Radar estimations of atmospheric winds in the troposphere and lower stratosphere.

摘要

This dissertation deals with the estimation of atmospheric flow field parameters using the spaced antenna (SA) and spatial interferometer (SI) methods. In the first section, a computer simulation of scattering from inhomogeneities in the refractive index is used to compare the SA and SI methods for measuring winds in clear air both with and without turbulent fading. The results show that the SA analysis which is carried out in the time domain and the SI analysis which is carried out in the frequency domain are equivalent in terms of the information that the two methods yield. A data analysis method equivalent to full correlation analysis, which can be carried out in the frequency domain, is presented. The method is applied to model-generated data in order to extract the typical full correlation analysis output parameters such as the apparent and true velocities. The results obtained are consistent with the model input parameters. In the second section a statistical comparison of the SA and SI methods for estimating horizontal winds in the troposphere and the lower stratosphere is presented. The data analyzed were obtained with the Middle and Upper (MU) atmosphere radar from 1910 LT on June 29, 1990, through 0950 LT on July 2, 1990. At all heights, velocity estimates based on frequency domain data are within 4% of those based on time domain data. We conclude that frequency domain techniques provide an alternate method for estimating true horizontal velocity. Nevertheless, it is not clear that they offer any significant advantage over time domain methods. In fact, the results obtained indicate that the SI method for estimating horizontal velocity may be slightly more difficult to apply in practice. The final section presents an analytical evaluation of SA-based instrumental setups with the potential for estimating the vertical component of atmospheric vorticity from a single-radar location. Methods considered are the oblique spaced antenna (OAS) method and a modified SA system employing four vertically-pointed receiving antennas. Analogies are drawn between the Doppler and SA methods, and it is concluded that the two systems gather the same information when atmospheric turbulence is small and the reflectivity is uniform. Furthermore, it is concluded that under normal conditions measurement uncertainties will preclude the estimation of atmospheric vorticity from a single-radar location.