Abstract
Local winds were studied around a valley city, by using a high resolution two-dimensional mesoscale model forced by surface temperatures from a measurement campaign around Lanzhou City, China, during stagnant conditions. In the simulations nighttime winds are purely katabatic downslope winds without urban effects, despite the fact that the city is 6–7°C warmer than its surroundings all night. In contrast, daytime near-surface winds result from upslope flow resisted by an opposing simultaneous urban heat-island circulation (UHIC). Hence winds remain weak and variable around a city in a narrow valley during daytime. These conditions may lead to severe air quality problems day and night.
The local circulations are sensitive to the widths of the valley and/or city,and also latitude, as is demonstrated by model experiments. Interestingly, in a flat and calm environment an extratropical daytime UHIC cell may turn into a weak `anti-UHIC' by the morning, due to frictional decoupling after sunset and subsequent inertial oscillation during the night, analogously tothe land breeze and nocturnal low-level jet formation.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Alestalo, M. andSavijärvi, H.: 1985, ‘Mesoscale Circulations in a Hydrostatic Model: Coastal Convergence and Orographic Lifting’ Tellus 37A, 156-162.
Alpert, P., Cohen, A., Doron, E., andNeumann, J.: 1982, ‘A Model Simulation of the Summer Circulation from the Eastern Mediterranean Past Lake Kinneret in the Jordan Valley’ Mon. Wea. Rev. 110, 994-1006.
Atkinson, B. W.: 1981, Meso-Scale Atmospheric Circulations, Academic Press, 495 pp.
Blackadar, A. K.: 1957, ‘Boundary-Layer Wind Maxima and their Significance for the Growth of Nocturnal Inversions’ Bull. Amer. Meteorol. Soc. 38, 283-290.
Bornstein, R. D.: 1968, ‘Observations of the Urban Heat Island Effect in New York City’ J. Appl. Meteorol. 7, 575-585.
Chen, Z. andWang, S.: 1993, ‘Analysis of Wind Fields in Lanzhou City’ in C. Chen et al. (eds.), Boundary Layer Observation and Atmospheric Dispersion Modelling in Complex Terrain, China Meteorological Press, pp. 23-27 (in Chinese). [Available via book stores, ISBN 7-5029-1544-3.]
Hertig, J.-A.: 1995, ‘Urban Climates and Air Pollution in Small Swiss Cities’ in Cermak et al. (eds.), Wind Climate in Cities, NATO ASI Series E277, Kluwer Academic Publishers, Dordrecht, pp. 353-382.
Landsberg, H. E.: 1981, The Urban Climate, Academic Press, 275 pp.
Martin, C. L. andPielke, R. A.: 1983, ‘The Adequacy of the Hydrostatic Assumption in Sea Breeze Modelling over Flat Terrain’ J. Atmos. Sci. 40, 1472-1481.
Oke, T. R.: 1982, ‘The Energetic Basis of the Urban Heat Island’ Quart. J. Roy. Meteorol. Soc. 108, 1-24.
Oort, A. O.: 1983, Global Atmospheric Circulation Statistics 1958-1973, NOAA Professional Paper 14. [Available from U.S. Department of Commerce, Rockville, MD.]
Pielke, R. A.: 1984, Mesoscale Meteorological Modelling, Academic Press, 612 pp.
Rotunno, R.: 1983, ‘On the Linear Theory of the Land and Sea Breeze’ J. Atmos. Sci. 40, 1999-2009.
Savijärvi, H. 1985, ‘The Sea Breeze and Urban Heat Island in a Numerical Model’ Geophysica 21, 115-126.
Savijärvi, H.: 1991, ‘The United States Great Plains Diurnal ABL Variation and the Nocturnal Low-Level Jet’ Mon. Wea. Rev. 119, 833-840.
Savijärvi, H.: 1992, ‘On Surface Temperature and Moisture Prediction in Atmospheric Models’ Contr. Atmos. Phys. 65, 281-292.
Savijärvi, H.: 1997, ‘Diurnal Winds around Lake Tanganyika’ Quart. J. Roy. Meteorol. Soc. 123, 901-918.
Savijärvi, H. andAlestalo, M.: 1988, ‘The Sea Breeze over a Lake or Gulf as the Function of the Prevailing Flow’ Beitr. Phys. Atmos. 61, 98-104.
Savijärvi, H. andRäisänen, P.: 1998, ‘Longwave Optical Properties of Waterclouds and Rain’ Tellus 50A, 1-11.
Savijärvi, H. andSiili, T.: 1993, ‘The Martian Slope Winds and the Nocturnal PBL Jet’ J. Atmos. Sci. 50, 77-88.
Savijärvi, H., Arola, A., andRäisänen, P.: 1997, ‘Shortwave Optical Properties of Precipitating Waterclouds’ Quart. J. Roy. Meteorol. Soc. 123, 883-899.
Schultz, P. andWarner, T. T.: 1982, ‘Characteristics of Summer-Time Circulations and Pollutant Ventilation in the Los Angeles Basin’ J. Appl. Meteorol. 21, 672-682.
Shreffler, J. H.: 1978, ‘Detection of Centripetal Heat-Island Circulations from Tower Data in St. Louis’ Boundary-Layer Meteorol. 15, 229-242.
Smith, E. A. andShi, L.: 1992, ‘Surface Forcing of the Infrared Cooling Profile over the Tibetan Plateau. Part I: Influence of Relative Longwave Radiative Heating at High Altitude’ J. Atmos. Sci. 49, 805-822.
Vukovich, F. M. andDunn, J. W.: 1978, ‘A Theoretical Study of the St. Louis Heat Island: Some Parameter Variations’ J. Appl. Meteorol. 17, 1585-1594.
Wang, H., Chen, C., andHuang, J.: 1994, ‘Longwave Radiative Effect of Smog Layer and its Influence on the Boundary Layer Temperature Stratification’ Chinese J. Atmos. Sci. 18, 23-31.
Wang, J.: 1992, ‘Turbulence Characteristics in an Urban Atmosphere of Complex Terrain’ Atmos. Environ. 26A, 2717-2714.
Yan, H. andAnthes, R. A.: 1987, ‘The Effect of Latitude on the Sea Breeze’ Mon. Wea. Rev. 115, 936-956.
Yoshikado, H.: 1992, ‘Numerical Study of the Daytime Urban Effect and its Interaction with the Sea Breeze’ J. Appl. Meteorol. 31, 1146-1164.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Savijärvi, H., Liya, J. Local Winds In A Valley City. Boundary-Layer Meteorology 100, 301–319 (2001). https://doi.org/10.1023/A:1019215031007
Issue Date:
DOI: https://doi.org/10.1023/A:1019215031007