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The Second Airborne Arctic Stratospheric Expedition (AASE-II) on CD-ROM

Entry ID: AASE9192

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Summary

Abstract: This CD-ROM contains the final data pertaining to the Airborne Arctic Stratospheric Expedition II (AASE-II) which was based in Bangor, Maine between October 1991 and March 1992, with ER-2 flights from Ames Research Center, Moffett Field (California), Fairbanks (Alaska), and Bangor (Maine), along with and DC-8 flights from Ames, Bangor, Anchorage (Alaska), Stavanger (Norway), and Tahiti. The data ... consist of measurements collected onboard the NASA ER-2 and DC-8 aircraft, ozonesonde soundings from six Canadian stations, global grid point values of Nimbus 7 TOMS ozone, and selected radiosonde soundings from stations in the region of the experiment. Theory teams provided calculations of potential vorticity, temperature, geopotential, horizontal winds, parcel back trajectories, and concentrations of short lived species along the aircraft flight tracks; and northern hemispheric analyses of potential vorticity, temperature, geopotential, horizontal winds, and radiative heating rates.

All files within this release are standard ASCII files with variable length records terminated by a carriage return/line feed pair (, ASCII decimal values 13 and 10). Therefore, MS-DOS users should be able to read them as they are, but UNIX and MAC users will have to strip off either the or the from each line to convert them to standard UNIX or MAC files. Commercially available software, such as dos2unix and Apple File Exchange, exists to convert MS-DOS files to both UNIX and MAC files. VMS users can define the files to have STREAM record formats.

In general, the file naming convention uses a two-character prefix to identify the measurement, followed by a six digit number (yymmdd) giving the year, month, and day (UT) of the flight, balloon launch, or model result. To identify the measurement platform, a three character extension of EA1, DA1, Bhh, or Ghh is used to denote the data is from the ER-2, DC-8, balloon, or grid point model output (hh denotes the UT hour of balloon launch or model result). Exceptions to this convention are the SFyymmdd.Enn files which use the extensions E00, E01, E05, E30 to denote aerosol loading factors; the TOMS data files which have the extensions N7; and the chemical modelling result MA911006.H00.

The NASA ER-2 and DC-8 aircraft and balloons were employed to carry a suite of instruments into the lower stratosphere. Many of these were used in the 1989 AASE-I. New instruments included a gas chromatograph to measure CFC-11, a diode laser spectrometer to measure CH4, N2O, and HCL, and spectrometers to measure in situ CO, CH4, N2O, and CO2. The ER-2 was deployed from Ames Research Center, California (37N, 122W), to Fairbanks, Alaska (65N, 147W) in October 1991, so that air could be observed at the highest possible latitudes before it was incorporated into the forming polar vortex. In November 1991, the ER-2 was moved to Bangor, Maine (45N, 69W) where it would have a high probability of encountering air in the arctic vortex, but could still have acceptable weather for aircraft operations. The ER-2 missions involved flights to Greenland, 20N, 25N, 55N, 65N, 70N, 85N, and 90N. The DC-8 missions involved flights to Tahiti, Norway, Wyoming, 15N, 20N, 65N, and 90N.

On March 11, 1992, a balloon launched from Greenland (67.0N, 50.6W) carried instruments to measure O3, NO, and CLO. The objective of the balloon launch was to extend the aircraft measurements to higher latitudes. The Canadian Ozone Experiment (CANOZE-7) launched balloons from December 1991 to March 1992 from Alert, Canada (82N, 62W). The nitric acid measurements made from these balloons are also reported here.

The AASE-II data set provides the first seasonal perspective on polar ozone chemistry in the northern hemisphere. It also provides the first detailed investigations of the chemistry occurring on volcanic sulfuric acid aerosols. The data show clearly the important counterbalance between dynamical resupply of ozone in the arctic vortex and ongoing chemical destruction. The aircraft measurements also show the important role of nitrogen oxides, produced by nitric acid photolysis, in destroying CLO after temperatures become too high for polar stratospheric clouds to form. These results highlight the fact that large ozone losses in the arctic spring require either extensive denitrification of the vortex, which could occur if temperatures fell below that at which ice clouds form, or long lasting polar stratospheric clouds, that will occur if temperatures remain low enough for nitric acid to condense for extended periods of time. Neither extremely low temperatures, with extensive denitrification, nor a prolonged period of low temperatures occurred in 1992. Therefore, although very high levels of CLO were present in the arctic vortex in January 1992, the ozone loss that occurred was limited by the rapid decline of CLO in February. Other winters, such as 1992-1993, which had much more persistent low temperatures, may have conditions more conducive to significant ozone loss. It is also clear from the AASE-II data set that volcanic aerosols do significantly perturb stratospheric chemistry. However, some of the reactions are saturated at aerosol surface areas only slightly greater that ambient, and others depend strongly on temperature. Therefore, an assessment of the impact of the Pinatubo eruption on global ozone requires careful treatment of the entire thermal, dynamical, aerosol and chemical evolution of the stratosphere.

Related URL

Link: GET DATA

Link: VIEW PROJECT HOME PAGE

Description: Airborne Arctic Stratospheric Expedition II (AASE II) Home Page

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: 90.0

S: -17.0

E: 20.0

W: -180.0

Data Set Citation

Dataset Originator/Creator: Airborne Arctic Stratospheric Expedition II Team (AASE-II)

Dataset Title: The Second Airborne Arctic Stratospheric Expedition (AASE-II) on CD-ROM

Online Resource: http://cloud1.arc.nasa.gov

Temporal Coverage

Start Date: 1991-10-04

Stop Date: 1992-03-26

Location Keywords

OCEAN > ARCTIC OCEAN

CONTINENT > NORTH AMERICA > CANADA

Science Keywords

ATMOSPHERE > AEROSOLS > AEROSOL EXTINCTION

ATMOSPHERE > AEROSOLS > AEROSOL PARTICLE PROPERTIES

ISO Topic Category

GEOSCIENTIFIC INFORMATION

IMAGERY/BASE MAPS/EARTH COVER

Platform

TERRA > Earth Observing System, TERRA (AM-1)

Instrument

MODIS > Moderate-Resolution Imaging Spectroradiometer

Project

EOS > Earth Observing System

EOSDIS > Earth Observing System Data Information System

ESIP > Earth Science Information Partners Program

CWIC > CEOS WGISS Integrated Catalog

Quality Quality indicators for MODIS snow data can be found in three places:
* AutomaticQualityFlag and the ScienceQualityFlag metadata objects and their corresponding explanations: AutomaticQualityFlagExplanation and ScienceQualityFlagExplanation located in the ... CoreMetadata.0 global attributes
* Custom local attributes associated with each Scientific Data Set (SDS), for example snow cover
* Snow Cover Pixel QA data field.
These quality indicators are generated during production or in post-production scientific and quality checks of the data product. The AutomaticQualityFlag is automatically set according to conditions for meeting data criteria in the snow mapping algorithm. In most cases, the flag is set to either Passed or Suspect, and in rare instances, it may be set to Failed. Suspect means that a significant percentage of the data were anomalous and that further analysis should be done to determine the source of anomalies. The AutomaticQualityFlagExplanation contains a brief message explaining the reason for the setting of the AutomaticQualityFlag. The ScienceQualityFlag and the ScienceQualityFlagExplanation maybe updated after production, either after an automated QA program is run or after the data product is inspected by a qualified snow scientist. Content and explanation of this flag are dynamic so it should always be examined if present in the external metadata file. The snow algorithm identifies missing data and reports them in the output product. Certain expected anomalous conditions may exist with the input data such as a few missing lines or unusable data from the MODIS sensor. In these cases, the snow algorithm makes no snow decision for an affected pixel. Summary statistics are calculated for these conditions and reported as Valid EV Obs Band x percent and Saturated EV Obs Band 1 percent local attributes Riggs, Hall, and Salomonson 2006). In addition to these data values, the product contains quality information at the pixel level. The Snow Cover Pixel QA data field provides additional information on algorithm results for each pixel within a MODIS scene and is used as a measure of usefulness for snow-cover data. The QA data are stored as coded integer values and tell if algorithm results were nominal, abnormal, or if other defined conditions were encountered for a pixel (Riggs, Hall, and Salomonson 2006). For example, intermediate checks for theoretical bounding of reflectance data and the NDSI ratio are made in the algorithm. In theory, reflectance values should lie within the 0-100 percent range, and the NDSI ratio should lie within the -1.0 to +1.0 range. Summary statistics are kept for pixels that exceed these theoretical limits; however, the test for snow is done regardless of violations of these limits. The NASA Goddard Space Flight Center: MODIS Land Quality Assessment Web site provides updated quality information for each product.

Ancillary Keywords

Antarctic

Arctic

Data Set Progress

IN WORK

Data Center

NSIDC Distributed Active Archive Center

Data Center URL: http://nsidc.org/daac/index.html

Data Center Personnel
Name: NSIDC USER SERVICES Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 Email: nsidc at nsidc.org Contact Address: National Snow and Ice Data Center CIRES, 449 UCB University of Colorado City: Boulder Province or State: CO Postal Code: 80309-0449 Country: USA

National Snow and Ice Data Center

Data Center URL: http://nsidc.org

Data Center Personnel
Name: NSIDC USER SERVICES Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 Email: nsidc at nsidc.org Contact Address: National Snow and Ice Data Center CIRES, 449 UCB University of Colorado City: Boulder Province or State: CO Postal Code: 80309-0449 Country: USA

Distribution

Distribution Media: FTP

Distribution Size: 0.5 - 10.0 MB

Distribution Format: GeoTIFF

Fees: None

Distribution Media: FTP

Distribution Size: 0.5 - 10.0 MB

Distribution Format: HDF-EOS

Fees: None

Personnel

DOROTHY K. HALL

Role: INVESTIGATOR

Contact Address:

National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC)

Mail stop 614.1

City: Greenbelt

Province or State: MD

Postal Code: 20771

Publications/References

Diner, D.J., J.V. Martonchik, C. Borel, S.A.W. Gerstl, H.R. Gordon, Y. Knyazikhin, R. Myneni, B. Pinty, and M.M. Verstraete. 1999. MISR Level-2 surface retrieval algorithm theoretical basis document. Pasadena, CA: Jet Propulsion Laboratory.

Earth Science Data and Information System (ESDIS). 1996. EOS Ground System (EGS) systems and operations concept. Greenbelt, MD: Goddard Space Flight ...

Extended Metadata Properties

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Creation and Review Dates

DIF Creation Date: 2006-11-09

Last DIF Revision Date: 2012-05-04

Future DIF Review Date: 2008-09-01

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