Results of the 1988 fluxes-from-scintillation experiment

An experiment was performed to assess three new concepts for the remote sensing of heat and momentum fluxes in the atmospheric surface layer. These concepts use optical scintillation caused by turbulence along a horizontal propagation path from a transmitter to a receiver. The fluxes are derived from the measured scintillation using Monin-Obukhov similarity theory (MOST) of the horizontally homogeneous atmospheric surface layer. The first concept is to measure the refractive-index structure parameter, C1 2 , and inner scale, lo , using an optical inner-scale meter; the values of C2n and la are empirically related to the heat and momentum fluxes using MOST. The second concept is to use scintillometers to measure cfat two heights; the ratio of the two C2n values gives surface-layer stability; C2 and stability then give heat and momentum flux using MOST. The third concept is to measure apparent mean vertical wind by deploying an optical-scintillation cross-wind sensor with its measurement axis turned vertically. If this apparent vertical wind has Monin-Obukhov similarity scaling, then its measurement can be used to determine heat flux. The order in which these methods are described above is from most to least successful. In particular, the first method, that of measuring lo and C2n , appears to be very robust in that it produces good results even for very nonideal conditions. It is expected that it will be routinely used for future experiments.