Aerosol Workshop — June 2-3, 1997

Panel A: Direct Aerosol Forcing

J. Penner (Facilitator), Y. Kaufman (Recorder), T. Nakajima, L. Stowe, I Sokolik

Panel A Summary by Recorder

(Yoram Kaufman)

The satellite record can be used to document the spatial distribution of optical thickness and derived fluxes (which may be more accurate). Comparison with models at specific locations can reveal problems in the satellite record and models.

Field data can be used to improve the satellite inversion, even to some degree for past times.

Past data can be improved by use of several channels of TOMS and AVHRR. Note that the AVHRR and TOMS instruments need to characterized regarding their spectral response and other characteristics for the sake of long records.

There are a number of issues about the direct radiative forcing that need to be investigated, for example, the refractive index of dust aerosols.

The data record will be continued and improved with the new satellites, which can also be used for comparisons with the AVHRR and TOMS retrievals.

Yoram Kaufman suggestions are specified in the following box:

Form Forcing and Satellite Teams

  1. Form teams of 10-15 scientists to deal with aerosol forcing for specific types/regions; do not separate direct and indirect effects. Use data from past concentrated field experiments (SCAR, TARFOX, ACE) for detailed information on aerosol and cloud properties. NASA can select the team leaders directly or via the NRA.
  2. Form a team for analysis of satellite data, applying algorithms globally (AVHRR, TOMS, GOES/Meteosat, POLDER, OCTS, MODIS, MISR ...). There should be joint membership between this and other teams.
  3. Include foreign participants, providing only travel funds.

Tasks for the Forcing Teams

  1. Derive changes in aerosol forcing for the past two decades from models, with validation using satellite data and ground/air measurements. It is not clear that this is possible; let's see if good proposals are generated.
  2. Derive changes in aerosol forcing for the past two decades using satellite data. Models and in situ measurements will supply coefficients in the analysis of satellite data. Derive separately the direct forcing, indirect forcing and the combined forcing, and see if they add up. Each method could be applied by different investigators. Examples of applications could include:
    • Total forcing computed from the spectral angular radiance using models that convert radiance to fluxes, based on cloud coverage and surface conditions.
    • Indirect forcing obtained from correlation between aerosol loading and cloud properties for several cloud temperatures. It can be derived from satellite data or from aircraft data (e.g., SCAR). Examine whether the effect on clouds has changed with time, and whether it depends on cloud type and meteorological conditions. Compute the integrated effect for each region and month.
  3. Analyze new satellite data (MODIS, MISR, POLDER ... including CERES for fluxes) to derive the present forcing and its dependence on the aerosol concentration. Compare this future aerosol concentration with the results for earlier times. Check whether the processes change with time (e.g., aerosol spectral properties, cloud dependence on aerosols).
  4. Analyze changes in sources with time (e.g., population, urbanization/industrialization, fire count) and the corresponding aerosol optical thickness and cloud properties.

Tasks for Satellite Teams

  1. Characterize the properties of the satellite data as a function of time.
  2. Develop algorithms to derive aerosol properties and cloud properties simultaneously, making use of pathfinder projects and Nakajima's effort. Apply more than one algorithm for the sake of comparison.

Workshop Homepage * Agenda * Summary
Sessions: 1, 2, 3, 4, 5, 6
Panels: A, B, C, D * Participants