Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation...

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Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of Delaware June 17-21, 2002 Breckenridge, Colorado

Transcript of Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation...

Page 1: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Whitecaps, sea-salt aerosols, and climate

Magdalena D. Anguelova

Physical Oceanography

Dissertation Symposium

College of Marine Studies, University of Delaware

June 17-21, 2002Breckenridge, Colorado

Page 2: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

What?

Outline

How?

Why?

Work

Background

Results

Page 3: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Aerosol effects

IPCC, 2001

Page 4: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Assessment: Effect of anthropogenic aerosols = Effect of all aerosols – Effect of natural aerosols

Aerosol radiative forcing Defined as…

natural

Page 5: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Background atmosphere Natural aerosols; Baseline of an unperturbed

atmosphere.

Page 6: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Background baseline

Sea-salt aerosols are the dominant aerosol species in background

atmosphere.

Sea-salt aerosols

Natural aerosols; Baseline of an unperturbed

atmosphere.

Page 7: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Formation of sea-salt aerosols

Sea spray;

Droplet sizes:• 0.5-500 m;• < 20 m;

Sea-salt aerosols:• Phase state;• Sizes: 0.025 to 20 m.

Page 8: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Sea-salt aerosol effects must be accounted for in climate models.

Motivation

Page 9: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Modeling sea-salt aerosols

Generation; Transport; Diffusion and convection; Chemical and physical

transformations:• in clear air;• in clouds;• below clouds;

Wet and dry deposition.

Generation

Page 10: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Rate of production of sea spray per unit area per increment of droplet radius, r (s-1 m-2 m-

1).

Sea spray generation function

dr

dF

dr

dfrf )( Explicit forms for 4 size regions

covering 1.6 to 500 m range. Andreas (2001)

41.310

61010 108.3)()( UUWUf (Monahan and

O’Muircheartaigh, 1980)

Best)()( 10 rfUf

Page 11: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Improved generation function?

)()( 10 rfUfdr

dF

r0 1.6 mMeasurements

0.1

W(U10, T, Ts , S, f , d , C )

(Monahan and O’Muircheartaigh, 1986)

) , C ), T, Ts , S , f , d , C ), Ts , S , f , d

Whitecap coverage

Page 12: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Need for a database

W (U10 , T, Ts , S, f , d , C )

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

1

2

3

45 6

7

9

1011

1213

14

1516

Page 13: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Need of a database

W (U10 , T, Ts , S, f , d , C )

1

2

3

45 6

7

9

1011

1213

14

1516

307 points477 points

New meth

od

Page 14: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Outline

Work

Background

Results

Page 15: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Ocean emissivity is compositee

Method concept

e as W Emissivity of foam-free ocean is low.

Emissivity of foam-covered ocean is high.

e – es – er ef – es – er

W == (es + er)(1-W ) + W ef

Page 16: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

The task: calculate emissivities

Composite emissivity e:

Specular emissivity es:

Foam emissivity ef :

Roughness correction er:

Radiative transfer equation

Fresnel formula, Debye equation

Fresnel formula, empirical relation

Empirical relation

TB, V, L

Ts, S

Ts, S

U10, Ts

SSM/I

AVHRRNOAA

SSM/IAVHRR

Page 17: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Valid estimation of W

rsf

rs

eee

eeeW

W < 0

e < es + er

Brightness Temperature, TB (K)

100 120 140 160 180

Whi

teca

p co

vera

ge, W

(%

)

0

10

20

30

40

50

L = 0 mmS = 35 psuTs = 20 oCQ = 2 %U10 = 9 m s-1

V mm

8

20

35

50

Brightness Temperature, TB (K)

100 120 140 160 180

Whi

teca

p co

vera

ge, W

(%

)

0

10

20

30

40

50

L = 0 mmS = 35 psuTs = 20 oCQ = 2 %U10 = 9 m s-1

V mm

8

20

35

50

Brightness Temperature, TB (K)

100 120 140 160 180

Whi

teca

p co

vera

ge, W

(%

)

0

10

20

30

40

50

L = 0 mmS = 35 psuTs = 20 oCQ = 2 %U10 = 9 m s-1

V mm

8

20

35

50

Brightness Temperature, TB (K)

100 120 140 160 180

Whi

teca

p co

vera

ge, W

(%

)

0

10

20

30

40

50

L = 0 mmS = 35 psuTs = 20 oCQ = 2 %U10 = 9 m s-1

V mm

8

20

35

50

2 – 10 %

Page 18: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Error of W

Page 19: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Method accuracy

0 10 20 30 40 50 60 70 80 90 1000

40

80

120

160

200

240

280

320

Relative error of W

Cou

nt

Relative error, W/W (%)

Cou

nt

Page 20: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itu

de

0.00 0.02 0.04 0.06 0.08 0.10

Whitecap coverage, W

Whitecap coverage27 March

1998

Page 21: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Validation with in situ data

Page 22: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Validation with in situ data

Magnitude; Trend:

• Suppression at high winds;

• Enhancement at moderate winds.

Variability!

Page 23: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Outline

Work

Background

Results

Page 24: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Database

Use:• Investigate spatial and temporal

characteristics of global whitecap coverage;

• Evaluate whitecap contribution to climate processes.

• Parameterize effects of additional factors on whitecaps;

Content:• Daily and monthly estimates of W and W

for the entire 1998;• Collocated measurements of U10, Ts, S;

Page 25: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Spatial distribution Same magnitude; Different spatial

features:• More uniform;• 3% instead of 1%.

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itu

de

0.00 0.02 0.04 0.06 0.08 0.10

Whitecap coverage, W

March 1998 W U10

3

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itu

de

0.00 0.02 0.04 0.06 0.08 0.10

Whitecap coverage, W

Page 26: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itu

de

0.00 0.02 0.04 0.06 0.08 0.10

Whitecap coverage, W

Effects of additional factors

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

-3 0 3 6 9 12 15 18 21 24 27 30 33

Wind speed, U10 (m s-1)

Sea surface temperature, Ts (oC)

Wind fetch and duration; Surface-active material.

March 1998

Page 27: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Ocean surface albedo Natural

climate agent; Average:

0.11 W m-2;

Anthropogenic agents:

•Stratospheric ozone (0.18 W m-2)

•Biomass burning (0.21 W m-2)

•Land use (0.22 W m-2)

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itud

e

0.00 0.04 0.08 0.12 0.16 0.20

Radiative flux changes, F (W m‑2)

Page 28: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

CO2 transfer velocity

5 – 150 cm h-1; Average:

56.8 cm h-1; Tropics are

source of CO2; Southern

Ocean is sink of CO2.

CO2 transfer velocity, kCO2 (cm h‑2)

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itud

e

0 30 60 90 120 150

Flux = kCO2 C

Page 29: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Improved generation function?

)()(),(

1010 rfUf

dr

UrdF

r0 1.6 mMeasurements

0.1

W(U10)

(Monahan and O’Muircheartaigh, 1986)

W(U10, T, Ts , S, f , d , C )

Page 30: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Modified generation function

1010

0

),,,,,,(

dr

dfCdfSTTUW

dr

dFs 206.1 0 r

2010

0

),,,,,,(

dr

dfCdfSTTUW

dr

dFs 6.14.0 0 r

3010

0

),,,,,,(

dr

dfCdfSTTUW

dr

dFs 4.01.0 0 r

Assimilating new method estimates

Andreas, 2001

Monahan et al., 1986

Future work

m

m

m

Page 31: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Sea-salt aerosol loading

Magnitude; Weak wind dependence;

5.0 10.0 15.0 20.0 25.0 30.0

0

50

100

150

200

250

300

Cou

nt

Ts in places with

U10 = 10 m s-1

Sea surface temperature, Ts oC 5.0 10.0 15.0 20.0 25.0 30.0

0

50

100

150

Cou

nt

Ts in places with

U10 = 15 m s-1

Page 32: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Haywood et al., 1999Model - Experiment

Spatial distribution of sea-salt

-180 -120 -60 0 60 120 180

90

60

30

0

-30

-60

-90

Longitude

Lat

itud

e

1.0e+005 4.0e+005 7.0e+005 1.0e+0061105 4105 7105 1106

Number flux, dF/dr0 (# m-1 m-2 s-1)

Direct effect: 15 W m-2

Page 33: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.

Conclusions

Whitecap coverage estimation

Whitecap coverage database

Generation of sea-salt aerosols

Page 34: Whitecaps, sea-salt aerosols, and climate Magdalena D. Anguelova Physical Oceanography Dissertation Symposium College of Marine Studies, University of.