AN EVALUATION OF THE NATIONAL METEOROLOGICAL CENTER WEEKLY HINDCAST OF UPPER-OCEAN TEMPERATURE ALONG THE EASTERN PACIFIC EQUATOR IN JANUARY1992

The upper-ocean temperature distribution along the Pacific equator fro m 139-degrees to 103-degrees-W was observed in January 1992 with tempe rature profiles recorded from a ship and inferred from an ocean genera l circulation model calculation involving data assimilation (i.e., hin dcast). An El Nino episode was in progress. The 100-m-thick mixed laye r depth, the mixed-layer temperature, and the depth-averaged temperatu re below the thermocline were similar in both data products. Considera ble differences occurred in the representation of the 15-degrees-25-de grees-C thermocline, such as the depth-averaged temperatures above and below the 20-degrees-C isotherm, the east-west slope of the 20-degree s-C isotherm, and a 1000-km-wide depression. The longitudinal-averaged root-mean-square difference between the hindcast and observed depths of the center of the thermocline was 17 m. Most of the disparities cou ld be attributed to a high wavenumber transient event that the model-b ased assimilation system was not intended to resolve.