Cloud susceptibility from MODIS Cloud susceptibility from MODIS Level-3 daily cloud products Level-3 daily cloud products Lazaros Oreopoulos Lazaros Oreopoulos and and Steven Platnick Steven Platnick UMBC’s JCET UMBC’s JCET and and NASA GSFC’s Climate and Radiation Branch NASA GSFC’s Climate and Radiation Branch
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Cloud susceptibility from MODIS Level-3 daily cloud products Lazaros Oreopoulos and Steven Platnick UMBC’s JCET and NASA GSFC’s Climate and Radiation Branch.
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Cloud susceptibility from MODIS Level-3 Cloud susceptibility from MODIS Level-3 daily cloud productsdaily cloud products
Lazaros OreopoulosLazaros Oreopoulosandand
Steven PlatnickSteven Platnick
UMBC’s JCETUMBC’s JCET
and and
NASA GSFC’s Climate and Radiation BranchNASA GSFC’s Climate and Radiation Branch
Sλ =
dRλ (τ λ ,gλ , %ωλ )dN
=∂Rλ
∂τ λ
dτ λ
dre
dredN
+∂Rλ
∂gλ
dgλ
dre
dredN
+∂Rλ
∂ %ωλ
d%ωλ
dre
dredN
+ + –– –– –– ++ – – ++ –– ––
ΔR =
wiFi↑ τ i + Δτ i , gi + Δgi , %ω i + Δ %ω i( )
i∑
μ 0Fe↓
−wiFi
↑ τ i , gi , %ω i( )i
∑μ 0Fe
↓
From a BB RT code:From a BB RT code:
Susceptibility and relative susceptibilitySusceptibility and relative susceptibility
Where Where ΔΔττ, , ΔΔg, g, are due to are due to ΔΔrree (< 0)(< 0) changes arising from changes arising from ΔΔNN (> 0) (> 0) changes changes
under constant LWCunder constant LWC:: Δ %ω
N =3LWC
4ρwπk3re3 ⇒ Δre =re 1−
NN + ΔN
⎛⎝⎜
⎞⎠⎟
1 3⎡
⎣⎢⎢
⎤
⎦⎥⎥=re 1−
1
1+ΔNN
⎛
⎝
⎜⎜⎜
⎞
⎠
⎟⎟⎟
⎡
⎣
⎢⎢⎢
⎤
⎦
⎥⎥⎥
1 3
⇒Δrere
≈−13ΔNN
ΔΔrree determined by specifying either: determined by specifying either:
(1) absolute change in (1) absolute change in N, N, ΔΔNN (e.g., 1 cm (e.g., 1 cm-3-3) susceptibility) susceptibility (2) relative change in (2) relative change in N, N, ΔΔN/N N/N (e.g., 10%) relative susceptibility(e.g., 10%) relative susceptibility
Theoretical calculations (no atmosphere or surface)Theoretical calculations (no atmosphere or surface)
0.0 0.2 0.4 0.6 0.8cloud albedoTerra, October 2005Terra, October 2005
Susceptibility correlates with effective radiusSusceptibility correlates with effective radius
-180 -120 -60 0 60 120 180
90
60
30
0
-30
-60
-90
longitude
latitude
0 10 20 30 40 50optical thickness
-180 -120 -60 0 60 120 180
90
60
30
0
-30
-60
-90
longitude
latitude
4 8 12 16 20 24 28effective radius (µm)
-180 -120 -60 0 60 120 180
90
60
30
0
-30
-60
-90
longitude
latitude
0 2 4 6 8relative susceptibility x 1000
-180 -120 -60 0 60 120 180
90
60
30
0
-30
-60
-90
longitude
latitude
0.0 0.2 0.4 0.6 0.8cloud albedo
Relative suscept. correlates with intermediate Relative suscept. correlates with intermediate albedosalbedos
Terra, October 2005Terra, October 2005
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5 6 7 8
JanuaryOceanLand
susceptibility x 1000
0
0.02
0.04
0.06
0.08
0.1
0 1 2 3 4 5 6 7 8
April
susceptibility x 1000
0
0.02
0.04
0.06
0.08
0.1
0 1 2 3 4 5 6 7 8
July
susceptibility x 1000
0
0.02
0.04
0.06
0.08
0.1
0 1 2 3 4 5 6 7 8
October
susceptibility x 1000
Susceptibility for continental and marine cloudsSusceptibility for continental and marine clouds
TerraTerra
0
0.02
0.04
0.06
0.08
0.1
0.12
0 1 2 3 4 5 6 7 8
JanuaryOceanLand
relative susceptibility x 1000
0
0.01
0.02
0.03
0.04
0.05
0.06
0 1 2 3 4 5 6 7 8
April
relative susceptibility x 1000
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 1 2 3 4 5 6 7 8
July
relative susceptibility x 1000
0
0.02
0.04
0.06
0.08
0.1
0 1 2 3 4 5 6 7 8
October
relative susceptibility x 1000
Terra, relative susceptibilityTerra, relative susceptibilityRelative suscept. for continental and marine cloudsRelative suscept. for continental and marine clouds
Susceptibility-cloud fraction relations are important!Susceptibility-cloud fraction relations are important!
SummarySummary
• Susceptibility is a useful concept for identifying regions prone to significant Susceptibility is a useful concept for identifying regions prone to significant IAE radiative perturbations not only due to their proximity to pollution IAE radiative perturbations not only due to their proximity to pollution sources, but also due to the nature of the prevailing clouds under current sources, but also due to the nature of the prevailing clouds under current climate conditions; it therefore provides an additional constraint in cloud climate conditions; it therefore provides an additional constraint in cloud modeling studiesmodeling studies
• A global picture of liquid cloud susceptibility can be obtained from MODIS A global picture of liquid cloud susceptibility can be obtained from MODIS in a straightforward manner with the aid of some RT modelingin a straightforward manner with the aid of some RT modeling
• Significant seasonal variations of susceptibility are observed, consistent Significant seasonal variations of susceptibility are observed, consistent with seasonal shifts in cloud patterns and propertieswith seasonal shifts in cloud patterns and properties
• As expected, marine clouds are more susceptible than continental cloudsAs expected, marine clouds are more susceptible than continental clouds• Morning-afternoon susceptibility differences are relatively smallMorning-afternoon susceptibility differences are relatively small• The current distribution of liquid cloud optical thickness and effective The current distribution of liquid cloud optical thickness and effective
radius, as observed from MODIS, yields ~1.5 Wmradius, as observed from MODIS, yields ~1.5 Wm-2-2 IAE for a uniform 10% IAE for a uniform 10% increase in CDNC under constant LWC conditionsincrease in CDNC under constant LWC conditions
Additional SlidesAdditional Slides
JanuaryJanuary
Absolute susceptibility Absolute susceptibility ΔΔN=1 cmN=1 cm-3-3, Aqua, Aqua