A Technical Description of the NAVDAS Adjoint System
Memorandum rept. for Jul 2002-Jan 2004
NAVAL RESEARCH LAB MONTEREY CA
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This report provides a technical description of the adjoint code for the NRL Atmospheric Variational Data Assimilation System NAVDAS. The output of the NAVDAS adjoint is an array that contains the sensitivity of a user-defined forecast cost function with respect to the complete set of observations assimilated by NAVDAS at a particular time. The input for the NAVDAS adjoint is an analysis sensitivity vector provided by the adjoint of a forecast model such as NOGAPS. Step by step guidelines for using the NAVDAS adjoint system to compute observation sensitivity are given. The basic theory of observation sensitivity is outlined, and features of the adjoint code and main subroutines are described in detail. Examples of observation sensitivity applications are provided, including the impact of innovations on short-range forecast error, and targeted observing.
- Computer Programming and Software