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Ground-based observations of the middle atmospheric density, pressure and temperature profiles can be obtained by lidar. A single-wavelength Rayleigh lidar system based at Hefei (31°N,117°E) has been used to measure the atmospheric density, pressure and temperature in the middle atmosphere in night in the altitude range from about 25 to 40 km. The structure of Rayleigh lidar system, principles of middle atmospheric density, pressure and temperature measurement which is based on the Rayleigh scattering theory and method to retrieve atmospheric density, pressure and temperature profiles were described respectively. This instrument combined a 500mW Nd:YAG laser transmitter with a 0.4 m receiver mirror to observe returns from altitudes between 25km and 40km.The lidar observed atmosphere density, pressure and temperature profiles are validated through comparison with the measure data provided by sounding balloon. According to the data from actual measurement, the inversion of the vertical distribution of middle atmosphere density, pressure and temperature are in good agreement with the result of sounding balloon. Generally, in the altitude range 25 to 40 km, the density ratio profile of Rayleigh lidar to the sounding balloon density fluctuates between 0.98 and 1.10, the pressure ratio profile of Rayleigh lidar to the sounding balloon is between 0.99 and 1.06 and the deviation of the temperature is less than 6 k.
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