KGRN K B U C KB J C L89 30 8 KHEF KCOS KCEN NORTH UP K F T C H 8 2 KCLN KGHR 3 0 KLAR KLVL KCO S LAR H C T H82 KDEN KFT R KB W GPH 25 V SIG / AIR MAP NRST WPT AUX NEXRAD AGE: 5min RAIN MI X SNOW L I  G  H  T H  E  A  V  Y 30NM 5 338 1 1652 200 46 13.7 2300 23.0 NAV1 117.95 115.40 NAV2  108.00 117.95 123.750 119.925  COM1 135.975 120.050 COM2 GS  123kts  DIS  53.2NM ETE  25:58  ESA  16800 ENGINE ECHO TOP CLD TOP LTNG CELL MOV METAR NEXRAD LEGEND MORE WX MAP - NAVIGATION MAP Figure 5-11. Radar data shown on an MFD. Onboard Weather Radar Systems Ground Weather Surveillance Radar 0 Figure 5-12. A radar beam allows you to see some weather cells,  but not others. Ground weather surveillance integrates weather information  from many ground radar stations. The weather information  collected from many sources is then used to create a  composite picture that covers large volumes of airspace.  These composite radar images can then be transmitted to  aircraft equipped with weather data receivers. Although the tilt of the radar antenna can be adjusted upward  and downward, the weather phenomena that the weather  radar can detect are limited in both direction and range. The  A simple color‑coding scheme, as shown in  Figure 5-14,  is  used to represent the intensity of radar echoes detected by  an onboard weather radar system. When a cell is detected by an onboard weather radar system,  that cell often absorbs or reflects all of the radio signals sent  out by the radar system. This phenomenon, called attenuation,  prevents the radar from detecting any additional cells that  might lie behind the first cell.  Figure 5-13  illustrates radar  attenuation, in which one cell “shadows” another cell. radar system in  Figure 5-12  fails to detect the two cells that  lie below and beyond the radar beam. As illustrated in  Figure 5-12, you must be careful not to  assume that the only cells in the area are the ones shown on  the radar display. The two additional cells in  Figure 5-12  are  present, but not detected by the onboard weather radar  system. Onboard weather radar uses an adjustable aircraft mounted  radar antenna to detect, in real time, weather phenomena near  the aircraft. The coverage of an onboard weather radar system  is similar to a flashlight beam, as illustrated in  Figure 5-12. You should always remember that the radar displays only  areas of water or moisture (rain, sleet, snow, and hail). Radar  does not display turbulence or lightning. 5-10