A comparison of the SeaWiFS chlorophyll and CZCS pigment algorithms using optical data from the 1992 JGOFS Equatorial Pacific Time Series

Abstract

Optical data were collected during two U.S. JGOFS EgPac Time Series cruises aboard the U.S. Research Vessel Thomas G. Thompson, at a station at 140°W on the equator, during the time of both the first equinox and the second equinox of 1992. This data set represents the range of conditions expected in this region, and was used to compare the SeaWiFS chlorophyll a algorithm with the CZCS pigment algorithm, as well as test the validity of using ocean color remote sensing to track the biological response to physical phenomena such as Kelvin Waves and Tropical Instability Waves (TIW). Time Series 1(23 March to 9 April) took place during the maximum expression of the 1991–1992 El Nin˜o event, and coincided with the peak of a passing Kelvin wave. Time Series II (2–21 October) occurred during La Nina conditions and encompassed the passage of a TIW. The SeaWiFS pigment compared favorably with the earlier CZCS pigment algorithm and indicate that the SeaWiFS algorithm is capable of determining both quantitative and qualitative changes in surface chlorophyll a from remotely sensed optical data in high nutrient, low chlorophyll regions such as the Equatorial Pacific. Our results show that, although Kelvin waves can not be currently tracked using ocean color sensors alone, when a Kelvin wave is detected by other methods, satellite ocean color data can be used to characterize the biological response to the Kelvin wave. However, since TIWs have a much shorter period and can enhance near-surface phytoplankton growth rates quickly, they can be tracked using remotely sensed ocean color data using either the CZCS pigment or the SeaWiFS chlorophyll algorithm.