Thermal calibration of satellite infrared images and correlation with sea-surface nutrient distribution.

Abstract

Satellite infrared imagery off the California coast, near Pt. Sur, show thermal patterns associated with an upwelling center; the patterns frequently curl cyclonically when inter- acting with the warmer California Current. This pattern shows sharp thermal fronts, easily identified in satellite IR images, that are strongly correlated with nutrient fronts during the early stages of upwelling. With sea truth data available, it was feasible to calibrate satellite derived sea surface temperature, by applying radiative transfer theory, and to infer nutrient concentrations from their linear inverse correlations with temperature. Thus, it was possible to calibrate satellite thermal fields to produce maps of nutrient distributions. When the inferred relationships were applied over representative regions of the upwelling center, standard deviations of 0.5°C, 1.7 uM and 0.1 uM were computed for temperature, nitrate and phosphate, respectively.