The influence of the signal-to-noise ratio upon radio occultation inversion quality

Abstract. In this paper, we investigate the influence of the signal-to-noise ratio (SNR) upon the radio occultation (RO) retrieval quality. We perform two series of numerical simulations: (1) with artificial RO data and, (2) with real COSMIC observations. We superimpose the simulated white noise with varying magnitudes upon both types of the observation data and evaluate the response in the statistics. The statistics use the reference fields of the analyses of European Centre for Medium-Range Weather Forecasts (ECMWF). Our simulations indicate that the effect of additive white noise has a threshold character: the influence of the noise is very low up to some threshold, but when the threshold is exceeded, the influence increases dramatically. Another conclusion is that, given RO observations of fair quality, the enhancement of the SNR cannot be expected to provide significant improvement in retrieval quality.