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Alcott, T. I., and W. J. Steenburgh, 2013: Orographic influences on a Great Salt Lake–effect snowstorm. Mon. Wea. Rev., 141, 24322450, doi:10.1175/MWR-D-12-00328.1.

    • Search Google Scholar
    • Export Citation
  • Barrett, A. I., S. L. Gray, D. J. Kirshbaum, N. M. Roberts, D. M. Schultz, and J. G. Fairman Jr., 2015: Synoptic versus orographic control on stationary convective banding. Quart. J. Roy. Meteor. Soc., 141, 11011113, doi:10.1002/qj.2409.

    • Search Google Scholar
    • Export Citation
  • Bryan, G. H., J. C. Wyngaard, and J. M. Fritsch, 2003: Resolution requirements for the simulation of deep moist convection. Mon. Wea. Rev., 131, 23942416, doi:10.1175/1520-0493(2003)131<2394:RRFTSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, F., and J. Dudhia, 2001: Coupling an advanced land surface-hydrology model with the Penn State–NCAR MM5 modeling system. Part I: Model implementation and sensitivity. Mon. Wea. Rev., 129, 569585, doi:10.1175/1520-0493(2001)129<0569:CAALSH>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Cosma, S., E. Richard, and F. Miniscloux, 2002: The role of small-scale orographic features in the spatial distribution of precipitation. Quart. J. Roy. Meteor. Soc., 128, 7592, doi:10.1256/00359000260498798.

    • Search Google Scholar
    • Export Citation
  • Fuhrer, O., and C. Schär, 2007: Dynamics of orographically triggered banded convection in sheared moist orographic flows. J. Atmos. Sci., 64, 35423561, doi:10.1175/JAS4024.1.

    • Search Google Scholar
    • Export Citation
  • Gohm, A., and G. Mayr, 2005: Numerical and observational case-study of a deep Adriatic Bora. Quart. J. Roy. Meteor. Soc., 131, 13631392, doi:10.1256/qj.04.82.

    • Search Google Scholar
    • Export Citation
  • Gohm, A., G. Zängl, and G. J. Mayr, 2004: South foehn in the Wipp Valley on 24 October 1999 (MAP IOP 10): Verification of high-resolution numerical simulations with observations. Mon. Wea. Rev., 132, 78102, doi:10.1175/1520-0493(2004)132<0078:SFITWV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Grubišíc, V., 2001: Structure of wake north of the Alps. MAP Newsl., 15, 130133. [Available online at http://www.map.meteoswiss.ch/map-doc/NL15/grubisic.pdf.]

    • Search Google Scholar
    • Export Citation
  • Grubišíc, V., 2004: Bora-driven potential vorticity banners over the Adriatic. Quart. J. Roy. Meteor. Soc., 130, 25712603, doi:10.1256/qj.03.71.

    • Search Google Scholar
    • Export Citation
  • Hoggatt, B. D., and J. A. Knox, 1998: Non-hydrostatic simulation of unforecast convection in an intense mid-latitude anticyclone. Preprints, 16th Conf. on Weather Analysis and Prediction/12th Conf. on Numerical Weather Prediction, Phoenix, AZ, Amer. Meteor. Soc, 59–62.

  • Houze, R. A., Jr., 2012: Orographic effects on precipitating clouds. Rev. Geophys., 50, RG1001, doi:10.1029/2011RG000365.

  • Hunt, J., H. Olafsson, and P. Bougeault, 2001: Coriolis effects on orographic and mesoscale flows. Quart. J. Roy. Meteor. Soc., 127, 601633, doi:10.1002/qj.49712757218.

    • Search Google Scholar
    • Export Citation
  • Hunt, J., A. Orr, J. Rottman, and R. Capon, 2004: Coriolis effects in mesoscale flows with sharp changes in surface conditions. Quart. J. Roy. Meteor. Soc., 130, 27032731, doi:10.1256/qj.04.14.

    • Search Google Scholar
    • Export Citation
  • Iacono, M. J., J. S. Delamere, E. J. Mlawer, M. W. Shephard, S. A. Clough, and W. D. Collins, 2008: Radiative forcing by long-lived greenhouse gases: Calculations with the AER radiative transfer models. J. Geophys. Res., 113, D13103, doi:10.1029/2008JD009944.

    • Search Google Scholar
    • Export Citation
  • Jascourt, S. D., S. S. Lindstrom, C. J. Seman, and D. D. Houghton, 1988: An observation of banded convective development in the presence of weak symmetric stability. Mon. Wea. Rev., 116, 175191, doi:10.1175/1520-0493(1988)116<0175:AOOBCD>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Jiang, Q., R. B. Smith, and J. Doyle, 2003: The nature of the mistral: Observations and modelling of two MAP events. Quart. J. Roy. Meteor. Soc., 129, 857875, doi:10.1256/qj.02.21.

    • Search Google Scholar
    • Export Citation
  • Johns, R. H., and C. A. Doswell, 1992: Severe local storms forecasting. Wea. Forecasting, 7, 588612, doi:10.1175/1520-0434(1992)007<0588:SLSF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kain, J. S., 2004: The Kain–Fritsch convective parameterization: An update. J. Atmos. Sci., 43, 170181, doi:10.1175/1520-0450(2004)043<0170:TKCPAU>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kirshbaum, D. J., and D. R. Durran, 2005a: Atmospheric factors governing banded orographic convection. J. Atmos. Sci., 62, 37583774, doi:10.1175/JAS3568.1.

    • Search Google Scholar
    • Export Citation
  • Kirshbaum, D. J., and D. R. Durran, 2005b: Observations and modeling of banded orographic convection. J. Atmos. Sci., 62, 14631479, doi:10.1175/JAS3417.1.

    • Search Google Scholar
    • Export Citation
  • Kirshbaum, D. J., and J. G. Fairman Jr., 2015: Cloud trails past the Lesser Antilles. Mon. Wea. Rev., 143, 9951017, doi:10.1175/MWR-D-14-00254.1.

    • Search Google Scholar
    • Export Citation
  • Kirshbaum, D. J., G. H. Bryan, R. Rotunno, and D. R. Durran, 2007: The triggering of orographic rainbands by small-scale topography. J. Atmos. Sci., 64, 15301549, doi:10.1175/JAS3924.1.

    • Search Google Scholar
    • Export Citation
  • Knox, J. A., 2015: Dynamical meteorology/inertial instability. Encyclopedia of Atmospheric Sciences, 2nd ed. G. North, J. Pyle, and F. Zang, Eds., Academic Press, 334–342, doi:10.1016/B978-0-12-382225-3.00175-4.

  • Knox, J. A., and B. D. Hoggatt, 1996: Mesoscale dynamics of mid-level convection in an intense mid-latitude anticyclone. Preprints, Seventh Conf. on Mesoscale Processes, Reading, United Kingdom, Amer. Meteor. Soc., 453–455.

  • Lim, K.-S. S., and S.-Y. Hong, 2010: Development of an effective double-moment cloud microphysics scheme with prognostic cloud condensation nuclei (CCN) for weather and climate models. Mon. Wea. Rev., 138, 15871612, doi:10.1175/2009MWR2968.1.

    • Search Google Scholar
    • Export Citation
  • Marconetti, A., and G. Frustaci, 2001: Looking for possible PV banner effects in the Po Valley’s lower layer during MAP-SOP. MAP Newsl., 15, 183186. [Available online at http://www.map.meteoswiss.ch/map-doc/NL15/frustaci.pdf.]

    • Search Google Scholar
    • Export Citation
  • Markowski, P., and Y. Richardson, 2011: Mesoscale Meteorology in Midlatitudes. Vol. 2. John Wiley & Sons, 430 pp.

  • Mayr, G., and Coauthors, 2004: Gap flow measurements during the Mesoscale Alpine Programme. Meteor. Atmos. Phys., 86, 99119, doi:10.1007/s00703-003-0022-2.

    • Search Google Scholar
    • Export Citation
  • Nakanishi, M., and H. Niino, 2004: An improved Mellor–Yamada level-3 model with condensation physics: Its design and verification. Bound.-Layer Meteor., 112, 131, doi:10.1023/B:BOUN.0000020164.04146.98.

    • Search Google Scholar
    • Export Citation
  • Novak, D. R., L. F. Bosart, D. Keyser, and J. S. Waldstreicher, 2004: An observational study of cold season–banded precipitation in northeast U.S. cyclones. Wea. Forecasting, 19, 9931010, doi:10.1175/815.1.

    • Search Google Scholar
    • Export Citation
  • Rotunno, R., and R. Ferretti, 2003: Orographic effects on rainfall in MAP cases IOP 2b and IOP 8. Quart. J. Roy. Meteor. Soc., 129, 373390, doi:10.1256/qj.02.20.

    • Search Google Scholar
    • Export Citation
  • Schär, C., 2002: Mesoscale mountains and the larger-scale atmospheric dynamics: A review. Meteorology at the Millennium, R. P. Pearce, Ed., Vol. 83, Academic Press, 29–42, doi:0.1016/S0074-6142(02)80155-3.

  • Schär, C., and R. B. Smith, 1993: Shallow-water flow past isolated topography. Part II: Transition to vortex shedding. J. Atmos. Sci., 50, 14011412, doi:10.1175/1520-0469(1993)050<1401:SWFPIT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Schär, C., M. Sprenger, D. Lüthi, Q. Jiang, R. B. Smith, and R. Benoit, 2003: Structure and dynamics of an Alpine potential-vorticity banner. Quart. J. Roy. Meteor. Soc., 129, 825855, doi:10.1256/qj.02.47.

    • Search Google Scholar
    • Export Citation
  • Schultz, D. M., and P. N. Schumacher, 1999: The use and misuse of conditional symmetric instability. Mon. Wea. Rev., 127, 27092732, doi:10.1175/1520-0493(1999)127<2709:TUAMOC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Schultz, D. M., and J. A. Knox, 2007: Banded convection caused by frontogenesis in a conditionally, symmetrically, and inertially unstable environment. Mon. Wea. Rev., 135, 20952110, doi:10.1175/MWR3400.1.

    • Search Google Scholar
    • Export Citation
  • Schumacher, R. S., D. M. Schultz, and J. A. Knox, 2010: Convective snowbands downstream of the Rocky Mountains in an environment with conditional, dry symmetric, and inertial instabilities. Mon. Wea. Rev., 138, 44164438, doi:10.1175/2010MWR3334.1.

    • Search Google Scholar
    • Export Citation
  • Schumacher, R. S., D. M. Schultz, and J. A. Knox, 2015: Influence of terrain resolution on banded convection in the lee of the Rocky Mountains. Mon. Wea. Rev., 143, 13991416, doi:10.1175/MWR-D-14-00255.1.

    • Search Google Scholar
    • Export Citation
  • Shen, C. Y., and T. E. Evans, 1998: Inertial instability of large Rossby number horizontal shear flows in a thin homogeneous layer. Dyn. Atmos. Oceans, 26, 185208, doi:10.1016/S0377-0265(98)00042-6.

    • Search Google Scholar
    • Export Citation
  • Skamarock, W. C., 2004: Evaluating mesoscale NWP models using kinetic energy spectra. Mon. Wea. Rev., 132, 30193032, doi:10.1175/MWR2830.1.

    • Search Google Scholar
    • Export Citation
  • Skamarock, W. C., and Coauthors, 2008: A description of the Advanced Research WRF version 3. NCAR. Tech. Note NCAR/TN-475+STR, 113 pp., doi:10.5065/D68S4MVH.

  • Smith, R. B., A. C. Gleason, P. A. Gluhosky, and V. Grubii, 1997: The wake of St. Vincent. J. Atmos. Sci., 54, 606623, doi:10.1175/1520-0469(1997)054<0606:TWOSV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Smith, R. B., Q. Jiang, M. G. Fearon, P. Tabary, M. Dorninger, J. D. Doyle, and R. Benoit, 2003: Orographic precipitation and air mass transformation: An Alpine example. Quart. J. Roy. Meteor. Soc., 129, 433454, doi:10.1256/qj.01.212.

    • Search Google Scholar
    • Export Citation
  • Stevens, D. E., and P. E. Ciesielski, 1986: Inertial instability of horizontally sheared flow away from the equator. J. Atmos. Sci., 43, 28452856, doi:10.1175/1520-0469(1986)043<2845:IIOHSF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wetter, T., and D. Zinkhan, 2014: Tailored weather radar products for use in aviation. Eighth Int. Conf. on Radar in Hydrology and Meteorology (ERAD 2014), Deutscher Wetterdienst (DWD), Garmisch-Partenkirchen, Germany, APP.P01. [Available online at http://www.pa.op.dlr.de/erad2014/programme/Presentations/APP.P01_Wetter.pdf.]

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