Numerical Study of the Diurnal Cycle along the Central Oregon Coast during Summertime Northerly Flow

S. Bielli College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by S. Bielli in
Current site
Google Scholar
PubMed
Close
,
P. Barbour College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by P. Barbour in
Current site
Google Scholar
PubMed
Close
,
R. Samelson College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by R. Samelson in
Current site
Google Scholar
PubMed
Close
,
E. Skyllingstad College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by E. Skyllingstad in
Current site
Google Scholar
PubMed
Close
, and
J. Wilczak College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by J. Wilczak in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

A triply nested mesoscale atmospheric numerical model is used to study the dynamics of the diurnal cycle of the summertime lower atmosphere along the central Oregon coast. Simulations of four consecutive days in September 1998, during which the winds were strong and northerly, are analyzed. Comparisons with profiler observations suggest that the model performed well enough to provide a useful estimate of the diurnal circulation. During the four days of interest, the low-level wind pattern has a broad maximum between Cape Blanco and Cape Mendocino, with a large north–south gradient along the Oregon coast. The low-level jet undergoes diurnal horizontal and vertical displacements, which partially resemble previous observational and modeling results along the California coast. In both the model and the profiler data, there is a minimum in northerly wind between 1500 and 1800 UTC (0700 and 1000 local time), and a double maximum in offshore flow above the marine boundary layer, with peaks near 0700 and 1600 UTC. At the jet core height, the advection of alongshore momentum is an important component of the alongshore force balance. After 2100 UTC, this advection is the main term balancing the pressure gradient force. Thus, in contrast to the previous results for the California coast, the diurnal circulation is fundamentally three-dimensional in the coastal zone, for several hundred kilometers alongshore and as far as 100 km offshore. The blocking effect of coastal terrain has a strong influence on the diurnal circulation.

Current affiliation: NOAA/ETL, Boulder, Colorado

Corresponding author address: S. Bielli, Dept. of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195. Email: soline@atmos.washington.edu

Abstract

A triply nested mesoscale atmospheric numerical model is used to study the dynamics of the diurnal cycle of the summertime lower atmosphere along the central Oregon coast. Simulations of four consecutive days in September 1998, during which the winds were strong and northerly, are analyzed. Comparisons with profiler observations suggest that the model performed well enough to provide a useful estimate of the diurnal circulation. During the four days of interest, the low-level wind pattern has a broad maximum between Cape Blanco and Cape Mendocino, with a large north–south gradient along the Oregon coast. The low-level jet undergoes diurnal horizontal and vertical displacements, which partially resemble previous observational and modeling results along the California coast. In both the model and the profiler data, there is a minimum in northerly wind between 1500 and 1800 UTC (0700 and 1000 local time), and a double maximum in offshore flow above the marine boundary layer, with peaks near 0700 and 1600 UTC. At the jet core height, the advection of alongshore momentum is an important component of the alongshore force balance. After 2100 UTC, this advection is the main term balancing the pressure gradient force. Thus, in contrast to the previous results for the California coast, the diurnal circulation is fundamentally three-dimensional in the coastal zone, for several hundred kilometers alongshore and as far as 100 km offshore. The blocking effect of coastal terrain has a strong influence on the diurnal circulation.

Current affiliation: NOAA/ETL, Boulder, Colorado

Corresponding author address: S. Bielli, Dept. of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195. Email: soline@atmos.washington.edu

Save
  • Banta, R. M., 1995: Sea breeze shallow and deep on the California coast. Mon. Wea. Rev., 123 , 36143622.

  • Banta, R. M., L. D. Olivier, and D. H. Levinson, 1993: Evolution of the Monterey Bay sea-breeze layer as observed by pulsed Doppler lidar. J. Atmos. Sci., 50 , 39593982.

    • Search Google Scholar
    • Export Citation
  • Beardsley, R. C., C. E. Dorman, C. A. Friehe, L. K. Rosenfeld, and C. D. Winant, 1987: Local atmospheric forcing during the Coastal Ocean Dynamics Experiment, Pt. 1, Description of the marine boundary layer and atmospheric conditions over a northern California upwelling region. J. Geophys. Res., 92 , 14671488.

    • Search Google Scholar
    • Export Citation
  • Bridger, A. F. C., W. C. Brick, and P. F. Lester, 1993: The structure of the marine inversion layer off the central California coast: Mesoscale conditions. Mon. Wea. Rev., 121 , 335351.

    • Search Google Scholar
    • Export Citation
  • Burk, S. D., and W. T. Thompson, 1996: The summertime low-level jet and marine boundary layer structure along the California coast. Mon. Wea. Rev., 124 , 668686.

    • Search Google Scholar
    • Export Citation
  • Burk, S. D., T. Haack, and R. M. Samelson, 1999: Mesoscale simulation of supercritical, subcritical, and transcritical flow along coastal topography. J. Atmos. Sci., 56 , 27802795.

    • Search Google Scholar
    • Export Citation
  • Dorman, C. E., and C. D. Winant, 1995: Buoy observations of the atmosphere along the west coast of the United States, 1981–1990. J. Geophys. Res., 100 , 1602916044.

    • Search Google Scholar
    • Export Citation
  • Dorman, C. E., D. P. Rogers, W. Nuss, and W. T. Thompson, 1999: Adjustment of the summer marine boundary layer around Point Sur, California. Mon. Wea. Rev., 127 , 21432159.

    • Search Google Scholar
    • Export Citation
  • Dorman, C. E., T. Holt, D. P. Rogers, and K. Edwards, 2000: Large-scale structure of the June-July 1996 marine boundary layer along California and Oregon. Mon. Wea. Rev., 128 , 16321652.

    • Search Google Scholar
    • Export Citation
  • Elliott, D. L., and J. J. O'Brien, 1977: Observational studies of the marine boundary layer over an upwelling region. Mon. Wea. Rev., 105 , 8698.

    • Search Google Scholar
    • Export Citation
  • Holt, T. R., 1996: Mesoscale forcing of a boundary layer jet along the California coast. J. Geophys. Res., 101 , 42354254.

  • Johnson, A. Jr,, and J. J. O'Brien, 1973: A study of an Oregon sea breeze event. J. Appl. Meteor., 12 , 12671283.

  • Kessler, E., 1969: On the Distribution and Continuity of Water Substance in Atmospheric Circulation. Meteor. Monogr., No. 32, Amer. Meteor. Soc., 84 pp.

    • Search Google Scholar
    • Export Citation
  • Korac̆in, D., and C. Dorman, 1999: Marine atmospheric boundary layer divergence and clouds along California in June 1996. Preprints, Third Conf. on Coastal Atmospheric and Oceanic Prediction and Processes, New Orleans, LA, Amer. Meteor. Soc., 314–318.

    • Search Google Scholar
    • Export Citation
  • Meitin, R. J., and D. W. Stuart, 1977: The structure of the marine inversion in northwest Oregon during 26–30 August 1973. Mon. Wea. Rev., 105 , 748761.

    • Search Google Scholar
    • Export Citation
  • Neiburger, M., D. S. Johnson, and C. Chien, 1961: Studies of the Structure of the Atmosphere over the Eastern Pacific Ocean in the Summer. University of California Publications in Meteorology, Vol. 1, No. 1, 1–94.

    • Search Google Scholar
    • Export Citation
  • Ralph, F. M., P. J. Neiman, P. O. G. Persson, J. M. Bane, M. L. Cancillo, J. M. Wilczak, and W. Nuss, 2000: Kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals. Mon. Wea. Rev., 128 , 283300.

    • Search Google Scholar
    • Export Citation
  • Samelson, R., and Coauthors. 2002: Wind stress forcing of the Oregon coastal ocean during the 1999 upwelling season. J. Geophys. Res., in press.

    • Search Google Scholar
    • Export Citation
  • Weber, B. L., D. B. Wuertz, D. C. Welsh, and R. McPeek, 1993: Quality controls for profiler measurements of winds and RASS temperatures. J. Atmos. Oceanic. Technol., 10 , 452464.

    • Search Google Scholar
    • Export Citation
  • Winant, C. D., C. E. Dorman, C. A. Friehe, and R. C. Beardsley, 1988: The marine layer off Northern California: An example of supercritical channel flow. J. Atmos. Sci., 45 , 35883605.

    • Search Google Scholar
    • Export Citation
  • Xue, M., K. K. Droegemeier, V. Wong, A. Shapiro, and K. Brewster, 1995: ARPS version 4.0 user's guide. Center for Analysis and Prediction of Storms, 380 pp. [Available from CAPS, University of Oklahoma, Norman, OK 73072.].

    • Search Google Scholar
    • Export Citation
  • Zemba, J., and C. A. Friehe, 1987: The marine atmospheric boundary layer jet in the Coastal Ocean Dynamics Experiment. J. Geophys. Res., 92 , 14891496.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 99 30 0
PDF Downloads 39 16 0