SYNTHETIC SUBSURFACE PRESSURE DERIVED FROM BOTTOM PRESSURE AND TIDE-GAUGE OBSERVATIONS

Synthetic subsurface pressure (SSP) can be formed from tide gauge reco rds and from bottom pressure measurements to provide a consistent and convenient basis for comparison of these two different types of observ ations. Common methods for this estimation are reviewed, and their acc uracy is evaluated. Calculations show that subtidal SSP estimates from sea level (SSPSL) and from bottom pressure observations (SSPBP) at cl ose sites agree only in a finite band of frequencies, corresponding to periods between 3.5 and 30 days. At the lower frequencies (periods lo nger than 30 days), sea level observations are subject to errors induc ed by the daily measure of staff height. At higher frequencies (period s between 1.5 and 3.5 days), the amplitude of fluctuations is too smal l to be resolved by a sea level gauge.