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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