Effective height of a dual-wavelength scintillometer system over complex terrain

In 2005-2007 a combined Optical & Millimeter-Wave Scintillometer (OMS) system consisting of a large aperture scintillometer (LAS) manufactured by Kipp & Zonen, B.V., Holland, with a light source of 0.88 m and a millimeter-wave scintillometer (MWS) operating at 94 GHz (about 3 mm wavelength) built by Rutherford Appleton Laboratory, UK, was tested at Sheepdrove Organic Farm, Lambourn, Berkshire, UK (51.5° N, 1.5° W). The terrain is complex, but typical for this part of England: rolling chalk downland (130 m to 220 m above sea level) with the soil being a variable mixture of flints, chalk, and brown rendzinas. Earlier scintillometry studies have revealed that over non-flat terrain or for slanted paths the so-called effective height of a scintillometer is a function of atmospheric stability. We found that over flat terrain the effective height for the LAS and MWS are almost the same. However, over complex terrain such as Sheepdrove Farm, we found differences. The practical consequences of our findings are discussed.