A study on aspect sensitivity of clear-air turbulence using coherent radar imaging of VHF atmospheric radar

Abstract

Aspect sensitivity of clear-air turbulence was examined with multiple-receiver coherent radar imaging (CRI) of VHF atmospheric radar. The study was carried out by means of aspect angle, estimated from two CRI parameters: direction of arrival of echo center from oblique radar beam and brightness distribution width from vertical radar beam. The brightness distribution was retrieved by the Capon method. Modification of brightness value has been made with a suitable radar beam-weighting function before estimating the two CRI parameters. The radar beam-weighting function used for correction is a Gaussian form, and its standard deviation (beam width) varies with off-beam direction angle and is also adaptive to signal-to-noise ratio of echoes. The use of adaptable beam width can avoid over-modifying the brightness values at the edges of the imaged map, yielding a more reliable estimate of aspect angle. The CRI-estimated aspect angle was compared with that obtained from comparison of echo powers of different oblique radar beams. The statistical features of aspect angles obtained from the two approaches are consistent.