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 USA Santa Fe, New Mexico November 21, 2002 This work was supported by a NASA MODIS Team contract (NAS ) and NASA grant (NAG5-6289).

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. L w (443):L w (550) R(490):R(555) max[R(443),R(490)]:R(555) max[R(443),R(490),R(510)]:R(555) CZCS OC2 OC3M OC4

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 Garver & Siegel, 1997 Carder et al. 1999

In this presentation, I will…. 1.Demonstrate this by comparing Garver & Siegel (1997) algorithm OC4 algorithm (O’Reilly et al. 2000) 2.Show that covariance among optically active constituents reconciles this inconsistency.

Ratio algorithms are strongly supported by empirical data….

Chl = Isopleths of chlorophyll for the OC4 algorithm

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

bbp=b bp (555) adm=a cdm (443) Chl R rs (555) max. R rs ( ) 3-D “constituent space” maps into 2-D reflectance plane

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

Measured Chl SeaBAM Data

Chl = , 30 Maximum reflectance Isopleths of Chl in the OC4 plane, holding %adm = 35% bbp isopleths

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

%adm = OC4 Chl = 0.3 isopleths varying %adm between 0 and 90% Tracing points along the OC4 Chl = 0.3 isopleth, adm increases as bbp decreases.

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

Chl = 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.

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

Measured Chl SeaBAM Data

Chl < 0.05 Chl = 0.1 Chl = 1 Chl = 10

CONCLUSIONS 1.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. 2.Empirical evidence supports ratio algorithms in which Chl isopleths do pass through the origin. 3.Covariance between adm and bbp reconciles this discrepancy.

CONCLUSIONS (cont.) 4.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. 5.This might contain a clue as to the nature of the particles that scatter light in the different ocean environments.

NOMAD Data

Measured Chl SeaBAM Data