Hashiguchi, Hiroyuki

Yamamoto, Mamoru

Yamamoto, Masayuki K.

Kyoto University Research Information Repository

Title Range-imaging observation of turbulence in the tropicaltropopause layer by the Equatorial Atmosphere RadarAuthor(s)Yamamoto, Mamoru; Hashiguchi, Hiroyuki; Yamamoto,Masayuki K.CitationSustainable humanosphere : bulletin of Research Institute forSustainable Humanosphere Kyoto University (2009), 5: 6-6Issue Date2009-09-10URL http://hdl.handle.net/2433/182176RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityRECENT RESEARCH ACTIVITIESRange-imaging observation of turbulence in the tropical tropopause layer                 by the Equatorial Atmosphere Radar(Laboratory of Radar Atmospheric Science, RISH, Kyoto University)Mamoru Yamamoto, Hiroyuki Hashiguchi, and Masayuki K. Yamamoto    Observations of temperature, winds, and atmospheric trace gases suggest that the transition from thetroposphere to the stratosphere occurs in a layer, rather than at a sharp tropopause. In the tropics, this layeris often called the tropical tropopause layer (TTL). TTL has a bottom at 150 hPa, 355 K, 14 km (pressure,potential temperature, and altitude) and has a top at 70 hPa, 425 K, 18.5 km. TTL acts in many ways as agate to the stratosphere, and understanding all relevant processes is of great importance for reliablepredictions of future climate [1]. The 47-MHz atmospheric radar referred to as the Equatorial AtmosphereRadar (EAR) has been operated at Sumatra island, Indonesia (O.20S, 100.320E), and has revealed featuresof turbulence in TTL, which is expected to contribute airmass mixing there [2, 3]. In December 2009, wecarried out the observation campaign named Cloud experiment by Lidar and the Equatorial AtmosphereRadar (CLEAR). During CLEAR campaign, the EAR was operated with a frequency-domaininterferometric imaging (FII) mode to observe fine time and altitude variations of turbulence. Onpulse-to-pulse basis, the EAR changed transmitted frequencies from 46.5 to 47.5 MHz with 250 kHzspacing. Using phase difference of received signals caused by transmitted frequency difference andlocation of turbulence, altitudes of enhanced turbulence were deterrnined. Figure shows an example ofrange-imaging result in TTL. Wavy echoes with a period of about 7 minutes show presence of shearinstability, which causes airmass mixing. Previous study has shown that shear instability frequently occursaround the tropopause due to large wind shear [3], and the wavy echoes as shown in the Figure furtherprovide detailed information on observed scales of shear instability in TTL.  l5400  15200g lsooowv 14800Rkr 146oo  l4400  14200646260S856      Ol:45 Ol:50 Ol:S5 02:OO 02:05 02:10 02:15                                     LocalTirne           Figure. Time-altitude plot ofbrightness observed by FII the mode ofthe EAR.Acknowledgements    We thank Dr. Tomoaki Mega of RJSH for his great contribution in FII data analysis.References[1] Fueglistaler, S., A. E. Dessler, T. J. Dunkerton, I. Folkins, Q. Fu, and P. W. Mote, "Tropical tropopauselayer", Rev. Geophys., 47, RGIO04, doi:10.102912008RGOO0267, 2009.[2] Fujiwara, M., M. K. Yamamoto, H. Hashiguchi, T. Horinouchi, and S. Fukao, "Turbulence at thetropopause due to breaking Kelvin waves observed by the Equatorial Atmosphere Radar", Geophys, Res.Lett., 30, 1171, doi:1O.102912002GLO16278, 2003.[3] Yamamoto, M. K., M. Fujiwara, T. Horinouchi, H. Hashiguchi, and S. Fukao, "Kelvin-Helmholtzinstability around the tropical tropopause observed with the Equatorial Atmosphere Radar", Geophys. Res.Lett., 30, 1476, doi:10.102912002GLO16685, 2003.6

Range-imaging observation of turbulence in the tropical tropopause layer by the Equatorial Atmosphere Radar

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Range-imaging observation of turbulence in the tropical tropopause layer by the Equatorial Atmosphere Radar

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