THE ABILITY TO PREDICT LOW-ANGLE HEIGHT ERRORS WITH THE NBS SURFACE-CORRECTED MODEL ATMOSPHERE

A comparison is made between values of radio ray bending which is calculated in two ways: one using a ray-tracing computation based on radiosonde data; and the other using the National Bureau of Standards exponential reference atmosphere (1959) corrected to match the refractivity measured at the surface. The refractivity data for the ray-tracing computations were obtained from twice-daily radiosonde soundings taken at Albany, New York, and Nantucket, Massachusetts, during July and November 1963. Results indicate that the NBS model does not completely remove height errors, but it can be used effectively to offset errors due to slow seasonal changes bending conditions. The correction technique is not effective during periods of anomalous propagation. A review of more recent prediction techniques (1963) is presented, and recommendations are made for their field evaluation.