Land Surface Models

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Land Surface Models Surface Water Hydrology

• Cédric DAVID

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Outline

• 1. Introduction
• 2. Basic Models
• 3. Areas of improvement
• 4. Conclusions

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1. Introduction

• Land covers 30 of the Earths surface
• Shelter for human beings
• Storage of freshwater (essential for human life)
• Greater variability of weather above land than
  oceans

Understanding land surface processes is crucial
for human life
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1. Introduction

• How do Land Surface Models handle Surface Water
  Hydrology?

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Outline

• 1. Introduction
• 2. Basic Models
• 3. Areas of improvement
• 4. Conclusions

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2. Basic Models

• Bucket model
• Most simple model
• Fixed water capacity
• No soil charaterictics
• No vegetation

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2. Basic Models

• The Biosphere Atmosphere Transfer Scheme (BATS)
• Three soil layers
• One vegetation layer

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2. Basic Models

• SiB (Simple Biosphere)
• Two vegetation layers
• Three soil layers

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2. Basic Models

• Bucket, BATS and SiB models are 1-D models
  (vertical)
• Ignore horizontal interactions between adjacent
  cells
• Used in 3-D atmospheric models
• Only three land components (soil, snow and
  vegetation)
• No vegetation types
• No runoff

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Outline

• 1. Introduction
• 2. Basic Models
• 3. Areas of improvement
• 4. Conclusions

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3. Areas of improvement

• Moisture
• Runoff
• Snow

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3. Areas of improvement

• Moisture
• Darcys law

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3. Areas of improvement

• Moisture
• Infiltration excess runoff (Liang and
  Xie)infiltration is a function of the soil and
  of the soil moisture
• Moisture excess runoff (Liang and Xie)
• Niu and Yang (2006) Gravity Recovery And Climate
  Experiment (GRACE) compared to Noah (seasonal
  variability of TWS)

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3. Areas of improvement

• Runoff
• Boone et al. (2004) Comparison of LSMs
• ? good estimates of runoff

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3. Areas of improvement

• Runoff
• Simple Water Balance
• Schaake et al. (1996) Simple Water Balance
• Understand surface runoff processes ? runoff
  estimates comparable to more advanced models

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3. Areas of improvement

• Snow
• Ek et al. (2003)
• snowpack physics (snow albedo and conductivity)
• Snow cover fraction
• ? Improvement of wintertime conditions forecast

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Outline

• 1. Introduction
• 2. Basic Models
• 3. Areas of improvement
• 4. Conclusions

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4. Conclusions

• Land surface models crucial component of
  atmospheric models
• Basic models exist and can be improved
• Variety of improvements each serving its own
  purpose

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Thank you!Questions?
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3. Areas of improvement

• Sub-grid scale variability
• component approach
• tile approach
• statistical approach