资源环境科技发展态势分析平台

In this study, we estimate atmospheric turbulence in the free atmosphere in terms of the Thorpe scale (L-T) and eddy dissipation rate (epsilon) using U.S. high vertical-resolution radiosonde data over 4 years (September 2012 to August 2016) at 68 operational stations. In addition, same calculations are conducted for 12 years (October 2005 to September 2017) at four stations among the 68 stations. These high vertical-resolution radiosonde data have a vertical resolution of approximately 5 m and extend to an altitude of approximately 33 km, and thus, turbulence can be retrieved in the entire troposphere and lower stratosphere. There are thicker and stronger turbulent layers in the troposphere than in the stratosphere, with mean epsilon values of 1.84 x 10(-4) and 1.37 x 10(-4) m(2)/s(3) in the troposphere and stratosphere, respectively. The vertical structure of epsilon exhibits strong seasonal variations, especially in the upper troposphere and lower stratosphere, with the largest epsilon values in summer and the smallest in winter. In the horizontal distribution of epsilon, large epsilon is seen mainly above the mountainous region in the troposphere, but this pattern is not seen in the stratosphere. Although epsilon is estimated by the square of L-T multiplied by the cube of the Brunt-Vaisala frequency (N), the regions of large epsilon are matched with large L-T regions where N is relatively small. For the time series of epsilon near the tropopause for 12 years at four stations, an annual variation is prominent at all stations without significant interannual variations. There is, however, a slightly increasing trend of epsilon at two stations.