- Open Access
MU radar observations of tropopause variations by using clear air echo characteristics
Earth, Planets and Space volume 50, pages 361–370 (1998)
We present in this paper the characteristics of clear air echoes revealed by the MU radar experiments in Shigaraki, Japan (34° 51′ N, 136° 06′ E). In particular, we study a relation between atmospheric stability, represented by Brunt Väisälä frequency squared, N2, and both the vertical echo power and the aspect sensitivity. On August 24–25, 1991, echo power was collected by steering the zenith angle of the antenna beam of the MU radar from the zenith to 28° with a step of 2°. Aspect sensitive echoes were detected in the lower stratosphere and some regions in the troposphere. We found that a ratio of vertical echo power to oblique echo power at 10° can represent the magnitude of aspect sensitivity. We compared profiles of both the vertical echo power and the aspect sensitivity with N2, inferred from a radiosonde sounding at the radar site. Cross correlation analysis indicates that a rapid increase of both vertical echo power and the aspect sensitivity near the tropopause usually coincides with a step-wise enhancement of N2.
We also analyzed four other MU radar observations, continued 4–5 days each, and obtained a statistical results that the mean CCF values between profiles of N2 and vertical echo power and the aspect sensitivity are 0.89 and 0.86, respectively. Their mean lag distance was about 71 m and 134 m, with a standard deviation of 77 m and 176 m, respectively. That is, the increase in the vertical echo power and the aspect sensitivity generally occurred slightly higher altitude relative to a sharp increase in N2. However, we also found some exceptional cases when the lag distance was as large as several hundred meters or even negative.
Balsley, B. B., The MST technique-a brief review, J. Atmos. Terr. Phys., 43, 495–509, 1981.
Fukao, S., T. Sato, T. Tsuda, S. Kato, K. Wakasugi, and T. Makihira, The MU radar with an active phased array system: 1. Antenna and power amplifiers, Radio Sci., 20, 1155–1168, 1985a.
Fukao, S., T. Sato, T. Tsuda, S. Kato, K. Wakasugi, and T. Makihira, The MU radar with an active phased array system: 2. In-house equipment, Radio Sci., 20, 1169–1176, 1985b.
Gage, K. S. and B. B. Balsley, On the scattering and reflection mechanisms contributing to clear air radar echoes from the troposphere, stratosphere, and mesosphere, Radio Sci., 15, 407–416, 1980.
Gage, K. S. and J. L. Green, Evidence for specular reflection from monostatic VHF radar observations of the stratosphere, Radio Sci., 13, 991–1001, 1978.
Gage, K. S. and J. L. Green, Tropopause detection by partial specular reflection with VHF radar, Science., 203, 1238–1240, 1979.
Gage, K. S. and J. L. Green, An objective method for the determination of tropopause height from VHF radar observation, J. Appl. Meteorol., 21, 1150–1154, 1982.
Gage, K. S., W. L. Ecklund, and B. B. Balsley, A modified Fresnel scattering model for parameterization of Fresnel returns, Radio Sci., 20, 1493–1501, 1985.
Green, J. L., K. S. Gage, and T. E. VanZandt, Atmospheric measurements by VHF pulsed Doppler radar, IEEE Transactions on Geoscience Electronics, GE-17, 1979.
Hocking, W. K., Measurement of turbulent energy dissipation rates in the middle atmosphere by radar techniques: A review, Radio Sci., 20, 1403–1422, 1985.
Hocking, W. K. and J. Röttger, Pulse length dependence of radar signal strengths for Fresnel backscatter, Radio Sci., 18, 1312–1324, 1983.
Hocking, W. K., S. Fukao, T. Tsuda, M. Yamamoto, T. Sato, and S. Kato, Aspect sensitivity of stratospheric VHF radio wave scatterers, particularly above 15 km altitude, Radio Sci., 25, 613–627, 1990.
Hocking, W. K., S. Fukao, M. Yamamoto, T. Tsuda, and S. Kato, Viscosity waves and thermal-conduction waves as a cause of “specular” reflectors in radar studies of the atmosphere, Radio Sci., 26, 1281–1303, 1991.
Holton, J. R., P. H. Haynes, M. E. McIntyre, A. R. Douglass, R. B. Rood, and L. Pfister, Stratosphere-Troposphere Exchange, Rev. Geophys., 33, 403–440, 1995.
Larsen and J. Röttger, VHF and UHF Doppler radars as tools for synoptic research, Bull. Amer. Meteor. Soc., 63, 996–1008, 1982.
Larsen and J. Röttger, Observations of frontal zone and tropopause structures with a VHF Doppler radar and radiosondes, Radio Sci., 20, 1223–1232, 1985.
Ottersten, H., Mean vertical gradient of potential refractive index in turbulent mixing and radar detection of CAT, Radio Sci., 4, 1247–1249, 1969.
Röttger, J., VHF radar observations of a frontal passage, J. Appl. Meteorol., 18, 85–91, 1979.
Röttger, J., Structure and dynamics of the stratosphere and mesosphere revealed by VHF radar investigations, Pure and Appl. Geophys., 118, 494–527, 1980.
Röttger, J., P. Czechowsky and G. Schmidt, First low-power VHF radar observations of tropospheric, stratospheric and mesospheric winds and turbulence at the Arecibo Observatory, J. Atmos. Terr. Phys., 43, 789–800, 1981.
Tatarskii, The effects of the turbulent atmosphere on wave propagation, U.S. Dept. of Commerce, 1971.
Tsuda, T., T. Sato, K. Hirose, S. Fukao, and S. Kato, MU radar observation of the aspect sensitivity of backscattered VHF echo power in the troposphere and lower stratosphere, Radio Sci., 21, 971–980, 1986.
Tsuda, T., P. T. Pay, T. Sato, S. Kato, and S. Fukao, Simultaneous observations of reflection echoes and refractive index gradient in the troposphere and lower stratosphere, Radio Sci., 23, 655–665, 1988.
Tsuda, T., T. E. VanZandt, M. Mizumoto, S. Kato, and S. Fukao, Spectral analysis of temperature and Brunt Väisälä frequency fluctuations observed by radiosondes, J. Geophys. Res., 96, 17265–17278, 1991.
Tsuda, T., T. E. VanZandt, and H. Saito, Zenith-angle dependence of VHF specular reflection echoes in the lower atmosphere, J. Atmos. Terr. Phys., 59, 761–775, 1997.
VanZandt, T. E. and R. A. Vincent, Is VHF Fresnel reflectivity due to lowfrequency buoyancy waves?, Handbook for MAP, Middle Atmosphere Program, University of Illinois, Urbana, 9, 78–80, 1983.
VanZandt, T. E., J. L. Green, K. S. Gage, and W. L. Clark, Vertical profiles of reflectivity turbulence structure constant: Comparison of observations by the Sunset radar with a new theoretical model, Radio Sci., 13, 819–829, 1978.
About this article
Cite this article
Hermawan, E., Tsuda, T. & Adachi, T. MU radar observations of tropopause variations by using clear air echo characteristics. Earth Planet Sp 50, 361–370 (1998). https://doi.org/10.1186/BF03352122
- Zenith Angle
- Cross Correlation Function
- Lower Stratosphere
- Tropopause Height