武汉中层、低热层大气角谱中频雷达观测

武汉中频雷达是利用中层、低热层中电子密度不均匀体的散射来测量大气的水平风场和电子密度剖面。雷达在计算风场的过程中可得到一些该层大气中电子密度不均匀体的寿命和空间尺度等参量值。结合这些参量和大气风场值可计算得到大气的角谱。其计算方法包括全相关分析技术的谱宽法和空间相关法。前者计算的值被认为是大气角谱的上限值。应用这两种方法,利用2001年2月9日武汉中频雷达的观测数据,对武昌上空中层、低热层大气的角谱进行了计算。结果得到大气角谱随高度增加略微增加,如在68km为6°,90km达最大为11°,其平均值为9.2°。利用2001年2月4—10日86km高度上的数据,得到一个7天平均的日变化曲线,发现大气角谱值在本地夜晚最小。

OBSERVATIONS OF THE MESOSPHERE AND LOWER THERMOSPHERE ANGULAR SPECTRUM WITH AN MF RADAR AT WUHAN

Atmospheric angular spectrum is one of the significant features of the atmospheric radio scatterrers. Echoes scattered from the electron irregularities in the mesosphere and lower thermosphere can be used to measure horizontal winds and electron densities with the MF radar at Wuhan. Configured with spaced antenna mode and full correlation analysis techniques, Wuhan MF radar can measure the life time and scale of the irregularities routinely as well. Using these data, the atmospheric angular spectrum can be estimated with both a spectral width method and a space correlation method. The former method gives the upper limit of the angular spectrum, while the latter gives estimations close to the true angular spectrum. The observational data on February 9, 2001 are used to estimate the angular spectrums with these two methods. Results show that the angular spectrum increase slightly with increasing height with a minimum of 6 at 68km and a maximum of 11 at 90km. Its mean value is 9.2.Data at 86km level from Feb. 4 to 10, 2001 are used to give mean daily variations that have a maximum in the daytime and minimum in the nighttime.