Editorial Type:
Article
Article Type:
Research Article

The Influence of Topography and Lower-Tropospheric Winds on Dryline Morphology

Steven E. Peckham Department of Meteorology, Texas A&M University, College Station, Texas

Search for other papers by Steven E. Peckham in
Current site
Google Scholar
PubMed Close
and
Louis J. Wicker Department of Meteorology, Texas A&M University, College Station, Texas

Search for other papers by Louis J. Wicker in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Jul 2000
DOI:
https://doi.org/10.1175/1520-0493(2000)128<2165:TIOTAL>2.0.CO;2
Page(s):
2165–2189
Restricted access

Abstract

The effects of topography, wind shear, and zonal wind speed on dryline formation and evolution are investigated using a three-dimensional nonhydrostatic mesoscale model. Rather than conduct a case study a parameter study was performed to examine factors that control the depth and strength of the dryline circulation.

This study reveals that the potential for convective storm formation is greatest in those environments in which the cross-dryline flow is weak above the dryline location. This results in boundary layer flow nearly parallel to the north–south-oriented dryline boundary. Under these conditions, the subsiding westerly flow and elevated residual layer formation do not strengthen the capping inversion above the eastern convective boundary layer. In addition, moist air parcels from near the surface are able to reside within the dryline updraft resulting in higher midtropospheric relative humidity subsequently increasing the likelihood of convective storm initiation.

As downslope westerly flow strengthens above the dryline subsidence warming increases and the capping inversion east of the boundary lowers. In response to the subsidence pressure falls occur east of the dryline. Consequently, the east–west horizontal pressure gradient weakens reducing the convergence and frontogenetical circulation along the dryline. The depth of the vertical circulation decreases and air parcels resident within the dryline updraft are detrained at lower altitudes.

Corresponding author address: Dr. Steven E. Peckham, Department of Atmospheric Science, University of Illinois at Urbana–Champaign, 105 S Gregory St., Urbana, IL 61801.

Abstract

The effects of topography, wind shear, and zonal wind speed on dryline formation and evolution are investigated using a three-dimensional nonhydrostatic mesoscale model. Rather than conduct a case study a parameter study was performed to examine factors that control the depth and strength of the dryline circulation.

This study reveals that the potential for convective storm formation is greatest in those environments in which the cross-dryline flow is weak above the dryline location. This results in boundary layer flow nearly parallel to the north–south-oriented dryline boundary. Under these conditions, the subsiding westerly flow and elevated residual layer formation do not strengthen the capping inversion above the eastern convective boundary layer. In addition, moist air parcels from near the surface are able to reside within the dryline updraft resulting in higher midtropospheric relative humidity subsequently increasing the likelihood of convective storm initiation.

As downslope westerly flow strengthens above the dryline subsidence warming increases and the capping inversion east of the boundary lowers. In response to the subsidence pressure falls occur east of the dryline. Consequently, the east–west horizontal pressure gradient weakens reducing the convergence and frontogenetical circulation along the dryline. The depth of the vertical circulation decreases and air parcels resident within the dryline updraft are detrained at lower altitudes.

Corresponding author address: Dr. Steven E. Peckham, Department of Atmospheric Science, University of Illinois at Urbana–Champaign, 105 S Gregory St., Urbana, IL 61801.

Save
Cover Monthly Weather Review
Monthly Weather Review

  • Atkins, N. T., R. M. Wakimoto, and C. L. Ziegler, 1998: Observations of the finescale structure of a dryline during VORTEX 95. Mon. Wea. Rev.,127, 525–550.

  • Benjamin, S. G., 1983: Some effects of surface heating and topography on the regional severe storm environment. Ph.D. dissertation, The Pennsylvania State University, State College, PA, 265 pp.

  • ——, and T. N. Carlson, 1986: Some effects of surface heating and topography on the regional severe storm environment. Part I: Three-dimensional simulations. Mon. Wea. Rev.,114, 307–329.

  • Bluestein, H. B., and S. Parker, 1993: Modes of isolated, severe convective-storm formation along the dryline. Mon. Wea. Rev.,121, 1354–1372.

  • ——, and T. M. Crawford, 1997: Mesoscale dynamics of the near-dryline environment: Analysis of data from COPS-91. Mon. Wea. Rev.,125, 2161–2175.

  • Bonner, W. D., 1968: Climatology of the low-level jet. Mon. Wea. Rev.,96, 833–850.

  • Brown, R. A., 1980: Longitudinal instabilities and secondary flows in the planetary boundary layer: A review. Rev. Geophys. Space Phys.,18, 683–697.

  • Carlson, T. N., and F. H. Ludlam, 1968: Conditions for the occurrence of severe local storms. Tellus,20, 203–226.

  • ——, S. G. Benjamin, G. S. Forbes, and Y.-F. Li, 1983: Elevated mixed layers in the regional severe storm environment: Conceptual model and case studies. Mon. Wea. Rev.,111, 1453–1473.

  • Chang, J.-T., and P. J. Wetzel, 1991: Effects of spatial variations of soil moisture and vegetation on the evolution of a prestorm environment: A case study. Mon. Wea. Rev.,119, 1368–1390.

  • Colby, F. P., 1984: Convective inhibition as a predictor of convection during AVE-SESAME II. Mon. Wea. Rev.,112, 2239–2252.

  • Crawford, T. M., and H. B. Bluestein, 1997: Characteristics of dryline passage during COPS-91. Mon. Wea. Rev.,125, 463–477.

  • Deardorff, J. W., 1972: Parameterization of the planetary boundary layer for use in general circulation models. Mon. Wea. Rev.,100, 93–106.

  • ——, 1978: Efficient prediction of ground surface temperature and moisture, with inclusion of a layer of vegetation. J. Geophys. Res.,83, 1889–1903.

  • Doswell, C. A., III, 1982: The operational meteorology of convective weather. Vol. I: Operational mesoanalysis. NOAA Tech. Memo. NWS NSSFC-5, 186 pp.

  • Etling, D., and R. A. Brown, 1993: Roll vortices in the planetary boundary layer: A review. Bound.-Layer Meteor.,65, 215–248.

  • Fankhauser, J. C., 1971: Thunderstorm-environment interactions determined from aircraft and radar observations. Mon. Wea. Rev.,3, 171–192.

  • Fawbush, E. J., and R. C. Miller, 1954: The types of airmasses in which North American tornadoes form. Bull. Amer. Meteor. Soc.,35, 154–165.

  • Fritsch, J. M., R. J. Kane, and C. R. Chelius, 1986: The contribution of mesoscale convective systems to the warm-season precipitation in the United States. J. Climate Appl. Meteor.,25, 1333–1345.

  • Gal-Chen, T., and R. Sommerville, 1975: On the use of a coordinate transformation for the solution of the Navier–Stokes equations. J. Comput. Phys.,17, 209–228.

  • Graziano, T. M., and T. N. Carlson, 1987: A statistical evaluation of lid strength on deep convection. Wea. Forecasting,2, 127–139.

  • Hane, C. E., C. L. Ziegler, and H. B. Bluestein, 1993: Investigation of the dryline and convective storms initiated along the dryline:Field experiments during COPS-91. Bull. Amer. Meteor. Soc.,74, 2133–2145.

  • ——, H. B. Bluestein, T. M. Crawford, M. E. Baldwin, and R. M. Rabin, 1997: Severe thunderstorm development in relation to along-dryline variability: A case study. Mon. Wea. Rev.,125, 231–251.

  • Klemp, J. B., and R. B. Wilhelmson, 1978: The simulation of three-dimensional convective storm dynamics. J. Atmos. Sci.,35, 1070–1096.

  • Lanicci, J. M., T. N. Carlson, and T. T. Warner, 1987: Sensitivity of the Great Plains severe-storm environment to soil-moisture distribution. Mon. Wea. Rev.,115, 2660–2673.

  • Marshall, T. P., 1980: Topographic influences on Amarillo radar echo climatology. M.S. thesis, Texas Tech University, Lubbock, TX, 65 pp.

  • McGuire, E. L., 1962: The vertical structure of three drylines as revealed by aircraft traverses. National Severe Storms Project Rep. 7, 11 pp.

  • Ogura, Y., and Y. Chen, 1977: A life history of an intense mesoscale convective storm in Oklahoma. J. Atmos. Sci.,34, 1458–1476.

  • Peckham, S. E., 1999: The influence of topography and lower tropospheric winds on dryline convective initiation. Ph.D. dissertation, Texas A&M University, College Station, TX, 184 pp.

  • Rhea, J. O., 1966: A study of thunderstorm formation along drylines. J. Appl. Meteor.,5, 58–83.

  • Schaefer, J. T., 1973: The motion and morphology of the dryline. NOAA Tech. Memo. ERL NSSL-66, 81 pp.

  • ——, 1986: The dryline. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 549–572.

  • Segal, M., and R. W. Arritt, 1992: Nonclassical mesoscale circulations caused by surface sensible heat-flux gradients. Bull. Amer. Meteor. Soc.,73, 1593–1604.

  • Shaw, B. L., R. A. Pielke, and C. L. Ziegler, 1997: A three-dimensional numerical simulation of a Great Plains dryline. Mon. Wea. Rev.,125, 1489–1506.

  • Stensrud, D. J., 1993: Elevated residual layers and their influence on surface boundary-layer evolution. J. Atmos. Sci.,50, 2284–2293.

  • Sun, W. Y., and Y. Ogura, 1979: Boundary-layer forcing as a possible trigger to a squall-line formation. J. Atmos. Sci.,36, 235–254.

  • ——, and C.-C. Wu, 1992: Formation and diurnal variation of the dryline. J. Atmos. Sci.,49, 1606–1619.

  • Wicker, L. J., and R. B. Wilhelmson, 1995: Simulation and analysis of tornado development and decay within a three-dimensional supercell thunderstorm. J. Atmos. Sci.,52, 2675–2703.

  • Ziegler, C. L., and C. E. Hane, 1993: An observational study of the dryline. Mon. Wea. Rev.,121, 1134–1151.

  • ——, W. J. Martin, R. A. Pielke, and R. L. Walko, 1995: A modeling study of the dryline. J. Atmos. Sci.,52, 263–285.

  • ——, T. J. Lee, and R. A. Pielke Sr., 1997: Convective initiation at the dryline: A modeling study. Mon. Wea. Rev.,125, 1001–1026.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 926 739 41
PDF Downloads 194 65 4