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A study of multiple-frequency range imaging of atmospheric VHF radar: Effects of radar beamwidth and scatterer anisotropy

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38th COSPAR Scientific Assembly 2010

Space Studies of the Upper Atmospheres of the Earth and Planets including Reference Atmo- spheres (C)

Advances in Remote Sensing of the Middle and Upper Atmosphere and Ionosphere from the Ground and from Space, including Sounding Rockets and Multi-Instrument Studies (C02)

A STUDY OF MULTIPLE-FREQUENCY RANGE IMAGING OF ATMOSPHERIC

VHF RADAR: EFFECTS OF RADAR BEAMWIDTH AND SCATTERER ANISOTROPY

Jenn-Shyong Chen, [email protected]

Chienkuo technology University, Changhua, Taiwan, China Presenting author: Jenn-Shyong Chen, [email protected] Chienkuo technology University, Changhua, Taiwan, China Jun-ichi Furumoto, [email protected]

Kyoto University, Japan

Takuji Nakamura, [email protected]

National Institute of Polar Research, Tachikawa, Tokyo, Japan

Benefiting from the changeable array size and flexible radar beam direction of the Middle and Upper atmosphere (MU) radar system (34.85

◦

N, 136.11

◦

E), the effects of radar beamwidth and scatterer anisotropy on the performance of multiple-frequency range imaging (RIM) were examined in addition to numerical simulation. Nine transmitter/receiver modes were first employed to reveal that a wider radar beam yielded 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 beamwidths after proper corrections of phase bias and range-weighting function

effect. Statistical examination showed that the imaged layer structure was thicker for a larger

radar beamwidth and such feature became more evident at higher altitude. This demonstrates

apparently the influence of radar beamwidth on practical performance of RIM. Second, the

scatterer anisotropy in the layer structure was examined by means of 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 detected by the oblique beams sometimes, 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 could be different, demonstrating one more capability of RIM to investigate fine-scale

features of the atmospheric layer structures.

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