7.5
A new system for airborne measurements of high-resolution 3D winds using a Tethered Lifting System (TLS)
Michael L. Jensen, CIRES/Univ. of Colorado, Boulder, CO; and M. Tjernström and A. Targino
A new system developed to measure high-resolution 3-dimensional winds and fluxes using a Tethered Lifting System (TLS) will be presented. The TLS incorporates kites and tethered balloons, as lifting platforms, along with a powered winch to raise and lower the platforms. Details of the design of the 3D wind system will be outlined including selection of the sensors and instruments, implementation of the motion correction algorithm, and estimation of accuracy and error sources. Finally, preliminary results obtained from measurements made during a three-week ice drift as part of the Arctic Ocean Expedition (AOE-2001) will be presented.
The system is composed of a 3D sonic anemometer used to measure all three components of the wind and the sonic temperature, a fast response water vapor sensor, and meteorological sensors for mean temperature and humidity. The entire payload is vaned into the wind to maintain mean flow into an open sector of the sonic anemometer and force rotations about its vertical axis into a low frequency regime where they can be corrected more easily. The payload operates in a stand-alone manner when suspended from a tethered balloon or kite tether. A pair of miniature high-speed data loggers and rechargeable batteries provides ample memory capacity and power to log data for flights of up to three hours in duration.
The 3D wind measurement system incorporates a suite of motion sensors to allow post-processing to transform the data into an Earth-referenced (u, v, w) coordinate frame. These sensors provide high-speed (20 Hz) measurements of accelerations and magnetic field in 3 axes and precision pitch and roll angles. One-second observations of raw GPS measurements are made and then differentially corrected (using base station data) to provide precise position and velocity data in 3 dimensions.
The basic theory behind the motion correction and transformation equations will be presented, as well as, estimated error sources and predicted accuracy of the system. Preliminary high-resolution profiles of wind, temperature, and water vapor are presented from initial tests of the system conducted from a camp set up on an ice floe near the North Pole. In addition, preliminary calculations of momentum, and latent and sensible heat flux will be presented for altitudes between the surface and 2 km, along with low altitude comparisons made with a tower-fixed flux system mounted on a nearby 18 meter mast.
Session 7, Field Programs and Observational Technology
Tuesday, 16 July 2002, 3:30 PM-5:30 PM
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