Super-refraction effects on GPS radio occultation refractivity in marine boundary layers

Abstract

With the combination of global coverage, high vertical resolution, and all-weather capability, GPS radio occultation (RO) is an emerging satellite remote sensing technique that can probe the atmospheric boundary layer (ABL) on a global basis. However, a systematic negative bias (commonly referred to as N-bias) remains in derived refractivity profiles in the ABL. In this paper we present the N-biases in COSMIC RO soundings with respect to ECMWF analyses, which show a seasonally varying pattern clustered over the oceans where super-refraction (SR) often occurs. A case study of coincident COSMIC RO and radiosonde sounding confirms that the N-bias is primarily caused by SR. We also show that the high-rate RO bending angle measurements can resolve the ABL top at a vertical resolution better than 100 m. A reconstruction method is applied to one case where SR occurs and significantly reduces the negative refractivity error in the ABL. Copyright © 2010 by the American Geophysical Union.