A 1299-MHz boundary layer wind profiler has been in operation in Hong Kong since 1996. It provides wind data normally up to about 2 km in clear air and about 6 km in rain.

In mid-2002, a couple of changes were made to the operation of the profiler with a view to extending its range to about 9 km in rain. These changes were:

(a) Extending the inter-pulse period, in order to receive radar signals returned from higher altitudes; and

(b) Increasing the frequency of radio pulses by four folds, so as to enable, through statistical averaging, the radar signals to stand out against the background noise.

The results were very encouraging. Extra wind data were received at altitudes of 6 to 9 km. These data were compared with the upper-air radiosonde ascents, with reasonably good results. With the extended range, these data help enhance the monitoring of severe weather, such as heavy rain associated with the passage of upper tropospheric troughs.

The paper describes the technical changes implemented on the wind profiler, summarizes the comparison results and describes the applications of the profiler°¦s data in the monitoring of severe weather.