Under relatively rare conditions of heavy precipitation, the strength
of hydrometeor returns can excede that of the (desired) clear-air
returns at low altitudes. Sometimes the downward velocities of the
hydrometeors are so large, and persist for such a short time, that the
signals are rejected by the time-continuity (reliability) algorithm of
versions 1 and 2. However, in the altitude regions where the
hydrometeors are just beginning to accelerate downwards (e.g. below 5
km, between 21 and 22 UT, and below 3 km just before 24 UT in the
example above), the signals can be accepted. Sometimes both the
hydrometeor and clear-air returns are identified as belonging to a
single, broad signal. Either way this sort of contamination tends to
give rise to large downward vertical velocities and enhanced
(beam-broadening corrected) spectral widths in the quick-look
plots.
This problem also affects version-0 data products. The version-3
signal processing (for which data products are due to be made
available in early 2005) has been designed to provide better
discrimination between clear-air and hydrometeor
returns. Nevertheless, hydrometeor contamination is sometimes very
hard to avoid.
This problem has been discussed in the following publication:
- McDonald, A. J., Carey-Smith, T. K. , Hooper, D. A., Fraser, G. J.,
and Lublow, B. P.: The effect of precipitation on wind-profiler clear
air returns, Ann. Geophys., 22, 3959 - 3970, 2004.
Internal Links:
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- Contacting the NERC MST Radar Facility
Project Scientist
- A comparison of the
different signal processing version numbers
- Known problems with
MST radar products: ground clutter
- Known problems with
MST radar products: interference
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