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Detailed Reference Information |
Pan, C.J. and Rao, P.B. (2002). Low altitude quasi-periodic radar echoes observed by the Gadanki VHF radar. Geophysical Research Letters 29: doi: 10.1029/2001GL014331. issn: 0094-8276. |
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We report here on the low altitude quasi-periodic (LQP) radar echoes from low latitude sporadic E layer (Es) observed by the Gadanki (13.5¿N, 79.2¿E; geomagnetic latitude 6.3¿N) VHF radar. The LQP echoes occurred both during daytime and nighttime and are confined to a slowly descending layer with a thickness of about 2--4 km in the height range of 90--100 km. The periods are found to range from tens of seconds to less than about 3 minutes. The Doppler velocities vary over a range of -20 to +20 m/s during daytime and 0 to 10 m/s during nighttime and are known to be sensitive to the layer height, being dominated by the effect of zonal electric field above and meridional neutral wind below a height of ~97 km for the type 2 irregularities <Krishna Murthy et al., 1998>. The spectral widths are found to be of the order of 50 to 75 m/s during daytime and 30 to 60 m/s during nighttime. The LQP echoes reported here are similar to that observed recently over midlatitudes <Rao et al., 2000; Urbina et al., 2000>, but distinctly different from the widely reported quasi-periodic (QP) echoes occurring at higher altitudes (>100 km). The observations are discussed briefly in terms of the potential source mechanisms. |
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Abstract |
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Keywords
Hydrology, Precipitation, Meteorology and Atmospheric Dynamics, Precipitation, Meteorology and Atmospheric Dynamics, Climatology, Meteorology and Atmospheric Dynamics, Paleoclimatology |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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