The core equation describing the relationship between surface chlorophyll and depth-integrated primary production is expressed as follows:

C_SAT

Satellite surface chlorophyll concentration as derived from measurements of water leaving radiance (mg Chl/m³). VGPM calculations of global primary production were based on monthly average C_SAT . (see: Chlorophyll dataset)

D_IRR

Daily photoperiod (in decimal hours) calculated for the middle of the month for each pixel

E₀

Sea surface daily PAR (mol quanta/m²/d)

Z_eu

Physical depth (m) of the euphotic zone defined as the penetration depth of 1% surface irradiance based on the Beer-Lambert law. Z_eu is calculated from C_SAT following Morel and Berthon (Surface pigments, algal biomass profiles, and potential production of the euphotic layer: Relationships reinvestigated in view of remote-sensing applications. Limnol. Oceanogr. 34, 1989: 1545 - 1562):

where C_TOT

P^B_Opt

Optimal rate of daily carbon fixation within a water column [mg C (mg Chl)^-1 h^-1]. P^B_Opt can be modeled according to various temperature-dependent relationships. The relationship used for most of the global production calculations was described by Behrenfeld and Falkowski (1997):

PP_eu

Daily carbon fixation integrated from the surface to Z_eu , (mg C/m²)

You can access the model source code directly or download the files via the FTP protocol. Source code is provided in IDL and Fortran:

• IDL
• FORTRAN
• ftp: anonymous@marine.rutgers.edu. If access to files is denied, please contact IMCS at vgpm@imcs.rutgers.edu. Please provide your ftp address and password to receive the files.