National POES System (NPOESS) is scheduled to fly during the 2007-2010 period. The impact of future instruments such as Doppler Wind Lidar (DWL) need to be assessed with experiments using simulated observations. These experiments are known as Observing System Simulation Experiments (OSSEs). OSSE will provide a guideline for selection and design of the instrument.

This project is a collaboration among several organizations. Data assimilation will be performed mainly by a technology-neutral organization, the National Centers for Environmental Prediction (NCEP) and repeated by NASA/Data Assimilation Office (DAO). Simpson Weather Associates (SWA) and NOAA scientists are participating in the simulation of Doppler Wind Lidar (DWL) observations, and the National Environmental Satellite, Data and Information Service (NESDIS) will simulate both existing and future thermodynamic sounders. NASA/DAO will simulate conventional observations including ACARS and cloud track winds.

The first "nature run" (true atmosphere for the OSSEs) was provided by the European Centre for Medium- Range Weather Forecasts (ECMWF) for February 1993. The representativeness of the nature run was evaluated and found to be suitable to conduct OSSEs after some adjustment for low level cloud. Alternative nature run has been also prepared by NASA/DAO including summer and being evaluated.

Data impact of existing instruments in real and simulated data are compared for calibration. The impact test showed satisfactory similarity on TOVS 1B data and RAOB wind between real and simulated analysis. It is found that RAOB temperature may require some bias correction. Localized SST anomaly in late February caused large impact of 1B data in real analysis. These facts need to be considered when we asses the data impact of new instruments. It is noted that this OSSE can assess the data impact when SST variability is small.

For DWL OSSE, the bracketing OSSEs are being performed for various concepts to bound the technology neutral potential impact. Scanning: wavelength; data sampling strategies: various error characterizations are tested through the bracketing OSSE. The initial results show the impact is sensitive to error assignment. The results show that scanning is most important particularly in upper atmosphere. Penetration important in lower troposphere. Designing systematic errors, various representativeness errors, and large scale correlated errors for both existing instruments and DWL are being developed. .

OSSEs for atmospheric infrared sounder (AIRS) and cloud motion vectors are under preparation. OSSE for other instruments such as cross track infrared sounder (CrIS), conically scanning microwave imager/sounder (CMIS), advanced technology microwave sounder (ATMS) are also being considered.

Through OSSEs at operational centers, the operational data assimilation systems will be ready to handle new data in time for the launch. This process involves the evaluation of the operational load, the development of the data base and data-processing, and a quality control system. All of this development will accelerate the operational use of data from the future instruments.