2 nearby locations in the great basin desert why the ...cassano/atoc4750/lecture_notes/ch04b_… ·...
TRANSCRIPT
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Atmospheric and Surface Energy and Moisture Budgets
Energy Budget Components
Why Do We CareAbout Energy Budgets?
• Determines overall climate• Determines local variations in climate• Determines response of climate to
human changes (e.g., agriculture, urbanization) and natural changes
2 nearby locations in the Great Basin Desert – different energy budgets lead to different microclimates
(Sand, gravel)
(Salt flat)
Why the Difference?We will discuss this in the next chapter.
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How are desert energy budget components different from global
energy budget?
?
M ?
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L ?
M
?
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L ?
L ?
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L ?
L
?
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M
Moisture Budget Components
Why Care About Details of the Water Budgets?
Determines how much water available for • evaporation• replenishment of water table• plants• runoff to reservoirs, flash floods
Implication for
• Agriculture• Cloud seeding• Emergency response (flooding)• Water management – dams, wells, water
rights
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? L
? M/L
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? M
? ? M/L M/L
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? M/L
Atmospheric and Surface Energy and Moisture Budgets
Focus on Budgets at the Surface to Understand Conditions Where We
Live
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Surface Radiation Budget
R = (Q+q)(1-a) – I + I¯
R – net radiation
Q – direct solar radiationq – diffuse solar radiation
a- albedoI – longwave radiation
Components of surface radiation budget measured at a location in the Great Basin. (cloud-free, September)
Noontime Sun
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I ?
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger
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How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q?
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds
•a?
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds•a - Larger because of less vegetation
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How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds•a - Larger because of less vegetation•I¯ ?
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds•a - Larger because of less vegetation•I¯ - Probably less
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How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds•a - Larger because of less vegetation•I¯ - Probably less•q?
How is net radiation different in the desert?R = (Q+q)(1-a) – I + I¯
•I - Larger because T-surface is larger•Q – Larger because of less clouds•a - Larger because of less vegetation•I¯ - Probably less•q – Smaller because of less cloud
Surface Energy Budget
R = LE + H + G
R – net radiationLE – latent heat flux (evaporation & transpiration)
H – heat flux to atmosphereG – heat flux into ground
Annually
0
How Would LE, H, and G be different in the desert?
• LE?• Depends on amount of energy and
moisture available• LE – Small or 0 in desert
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How Would LE, H, and G be different in the desert?
• H?• Depends on the temperature
of the ground (what does this depend on?)
• H probably higher in the desert
How Would LE, H, and G be different in the desert?
• G?• Depends on
- thermal conductivity of substrate (sand, rock, playa)
- amount of energy available• Will discuss this in more detail
in next chapter
The diurnal variation of the components of the surface energy budget for three different surfaces
Noontime Sun
Why are the Energy Budget components different?
Fig. 4.15 The annual variation of the surface energy budget components at three different locations
Why are the Energy Budget components different?
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The Oasis Effect –An energy budget peculiar to the desert
What causes LE to be larger than R?
Oasis – Death Valley
Desert Heat
• More solar energy input to surface because of less cloud (connection between water budget and energy budget)
• Drier substrate, so less solar energy lost to evaporation and more available for heating surface (and atmosphere)
• Hotter surface means more heat input to atmosphere and substrate