Potential Loss of Predictability in the Numerical Weather Prediction from the Reduced Spatial Coverage of the Polar-Orbiting Satellite Observing System

Abstract

Abstract To provide global coverage for the hyperspectral infrared (IR) and microwave (MW) sounders, the low-Earth-orbiting (LEO) satellite constellation is in operation in three temporally well-spaced sun-synchronous orbits. However, the satellite program can be altered as a result of aging satellites needing to deorbit and/or termination of the legacy program, resulting in less spatiotemporal coverage. In this study, to stress the contribution of IR and MW sounder observations from the LEO satellite constellation on numerical weather prediction (NWP) system performance, the change of the analysis impact is assessed under two assumptions: 1) the loss of the IR and MW sounder observations in each of three sun-synchronous orbits and 2) the loss of the secondary LEO satellite in two orbits, using a 2017 version of the National Centers for Environmental Prediction Global Forecast System (GFS). In the analysis verification, it is found that the analysis field is degraded due to the loss of the IR and MW sounders in each of the three primary orbits. In particular, the satellites in the afternoon orbit significantly contribute to improving the analysis as compared with the satellites in the other two orbits. In addition, the loss of the secondary satellite results in significant degradation of the analysis, resulting from reduced spatial coverage by the IR and MW sounders. These results suggest that the LEO satellite constellation, consisting of the LEO satellites in three primary sun-synchronous orbits, should be maintained in terms of the contribution to the NWP. Significance Statement Hyperspectral infrared (IR) and microwave (MW) sounders from low-Earth-orbiting (LEO) satellites significantly contribute to improving numerical weather forecasting. Nevertheless, the resiliency of the LEO satellite programs, operating in three sun-synchronous orbits, can be compromised by aging satellites needing to deorbit and/or termination of legacy satellite systems. Thus, to highlight the importance of the IR and MW sounder observations from LEO satellites in terms of numerical weather forecasting, we assessed the analysis impact of these observations with diverse satellite data availability scenarios. In the trial experiments, it is demonstrated that analysis performance is significantly degraded if the IR and MW sounders are lost, suggesting that the satellite programs carrying the IR and MW sounders should be maintained seamlessly in the future.