Exchange Processes Between the
Earth‘s Surface and the Atmosphere
1.
2.
3.
Energy budget
Boundary layers
Observations
Climatic system:
Open components
Coupling between individual components
Boundary layers (fluxes of matter, energy and momentum)
Energy Budget at the Surface
Fradsfs = FSWs↓ (1-A sfs)-εσT4+ FLW↓
Fradsfs is the net radiative flux,
FSWs↓ is the short-wave radiation
A sfs is the albedo
ε is the infrared emissivity,
FLW↓ is the lnog-wave radiation (back radiation)
From the conservation of energy for ideal surface it follows:
Fradsfs - FSH↑ -FLH ↑ -FG↓ -FM =0
FSH↑ =is the sensible heat flux (differences in temperatures of
the surface and the air)
FLH↑ =LeE is the latent heat flux (mostly evaporation)
FG↓ is the sensible heat flux to or from the soil/water (mainly
due to heat conduction)
FM = LM(Ms -Fs), melting (Ms) and freezing (Fs) rates
For annual mean conditions: FG↓ =0 and we have for land
Fradsfs - FSH↑ -LeE-LM(Ms -Fs) =0
Energy budget
of a layer
∆H s
↑
↑
sfs
= Frad
− FSH
− FLH
− FG↓ − Lm ( M S − FS )
∆t
∂T
FG = − K
∂z
∂
∂FG
This is valid if there are no sources or sinks of
( ρcT ) = −
∂t
∂z
energy within the slab, c-specific heat
∂T ∂ ∂F
= K
ρc
This is valid if ρ and c are constant
∂t ∂z ∂z
Variations of temperature can be used to estimate the heat fluxes into the ground
Dynamic Structure of the
Atmosphere
Newtonean law:
τ
∂u
= −νK
∂z
ρ
Logaritmic layer
τ = const
K = f ( z)
1
z
u ( z ) = u* ln
z0
k
Exchange of Heat Trough
Sensible Heat
FSH = ρc p w θ
'
Eddy correlation
approach
Bulk aerodynamic
approach
FSH
FSH
'
∂θ
= − K H ρc p
∂z
= − ρc p Ch v( z ) [θ ( z ) − θ (0)]
Ch = Cd = 0.0013
Exchange of Heat Trough Water
Exchange/Evaporation
E = ρq w
'
'
∂q
E = − ρKW
∂z
E = − ρc p Ce v( z ) [q ( z ) − q (0)]
τ = − ρC d v( z ) v( z )
Cd is a function of stability,
surface roughnes, etc.
τ ⋅v
0.02-0.04W/m2