MU radar 1D, 2D, and 3D imaging of atmosphere and ionosphere
M. Yamamoto1, G. Hassenpflug2, S. Saito2, H. Luce3, S. Fukao4
- Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Kyoto, Japan
- National Institute for Information and Communications Technology, Tokyo, Japan
- LSEET-LEPI, Toulon-Var South University, Toulon, France
- Research Institute of Science and Technology, Tokai University, Tokyo, Japan
Radar imaging is a new technique for atmospheric and ionospheric radars. Resolution of the radars is very much enhanced by the imaging analysis with multiple-antenna and/or multiple-frequency observations. In addition to the flexible multi-beam capability of the MU radar, that is the original advantage of the system, the radar is now equipped with “MU radar imaging observation system” since March 2004. It consists of ultra multi-channel digital receiving subsystem that digitally demodulate 5 MHz IF signals at 29 channels (25 channels for all sub-groups of antenna, and 4 channels corresponding to analog signal-combiners). In addition to the digital receivers, we widened the radio-band allocation to 3.5MHz. We can now shift the radar frequency to at most five different frequencies at each pulse. This paper overviews recent results of our study utilizing the new feature of the MU radar. One most successful application is the study of thin-layered structure of the atmosphere with “1D imaging” in the frequency domain (Frequency radar Interferometric Imaging (FII) technique). Cumulus convection and Kelvin-Helmholtz instabilities (KHI) are clearly elucidated from observations with Capon method analysis (Luce et al, 2007). “2D imaging” in the spatial domain is very successful to investigate structures of ionospheric irregularities. The maximum entropy analysis with 19-channel signals (i.e., use all hexagonal sub-groups) is the standard observation mode (Saito et al., 2007). We can conduct the imaging observations at multiple-beam directions as well. We are now developing a “3D imaging” technique for the study of lower atmosphere. As it combines multi-channel and multi-frequency observations of at most 19-channel X 5-frequency, signal processing load is very heavy. From our study we will show an example of the KHI observed by the 3D imaging (Hassenpflug, et al., 2008).
Luce, H., G. Hassenpflug, M. Yamamoto, M. Crochet, and S. Fukao, Range-imaging observations of cumulus convection and Kelvin-Helmholtz instabilities with the MU radar, Radio Sci., 42, RS1005, 2007.
Hassenpflug, G., M. Yamamoto, H. Luce, and S. Fukao, Description of demonstration of the new Middle and Upper atmosphere Radar imaging system: 1-D, 2-D and 3-D imaging of troposphere and stratosphere, Radio Sci., in press, 2008.
Saito, S., M. Yamamoto, H. Hashiguchi, A. Maegawa, and A. Saito, Observational evidence of coupling between quasi-periodic echoes and medium scale traveling ionospheric disturbances, Ann. Geophys., 25, 2185-2194, 2007.