1. ISOPLETHS OF CHLOROPHYLL IN RADIANCE SPACE Janet W. Campbell, Timothy S. Moore, and Mark D. Dowell Ocean Process Analysis Laboratory University of New Hampshire Durham, NH 03824-3525 USA Santa Fe, New Mexico November 21, 2002 This work was supported by a NASA MODIS Team contract (NAS5-96063) and NASA grant (NAG5-6289).

2. According to a ratio algorithm…. Isopleths of chlorophyll are lines passing through the origin in the plane defined by the two radiances used in the ratio. • CZCS • OC2 • OC3M • OC4 • Lw(443):Lw(550) • R(490):R(555) • max[R(443),R(490)]:R(555) • max[R(443),R(490),R(510)]:R(555)

3. According to a semi-analytic algorithm … Isopleths of chlorophyll generally do not pass through the origin in planes defined by two radiances. • Gordon et al. 1988 • Garver & Siegel, 1997 • Carder et al. 1999

4. In this presentation, I will…. • Demonstrate this by comparing • Garver & Siegel (1997) algorithm • OC4 algorithm (O’Reilly et al. 2000) • Show that covariance among optically active constituents reconciles this inconsistency.

5. Ratio algorithms are strongly supported by empirical data….

6. Chl = 0.01 0.1 0.3 1 3 10 30 Isopleths of chlorophyll for the OC4 algorithm

7. Semi-analytic Model of Garver & Siegel, 1997 l b ( ) b l R ( ) ~ Gordon et al. 1988 rs l + l a ( ) b ( ) b Pope & Fry, 1997 Bricaud et al. 1995 S = 0.02 p = 1

8. 3-D “constituent space” maps into 2-D reflectance plane bbp=bbp(555) max. Rrs(l) Chl Rrs(555) adm=acdm(443)

9. p=2 to 0 Chl = 0 %adm = 0 Pure Seawater bbp = 0 Chl = 10 mg m-3 %adm = 80% Feasible Points in 490 vs. 555 Reflectance Plane

10. Measured Chl SeaBAM Data

11. Chl = 0.01 0.1 0.3 1 3 10, 30 Maximum reflectance bbp isopleths Isopleths of Chl in the OC4 plane, holding %adm = 35%

12. bbp isopleths Chl = 0.3 isopleths varying %adm between 0 and 90%

13. %adm = 0 10 35 50 65 80 90 Chl = 0.3 isopleths varying %adm between 0 and 90% Tracing points along the OC4 Chl = 0.3 isopleth, adm increases as bbp decreases. OC4

14. Chl = 0 Chl = 0.1 Chl = 1 %adm = 0% 10% 50%10% 75% 30% Chl = 10 90% SeaBAM data for Chl = 0.1, 1 and 10

15. Chl = 0.01 0.1 0.3 1 3 10 30 Isopleths of chlorophyll for the OC4 algorithm The Garver&Siegel model was inverted to derive the relationship between adm and bbp along the OC4 isopleths of Chl.

16. Relationship between adm and bbp required to reconcile OC4 and Garver&Siegel model

17. Measured Chl SeaBAM Data

18. Chl < 0.05Chl = 0.1Chl = 1Chl = 10

19. CONCLUSIONS • According to semi-analytic models for Case 1 waters, optical properties are governed by three variables (Chl, adm, bbp). Chl isopleths in radiance space do not pass through the origin. • Empirical evidence supports ratio algorithms in which Chlisopleths do pass through the origin. • Covariance between adm and bbp reconciles this discrepancy.

20. CONCLUSIONS (cont.) • The nature of the relationship between adm and bbp depends on the trophic state: • In oligotrophic waters, there is a negative correlation between adm and bbp. • In eutrophic waters, the correlation is zero or positive. • This might contain a clue as to the nature of the particles that scatter light in the different ocean environments.

21. NOMAD Data

22. Measured Chl SeaBAM Data