1. Magdalena D. Anguelova, Ferris Webster, Peter Gaiser 12 May, 2004 Effects of Environmental Variables in Sea Spray Generation Function via Whitecap Coverage Remote Sensing Physics Branch Naval Research Laboratory Washington, DC Workshop: Toward a Universal Sea Spray Source Function Skipton, UK, 11-13 May, 2004

2. Sea Spray Workshop, May 2004 OutlineOutline Motivation and objectives; Whitecap coverage estimation; Generation of sea spray; Summary and future work.

3. Sea Spray Workshop, May 2004 Sea Spray and Climate Heat exchange; Gas exchange; Sea-salt aerosols: Direct effect – cooling; Indirect effect: Dominate the activation of CCN; Compete with SO 4 2- aerosols; Halogen chemistry: Reactive Cl and Br; Tropospheric O 3 ; Sink of S.

4. Sea Spray Workshop, May 2004 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 Explicit forms for 4 size regions covering 1.6 to 500  m range. Andreas (2001) (Monahan and O’Muircheartaigh, 1980)

5. Sea Spray Workshop, May 2004 Sea-salt concentrations High variability of C(U 10 ) : r 2 = 0.14 to 0.91 Exton et al., 1985 Hoppel et al.,1989 Gong et al., 1997 Quinn & Coffman, 1999 Due to: Either processes in the atmosphere: Transport: Mixing; Advection; Deposition; Chemistry: Particle-to-particle conversions; In cloud processing; Or…

6. Sea Spray Workshop, May 2004 Source function variability

7. Sea Spray Workshop, May 2004 Source function variability

8. Sea Spray Workshop, May 2004 Additional factors Introduce: Meteorological conditions; Environmental factors; W(U 10,  T, T s, S, f, d, C ) (Monahan and O’Muircheartaigh, 1986) ), C ),  T, T s, S, f, d, C ), C ), Ts, Ts, S, S, f, d, d Need of data base; Existing measurements.

9. Sea Spray Workshop, May 2004  Open ocean?                  

10. Sea Spray Workshop, May 2004 Range of conditions 307 points 477 points

11. Sea Spray Workshop, May 2004 Subjective analysis Intensity threshold; A and B stages in oblique view High uncertainty: Up to 30%; Higher Stramska and Petelski, 2003

12. Sea Spray Workshop, May 2004 Alternative approach Open ocean conditions; Range of conditions; Subjective analysis.

13. Sea Spray Workshop, May 2004 OutlineOutline Motivation and objectives; Whitecap coverage estimation; Generation of sea spray; Summary and future work.

14. Sea Spray Workshop, May 2004 Whitecaps signature High Reflectivity High Emissivity Reflectivity Emissivity Vis IRmWUV TBTB

15. Sea Spray Workshop, May 2004 Ocean emissivity is composite e Method concept e  as W  Emissivity of foam-free ocean is low. Emissivity of foam-covered ocean is high. e – e s –  e r e f – e s –  e r W = = (e s +  e r )(1-W ) + W e f

16. Sea Spray Workshop, May 2004 Calculate emissivities Composite emissivity e : Specular emissivity e s : Foam emissivity e f : Roughness correction  e r : Radiative transfer equation Fresnel formula, Debye equation Fresnel formula, empirical relation Empirical relation T B, V, L T s, S U 10, T s SSM/I AVHRR NOAA SSM/I AVHRR

17. Sea Spray Workshop, May 2004 Whitecap coverage 27 March 1998

18. Sea Spray Workshop, May 2004 AccuracyAccuracy Relative error,  W /W (%) Count

19. Sea Spray Workshop, May 2004 Validation with previous data

20. Sea Spray Workshop, May 2004 Magnitude; Trend: Suppression at high winds; Enhancement at moderate winds. Variability! Validation with previous data

21. Sea Spray Workshop, May 2004 Spatial distribution Same magnitude; Different spatial features: More uniform; 3% instead of 1%. March 1998 W  U 10 3

22. Sea Spray Workshop, May 2004 Effects of additional factors Wind speed, U 10 (m s -1 ) Sea surface temperature, T s ( o C) Wind fetch and duration; Surface-active material. March 1998

23. Sea Spray Workshop, May 2004 OutlineOutline Motivation and objectives; Whitecap coverage estimation; Generation of sea spray; Summary and future work.

24. Sea Spray Workshop, May 2004 Modified source function Use new global estimates for f(U 10 ) ; Chose size dependence f(r). W(U 10 ) (Monahan and O’Muircheartaigh, 1986) W(U 10,  T, T s, S, f, d, C )

25. Sea Spray Workshop, May 2004 Modified source function    Assimilating new method estimates    Andreas, 2002 Monahan et al., 1986 Future work mm mm mm

26. Sea Spray Workshop, May 2004 New method Wind formula Function performance Current function (Andreas, 2002) Measurements (Smith et al., 1993)

27. Sea Spray Workshop, May 2004 Sea-salt aerosol loading Magnitude; Weak wind dependence; T s in places with U 10 = 10 m s -1 Sea surface temperature, T s o C T s in places with U 10 = 15 m s -1

28. Sea Spray Workshop, May 2004 Sea spray spatial distribution 1  10 5 4  10 5 7  10 5 1  10 6 Number flux, dF/dr 0 (#  m -1 m -2 s -1 ) Haywood et al., 1999 Model - Experiment

29. Sea Spray Workshop, May 2004 OutlineOutline Motivation and objectives; Whitecap coverage estimation; Generation of sea spray; Summary and future work.

30. Sea Spray Workshop, May 2004 SummarySummary Variability of sea spray source function due to environmental factors; Whitecap coverage can account for them; Alternative approach for global whitecap coverage; Modification of sea spray source function.

31. Sea Spray Workshop, May 2004 Future work Improvements in whitecap coverage estimates: e s – all available models considered and compared;  e r – 2-scale model; e f – full RT model for a foam layer with void fraction changing with depth; e – decoupling of satellite measurements; Parameterizations: Initial steps for W(U 10, T s ) encouraging; Identify more suitable methods and functions fitting highly variable data; Revise W(U 10, T s ); Investigate correlations W(S), W(f), W(d), W©.

32. Sea Spray Workshop, May 2004