Sunday, 9 February 2003

Exploring the Effects of Applying a More General Radar Equation to Wind Profiler Data

Data collected by the Galápagos Islands’ Doppler wind profiler using 100- and 500-m pulse lengths do not yield the same wind profiles. The longer 500-m pulse length profiles are displaced in height from those of the shorter 100-m pulse. The standard radar equation used to assign heights to measured winds assumes that the reflectivity in the atmospheric scattering volume is constant and the range of the scattering volume is much longer than the profiler pulse length. These assumptions are often violated, producing substantial differences in 500-m height assignments.
This study adjusted 500-m pulse wind height assignments using a more general radar equation. The more general equation takes into account that the reflectivity in the scattering volume can be non-constant and the range of the scattering volume can be of similar length to the profiler pulse length.
Height corrections were applied to El Niño, La Niña, and normal 10-day case studies. Applying the more general radar equation reduced the mean absolute difference between the wind speed and direction profiles for all cases at heights above 750 m. The results implied that height corrections could be applicable during different atmospheric conditions.
The results of this research could allow profiles collected with different pulse lengths to be merged into one product, thereby improving data quality. Further research is needed to determine the statistical significance of the improvement and the equation’s applicability to other time periods in the Galápagos and other wind profiler data around the world.

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