FM-CW Radar Observations in Northeastern Colorado Compared with Rawinsonde-Measured Profiles of Refractive Index

摘要

This report deals primarily with a long period during which the FM-CW radar and a RAWINSONDE station were operated side-by-side in the NHRE program in 1974. The RAWINSONDE station and the FM-CW radar were colocated at Sterling in northeastern Colorado. Three balloons a day were launched while the radar operated in a vertically pointing, non-Doppler mode. It is concluded that the radar is a reliable detector of elevated refractive layers. In fact it provides a better estimate of the height and persistency of such layers than do balloon soundings because layers undulate and the refractive index distribution is often transient and patchy. Single balloon sounding data cannot provide the important persistency information. Insects are shown to be an important contaminant in the radar observations. It is demonstrated that insect targets are adequately separated from the clear-air returns if the range resolution of the radar is good (typically 3 mi in the case of the Sterline observations). This ability is needed in biogeographical areas such as the U.S. Midwest if the clear-air elevated layers of meteorological interest are to be distinguished from insect layers.