Potential Gaps in the Satellite Observing System Coverage: Assessment of Impact on NOAA’s Numerical Weather Prediction Overall Skills

Abstract

Abstract The current constellation of environmental satellites is at risk of degrading due to several factors. This includes the following: 1) loss of secondary polar-orbiting satellites due to reaching their nominal lifetimes, 2) decrease in the density of extratropical radio-occultation (RO) observations due to a likely delayed launch of the Constellation Observing System for Meteorology, Ionosphere and Climate-2 (COSMIC-2) high inclination orbit constellation, and 3) the risk of losing afternoon polar-orbiting satellite coverage due to potential launch delays in the Joint Polar Satellite System (JPSS) programs. In this study, the impacts from these scenarios on the National Oceanic and Atmospheric Administration (NOAA) Global Forecast System skill are quantified. Performances for several metrics are assessed, but to encapsulate the results the authors introduce an overall forecast score combining metrics for all parameters, atmospheric levels, and forecast lead times. The first result suggests that removing secondary satellites results in significant degradation of the forecast. This is unexpected since it is generally assumed that secondary sensors contribute to system’s robustness but not necessarily to forecast performance. Second, losing the afternoon orbit on top of losing secondary satellites further degrades forecast performances by a significant margin. Finally, losing extratropical RO observations on top of losing secondary satellites also negatively impacts the forecast performances, but to a lesser degree. These results provide a benchmark that will allow for the assessment of the added value of projects being implemented at NOAA in support of mitigation strategies designed to alleviate the negative impacts associated with these data gaps, and additionally help NOAA to define requirements of the future global observing system architecture.