East Asia and Western Pacific METEOROLOGY AND CLIMATE

146
PRF: 80-2000 Hz
Minimum detectable power: -112 dBm
Prom the intensity and spectrum of radar echoes, rainfall
rate, radial velocity/ wind shear and turbulence intensity
have been derived and identification of hail also will be
tested. In the summer time, radar echoes from clear-air of
lower troposphere below 3 km often were detected.
The type 713D radar that is the first Doppler radar at
5 cm wavelength manufactured in China will be operated in
1990 in the Beijing area.
Accurate estimation of the rainfall rate from radar
measuremant is an attractive issue for meteorologists and
hydrologists. Though many years of study, we have found a
usual formula that relates rainfall rate R to the radar
echoes intensity Z in the Beijing area as follows: [11]
b
Z=a R ( 3 )
where in averaging a=236, b=1.46. However, the parameters a
and b significantly depend on the raindrop-size
distribution. The standard deviation between radar and
raingauge measurement is about 40&.
On the basis of theoretical calculation and comparison
of radiometer data with the raingauge measurement, the
relation between extinction coefficient and rainfall rate R
has been found as follows. [3]
d
a =C R (4)
It is shown that the parameters C and D are insensitive
to the raindropsize distribution. The RMS deviation of the
relation a-R for different size distribution is reduced to
15 &. Therefore, more accurate estimation of path-integrated
rainfall from microwave radiometer measurements might be
expected. Unfortunately, the spatial distribution of
rainfall rate along the sounding path cannot be retrieved
from microwave radiometer data. To solve this difficulty, a
synthesized system consisting of radar and microwave
radiometer with a common antenna has been developed and
tested.