Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Soil Processes
- Part IV Hydrometeorology
- 11 Water balance
- 12 Watershed hydrology
- 13 Surface energy fluxes
- 14 Turbulent fluxes
- 15 Soil moisture and the atmospheric boundary layer
- Part V Biometeorology
- Part VI Terrestrial Plant Ecology
- Part VII Terrestrial Forcings and Feedbacks
- Index
- Plate section
- References
15 - Soil moisture and the atmospheric boundary layer
from Part IV - Hydrometeorology
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Soil Processes
- Part IV Hydrometeorology
- 11 Water balance
- 12 Watershed hydrology
- 13 Surface energy fluxes
- 14 Turbulent fluxes
- 15 Soil moisture and the atmospheric boundary layer
- Part V Biometeorology
- Part VI Terrestrial Plant Ecology
- Part VII Terrestrial Forcings and Feedbacks
- Index
- Plate section
- References
Summary
Chapter summary
The atmospheric boundary layer is the layer of the atmosphere above Earth's surface that is directly affected over the course of a day by surface fluxes such as sensible heat, latent heat, water vapor, and CO2. Sensible heat from the surface warms the boundary layer as heat is carried vertically by turbulent motion. Evaporated water moistens the boundary layer, releasing latent heat during condensation and forming clouds. The diurnal cycle of surface fluxes imparts a diurnal cycle to the boundary layer. At night, the boundary layer is typically stable with weak turbulent motion. Surface heating during the day warms the boundary layer and it becomes unstable. Soil water greatly influences the boundary layer by its effect on the partitioning of net radiation into sensible and latent heat. The Bowen ratio is typically smaller where soil water does not limit evapotranspiration, and the boundary layer is cooler, moister, and shallower than in the absence of evapotranspiration. Dry sites have lower latent heat flux and a warmer, drier, and deeper boundary layer. The changes in surface fluxes and boundary layer characteristics associated with wet soil may create conditions that favor precipitation. Surface heterogeneity in soil moisture can also generate mesoscale atmospheric circulations. Large patches of wet soil interspersed in a comparatively dry landscape create a contrast in surface fluxes.
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- Information
- Ecological ClimatologyConcepts and Applications, pp. 214 - 226Publisher: Cambridge University PressPrint publication year: 2008