Short‐wave directional properties in the vicinity of atmospheric and oceanic fronts

The author estimated and investigated mean wave directions and directional spread parameters of 0.505 Hz ocean waves using data from 24.5 MHz‐HF ocean radar. The author described temporal and spatial variabilities of the short‐wave field. The short‐wave direction is a good indication of wind direction. The spread parameter was related to the variability of wind direction. The author examined the case that an atmospheric front or an oceanic front exists in the HF ocean radar observation area. In the case of an atmospheric front the short‐wave direction changed with the passage of the atmospheric front. Furthermore, the complicated frontal structure, which cannot be verified from a weather chart, was revealed. Narrow directional spread was observed in the vicinity of the convergent front, which was reproduced using a simplified model based on the wave action conservation law. The result shows that wave refraction associated with a frontal convergent zone is important in determining the spatial variability of short‐wave directional properties.