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A regional scale modeling analysis of aerosol and trace gas distributions over the eastern Pacific during the INTEX-B field campaign

Adhikari, B. and Carmichael, G. R. and Kulkarni, S. and Wei, C. and Tang, Y. and D'Allura, A. and Mena-Carrasco, M. and Streets, D. G. and Zhang, Q. and Pierce, R. B. and Al-Saadi, J. A. and Emmons, L. K. and Pfister, G. G. and Avery, M. A. and Barrick, J. D. and Blake, D. R. and Brune, W. H. and Cohen, R. C. and Dibb, J. E. and Fried, A. and Heikes, B. G. and Huey, L. G. and O'Sullivan, D. W. and Sachse, G. W. and Shetter, R. E. and Singh, H. B. and Campos, T. L. and Cantrell, C. A. and Flocke, F. M. and Dunlea, E. J. and Jimenez, J. L. and Weinheimer, A. J. and Crounse, J. D. and Wennberg, P. O. and Schauer, J. J. and Stone, E. A. and Jaffe, D. A. and Reidmiller, D. R. (2010) A regional scale modeling analysis of aerosol and trace gas distributions over the eastern Pacific during the INTEX-B field campaign. Atmospheric Chemistry and Physics, 10 (5). pp. 2091-2115. ISSN 1680-7316.

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The Sulfur Transport and dEposition Model (STEM) is applied to the analysis of observations obtained during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), conducted over the eastern Pacific Ocean during spring 2006. Predicted trace gas and aerosol distributions over the Pacific are presented and discussed in terms of transport and source region contributions. Trace species distributions show a strong west (high) to east (low) gradient, with the bulk of the pollutant transport over the central Pacific occurring between similar to 20 degrees N and 50 degrees N in the 2-6 km altitude range. These distributions are evaluated in the eastern Pacific by comparison with the NASA DC-8 and NSF/NCAR C-130 airborne measurements along with observations from the Mt. Bachelor (MBO) surface site. Thirty different meteorological, trace gas and aerosol parameters are compared. In general the meteorological fields are better predicted than gas phase species, which in turn are better predicted than aerosol quantities. PAN is found to be significantly overpredicted over the eastern Pacific, which is attributed to uncertainties in the chemical reaction mechanisms used in current atmospheric chemistry models in general and to the specifically high PAN production in the SAPRC-99 mechanism used in the regional model. A systematic underprediction of the elevated sulfate layer in the eastern Pacific observed by the C-130 is another issue that is identified and discussed. Results from source region tagged CO simulations are used to estimate how the different source regions around the Pacific contribute to the trace gas species distributions. During this period the largest contributions were from China and from fires in South/Southeast and North Asia. For the C-130 flights, which operated off the coast of the Northwest US, the regional CO contributions range as follows: China (35%), South/Southeast Asia fires (35%), North America anthropogenic (20%), and North Asia fires (10%). The transport of pollution into the western US is studied at MBO and a variety of events with elevated Asian dust, and periods with contributions from China and fires from both Asia and North America are discussed. The role of heterogeneous chemistry on the composition over the eastern Pacific is also studied. The impacts of heterogeneous reactions at specific times can be significant, increasing sulfate and nitrate aerosol production and reducing gas phase nitric acid levels appreciably (~50%).

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Jimenez, J. L.0000-0001-6203-1847
Crounse, J. D.0000-0001-5443-729X
Wennberg, P. O.0000-0002-6126-3854
Additional Information:© Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 19 July 2009 – Published in Atmos. Chem. Phys. Discuss.: 3 August 2009 Revised: 15 February 2010 – Accepted: 21 February 2010 – Published: 1 March 2010. We would like to thank the INTEX-B science team. This work was supported by a NASA grants (NNG04GC58G and INTEX-B). The heterogeneous chemistry portion was based on work done under a NSF grant (0613124). The authors would also like to acknowledge NOAA and Atmospheric Brown Cloud project for support of the Trinidad Head and Kathmandu measurements.
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Issue or Number:5
Record Number:CaltechAUTHORS:20100416-094948497
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Official Citation:Adhikary, B., Carmichael, G. R., Kulkarni, S., Wei, C., Tang, Y., D'Allura, A., Mena-Carrasco, M., Streets, D. G., Zhang, Q., Pierce, R. B., Al-Saadi, J. A., Emmons, L. K., Pfister, G. G., Avery, M. A., Barrick, J. D., Blake, D. R., Brune, W. H., Cohen, R. C., Dibb, J. E., Fried, A., Heikes, B. G., Huey, L. G., O'Sullivan, D. W., Sachse, G. W., Shetter, R. E., Singh, H. B., Campos, T. L., Cantrell, C. A., Flocke, F. M., Dunlea, E. J., Jimenez, J. L., Weinheimer, A. J., Crounse, J. D., Wennberg, P. O., Schauer, J. J., Stone, E. A., Jaffe, D. A., and Reidmiller, D. R.: A regional scale modeling analysis of aerosol and trace gas distributions over the eastern Pacific during the INTEX-B field campaign, Atmos. Chem. Phys., 10, 2091-2115, 2010.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17998
Deposited By: Ruth Sustaita
Deposited On:19 Apr 2010 15:47
Last Modified:03 Oct 2019 01:36

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