Radar beam
As the distance from the radar site increases, the granularity of the radar beam decreases, which degrades the accuracy of radar products. For example, a 1° wide beam sent at the antenna has a width of 2 km across at 120 km distance. The following image shows how the detected bins grow larger further away from the radar.
Many radar products are affected by the curvature of the Earth. A radar beam transmitted at a 0° vertical angle from the radar site on a flat environment would be 780 meters above ground at 100 km distance, before accounting for atmospheric refraction. While all IRIS Focus radar products are corrected for curvature and refraction effects, weather phenomena from below the curvature threshold cannot be detected.
