Coupling of Horizontal, Vertical, and Temporal Resolving Power of a Satellite Temperature Sounder

Abstract

Satellite sensor optical systems now provide scan spots that are reasonably small and closely spaced compared with the horizontal scales of atmospheric variability that meteorologists might like to infer. Furthermore, geo-synchronous deployment of meteorological satellites provides the opportunity for almost arbitrarily frequent observational thus apparently increasing the temporal resolving power to almost an arbitrary degree. It is known, however, that the vertical resolving power of satellite sounding technology is poor compared with RAOBs. That is, finer scales of vertical atmospheric structure that can he resolved by radiosonde observations may not be detectable or resolvable by satellite radiance observations. In all retrieval methods, some external information or estimates of the ambient vertical structure must be included so that the apparent vertical resolution of the retrieval system is increased. In this study we show that horizontal and temporal resolving power of satellite soundings is closely coupled to the vertical resolving power. This is demonstrated both empirically and theoretically. Moreover, we show that improving the horizontal or temporal resolving power is not a simple matter of improving scan spot optics or increasing the frequency of observation. Either the ?vertical resolving power? of the satellite instrument itself must be improved, or the a priori external information must be extended to include correct horizontal and temporal structure. The vertical resolution limitation of satellite sounders has a direct effect on filtering out, or distorting, horizontal and temporal structural information.