content_image/541407.jpg content_image/541411.jpg
<img src='content_image/541407.jpg'>

## Onboard Weather Radar Systems 

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. 

<img src='content_image/541411.jpg'>

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 

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. 

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. 

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. 

## Ground Weather Surveillance Radar 

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. 

