Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
26 - Seasonal-to-Interannual Variability
from Part VI - Terrestrial Forcings and Feedbacks
Published online by Cambridge University Press: 05 November 2015
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
Summary
Chapter Summary
Atmospheric and oceanic processes and their coupling dominate much of the study of seasonal-to-interannual climate variability. However, land surface processes also contribute to climate variability. Soil moisture is a key aspect of seasonal precipitation forecasts. Recycling of precipitation in evapotranspiration can lead to a positive feedback by which wet soils pump more moisture into the atmosphere, which enhances rainfall and further wets the soil. Conversely, dry soils, with low rates of evapotranspiration, can reduce rainfall. The retention of precipitation by soil and the influence of soil moisture on subsequent evapotranspiration contribute to and amplify interannual precipitation variability over tropical and middle latitudes. The presence of snow is also an important initial condition required for accurate forecasts. The high albedo of snow-covered surfaces prevents the surface from warming during the day. On warm days, a large portion of net radiation at the surface is used to melt snow. By cooling the surface and reducing the land–ocean temperature contrast, snow can influence summer precipitation in monsoon climates. The seasonal emergence of leaves in spring imparts a discernible signal to air temperature. Greater latent heat flux with leaf emergence cools air temperature.
Soil Moisture
Soil moisture regulates boundary layer processes through the partitioning of net radiation into sensible and latent heat fluxes (Figure 26.1). Atmospheric model simulations have routinely demonstrated the importance of soil moisture, through its effect on evapotranspiration, for climate simulation (Seneviratne et al. 2010). These simulations typically alter soil moisture or more generally soil wetness (the effect of soil moisture on evapotranspiration). Such studies demonstrate a positive feedback in which wet soils pump more moisture into the atmosphere, which can enhance rainfall and further wet the soil. Conversely, dry soils, with low rates of evapotranspiration, reduce rainfall.
One experimental approach has been to artificially set soil wetness to prescribed values that do not change over time and to contrast climate simulations using wet and dry soils. Shukla and Mintz (1982) used this method to demonstrate the effect of evapotranspiration on climate. Using a global model, they compared a simulation with perpetually dry soils to that with perpetually wet soils.
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- Information
- Ecological ClimatologyConcepts and Applications, pp. 483 - 499Publisher: Cambridge University PressPrint publication year: 2015