On temporal spectra of scintillometers
Evans, Jonathan G.; De Bruin, H.A.R.. 2009 On temporal spectra of scintillometers. [Speech] In: 9th European Conference on Applications of Meteorology (ECAM), Toulouse, France, 28 September - 02 October 2009.Full text not available from this repository.
Clifford (1971) derived expressions for the real and imaginary part of the temporal spectra W(f) for spherical waves propagating through the atmosphere. To a good approximation, the transmitter of a Millimeter-Wave Scintillometer (MWS) can be regarded as a point source and thus Clifford's theory is applicable to a MWS. Nieveen et al. (1998) extended Clifford's theory to large aperture scintillometers (LAS). In both cases a so called corner frequency, fc , can be defined. For frequencies smaller than fc , the real part of W(f) is approximately constant at Wplateau, whereas for f>fc , the real part of W(f) is proportional to f-8/3 for the MWS. It is noted that Wplateau is inversely proportional to the cross wind uc and that fc is proportional to uc, therefore the integral of W(f) over all f is independent of uc; however, this applies for the case where the cross wind does not vary along the path. During a field experiment carried out in mid-summer 2006 at Sheepdrove Organic Farm, UK, over mixed agricultural land use and complex topography, W(f) was measured by a 94 GHz MWS. There were contrasting cool-windy and hot-convective weather conditions during the experiment. With these data the Clifford theory will be validated.
|Item Type:||Publication - Conference Item (Speech)|
|Programmes:||CEH Programmes pre-2009 publications > Water > WA02 Quantifying processes that link water quality and quantity, biota and physical environment > WA02.1 Hydrological processes|
|CEH Sections:||Harding (to July 2011)|
|Date made live:||13 Oct 2010 13:27|
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