On the Orographically Generated Low-Level Easterly Jet and Severe Downslope Storms of March 2006 over the Tacheng Basin of Northwest China

Guangxing Zhang Institute of Desert Meteorology, China Meteorological Administration, and Institute of Central-Asian Weather, Urumqi, Xinjiang, China

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Da-Lin Zhang State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing, China, and
Department of Atmospheric and Oceanic Science, University of Maryland, College Park, College Park, Maryland

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Shufang Sun Urumqi Meteorological Bureau, Urumqi, Xinjiang, China

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Abstract

A high-latitude low-level easterly jet (LLEJ) and downslope winds, causing severe dust storms over the Tacheng basin of northwestern China in March 2006 when the dust source regions were previously covered by snow with frozen soil, are studied in order to understand the associated meteorological conditions and the impact of complex topography on the generation of the LLEJ. Observational analyses show the development of a large-scale, geostrophically balanced, easterly flow associated with a northeastern high pressure and a southeastern low pressure system, accompanied by a westward-moving cold front with an intense inversion layer near the altitudes of mountain ridges. A high-resolution model simulation shows the generation of an LLEJ of near-typhoon strength, which peaked at about 500 m above the ground, as well as downslope windstorms with marked wave breakings and subsidence warming in the leeside surface layer, as the large-scale cold easterly flow moves through a constricting saddle pass and across a higher mountain ridge followed by a lower parallel ridge, respectively. The two different airstreams are merged to form an intense LLEJ of cold air, driven mostly by zonal pressure gradient force, and then the LLEJ moves along a zonally oriented mountain range to the north. Results indicate the importance of the lower ridge in enhancing the downslope winds associated with the higher ridge and the importance of the saddle pass in generating the LLEJ. We conclude that the intense downslope winds account for melting snow, warming and drying soils, and raising dust into the air that is then transported by the LLEJ, generated mostly through the saddle pass, into the far west of the basin.

© 2018 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Guangxing Zhang, zhanggx@idm.cn

Abstract

A high-latitude low-level easterly jet (LLEJ) and downslope winds, causing severe dust storms over the Tacheng basin of northwestern China in March 2006 when the dust source regions were previously covered by snow with frozen soil, are studied in order to understand the associated meteorological conditions and the impact of complex topography on the generation of the LLEJ. Observational analyses show the development of a large-scale, geostrophically balanced, easterly flow associated with a northeastern high pressure and a southeastern low pressure system, accompanied by a westward-moving cold front with an intense inversion layer near the altitudes of mountain ridges. A high-resolution model simulation shows the generation of an LLEJ of near-typhoon strength, which peaked at about 500 m above the ground, as well as downslope windstorms with marked wave breakings and subsidence warming in the leeside surface layer, as the large-scale cold easterly flow moves through a constricting saddle pass and across a higher mountain ridge followed by a lower parallel ridge, respectively. The two different airstreams are merged to form an intense LLEJ of cold air, driven mostly by zonal pressure gradient force, and then the LLEJ moves along a zonally oriented mountain range to the north. Results indicate the importance of the lower ridge in enhancing the downslope winds associated with the higher ridge and the importance of the saddle pass in generating the LLEJ. We conclude that the intense downslope winds account for melting snow, warming and drying soils, and raising dust into the air that is then transported by the LLEJ, generated mostly through the saddle pass, into the far west of the basin.

© 2018 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Guangxing Zhang, zhanggx@idm.cn
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  • Belušić, D., M. Hrastinski, Z. Večenaj, and B. Grisogono, 2013: Wind regimes associated with a mountain gap at the northeastern Adriatic coast. J. Appl. Meteor. Climatol., 52, 20892105, https://doi.org/10.1175/JAMC-D-12-0306.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bougeault, P., and Coauthors, 1993: The atmospheric momentum budget over a major mountain range: First results of the PYREX field program. Ann. Geophys., 11, 395418.

    • Search Google Scholar
    • Export Citation
  • Bougeault, P., and Coauthors, 2001: The MAP special observing period. Bull. Amer. Meteor. Soc., 82, 433462, https://doi.org/10.1175/1520-0477(2001)082<0433:TMSOP>2.3.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brinkmann, W. A. R., 1974: Strong downslope winds at Boulder, Colorado. Mon. Wea. Rev., 102, 592602, https://doi.org/10.1175/1520-0493(1974)102<0592:SDWABC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cameron, D. C., 1931: Easterly gales in the Columbia River gorge during the winter of 1930–1931—Some of their causes and effects. Mon. Wea. Rev., 59, 411413, https://doi.org/10.1175/1520-0493(1931)59<411:EGITCR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Clark, T. L., and W. R. Peltier, 1984: Critical level reflection and the resonant growth on nonlinear mountain waves. J. Atmos. Sci., 41, 31223134, https://doi.org/10.1175/1520-0469(1984)041<3122:CLRATR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Colle, B. A., and C. F. Mass, 2000: High-resolution observations and numerical simulations of easterly gap flow through the Strait of Juan de Fuca on 9–10 December 1995. Mon. Wea. Rev., 128, 23982422, https://doi.org/10.1175/1520-0493(2000)128<2398:HROANS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Colman, B. R., and C. F. Dierking, 1992: The Taku wind of southeast Alaska: Its identification and prediction. Wea. Forecasting, 7, 4964, https://doi.org/10.1175/1520-0434(1992)007<0049:TTWOSA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dudhia, J., 1989: Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model. J. Atmos. Sci., 46, 30773107, https://doi.org/10.1175/1520-0469(1989)046<3077:NSOCOD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Durran, D. R., 1986: Another look at downslope windstorms. Part I: The development of analogs to supercritical flow in an infinitely deep, continuously stratified fluid. J. Atmos. Sci., 43, 25272543, https://doi.org/10.1175/1520-0469(1986)043<2527:ALADWP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Durran, D. R., 1990: Mountain waves and downslope winds. Atmospheric Processes over Complex Terrain, Meteor. Monogr., No. 23, Amer. Meteor. Soc., 59–81.

    • Crossref
    • Export Citation
  • Durran, D. R., 2003: Downslope winds. Encyclopedia of the Atmospheric Sciences, J. Holton, J. Curry, and J. Pyle, Eds., Academic Press, 644–650.

    • Crossref
    • Export Citation
  • Gohm, A., G. J. Mayr, A. Fix, and A. Giez, 2008: On the onset of bora and the formation of rotors and jumps near a mountain gap. Quart. J. Roy. Meteor. Soc., 134, 2146, https://doi.org/10.1002/qj.206.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grubišić, V., and Coauthors, 2008: The Terrain-Induced Rotor Experiment: A field campaign overview including observational highlights. Bull. Amer. Meteor. Soc., 89, 15131534, https://doi.org/10.1175/2008BAMS2487.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hong, S. Y., and J. O. Lim, 2006: The WRF single-moment 6-class microphysics scheme (WSM6). J. Korean Meteor. Soc., 42, 129151.

  • Hong, S. Y., Y. Noh, and J. Dudhia, 2006: A new vertical diffusion package with an explicit treatment of entrainment processes. Mon. Wea. Rev., 134, 23182341, https://doi.org/10.1175/MWR3199.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jackson, P. L., and D. G. Steyn, 1994: Gap winds in a fjord. Part I: Observations and numerical simulation. Mon. Wea. Rev., 122, 26452665, https://doi.org/10.1175/1520-0493(1994)122<2645:GWIAFP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jiang, Q., and J. D. Doyle, 2004: Gravity wave breaking over the central Alps: Role of complex terrain. J. Atmos. Sci., 61, 22492266, https://doi.org/10.1175/1520-0469(2004)061<2249:GWBOTC>2.0.CO;2.

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., and D. K. Lilly, 1978: Numerical simulation of hydrostatic mountain waves. J. Atmos. Sci., 35, 78107, https://doi.org/10.1175/1520-0469(1978)035<0078:NSOHMW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lackmann, G. M., and J. E. Overland, 1989: Atmospheric structure and momentum balance during a gap-wind event in Shelikof Strait, Alaska. Mon. Wea. Rev., 117, 18171833, https://doi.org/10.1175/1520-0493(1989)117<1817:ASAMBD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lehner, M., and Coauthors, 2016: The METCRAX II field experiment: A study of downslope windstorm-type flows in Arizona’s Meteor Crater. Bull. Amer. Meteor. Soc., 97, 217235, https://doi.org/10.1175/BAMS-D-14-00238.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lilly, D. K., 1978: A severe downslope windstorm and aircraft turbulence event induced by a mountain wave. J. Atmos. Sci., 35, 5977, https://doi.org/10.1175/1520-0469(1978)035<0059:ASDWAA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lilly, D. K., and J. B. Klemp, 1979: The effects of terrain shape on nonlinear hydrostatic mountain waves. J. Fluid Mech., 95, 241261, https://doi.org/10.1017/S0022112079001452.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lin, Y.-L., 2007: Mesoscale Dynamics. Cambridge University Press, 630 pp.

    • Crossref
    • Export Citation
  • Liu, M., D. L. Westphal, A. L. Walker, T. R. Holt, K. A. Richardson, and S. D. Miller, 2007: COAMPS real-time dust storm forecasting during Operation Iraqi Freedom. Wea. Forecasting, 22, 192206, https://doi.org/10.1175/WAF971.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Long, R. R., 1954: Some aspects of the flow of stratified fluids: II. Experiments with a two-fluid system. Tellus, 6A, 97115, https://doi.org/10.1111/j.2153-3490.1954.tb01100.x.

    • Search Google Scholar
    • Export Citation
  • Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J. Iacono, and S. A. Clough, 1997: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102, 16 66316 682, https://doi.org/10.1029/97JD00237.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mobbs, S. D., and Coauthors, 2005: Observations of downslope winds and rotors in the Falkland Islands. Quart. J. Roy. Meteor. Soc., 131, 329351, https://doi.org/10.1256/qj.04.51.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Reed, T. R., 1931: Gap winds of the Strait of Juan de Fuca. Mon. Wea. Rev., 59, 373376, https://doi.org/10.1175/1520-0493(1931)59<373:GWOTSO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sharp, J., and C. F. Mass, 2004: Columbia Gorge gap winds: Their climatological influence and synoptic evolution. Wea. Forecasting, 19, 970992, https://doi.org/10.1175/826.1.

    • Crossref
    • 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, https://doi.org/10.5065/D68S4MVH.

    • Crossref
    • Export Citation
  • Smith, C. M., and E. D. Skyllingstad, 2011: Effects of inversion height and surface heat flux on downslope windstorms. Mon. Wea. Rev., 139, 37503764, https://doi.org/10.1175/2011MWR3619.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Smith, R. B., 1977: The steepening of hydrostatic mountain waves. J. Atmos. Sci., 34, 16341654, https://doi.org/10.1175/1520-0469(1977)034<1634:TSOHMW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Smith, R. B., 1985: On severe downslope winds. J. Atmos. Sci., 42, 25972603, https://doi.org/10.1175/1520-0469(1985)042<2597:OSDW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Steenburgh, W. J., D. M. Schultz, and B. A. Colle, 1998: The structure and evolution of gap outflow over the Gulf of Tehuantepec, Mexico. Mon. Wea. Rev., 126, 26732691, https://doi.org/10.1175/1520-0493(1998)126<2673:TSAEOG>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vosper, S. B., 2004: Inversion effects on mountain lee waves. Quart. J. Roy. Meteor. Soc., 130, 17231748, https://doi.org/10.1256/qj.03.63.

  • Whiteman, C. D., 2000: Mountain Meteorology: Fundamentals and Applications. Oxford University Press, 355 pp.

    • Crossref
    • Export Citation
  • Zhang, D., and R. A. Anthes, 1982: A high-resolution model of the planetary boundary layer—Sensitivity tests and comparisons with SESAME-79 data. J. Appl. Meteor., 21, 15941609, https://doi.org/10.1175/1520-0450(1982)021<1594:AHRMOT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhu, H., and H. S. Zhang, 2010: An estimation of the threshold friction velocities over the three different dust storm source areas in northwest China (in Chinese). Acta Meteor. Sin., 68, 977984.

    • Search Google Scholar
    • Export Citation
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