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Colloquium - Sandu

Computational Tools for Chemical Data Assimilation
Virginia Tech University
3/11/2010
3:30pm-4:30pm

The task of providing an optimal analysis of the state of the atmosphere requires the development of novel computational tools that facilitate an efficient integration of observational data into models. We discuss several new computational tools developed for the assimilation of chemical data into atmospheric chemical transport models. The distinguishing feature of these models is the presence of stiff chemical interactions.

The variational tools presented in this talk include automatic code generation of chemical adjoints, properties of adjoints for advection numerical schemes, calculation of energy singular vectors and their use in placing adaptive observations. Data assimilation results using the 4D-Var method are shown for several real test problems to illustrate the power of the proposed methods.

We introduce a new method for modeling the background errors as autoregressive processes. The proposed approach is computationally inexpensive, captures the error correlations along the flow lines, and results in nonsingular background covariance matrices. We also discuss practical aspects of nonlinear ensemble Kalman data assimilation applied to atmospheric chemical transport models.

We discuss the implementation and application of the computational tools to three state of the art chemical transport models: STEM, CMAQ, and Geos-CHEM. We present numerical results obtained for simulations of atmospheric pollution with real data in North America, East Asia, and at a global level.

Adrian Sandu is an associate professor of Computer Science at Virginia Tech. He obtained the PhD in Applied Mathematical and Computational Sciences from The University of Iowa. Before joining Virginia Tech he held a postdoctoral research position at the Courant Institute of Mathematical Sciences and assistant professor position in the Department of Computer Science at Michigan Tech. Sandu's research interests are in the area of computational science and engineering.

Hosted by Xiao-Chuan Cai.

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