East Asia and Western Pacific METEOROLOGY AND CLIMATE

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system, method of assimilation of observed data from
different sources and its application in monitoring and
forecasting.
(II) A New Atmospheric Remote Sensing System
During the last 15 years, we made every effort to
develop the theory and technology of ground-based remote
sinsing profiles of dynamic and thermodynamic parameters of
the troposphere. Since 1989,.a profiler station installed
with microwave radiometers and UHF Doppler radar has been
put into operation in the Beijing area.
(1) Thermodynamic profiling
Passive radiometers operating in the microwave
absorption bands of oxygen and water vapor have been
developed for sounding the thermodynamic prifiles such as
temperature, humidity and column liquid water in cloud.
Firstly, a new type of dual-channel microwave radiometer was
set up for providing humidity profiles and column liquid
water content in cloud: (Fig.3) [2]
Table (1) Dual-Channel Radiometer Characteristics
Parameters
Operating Frequencies
If Band width
Receiver Noise Figure
«. —
—— Integration
— — -
Time
—
___ _„_ _,_
- -
Antenna Beamwidth
Specification
_ — — __ — _ _
20.6, 31 .65 GHz
50-550 MHz
5.5 dB
Software selectable
2.5 deg
New features of this radiometer include a steerable
offset dual-paraboloid antenna producing optimum antenna
performance at each frequency, using noise diodes for gain
calibration and using voltage to frequency converters for
signal intergration and digital demodulation. The instrument
has a built-in-microprocessor to ensure system reliability.
In deriving total precipitable water vapor and path-
Intergrated liquid water content in cloud from radiometer
observations, linear statistical retrieval methods are
employed. For the Beijing area, the path-integrated
precipitable water vapor V and liquid water content in cloud
L can be calculated in realtime from the following formula:
V»-0.037+30.41 * (20.6 GHz > "" 12.86 T(31,6 GHz) (1)
Er=-0. 017-0.214 T (20.6 GHz) + 0 . 663 t (31. 6 .GHz-) (2)