In a 1994 National Research Council report, "Atmospheric Effects of Stratospheric Aircraft: An Evaluation of NASA's Interim Assessment", the assessment panel's key issues for better determining the atmospheric effects of stratospheric aircraft, particularly on ozone, were presented

Brune, William H.

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FINAL REPORT
PARTICIPATION AS MISSION SCIENTIST FOR THE
SPADE II MISSION
/
Dr. William H. Brune
February 1, 19993 -January 31, 1999
The Pennsylvania State University
503 Walker Building
Depar_ent of Meteorology
University Park, PA 16802
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"Participation as Mission Scientist for the SPADE 11 Mission"
William H. Brune
Department of Meteorology
505 Walker Building
Pennsylvania State University
University Park, PA 16802
Research Objectives
In a 1994 National Research Council report, "Atmospheric Effects of Stratospheric
Aircraft: An Evaluation of NASA's Interim Assessment", the assessment panel's key
issues for better determining the atmospheric effects of stratospheric aircraft, particularly
on ozone, were presented. One of the three key issues is summarized in the statement:
• "Uncertainties in the dispersion characteristics related to effluents in the
lower stratosphere."
A strategy for studying the transport of air through the stratosphere has evolved over the
last ten years. It involves the measurements of long-lived trace chemicals that have
different sources and sinks in the stratosphere and thus different lifetimes. By examining
the distributions of these long-lived tracers and by comparing the mixing ratio of one
tracer against another measured simultaneously, characteristics of transport between the
troposphere and stratosphere and within the stratosphere can be determined. These
observed characteristics then become benchmarks against which global stratospheric
model calculations can be compared.
The NASA ER-2 aircraft has had the instrumentation to measure a suite of long-lived
tracers since the SPADE mission in 1992-1993. ER-2 measurements have been made
since then during the campaigns: ASHOE/MAESA (1994); STRAT (1995-1996); and
POLARIS (1997). Unfortunately, the ER-2 can not probe the atmosphere above 20 km, a
region of great interest for transport and chemistry. Space-borne instrumentation has also
produced distributions of long-lived tracers, but the frequency, location, timing, and
measurement precision was generally inadequate to provide the measurements required to
determine the transport characteristics. Hence, another method for probing the middle
stratosphere.
The information gap is filled by Observations from the Middle Stratosphere (OMS).
OMS is a measurement strategy that uses instruments, carried aloft by large helium-filled
balloons, to sample long-lived trace chemical distributions in the middle and lower
stratosphere. In this strategy, existing balloon-bome remote sensing instrumentation
would be used. However, to get the high precision and accuracy required, a new payload
would have to be built that had in situ sampling instruments, similar to those on the ER-2.
The overall OMS science objectives is to define atmospheric transport processes
important for the stratospheric dispersion of HSCT effluents as a first step toward
reducing uncertainties in predicting HSCT effluent effects. Two questions are:
• Will effluents be carriedhigher into the stratosphereby entering the tropics
andrising?
• Wherein thestratospherewill theeffluent stayandfor how long?
A roughview of thetransportof interestto theAESA programis shownin theschematic.
S EQUATOR N
In 1994, I was asked to be the project scientist overseeing the development and
deployment of a new payload that contained in situ sampling instruments (called OMS in
situ). We began work in earnest on the design of the payload and the operational goals at
a workshop in Washington DC in January 1995. The operational objectives that we
defined were:
Measurement of a select group of long-lived tracers from 30 km to the troposphere, at
high, middle, and tropical latitudes, to define mixing, tropical ascent, and the mean
age-of-air, a surrogate for HSCT effluents.
Long-lived tracers with different tropospheric trends, seasonal cycles, and destruction
rates and methods act as "clocks" of atmospheric motion.
Scatter plots of two long-lived tracers are different in the tropics and middle latitudes.
These differences are used to examine mixing between the tropics, midlatitudes, and
high latitudes.
Frequent simultaneous sampling of the same air mass by in-situ balloons, remote-
sensing balloons, satellites, and the ER-2 to develop a large, cohesive observational
data base that will be used to test assessment models.
lntercomparisons give confidence in different measurement techniques.
These operational objectives were met during the course of the next three years.
OMS in situ payload
The payload for OMS in situ consists of instruments to measure long-lived gases that
trace atmospheric motions. This payload consists of instruments to measure CO/, CFC-
11, SF6, CH4, N20, H20, 03, pressure, and temperature: chemical species with a wide
variety of trends, lifetimes, and seasonal variations. The principal investigators and their
organizations are: CO2 (Boering and Wofsy, Harvard University); NzO and CI-I4,
(Webster, JPL); N20 and CI-I4 (Loewenstein, Ames Research Center); CFC-11, CFC-113,
SF6, (Elkins, NOAA CMDL); O3, P, and T (Margitan, JPL); H20 (Oltmans, NOAA
CMDL). The redundancy in the N20 measurement is required because both of these
instruments were new and the NzO measurement is so important to the mission. All of
these instruments are based on earlier designs or have been tested on aircraft. They were
placed on a balloon gondola that is being constructed at JPL by James Riccio and his
colleagues.
Other remote sensing payload already existed. A listing of the payloads and their
measurement capabilities is given below.
Balloon-borne instruments:
• OMS in-situ payload instruments
high accuracy, high precision, subkilometer altitude resolution
• JPL ALIAS II (N20, CH4)
* NASA ARC Argus (N20, CH4)
• Harvard University CO2 (CO2)
• NOAA CMDL LACE (CFC-11, SF6, CFC-12, CFC-113)
• JPL Ozone (03, P, and T)
• NOAA CMDL Water _'apor (H20, P, and T)
JPL Mark IV solar infrared absorption
good accuracy, good precision, 2 km altitude resolution
• measures: H20, CH4, N20, CFC-11, CFC-12, SF6, 03, CO2, CO, NO, NOz,
HNO3, HC1, HF, CF4, and many more
Harvard FIRS-2 far-infrared spectrometer
good accuracy, good precision, 2 km altitude resolution
• measures: O3, N20, HNO3, NO2, N205, H20, OH, HO2, HCI, and more
• U.of Denver CAESR infrared thermal emission
good accuracy, good precision, medium altitude resolution
• measures:O3, HNO3, CH4, CFC-I 1, CFC-12, N2Os,aerosol
JPL SLS submillimeter limb sounder
good accuracy, good precision, medium altitude resolution
• measures: 03, N20, HNO3, HO2, CIO, HCI
A history of recent balloon flights:
To meet the operational objectives, a number of flights were planned in a short time
interval. All flight operations were conducted by the National Scientific Balloon Facility,
in Palestine, Texas. We worked closely with them to optimize the probability of
achieving the operational objectives, and hence the scientific goals.
A total of 70MS in situ flights and 4 remote sensing payload flights were conducted
from June 1996 to May 1997. This feat is truly remarkable and probably unprecedented
for a payload of the complexity of the OMS in situ payload. A listing of the flights and
how they met the operational objectives is given below.
• June 1996, Ft. Sumner, New Mexico.
• OMS in situ engineering test flight - first flight
• Test new instruments and gondola.
• September 1996, Ft. Sumner, New Mexico.
• OMS in situ first midlatitude flight - transport.
• ER-2 flight to New Mexico. Intercomparison.
• Mark IV flight 1 week later. Intercomparison.
• February 1997, Juazeiro do Norte, Brazil.
• OMS in situ first tropical flight -transport.
• Tropical observations of unprecedented quality.
• April - May 1997, Fairbanks, Alaska. (ADEOS).
• ADEOS intercomparison - photochemistry and transport.
• Mark IV, FIRS-2, SLS, CAESR, 03. Aerosol.
• ER-2 POLARIS flights. Intercomparison.
• Two launches 8 days apart.
• June - July 1997, Fairbanks, Alaska.
• OMS in situ high latitude - transport.
• ER-2 POLARIS flights. Intercomparison.
• Mark IV - photochemistry, transport, & intercomparison.
• November 1997, Juazeiro do Norte, Brazil.
• OMS in situ second and third tropical flights.
• Later time, different stratospheric conditions
• May, 1998, Ft. Sumner, New Mexico
• OMS in situ midlatitude flight
• Observations of the highest quality ever obtained
OMS results that impact the assessment of stratospheric ozone loss from HSCTs.
The scientific results from these flights has had the anticipated impact on the
understanding of stratospheric transport. The key findings are summarized below.
OMS tracer-tracer relationships are distinctly different in the tropics, midlatitudes,
and high latitudes, as also seen from the ER-2 and from space (ATMOS).
These observations confirm the utility of tracer-tracer relationships for defining
stratospheric transport and for testing transport in the HSR assessment models.
OMS tracer-tracer relationships confirm ASHOE/MAESA and STRAT ER-2
observations that lower-stratospheric quasi-horizontal mixing is rapid just above the
tropopause and 30% of tropical air came from the midlatitude lower stratosphere.
Thus HSCT effluents could get into the lower tropical stratosphere in greater
amounts than currently calculated.
Ascent rates, entrainment rates, and mean age of the air in the tropical stratosphere
(18 - 30 km) are being determined from OMS measurements of CO2, SF6, N20, and
CH4. The mean age of tropical stratospheric age is 2-4 years. Above 25 km, mixing
with midlatitude air appears to be substantial.
Thus HSCT effluents will ascend to at least 25 km where they will mix out into middle
latitudes.
• The mean age of air in the summertime polar stratosphere is 5-6 years, Mixing is
slow in the stagnant air, as seen by the presence of polar filaments.
Thus HSCT effluents could remain longer in stratospheric regions where they are
effective in destroying ozone.
How do assessment models compare to OMS, STRAT, and ATMOS observations?
Overall, the assessment models do not match the observed:
• mixing into the tropical lower stratosphere;
• lifetime (probably mixing) in the tropical stratosphere above 25 km;
• stratospheric mean age-of-air at high latitudes.
The goal was to have these results available to impact the 1998 assessment of the impact
of stratospheric aircraft on stratospheric ozone and climate. This goal was accomplished.
Numerous publications from OMS in situ and remote sensing payloads as well as the
results are essential components that support the findings of the assessment. This
assessment - Assessment of the Effects of High-Speed Aircraft in the Stratosphere: 1998
- is currently in press.
Publications resulting from this effort and those of the OMS investigators
Several publications are in preparation and will be submitted this year. Two that are
already submitted are:
Andrews, A. E., K. A. Boering, B. C. Daube, S. C. Wofsy, E. J. Hinsta, E. M. Weinstock,
and T. P. Bui, Empirical age spectra for the lower tropical stratosphere from in situ
observations of CO2: Implications for stratospheric transport, J. Geophys. Res.,
submitted, 1999.
Jost, H., M. Loewenstein, L. Pfister, J. J. Margitan, A. Y. Chang, R. J. Salawitch, and H.
A. Michelsen, Filaments in the tropical middle stratosphere: Origin and age
estimation, Geophys. Res. Lett., accepted, 1998.


Participation as Mission Scientist for the SPADE 2 Mission

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