空间GPS无线电掩星反演大气参数方法及其应用

给出了空间无线电掩星反演大气参数的原理及其误差估计方法,介绍了国内外在该领域的研究进展。并针对该技术的一些特点,指出了若干尚需解决的问题。

INVERSION OF TERRESTRIAL ATMOSPHERIC PARAMETERS USING SPACEBORNE GPS RADIO OCCULTATION AND ITS APPLICATION

 The principle and error assessments of the application of spaceborne GPS radio occultation to terrestrial atmosphere inversion are reviewed and the recent developments on this discipline are summarized. Based on the established theory and data from GPS/MET mission, researchers from University Corporation for Atmosphere Research in US have presented their results that the accuracy of GPS occultation inversion for atmospheric temperature is averagely one Kelvin between 5 km and 40 km altitude. If temperature is obtainable from an independent source, water vapour pressure profiles can be derived, which is quite interesting to meteorologists; however it is still tentative to derive water vapor profile because before reliable results for water vapor profiles are attainable, the multipath effect on signal, which is difficult to model, should be mostly removed. Currently, inversion accuracies suffer much from signal to noise ratio limiting, so inflight GPS receivers for obtaining lower signal to noise ratio GPS signal are required in order to get more effective data for inverting atmospheric parameters. As far as the characteristics of the technique in question are concerned, we raise some problems which remain to be settled. They include: how to narrow and interpret the differences of temperature derived by GPS occultation method and routine technique, such as Radiosonde; how to get atmospheric parameters in the lower atmosphere, say, under 5 km altitude, and in the upper atmosphere, say, above 40 km; how to decorrelate temperature and water vapour pressure so as to get reliable water vapour pressure profiles; how to take into account the ignored “higher-order”term, which can be expressed as the integral of the dot-product between gradient of refractivity and velocity of GPS signal with respect to the geocenter, integrating along the signal propagation path; how to overcome the singularity of integrand at the lower integration limiting when the Abel transform is adopted to produce the refractivity profiles.