Cloud susceptibility from MODIS Level-3 daily cloud products Lazaros Oreopoulos and Steven Platnick...

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)

Susceptibility Susceptibility ΔΔNN=1 cm=1 cm-3-3 Relative susceptibility Relative susceptibility ΔΔNN//NN=10%=10%

ΔR ≈4π

9LWCτ

∂R

∂τk 3re

3ΔN ΔR ≈1

3τ

∂R

∂τ

ΔN

N

SZA=60°SZA=60°

Susceptibility from MODISSusceptibility from MODIS

• D3 data provide means of D3 data provide means of ττ and and rree and joint and joint ττ - - rree histograms at 1° histograms at 1°

• Either can be used to calculate broadband unperturbed and perturbed Either can be used to calculate broadband unperturbed and perturbed

(due to (due to ΔΔrree changes) albedos; their difference is susceptibility changes) albedos; their difference is susceptibility

• The albedo is obtained with the aid of a modified version of the BB SW The albedo is obtained with the aid of a modified version of the BB SW

RT code by Chou et al.RT code by Chou et al.

• Atmospheric and surface effects, consistent with retrievals, are includedAtmospheric and surface effects, consistent with retrievals, are included

• Daily susceptibility values are averaged to monthly scalesDaily susceptibility values are averaged to monthly scales

• Susceptibility has been calculated for four months (January, April, July, Susceptibility has been calculated for four months (January, April, July,

October 2005) of Collection 5 Terra and Aqua liquid cloud data October 2005) of Collection 5 Terra and Aqua liquid cloud data

• Here we show results only from joint Here we show results only from joint ττ - - rree histograms histograms

JanuaryJanuary

Susceptibility Susceptibility ΔΔNN=1 cm=1 cm-3-3, , LWCLWC=0.3 gm=0.3 gm-3-3, Terra, TerraAprilApril

JulyJuly OctoberOctober

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

90

60

30

0

-30

-60

-90

longitude

latitude

0 2 4 6 8 10susceptibility x 1000

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


JanuaryJanuary

Relative susceptibility Relative susceptibility ΔΔNN=10%, Terra=10%, TerraAprilApril


-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


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-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


-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 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


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-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


0

0.02

0.04

0.06

0.08

0.1

0 1 2 3 4 5 6 7 8

July


0

0.02

0.04

0.06

0.08

0.1

0 1 2 3 4 5 6 7 8

October


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


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


0

0.02

0.04

0.06

0.08

0.1

0 1 2 3 4 5 6 7 8

October


Terra, relative susceptibilityTerra, relative susceptibilityRelative suscept. for continental and marine cloudsRelative suscept. for continental and marine clouds

TerraTerra

0

1

2

3

4

5

-90 -60 -30 0 30 60 90

JanuaryTerraAqua

latitude

0

1

2

3

4

5

-90 -60 -30 0 30 60 90

April

latitude

0

1

2

3

4

5

-90 -60 -30 0 30 60 90

July

latitude

0

1

2

3

4

5

-90 -60 -30 0 30 60 90

October

latitude

Susceptibility, Terra-Aqua zonal contrast Susceptibility, Terra-Aqua zonal contrast

0

1

2

3

4

5

6

7

-90 -60 -30 0 30 60 90

April

latitude

0

1

2

3

4

5

6

7

-90 -60 -30 0 30 60 90

October

latitude

0

1

2

3

4

5

6

7

-90 -60 -30 0 30 60 90

January

TerraAqua

latitude

0

1

2

3

4

5

6

7

-90 -60 -30 0 30 60 90

July

latitude

Relative susceptibility, Terra-Aqua zonal contrast Relative susceptibility, Terra-Aqua zonal contrast

0

0.2

0.4

0.6

0.8

1

1.2

January April July October

global IAE for Δ =1 N cm-3TerraAqua

Month

0

0.5

1

1.5

2

January April July October

global IAE for Δ =10%NTerraAqua

Month

Examples of potential global IAE forcingsExamples of potential global IAE forcings

ΔΔNN=1 cm=1 cm-3-3, , LWC LWC = 0.3 gm= 0.3 gm-3-3 ΔΔNN//NN = 10% = 10%

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

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


AprilApril

JulyJuly

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


OctoberOctober

Susceptibility Susceptibility ΔΔNN=1 cm=1 cm-3-3, , LWCLWC=0.3 gm=0.3 gm-3-3, Aqua, Aqua

Relative susceptibility Relative susceptibility ΔΔNN=10%, Aqua=10%, AquaJanuaryJanuary AprilApril


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


The impact of cloud fractionThe impact of cloud fraction

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude


-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

longitude

latitude

0.0 0.2 0.4 0.6 0.8 1.0liquid cloud fractionTerra, October 2005Terra, October 2005

Impact of using 2D joints instead of meansImpact of using 2D joints instead of means

Aqua, January 2005Aqua, January 2005

Imp

act of a

tmosp

here

Im

pa

ct of atm

osphe

re

and

surfa

ce alb

edo

and

surfa

ce alb

edo

Aq

ua, Ja

nua

ry 20

05A

qua

, Janu

ary 2

005

PPH calculationsPPH calculations

Cloud susceptibility from MODIS Level-3 daily cloud products Lazaros Oreopoulos and Steven Platnick...

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