A Comparison of Long Coastal-trapped Wave Theory with Remote-Storm-generated Wave Events in the Gulf of California

Abstract

Moored pressure, temperature, and current observations of low-frequency coastal-trapped wave (CTW) events in the Gulf of California are examined in the context of long-wave CTW theory. Mode 1 CTWs that are generated by summer tropical storms are consistent with the occurrences and propagation speeds of the observed wave events in the gulf. The mode 1 CTW generation, however, occurs farther north than observed, presumably due to insufficient wind data. The mode 1 and observed across-shelf wave structure in the gulf are similar, in that alongshelf currents are nearly depth independent in 100-m water depth, the pressure response is strongest at the coast with decay offshore and with depth, and downwelling occurs over the shelf with the amplitude of the mode 1 density response within a factor of two of the observed response. The main discrepancies between the mode 1 and observed wave structure are that the speed of the mode 1 alongshelf current increases toward the coast while the weakest observed speeds occur nearest the coast, and mode 1 cannot account for the observations of weak across-shelf phase lags in pressure, density, and alongshelf current. While frictional effects are consistent with some of the observed wave properties, frictional coupling of the first three CTW modes does not improve the model agreement with the observations. In addition to model comparisons, it is shown that temperature measurements on the Baja California peninsula shelf that are significantly correlated with the wave signal may be explained in terms of a possible wave-dissipation mechanism in the northern gulf.