Geoscience Reference
In-Depth Information
Figure 12.9
(a) Basic operation of a radar system used to measure the presence of hydrometeors in the atmosphere from
which estimates of precipitation at the ground are made; (b) The NEXRAD system which is the basis of the weather radar
system in the USA; (c) The array of NEXRAD systems deployed in the USA and the maximum range they could sample
over. (From NOAA, 2010, and Firstweather, 2010.)
distance to the hydrometeors, while the strength of the return signal provides
information on the amount of hydrometeors present (Fig. 12.9a). In some radar
systems minor difference in the wavelength caused by the Doppler effect are used
to allow the system also to determine the speed of the hydrometeors moving in the
wind relative to the radar station.
Because the energy pulse used for detection is at microwave frequency (with
wavelength of order 10 cm), it is the
average density
of hydrometeors in the sample
