Progress in Joint OSSEs Three Joint OSSE nature runs and simulation of observation

Observing system impact assessments using atmospheric simulation experiments are conducted to provide an objective quantitative evaluation of future observing systems and instruments. Such simulation experiments using a proxy true atmosphere, or Nature Run (NR), are known as Observing System Simulation Experiments (OSSEs, Arnold and Day 1986, Lord et al. 1997, Masutani et al. 2006). An internationally collaborative effort called Joint OSSEs was formed over the last two years in order to perform "full OSSEs" (Masutani et al. 2007). Various types of simulation experiments have been performed, but through full OSSEs, where a NR is produced by a free forecast run using a model different from the forecast model used for the data assimilation system (DAS), and calibratio