Interim Review of the Subsonic Assessment Project Management, Science, and Goals (1997) / Chapter Skim
Currently Skimming:
Review of the SASS Questions and Responses
Review of the SASS Questions and Responses
Pages 11-24
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From page 11... ...
NEAR-FIELD INTERACTIONS Question: · Can;fluid dynamics and/or chemical processes in aircraft wakes alter properties of engine exhaust products or their deposition altitude to significantly influence the background atmosphere? Program · Develop efficient and accurate algorithms for thermodynamic, Response: physical, and chemical properties of wake and exhaust products between the engine exhaust plume and the location where interac tion is influenced only by background atmosphere.
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From page 12... ...
indicate that a higher pre-existing surface area suppresses new-particle nucleation, because of preferential condensation of precursors onto existing surfaces. Hence, measured particle concentrations in wakes (as observed by the Airborne Southern Hemisphere Ozone Experiment and Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/ MAESA)
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From page 13... ...
and Subsonic Assessment projects have supported several laboratory studies that have provided key kinetic information required for computer simulation of the effects of aircraft emissions on tropospheric and stratospheric ozone. The question quoted immediately above is indeed the crucial one, and the project responses will be important steps in the forthcoming SASS assessment.
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From page 14... ...
Attention should probably be focused first on heterogeneous chemistry associated with types of particles expected to be of significance to cloud-nuclei formation and radiative effects, such as black carbon and sulfuric acid (see Stolarski and Wesoky, 1993~. An activity in the area of aqueous chemical kinetics, as suggested in the SASS report, would also be of interest.
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From page 15... ...
An important element missing from the kinetic evaluation outlined in the SASS report is the program to reevaluate j-values (the apparent first-order decay coefficients related to photochemical processes) for the important light-absorbing species over the vertical extent of the troposphere, e.g., reactions of O3 to form O(iD)
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From page 16... ...
The rate parameters for the reactions that appear to be potentially important in the modeling studies should be examined and tested carefully with well-planned, pertinent laboratory measurements. ATMOSPHERIC OBSERVATIONS CHEMISTRY Questions: · What is NOx conversion time and odd nitrogen partitioning in lower stratosphere and upper troposphere?
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From page 17... ...
· Assemble existing NOx and NOy database and study budget information from past UT/LS measurement campaigns. 17 This SASS table entry identifies the key questions correctly, if rather generally.
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From page 18... ...
. Ensure that HOx, and all HOx precursors and sinks currently thought to be of importance in the upper troposphere, are included in proposed measurement programs.
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From page 19... ...
identifies radiative forcing as a "major area", and emphasizes that "experimental strategies will be developed so that process models are an integral part of the design, with each model selected to answer a key question defined in the mission plan." It notes further that this type of assessment will require prioritization of two types: the use of models and previous studies (including sensitivity studies) to focus measurement strategies on the highest-priority species, and determination of the conditions responsible for variability of selected trace gases, so that sampling aircraft will be flown in regions where the variability will be appropriately characterized.
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From page 20... ...
On the modeling side, decide what kind of modeling should be done to determine the sensitivities of radiative effects to the changes in cloud optical properties caused by changing aerosol properties, and what kind of modeling is needed to help design effective field experiments. Once these steps have been taken and they should hold for all measurement campaigns, not just aerosols the mission plan of any field experiment should state clearly how the results of the experiment will fulfill one of the needs identified.
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From page 21... ...
· As part of a more coordinated measurement strategy, determine what kind of measurements are required to establish the direct and indirect effects of aerosols from aircraft exhaust on radiative forcing and actinic flux. GLOBAL MODELING Questions: · What are predicted ozone changes and climatic impact associated with aviation ?
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From page 22... ...
. Such a data base could be used in conjunction with known aircraft emission characteristics to guide laboratory studies of heterogeneous chemistry on aerosols, or provide realistic aerosol scenarios for modeling studies.
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From page 23... ...
These first evaluations could be performed through collaboration between AEAP or SASS research groups and climate modeling groups at institutions such as NOAA's Geophysical Fluid Dynamics Laboratory, NASA's Goddard Institute for Space Studies, and NSF's National Center for Atmospheric Research. The GMI model is expected to be an important contributor to the next SASS assessment.
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From page 24... ...
· Put a high priority on GMI model evaluation, through comparisons of its results with those of separate modules, with available observations, and with results of other existing 3-D models. · Perform chemistry and transport sensitivity tests with existing 3-D chemical-transport models.
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