Monday, 14 January 2002
An Integrated Airborne Measurement System for the Determination of Atmospheric Turbulence and Ocean Surface Wave Field Properties
A small research aircraft has been used in a series of air-sea interaction experiments to investigate the spatial variation of both marine atmospheric boundary layer and the ocean surface wave field. The integrated instrument suite of in situ and remote sensors carried by a LongEZ (registration N3R) airplane is used to measure mean properties of the atmosphere as well as turbulent fluxes of heat, moisture, and momentum. N3R is an ideal platform for acquiring turbulence measurements with minimal flow distortion at low altitudes (~10 m) and slow aircraft speeds (~50 m/s). A distinct advantage of its pusher design is that it allows for the mounting of instruments on the aircraft nose which minimizes contamination due to propeller-induced turbulence, engine vibration, and exhaust. A nadir-pointing 36-GHz Ka-band radar scatterometer and a laser altimeter array and are used to determine long and short wave characteristics, respectively, of the sea surface. The scatterometer measures changes in the integrated roughness of short ocean waves on the order of 2 to 100 cm while the laser altimeter array is designed to measure the sea surface profile and the one- and two-dimensional slopes of intermediate scale waves on the order of 1 to 10 m. The data obtained from these remote sensors is unique in that it provides wave information from small capillary waves to long swells coupled with wind stress and turbulence measurements in the atmospheric surface layer. Data from two independent global positioning systems are blended with fast response accelerometers to create an accurate accounting of aircraft position, attitude, and velocity.