Application of over-the-horizon radar observations to synoptic and mesoanalysis over the atlantic

Over-the-horizon (OTH) radar observations of surface wind direction offer a high-resolution (15 km) resource for synoptic and mesoscale wind field analysis. With horizontal resolution at the lower end of the mesoscale and areal coverage in the synoptic scale, OTH radar has the potential to contribute significantly to the amelioration of the data sparseness that has long plagued over-ocean surface analysis. Because of a twofold ambiguity in the OTH radar algorithm for determining surface wind direction, however, mapping surface wind directions unambiguously would normally require two radars with overlapping coverage. Alternatively, the single-radar ambiguity can be resolved by combining NWP model analyses and incidental surface wind observations with meteorological insight. An approach to the latter, less expensive solution is presented that relies on the classic principles of streamline analysis and an easy-to-use graphical wind field editor developed specifically for this task. A case study demonstrates the utility of the resulting OTH radar analyses of surface wind direction over the tropical Atlantic Ocean. Existing military OTH radars in several countries could be used for such monitoring with little impact on their primary mission.