Coupled Air/Ocean Model Data Assimilation Researcher

Peraton is seeking a Coupled Air/Ocean Model Data Assimilation Researcher at Stennis Psace Center in MS.  The Navy Earth System Prediction Capability (ESPC) provides the Navy with global operational forecasts of the atmosphere and ocean, in its present weakly coupled form, the models for the ocean and atmosphere are coupled but the data assimilation (DA) step itself is not. The DA corrections do not extend across the air-sea interface, introducing imbalances in the boundary layer acoustic and evaporative ducts that degrade predictions of sonar and radar detection coverage. NRL is working to introduce a strong coupling between the atmosphere and ocean assimilation components, therefore enhancing the overall capability of the system to predict these surface acoustic and evaporative ducts. Implementing a strongly coupled system brings in complications of how to express these localization schemes across the two different media. Length scales of features in the atmosphere tend to larger scales than the features they are correlated with in the ocean.

This project seeks to better parametrize the effect of atmospheric observations on the ocean state and vice versa, by developing a wavelet-based localization scheme for the ensemble correlations. The wavelet transform decomposes a signal into a multiresolution representation of scales in wavelet space. The localization scheme will then be computed in wavelet space, as scales from the atmosphere and ocean will be standardized through the wavelet transform. Ensemble DA methods are sensitive to computational cost due to the large arrays involved and this project should reduce that cost with the compression inherent with the wavelet transform. Wavelet compression of the signals is achieved by thresholding redundant scales before calculation of the localization to reduce the problem size and increase the efficient use of computational resources.

Responsibilities will include:

• Write generalized Fortran code to use the wavelet transform that will be compatible with existing Navy DA systems.
• Write specialized code to use the generalized code on an ensemble-based DA system.
• Build a toy program of a fully coupled DA system to verify the localization scales computed by the wavelet-based method and to verify the capture of features used to describe acoustic and evaporative ducts.
• Evaluate success by measuring the improved assimilation of temperature, salinity, and humidity profiles in the fully coupled system compared against generalized localization schemes by reduced root mean square error, and increased forecast skill.
• Evaluate the capability of the wavelet compression by measuring reduced run time of the localization process and computational storage size.
• Present results at academic conferences.
• Publish results in peer reviewed journals.

PhD in an Engineering or Applied Science Field.

• Must have coding experience in Fortran and C++.
• Must have experience with Linux, Shell Scripting, and High Performance Computing (HPC).
• Must be knowledgeable in Ocean Modeling, Fourier Analysis, and wavelet-base data assimilation systems.
• Must be familiar with U.S. Navy standard ocean models.
• Ability to obtain a Secret Clearance
• Experience working in a Department of Defense research facility strongly preferred.

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