1

Assessing the ‘Full Spectral’ Potential Radiative Impact of Arctic Aerosols: Dust, Smoke, Haze and Volcanic

“A PERTURBATION STUDY!”G.P. Anderson1,2 , R.S. Stone 2,3, E.P. Shettle4, E. Andrews2,3, E.G. Dutton2

1 Air Force Research Laboratory/Space Vehicles Directorate,2 NOAA Earth Systems Research Laboratory

3 Cooperative Institute for Research in Environmental Sciences, University of Colorado, 4 Navy Research Laboratory, Remote Sensing Division

2

FLEXPART CO Tracer Simulation

(A. Stohl 2006, Norwegian Institute for Air Research )Transport-only, based on mean winds from European Centre for Medium-Range Forecasts, (1x1º

resolution, 60 layers, 30 million tracer particles, 30 days)

Tracing Aerosol Sources: Smoke & Volcanic

3

MODTRAN®5 Spectroscopic Properties:Asian Dust O3 Heating & Aerosol Forcing over Barrow

R. Stonea,b, B. Andrewsa,b, J. Harrisa, E. Duttona, E. Shettlec

a = NOAA/GMD, b = CIRES, c = NRL, plus Anderson / Berk

0

20

40

60

80

-30-25-20-15-10-50

Cooling (K/day)

Alt (Km)

O3

0 5 10 15 20 25KHeating (K/day)

Atitude80 60 40 20 0

O3 Chap

Dust Layer

H2O

O2

O3 H-H

3.2 1.6 0 .8 0.4 0.2WAVELENGTH (um)

ALT

ITU

DE

.0

1

2.

2

8.

4

5.

56.

70.

8

0.

stratopause

Dust Layer

0246810

-5-4-3-2-10Cooling (K/day)

Alt (Km)

0 1 2 3 4 5K

Heating (K/day)

Atitude10 8 6 4 2 0

10

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

MODTRAN™simulationsfor Asian Dust at ?0 = 75°

Layer Heating; Surface cooling:

• increases atmospheric stability

• Suppresses cloud formation ?

(Stone et al., GRL 2007)

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo= 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

MODTRAN™simulationsfor Asian Dust at ?0 = 75°

; Surface cooling:

• increases atmospheric stability

• Suppresses cloud formation ?

(Stone et al., GRL 2007)

Layer Heating

Contour units: (K/day)/cm-1

4King et al. inversion (1978), AFRL Handbook (1986)

Fresh volcanic

~haze

MODTRAN®5 Input Requirements for Aerosol Studies:

• Aerosol Optical Properties, • Derived from size distribution, extended to LW

AOPs for Small Particles

0.0001

0.001

0.01

0.1

1

10

0.1 1 10 100 1000wavelength um

No

rm e

xt,

ab

s +

As

ym

smokehi-ext

smokehi-abs

smokehi-asym

Haze Ext.

Haze Abs.

Haze Asym.

AOPs for Large Particles

0.0001

0.001

0.01

0.1

1

10

0.1 1 10 100 1000wavelength um

Nor

m e

xt, a

bs +

Asy

m

Dust-ext

Dust-abs

dust- assym

volc_ext

volc_abs

volc_asym

Dust -asym

AOPs for Large Particles

0.0001

0.001

0.01

0.1

1

10

0.1 1 10 100 1000wavelength um

Nor

m e

xt, a

bs +

Asy

m

Dust-ext

Dust-abs

volc_ext

volc_abs

volc_asym

dust- asym

LW

SWsolar thermal

5

MODTRAN®5 Input Requirements for Aerosol Studies:

Sensitivity Study INPUT :

Barrow albedos: tundra, sea ice, snow (ref: MODTRAN)

DOY: 51 (low sun, 75°), Max AOD ~1.00Surface Albedos, 0.3-3.0µm, Emissivities, 3.0-30µm

0

0.2

0.4

0.6

0.8

1

0.1 1 10 100wavelength (um)

seaice: 0.50, 0.97

tundra: 0.120, 0.93

snow: 0.810, 0.98

SW LW

0 0.2 0.4 0.6 0.8 1

EmissivityAl

bedo

6

• Re-establish Short Wave Aerosol Impact– Heating within Aerosol Layer (2-4km)– Cooling at Surface – Evaluate the Direct Aerosol Radiative Forcing ‘At the

Surface’ ⇒ DARF• Project same Aerosols into the LW

– Establish Simple Sensitivity Study• No Feedbacks, No Chemistry, No Deposition. No Dynamics• 4 Aerosol types, 3 Arctic Surfaces, 1 solar angle (75°)

– Provide Aerosol Optical Properties• Assess Mitigation in the thermal (LW) by Aerosols

– Small ∆ thermal effect within layer (cooling)– Small ∆Heating at Surface

7

TUNDRAalbedo<0.2

SEA ICEAlbedo~0.5

SNOWalbedo~.8

75°

ALT

ITU

DE

(KM

)0

1

2

3

4

5

6

Direct Down Flux

SW Net Flux(surf) = Down (Diffuse + Direct) ⇓ – Upflux⇑

Attenuating Aerosol Layer

Diffuse Down Flux

Up-Flux ⇑ =α•⇓75° 75°

Solar heating more effective over darker surfaces!

•heats within the aerosol layer•cools the surface ∝ AOD

absorbs reflects

Aerosol Reflection

8

1. Measure NETsw radiation and AOD2. Infer size distribution from AOD(λ), via King Inversion3. Derive optical properties (AOP) using Mie Theory4. Determine Direct Aerosol Radiative Forcing (DARF) from Measurements

Model Simulations vs. Observations

Direct Aerosol Radiative Forcing = ΔNETsw AOD-1

9

50

55

65

80

60

Broadband Measurement vs. MODTRAN® Model Calculations

1. Initialize MODTRAN®; compute NET_SW FLX(AOD)2. Calculate Theoretical DARF & compare

10

Radiative Transfer Sensitivity StudyGiven CLOSURE - Design SENSITIVITY TEST

Using MODTRAN®5, ‘soda straw’ RT code• NO chemistry, • NO deposition.• NO feedbacks.

Extend to Long-Wave (LW); magnitude of mitigation?Extend to other Aerosols:

Dust, Smoke, Haze, Fresh VolcanicCONTROLS

• Maximum AOD = ~1.0• Layer confined to 2-4km (relatively insensitive)• All other parameters the same:

sonde, surface T, Io, 75° solar zenith

11

75° Model Simulations: SW

LARGE

SMALL

-40

0

40

80

120

0 0.2 0.4 0.6 0.8 1 1.2

Aerosol Optical Depth

(do

wn

-u

p)

W/m

2

(Dust, Smoke, Haze , ExtVolc) over Sea Ice, Snow, Tundra

SEA ICE

SNOW

TUNDRA

Small

Large

(Dust, Smoke, Haze, ExtVolc) over Sea Ice, Snow, Tundra

Net

Flu

x a

t S

urf

ace

LARGE

SMALL

LARGE

SMALL

-40

0

40

80

120

0 0.2 0.4 0.6 0.8 1 1.2

Aerosol Optical Depth

(do

wn

-u

p)

W/m

2

(Dust, Smoke, Haze , ExtVolc(Dust, Smoke, Haze , ExtVolc) over Sea Ice, Snow, Tundra

SEA ICE

SNOW

TUNDRA

Small

Large

(Dust, Smoke, Haze, ExtVolc) over Sea Ice, Snow, Tundra

Net

Flu

x a

t S

urf

ace

+ LW

12

Aerosol Forcing (Dust, Smoke, Haze, ExtVolc) over Sea Ice, Snow, Tundra

SENSITIVITY TEST RESULTS: 75°, 3 surfaces, 4 aerosolsDARF *

Full Spectral: SW+LW Solar Spectral: SW

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-13.0-11.0-11.0-10.0snow

-64.0-63.0-46.0-40.0Sea Ice

-96.0-94.0-75.0-70.0Tundra

-26-24-13-11snow

-79-74-48-42Sea Ice

-111-105-77-71Tundra

VolcanicDustHazeSmoke

-26-24-13-11snow

-79-74-48-42Sea Ice

-111-105-77-71Tundra

VolcanicDustHazeSmoke

1.0

LARGE LARGESMALL SMALL

>10 W~2W/m2

~10 W

~10 W

*

13

TUNDRAalbedo<0.2

SEA ICEAlbedo~0.5

SNOWalbedo~.8

75°

ALT

ITU

DE

(KM

)0

1

2

3

4

5

6

Direct Down Flux

SW Net Flux(surf) = Down (Diffuse + Direct) ⇓ – Upflux⇑

Attenuating Aerosol Layer

Diffuse Down FluxAerosol Reflection

Up-Flux ⇑ =α•⇓75° 75°

Solar heating more effective over darker surfaces!

•further cools the surface,•heats within the aerosol layer?

14

Volcanic over Tundra

Haze over Sea Ice

0 6.85K

0 3.86K

Heating Rate

Heating Rate

IntegrateHeating Rate

IntegrateHeating Rate

LW+SW

0 3.95K-0.1 0K

LW SWSWLW

NOTE: Change of Scale

0 7.49K

SW

-0.64 0K

LWLW+SW

O3O3CO2H2O

Perturbation: bkg – (bkg+haze), over Sea Ice

~3%

~10%

Heating Rate

Heating Rate

-6.9 14.5K

Heating Rate

15

BACKGROUND

Heating Rate

-14.5 6.9

Maximum Perturbation: bkg – (bkg+volcanic), over Tundra

SW-only -14.7 7.5

Dust Layer

0246810

-5-4-3-2-10Cooling (K/day)

Alt (Km)

0 1 2 3 4 5K

Heating (K/day)

Atitude10 8 6 4 2 0

10

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

MODTRAN ™ simulations

for Asian Dust at ?0 = 75 °

Layer Heating ; Surface cooling :

• increases atmospheric stability

• Suppresses cloud formation ?

(Stone et al., GRL 2007)

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 nightAOD = 0.40 day

0

1

2

3

4

5

6

-1 0 1 2 3 4

Heating (K/Day)

Altit

ude

(km

)

Heating (K/day)

Alti

tude

(km

)

Simulations for Θo = 75º

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

AOD = 0.15AOD = 0.28AOD = 0.40AOD = 0.58

Full SpectralAOD = 0.40 LWAOD = 0.40 SW+LW

MODTRAN ™ simulations

for Asian Dust at ?0 = 75 °

; Surface cooling:

• increases atmospheric stability

• Suppresses cloud formation ?

(Stone et al., GRL 2007)

Layer Heating

Heating Rate

----------++++++++++

-12.3 3.8K -12.4 3.9K

Haze overSea Ice

16

The Magnitude of Aerosol Perturbations depends upon:

1st order: SW Solar ‘heating within the aerosol layer’ and ‘cooling at the surface’ are the dominant terms.2nd order: LW ‘∆cooling within the layer’ and ‘∆heating at the surface’ are impacted by the particle size and surface type.

Surface Cooling is typically linear in AOD-1, but the radiative forcing (DARF) depends on the size of the aerosol particulates, especially at and above 1um in diameter.

Aside: In prior studies the altitude of the aerosol layer was not very relevant; however, the emissive (LW) regime would be more sensitive to hot plumes, near originating sources (volcanic or fire).

17

Direct Down Flux

TUNDRAEmissivity~.93

SEA ICEEmissivity~.97

SNOWEmissivity~.98

ALT

ITU

DE

(KM

)0

1

2

3

4

5

6

Diffuse Down Direct = 0

LW Net Flux(surf) = Down (Diffuse + Direct) ⇓ – Upflux⇑

Attenuating/Emitting Aerosol LayerNOTE: LW AOP have stronger

emission properties

Fluxo ⇑ =εo* BΣ(To)

ℜ= ΣBl δτ

εo* B (To)

18

Dust, Smoke, Haze, Volc over Sea Ice, Snow,Tundra

-90

-85

-80

-75

-70

-65

-60

0 0.2 0.4 0.6 0.8 1 1.2Aerosol Optical Depth

Net

LW

Flu

x at

Sur

face

(W/m

2)

75° Model Simulations: LW

19

DARF (Total & SW) ~ -1/albedohypothesis: high albedo leads to more multiple reflections

between surface & atmosphere, diminishing the surface cooling

Dust, Smoke, Haze, ExtVolc2 75o Solar Incidence

y = 124.18x - 124.75

y = 91.015x - 83.001

y = 0.9085x + 10.243y = 0.067x + 1.0938

-120

-100

-80

-60

-40

-20

0

20

0 0.2 0.4 0.6 0.8 1

(Io*albedo)/Io

Aero

sol-I

nduc

ed H

eatin

g (W

/m2)

day full calcniteday full calcniteLinear (day )Linear (day )Linear (nite)Linear (nite)

Sea iceSnowTundra

SMALL

LARGE

SW

AEROSOL-INDUCED SURFACE COOLING

LW