NASA Technical Reports Server (NTRS) 19950017854: The atmospheric effects of stratospheric aircraft: A fourth program report

256 Pages·10.7 MB·English

by  NASA Technical Reports Server (NTRS)

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NASA
Reference
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Publication
1359
January 1995
The Atmospheric Effects
of Stratospheric Aircraft:
A Fourth Program Report
(NASA-RP-1359) THE ATMOSPHERIC N95-Z4274
EFFECTS 0# STRATOSPHERIC AIRCRAFT:
A FOURTH PROGPAM REPORT (NASA)
Unc|as
234 p
HI/45 0044073

NASA
Reference
Publication
1359
January 1995
The Atmospheric Effects
of Stratospheric Aircraft:
A Fourth Program Report
Edited by:
Richard S. Stolarski
Goddard Space Flight Center
National Aeronautics and Space
Administration
Greenbelt, MD
Howard L. Wesoky
Office of Aeronautics
Headquarters
National Aeronautics and Space
Administration
Washington, DC

Contents
Program Summary
Richard Stolarski and Howard Wesoky ............................................................ 1
2 Stratospheric Photochemistry, Aerosols and Dynamics Expedition
Steve Wofsy and Richard Stolarski ................................................................. 15
3 Heterogeneous Chemistry in the Atmosphere: An Assessment of Current Status
A. R. Ravishankara et al.................................................................................. 35
4 Assessment Model Workshop Summary
Jose Rodriguez .............................................................................................. 115
5 Aircraft Exhaust Plume and Wake Vortex Near-Field Interactions
William Grose et al....................................................................................... 131
6 High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft
Research Summaries ..................................................................................... 145
Appendix: List of Reviewers ................................................................................... A-1

Chapter I
Program Summary
Richard S. Stolarski
Goddard Space Flight Center
National Aeronautics and Space Administration
Greenbelt, MD
Howard L. Wesoky
Headquarters
National Aeronautics and Space Administration
Washington, DC

INTRODUCTION
This report marks two important milestones in NASA's recent aviation-related atmospheric
research. First, as discussed in later chapters, a new effort has been initiated as an element of the
NASA Advanced Subsonic Technology Program to investigate the possible atmospheric impact of
subsonic aircraft, particularly the growing commercial fleets. This Subsonic Assessment (SASS)
has been combined with the ongoing Atmospheric Effects of Stratospheric Aircraft (AESA)
(Stolarski and Wesoky, 1993a) element of NASA's High-Speed Research Program (HSRP)
(Williams, 1993) to establish the Atmospheric Effects of Aviation Project (Wesoky et al., 1994).
Therefore, future AESA progress reports, which focus on the effects of supersonic or high-speed
civil transport (HSCT) aircraft, will be accompanied by similar information on subsonic aviation.
The second important milestone is related directly to AESA. In late 1992, NASA asked the
National Research Council (NRC) of the National Academy of Sciences to provide an evaluation of
AESA. A panel of ten experts, including four from Europe, received extensive briefings from
AESA managers and investigators before an interim assessment report (Albritton et al., 1993) was
transmitted to them in June 1993.
This chapter begins with a discussion of the interim assessment and the NRC review. The
AESA response to that report (NRC, 1994) is then discussed and related to the 1995 assessment
which will end Phase I of the program. Finally, the major uncertainties expected to remain in the
post-1995 time frame are discussed and the initiatives for the AESA Phase II program plan are
presented.
1993 INTERIM ASSESSMENT FOR AESA PHASE I
The 1993 AESA interim assessment evaluated the potential impact of a fleet of HSCT aircraft
on stratospheric ozone. The result depends on size of fleet, Mach number (cruise altitude), and
emission index (El) for NOx (El, g of equivalent nitrogen oxides as NO2 per kg of fuel).
Although a realistic jet engine suitable for the proposed fleet of supersonic civil aircraft will not be
available until after the turn of the century, laboratory and theoretical studies show great promise
for the development of efficient and safe engines with El as low as 5. For an estimated fleet of 500
Mach 2.4 aircraft flying realistic routes, the calculated effects on the column of ozone is a depletion
of less than 1percent for E1 of 5 and as much as 2-3 percent for E1 of 15. Table 1 shows the range
of predictions included in the interim assessment, along with newer Mach 2.0 results.
Table 1. Assessment Model Predictions
SCENARIOS ASSESSMENT MODEL
HSCT FLEET HSCT EMISSIONS INDEX 3ACKGROUNE COLUMN OZONE CHANGE (%}, 40 TO 50 DEG N LATITUDE
MACH NO. gm equlv NO2/kg fuel Cl(ppbv} AER CAMED GSFC LLNL NCAR OSLO
1.6 5 3.7 -0.04 0.69 -0.11 -0.22 -0.01 0.04
1.6 15 3.7 -0.02 0.48 -0.07 -0.57 -0.60 0.15
2.0 3.7 -0.29 -0.48
2.0 15 3.7 -0.63 -1.45
2.4 5 3.7 -0.47 0.38 -0.29 -0.58 -0.26 -0.47
2.4 15 3.7 -1.20 -0.45 -0.86 -2. I0 -1,80 -1.30
2.4 15 2.0 -2.00 -l. I0 -1.30 -2.70 -230 -1.90
2.4 45 3.7 -5.50 -2.80 -4.10 -8.30 -6.90 -3.50
It was also reported that an increasing body of experimental evidence clearly demonstrates that
the lower stratospheric chemistry of NOx is strongly influenced by heterogeneous reactions
occurring on the surfaces of sulfate aerosols. This implies that nitrogen compounds are less active
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towards ozone than they would otherwise be, and that ozone loss in the lower stratosphere is
dominated by hydrogen and chlorine oxides.
In its recent evaluation report, the NRC (1994) commended AESA for, on the whole,
performing good work which has enhanced understanding of atmospheric chemistry, but also
recommended that more work will be needed to allow fully informed decisions concerning the
environmental compatibility of HSCT aircraft. In response to these recommendations, NASA has
augmented the AESA effort as an element of the Phase II HSRP (Williams, 1993; Shaw et al.,
1993) that is developing HSCT technology.
In the opinion of the NRC Panel, the three remaining key uncertainties in the AESA studies are:
(see page 5, NRC, 1994)
• Dispersion of HSCT emissions in the stratosphere
• Physical and chemical properties of stratospheric aerosols and their precursors
• Possible climate effects of the HSCT fleet
Many AESA program elements were noted to have contributed to a reduction in uncertainties.
However, some changes in program structure and emphasis were advised. Among those for
which the Panel recommends augmentation of effort are: (see page 6, NRC, 1994)
• Three-dimensional (3-D) (i.e., altitude, latitude, and longitude) chemical assessments, with
more attention to incorporating data from s.atellites
• Parameter space sensitivity studies with two dimensional (2-D) (i.e., altitude and latitude)
models
• Examination of HSCT effects on climate, especially those pertaining to water vapor and
ozone
• Organic chemistry in the upper troposphere
• Additional independent studies of plume/wake processes
INITIAL RESPONSE OF AESA TO THE NRC EVALUATION
Guidance of the NRC Panel is first being used to focus on activities which can significantly
improve the assessment to be provided at the end of AESA Phase I in 1995. In particular, a
number of activities have been initiated to address modeling issues brought out in the NRC report.
These are being mostly accomplished within the scope of the existing research efforts of current
AESA investigators. They include:
A step-by-step model intercomparison. This has been started as a chemistry-only
intercomparison with just two of the 2-D models. The intercomparison will then be
expanded to include other 2-D models and the trajectory chemistry model used for
interpretation of aircraft data. The next step in this comparison will be to define a chemical
benchmark using an accurate Gear-type code to integrate the chemical equations at several
fixed points with specified inputs. Two detailed radiative models have been intercompared
and shown to give virtually identical results (Kawa, personal communication). These will
be used as a standard to resolve several outstanding issues in the calculation of photolysis
rates in existing 2-D models. 2-D or 3-D chemistry and radiation codes will be tested
against these standards.
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