. Compendium of meteorology. Meteorology. 1272 RADIOMETEOROLOGY from which it may be seen that at a range of 200 miles the lowest portion of a horizontally directed beam of a radar located at sea level is about 20,000 ft above sea level [2]. One of the finest practical applications of radar storm detection is made when radar-equipped aircraft use it to avoid violent convective activity while flying through an active cold front [11, 46]. As Fig. 6 shows, the front is far from being a solid mass of storms of moderate altitudes. This application is especially useful at night or when the pilot's v
. Compendium of meteorology. Meteorology. 1272 RADIOMETEOROLOGY from which it may be seen that at a range of 200 miles the lowest portion of a horizontally directed beam of a radar located at sea level is about 20,000 ft above sea level [2]. One of the finest practical applications of radar storm detection is made when radar-equipped aircraft use it to avoid violent convective activity while flying through an active cold front [11, 46]. As Fig. 6 shows, the front is far from being a solid mass of storms of moderate altitudes. This application is especially useful at night or when the pilot's vision is restricted by clouds. A re- cent development has been shown to have value in selec- tion of the least turbulent portions of storms when it is impossible to avoid them completely. This will be dis- ^^ussed in the section concerning echo-signal analysis. Radar observations of the approach of a cold front show the following sequence of events [67]: Scattered storm-echo signals are first detected at maximum ranges (100-300 miles) depending upon the activity of the front. These echoes are caused by hydrometeors in the upper portions of the tallest cumulonimbus along the front, and generally lie in an arc which may be closely identified with the position of the front as reported by surface observation stations. As the front approaches, the radar detects precipitation at successively lower levels and the original cells appear to increase in size and intensity. When the nearest portion of the front is about 50 miles away, a large part of it appears to be a solid line of precipitation if the antenna elevation angle is kept at or near zero degrees. The inexperienced ob- server will sometimes conclude that the front is actually intensifying, whereas the radar is simply detecting rain at lower levels which is almost invariably more wide- spread. This trend continues until the front passes over the radar, at which time echoes from the more distant storms along the front may disappe
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