Sea salt aerosols: Their generation and role in the climate system Ph. D. Dissertation Proposal Magdalena D. Anguelova November 12, 1999 College of Marine Studies University of Delaware

Outline What? n Problem statement How? n Implementation Why? n Implications

Problem statement n Modify the currently available sea-salt generation function. n Evaluate the effect of sea-salt aerosols on the climate system.

The Role of the Aerosols n In climate: n n In atmospheric chemistry: n n Scatter sunlight; n n Facilitate cloud droplet formation; n n Provide site for chemical reactions.

“...However, it generates too much big sea-salt particles at high wind speeds compared to observations and is therefore neglected in the simulation.” “... However, it generates too much big sea-salt particles at high wind speeds compared to observations and is therefore neglected in the simulation.” Aerosols in Climate Models n Improves model predictions; n Canadian Climate Model (Gong, Barrie, Blanchet, 1997) n n Use the first sea-salt generation function (Monahan et al., 1986)

Sea Spray Formation n n Direct; n n Indirect. Andreas et al., 1995

Sea Spray Sizes r,  m Film drops: 0.5 to 5  m Jet drops: 3 to 50  m Spume drops: 20 to > 500  m Andreas, 1998

Sizes Relevant to Aerosol Forcing n Long residence time. n n Gravitational settling. Heat exchangeAerosol forcing r,  m

Modeling Sea Spray dF/dr = dF 0 /dr + dF 1 /dr Monahan et al., 1986 r,  m

Modeling the Indirect Mechanism d F 0 /d r = U r -3 ( r 1.05 ) e -B2-B2 B = ( log r) / 0.65 Monahan et al., 1986 d F 0 /d r = f (U 10, r) Whitecap coverage W

Modeling the Direct Mechanism d F 1 /d r = C 1 (U 10 ) r  m  r  37.5  m d F 1 /d r = C 2 (U 10 ) r  m  r  100  m Andreas, 1998 d F 1 /d r = f (U 10, r) Coefficients C i

The Goal d F 0 /d r d F /d r = f (U 10, r) f (U 10,  T, T s, S, f, d, C, r) ? W (U 10,  T, T s, S, f, d, C) d F 1 /d r C i (U 10,  T, T s, S, f, d, C) Method

TsTs The Concept e - e s e f - e s W = eT s =CalculatedObserved TBTB = e s (1-W )T s + W e f T s B A

The Procedure n Data n Compute W n n Preparation n n Brightness temperature; n n Wind mask; n n Cloud mask; n n Rain mask; n n Available T s ; n n Calculate e; n n Calculate e s ; n n Calculate e f ; n n Calculate W. e eses eses n n Salinity; n n Sea surface temperature;

Brightness Temperature T B (h), K March 27, 1998Ascending pass SSM/I 19 GHz Grid: 0.5 o  0.5 o Data

Sea Surface Temperature T s, o C AVHRR Data

Wind Mask U 10, m s -1 U 10 > 10 m s -1 Preparation

Cloud Mask L, mg cm -2 L < 5 mg cm -2 Preparation

Rain Mask T B (h), K T B (37v) - T B (37h) > 50 and T B (19h) < T K 165 K 175 K Preparation

All Masks on T B T B (h), K e Preparation

All Masks on SST T s, o C eses Preparation

Available T B T B (h), K Preparation

Emissivity of Sea Water e (h) 0.29 to 0.45 Results

Specular Emissivity e s (h) 0.26 to 0.28 e Results

Emissivity of Foam e f (h) 0.91 to 0.94 e eses Results

Whitecap Coverage W (h) Results

Comparison W (h) e - e s e f - e s W = W = 3.84  U 10 Conventional MethodProposed Method 4% - 30% 1% - 19%

Questions The Boasting Traveller, Aesop "Deeds speak louder than words"