Mechanisms of the Great Plains Low-Level Jet as Simulated in an AGCM

Xianan Jiang Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey

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Ngar-Cheung Lau NOAA/Geophysical Fluid Dynamics Laboratory, Princeton University, Princeton, New Jersey

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Isaac M. Held NOAA/Geophysical Fluid Dynamics Laboratory, Princeton University, Princeton, New Jersey

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Jeffrey J. Ploshay NOAA/Geophysical Fluid Dynamics Laboratory, Princeton University, Princeton, New Jersey

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Abstract

A model diagnosis has been performed on the nocturnal Great Plains low-level jet (LLJ), which is one of the key elements of the warm season regional climate over North America. The horizontal–vertical structure, diurnal phase, and amplitude of the LLJ are well simulated by an atmospheric general circulation model (AGCM), thus justifying a reevaluation of the physical mechanisms for the formation of the LLJ based on output from this model. A diagnosis of the AGCM data confirms that two planetary boundary layer (PBL) processes, the diurnal oscillation of the pressure gradient force and of vertical diffusion, are of comparable importance in regulating the inertial oscillation of the winds, which leads to the occurrence of maximum LLJ strength during nighttime. These two processes are highlighted in the theories for the LLJ proposed by Holton (1967) and Blackadar (1957). A simple model is constructed in order to study the relative roles of these two mechanisms. This model incorporates the diurnal variation of the pressure gradient force and vertical diffusion coefficients as obtained from the AGCM simulation. The results reveal that the observed diurnal phase and amplitude of the LLJ can be attributed to the combination of these two mechanisms. The LLJ generated by either Holton’s or Blackadar’s mechanism alone is characterized by an unrealistic meridional phase shift and weaker amplitude.

It is also shown that the diurnal phase of the LLJ exhibits vertical variations in the PBL, more clearly at higher latitudes, with the upper PBL wind attaining a southerly peak several hours earlier than the lower PBL. The simple model demonstrates that this phase tilt is due mainly to sequential triggering of the inertial oscillation from upper to lower PBL when surface cooling commences after sunset. At lower latitudes, due to the change of orientation of prevailing mean wind vectors and the longer inertial period, the inertial oscillation in the lower PBL tends to be interrupted by strong vertical mixing in the following day, whereas in the upper PBL, the inertial oscillation can proceed in a low-friction environment for a relatively longer duration. Thus, the vertical phase tilt initiated at sunset is less evident at lower latitudes.

Corresponding author address: Dr. Xianan Jiang, USDOC/NOAA/GFDL, P.O. Box 308, 201 Forrestal Rd., Princeton, NJ 08542. Email: xianan.jiang@noaa.gov

Abstract

A model diagnosis has been performed on the nocturnal Great Plains low-level jet (LLJ), which is one of the key elements of the warm season regional climate over North America. The horizontal–vertical structure, diurnal phase, and amplitude of the LLJ are well simulated by an atmospheric general circulation model (AGCM), thus justifying a reevaluation of the physical mechanisms for the formation of the LLJ based on output from this model. A diagnosis of the AGCM data confirms that two planetary boundary layer (PBL) processes, the diurnal oscillation of the pressure gradient force and of vertical diffusion, are of comparable importance in regulating the inertial oscillation of the winds, which leads to the occurrence of maximum LLJ strength during nighttime. These two processes are highlighted in the theories for the LLJ proposed by Holton (1967) and Blackadar (1957). A simple model is constructed in order to study the relative roles of these two mechanisms. This model incorporates the diurnal variation of the pressure gradient force and vertical diffusion coefficients as obtained from the AGCM simulation. The results reveal that the observed diurnal phase and amplitude of the LLJ can be attributed to the combination of these two mechanisms. The LLJ generated by either Holton’s or Blackadar’s mechanism alone is characterized by an unrealistic meridional phase shift and weaker amplitude.

It is also shown that the diurnal phase of the LLJ exhibits vertical variations in the PBL, more clearly at higher latitudes, with the upper PBL wind attaining a southerly peak several hours earlier than the lower PBL. The simple model demonstrates that this phase tilt is due mainly to sequential triggering of the inertial oscillation from upper to lower PBL when surface cooling commences after sunset. At lower latitudes, due to the change of orientation of prevailing mean wind vectors and the longer inertial period, the inertial oscillation in the lower PBL tends to be interrupted by strong vertical mixing in the following day, whereas in the upper PBL, the inertial oscillation can proceed in a low-friction environment for a relatively longer duration. Thus, the vertical phase tilt initiated at sunset is less evident at lower latitudes.

Corresponding author address: Dr. Xianan Jiang, USDOC/NOAA/GFDL, P.O. Box 308, 201 Forrestal Rd., Princeton, NJ 08542. Email: xianan.jiang@noaa.gov

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  • Astling, E. G., J. Paegle, E. Miller, and C. J. O’Brien, 1985: Boundary layer control of nocturnal convection associated with a synoptic-scale system. Mon. Wea. Rev., 113 , 540552.

    • Search Google Scholar
    • Export Citation
  • Beljaars, A. C. M., 1995: The parameterization of surface-fluxes in large-scale models under free convection. Quart. J. Roy. Meteor. Soc., 121 , 255270.

    • Search Google Scholar
    • Export Citation
  • Benton, G. S., and M. A. Estoque, 1954: Water-vapor transfer over the North American continent. J. Meteor., 11 , 462477.

  • Blackadar, A. K., 1957: Boundary layer wind maxima and their significance for the growth of nocturnal inversions. Bull. Amer. Meteor. Soc., 38 , 283290.

    • Search Google Scholar
    • Export Citation
  • Bleeker, W., and M. J. Andre, 1951: On the diurnal variation of precipitation, particularly over central U.S.A., and its relation to large-scale orographic circulation systems. Quart. J. Roy. Meteor. Soc., 77 , 260271.

    • Search Google Scholar
    • Export Citation
  • Bonner, W. D., 1968: Climatology of the low-level jet. Mon. Wea. Rev., 96 , 833850.

  • Bonner, W. D., and J. Paegle, 1970: Diurnal variations in the boundary layer winds over the south-central United States in summer. Mon. Wea. Rev., 98 , 735744.

    • Search Google Scholar
    • Export Citation
  • Carbone, R. E., J. D. Tuttle, D. A. Ahijevych, and S. B. Trier, 2002: Inferences of predictability associated with warm season precipitation episodes. J. Atmos. Sci., 59 , 20332056.

    • Search Google Scholar
    • Export Citation
  • Fast, J. D., and M. D. McCorcle, 1990: A two-dimensional numerical sensitivity study of the Great Plains low-level jet. Mon. Wea. Rev., 118 , 151163.

    • Search Google Scholar
    • Export Citation
  • Frisch, A. S., B. W. Orr, and B. E. Martner, 1992: Doppler radar observations of the development of a boundary-layer nocturnal jet. Mon. Wea. Rev., 120 , 316.

    • Search Google Scholar
    • Export Citation
  • GFDL Global Atmospheric Model Development Team, 2004: The new GFDL global atmosphere and land model AM2-LM2: Evaluation with prescribed SST simulations. J. Climate, 17 , 46414673.

    • Search Google Scholar
    • Export Citation
  • Helfand, H. M., and S. D. Schubert, 1995: Climatology of the Great Plains low-level jet and its contribution to the continental moisture budget of the United States. J. Climate, 8 , 784806.

    • Search Google Scholar
    • Export Citation
  • Hering, W. S., and T. R. Borden, 1962: Diurnal variations in the summer wind field over the central United States. J. Atmos. Sci., 19 , 8186.

    • Search Google Scholar
    • Export Citation
  • Higgins, R. W., Y. Yao, E. S. Yarosh, J. E. Janowiak, and K. C. Mo, 1997: Influence of the Great Plains low-level jet on the summertime precipitation and moisture transport over the central United States. J. Climate, 10 , 481507.

    • Search Google Scholar
    • Export Citation
  • Hoecker Jr., W. H., 1963: Three southerly low-level jet systems delineated by the Weather Bureau special pibal network of 1961. Mon. Wea. Rev., 91 , 573582.

    • Search Google Scholar
    • Export Citation
  • Hoecker Jr., W. H., 1965: Comparative physical behavior of southerly boundary layer jets. Mon. Wea. Rev., 93 , 133144.

  • Holton, J. R., 1967: The diurnal boundary layer wind oscillation above sloping terrain. Tellus, 19 , 199205.

  • Izumi, Y., and M. L. Barad, 1963: Wind and temperature variations during development of a low-level jet. J. Appl. Meteor., 2 , 668673.

    • Search Google Scholar
    • Export Citation
  • Klein, S. A., X. Jiang, J. Boyle, S. Malyshev, and S. Xie, 2006: Diagnosis of the summertime warm and dry bias over the U.S. Southern Great Plains in the GFDL climate model using a weather forecasting approach. Geophys. Res. Lett., 33 .L18805, doi:10.1029/2006GL027567.

    • Search Google Scholar
    • Export Citation
  • Krishna, K., 1968: A numerical study of the diurnal variation of meteorological parameters in the planetary boundary layer. Part I: Diurnal variations of winds. Mon. Wea. Rev., 96 , 269276.

    • Search Google Scholar
    • Export Citation
  • Lee, M-I., and Coauthors, 2007: An analysis of the warm season diurnal cycle over the continental United States and northern Mexico in general circulation models. J. Hydrometeor., in press.

    • Search Google Scholar
    • Export Citation
  • Lock, A. P., 1998: The parameterization of entrainment in cloudy boundary layers. Quart. J. Roy. Meteor. Soc., 124 , 27292753.

  • Lock, A. P., A. R. Brown, M. R. Bush, G. M. Martin, and R. N. B. Smith, 2000: A new boundary layer mixing scheme. Part I: Scheme description and single-column model tests. Mon. Wea. Rev., 128 , 31873199.

    • Search Google Scholar
    • Export Citation
  • Louis, J-F., 1979: A parameteric model of vertical eddy fluxes in the atmosphere. Bound.-Layer Meteor., 17 , 187202.

  • Maddox, R. A., 1980: Mesoscale convection complexes. Bull. Amer. Meteor. Soc., 61 , 13741387.

  • McCorcle, M. D., 1988: Simulation of surface-moisture effects on the Great Plains low-level jet. Mon. Wea. Rev., 116 , 17051720.

  • McNider, R. T., and R. A. Pielke, 1981: Diurnal boundary-layer development over sloping terrain. J. Atmos. Sci., 38 , 21982212.

  • Means, L. L., 1952: On thunderstorm forecasting in the central United States. Mon. Wea. Rev., 80 , 165189.

  • Means, L. L., 1954: A study of the mean southerly wind—Maximum in low levels associated with a period of summer precipitation in the Middle West. Bull. Amer. Meteor. Soc., 35 , 166170.

    • Search Google Scholar
    • Export Citation
  • Mesinger, F., and Coauthors, 2006: North American Regional Reanalysis. Bull. Amer. Meteor. Soc., 87 , 343360.

  • Mitchell, M. J., and R. A. Arritt, 1995: An hourly climatology of the summertime Great Plains low-level jet using wind profiler observations. Wea. Forecasting, 10 , 576591.

    • Search Google Scholar
    • Export Citation
  • Moorthi, S., and M. J. Suarez, 1992: Relaxed Arakawa–Schubert: A parameterization of moist convection for general circulation models. Mon. Wea. Rev., 120 , 9781002.

    • Search Google Scholar
    • Export Citation
  • Paegle, J., and D. W. McLawhorn, 1983: Numerical modeling of diurnal convergence oscillations above sloping terrain. Mon. Wea. Rev., 111 , 6785.

    • Search Google Scholar
    • Export Citation
  • Parish, T. R., A. R. Rodi, and R. D. Clark, 1988: A case study of the summertime Great Plains low level jet. Mon. Wea. Rev., 116 , 94105.

    • Search Google Scholar
    • Export Citation
  • Pitchford, K. L., and J. London, 1962: The low-level jet as related to nocturnal thunderstorms over Midwest United States. J. Appl. Meteor., 1 , 4347.

    • Search Google Scholar
    • Export Citation
  • Rasmusson, E. M., 1967: Atmospheric water vapor transport and the water balance of North America. Part I: Characteristics of the water vapor flux field. Mon. Wea. Rev., 95 , 403426.

    • Search Google Scholar
    • Export Citation
  • Rasmusson, E. M., 1968: Atmospheric water vapor transport and the water balance of North America. Part II: Large-scale water balance investigations. Mon. Wea. Rev., 96 , 720734.

    • Search Google Scholar
    • Export Citation
  • Ting, M., and H. Wang, 2006: The role of the North American topography on the maintenance of the Great Plains summer low-level jet. J. Atmos. Sci., 63 , 10561068.

    • Search Google Scholar
    • Export Citation
  • Uccellini, L. W., and D. R. Johnson, 1979: The coupling of upper and lower tropospheric jet streams and implications for the development of severe convective storms. Mon. Wea. Rev., 107 , 682703.

    • Search Google Scholar
    • Export Citation
  • Wallace, J. M., 1975: Diurnal variations in precipitation and thunderstorm frequency over the conterminous United States. Mon. Wea. Rev., 103 , 406419.

    • Search Google Scholar
    • Export Citation
  • Wexler, H., 1961: A boundary layer interpretation of the low level jet. Tellus, 13 , 368378.

  • Zhong, S., J. D. Fast, and X. Bian, 1996: A case study of the Great Plains low-level jet using wind profiler network data and a high-resolution mesoscale model. Mon. Wea. Rev., 124 , 785806.

    • Search Google Scholar
    • Export Citation
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