Journal article
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
ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol.13(20), pp.10425-10444
2013
DOI: 10.5194/acp-13-10425-2013
Abstract
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.
Details
- Title: Subtitle
- 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
- Creators
- P E Saide - University of IowaG R Carmichael - University of IowaZ Liu - NSF National Center for Atmospheric ResearchC S Schwartz - NSF National Center for Atmospheric ResearchH C Lin - NSF National Center for Atmospheric ResearchA M da Silva - Goddard Space Flight CenterE Hyer - United States Naval Research Laboratory
- Resource Type
- Journal article
- Publication Details
- ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol.13(20), pp.10425-10444
- DOI
- 10.5194/acp-13-10425-2013
- ISSN
- 1680-7324
- Language
- English
- Date published
- 2013
- Academic Unit
- Civil and Environmental Engineering; Center for Global & Regional Environmental Research; Nursing; Chemical and Biochemical Engineering
- Record Identifier
- 9984231961402771
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