Analysis of Surface Temperature and Heat Flux Relationships
Sfc
Δ
T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc DeltaT = (swgdn + (swgdn – swgnt) )
+
(lwgdn – (lwgdn – lwgnt) )
-
hflux
–
eflux + ghland
A
B
C
D
E
F
G
…
a
n
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)
We can quickly eliminate terms E and F
It isn’t latent heat flux
In the Sahara Desert
Even though we believe this is strongly diurnal, it still shows up in monthly means
As should some net difference
Sfc Delta-T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Q
net = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc DeltaT = (swgdn + (swgdn – swgnt) )
+
(lwgdn – (lwgdn – lwgnt) ) + ghland
A
B
C
D
G
…
a
n
d
w
e
h
a
v
e
a
l
l
o
f
t
h
e
s
e
e
x
p
r
e
s
s
i
o
n
s
f
o
r
E
R
A
-
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t
e
r
i
m
e
x
c
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p
t
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d
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m
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t
a
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)
We can quickly eliminate terms E and F
Sfc
Δ
T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Q
net = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc
Δ
T = (swgdn + (swgdn – swgnt) )
+
(lwgdn) + ghland
A
B
C
G
…
a
n
d
w
e
h
a
v
e
a
l
l
o
f
t
h
e
s
e
e
x
p
r
e
s
s
i
o
n
s
f
o
r
E
R
A
-
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t
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r
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m
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x
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t
)
Term D, upwelling longwave, by definition has
To be lower in MERRA-2, it says that we have
A cold bias…so it isn’t contributing to the bias
Sfc
Δ
T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Q
net = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc
Δ
T = (swgdn – swgnt) )
+
(lwgdn) + ghland
B
C
G
…
a
n
d
w
e
h
a
v
e
a
l
l
o
f
t
h
e
s
e
e
x
p
r
e
s
s
i
o
n
s
f
o
r
E
R
A
-
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n
t
e
r
i
m
e
x
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p
t
g
h
l
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d
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b
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m
p
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t
a
n
t
)
Downwelling Shortwave, A, could be an issue in cloudy regions…but
It looks pretty good compared with ERA-interim in the desert.
Sfc
Δ
T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Q
net = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc
Δ
T =
(swgdn – swgnt) )
+
(lwgdn) + ghland
B
C
G
…
a
n
d
w
e
h
a
v
e
a
l
l
o
f
t
h
e
s
e
e
x
p
r
e
s
s
i
o
n
s
f
o
r
E
R
A
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Upwelling shortwave , B…the albedo factor may be contributing
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Sfc
Δ
T = Qnet – Sensible Heat Flux – Latent Heat Flux + Ground Heat Flow
Q
net = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave – Upwelling Longwave)
Substituting the GEOS-5 expressions for each of these fields gives:
Sfc
Δ
T =
(swgdn – swgnt) )
+
(lwgdn)
+ ghland
B
C
G
…
a
n
d
w
e
h
a
v
e
a
l
l
o
f
t
h
e
s
e
e
x
p
r
e
s
s
i
o
n
s
f
o
r
E
R
A
-
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n
t
e
r
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m
e
x
c
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p
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Radiating at the appropriate temperature, it should be close to ERA-i. And while not
Exactly like ERA-i , the mean difference is only on order of 10 to maybe 15 W/m2…
not enough to be the 2-3K differences we see
While we see a lot
Of blue over the desert
It is in the 10W/m2 range
It turns out the ground heat flow term has a large diurnal cycle in deserts
The equation describing the conduction of heat through the ground
G = Ks *
Δ
T /
Δ
depth
,
where Ks is the thermal conductivity (dependent on ground type soil, clay, sand)
Exploring the interplay between surface temperature, sensible heat flux, latent heat flux, and ground heat flow, utilizing data from GEOS-5 and ERA-interim models to understand the impact of different heat flux components on surface temperature variations in diurnal cycles and monthly means. Comparison with MERRA-2 reveals potential biases and challenges, particularly in the context of desert regions.
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Even though we believe this is strongly diurnal, it still shows up in monthly means As should some net difference Sfc T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc DeltaT = (swgdn + (swgdn swgnt) )+(lwgdn (lwgdn lwgnt) ) - hflux eflux + ghland A B C D E F G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) We can quickly eliminate terms E and F It isn t latent heat flux In the Sahara Desert
Sfc Delta-T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc DeltaT = (swgdn + (swgdn swgnt) )+(lwgdn (lwgdn lwgnt) ) + ghland A B C D G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) We can quickly eliminate terms E and F
Sfc T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc T = (swgdn + (swgdn swgnt) )+(lwgdn) + ghland A B C G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) Term D, upwelling longwave, by definition has To be lower in MERRA-2, it says that we have A cold bias so it isn t contributing to the bias
Sfc T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc T = (swgdn swgnt) )+(lwgdn) + ghland B C G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) Downwelling Shortwave, A, could be an issue in cloudy regions but It looks pretty good compared with ERA-interim in the desert.
Sfc T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc T = (swgdn swgnt) )+(lwgdn) + ghland B C G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) Upwelling shortwave , B the albedo factor may be contributing to the cold bias in some small way (slightly brighter, slightly less sfc. net)
Sfc T = Qnet Sensible Heat Flux Latent Heat Flux + Ground Heat Flow Qnet = (Downwelling Shortwave + Upwelling Shortwave (albedo)) + (Downwelling Longwave Upwelling Longwave) Substituting the GEOS-5 expressions for each of these fields gives: Sfc T = (swgdn swgnt) )+(lwgdn) + ghland B C G and we have all of these expressions for ERA-interim except ghland (which may turn out to be very important) The Downwelling longwave term could be important. If we have clouds and aerosols Radiating at the appropriate temperature, it should be close to ERA-i. And while not Exactly like ERA-i , the mean difference is only on order of 10 to maybe 15 W/m2 not enough to be the 2-3K differences we see While we see a lot Of blue over the desert It is in the 10W/m2 range
It turns out the ground heat flow term has a large diurnal cycle in deserts The equation describing the conduction of heat through the ground G = Ks * T / depth, where Ks is the thermal conductivity (dependent on ground type soil, clay, sand)
