Skip to main content

The effect of artificial rain on wave spectra and multi-polarisation X band radar backscatter

Buy Article:

$59.35 plus tax (Refund Policy)


We have carried out wind-wave tank measurements using wave-height and wave-slope gauges and a coherent 9.8 GHz (X band) scatterometer, when the water surface was agitated by heavy rain (160 mm h-1 to 300 mm h-1) and by wind (2 ms-1 to 12 ms-1). The upwind-looking scatterometer was operating at co- (VV- and HH-) and cross- (HV-) polarisation at a steep incidence angle of 28°. In the presence of rain, the power spectral density of the wind-wave spectra is enhanced at frequencies above about 5 Hz and it is reduced at lower frequencies. This is the net effect of surface roughness production by the rain-induced splash products and of wave damping by the rain-induced turbulence. We measured isotropic (rain-dominated) wave spectra at low wind speeds and anisotropic (wind-dominated) wave spectra at high wind speeds, with a transition wind speed that increases with rain rate. The radar backscattering at co-polarisation at low wind speeds is mainly caused by rain-induced ring waves, whereas at cross-polarisation, at all wind speeds, other rain-induced splash products, like crowns, stalks, and cavities, are the dominant scatterers. We have found a rain-induced increase of the radar backscatter at co-polarisation at wind speeds of up to 9 ms-1 and at cross-polarisation at all wind speeds. At cross-polarisation the radar backscatter slightly depends on rain rate. Using our results an analysis of spaceborne synthetic aperture radar (SAR) images of tropical rain cells was performed.

Document Type: Research Article


Publication date: October 20, 2002

More about this publication?

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
ingentaconnect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more