1 / 34

Whitecaps, sea-salt aerosols, and climate

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

woody
Download Presentation

Whitecaps, sea-salt aerosols, and climate

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. Outline • Background Why? How? • Work • Results What?

  3. Aerosol effects IPCC, 2001

  4. Aerosol radiative forcing • Defined as… • Assessment: Effect of anthropogenic aerosols = • Effect of all aerosols – Effect of natural aerosols natural

  5. Natural aerosols; Baseline of an unperturbed atmosphere. Background atmosphere

  6. Background baseline • Natural aerosols; • Baseline of an unperturbed atmosphere. Sea-salt aerosols Sea-salt aerosols are the dominant aerosol species in background atmosphere.

  7. 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.

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

  9. Modeling sea-salt aerosols Generation • Generation; • Transport; • Diffusion and convection; • Chemical and physical transformations: • in clear air; • in clouds; • below clouds; • Wet and dry deposition.

  10. (Monahan and O’Muircheartaigh, 1980) Explicit forms for 4 size regions covering 1.6 to 500 m range. Andreas (2001) Sea spray generation function Rate of production of sea spray per unit area per increment of droplet radius, r (s-1 m-2m-1). Best

  11. r0 1.6 m Measurements (Monahan and O’Muircheartaigh, 1986) W(U10, T, Ts , S, f , d , C) ) ,Ts ,f ,C) ,S ,d Improved generation function? 0.1 , Ts , f , C) , T , S , d Whitecap coverage

  12. Need for a database W (U10 , T, Ts , S, f , d , C) 10 2 16 11 15 12 4 13 7 6 5 1 3 9 14

  13. 307 points 477 points Need of a database W (U10 , T, Ts , S, f , d , C) New method 10 2 16 11 15 12 4 13 7 6 5 1 3 9 14

  14. Outline • Background • Work • Results

  15. Emissivity of foam-free ocean is low. e – es – er W = ef – es – er Method concept e  as W  • Emissivity of foam-covered ocean is high. • Ocean emissivity is composite e = (es + er)(1-W ) + W ef

  16. TB, V, L SSM/I Radiative transfer equation AVHRR NOAA Ts, S Fresnel formula, Debye equation Ts, S Fresnel formula, empirical relation SSM/I AVHRR U10, Ts Empirical relation The task: calculate emissivities • Composite emissivity e: • Specular emissivity es: • Foam emissivity ef : • Roughness correction Der:

  17. Valid estimation of W e < es + er W < 0 2 – 10 %

  18. Error of W

  19. Method accuracy Count Relative error, W/W (%)

  20. Whitecap coverage 27 March 1998

  21. Validation with in situ data

  22. Validation with in situ data • Magnitude; • Trend: • Suppression at high winds; • Enhancement at moderate winds. • Variability!

  23. Outline • Background • Work • Results

  24. Database • Content: • Daily and monthly estimates of W and W for the entire 1998; • Collocated measurements of U10, Ts, S; Use: • Investigate spatial and temporal characteristics of global whitecap coverage; • Evaluate whitecap contribution to climate processes. • Parameterize effects of additional factors on whitecaps;

  25. Same magnitude; Different spatial features: More uniform; 3% instead of 1%. • W U103 Spatial distribution March 1998

  26. Wind speed,U10 (m s-1) Sea surface temperature,Ts(oC) Effects of additional factors March 1998 • Wind fetch and duration; • Surface-active material.

  27. Natural climate agent; Average: 0.11 W m-2; Ocean surface albedo • Anthropogenic agents: • Stratospheric ozone (0.18 W m-2) • Biomass burning (0.21 W m-2) • Land use (0.22 W m-2) Radiative flux changes, F (W m‑2)

  28. 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 Flux = kCO2C CO2 transfer velocity, kCO2 (cm h‑2)

  29. Improved generation function? r0 1.6 m 0.1 Measurements (Monahan and O’Muircheartaigh, 1986) W(U10, T, Ts , S, f , d , C) W(U10)

  30. Modified generation function   m Andreas, 2001   m Monahan et al., 1986   m Future work Assimilating new method estimates

  31. Ts in places with U10 = 10 m s-1 Ts in places with U10 = 15 m s-1 Sea surface temperature, TsoC Sea-salt aerosol loading • Magnitude; • Weak wind dependence;

  32. Haywood et al., 1999 Model - Experiment Spatial distribution of sea-salt 1105410571051106 Number flux, dF/dr0 (# m-1 m-2 s-1) Direct effect: 15 W m-2

  33. Conclusions • Whitecap coverage estimation • Whitecap coverage database • Generation of sea-salt aerosols

  34. ????? ?????

More Related