Geoscience Reference
In-Depth Information
6.4
Summary and Considerations
An adjoint observation impact system for a limited area model is a useful tool. The
system built for COAMPS is similar to other global systems in that it indicates
that radiosondes, aircraft data, and feature track satellite winds are all important
in reducing forecast error measured in a dry energy norm throughout the depth of
the troposphere. As new observation types such as satellite radiances are added to
NAVDAS, the impact system can be utilized to ensure the data is being properly
assimilated. A nice additional feature of this system is its ability to quantify the
impact of lateral boundary conditions as well as observational data.
The relative importance of observations can vary with location and error metric.
Choosing a suitable metric for a user's particular interest is key to properly
evaluating an observation's importance. The COAMPS observation impact system
contains much of the functionality inherent in both COAMPS and NAVDAS
(relocatability, varying grid configurations) as well as the ability to easily change the
volume over which the error is calculated and the metric. However, to investigate
smaller scale atmospheric features (
30 km) the nesting capability in the adjoint
model will need to be added to the system. Also, an option for the truth other than the
model's analysis field would be helpful for making comparisons between different
experiments. For example, the error could be calculated with respect to radiosonde
observations, but this will require more system development. As it stands, the
COAMPS adjoint observations impact system is a valuable asset and is already
providing important information on the performance of the entire atmospheric
modeling system.
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Acknowledgements This work was supported by the US Office of Naval Research's program
element 0601153N. Computational resources of the Department of Defense High Performance
Computing Modernization Program were vital to this work.
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