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| Titel |
Advances In Global Aerosol Modeling Applications Through Assimilation of Satellite-Based Lidar Measurements |
| VerfasserIn |
James Campbell, Edward Hyer, Jianglong Zhang, Jeffrey Reid, Douglas Westphal, Peng Xian, Mark Vaughan |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036500
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| Zusammenfassung |
| Modeling the instantaneous three-dimensional aerosol field and its downwind transport
represents an endeavor with many practical benefits foreseeable to air quality, aviation,
military and science agencies. The recent proliferation of multi-spectral active and passive
satellite-based instruments measuring aerosol physical properties has served as an
opportunity to develop and refine the techniques necessary to make such numerical modeling
applications possible. Spurred by high-resolution global mapping of aerosol source regions,
and combined with novel multivariate data assimilation techniques designed to consider these
new data streams, operational forecasts of visibility and aerosol optical depths are now
available in near real-time1.
Active satellite-based aerosol profiling, accomplished using lidar instruments, represents
a critical element for accurate analysis and transport modeling. Aerosol source
functions, alone, can be limited in representing the macrophysical structure of injection
scenarios within a model. Two-dimensional variational (2D-VAR; x, y) assimilation of
aerosol optical depth from passive satellite observations significantly improves the
analysis of the initial state. However, this procedure can not fully compensate for
any potential vertical redistribution of mass required at the innovation step. The
expense of an inaccurate vertical analysis of aerosol structure is corresponding errors
downwind, since trajectory paths within successive forecast runs will likely diverge with
height.
In this paper, the application of a newly-designed system for 3D-VAR (x,y,z)
assimilation of vertical aerosol extinction profiles derived from elastic-scattering lidar
measurements is described [Campbell et al., 2009]. Performance is evaluated for use with the
U. S. Navy Aerosol Analysis and Prediction System (NAAPS) by assimilating NASA/CNES
satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) 0.532 μm
measurements [Winker et al., 2009]. Inversion retrievals of aerosol extinction are performed
for one-degree latitudinal averages of CALIOP backscatter signal (thus matching the
horizontal resolution of NAAPS) by constraining total column transmission using the model
estimate of AOD at the corresponding wavelength. As such, this system serves as a
post-processing module predicated on newly-operational NAAPS aerosol analysis
fields that feature 2D-VAR assimilation of NASA Moderate Resolution Infrared
Spectroradiometer (MODIS) AOD observations [Zhang and Reid, 2006; Zhang et al.,
2008].
We describe the influence of 3D-VAR assimilation on NAAPS analyses and forecasts by
considering the physical evolution of Saharan dust plumes during their advection across
the tropical Atlantic basin. Steps taken towards characterizing spatial covariance
parameters that broaden the horizontal influence of information obtained along
the limited lidar orbital swath are discussed. This latter context is critical when
comparing the efficacy and impact of 3D-VAR assimilation with that of 2D-VAR
procedures, which benefit from passive observations with a relatively wide field-of-view
and, therefore, greater/more routine global coverage. With multiple satellite-lidar
projects either pending launch or in design stages, including the dual ESA missions
(AEOLUS and EarthCARE), we describe the potential impact of future 3D-VAR
assimilation activities; both for NAAPS forecast capabilities, and the anticipated growth
in aerosol transport modeling efforts at federal and cooperative global agencies
worldwide.
1 http://www.nrlmry.navy.mil/aerosol/
References
Campbell, J. R., J. S. Reid, D. L. Westphal, J. Zhang, E. J. Hyer, and E. J. Welton,
CALIOP aerosol subset processing for global aerosol transport model data assimilation, in
press, J. Selected Topics Appl. Earth Obs. Rem. Sens., December 2009.
Winker, D. M., M. A. Vaughan, A. Omar, Y. Hu, K. A. Powell, Z. Liu, W. H. Hunt, and
S. A. Young, Overview of the CALIPSO mission and CALIOP data processing
algorithms, J. Atmos. Oceanic. Technol., 26, DOI:10.1175/2009JTECHA1281.1,
2009.
Zhang, J., and J. S. Reid, MODIS aerosol product analysis for data assimilation:
assessment of over-ocean level 2 aerosol optical thickness retrievals, J. Geophys. Res., 111,
D22207, doi:10.1029/2005JD006898, 2006.
Zhang, J. and J. S. Reid, D. Westphal, N. Baker, and E. Hyer, A System for Operational
Aerosol Optical Depth Data Assimilation over Global Oceans, J. Geophys. Res., 113,
D10208, doi:10.1029/2007JD009065, 2008. |
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