Consistency of rocket and radar electron density observations : implication about the anisotropy of mesospheric turbulence |
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| Institution: | 1. Institute of Surface-Earth System Science, Tianjin University, Tianjin, China;2. USDA Hydrology and Remote Sensing Laboratory, Beltsville, MD, USA;3. Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA;4. Hydrological Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA;5. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster, Ministry of Education/International Joint Research Laboratory on Climate and Environment Change, NUIST, Nanjing 210044, China;6. Guangdong Provincial Key Laboratory of Urbanization and Geo-simulation, School of Geography and Planning, Sun Yat-sen University, Guangzhou 510275, China;7. School of Hydrology and Water Resources, Nanjing University of Information Science & Technology, Nanjing, China;8. School of Geographical Sciences, East China Normal University, Shanghai, China;9. Department of Physical Geography and Ecosystem Science, Lund University, Sweden;1. Earth System Science Interdisciplinary Center (ESSIC), University of Maryland, College Park, MD, 20740, USA;2. Code 617, Hydrological Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA;3. Department of Civil Engineering, University of Louisiana at Lafayette, P.O. Box 42991, Lafayette, LA, 70504, USA |
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| Abstract: | We report about a quantitative comparison of rocket observations of electron density fluctuations and simultaneous 53.5 MHz radar measurements that were obtained during the MAC/SINE campaign in northern Norway in summer 1987. Out of three rockets launched during the Tur-bulence/Gravity Wave salvo on 14 July 1987, two were flown during conditions that allowed a detailed investigation. For a large part of the data from these rocket flights it is found that the radar reflectivity is about 10 dB, enhanced over what would be expected from the rocket observations in the case of isotropic electron density fluctuations. The observations can be reconciled under the assumption of an anisotropic turbulence. Assuming a simple model spectrum for the electron density fluctuations, we derive a relation between the rocket and radar observations that covers the whole range from isotropic turbulent scatter to Fresnel scatter at horizontal density stratifications. For the observed dataset, an anisotropy which typically corresponds to a ratio of the horizontal to the vertical coherence length of about 10 is consistent with the comparison of rocket and radar observations. A similar anisotropy is found also from the observed aspect sensitivity of the radar echoes. The variation of the anisotropy with height and time shows an anticorrelation with the turbulence level of the mesosphere as deduced from the spectral width of the radar echoes. The anisotropy is found to maximize in heights where the electron density displays deep ‘bite-outs’. These depletions in the electron density were independently observed by a Langmuir and an admittance probe on board two of the rockets. |
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