Welcome to the
ARM Aerosol IOP
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Welcome to the
ARM Aerosol IOP
Home Page
Aerosol influences on shortwave radiation are substantial locally and globally and must thus be accurately represented in radiation transfer models and climate models.
To gain improved understanding and model-based representation of aerosol radiative influences an IOP (Intensive Observational Period) is planned to be conducted at the Department of Energy's Atmospheric Radiation Measurement (ARM) Southern Great Plains Site in north central Oklahoma, in May 2003.
This page provides a brief overview of the IOP and gives links to documents further describing this IOP.
Project Abstract
Aerosol influences on shortwave radiation are substantial locally and globally. An aerosol optical thickness of 0.1 results in an instantaneous decrease in direct normal surface irradiance of ca 100 watts per square meter, and (depending on particle size and single scattering albedo) a top of atmosphere forcing of ca 30 watts per square meter. Such optical depths are not uncommon at SGP. Aerosols also substantially influence the diffuse downwelling surface irradiance; the magnitude of this influence, and also of the vertical distribution of atmospheric heating, depends sensitively on the aerosol single scattering albedo.
Knowledge of pertinent aerosol properties is required to accurately represent aerosol forcing in models. ARM CART has been systematically measuring aerosol properties at the surface and limited measurements aloft from light aircraft. It is shown by lidar and in-situ measurements that much of the aerosol at SGP is aloft, often in layers that are decoupled from the surface, raising question of the representativeness of surface aerosol properties for these calculations. Vertical profiles of aerosol properties are key parameters required for the computation of radiative flux profiles. Detailed measurements of aerosol optical properties are required to characterize the aerosol optical, microphysical, and chemical properties at the surface and above the SGP site for accurately computing radiative fluxes. Such well-characterized data would permit a more detailed evaluation of the performance of radiative transfer models to compute flux profiles and heating rates.
The planned IOP will carry out a variety of closure experiments on aerosol optical properties and their radiative influence. Additionally, planned measurements of the aerosol chemical composition size distribution, to be conducted by investigators in the DOE Atmospheric Chemistry Program and Tropospheric Aerosol Program, will allow testing of the ability to reconstruct optical properties from these measurements. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.
Additional participants are sought for this IOP. Interested participants are invited to contact one of the investigators listed below.
Steve Schwartz (ses@bnl.gov)
Rich Ferrare (r.ferrare@larc.nasa.gov)
John Ogren (John.A.Ogren@noaa.gov)
Pete Daum (phdaum@bnl.gov)
Beat Schmid (bschmid@mail.arc.nasa.gov)
Steve Ghan (steve.ghan@pnl.gov)
A poster describing this IOP was presented at the 2002 ARM Science Team Meeting and may be viewed or downloaded as a pdf file.
A viewgraph presentation describing this IOP was discussed at the Aerosol Working Group meeting as part of the 2002 ARM Science Team Meeting and may be viewed or downloaded as a pdf file.
Further information is available in a Project Description.
This IOP will build on In-situ Aerosol Profiling (IAP) by light aircraft measurements, an ongoing activity at the ARM SGP site. Recent IAP results are summarized in Viewgraphs presented at the Aerosol Working Group meeting as part of the 2002 ARM Science Team Meeting and may be viewed or downloaded as a pdf file.
Experiments involving investigators in the DOE Atmospheric Sciences Program are outlined in Viewgraphs prepared for presentation at the 2002 Atmospheric Sciences Program meeting and may be viewed or downloaded as a pdf file.
Please contact us by email especially if you have interest in participating in this IOP.
Check back here frequently for further details or to get updates on planning this IOP.