A principal component analysis of sea-surface temperature in the Arabian Sea

Spatial and temporal variability in sea-surface temperature (SST) is analyz ed by the method of principal component analysis (PCA). Variability of sate llite-derived SST from the NOAA/NASA Advanced Very High Resolution Radiomet er (AVHRR) Pathfinder data over the Arabian Sea is compared to the PCA of t he mixed-layer temperature fields from two different Indian Ocean models. C limatological model output is compared to Pathfinder's "averaged" year usin g data from 1987 to 1990. A 5-year analysis with data and model output (fro m 1985 to 1989) is also done. The first mode in all the studies accounts fo r 58.2-95.8% of the SST variability, and is identified with the seasonal wa rming and cooling associated with the Indian Monsoon. The second mode accou nts for 20.6-31.1% and corresponds to the radiative heating of the basin. T ime series of the basin's mean SST shows that the models lag Pathfinder SST by approximately one month. The climatological models fail to reproduce th e SST variability, in both space and time, of the Arabian Sea. The Luther-J i model, forced by interannual monthly winds, does much better. The main di screpancies are likely due to the models' forcing fields underestimating th e strength of the monsoon, and the vertical thermal structure not being ade quate to represent the real ocean, especially in upwelling areas. (C) 2001 Elsevier Science Ltd. All rights reserved.