Coherent particle scattering

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Radar waves can be scattered by small scale cloud structures. This type of scattering is similar to the so called Bragg scatter due to humidity variations. Both cloud liquid water and humidity structures lead to structures in the atmospheric refractive index. We call this type of scattering coherent particle scattering.
Coherent particle scattering can be significant compared to incoherent particle scattering for radars with a long wavelength. We think we have seen signs of this type of scattering in cumulus clouds measured with a 10-cm radar.
In clouds coherent particle scattering can be significant compared to coherent molecular scattering (Bragg scattering) by humidity structures. In clouds strong liquid water variations are possible, but humidity variation are almost absent.

The main article on this topic is Erkelens et al. 2001, which is almost identical to chapter 5 of my thesis. Chapter 6 of this thesis contains estimates of the conditions under which one may expect coherent particle scattering and the radar systems for which it is important. Below you can also find links to the conference articles that were published before these larger works.
People interested in this, may also be interested in a small conference paper "Clear-air scattering observations: downdraft and angels" with dual-frequency observations of a downdraft and a 10-cm radar measurement of an angel with a temporal resolution of milliseconds.

Articles

Cloud measurements with radar
PhD thesis, 13 November 2000.
Victor Venema
Chapter 5. Coherent scattering of microwaves by particles: Evidence from clouds and smoke pdf (0.4 Mb)
Chapter 6. The contribution of coherent particle scattering to the reflections of radio waves by clouds pdf (0.4 Mb)

Coherent particle scatter in clouds: reflection calculations based on in-situ measurements
Proc. 13th Int. Conf. Clouds Precipitation, Reno, Nevada, USA, 14-18 Aug. 2000.
Victor Venema, Jan Erkelens, Herman Russchenberg, and Leo Ligthart

Some notes on scattering of radiowaves by clouds
Proc. Symposium Remote Sensing of Cloud Parameters: Retrieval and Validation, pp. 63-70, 21-22 October 1999, Delft, The Netherlands.
Victor Venema, Jan Erkelens, Herman Russchenberg, and Leo Ligthart

Coherent particle scatter in developing cumulus clouds
Proc. 29th International conf. on radar meteorology, 12-16 July 1999, Montreal, Canada, AMS, pp. 904-907.
J.S. Erkelens, V.K.C. Venema, and H.W.J. Russchenberg

Coherent Particle Scatter in Smoke and Cumulus Clouds
Igarss 99, Hamburg, vol. 1, pp. 687-689, June 28 - July 2, 1999, Germany
J.S. Erkelens, V.K.C. Venema, and H.W.J. Russchenberg