ABSTRACT
Refraction effects were summarized in Section 1.4.2. The ray tracing procedures needed to analyze refraction effects were developed in Section 2.5 and Section 2.6. Figure 2.7 provides sample ray trajectories for the ITU-R model atmosphere and for radio refractivity profiles obtained from rawinsonde observations (RAOBs) made on June 4, 1996, in Norman, OK. The trajectories calculated by using the RAOB data differed little from the model trajectory for rays launched at an initial elevation angle of 3
°
. At a 1
°
initial elevation angle, the trajectories calculated for the 00:00 UT and 12:00 UT RAOBs differed from each other and from the model prediction. For a 0
°
initial elevation angle, the ray for the 00:00 UT RAOB was trapped below 57 m (0.414 km msl) above the surface (at 0.357 km msl). For these calculations, the Earth’s surface was assumed to be a sphere concentric with the center of the Earth at the height of the meteorological instrument used to make the surface observations (about 1 m above the physical surface).
