Measurement resolution criteria for assessment of coastal ducting

We examine the required vertical and lateral resolutions associated with refractivity measurements of coastal regions for the case in which these measurements are injected into reliable propagation models which give propagation factor fields at frequencies of 1, 3, and 10 GHz. We also address the required time separations in making refractivity measurements for ducting and extreme subrefraction conditions. These results are derived from actual helicopter measurements over the east and west coasts of the United States. Errors are characterized through a simulation methodology where the measured vertical and lateral refractivity profiles are spoiled and subsequently injected into propagation models to produce error propagation factor fields. Although results for only a limited number of cases are given, they demonstrate that serious errors in the propagation factors over broad regions of the lower troposphere may arise when vertical and lateral resolutions are significantly spoiled. (6 pages)