Analysis of a 12-Year Record of Sea-Surface Temperatures Off Pt. Sur, California.

摘要

Daily observations of sea-surface temperature (SST) taken just north of Pt. Sur, California over the past 12 years are examined for statistical and oceanographic content. Spectral analysis of the data reveals an annual cycle and two harmonics, but no obvious influence from the local winds or tides. A statistical model has been constructed based on a decomposition of the data into its various deterministic and random components. As expected, the model provides forecasts which are significantly better than those that would be obtained from a simple climatological treatment of the data alone. The model is also used to generate simulated series, which in turn are used as a basis to estimate adequate sampling rates. In 6 years of the 12 year record, an abrupt major decrease in SST was observed between February and April and has been identified as the spring transition to coastal upwelling. One such transition was found to occur almost simultaneously at three locations; including Pt. Sur, along the California coast between Pt. Conception and San Francisco. The data also indicate that a well-defined annual temperature cycle does exist at Pt. Sur although its range is reduced and its maximum occurs later in the year than would normally be expected at this latitude. Three El Nino events are clearly evident in the 12-year record including the present El Nino; SSTs have increased by almost 3C at Pt. Sur as a result of the present El Nino warning. Over the whole 12 year period an average increase in temperature of 1.6 C was found. (Author)