Instantaneous Height of Sea Surface: A Comparison Between Local Field Observation and The Simulated Level from Global Models

Abstract

This paper explores the usability of a global database containing sea surface height. We look at simulated heights of the sea surface at a certain area and compare them with field observation from three stationary stations and one from an ocean cruise. Mean Sea Surface data from the global model and Mean Sea Level (MSL) data from the field observation must be referenced to the same height system. For this reason, a height system in the form of a global ellipsoid model, namely the World Geodetic System 1984 (WGS84) was chosen as the height reference. After being referenced in the same height system, then the MSS and MSL are compared by looking for the difference between the MSS of the ellipsoid $(\mathrm{h}_{\mathrm{M}\mathrm{s}\mathrm{s}})$ and the MSL of the ellipsoid $(\mathrm{h}_{\mathrm{M}\mathrm{S}\mathrm{L}})$ and the average of these differences. The results show that the differences are in the order of $\lt$1m. The simulated tidal waves from the global model is incapable to describe the actual sea level variations, although it is able to capture the general trend. It should be noted that the field observation is incomplete and subject to various uncertainties. Bearing in mind the limitation of the models and uncertainties of the observation, our study confirms that such an order discrepancy in a global sense is tolerable.