BOREAS RSS-12 Airborne Tracking Sunphotometer Measurements
Summary
The BOREAS RSS-12 team collected both ground and airborne sunphotometer
measurements for use in characterizing the aerosol optical properties of the
atmosphere during the BOREAS data collection activities. These measurements are
to be used to: 1) measure the magnitude and variability of the aerosol optical
depth in both time and space; 2) determine the optical properties of the boreal
aerosols; and 3) atmospherically correct remotely sensed data acquired during
BOREAS. This data set contains airborne tracking sunphotometer data that were
acquired from the C-130 aircraft during its flights over the BOREAS study areas.
The data cover selected days and times from May to September 1994. The data are
stored in tabular ASCII files.
Table of Contents
* 1 Data Set Overview
* 2 Investigator(s)
* 3 Theory of Measurements
* 4 Equipment
* 5 Data Acquisition Methods
* 6 Observations
* 7 Data Description
* 8 Data Organization
* 9 Data Manipulations
* 10 Errors
* 11 Notes
* 12 Application of the Data Set
* 13 Future Modifications and Plans
* 14 Software
* 15 Data Access
* 16 Output Products and Availability
* 17 References
* 18 Glossary of Terms
* 19 List of Acronyms
* 20 Document Information
1. Data Set Overview
1.1 Data Set Identification
BOREAS RSS-12 Airborne Tracking Sunphotometer Measurements
1.2 Data Set Introduction
The Airborne Tracking Sunphotometer (ATSP) data set consists of instrument
voltages; Sun position information; ozone (O3), nitrogen dioxide (NO2) and
aerosol optical depth values. These data were collected and processed by the
BOReal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science Team 12 (RSS-
12) at the National Aeronautics and Space Administration (NASA) Ames Research
Center (ARC). The data provide a good characterization of atmospheric aerosols
during the C-130 flights.
1.3 Objective/Purpose
The overall goal of this investigation was to measure aerosol optical properties
from both ground- and aircraft-based sunphotometers during the 1994 BOREAS
Intensive Field Campaigns (IFCs). These measurements are to be used to:
1) Measure the magnitude and variability of the aerosol optical
depth in both time and space.
2) Determine the optical properties of the boreal aerosols.
3) Atmospherically correct selected remotely sensed data acquired
during BOREAS.
1.4 Summary of Parameters
The phenomenon being measured is the atmospheric aerosol optical depth. The
parameters include Rayleigh optical depth, aerosol optical depth, time,
latitude, longitude, air mass, solar position, and aircraft altitude.
1.5 Discussion
The ATSP data were used in conjunction with the Automated Ground Sunphotometer
(AGSP) data to determine the magnitude and variability of the aerosol optical
depth in both time and space. The aerosol optical depth data will be inverted
using an algorithm developed by King et al., 1978, to derive the size
distribution of the boreal aerosols. Mie theory will then be used to calculate
the aerosol phase function and single-scattering albedo. Finally, the
atmospheric correction algorithm of Wrigley et al., 1992 will be used to
atmospherically correct selected NS001 Thematic Mapper Simulation (TMS), Landsat
Thematic Mapper (TM), and MODerate-resolution Imaging Spectrometer (MODIS)
Airborne Simulator (MAS) data collected during the 1994 BOREAS IFC's.
Atmospheric correction of Landsat TM and other satellite data will use the
aerosol properties derived from surface optical depth measurements. Atmospheric
correction of NS001 and MAS data will use aerosol properties derived from the
airborne optical depth measurements as well as those from the surface
measurements.
1.6 Related Data Sets
BOREAS RSS-12 Automatic Ground Sunphotometer Measurements in the SSA
BOREAS RSS-11 Ground Network of Sunphotometer Measurements
BOREAS RSS-18 Ground Sunphotometer Measurements in the SSA
2. Investigator(s)
2.1 Investigator(s) Name and Title
Robert C. Wrigley (retired 1995)
Principal Investigator
Co-Investigators:
Michael A. Spanner
Robert E. Slye
Philip B. Russell
John M. Livingston
2.2 Title of Investigation
Aerosol Determinations and Atmospheric Correction for BOREAS Imagery
2.3 Contact Information
Contact 1
--------------------------------
Michael A. Spanner
Co-Investigator
Johnson Controls World Services
NASA Ames Research Center
Moffett Field, CA
(415)604-3620
mspanner@gaia.arc.nasa.gov
Contact 2
-------------------------------
Jaime Nickeson
NASA/GSFC
Greenbelt, MD
(301) 286-3373
(301)286-0239(fax)
Jaime.Nickeson@gsfc.nasa.gov
3. Theory of Measurements
The ATSP measures direct-beam solar radiation for six channels in the visible
and near-infrared wavelengths. The solar radiation data are collected in the
form of voltages. The instrument was calibrated before and after the experiment
at high mountain observatories, which often have clean, stable air masses, so
the Langley plot technique could be used. For calibration, data are collected at
a range of solar angles from low solar elevation (air mass=5) to high solar
elevation (air mass =1.8). A regression is developed between log voltage and air
mass. This regression equation is then extrapolated to an air mass of 0. This
value called the zero air mass intercept voltage, is the value used to calibrate
the instrument in a given channel. Great care must be taken to ensure the
stability of these intercept voltages over time. A calibration history is
maintained that attests to the stability of the instrument. The voltages
measured by the instrument during the BOREAS IFCs were converted to total
optical depth using the zero air mass intercept voltages calculated from the
calibrations using the equation:
V/Vo = (Rm/R)^2 exp(-mt)
where V is the measured voltage, Vo is the zero air mass voltage intercept, R is
the radius of Earth's orbit at the time, Rm is the mean radius, m is the air
mass at the time, and t is the total optical depth (usually written as the
Greek letter tau). The aerosol optical depth is calculated from the total
optical depth by subtracting a number of components that contribute to the total
optical depth: Rayleigh scattering and gaseous absorption due to ozone and NO2.
The Rayleigh optical depth is calculated using pressure measured on the
aircraft. NO2and ozone optical depths are subtracted from the total minus
Rayleigh optical depth to obtain the aerosol optical depth. NO2 abundance is
obtained from climatology tables based on Noxon, 1979, and convolved with
absorption coefficients at ATSP wavelengths. Ozone optical depth is calculated
using ozone abundances from the Total Ozone Mapping Spectrometer (TOMS)
satellite instrument and convolved with absorption coefficients at ATSP
wavelengths. The result of this processing is the aerosol optical depth measured
in five channels (not including the 940 nm water vapor channel) at approximately
2-second intervals in the air and 10 second intervals on the ground.
The correction of remote sensing data acquired from satellites or aircraft for
effects due to the intervening atmosphere has proven to be a difficult problem.
Not only does the atmosphere reduce the transmission of the incoming, reflected,
and emitted radiation, but it contributes reflected and emitted radiation of its
own. Under high aerosol concentration conditions, atmospheric radiation
comprises over 90% of the satellite-observed radiance, but even much smaller
effects would degrade the quantitative use of these data unless they are taken
into account. The interaction of radiation with the atmosphere is complex and
has proved difficult to calculate without reference to measurements made at, or
close to, the time and location of interest. Effects due to Rayleigh scattering
from atmospheric gases are well understood because the major gases (nitrogen,
oxygen) that comprise 99% of the atmosphere are well mixed and their
concentrations with altitude are known. The effects because of small particle
(aerosol) scattering are quite variable because of the wide range of aerosol
concentrations; and the variety of aerosols found in the atmosphere. Because
aerosol concentrations cannot be known a priori, they must be measured at the
time and location of remote sensing data acquisition.
The physical properties of aerosols such as size, shape, refractive index, and
concentration in the atmosphere control the aerosol interaction with light
according to a set of optical properties. Three fundamental properties are (1)
the aerosol optical depth, an indirect measure of the size and number of
particles present in a given column of air; (2) the single scattering albedo;
the fraction of light intercepted and scattered by a single particle; and (3)
the phase function; a measure of the light scattered by a particle as a function
of angle with respect to the original direction of propagation.
4. Equipment
4.1 Sensor/Instrument Description
The instrument consists of a solar-tracking system, detector module, temperature
control system, nitrogen-purge system, mechanical drive chain, and data
collection system.
4.1.1 Collection Environment
The ATSP was used for data collection while mounted on the NASA C-130 aircraft.
Data were collected while the aircraft was on the ground and during flight at
altitudes up to 10,120 meters.
4.1.2 Source/Platform
The ATSP was mounted on the NASA ARC C-130 Earth Resources aircraft.
4.1.3 Source/Platform Mission Objectives
The ATSP was developed to obtain accurate multispectral atmospheric extinction
measurements at different altitudes.
4.1.4 Key Variables
The primary quantity being measured is the total optical depth. The aerosol
optical depth is derived by subtracting optical depths caused by other
components of the atmosphere: Rayleigh scattering, ozone absorption, and NO2
absorption.
4.1.5 Principles of Operation
The sensors used are Clairex photoresistors that have been matched to track each
other over the operational range of Sun intensities. The sensing technique uses
a shadow mask that bisects each detector when the system is in balance. The
design allows for very accurate tracking, yet at the same time provides a Field-
of-View (FOV) and accurate tracking in a very compact package. The dome rotation
is referred to as azimuth motion. The central section of the dome is free to
rotate within the dome, perpendicular to the azimuth, and is referred to as
elevation motion. The control system is designed to compensate for the flight
characteristics of the aircraft.
4.1.6 Sensor/Instrument Measurement Geometry
The six separate detectors view the Sun simultaneously at six independent
wavelengths. The FOV of each detector is set by the entrance aperture to 4
degrees; the inside surfaces of the aperture assembly are anodized a dull black
to reduce internal reflections. The 4-degree FOV was selected to allow for +/-1
degree of tracking error without affecting the solar-radiation signal. The
wavelengths and the full width half maximum (FWHM) of the ATSP are shown in the
following table for all channels.
Wavelength (nm) FWHM (nm)
--------------- ---------
379.8 11.0
451.3 6.2
525.7 9.1
860.5 13.0
940.0 0.2
1059.9 12.7
The system is designed to move in elevation or azimuth at 8 degrees per second.
The acceleration that may occur during a turn is estimated to be 1.0 radian per
second squared. If the instrument should lose lock, the reacquisition occurs
very rapidly as long as the Sun is in the FOV of the instrument. The tracking
system responds quickly because it uses a single rate of 8 degrees per second
for tracking. The solar-tracking system was designed to achieve two objectives:
first, to be able to acquire the Sun starting from a position several degrees
away; and second, to track the Sun with an accuracy of +/-2 degrees in the
presence of aircraft movements.
4.1.7 Manufacturer of Sensor/Instrument
Manufactured by NASA ARC, Moffett Field, CA 94035, Dr. Philip Russell, Principal
Investigator.
4.2 Calibration
4.2.1 Specifications
The detectors are temperature controlled, and the amplifier gains are set with
precision resistors. The resolution of the detector signals is limited by the
12-bit analog-to-digital converter that can resolve 1 part out of 2048 of the 0
to +10v detector signals. The instrument is designed to operate in clear skies,
and it is assumed that over the period of a flight profile, there are no solar
fluctuations.
4.2.1.1 Tolerance
There is evidence in the literature that in the wavelength region of interest,
solar fluctuations would account for less than a 1% variation of the data.
4.2.2 Frequency of Calibration
The instrument was calibrated at the Mt. Lemmon Steward Observatory, Tucson, AZ,
in April 1994 (before the field season) and at the Mauna Loa Observatory, HI in
November 1994 (after the field season).
4.2.3 Other Calibration Information
The calibration coefficients, corrected for Earth-Sun distance, are contained in
the data files.
5. Data Acquisition Methods
The data collection system was based on a Hewlett-Packard HP9816 computer with
floppy disk and printer. This system was used to run data collection, data
processing, and printing software developed by NASA ARC. In addition to the
computer, the data collection system included a multiplexer, a 12-bit analog-to
-digital converter, and electronics to process the aircraft inertial navigation
data. The data are sampled approximately every 2-seconds and are synchronized
with the aircraft data system, which provides the altitude, longitude, and
latitude data. The science data set includes the six detector signals, detector
temperature, tracking error, Sun tracker azimuth angle, Sun tracker elevation
angle, and Universal Time Code (UTC) time. The data were stored on 3.5-inch
floppy disks and were also printed for real-time check and backup. Data were
collected for the duration of the optical flights of the C-130 aircraft and were
collected on the ground before and/or after the flights to determine the total
atmospheric aerosol optical depth.
A new data collection system is under design and construction. It will be based
on a 486 laptop PC running Visual Basic in a Windows environment. Digital-to -
analog conversion will be significantly enhanced and optimized for each channel
using a Dacbook. Data reduction will be simplified because the necessity for
hex-to-ASCII conversion will be eliminated. Several programs currently requiring
processing on minicomputers will be installed on the PC; this will permit
processing to semifinal products in the field (only the postmission calibration
will have to be incorporated into the final products).
6. Observations
6.1 Data Notes
Below is a table of
SPATIAL_COVERAGE C130_SITE C130_LINE_NUM
-------------------- --------- -------------
SSA 429 0
SSA-LAKE 429 9
SSA-LAKE 429 10
SSA-OBS 429 101
SSA-OBS 429 102
SSA-OBS 429 103
SSA-OJP 429 201
SSA-OJP 429 202
SSA-OJP 429 203
SSA-9OA 429 301
SSA-9OA 429 302
SSA-9OA 429 303
SSA-YJP 429 401
SSA-YJP 429 402
SSA-YJP 429 403
SSA-9YA 429 501
SSA-9YA 429 502
SSA-9YA 429 503
SSA-CAL 429 601
SSA-CAL 429 603
SSA-FEN 429 701
SSA-FEN 429 702
SSA-FEN 429 703
SSA 430 0
SSA-MSA 430 1
SSA-MSA 430 2
SSA-MSA 430 3
SSA-MSA 430 4
SSA-MSA 430 5
SSA-MSA 430 6
SSA-MSA 430 7
SSA-MSA 430 8
SSA-MSA 430 9
SSA-MSA 430 10
SSA-MSA 430 11
NSA 431 0
CALIB_FROZEN_LAKE KE 431 1
NSA-OBS 431 101
NSA-OBS 431 102
NSA-OBS 431 103
NSA-FEN 431 201
NSA-FEN 431 202
NSA-FEN 431 203
NSA-OJP 431 301
NSA-OJP 431 302
NSA-OJP 431 303
NSA-YJP 431 401
NSA-YJP 431 402
NSA-YJP 431 403
NSA-9OA 431 601
NSA-9OA 431 602
NSA-9OA 431 603
NSA 432 0
NSA-MSA 432 1
NSA-MSA 432 2
NSA-MSA 432 3
NSA-MSA 432 4
NSA-MSA 432 5
NSA-MSA 432 6
NSA-MSA 432 7
NSA-MSA 432 8
NSA-MSA 432 9
TRANSECT 433 0
TRANSECT 433 1
TRANSECT 433 2
TRANSECT 433 3
TRANSECT 433 4
TRANSECT 433 5
NSA-MSA 999 999
NSA BTW 0
SSA BTW 0
NSA DSC 0
SSA DSC 0
TRANSECT DSC 0
NSA PRE 0
SSA PRE 0
TRANSECT PRE 0
TRANSECT TRN 0
SSA YPA 0
NSA YTH 0
6.2 Field Notes
The ATSP operator normally takes notes of significant events while the
instrument is acquiring data. These notes supplement the real-time display of
detector voltages or optical depths and permit determination of the presence of
variable cloud interference with remote sensing data collection; this feature
often indicates whether or not a given flight line was acceptable or had to be
repeated. If the line was acceptable, then the notes, if any, help identify data
problems during processing. Anyone interested in these notes should contact
RSS-12 personnel at NASA ARC.
7. Data Description
7.1 Spatial Characteristics
The ATSP views the Sun with a 4-degree FOV and typically acquires data every 2
or 3 seconds during flight. A typical ground speed of the C-130 aircraft is 150
m/sec. Hence, data are collected every 300 meters along a flight line. During
spiral descents and ascents, typical vertical rates are 1,000 ft/min or 5 m/sec
so the ATSP samples the vertical column every 10 meters.
7.1.1 Spatial Coverage
Although most of the data were collected over the BOREAS Northern Study Area
(NSA), Southern Study Area (SSA), and tower sites, some data are available over
the transect between the NSA and SSA.
The North American Datum 1983 (NAD83) corner coordinates of the 1,000- by
1,000- km BOREAS region are:
Latitude Longitude
---------- -----------
Northwest 59.97907 N 111.00000 W
Northeast 58.84379 N 93.50224 W
Southwest 51.00000 N 111.00000 W
Southeast 50.08913 N 96.96951 W
The NAD83 corner coordinates of the NSA are:
Latitude Longitude
-------- ---------
Northwest 56.249 N 98.825 W
Northeast 56.083 N 97.234 W
Southwest 55.542 N 99.045 W
Southeast 55.379 N 97.489 W
The NAD83 corner coordinates of the SSA are:
Latitude Longitude
-------- ---------
Northwest 54.321 N 106.228 W
Northeast 54.225 N 104.237 W
Southwest 53.515 N 106.321 W
Southeast 53.420 N 104.368 W
7.1.2 Spatial Coverage Map
Not available.
7.1.3 Spatial Resolution
The sunphotometer's spatial resolution was variable based on aircraft maneuvers
and flight speed. If the sunphotometer was acquiring data every 2-seconds and
the C-130 was flying level at 150 m/sec, then the ground resolution was 300
meters.
7.1.4 Projection
The coordinates in the data files are from the C-130 internal navigation system
(INS). The INS geographic position data are from the onboard Global Positioning
System (GPS), which uses NAD83.
7.1.5 Grid Description
Not applicable.
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
Data were acquired during three IFCs in 1994. The days and times were:
Date Time (GMT)
----------- -----------------
25-May-1994 15:21:28-18:02:23
26-May-1994 12:51:41-19:15:20
31-May-1994 13:30:20-16:30:26
01-Jun-1994 13:34:43-15:20:41
04-Jun-1994 13:08:07-18:53:02
06-Jun-1994 15:07:25-17:33:26
07-Jun-1994 14:15:28-17:08:53
08-Jun-1994 14:04:34-22:29:33
20-Jul-1994 15:12:04-18:25:55
21-Jul-1994 13:46:30-17:33:00
22-Jul-1994 14:04:43-17:27:18
23-Jul-1994 13:44:38-14:41:09
24-Jul-1994 13:50:45-14:08:24
26-Jul-1994 16:08:00-17:15:44
29-Jul-1994 13:21:03-18:16:19
31-Jul-1994 12:59:18-18:24:25
02-Aug-1994 13:09:15-18:07:19
03-Aug-1994 14:37:00-16:46:39
04-Aug-1994 12:45:25-22:23:19
08-Aug-1994 12:47:45-15:43:01
09-Aug-1994 12:36:04-19:20:08
10-Aug-1994 13:21:34-18:08:37
31-Aug-1994 14:05:24-19:55:39
01-Sep-1994 00:40:38-14:27:32
02-Sep-1994 13:51:45-17:10:32
03-Sep-1994 14:08:56-16:53:50
06-Sep-1994 15:03:13-18:33:01
08-Sep-1994 14:02:31-17:41:14
09-Sep-1994 15:49:51-16:00:32
7.2.2 Temporal Coverage Map
Not available.
7.2.3 Temporal Resolution
The ATSP typically samples every 2 or 3 seconds during flight, but the sampling
rate is under computer control and can be modified if necessary.
7.3 Data Characteristics
Data characteristics are defined in the companion data definition file
(sunphair.def).
7.4 Sample Data Record
Sample data format shown in the companion data definition file (sunphair.def).
8. Data Organization
8.1 Data Granularity
All of the Airborne Tracking Sunphotometer Measurement Data are contained in one
file.
8.2 Data Format(s)
The data file contains numerical and character fields of varying length
separated by commas. The character fields are enclosed with single apostrophe
marks. There are no spaces between the fields. Sample data records are shown in
the companion data definition files (sunphair.def).
9. Data Manipulations
9.1 Formulae
For all sunphotometer channels except the 940 nm, the Bouguer-Lambert-Beer
extinction law was used to describe the attenuation of solar radiation:
V = (R'/R)^2 V0 exp(-m tau) = V'0 exp(-m tau)
where V is the output voltage of the detector at a given wavelength, V0 is the
zero air-mass voltage intercept at that wavelength for the mean Earth-Sun
separation R', R is the Earth-Sun separation at the time of observation, m is
the atmospheric air mass between the instrument and the Sun, tau is the
wavelength-dependent total vertical optical depth above the sunphotometer, and
V'0 is the zero-air-mass voltage intercept for the Earth-Sun separation R at the
time of observation. The 940-nm channel requires different processing and is not
included this data set.
The logarithm of the above equation,
ln V = ln V'0 - m tau,
is used in calibration to provide the V'0 values for each channel (i.e., zero
air mass Langley plot intercept voltages). When the detector voltages are
plotted against the air mass, the intercept is the V'0. After calibration, this
equation can be solved for tau to provide the total optical depth. The total
optical depth is then decomposed using
tau = tau_r + tau_a + tau_O3 + tau_NO2 + tau_H2O,
where these terms are the optical depth due to Rayleigh scattering, aerosols,
ozone, NO2, and water vapor, respectively. The source for each of these terms is
given in Section 7.3. Water vapor was ignored because it contributes in the 940-
nm channel.
This description is taken from Spanner et al., 1990, where more information
concerning the data processing can be found.
9.1.1 Derivation Techniques and Algorithms
A description of algorithms can be found in Spanner et al., 1990.
9.2 Data Processing Sequence
9.2.1 Processing Steps
The steps for processing are as follows: 1) acquire the data; 2) run a program
to calculate all the variables, including solar zenith angle, air mass, Rayleigh
optical depth, and instantaneous optical depth (total optical depth minus
Rayleigh optical depth); 3) calculate NO2 and ozone optical depths from Noxon et
al., 1979, and TOMS data, respectively; and 4) subtract NO2 and ozone to derive
aerosol optical depth.
The ozone abundance was determined from the TOMS satellite instrument convolved
with ozone absorption coefficients from Penney (1979). The values calculated for
NO2 and ozone optical depth were subtracted from the instantaneous optical depth
to derive the aerosol optical depth, are provided in the data files.
9.2.2 Processing Changes
None given.
9.3 Calculations
9.3.1 Special Corrections/Adjustments
No special corrections or adjustments have been made.
9.3.2 Calculated Variables
Description of algorithms can be found in Spanner et al., 1990.
9.4 Graphs and Plots
Plots have been provided to BORIS and can be made available upon request.
10. Errors
10.1 Sources of Error
Calibration errors are the main source of error in the derivation of aerosol
optical depth.
10.2 Quality Assessment
10.2.1 Data Validation by Source
Data were compared with the RSS-11 field sunphotometer (see related data sets,
Section 1.6).
10.2.2 Confidence Level/Accuracy Judgment
The data are of high quality, because a good calibration of the instrument was
performed before and after the BOREAS field collection effort.
10.2.3 Measurement Error for Parameters
Uncertainties for the aerosol optical depths were determined by using
uncertainty propagation through the algorithm. The aerosol optical depth
uncertainty is dependent on the uncertainty in the Rayleigh, ozone, and
NO2optical depths, as well as the uncertainty in the intercept voltage
(calibration error), instantaneous measurement, and airmass. Aerosol optical
depth uncertainties are given in the data files and are summarized in Section
7.3 of this document.
10.2.4 Additional Quality Assessments
None.
10.2.5 Data Verification by Data Center
Visual review and use of selected subsets of the data have shown them to be of
good quality with no noteworthy problems.
11. Notes
11.1 Limitations of the Data
None.
11.2 Known Problems with the Data
None.
11.3 Usage Guidance
The values of aerosol optical depth are accurate instantaneous values of aerosol
optical depth. These data were taken frequently; therefore, under conditions of
rapid variability in cloudiness or haze, the data may not be internally
consistent or appropriate. It is useful to calculate averages of aerosol optical
depth over periods of time to get a more accurate measure of the average
conditions at a site.
Users should take note that the daily extrated files have a large size range
(400 to 38,000 records)
11.4 Other Relevant Information
The aerosol optical depth at 941 nm was not calculated because this channel
primarily measures absorption due to water vapor.
12. Application of the Data Set
These data can be used for correcting various visible and infrared satellite and
aircraft image products or for characterizing the atmospheric aerosols at the
times of the flights.
13. Future Modifications and Plans
Future plans for the airborne instrument include the design and development of a
new 14-channel airborne instrument.
14. Software
14.1 Software Description
NASA ARC software was developed in FORTRAN on a VAX to implement the data
processing procedure described in Section 9.1. Input data include sunphotometer
data files as well as ozone and NO2 optical depth parameters. Aerosol optical
depths were calculated and written to the data files. No special software is
needed to read the data files because they are stored comma delimited.
14.2 Software Access
This software is used to generate the data product from the detector voltages
and is not needed to use the data.
15. Data Access
15.1 Contact Information
Ms. BethNelson
BOREAS Data Manager
NASA GSFC
Greenbelt, MD
(301) 286-4005
(301) 286-0239 (fax)
beth@ltpmail.gsfc.nasa.gov
15.2 Data Center Identification
See Section 15.1.
15.3 Procedures for Obtaining Data
Users may place requests by telephone, electronic mail, or fax.
15.4 Data Center Status/Plans
The RSS-12 C130 sunphotometer data are available from the Earth Observing System
Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL)
Distributed Active Archive Center(DAAC). The BOREAS contact at ORNL is:
ORNL DAAC User Services
Oak Ridge National Laboratory
Oak Ridge, TN
(423) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov
16. Output Products and Availability
16.1 Tape Products
None.
16.2 Film Products
None.
16.3 Other Products
The data are available as tabular ASCII files.
17. References
17.1 Platform/Sensor/Instrument/Data Processing Documentation
None.
17.2 Journal Articles and Study Reports
Bruegge, C.J., R.N. Halthore, B. Markham, M. Spanner, and R. Wrigley. 1992.
Aerosol optical depth retrievals over the Konza prairie. Journal of Geophysical
Research 97(D17):18743-18758.
King, M., D. Bryne, B. Herman, and J. Reagan. 1978. Aerosol size distributions
obtained by inversion of spectral optical depth measurements. J. Atmos. Sci.
35:2153-2167.
Noxon, J. 1979. Stratospheric NO2, 2, Global behavior, J. Geophys. Res. 84:5067-
5076.
Penney, C.M. 1979. Study of temperature dependence of the Chappuis band
absorption of ozone, NASA Contract Rep. 158977, General Electric Company,
Schenectady, N.Y.
Russell, P., J. Livingston, E. Dutton, R. Pueschel, J. Reagan, T. DeFoor, M.
Box, D. Allen, P. Pilewskie, B. Herman, S. Kinne, and D. Hofmann. 1994. Pinatubo
and pre-Pinatubo optical depth spectra: Mauna Loa measurements, comparisons,
inferred particle size distributions, radiative effects, and relationship to
lidar data. J. Geophys. Res. 98:22,969-22,985.
Sellers, P.and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).
Sellers, P.and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).
Sellers, P.and F. Hall and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere
Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94).
Sellers, P., F. Hall and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere
Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J.
Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J.Ranson, D. Lettenmaier, and D.E.
Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and
early results from the 1994 field year. Bulletin of the American Meteorological
Society. 76(9):1549-1577.
Sellers, P.and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in
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Determination of atmospheric optical properties for the First ISLSCP Field
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Atmospheric correction of remotely sensed image data by a simplified model.
Journal of Geophysical Research 97(D17):18797-18814.
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Applied Optics 19:3427-3428.
17.3 Archive/DBMS Usage Documentation
18. Glossary of Terms
air mass - secant of the solar zenith angle
optical depth - an indirect measure of the size and number of
particles present in a given column of air, which is a
measure of the extinction of the direct solar beam by
aerosols and particulates in the atmosphere, or by
scattering. Also referred to as optical thickness.
phase function - a measure of the light scattered by a particle as a
function of angle with respect to the original
direction of propagation
radiometer - an instrument for measuring radiant energy
Rayleigh - wavelength-dependent scattering directly proportional
scattering to (1 + cos2(angle)) and indirectly proportional to
wavelength4
single - the fraction of light intercepted and scattered by a
scattering single particle
albedo
19. List of Acronyms
AGSP - Automated Ground Sunphotometer
ARC - Ames Research Center
ATSP - Airborne Tracking Sunphotometer
BOREAS - BOReal Ecosystem-Atmosphere Study
BORIS - BOReas Information System
DAAC - Distributed Active Archive Center
EOS - Earth Observing System
EOSDIS - EOS Data and Information System
FIFE - First ISLSCP Field Experiment
FOV - Field-of-View
FWHM - Full Width Half Maximum
GMT - Greenwich Mean Time
GPS - Global Positioning System
GSFC - Goddard Space Flight Center
IFC - Intensive Field Campaign
INS - Inertial Navigation System
ISLSCP - International Satellite Land Surface Climatology Project
MAS - MODIS Airborne Simulator
MODIS - MODerate-resolution Imaging Spectrometer
NASA - National Aeronautics and Space Administration
NSA - Northern Study Area
ORNL - Oak Ridge National Laboratory
PANP - Prince Albert National Park
RSS-12 - Remote Sensing Science Team 12
SSA - Southern Study Area
TM - Thematic Mapper
TMS - Thematic Mapper Simulator
TOMS - Total Ozone Mapping Spectrometer
URL - Uniform Resource Locator
UTC - Universal Time Code
20. Document Information
20.1 Document Revision Dates
Written: 07-Jan-1997
Last Updated: 04-May-1998
20.2 Document Review Dates
BORIS Review: 19-May-1997
Science Review: 27-Jun-1997
20.3 Document ID
20.4 Citation
Please acknowledge the NASA/ARC investigation (RSS-12) and Michael Spanner,
Principal Investigator, if these data are used or referenced. If appropriate,
the references cited in Section 17 may be used.
20.5 Document Curator
20.6 Document URL
Keywords
---------------
Aerosols
Optical Thickness
Ozone
RSS12_Air_Sunphoto.doc
05/26/98