Use of the NASA GEOS-5 SEAC4RS Meteorological and Aerosol Reanalysis for assessing simulated aerosol optical properties as a function of smoke age

Cynthia Randles, ExxonMobil Research and Engineering Company, Annandale, United States, Arlindo da SIlva, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Peter Richard Colarco, NASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamics Laboratory, Greenbelt, MD, United States, Anton Darmenov, NASA Goddard Space Flight Center, Greenbelt, United States, Virginie Buchard, NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, United States, Ravi Govindaraju, Science Systems and Applications, Inc., Lanham, United States, Gao Chen, NASA Langley Research Ctr, Hampton, United States, Johnathan W Hair, NASA Langley Research Center, Hampton, VA, United States, Philip B Russell, NASA-Ames Research Center, Moffett Field, CA, United States, Yohei Shinozuka, Bay Area Environmental Research Institute Sonoma, Sonoma, CA, United States, Nick Wagner, NOAA/University of Colorado, Boulder, CO, United States and Daniel Lack, CIRES, Boulder, CO, United States
Abstract:
The NASA Goddard Earth Observing System version 5 (GEOS-5) Earth system model, which includes an online aerosol module, provided chemical and weather forecasts during the SEAC4RS field campaign. For post-mission analysis, we have produced a high resolution (25 km) meteorological and aerosol reanalysis for the entire campaign period. In addition to the full meteorological observing system used for routine NWP, we assimilate 550 nm aerosol optical depth (AOD) derived from MODIS (both Aqua and Terra satellites), ground-based AERONET sun photometers, and the MISR instrument (over bright surfaces only). Daily biomass burning emissions of CO, CO2, SO2, and aerosols are derived from MODIS fire radiative power retrievals. We have also introduced novel smoke “age” tracers, which provide, for a given time, a snapshot histogram of the age of simulated smoke aerosol. Because GEOS-5 assimilates remotely sensed AOD data, it generally reproduces observed (column) AOD compared to, for example, the airborne 4-STAR instrument. Constraining AOD, however, does not imply a good representation of either the vertical profile or the aerosol microphysical properties (e.g., composition, absorption). We do find a reasonable vertical structure for aerosols is attained in the model, provided actual smoke injection heights are not much above the planetary boundary layer, as verified with observations from DIAL/HRSL aboard the DC8. The translation of the simulated aerosol microphysical properties to total column AOD, needed in the aerosol assimilation step, is based on prescribed mass extinction efficiencies that depend on wavelength, composition, and relative humidity. Here we also evaluate the performance of the simulated aerosol speciation by examining in situ retrievals of aerosol absorption/single scattering albedo and scattering growth factor (f(RH)) from the LARGE and AOP suite of instruments. Putting these comparisons in the context of smoke age as diagnosed by the model helps us to revise assumed aerosol optical properties for an improved representation of aerosol radiative forcing.
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