Ocean Color Forum
Topic Frequently Asked Questions / Data Products & Algorithms FAQ / What are the forms of the OC chlorophyll algorithms? (locked)
By houghtah Date 2008-01-18 08:55
The Ocean Color (OC) suite of chlorophyll a (Ca, mg/m3) algorithms describe the polynomial best fits that relate log-transformed Ca to log-transformed ratios of remote-sensing reflectances (Rrs, 1/sr).

Currently, all have the form:

Ca = 10^( a0 + a1*x + a2*x^2 + a3*x^3 + a4*x^4 ), where x = log10( Rrs[blue wl] / Rrs[green wl] )

The wavelengths and polynomial coefficients (a0...a4) used in operational MSl12 processing are provided below.

`name    sensor          blue wl         green wl      a0      a1      a2      a3      a4----------------------------------------------------------------------------------------OC4     SeaWiFS         443>490>510     555       0.3660,-3.0670, 1.9300, 0.6490,-1.5320OC3S    SeaWiFS         443>490         555       0.2409,-2.4768, 1.5296, 0.1061,-1.1077OC2S    SeaWiFS         490             555       0.2372,-2.4541, 1.7114,-0.3399,-2.7880OC3M    MODIS           443>488         551       0.2830,-2.7530, 1.4570, 0.6590,-1.4030OC2M    HMODIS (500-m)  469             555       0.1543,-1.9764, 1.0704,-0.2327,-1.1404OC4O    OCTS            443>490>520     565       0.4006,-3.1247, 3.1041,-1.4179,-0.3654OC3O    OCTS            443>490         565       0.2836,-2.1982, 1.0541, 0.1860,-0.7170OC2O    OCTS            490             565       0.2805,-2.1670, 1.1789,-0.1597,-1.5591OC3C    CZCS            443>520         550       0.3012,-4.4988, 9.0983,-9.9821, 3.2350`

The greatest Rrs[blue wl] is used when multiple blue wl are specified. In OC4, for example, the Rrs ratio numerator is the greatest of Rrs(443), Rrs(490), and Rrs(510).

References: