Ground truthing modeled k(PAR) and on deck primary productivity incubations with in situ observations

The Arabian Sea Process Study carried out on six cruises in 1995 provided observations that make possible the ground truthing of model estimates of k(PAR) and on deck productivity incubations with direct k(PAR) observations and in situ productivity incubations. The Morel 1988 optical model did a good job of reproducing the observed values (Obs.=0.994 Modeled+0.004; r(2)=0.75). Comparison of on deck and in situ depth profiles suggested that on deck incubators received more irradiance across the entire light gradient. This subsidy in Eo apparently came from efficient absorption of reflected light and low angle sunlight by small (30x20x20 cm) incubators. When depths were recalculated taking into account the irradiance subsidy, profiles of productivity as a function of depth determined by on deck incubations were essentially identical to in situ profiles.