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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
D02301,
doi:10.1029/2005JD005883,
2006
Chemical data assimilation of Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft measurements
Tianfeng Chai
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Gregory R. Carmichael
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Adrian Sandu
Department of Computer Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Youhua Tang
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Dacian N. Daescu
Department of Mathematics and Statistics, Portland State University, Portland, Oregon, USA
Abstract
In this paper, the four-dimensional variational (4D-Var) technique is applied to assimilate aircraft measurements during the
Transport and Chemical Evolution over the Pacific (TRACE-P) field experiment into a chemical transport model, Sulfur Transport
Eulerian Model, version 2K1 (STEM-2K1). Whether data assimilation would produce better analyzed fields is examined. It is
found that assimilating ozone observations from one of two independent flights improves model prediction of the other flight
ozone measurements, which are withheld as validation data. The adjusted initial fields after only assimilating the total reactive
nitrogen (NO
y
) observations lead to better predictions of NO, NO2, and PAN, based on their agreement with the withheld measurements. One experiment simultaneously assimilating the observations
of O3, NO, NO2, HNO3, PAN, and RNO3 demonstrates that the model is able to match those measurements well by changing the initial fields. In addition, the model
predictions of NO
y
improve significantly after assimilating the aforementioned multiple observation species, which are independent of the withheld
NO
y
measurements. In the paper, we also show that the key species whose initial mixing ratios would significantly affect the
agreement between model and measurements can be identified using adjoint sensitivity analysis. Such information can be used
to reduce the number of control variables in the 4D-Var data assimilation. To speed up the optimization process in the 4D-Var,
we enforce the concentration upper bounds through the limited memory–Broyden-Fletcher-Goldfarb-Shanno-B (L-BFGS-B) algorithm,
and this proves to be effective.
Received 15
February
2005;
accepted 28
September
2005;
published 17
January
2006.
Keywords: 4D-Var data assimilation;
chemical transport model;
TRACE-P.
Index Terms: 3315 Atmospheric Processes: Data assimilation; 3355 Atmospheric Processes: Regional modeling; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry.
Read Full Article (file size: 2027864 bytes) Cited by
Citation: Chai, T., G. R. Carmichael, A. Sandu, Y. Tang, and D. N. Daescu
(2006),
Chemical data assimilation of Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft measurements,
J. Geophys. Res.,
111,
D02301,
doi:10.1029/2005JD005883.
Copyright 2006 by the American Geophysical Union.
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