sea salt aerosols: their generation and role in the climate system
DESCRIPTION
Sea salt aerosols: Their generation and role in the climate system. Ph. D. Dissertation Proposal Magdalena D. Anguelova. College of Marine Studies University of Delaware. November 12, 1999. Outline. What?. Problem statement. Why?. Implications. Implementation. How?. - PowerPoint PPT PresentationTRANSCRIPT
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Sea salt aerosols: Their generation
and role in the climate system
Ph. D. Dissertation Proposal
Magdalena D. Anguelova
November 12, 1999College of Marine Studies
University of Delaware
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Outline
What? Problem statement
How? ImplementationImplementation
Why? ImplicationsImplications
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Problem statement
Modify the currently available sea-salt generation function.
Evaluate the effect of sea-salt aerosols on the climate system.
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The Role of the Aerosols
In climate:
In atmospheric chemistry:
Scatter sunlight; Facilitate cloud
droplet formation;
Provide site for chemical reactions.
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““...... However, it generates too much big sea-salt particles However, it generates too much big sea-salt particles at high wind speeds compared to observations and is at high wind speeds compared to observations and is therefore neglected in the simulation.”therefore neglected in the simulation.”
Aerosols in Climate Models
Improves model predictions; Canadian Climate Model
(Gong, Barrie, Blanchet, 1997) Use the first sea-salt generation function
(Monahan et al., 1986)
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Sea Spray Formation
Direct; Indirect.
Andreas et al., 1995
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Sea Spray Sizes
r, m5001001010.1
Film drops: 0.5 to 5 m
Jet drops: 3 to 50 m
Spume drops: 20 to > 500 m
Andreas, 1998
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Sizes Relevant to Aerosol Forcing
Long residence time.
Gravitational settling.
Heat exchangeAerosol forcing
r, m5001001010.1
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Modeling Sea Spray
dF/dr = dF0 /dr + dF1 /drMonahan et al., 1986
r, m5001001010.1 0.8
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Modeling the Indirect Mechanism
d F0 /d r = 1.373 U103.41 r -3(1 + 0.057r1.05) 101.19e -B2
B = (0.38 - log r) / 0.65Monahan et al., 1986
d F0 /d r = f (U10 , r)
Whitecap coverage W
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Modeling the Direct Mechanism
d F1 /d r = C1 (U10) r -1 10 m r 37.5 m
d F1 /d r = C2 (U10) r -2.8 37.5 m r 100 m
Andreas, 1998
d F1 /d r = f (U10 , r)
Coefficients Ci
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The Goal
d F0 /d r
d F /d r = f (U10 , r)
f (U10 , T, Ts , S, f , d , C, r)
??W (U10 , T, Ts , S, f , d , C)
d F1 /d r
Ci (U10 , T, Ts , S, f , d , C) Method Method
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Ts
The Concept e - es ef - es
W =
eTs =
CalculatedCalculatedObservedObserved
TB= es (1-W )Ts + W ef Ts
BA
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The Procedure
Data Compute W Preparation
Brightness temperature;
Wind mask; Cloud mask; Rain mask; Available Ts;
Calculate e; Calculate es;
Calculate ef ; Calculate W.
e
es
es Salinity;
Sea surface temperature;
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Brightness Temperature
TB (h), K
March 27, 1998 Ascending pass SSM/I19 GHz
Grid: 0.5o 0.5o
DataData
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Sea Surface Temperature
Ts , oC
AVHRRAVHRR
DataData
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Wind Mask
U10 , m s-1
U10 > 10 m s-1
PreparationPreparation
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Cloud Mask
L , mg cm-2
L < 5 mg cm-2
PreparationPreparation
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Rain Mask
TB (h), K
TB (37v) - TB (37h) > 50 and
TB (19h) < T1
130 K
165 K
165 K
175 K
PreparationPreparation
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All Masks on TB
TB (h), K
e
PreparationPreparation
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All Masks on SST
Ts , oC
es
PreparationPreparation
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Available TB
TB (h), K
PreparationPreparation
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Emissivity of Sea Water
e (h)0.29 to 0.45
Results
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Specular Emissivity
es (h)0.26 to 0.28
e
Results
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Emissivity of Foam
ef (h)0.91 to 0.94
ees
Results
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Whitecap Coverage
W (h)
Results
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Comparison
W (h)
e - es ef - es
W =
W = 3.8410-6 U10
Conventional Method
Proposed Method
4% - 30%4% - 30%
1% - 19%1% - 19%
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Questions
The Boasting Traveller, Aesop
"Deeds speak louder than
words"