Editorial Type:
Article
Article Type:
Research Article

Observations of Nonclassical Frontal Propagation and Frontally Forced Gravity Waves Adjacent to Steep Topography

Paul J. Neiman NOAA/Environmental Technology Laboratory, Boulder, Colorado

Search for other papers by Paul J. Neiman in
Current site
Google Scholar
PubMed Close
,
F. Martin Ralph NOAA/Environmental Technology Laboratory, Boulder, Colorado

Search for other papers by F. Martin Ralph in
Current site
Google Scholar
PubMed Close
,
Robert L. Weber NOAA/Environmental Technology Laboratory, Boulder, Colorado

Search for other papers by Robert L. Weber in
Current site
Google Scholar
PubMed Close
,
Taneil Uttal NOAA/Environmental Technology Laboratory, Boulder, Colorado

Search for other papers by Taneil Uttal in
Current site
Google Scholar
PubMed Close
,
Louisa B. Nance Cooperative Institute for Research in Environmental Sciences and NOAA/ETL, Boulder, Colorado

Search for other papers by Louisa B. Nance in
Current site
Google Scholar
PubMed Close
, and
David H. Levinson United States Department of the Interior—BLM, Missoula, Montana

Search for other papers by David H. Levinson in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Nov 2001
DOI:
https://doi.org/10.1175/1520-0493(2001)129<2633:OONFPA>2.0.CO;2
Page(s):
2633–2659
Restricted access

We are aware of a technical issue preventing figures and tables from showing in some newly published articles in the full-text HTML view.
While we are resolving the problem, please use the online PDF version of these articles to view figures and tables.

Abstract

Through the integrated analysis of remote sensing and in situ data taken along the Front Range of Colorado, this study describes the interactions that occurred between a leeside arctic front and topographically modulated flows. These interactions resulted in nonclassical frontal behavior and structure across northeastern Colorado. The shallow arctic front initially advanced southwestward toward the Front Range foothills, before retreating eastward. Then, a secondary surge of arctic air migrated westward into the foothills. During its initial southwestward advance, the front exhibited obstacle-like, density-current characteristics. Its initial advance was interrupted by strong downslope northwesterly flow associated with a high-amplitude mountain wave downstream of the Continental Divide, and by a temporal decrease in the density contrast across the front due to diurnal heating in the cold air and weak cold advection in the warm air. The direction and depth of flow within the arctic air also influenced the frontal propagation.

The shallow, obstacle-like front actively generated both vertically propagating and vertically trapped gravity waves as it advanced into the downslope northwesterly flow, resulting in midtropospheric lenticular wave clouds aloft that tracked with the front. Because the front entered a region where strong downslope winds and mountain waves extended downstream over the high plains, the wave field in northeastern Colorado included both frontally forced and true mountain-forced gravity waves. A sequence of Scorer parameter profiles calculated from hourly observations reveals a sharp contrast between the prefrontal and postfrontal wave environments. Consequently, analytic resonant wave mode calculations based on the Scorer parameter profiles reveal that the waves supported in the postfrontal regime differed markedly from those supported in the prefrontal environment. This result is consistent with wind profiler observations that showed the amplitude of vertical motions decreasing substantially through 16 km above mean sea level (MSL) after the shallow frontal passage.

Corresponding author address: Paul J. Neiman, NOAA/Environmental Technology Laboratory, Mail Code R/E/ET7, 325 Broadway, Boulder, CO 80303. Email: Paul.J.Neiman@noaa.gov

Abstract

Through the integrated analysis of remote sensing and in situ data taken along the Front Range of Colorado, this study describes the interactions that occurred between a leeside arctic front and topographically modulated flows. These interactions resulted in nonclassical frontal behavior and structure across northeastern Colorado. The shallow arctic front initially advanced southwestward toward the Front Range foothills, before retreating eastward. Then, a secondary surge of arctic air migrated westward into the foothills. During its initial southwestward advance, the front exhibited obstacle-like, density-current characteristics. Its initial advance was interrupted by strong downslope northwesterly flow associated with a high-amplitude mountain wave downstream of the Continental Divide, and by a temporal decrease in the density contrast across the front due to diurnal heating in the cold air and weak cold advection in the warm air. The direction and depth of flow within the arctic air also influenced the frontal propagation.

The shallow, obstacle-like front actively generated both vertically propagating and vertically trapped gravity waves as it advanced into the downslope northwesterly flow, resulting in midtropospheric lenticular wave clouds aloft that tracked with the front. Because the front entered a region where strong downslope winds and mountain waves extended downstream over the high plains, the wave field in northeastern Colorado included both frontally forced and true mountain-forced gravity waves. A sequence of Scorer parameter profiles calculated from hourly observations reveals a sharp contrast between the prefrontal and postfrontal wave environments. Consequently, analytic resonant wave mode calculations based on the Scorer parameter profiles reveal that the waves supported in the postfrontal regime differed markedly from those supported in the prefrontal environment. This result is consistent with wind profiler observations that showed the amplitude of vertical motions decreasing substantially through 16 km above mean sea level (MSL) after the shallow frontal passage.

Corresponding author address: Paul J. Neiman, NOAA/Environmental Technology Laboratory, Mail Code R/E/ET7, 325 Broadway, Boulder, CO 80303. Email: Paul.J.Neiman@noaa.gov

Save
Cover Monthly Weather Review
Monthly Weather Review

  • Adams, M. E., S. Businger, and M. L. Kaplan, 1995: Terrain-induced midtropospheric frontogenesis and jet streak formation during STORM-FEST IOP-17. Preprints, Seventh Conf. on Mountain Meteorology, Breckenridge, CO, Amer. Meteor. Soc., 96–100.

    • Search Google Scholar
    • Export Citation

  • Bernard, A., D. Demaiffe, N. Mattielli, and R. S. Punongbayan, 1991:: Anhydrite-bearing pumices from Mount Pinatubo: Further evidence for the existence of sulphur-rich silicic magmas. Nature, 354 , 139–140.

    • Search Google Scholar
    • Export Citation

  • Bluestein, H. B., 1993: Observations and Theory of Weather Systems. Vol. II, Synoptic-Dynamic Meteorology in Midlatitudes, Oxford University Press, 594 pp.

    • Search Google Scholar
    • Export Citation

  • Caccia, J-L., M. Crochet, and K. Saada, 1997: ST radar evaluation of the standard deviation of the air vertical velocity perturbed by the local orography. J. Atmos. Solar-Terr. Phys, 59 , 1127–1131.

    • Search Google Scholar
    • Export Citation

  • Carbone, R. E., 1982: A severe frontal rainband. Part I: Stormwide hydrodynamic structure. J. Atmos. Sci, 39 , 258–279.

  • Clark, T. L., W. D. Hall, and R. M. Banta, 1994: Two- and three-dimensional simulations of the 9 January 1989 severe Boulder windstorm: Comparison with observations. J. Atmos. Sci, 51 , 2317–2343.

    • Search Google Scholar
    • Export Citation

  • Colle, B. A., and C. F. Mass, 1995: The structure and evolution of cold surges east of the Rocky Mountains. Mon. Wea. Rev, 123 , 2577–2610.

    • Search Google Scholar
    • Export Citation

  • Crook, N. A., 1988: Trapping of low-level internal gravity waves. J. Atmos. Sci, 45 , 1533–1541.

  • Darby, L. S., W. D. Neff, and R. M. Banta, 1999: Multiscale analysis of a meso-β frontal passage in the complex terrain of the Colorado Front Range. Mon. Wea. Rev, 127 , 2062–2081.

    • Search Google Scholar
    • Export Citation

  • Davis, C. A., 1997: Mesoscale anticyclonic circulations in the lee of the central Rocky Mountains. Mon. Wea. Rev, 125 , 2838–2855.

    • Search Google Scholar
    • Export Citation

  • Durran, D. R., 1986a: Mountain waves. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 472–492.

  • Durran, D. R., 1986b: 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 , 2527–2543.

    • Search Google Scholar
    • Export Citation

  • Durran, D. R., 1990: Mountain waves and downslope winds. Atmospheric Processes over Complex Terrain, Meteor. Monogr., No. 45, Amer. Meteor. Soc., 59–81.

    • Search Google Scholar
    • Export Citation

  • Fulton, R., D. S. Zrnić, and R. J. Doviak, 1990: Initiation of a solitary wave family in the demise of a nocturnal thunderstorm density current. J. Atmos. Sci, 47 , 319–337.

    • Search Google Scholar
    • Export Citation

  • Fritts, D. C., and G. D. Nastrom, 1992: Sources of mesoscale variability of gravity waves. Part II: Frontal, convective, and jet stream excitation. J. Atmos. Sci, 49 , 111–127.

    • Search Google Scholar
    • Export Citation

  • Hartjenstein, G., and R. Bleck, 1991: Factors affecting cold-air outbreaks east of the Rocky Mountains. Mon. Wea. Rev, 119 , 2280–2292.

    • Search Google Scholar
    • Export Citation

  • Hogg, D. C., and and Coauthors, 1983: An automated profiler of temperature, wind, and humidity in the troposphere. J. Climate Appl. Meteor, 22 , 807–831.

    • Search Google Scholar
    • Export Citation

  • Jin, Y., S. E. Koch, Y-L. Lin, F. M. Ralph, and C. Chen, 1996: Numerical simulations of an observed gravity current and gravity waves in an environment characterized by complex stratification and shear. J. Atmos. Sci, 53 , 3570–3588.

    • Search Google Scholar
    • Export Citation

  • Keller, T. L., 1994: Implications of the hydrostatic assumption on atmospheric gravity waves. J. Atmos. Sci, 51 , 1915–1929.

  • Koch, S. E., 1984: The role of an apparent mesoscale frontogenetical circulation in squall line initiation. Mon. Wea. Rev, 112 , 2090–2111.

    • Search Google Scholar
    • Export Citation

  • Kropfli, R. A., and and Coauthors, 1995: Cloud physics studies with 8 mm wavelength radar. Atmos. Res, 35 , 299–313.

  • Kuettner, J. P., P. A. Hildebrand, and T. L. Clark, 1987: Convection waves: Observations of gravity wave systems over convectively active boundary layers. Quart. J. Roy. Meteor. Soc, 113 , 445–467.

    • Search Google Scholar
    • Export Citation

  • Lee, T. J., R. A. Pielke, R. C. Kessler, and J. Weaver, 1989: Influence of cold pools downstream of mountain barriers on downslope winds and flushing. Mon. Wea. Rev, 117 , 2041–2058.

    • Search Google Scholar
    • Export Citation

  • Lilly, D. K., and E. J. Zipser, 1972: The Front Range windstorm of 11 January 1972—A meteorological narrative. Weatherwise, 25 , 56–63.

    • Search Google Scholar
    • Export Citation

  • Martner, B. E., and J. D. Marwitz, 1982: Wind characteristics in southern Wyoming. J. Appl. Meteor, 21 , 1815–1827.

  • Marwitz, J. D., and P. J. Dawson, 1984: Low-level airflow in southern Wyoming during wintertime. Mon. Wea. Rev, 112 , 1246–1262.

  • May, P. T., K. P. Moran, and R. G. Strauch, 1989: The accuracy of RASS temperature profiles. J. Appl. Meteor, 28 , 1329–1335.

  • Mecikalski, J. R., and J. S. Tilley, 1992: Cold surges along the Front Range of the Rocky Mountains: Development of a classification scheme. Meteor. Atmos. Phys, 48 , 249–271.

    • Search Google Scholar
    • Export Citation

  • Nance, L. B., 1997: On the inclusion of compressibility effects in the Scorer parameter. J. Atmos. Sci, 54 , 362–367.

  • Nance, L. B., and D. R. Durran, 1997: A modeling study of nonstationary trapped mountain lee waves. Part I: Mean-flow variability. J. Atmos. Sci, 54 , 2275–2291.

    • Search Google Scholar
    • Export Citation

  • Nastrom, G. D., M. R. Peterson, J. L. Green, K. S. Gage, and T. E. VanZandt, 1990: Sources of gravity wave activity seen in the vertical velocities observed by the Flatland VHF radar. J. Appl. Meteor, 29 , 783–792.

    • Search Google Scholar
    • Export Citation

  • Neiman, P. J., R. M. Hardesty, M. A. Shapiro, and R. E. Cupp, 1988:: Doppler lidar observations of a downslope windstorm. Mon. Wea. Rev, 116 , 2265–2275.

    • Search Google Scholar
    • Export Citation

  • Neiman, P. J., P. T. May, B. B. Stankov, and M. A. Shapiro, 1991: Radio acoustic sounding system observations of an arctic front. J. Appl. Meteor, 30 , 881–892.

    • Search Google Scholar
    • Export Citation

  • Neiman, P. J., P. T. May, and M. A. Shapiro, 1992: Radio acoustic sounding system (RASS) and wind profiler observations of lower- and middle-tropospheric weather systems. Mon. Wea. Rev, 120 , 2298–2313.

    • Search Google Scholar
    • Export Citation

  • Politovich, M. K., and B. C. Bernstein, 1995: Production and depletion of supercooled liquid water in a Colorado winter storm. J. Appl. Meteor, 34 , 2631–2648.

    • Search Google Scholar
    • Export Citation

  • Post, M. J., and R. E. Cupp, 1990: Optimizing a pulsed Doppler lidar. Appl. Opt, 29 , 4145–4158.

  • Post, M. J., A. Weickmann, K. R. Healy, R. J. Willis, and C. Grund, 1996:: Comparison of Mount Pinatubo and El Chichon volcanic events: Lidar observations at 10.6 and 0.69 μm. J. Geophys. Res, 101 , 3929–3940.

    • Search Google Scholar
    • Export Citation

  • Pratte, J. F., and L. Kaimal, 1986: Surface mesonetwork operator's manual. 2d version. 121 pp. [Available from NOAA/ERL/Forecast Systems Laboratory, Boulder, CO 80303.].

    • Search Google Scholar
    • Export Citation

  • Queney, P., 1948: The problem of airflow over mountains: A summary of theoretical studies. Bull. Amer. Meteor. Soc, 29 , 16–26.

  • Ralph, F. M., M. Crochet, and S. V. Venkateswaran, 1992: A study of mountain lee waves using clear-air radar. Quart. J. Roy. Meteor. Soc, 118 , 597–627.

    • Search Google Scholar
    • Export Citation

  • Ralph, F. M., C. Mazaudier, M. Crochet, and S. V. Venkateswaran, 1993: Doppler sodar and radar wind-profiler observations of gravity-wave activity associated with a gravity current. Mon. Wea. Rev, 121 , 444–463.

    • Search Google Scholar
    • Export Citation

  • Ralph, F. M., P. J. Neiman, D. W. van de Kamp, and D. C. Law, 1995: Using spectral moment data from NOAA's 404-MHz radar wind profilers to observe precipitation. Bull. Amer. Meteor. Soc, 76 , 1717–1739.

    • Search Google Scholar
    • Export Citation

  • Ralph, F. M., P. J. Neiman, and T. L. Keller, 1999: Deep-tropospheric gravity waves created by leeside cold fronts. J. Atmos. Sci, 56 , 2986–3009.

    • Search Google Scholar
    • Export Citation

  • Rasmussen, R. M., and and Coauthors, 1992: The Winter Icing and Storms Project (WISP). Bull. Amer. Meteor. Soc, 73 , 951–974.

  • Rasmussen, R. M., B. C. Bernstein, M. Murakami, G. Stossmeister, and J. Reisner, 1995: The 1990 Valentine's Day arctic outbreak. Part I: Mesoscale and microscale structure and evolution of a Colorado Front Range shallow upslope cloud. J. Appl. Meteor, 34 , 1481–1511.

    • Search Google Scholar
    • Export Citation

  • Schaefer, J. T., 1986: The dryline. Mesoscale Meteorology and Forecasting, P. Ray, Ed., Amer. Meteor. Soc., 549–570.

  • Schubert, W. H., S. K. Cox, P. E. Ciesielski, and C. M. Johnson-Pasqua, 1987: Operation of a ceilometer during the FIRE marine stratocumulus experiment. Atmospheric Science Paper 420, Colorado State University.

    • Search Google Scholar
    • Export Citation

  • Scorer, R. S., 1949: Theory of lee waves of mountains. Quart. J. Roy. Meteor. Soc, 75 , 41–56.

  • Shapiro, M. A., 1984: Meteorological tower measurements of a surface cold front. Mon. Wea. Rev, 112 , 1634–1639.

  • Shapiro, M. A., and D. Keyser, 1990: Fronts, jet streams, and the tropopause. Extratropical Cyclones: The Erik Palmén Memorial Volume, C. W. Newton and E. Holopainen, Eds., Amer. Meteor. Soc., 167–191.

    • Search Google Scholar
    • Export Citation

  • Shapiro, M. A., T. Hampel, D. Rotzoll, and F. Mosher, 1985: The frontal hydraulic head: A micro-α-scale (∼1 km) triggering mechanism for mesoconvective weather systems. Mon. Wea. Rev, 113 , 1166–1183.

    • Search Google Scholar
    • Export Citation

  • Shutts, G. J., and A. Broad, 1993: A case study of lee waves over the Lake District in northern England. Quart. J. Roy. Meteor. Soc, 119 , 377–408.

    • Search Google Scholar
    • Export Citation

  • Simpson, J. E., and R. E. Britter, 1980: A laboratory model of an atmospheric mesofront. Quart. J. Roy. Meteor. Soc, 106 , 485–500.

    • 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.

  • Steenburgh, W. J., and C. F. Mass, 1994: The structure and evolution of a simulated Rocky Mountain lee trough. Mon. Wea. Rev, 122 , 2740–2761.

    • Search Google Scholar
    • Export Citation

  • Tripoli, S., A. Buzzi, and A. Speranza, 1990: Orographic cyclogenesis. Extratropical Cyclones: The Erik Palmén Memorial Volume, C. W. Newton and E. Holopainen, Eds., Amer. Meteor. Soc., 107–127.

    • Search Google Scholar
    • Export Citation

  • Wakimoto, R. M., 1982: The life cycle of thunderstorm gust fronts as viewed with Doppler radar and rawinsonde data. Mon. Wea. Rev, 110 , 1060–1082.

    • Search Google Scholar
    • Export Citation

  • Weber, B. L., D. B. Wuertz, D. C. Law, A. S. Frisch, and J. M. Brown, 1992: Effects of small-scale vertical motion on radar measurements of wind and temperature profiles. J. Atmos. Oceanic Technol, 9 , 193–209.

    • Search Google Scholar
    • Export Citation

  • Wesley, D. A., R. M. Rasmussen, and B. C. Bernstein, 1995: Snowfall associated with a terrain-generated convergence zone during the Winter Icing and Storms Project. Mon. Wea. Rev, 123 , 2957–2977.

    • Search Google Scholar
    • Export Citation

  • Westwater, E. R., and F. O. Guiraud, 1980: Ground-based microwave radiometric retrieval of precipitable water vapor in the presence of clouds with high liquid content. Radio Sci, 15 , 947–957.

    • Search Google Scholar
    • Export Citation

  • Wolfe, D., and and Coauthors, 1995: An overview of the mobile profiler system: Preliminary results from field tests during the Los Angeles free-radical study. Bull. Amer. Meteor. Soc, 76 , 523–534.

    • Search Google Scholar
    • Export Citation

  • Wuertz, D. B., B. L. Weber, R. G. Strauch, A. S. Frisch, C. G. Little, D. A. Merritt, K. P. Moran, and D. C. Welsh, 1988: Effects of precipitation on UHF wind profiler measurements. J. Atmos. Oceanic Technol, 5 , 452–464.

    • Search Google Scholar
    • Export Citation

  • Wurtele, M. G., R. D. Sharman, and T. L. Keller, 1987: Analysis and simulations of a troposphere–stratosphere gravity wave model. Part I. J. Atmos. Sci, 44 , 3269–3281.

    • Search Google Scholar
    • Export Citation

  • Young, G. S., and R. H. Johnson, 1984: Meso- and microscale features of a Colorado cold front. J. Climate Appl. Meteor, 23 , 1315–1325.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 764 537 235
PDF Downloads 91 33 2