Effects of radar beam width and scatterer anisotropy on multiple-frequency range imaging using VHF atmospheric radar



[1] Benefiting from the changeable antenna array size and flexible radar beam direction of the middle and upper (MU) atmosphere radar (34.85°N, 136.11°E), the effects of radar beam width and scatterer anisotropy on the performance of multiple-frequency range imaging (RIM) were examined in addition to numerical simulation. First, nine transmitter/receiver modes were employed to reveal that a wider radar beam gives a larger phase bias in the RIM processing. Based on this, layer positions and layer thicknesses were estimated from the imaged powers of various radar beam widths after corrections of phase bias and range-weighting function effect. Statistical examination showed that the imaged layer structure was thicker for a larger radar beam width and this feature became more evident at a higher altitude, thereby demonstrating the influence of radar beam width on the practical performance of RIM. Second, the scatterer anisotropy in the layer structure was examined by means of a vertical and three oblique radar beams (5°, 10°, and 15° north), which were transmitted in company with the RIM technique. The vertical beam observed some single-layer and double-layer structures that were not always detected by the oblique beams, indicating the existence of anisotropic scatterers in the layers. In addition, a comparison of layer positions between the vertical and oblique radar beams showed that anisotropic characteristics of the upper and lower layers of a double-layer structure can be different, demonstrating one more capability of RIM for investigating fine-scale features of the atmospheric layer structures.