Improvement of the Tropospheric Correction for Doppler Data, Based on a Study of Upper Air Meteorological Data

摘要

The effect of tropospheric refraction on the Doppler shift has up to now been computed on the basis of a simple quadratic model of the height variation of the refractivity N of air. (N is defined as 100,0000 (n - 1), where n is the index of refraction.) The validity of this model in predicting the correct tropospheric range error for a vertically arriving signal is investigated here. The area under an N vs. height curve obtained from observed upper air data has been compared with the area under the corresponding quadratic profile (which starts at the same surface value of N), for 34 profiles observed at a variety of geographic locations, altitudes and seasons. The results show that the ratio between the tropospheric error due to the quadratic model and that due to the observed refractivity profile is in general not unity but is a linear function of the refractivity at the surface. This relation provides a simple correction factor for improving the computed tropospheric refraction correction for the Doppler shift. (Author)