A method for estimating sea surface nitrate concentrations from remotely sensed SST and chlorophyll a - A case study for the north Pacific Ocean using OCTS ADEOS data

We propose a method to estimate sea surface nitrate (N) from space using sa tellite measurements of sea surface temperature (SST) and chlorophyll a (ch l a), The procedure relies on empirical relationships between shipboard mea surements of N and its predictor variables, temperature (T) and chi a in su rface and hear surface waters, Although N appears to be controlled primaril y by T, the addition of the biological variable chi a. helps improve N pred iction by reducing local and regional differences in the character of the t emperature-nitrate (T-N) relationship. In the present study, we have applie d these empirical algorithms to SST and chi a data from the Ocean Color and Temperature Scanner (OCTS) on board the Advanced Earth Observation Satelli te (ADEOS). The results clearly suggest that measurements of SST and chi a now possible by modern-day ocean satellites could be exploited usefully to extend the resolution of shipboard N measurements over large spatial and te mporal scales. Systematic errors in estimates of N that could result from e rrors in satellite estimates of SST and chi a are examined through sensitiv ity analyses.