Summary of full OSSEs at NCEP and Emerging Internationally Collaborative Joint OSSEs



  Joint OSSE team



Michiko Masutani(EMC), Erik Andersson (ECMWF),

Oreste Reale(NASA/GLA) Jack Woollen (EMC)
Dave Emmitt(SWA) Lars Peter Riishojgaard (JCSDA,NASA/GMAO)



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 which is called Nature Run (NR), are known as Observing System Simulation Experiments (OSSEs). 


NCEP has been working on OSSE for last several years using a NR with triangular truncation 213 (T213).  Since a Doppler Wind Lidar (DWL) is a most costly instrument, its evaluation has been a main focus in NCEP OSSEs.  In the first part of this seminar, a summary from OSSEs at NCEP that evaluated the data impact of DWL are presented.  The results show a potentially powerful impact from DWL, but also show that without a careful design of the observing system and a significant effort in developing the data assimilation system, DWL will not be utilized to its best potential.


Through the NCEP OSSE, it has been recognized that OSSEs are very labor intensive projects. It has been realized that the preparation of a Nature Run, including its evaluation, the simulation of observations from it, and its distribution consume a significant of amount of resources.  


Scientists from NCEP, NASA/GSFC, NESDIS, ESRL, and ECMWF discussed the design of common NRs and the first three Joint OSSE NRs have been produced by the European Center for Medium-Range Weather Forecasts (ECMWF).  The first NR has a 13-month-long period with three hourly data dumps at T511 horizontal resolution with 91 vertical levels.  During hurricane season and the US severe storm season, two 35-day-long runs with hourly data dumps at T799 horizontal resolution with 91 levels (T799NR) have been produced.


Now the collaboration and interest have been expanded to include KNMI, JMA, Mississippi State University, NRL-Monterey, NCAR and others.  We decided to call this effort the Joint OSSEs.  In Joint OSSEs common NRs will be used by the various DAS at many institutes.  By using the same NR, simulated observations can be shared and the results can be compared.  Extended international collaboration within the meteorological community is essential for timely and reliable OSSEs.


The second part of this seminar, Evaluation of Joint OSSE NRs and progress and plans for Joint OSSEs are presented.