New Amazon Fire Data / Other Earth Results to be Revealed at AGU Meeting

John Bluck

NASA Ames Research Center, Moffett Field, CA

(Phone: 650/604-5026 or 604-9000)

E-mail: jbluck@mail.arc.nasa.gov

AGU Moscone Center press room, San Francisco, CA

(Phone: 415/905-1007, general AGU information during meetings)

NOTE TO EDITORS: 00-83AR

Three to five times higher carbon emissions from annual burning in the
Amazon went into the air in the early 1990s than was reported by similar,
recent studies, according to a new NASA report slated for presentation
Dec.16, at the American Geophysical Union (AGU) meeting at the Moscone
Convention Center in San Francisco.

The scientific journal “Atmospheric Environment” will also print full
results of the new NASA Amazon research. Principal author Christopher
Potter of NASA Ames Research Center, Moffett Field, CA, will present the
data at the AGU meeting at 9:30 a.m. PST, Saturday, Dec. 16, in room 122
Moscone Center. Almost 30 NASA Ames scientists will participate in a wide
range of Earth science presentations, ranging from ozone depletion to the
effects of dust in the atmosphere. A web page summarizes their reports at:
http://amesnews.arc.nasa.gov/factsheets/FS_ARC_0012_13.html

“Our study’s results indicate carbon emission estimates from annual burning
in the eight states of the Brazilian Legal Amazon in the early 1990s are
three to five times higher than reported in similar, recent studies that
implied the region tends towards a net-zero annual source of emissions from
terrestrial carbon,” Potter said. His study is part of the NASA-supported
“Large Scale Biosphere-Atmosphere Experiment in Amazonia,” an international
research project led by Brazil. Co-authors are Vanessa Brooks Genovese and
Matthew Bobo of NASA Ames, as well as Steven Klooster and Alicia
Torregrosa, both of California State University Monterey Bay, Seaside, CA.
The co-authors’ web pages contain more information at:
http://geo.arc.nasa.gov/sge/casa

The AGU meeting will take place from Dec.15 – Dec.19, and several hundred
scientists from government, universities and private industry plan to
attend.

Later, Genovese will talk about simulations of selected sites in Alaska’s
Denali National Park, which suggest that the past 50-year climate trends of
warming temperatures may shift the local ecosystem from dominance by
coniferous evergreen trees to a mixture of evergreens and deciduous,
broad-leafed trees. She will make this presentation at 11:30 a.m., Dec. 16
in Moscone Center room 124.

Ames resident scientist John Livingston, a contractor with SRI
International, Menlo Park, CA, will co-chair a “poster session” Dec.16, at
8:30 a.m. in Moscone’s Hall D about a summer 2000 study of Saharan dust
carried by winds to the Caribbean region. Researchers who studied Saharan
airborne dust used a sunphotometer during 21 science airplane flights to
measure how much sunlight penetrates smoke and other aerosols. In the dust
study, as in other Earth science studies, once satellite data are
calibrated with ground (or “ground truth”) and airborne observations,
scientists can use the satellite data to develop useful regional and global
computer pictures of atmospheric or ground conditions.

Many NASA Ames scientists also contributed to more than 10 AGU
presentations dealing with various aspects of ozone loss over the Arctic
and Antarctic. The Earth’s ozone layer protects life below from harmful
ultraviolet radiation coming from the Sun that can lead to the formation of
skin cancers. Scientists have observed unusually low levels of ozone over
the Arctic during recent winters.

Ames scientist Hansjurg Jost is scheduled to make a presentation concerning
the mixing of atmospheric gases related to ozone depletion. The talk will
be Dec.16 at 9:40 a.m. in Moscone room 131. Jost will discuss results from
data gathered by the NASA ER-2 high altitude aircraft that carried
instruments which measured nitrous oxide, carbon dioxide, ozone and
temperatures in regions of the Arctic stratosphere during the winter of
1999 -2000 to determine how these gases mix. The Arctic stratosphere is
located from about 6 miles to 30 miles above Earth. Researchers found that
various air masses have different gas mixes from their surroundings.

The exact makeup and temperature of air masses may be a factor in ozone
destruction. Ozone-destroying clouds, or polar stratospheric clouds, are
composed of water and nitric acid. Colder temperatures for a longer period
of time cause “denitrification.” This occurs when Arctic polar
stratospheric clouds precipitate, removing nitrogen from the upper
atmosphere. Denitrification increases the opportunity for chlorine
compounds to destroy ozone more efficiently.

Cooling of the stratosphere will likely increase ozone loss during Arctic
winters in coming decades, even as chlorine and bromine levels decrease as
a result of the Montreal Protocol, according to scientists. The buildup of
greenhouse gases, such as carbon dioxide, tends to trap more heat near
Earth’s surface, while at the same time colder than normal temperatures are
experienced above, in the stratosphere, where ozone breakdown occurs,
researchers said.

The ER-2 science flights took place as part of two international field
experiments: NASA’s SAGE III Ozone Loss and Validation Experiment (SOLVE)
and the European Commission-sponsored Third European Stratospheric
Experiment on Ozone (THESEO). More information about the AGU fall meeting
is on the Internet at http://www.agu.org/meetings/fm00glan.html

DETAILED LISTING OF NASA AMES AGU PRESENTATIONS WITH SHORT SUMMARIES FOLLOWS:

National Aeronautics and Space Administration

Ames Research Center, Moffett Field, California 94035-1000

650-604-9000

FS-ARC-0012_13

American Geophysical Union Meeting, San Francisco, CA

Dec. 15-19, 2000, Moscone Convention Center

NASA Ames presentations:

Note: This listing highlights NASA Ames Earth science presentations at the
AGU; most of these presentations also have co-authors from other
organizations, and we will list those persons separately. In addition,
hundreds of other scientists are also attending and presenting. Please
check the AGU Internet site for a summary of additional presentations, all
participants and their affiliations as well as any schedule changes. The
AGU website URL is: http://www.agu.org/meetings/fm00glan.html

1. Fri., Dec. 15, 2000, 8:30 a.m. PST, location Hall D

Posters, “Dependence of Aerosol Light Absorption and Single Scattering
Albedo on Ambient Relative Humidity for Sulfate Aerosols with Black Carbon
Cores.” Ames participants: P. Hamill, presenter; J. Redemann, principal
author and Phil Russell.

2. Fri., Dec. 15, 2000, 9:35 a.m. PST, location121

“Airborne Aerosol Closure Studies During PRIDE,” NASA Ames participants:
Principal author and presenter Jens Redemann (working for the Bay Area
Environmental Research Institute under a cooperative agreement with NASA
Ames Research Center, Moffett Field, CA) and Phil Russell of Ames. Other
participants: R.C. Levy of NASA Goddard Space Flight Center, Greenbelt, MD.
Other participants: L. Remer, Y. Kaufman, R. Kleidman, B. Holben,

Summary: The Puerto Rico dust experiment (PRIDE) took place in Puerto Rico
from June 26 to July 24, 2000. Scientists studied Saharan dust that wind
carried to the Puerto Rican region. This was the first experiment to
compare the Terra satellite’s aerosol data with data from a variety of
ground, shipboard and air-based instruments. Atmospheric aerosols are made
of tiny, solid or liquid particles suspended in air.

During this presentation scientists compare sunphotometer data to
measurements from aerosol size sensors and light-scattering sensors that
flew on the same aircraft as the sunphotometer. A sunphotometer measures
the amount of sunlight that penetrates smoke and other aerosols in the
atmosphere at different wavelengths, including ultraviolet, visible and
infrared light. The purpose of this closure study is to determine if
different types of aerosol measurements give consistent results.

3. Fri., Dec. 15, 2000, 9:50 a.m. PST, location Moscone Center 121,

“Solar Spectral Radiative Forcing Due to Dust Aerosol during the Puerto
Rico Dust Experiment.” Ames participants: Peter Pilewskie, presenter and
principal author, J.S. Reid and Phil Russell. Other participants: H.H.
Jonnson, R. Bergstrom, M. Rabbette, and J. Livingston.

4. Fri., Dec. 15, 2000, 1:50 p.m. PST, Location 123

“Validation of MODIS Aerosol Retrievals During PRIDE,” NASA Ames
participants: Phil Russell, J. Livingston. (MODIS is the Moderate
Resolution Imaging Spectrometer.) Other participants: Principal Author and
presenter R.C. Levy, Goddard Space Flight Center, Greenbelt, MD; L. Remer;
Y. Kaufman; R. Kleidman; B. Holben; J. Livingston.

Summary: The Puerto Rico dust experiment (PRIDE) took place in Puerto Rico
from June 26 to July 24, 2000. Scientists studied Saharan dust that wind
carried to the Puerto Rican region. This was the first experiment to
compare the Terra satellite’s aerosol data with data from a variety of
ground, shipboard and air-based instruments. Aerosols are made of tiny,
solid or liquid particles suspended in gas. During the study, scientists
tried to validate satellite aerosol data including the size of the
particles and the optical depth. Optical depth is a measure of blocking of
light by a medium such as dust.

The NASA-Ames sunphotometer, flown aboard a research aircraft, helped
scientists to try to validate the satellite data. A sunphotometer measures
the amount of sunlight that penetrates smoke and other aerosols in the
atmosphere at different wavelengths, including ultraviolet, visible and
infrared light.

Once satellite data is calibrated with ground (or “ground truth”) and
airborne observations, scientists can use the satellite data to develop
useful regional and global computer pictures of atmospheric or ground
conditions.

5. Sat., Dec. 16, 2000, 8:30 a.m. PST, Location Hall D

Posters, “Puerto Rico Dust Experiment-PRIDE: Mission Flight Summary and
Aerosol Instrument Calibrations,” NASA Ames participants: P. A. Pilewskie
and J.M. Livingston. Other participants: Principal author and presenter
J.E. Kinney; H.H. Jonnson; J.S. Reid.

Summary: From mid-June to mid-July, 2000, scientists conducted the Puerto
Rico dust experiment (PRIDE). One of the many instruments flown on the
primary aircraft taking data is the NASA Ames’ sunphotometer that measures
how much sunlight penetrates smoke and other aerosols. Other Ames
instruments that scientists flew on the missions are two solar spectral
flux radiometers. This kind of radiometer helps researchers determine how
much solar energy is absorbed by particles of smoke and dust and other
aerosols, and how much energy clouds reflect. Scientists will present a
summary of their in-flight data that covered about 20,000 square kilometers.

Ames scientist John Livingston of SRI International, Menlo Park, CA, will
co-chair the “poster session” about the summer 2000 study of Saharan dust
transported by winds to the Caribbean region. During the study, Ames
researchers used the airborne multiwavelength sunphotometer and airborne
and ground-based solar spectral flux radiometers to characterize the effect
on the Earth-atmosphere radiation budget (balance.) Ames scientists Peter
Pilewskie (NASA) and Jens Redemann (Bay Area Environmental Research
Institute) will discuss results in oral presentations, Friday morning, Dec.
15.

.
In the dust study, as in other Earth science studies, once satellite data
is calibrated with ground (or “ground truth”) and airborne observations,
scientists can use the satellite data to develop useful regional and global
computer pictures of atmospheric or ground conditions.

6. Sat. Dec. 16, 2000, 8:30 a.m. PST, Location Hall D

Posters, “Airborne Sunphotometry of African Dust and Marine Boundary Layer
Aerosol Particles in PRIDE.” NASA Ames participants: Principal author and
presenter J.M. Livingston, J. Redemann, P.B. Russell, B. Schmid, P.
Pilewskie. Other participant: J.S. Reid.

Summary: The NASA Ames six-channel sunphotometer was carried on a research
aircraft, based at Puerto Rico in the summer of 2000. Scientists used the
instrument to make measurements related to airborne Saharan dust in the
Caribbean region during 21 science airplane flights. The sunphotometer
measures how much sunlight penetrates smoke and other aerosols. This data
collection took place during the Puerto Rico dust experiment (PRIDE).

7. Sat. Dec. 16, 2000, 9:30 a.m. PST, Location 122

“Biomass Burning Losses of Carbon Estimated from Ecosystem Modeling and
Satellite Data Analysis for the Brazilian Amazon Region.” NASA Ames
participants: Principal author and presenter Chris Potter, Steve Klooster,
Vanessa Brooks Genovese, Matthew Bobo, A. Torregrosa

Summary: The study’s results indicate carbon emission estimates from annual
burning in the eight states of the Brazilian Legal Amazon in the early
1990’s are three to five times higher than reported in similar recent
studies that implied the region tends towards a net-zero annual source of
emissions from terrestrial carbon. Some sources of terrestrial carbon
include burning and deforestation. The scientific journal, “Atmospheric
Environment,” will also print full results of the new NASA Amazon
research. This study is part of the NASA-supported “Large Scale
Biosphere-Atmosphere
Experiment in Amazonia,” an international research project led by Brazil.

8. Sat., Dec. 16, 2000, 9:40 a.m. PST, location MC 131

“Mixing events during SOLVE/THESEO revealed by tracer correlations,” NASA
Ames participants: Principal author and presenter H. Jost, J.B. Greenblatt,
M Loewenstein, J.R.Podolske, P. Bui. Other participants: A. Andrews,
B.Daube, C.Gerbig, S. Wofsy, E. Richard, K. Aikin.

Summary: The NASA ER-2 high altitude aircraft carried instruments that
measured nitrous oxide (N2O), carbon dioxide (CO2), ozone (O3) and
temperatures in regions of the Arctic stratosphere during the winter of
1999 -2000 to determine how these gases mix. The Arctic stratosphere is
located from about 6 miles to 30 miles above Earth. Researchers found that
various air masses have different gas mixes from their surroundings.

The exact makeup and temperature of air masses may be a factor in ozone
destruction. Ozone destroying clouds, or polar stratospheric clouds, are
made of water and nitric acid. Colder temperatures for a longer period of
time cause “denitrification.” This occurs when Arctic polar stratospheric
clouds precipitate, removing nitrogen from the upper atmosphere.
Denitrification increases the opportunity for chlorine compounds to destroy
ozone more efficiently. (For more details, see presentation, “How do Polar
Stratospheric Clouds Form?” on Dec. 16, 2000, at 4:35 p.m., at the Moscone
Center, Rm. 131.)

Cooling of the stratosphere will likely increase ozone loss during Arctic
winters in coming decades, even as chlorine and bromine levels decrease as
a result of the Montreal Protocol, according to scientists. The buildup of
greenhouse gases, such as carbon dioxide, tends to trap more heat near
Earth’s surface, while at the same time colder than normal temperatures are
experienced above, in the stratosphere, where ozone breakdown occurs,
according to scientists.

The Earth’s ozone layer protects life below from harmful ultraviolet
radiation coming from the Sun that can lead to the formation of skin
cancers. Scientists have observed unusually low levels of ozone over the
Arctic during recent winters.

The ER-2 science flights took place as part of international field
experiments: NASA’s SAGE III Ozone Loss and Validation Experiment (SOLVE)
and the European Commission-sponsored Third European Stratospheric
Experiment on Ozone (THESEO).

9. Sat., Dec. 16, 2000, 11:30 a.m. PST, location 124

“Predicting Climate Change Effects on Vegetation, Soil Thermal Dynamics,
and Carbon Cycling in Ecosystems of Interior Alaska.” NASA Ames
participants: Principal author Chris Potter, and presenter V. Brooks
Genovese.

Summary: Simulations of selected sites in Alaska’s Denali National Park
suggest that the past 50-year climate trends of warming temperatures may
shift the local ecosystem from dominance by coniferous evergreen trees to a
mixture of evergreens and deciduous, broad-leafed trees. Deciduous trees
have leaves that all fall off seasonally or at certain times during their
lives. The investigators’ model predicts that a difference of only 3
degrees centigrade in mean annual air temperatures (which is probable,
according to global warming predictions for the next several decades made
by climate models) could force a switch from the long-term presence of
tundra vegetation
to the presence of coniferous (mainly spruce) forest. Tundra is a Arctic or
subarctic ecosystem comprised of small shrubs and herbs.

10. Sat., Dec. 16, 2000, 2:25 p.m. PST, location 131 (A62C-04)

“In situ Observations of Irreversible Denitrification in the 1999- 2000
Arctic winter Stratosphere,” NASA Ames participants: Hansjurg Jost, M.
Lowenstein, B.J. Greenblatt, J.R. Podolske. Other participants: Lead
author and Presenter Peter Popp NOAA, Boulder, CO; R.S. Gao, J.C. Holecek;
M.J. Northway; D.W. Fahey; D.F. Hurst; P.A. Romashkin; J.W. Elkins; C.R.
Webster; G.J. Flesch; D.C. Scott; R.J. Salawitch; G.C. Toon; R.L. Herman;
A.E. Andrews; B.C. Daube; C.Gerbig; P.A. Newman; L.R. Lait; B. Sen.

Summary: The exact makeup and temperature of air masses may be a factor in
ozone destruction. Polar stratospheric clouds are made of water and nitric
acid. Colder temperatures for a longer period of time cause
“denitrification.” This occurs when Arctic polar stratospheric clouds
precipitate, removing nitrogen from the upper atmosphere. Denitrification
increases the opportunity for chlorine compounds to destroy ozone more
efficiently.

11. Sat., Dec. 16, 2000, 3:50 p.m. PST, location 131

“Three Dimensional Simulations of Arctic Polar Stratospheric Cloud
Formation,” NASA Ames participants: Principal author and presenter E. J.
Jensen, A. Tabazadeh, Katja Drdla. Other participants: O.B. Toon and S.R.
Kawa.

Summary: Scientists developed a computer model that can simulate polar
stratospheric clouds (PSCs) in 3-D. Polar stratospheric clouds are made of
water and nitric acid. These clouds generally form about 13 miles above
Earth’s poles where temperatures can drop to minus 110 degrees Fahrenheit
and below.

Colder temperatures for a longer period of time cause “denitrification” in
PSCs. This occurs when Arctic polar stratospheric clouds precipitate,
removing nitrogen from the upper atmosphere, and increasing the chance for
chlorine compounds to destroy ozone more efficiently.

The 3-D computer simulation of polar stratospheric clouds for November 1999
through January 2000, includes simulation of sulfate aerosols and nitric
acid trihydrate particles. Scientists compared these cloud simulations
with satellite and NASA DC-8 aircraft measurements of PSCs taken in the
Arctic during the same period as part of the NASA’s SAGE III Ozone Loss and
Validation Experiment (SOLVE).

12. Sat., Dec. 16, 2000, 4:35 p.m., location 131

“How do Polar Stratospheric Clouds Form?” NASA Ames participant: Principal
author and presenter Katja Drdla. Other participants: B. Gandrud, D.
Baumgardner and R. Herman.

Summary: Scientists observed formation of polar stratospheric clouds
(PSCs) during the international Arctic SAGE III Ozone Loss and Validation
Experiment (SOLVE) experiment in which NASA participated. This field
experiment took place from November 1999 through March 2000. Evidence
indicates that a majority the PSC cloud particles remain liquid throughout
the winter. However, a small fraction of the particles freeze. Current
theories cannot explain the frozen particles. Scientists will discuss the
effects of these frozen cloud particles, including “denitrification.”
Denitrification occurs when Arctic polar stratospheric clouds stay cold for
a week or so and then precipitate, removing nitrogen from the upper
atmosphere. Nitrogen loss from the upper atmosphere increases the
opportunity for chlorine compounds to destroy ozone more efficiently.

The polar stratospheric clouds involved in the reactions contain nitric
acid and water, according to researchers who discovered these clouds in
1986.

13. Sun., Dec. 17, 2000, 8:30 a.m. PST, location Hall D

Posters, “Use of High-speed N2O Measurements From SOLVE to Refine the Nash
Definition of the Vortex Edge.” NASA Ames participants: Principal author
and presenter J.B. Greenblatt, Hansjurg Jost, M. Loewenstein, J.R.
Podolske, Katja Drdla. (Note: N2O is nitrous oxide.) Other participants:
P.A. Newman, L.R. Lait, R.J. Salawitch.

Summary: This presentation offers a way to better define the stratospheric
vortex boundary by taking nitrous oxide (N2O) measurements from aircraft.
Researchers compared the nitrous oxide data with traditional methods and
data. The airborne nitrous oxide readings were quicker and more accurate
than traditional methods. The Arctic polar vortex, which occurs only during
polar winters, is a rapid circulation of a mass of air around either of
Earth’s poles. The Arctic vortex temporally isolates the polar from the
mid-latitude air.

Scientists used the NASA ER-2 airplane to fly across the vortex boundary,
and an instrument on the aircraft measured nitrous oxide (N2O)
concentrations.
Researchers discovered that the nitrous oxide measurements could help to
fine-tune the location of the stratospheric vortex boundary.

Better defining the edge of the vortex is important because there are quite
complicated methods that analyze wind data to

These raw wind data must be analyzed to avoid errors. Instead of using
complex data scientists can get the information immediately for nitrous
oxide reading from aircraft instruments.

14. Sun., Dec. 17, 2000, 8:30 a.m. PST, location Hall D

Posters, “Observations of Hydration and Dehydration in the winter 2000
Arctic Stratosphere,” NASA Ames participants: Katja Drdla, T.P. Bui.
Other participants: Principal author and presenter R.L. Herman, NASA Jet
Propulsion Laboratory, Pasadena, CA; B.W. Gandrud; C.R. Webster; M.R.
Schoeberl.

Summary: The NASA ER-2 aircraft intercepted air parcels with unusual water
mixing ratios in the Arctic polar vortex January – February 2000 during the
SAGE III Ozone Loss Validation Experiment (SOLVE). A water-mixing ratio is
the humidity, or water concentration in an air parcel.

The Arctic polar vortex, which occurs only during polar winters, is a rapid
circulation of a mass of air around either of Earth’s poles. The Arctic
vortex temporally isolates the polar from the mid-latitude air. Scientists
found unusually low water concentrations in the Arctic stratosphere, which
is located from about 6 miles to 30 miles above Earth.

Researchers wondered what happened to the missing water vapor, which they
expected, should be in the Arctic air parcels. For the first time,
scientists discovered that in other upper atmospheric air parcels there
were increases in water vapor. This finding confirms that polar
stratospheric clouds (PSCs) play a key role in the distribution of water
vapor in the stratosphere. At sufficiently low temperatures, the water
vapor formed polar stratospheric clouds (PSCs), scientists report. PSCs
are made of water and nitric acid.

These clouds take part in a chain reaction that results in ozone loss.
This research implies that if the Arctic becomes colder at the
stratospheric altitudes, then more PSCs can form, resulting in more ozone
loss.

15. Sun., Dec. 17, 2000, 8:30 a.m. PST, location Hall D

Posters, “Processes Controlling Water Vapor in the Winter Arctic
Stratospheric Middleworld.” NASA Ames participants: Principal author and
presenter Dr. Leonhard Pfister, H. Selkirk, Eric Jensen, Dr. James R,
Podolske. Other participants: G. Sachse; M. Avery; M.R. Schoeberl

Summary: The troposphere extends from Earth’s surface to an altitude of
about 5 to 10 miles and is below the stratosphere. The Arctic stratosphere
is located from about 10 miles to 30 miles above Earth’s surface. The
Arctic stratospheric middleworld is that part of the stratosphere that can
mix with the troposphere below without undergoing significant heating or
cooling.

Water vapor in the winter Arctic stratospheric middleworld is important for
two reasons. The Arctic middleworld is a source of air for the upper
troposphere, and its water vapor content helps to determine the upper
tropospheric water distribution.

Water vapor in Earth’s atmosphere, like carbon dioxide and other greenhouse
gases, can serve as a blanket, keeping heat from radiating into space, and
causing higher average temperatures on Earth and in its atmosphere. In the
upper troposphere, a small amount of water goes a long way in acting like a
blanket, trapping infrared (IR) heat. Scientists are trying to figure out
how much of a facto upper tropospheric water vapor is in the total
radiation balance of Earth, and this study is a small part of that effort
to understand water’s role in the balance of heat on a global basis.

Water vapor in the winter Arctic stratosphere also is important because
relative humidity can be large, leading to the formation of cirrus clouds
in the stratospheric middleworld. Some of these clouds could convert
inactive chlorine to its active form, resulting in ozone loss in the
middleworld. This theory is currently quite controversial.

16. Sun., Dec. 17, 2000, 1:30 p.m. PST, location Hall D

Posters, “Discriminating Type 1a and 1b PSCs in Satellite Data” NASA Ames
participants: Principal author and presenter A.W. Strawa, Katja Drdla, R.
Pueschel, P. Hamill. Other participants: M. Fromm, K.W. Hoppel, E.V.
Browell, C.A. Hostetler.

Summary: Scientists show how they can use satellite observations of Arctic
clouds to measure the extent of two kinds of polar stratospheric clouds
(PSCs), Both kinds of clouds are implicated in ozone loss. During the
recent SAGE III Ozone Loss and Validation Experiment (SOLVE) in the Arctic,
scientists found that only type 1a clouds contain very large particles of
nitric acid. These relatively big particles fall out of the stratosphere,
causing denitrification. The Arctic stratosphere is located from about 6
miles to 30 miles above Earth. Because nitric acid normally reduces ozone
loss, denitrification leads to ozone loss. Type 1b clouds are smaller, and
do not cause much sedimentation of nitric acid, and so are less of a factor
in ozone loss. Scientists would like to know the extent of type 1a and
type 1b clouds, and satellite observations able to measure these clouds
would be helpful.

17. Sun., Dec. 17, 2000,1:30 p.m. PST, location Hall D

Posters, “In-situ observations of PSCs generated by gravity waves.” NASA
Ames participants: Principal author and presenter J. Dean-Day, L. Pfister,
T. Bui. Other participants: M.J. Mahoney, B..W. Gandrud.

Polar stratospheric clouds (PSCs) are potential sites for chemical
reactions that can locally deplete ozone in the Arctic stratosphere. This
atmospheric layer is located from about 6 miles to 30 miles above Earth.
Gravity waves that spread up from the troposphere can provide the “forcing”
necessary to cause PSC formation, and increase vertical motions and PSC
cooling rates. The troposphere extends from the Earth’s surface to an
altitude of about 7 to 10 miles and is below the stratosphere.

18. Sun., Dec. 17, 2000, 1:30 p.m. PST, location Hall D

Posters, “On the Existence and Persistence of a Polar Freezing Belt and Its
Role in Stratospheric Denitrification.” Ames participants: Principal
author and presenter A. Tabazadeh, E.J. Jensen, Katja Drdla. Other
participants: O.B. Toon, M.R. Schoeberl.

Summary: Scientists used computer models of the Arctic and Antarctic
clouds during various winters. These computer simulations show that large
crystalline particles of nitric acid often solidified over both the north
and south poles throughout the winter, forming a persistent polar freezing
belt in both hemispheres.

Denitrification occurs when large nitric acid-containing crystalline
particles (which are actually about the same size as a piece of dust, but
are large for this part of the atmosphere) fall out of the stratosphere. A
denitrified stratosphere in early spring is primed for ozone destruction
because reactive nitrogen, a factor in ozone loss, has been removed from
the atmosphere through the denitrification process.

Scientists say that the Arctic winter of 1999 – 2000 in early January was
very much like an Antarctic winter in late June. Calculated denitrification
in many areas showed 20 to 50 percent denitrification during the 1999-2000
winter. Calculated denitrification for cold Arctic winters in the 1990s
were only about 10 to 20 percent. The growth in the magnitude of
denitrification during the last Arctic winter is attributed to greenhouse
gas build-up in the Earth’s atmosphere. Greenhouse gases cause warming at
the Earth’s surface and cooling in the stratosphere where the ozone
layer is located.

19. Sun., Dec. 17, 2000, 1:30 p.m. PST, location Hall D

Posters, “Three Years of Project ALERT: A California Partnership for
Pre-Service Teacher Earth-Science Education.” Ames participant: J.W.
Skiles. SETI Institute.

Summary: Project ALERT (Augmented Learning Environment and Renewable
Teaching) has completed the third year of a college faculty involvement
with government research laboratories. ALERT partners are the California
State University (CSU) geoscience and education department at ten
different campuses and NASA Ames Research Center, Moffett Field, CA, and
NASA Jet Propulsion Laboratory, Pasadena, CA. One ALERT goal is to infuse
earth science course materials into the core science curriculum of
pre-service teachers.

20. Mon., Dec. 18, 2000, 1:30 p.m. PST, location Hall D

Posters, “Development of Statewide Inventory Estimates of Ammonia Emissions
from Natural Soils and Crop Fertilizers in California.” Ames participants:
Principal author and presenter Steve Klooster, Chris Potter and V. Brooks
Genovese. Other participants: C. Krauter, M. Benjamin.

Summary: Ammonia is the dominant gaseous base in the atmosphere and is a
primary neutralizer of acids in the air. Ammonia in the air can react to
form ammonium nitrate or ammonium sulfate that can generate airborne
particles.
Ammonia emissions from nitrogen-based fertilizer and agricultural sources
are undetermined for California and other large agricultural regions. The
scientists’ objectives is to developing the first statewide ammonia
emissions estimates based on field measurements, satellite observation and
computer modeling. This study reports on the first systematic measurements
of ammonia from fertilized crop fields in the San Joaquin Valley. These
new ammonia emissions data will be included in the first computer models of
statewide emission from soils and fertilizers, which could significantly
improve assessments of atmospheric chemistry for the Valley regions.

21. Tues., Dec. 19, 2000, 8:30 a.m. PST, location Hall D

Posters, “Interannual Variations in Net Terrestrial Carbon Sinks Driven by
Modified MODIS Algorithm Products for Global Land Surface Variable.” Ames
participants: Principal author and presenter Chris Potter, A. Torregrosa,
Steve Klooster, V. Brooks Genovese. Additional participant: R. Myneni.

Summary: To assess global carbon changes in the ecosystem of the world,
scientists used computer simulations to look at production of gaseous
carbon compounds and soil respiration for 1982 -1994. Satellite data that
researchers used in the computer model includes estimates of carbon
absorbed by plants.

The simulation predicted that over the northern latitudes, above 45
degrees, north, there were steady increases in carbon compounds being
absorbed by plants and trees which act as a “sinks,” or reservoirs for
carbon “storage.” Forest and tundra areas may serve as temporary “sinks”
for carbon in response to warmer than average spring temperatures. When
trees and vegetation die and are absorbed into soil, bacteria digest plant
material and return carbon to the air as CO2 emissions.

The scientists’ computer model predicted a 1.5 to 2 percent annual increase
in gaseous carbon compounds being captured by plants and trees from 1985 to
a peak in1990 in the northern latitudes. The 1991 Mt. Pinatubo volcanic
eruption resulted in a seven-percent decrease in atmospheric CO2 being
trapped by plants and trees in the northern latitude zones, according to
the computer simulation. The researchers’ computer model also predicted
that the rate of carbon capture by plants and trees returned to
pre-eruption levels in 1993 and 1994.

Scientists are developing computer models, such as the one discussed in
this study, to accurately portray trends Earth’s carbon cycle over large
areas of the globe because direct field measurements on a large scale are
not possible.

12/00 — For further information, contact:

NASA Ames Research Center

Office of Communication, MS 204-2

Moffett Field, CA 94035-1000