East Asia and Western Pacific METEOROLOGY AND CLIMATE

were mainly focused on predicting fronts or thunderstorms,
this kind of radar is unable to satisfy the needs of the
users today, particularly, the needs for aviational weather
services.
Using the principles of Doppler effect to detect the
weather elements has been discovered and experimented by
scientists (Lhermitte, 1964, Fujita, 1963), but it is in
the recent ten years development have just been made for
replacing the conventional weather radars with the Dopplar
weather radars. For example: NOAA, FAA, NCAR, NASA, as
well as NEXRAD and TOWR ( Terminal Doppler Weather Radar )
are expected to take the place of the conventional radars
in the USA and abroad. ( Zcnic, 1982; Mueller ,1987) In
addition, European countries are also devoting themselves
to the development of Doppler weather radars; and some
commercial products therefore have appeared.
A doppler weather radar not only possess the ability of
the traditional radars to observe the clouds and the
intensity of rain's echo and show-them on PPI or RHI, but
also can calculate the average wind speed with its spectrum
width and show the result on the monitor, therefore, with
these data forecasters can indicate not only fronts,
squall-lines, thunderstorms, typhoons, but also low level
wind shears, downbursts, gust fronts, and the location of
low level wind shears, which are hazardous to flying. And
then the abovesaid data are forwarded to the control tower
or air traffic controllers, thus enabling them to take
necessary actions to guide the aircraft to avoid hazards.
Taiwan is located in sub-tropical area where the
weather change in a year is influenced not only by the
Eastern Asia continental weather system but also the air
mass from the Pacific Ocean. In order to more understand
and observe the singnificant weather in this .area and
provide the best aviational weather services, CKS( Chiang
Kai-Shek ) International Airport set up a Doppler radar in
the April of 1987 for the detection of hazards weather,
such as downbursts, turbulences, and low level wind shears
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