An Overview on the Development of the Observing System Simulation Experiments (OSSEs)

The development, maintenance and use of a new space-based observing system is very expensive. There is usually a significant time delay (around 6 months to 1 year) from the completion of the instrument development and configuration to operational applications. It is very important to quantitatively evaluate the impacts and applications of the current and future observing system in advance to deploy it. The evaluation of the observing systems includes the instrument determination, orbit selection, constellation configuration, the applications to the numerical prediction and etc. The Observing System Simulation Experiments (OSSEs) is a sensitive experiment to study the value of new or proposed observing systems and the impacts of their data. An OSSE is designed to use the data assimilation method to investigate the potential impact of the future observing systems. In an OSSE, a nature run (NR) is generated by a very high temporal and spatial resolution numerical weather prediction (NWP) model output. The rapid development of NWP models and satellite data assimilation bring challenges as well opportunities to the development of OSSEs. Quick-OSSE, Hybrid OSSE and other forms of OSSE are extended to effectively evaluate future observing systems.