these accomplishments, the United States is not the world leader in global numerical weather prediction (NWP). Figure 3.1 indicates that the United States has made steady progress in global weather forecasting performance, but so have other countries.

Within the United States, however, the performance of the NOAA/NWS National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) is superior to the Navy Operational Global Atmospheric Prediction System (NOGAPS) operated by the Fleet Numerical Meteorology and Oceanography Center (FNMOC). In particular, the gap in model performance between NCEP and the European Centre for Medium-Range Weather Forecasts (ECMWF) has not narrowed in the past 15 years. The primary reason is the slow and sometimes ineffective transfer of achievements in the external research community to operational centers in the United States (R2O). Another reason is the lack of investment and progress in assimilating observations in advanced weather prediction models, which is also related to the slow R2O process in data assimilation. In addition, NCEP’s high-performance computing (HPC) capacity, despite recent upgrades, lags behind the capacities of many other major prediction centers around the world.3 The complexities associated with using a hydrostatic global model (GFS) and a variety of regional (nonhydrostatic and hydrostatic) models4 makes it very challenging to maintain and improve these prediction models and associated data assimilation schemes, particularly at the underresourced NCEP. As a consequence, the United States is not fully realizing the potential benefits of its substantial investments in observing systems.

Progress and Remaining Needs

As the horizontal grid spacing of models continues to decrease, especially to less than 10 km, hydrostatic models are no longer appropriate, and it is essential that global nonhydrostatic NWP models (Box 3.1) be coupled with ocean and land models. In fact, Japan’s global Non–hydrostatic Icosahedral Atmospheric Model (NICAM), which runs on the Earth Simulator5 computer, has reached horizontal grid spacing of 3.5 km (Satoh et al., 2008), which results in a spatial resolution 10 times greater (and an areal

3

These and other findings have been discussed in the recently completed external review of NCEP, the “2009 Community Review of National Centers for Environmental Prediction,” that was managed by the University Corporation for Atmospheric Research (UCAR). The executive summary of the NCEP review is included as Appendix B of this report.

4

The NCEP website describes the models operated by NCEP; see http://www.emc.ncep. noaa.gov/.

5

See http://www.jamstec.go.jp/esc/index.en.html.



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