East Asia and Western Pacific METEOROLOGY AND CLIMATE

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where V and L are in centimeters and the radiometer measured
quantities in nepers. Root mean square (RMS) difference of
total precipitable water vapor measured between the
radiometer and the radiosonde is about 0.3 mm (7*).
A nonlinear iteration method is used to retrieve the
water vapor profile in the troposphere from microwave
brightness temperature measurements at different elevation
angles. Some of the retrieved profiles have been shown in
Fig.4-5. It is found that the inversion of humidity in lower
troposphere can be detected by our method. Comparing with
radiosonde data, the relative errors of radiometer
measurement at different levels are shown in Fig.6 [3]-[7]
Secondly, another two microwave radiometers operating
at frequencies 52.8 and 54.4 GHz also have been developed
and applied by the Department of Geophysics, Peking
University to obtain the temperature profiles [8]-[9], Fig.7
show the RMS errors of the derived temperature at different
levels of troposphere by using radiometers measurement in
comparison with radiosonde data.
(2) Wind profiler
The first UHF wind profile radar in China has been
installed and tested in Beijing (Fig.8} [10]. The major
specifications of the radar are listed as following:
Radar:
Wavelength: 0.82 m (365.85 MHz)
Peak Power: 25 kw
Antenna: 108 Yagi elements, 3 beams (one is
zenith, two are 15 degrees off zenith)
Beamwidth: 6 degrees (3 dB)
Signal processing:
Preprocessing: time and spectrum averaging
Processing mode: 3 (High, Mid., Low altitudes)
Pulse width: 1-9 microsec.
PRT: 50-300 microsec.
Spectrum resolution: 128 points
Number of heights: 30 max for each mode
Estimated parameters: first 3 of Doppler mements
horizontal wind velocity,
horizontal wind direction,
vertical wind velocity
Fig, 9 is an example of a time series of horizontal
wind profiles given by UHF Doppler Radar. Every profile was
produced at an interval of 30 minutes. The height resolution
is 100 m at the height coverage from 0.5 to 4.1 km and 200 m
at 5.0-12.5 km. There are 2 additional profiles of
horizontal winds ploted with rawinsonde data time 1900 and
0100 as compared to those profiles measured by profiler
radar at the same moments. It can be seen that profiler's
measurements a well agreed to rawinsondeVs ones but show the
presence of a smaller scale system at the height from 3 to 4
km.