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| Titel |
Aerosol optical depth assimilation for a size-resolved sectional model: impacts of observationally constrained, multi-wavelength and fine mode retrievals on regional scale analyses and forecasts |
| VerfasserIn |
P. E. Saide, G. R. Carmichael, Z. Liu, C. S. Schwartz, H. C. Lin, A. M. da Silva, E. Hyer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 20 ; Nr. 13, no. 20 (2013-10-29), S.10425-10444 |
| Datensatznummer |
250085771
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| Publikation (Nr.) |
 copernicus.org/acp-13-10425-2013.pdf |
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| Zusammenfassung |
| An aerosol optical depth (AOD) three-dimensional variational data
assimilation technique is developed for the Gridpoint Statistical
Interpolation (GSI) system for which WRF-Chem forecasts are performed with
a detailed sectional model, the Model for
Simulating Aerosol Interactions and Chemistry (MOSAIC). Within GSI, forward AOD and adjoint
sensitivities are performed using Mie computations from the WRF-Chem optical
properties module, providing consistency with the forecast. GSI tools such as
recursive filters and weak constraints are used to provide correlation within
aerosol size bins and upper and lower bounds for the optimization. The system
is used to perform assimilation experiments with fine vertical structure and
no data thinning or re-gridding on a 12 km horizontal grid over the region
of California, USA, where improvements on analyses and forecasts is
demonstrated. A first set of simulations was performed, comparing the
assimilation impacts of using the operational MODIS (Moderate
Resolution Imaging Spectroradiometer) dark target retrievals to
those using observationally constrained ones, i.e., calibrated with AERONET
(Aerosol RObotic NETwork) data. It was found that
using the observationally constrained retrievals
produced the best results when evaluated against ground based monitors, with
the error in PM2.5 predictions reduced at over 90% of the stations
and AOD errors reduced at 100% of the monitors, along with larger overall
error reductions when grouping all sites. A second set of experiments reveals
that the use of fine mode fraction AOD and ocean multi-wavelength retrievals
can improve the representation of the aerosol size distribution, while
assimilating only 550 nm AOD retrievals produces no or at times
degraded impact. While assimilation of multi-wavelength AOD shows positive
impacts on all analyses performed, future work is needed to generate
observationally constrained multi-wavelength retrievals, which when
assimilated will generate size distributions more consistent with AERONET
data and will provide better aerosol estimates. |
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