 |
| Titel |
The effect of precipitation on wind-profiler clear air returns |
| VerfasserIn |
A. J. McDonald, T. K. Carey-Smith, D. A. Hooper, G. J. Fraser, B. P. Lublow |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 22, no. 11 ; Nr. 22, no. 11 (2004-11-29), S.3959-3970 |
| Datensatznummer |
250015063
|
| Publikation (Nr.) |
 copernicus.org/angeo-22-3959-2004.pdf |
|
|
|
|
|
| Zusammenfassung |
| A small number of studies have indicated that reductions in the signal
strength of clear air returns can be observed at low altitudes in regions of
precipitation. This study uses data from the NERC MST radar facility in
Aberystwyth (52.4° N, 4.1° W) and co-located tipping bucket
rain gauge data to determine whether this effect can be observed for all
periods where high rainfall rates were observed at the ground. The period
selected for examination includes all of the days where a peak rainfall rate
of 6mm h-1 was exceeded in 2001. A statistical examination of VHF
radar signal power during periods with and without surface rainfall suggests
that the returned power is reduced by the presence of precipitating clouds.
The corrected spectral width of the Doppler spectra is also significantly
wider during periods of precipitation. The process which causes the decrease
in the VHF signal power seems to be associated with a reduction in Fresnel
reflection within precipitating clouds. This, in turn, may be due to a
reduction of humidity gradients in clouds. UHF wind profiler data is also
used to show that there is a relationship between enhanced UHF
returns (signifying precipitation) and reduced VHF returns. To clarify the
processes and effects observed we examine three case studies which show
typical relationships between the VHF signal power and surface rainfall or
enhanced UHF signal-to-noise ratios. The effect of precipitation on the
signal processing scheme's derivation of signal power and spectral width is
explored using individual Doppler spectra. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|