Simulation of observation and Calibration for Joint OSSEs at NOAA

An internationally collaborative effort for full OSSEs, called Joint OSSEs, has been formed over the past three years. In Joint OSSEs common Nature Runs will be used by the various data assimilation systems at many institutes. The first Joint OSSE Nature Run has been produced by the European Center for Medium-Range Weather Forecasts (ECMWF). This Nature Run has a 13 month long period at T511 horizontal resolution with 91 vertical levels.

Full OSSE refers to a simulation experiment with a state-of-the-art Nature Run model significantly different from the NWP model used for data assimilation. This provides a truth independent of the data assimilation system and the Global Observing System data coverage and quality. In OSSEs, all the usual analysis and forecast verification metrics can be used to evaluate data impact, and the simulated data can be tested using several different data assimilation systems with only minor modification to the operational systems. Full OSSEs allow the quantitative assessment of the analysis and forecast impact if calibration is performed. Although a large initial investment is required for a full OSSE, using a full OSSE is the most reliable strategy today to assess the impact of prospective observing systems.

Ideally, all new instruments should be tested by OSSEs before they are selected for construction and deployment. OSSEs will also be important in influencing the design of the instruments and the configuration of the global observing system. While the instruments are being built, OSSEs will help prepare the DAS for the new instruments.

In a Full OSSEs, all major observations used for the DAS have to be simulated as a control observation besides the observation to be tested by OSSEs. Using the control observation, calibration of an OSSE verifies the simulated data impact by comparing it to a real data impact. Simulation of control observation and calibration are most significant initial investment for an OSSE before evaluating data impact of future instruments. NCEP and NESDIS volunteered to simulate control observations. Calibrations of OSSE system using NCEP global data assimilation system are being conducted at ESRL and NCEP. Extensive calibration experiments are conducted by ESRL as a part of OSSE to evaluate UAS.

Simulation of observations, particularly the simulation of radiance data, depends on the Radiative Transfer Model and sampling strategies used. The Flexible strategies which allow to coordinate limited resource in wide area of experts are proposed. A data base to allow for the testing of repeated simulations is being prepared and will be available from the NASA/GSFC/NCCS portal. Support for the simulation software is also provided.

Various OSSEs in progress will be introduced. OSSEs to evaluate proposed Doppler Wind Lidar, Unmanned Aircraft Systems, and additional GPS Radio Occultation (RO) observations, are in progress and other OSSEs are in preparation.

Calibration and simulation effort at NOAA is coordinated with work at NASA/GMAO.