Radiative Transfer of West Atlantic Cumulus Chang Sun 1 Jiaxi Wang 2 Shuwan Huang 2 1 Scripps Institution of Oceanography 2 Department of Chemistry and Biochemistry ID: 253724
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Slide1
A Simple Model for Cloud Radiative Transfer of West Atlantic Cumulus
Chang Sun
1
,
Jiaxi
Wang
2
,
Shuwan
Huang
2
1
Scripps
Institution
of Oceanography
2
Department of
Chemistry
and Biochemistry
University of California, San Diego, 9500 Gilman Drive, La Jolla 92092, CA, United States Slide2
OutlineBackground
Model
Results and AnalysisConclusionSlide3
Clouds & Global Climate Slide4
Clouds & Earth’s Radiation Budget
Bull. Am. Met. Soc. 78, 197-208Slide5
Cumulus
Piled clouds with a
flat base
and tops in the
shape of a cauliflower
Typically in the
boundary layer
of atmosphere that is nearest to the surface of Earth.
Roel
Neggers
, ISBN 90-5808-774-3Slide6
ModelTarget: West Atlantic Cumulus
For shortwave:
Assumption:
Back scattering fraction (
β
) is zero
Single scattering albedo
wo
is 0.95
Z
enith
is
45°
DeVault
J E el al., 1983Slide7
ModelFor
longwave
:
a0 —— mass absorption coefficientW
——
liquid water path
Neglect the cloud refl
e
ctivity
(Yamamoto
et
al.,
1970)
G
.
L.
Stephens
, 19
7
8Slide8
Western Atlantic Cumulus
Marile
’
Colo’n
-
Robles et al
., 2006
r
n
(r)Slide9
Western Atlantic Cumulus
Depth of cloud: Z=
z
top
-z
base
=1100
m
de
Roode
S
R and
Duynkerke
P G
., 1996 Slide10
FormulasSlide11
Results
N
(#
cm
-3
)
total number concentration of drops
207.1
w
l
(
g
/
kg)
liquid water mixing ratio
0.24
r
(
μm
)
mean drop size radius
6.67
r
e
(
μm
)
drop equivalent radius
7.52
σ
ext
(
m
-1
)
extinction cross section for shortwave radiation
0.062
W
l
(g m-2)liquid water path339.8τext (m)optical depth for shortwave radiation67.80Ttransmissivity for shortwave radiation0.28Rreflectivity for shortwave radiation0.55Aabsorptivity for shortwave radiation0.16εemissivity for longwave ~1
Data of western Atlantic cumulus from
Marile
’
Colo’n
-Robles et al. [2006] Slide12
Shortwave radiation
I
ncoming
solar
radiation
0
.25S
0
R
& A increase
T decreases
with concentration
N>2N
0
, R barely increases,
nearly remains constantSlide13
Shortwave radiation
Optical depth increases
linearly with
concentrationSlide14
Longwave radiation
E has been near 1 at original concentration
When concentration increases, E gets closer to 1.Slide15
Conclusion
With droplets concentration rising, optical depth will increase linearly, which contributes to more solar radiation reflection and
longwave
radiation emission of Western Atlantic cumulus.
N↑-----
>
τ
↑----->
R,E↑
Their
ultimate
effect
on
temperature
of
the
earth
is
complex
and
remains
to
be
exploredSlide16
Thank you
！