East Asia and Western Pacific METEOROLOGY AND CLIMATE

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For sharp absorption lines, the two channels close to the lineCinside
and one outside the line) can be easily selected. These two channels
will be close enough so as their contributions of aerosol extinction
and molecular scattering can be considered as the same, and with
various methods we can obtain the contents of the composition with
relatively strong absorption. But when the contents of the
composition is low and the aerosol content is high, there will be
obvious errors. In this case, aerosol and molecular extinction
corrections have to be made. Using the multichannel method presented
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by Wang Pengju and Zhou Xiuji L^' J the correction can be made. They
measured successfully the total ozone content and total water vapor in
Lhasa. In June of 1986, they found through the ozone Chappuis band
retrieval that the daily mean of total ozone content is 306(m-cm~atm)
in Lhasa. The value coincides well with the valueCmonthly mean of the
year) calculated through linear interpolation by latitudes from the
data observed at Xianghe, Hebei province(40° N), with Dobson ozone
spectrophotometer in their observations. At the same time, they also
obtained the total moisture content of Lhasa through the band of water
vapor.
In 1985 Zhao Yanzeng et al. •* made up a fast-tuning element
with calcite-KDP crystal. With the element they equipped a ruby laser
and tuned to two wavelengths within vapour absorption lines, 694.380
nm and 69^.215 nm. This DIAL system can change the wavelength from
absorption peak to valley within 100-300 microseconed. The stability
of the wavelength was better than +0.002 nm and the width of the line
is 0.001 run . Therefore, the remote sensing of water vapour
distribution can be carried out with this DIAL system. The probing
range is 2-3 kilometers'- 1^;'.If we futher improve properties of the
instruments and equip them with automatic data processing system and
vehicles, it is possible to realize the remote sensing of threedimensional
water vapour field in a range of several tens of
kilometers.
The description above is an outline of our research on remote
sensing of atmospheric compositions and optical properties. More
detailed results are described in respective references.