The objective of the Field Studies Session was to examine opportunities for cooperative participation in pending and future field programs: first to achieve a group consensus with regard to joint participation in major field efforts that are proposed for FY1996, and then to examine potential options for field studies in FY1997 and FY1998.
FY 1996 Field Programs
1. NOy Inlet Comparison
The motivation for this field program is to attempt to resolve the discrepancies found between aircraft measurements of NOy during the summer 1995 SOS field program. The source of these discrepancies has been hypothesized to be due to differences in the aerosol sampling efficiencies of the inlet systems that were employed on the various aircraft. These differences will be addressed by mounting all three inlets on the G-1 and simultaneously sampling the air from these inlets using BNL's three channel NOy detector. Measurements will be made in the Denver "brown cloud" which reportedly has a high concentration of aerosol nitrate. Flights will be made in the time period February 15-29, 1996, and will be based at Jeffco airport just south of Boulder, CO. Paul Doskey of ANL will take this opportunity to test his newly developed in-situ hydrocarbon analyzer.
Participants include:
Stephen Springston, et al., BNL
Y-N Lee, BNL
Marty Buhr, NOAA
Winston Luke, NOAA
Paul Doskey, ANL
Arrangements will be made by Stephen Springston of BNL.
2. Mexico City Studies
Opportunities for study of the pollution in the Mexico City basin were presented by Scott Elliot of Sandia National Laboratory. Mexico City has well known air pollution problems stemming from the vast amount of uncontrolled combustion that occurs in this area, which frequently gets trapped in the Mexico City basin under winter-time meteorological conditions. Apparently the motivation for the current study is to get a handle on the sources and composition of the aerosol that occurs during these episodes, although field studies could also be expanded to include studies of photochemical pollutants as well.
It was reported by Elliot and confirmed by Ricky Petty of DOE that the proposal to conduct this study is currently under review so a final decision regarding the proposed FY1996 preliminary field study as well as the planned full-scale program for FY1997 has not yet been made. Petty reported that the reviews of this program will be in shortly and that the status of the field programs should be known by early January.
Russ Dietz of BNL suggested a PFT (perfluorocarbon tracer) based experiment that could be used to identify the sources of various gaseous HC's in the Mexico City Basin. For example, if LPG sources were doped with PFT-1 and ambient air were doped with PFT-2 then one could estimate the leakage rate for LPG. Additional PFTs could be used to identify the HC contribution of large point sources to the Mexico City Atmosphere. The experiment could be entirely ground based, or could involve a combination of ground based and aircraft measurements.
The opinion of the working group was to wait and see whether the Mexico City proposal gets approved before having extensive discussions regarding the scientific and technical components of a Mexico City study.
3. NARSTO/NE
Pete Daum of BNL lead a discussion about potential ACP participation in the NARSTO/NE study that is currently planned for the Summer of 1996. The NARSTO acronym stands for the North American Research Strategy for Tropospheric Ozone. NARSTO/NE is a programs that pre-dates NARSTO, but is now considered to part of the NARSTO program.
The principal focus of NARSTO/NE is ozone formation in the Northeastern U. S. Ozone Transport Region (OTR) which region is defined as the eastern coastal states from VA through ME. The scientific issues of the program are very similar to the issues that drove the Summer 1995 Nashville program :
The influence of upwind O3 and O3 precursors
on OTR O3 concentrations
Whether O3 production is NOx or HC limited in
non-attainment areas.
The contribution of natural vs. anthropogenic HC to O3
concentrations in the OTR.
The influence of nocturnal transport and chemical
reactions on next day O3 concentrations
The effect of upwind sources of NOx and HC on the
amount of O3 formed in the OTR.
The facilities that NARSTO will tentatively deploy in the field during the intensive include:
Surface measurements of chemical species at a number
of sites in the Northeast.
Enhanced meteorology in the form of radiosondes
frequencies at NWS stations and other sites in the NE.
Wind profilers.
Two light aircraft equipped with NO/NOy, SO2,
O3, carbonyls, HC, and CO.
NOx vs. HC limitations to O3 production.
The NE U. S. is a much more intense source of NOx than
Central TN. More likely to encounter conditions where
O3 production is HC limited. How does this influence
potential O3 control strategies?
Nocturnal Chemistry and Transport-Where does material go?
How does it contribute to next day chemistry?
How do mixing and chemical processes associated with
nocturnal inversion layer break-up influence daytime
surface level O3 concentrations?
How are fresh emissions processed by photochemically aged
air-masses containing high concentrations of O3 and
photochemical end products.
What is the relative contribution of local and transported
VOCs to O3 production?
SPECIES
INSTRUMENT
SOURCE
SOy
modified pulsed flourescence
BNL
O3
uv absorption
PNL
NO, NO2, NOy
O3 chemiluminescence
BNL
PAN
GC/ECD
BCL
Peroxides
peroxidase/Fenton
SUNY/BNL
Aldehydes
scrubber/LC
BNL
Non-methane hydrocarbons
in-situ and cannister sampling
ANL
Radon and analysis
in-situ sampling
EML
CO
NDIR
BNL
HNO3
filter & scrubber
BNL
Aerosol Compostion-acidity and principal inorganic species
filter pack
BNL
Downwelling short wave irradiance
Eppley uv
PNL
Atmospheric state: T, P, dewpoint
standard aircraft instruments
PNL
Aerosol number densities and size distributions
PMS ASASP and FSSP
PNL
After significant discussion, the assembled working group agreed that participation in NARSTO/NE should be further explored. Carl Berkowitz of PNL and Peter Daum of BNL will meet with the Don Blumenthal of Sonoma Technology who is the technical coordinator of NARSTO/NE to explore how a mutually beneficial interaction between ACP and NARSTO/NE can be achieved. Results of our meeting with Blumenthal will be reported to potential participants.
If ACP decides to go ahead with this study, instrumentation will probably need to be ready for installation on the aircraft by May 1, 1996. Flights would be made for about a month during mid-summer, probably for the month of July.
Carl Berkowitz presented PNL plans for Summer of 1996. They are currently planning to continue exploration of chlorine chemistry using the TAGA mass spectrometer. Measurements are currently planned for June, 1996 and will be based at Suffolk County Airport in eastern Long Island. Stephen Springston of BNL has agreed to provide NOx/NOy measurements for the study. BNL will provide additional support for the effort as required.
If ACP goes ahead with participation in NARSTO/NE, Carl would like to make a series of flights to further explore breakup of the nocturnal boundary layer. These flights would be over a surface site measuring trace gas species (e. g. the site at Harvard Forest) and, as well, the site of one of the boundary layer profilers. The combination of winds and surface chemical measurements should allow for a more complete interpretation of mixing and consequent influence of trace species trapped near the surface at night to the evolution of boundary layer O3 concentrations during the day.
ANL plans for Summer 1996 were presented by Paul Doskey and Weigang Gao. They are interested in obtaining vertical profiles of isoprene concentrations at several places in the NE during whatever summer flights are planned. The purpose of these measurements is to validate/develop the ability of a model using satellite measurements of vegetation type and cover can be used to predict isoprene concentrations. Isoprene is a reactive hydrocarbon emitted by trees, and can be a significant source of the HC necessary for O3 production in the ambient atmosphere. Measurements would be required at several different times of day, and at several locations.
Potential Field Programs for FY 1997
1. ACE-II (Aerosol Characterization Experiment)
Steve Schwartz asked that the ACP community consider participation in the summer 1997 ACE-II program. The overall objectives of this program are to enhance understanding of the combined physical and chemical processes that control aerosol properties that are relevant to radiative forcing and climate. The experiment, which will be conducted in the Summer of 1997 will be based in the Eastern North Atlantic with an operational area bounded on the north by the Azores and to the south by the Canary Islands and extending eastward to southern Europe and northern Africa. Steve suggested that an appropriate role for ACP would be to use the G-1 to measure the input to the ACE-II project region from the North American continent, by flying N-S transects between, for example, Halifax, N. S. and Bermuda under relevant sets of meteorological conditions.
Considerable discussion ensued with regard to whether ACP should participate in ACE-II. It was pointed out that in consideration of the prevailing meteorological systems over the North Atlantic during the summer, that it will be very difficult to make the case that air sampled over the proposed flight tracks actually constitutes input to the ACE-II project region. It was suggested that if ACP does participate in ACE-II that it have a set of scientific objectives that can be addressed by the G-1 data alone. No consensus emerged with regard to ACP participation in ACE-II.
2. SOS (Southern Oxidant Study)
Lenny Newman discussed future plans for the Southern Oxidant Study program. This program, with which ACP has been collaborating for the past 5 years culminating with the Summer 1995 Nashville study, is just starting its second five year funding cycle. Lenny makes the case that ACP collaboration with SOS has been very productive in the past, and that we should strongly consider continuing this collaboration in the future. Future field programs are not yet defined, but may include a study of a coastal urban area to examine the effects of sea breeze circulation on urban photochemistry, or a study of a southwestern urban area such as Dallas, Several other potential project areas and foci are also under consideration.
Potential Field Studies Beyond 1997
Pete Daum asked that the group consider the possibility of an aerosol focused field program for the future . Such a study is motivated by the recognition of the climate community of the potential cooling effect of anthropogenic aerosols. The argument being that the climate has not warmed to the extent predicted on the basis of increased CO2 because concurrent increases in anthropogenic aerosols have mediated the effect by enhanced direct reflection of solar radiation back to space by the aerosol particles themselves, or indirectly by alteration of cloud albedo.
Potential issues that might be considered in such a study include:
Aerosol Properties
Composition
Size Distribution
Optical Effects
Direct
Indirect
Formation and Growth Processes
Precursor concentrations
Influence of substances such as NH3It was pointed out that all of these issues are probably not addressable in single field program. For example, it might make sense to couple characterization of aerosol microphysical properties with studies of their optical effects since the properties and optical effects are obviously linked, and to study aerosol formation processes in a separate experiment.
It was also suggested that if the focus of a field program were aerosol optical effects, it would make a lot of sense to consider doing the experiment over the ARM site in OK to take advantage of radiometric and meteorological measurements at the site.
The group was cautioned that any aerosol focused experiment will require substantial upgrading of the aerosol sampling capabilities of G-1, and that this cannot be accomplished without the organized co-operative effort of the ACP community.