Book contents
- Frontmatter
- Contents
- List of figures
- List of tables
- Preface to the Third Edition
- Acknowledgments
- 1 Mountains and their climatological study
- 2 Geographical controls of mountain meteorological elements
- 3 Circulation systems related to orography
- 4 Climatic characteristics of mountains
- 5 Regional case studies
- 6 Mountain bioclimatology
- 7 Changes in mountain climates
- Appendix
- Index
- References
3 - Circulation systems related to orography
Published online by Cambridge University Press: 20 May 2010
- Frontmatter
- Contents
- List of figures
- List of tables
- Preface to the Third Edition
- Acknowledgments
- 1 Mountains and their climatological study
- 2 Geographical controls of mountain meteorological elements
- 3 Circulation systems related to orography
- 4 Climatic characteristics of mountains
- 5 Regional case studies
- 6 Mountain bioclimatology
- 7 Changes in mountain climates
- Appendix
- Index
- References
Summary
DYNAMIC MODIFICATION
The effects of topography on air motion operate over a wide range of scales and produce a hierarchy of circulation systems through the mechanism of dynamic and thermal factors. Here, we concentrate on three major types of dynamic process. First, extensive mountain ranges set up planetary-scale wave motion through large-scale rotational effects. Second, mountains give rise to modifications of synoptic-scale weather systems, especially fronts. Third, topography on all scales introduces wave motion through local gravitational effects. While these categories are not always sharply differentiated from one another, they provide a convenient basis for discussion. Detailed accounts of orographic effects on airflow are given in Alaka (1960), Nicholls (1973), Smith (1979a), and Hide and White (1980); Beer (1976) provides a convenient summary.
Planetary-scale effects
The influence of mountain barriers on the planetary-scale atmospheric circulation involves three principal processes: the transfer of angular momentum to the surface through friction and form drag; the blocking and deflection of airflow; and the modification of energy fluxes, particularly as a result of the airflow effects on cloud cover and precipitation. Various attempts have been made to distinguish the relative importance of these factors in generating standing planetary waves, through diagnostic, theoretical and modeling studies (Kasahara, 1980; see Barry and Carleton, 2001, pp. 294–300). Orography and diabatic heating (latent heat release, absorption of solar radiation, infrared cooling and surface sensible heat) each contribute to the forcing of the planetary waves, but their effects are poorly quantified according to Dickinson (1980).
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- Mountain Weather and Climate , pp. 125 - 250Publisher: Cambridge University PressPrint publication year: 2008