Aerosol optical depths were recorded at various locations within the FIFE site. A Normal Incident Pyrheliometer (NIP) and a Reagan sunphotometer was used to collect data during the IFCs. These data showed that daily averages span a range of 0.05 to 0.28 in the mid-visible wavelength (Bruegge et al., 1992a). Diurnal variations were recorded. The afternoon optical depths are greater than those of the morning by as much as 0.07.
These data are analyzed using the Langley technique. Rayleigh optical depth is subtracted, and aerosol, ozone, and water vapor abundance's simultaneously measured. In retrieving ozone, a Junge aerosol model is assumed, thus, the natural log of aerosol optical depth is linear with wavelength (Bruegge et al., 1992a). This contrasts with other experimental approaches used by investigators in which an ozone abundance is assumed (Halthore and Markham 1992). This approach allows measurement of aerosol, but is limited by the accuracy of the ozone data.
The NIPS and Reagan Sunphotometer Optical Thickness study compared various ground and image-based techniques used to characterize the atmosphere. These data can be used to atmospherically correct remotely sensed data (see Markham and Halthore 1992). They can also be used to derive aerosol size distribution (King et al., 1978) and thereby estimate the phase function.
Aerosol optical depths were recorded at various locations within the FIFE site. A Normal Incident Pyrheliometer (NIP) and a Reagan sunphotometer was used to collect data during the IFCs. These data are analyzed using the Langley technique. The NIPS and Reagan Sunphotometer Optical Thickness Data Set contains surface pressure, surface temperature, optical visibility, ozone optical thickness, Rayleigh optical thickness, aerosol optical thickness, and total optical thickness data.
The objective was to compare various ground and image-based techniques used to characterize the atmosphere. These data are used to remove atmospheric absorption and scattering from remote sensing scenes so that surface parameters can be retrieved. An evaluation of the effects of uncorrected atmospheric absorption and scattering on various vegetation indices and subsequent biophysical parameter estimations was also undertaken.
Surface pressure, surface temperature, optical visibility, ozone optical thickness, Rayleigh optical thickness, aerosol optical thickness, and total optical thickness.
Aerosol optical depths were recorded at various locations within the FIFE site. A Normal Incident Pyrheliometer (NIP) was used to collect data during IFC-1. During IFC-2 through IFC-5 a Reagan sunphotometer was used. Data are available from the Reagan Instrument for 26 days in 1987, and for 7 days in 1988. These data showed that daily averages span a range of 0.05 to 0.28 in the mid-visible wavelength (Bruegge et al., 1992a). Diurnal variations were recorded. The afternoon optical depths are greater than those of the morning by as much as 0.07.
These data can be used to atmospherically correct remotely sensed data (see Markham and Halthore 1992). They can also be used to derive aerosol size distribution (King et al., 1978) and thereby estimate the phase function.
OPTICAL_THICK_BRUEGGE_DATA.
Dr. Carol J. Bruegge
Jet Propulsion Laboratory
Assessment of Techniques to Characterize the Atmosphere and to Extract Vegetation Cover Metrics.
Dr. Carol J. Bruegge
Jet Propulsion Laboratory
Pasadena, CA 91109
Tel.: (818) 354-4956
Email: cjb@jord.jpl.nasa.gov
Please cite the following paper in any work or publication using these data:
Bruegge, C.J., et al., 1992. Aerosol optical depth retrievals over the Konza Prairie. J. Geophys. Res. 97:18743-18758.
In FIFE, the Reagan sunphotometer was used to track the Sun through a range of airmasses. NIP, which is an autotracking sunphotometer was also used. These data are analyzed using the Langley technique. Rayleigh optical depth is subtracted, and aerosol, ozone, and water vapor abundance's simultaneously measured. In retrieving ozone, a Junge aerosol model is assumed, thus, the natural log of aerosol optical depth is linear with wavelength (Bruegge et al., 1992a). This contrasts with other experimental approaches used by investigators in which an ozone abundance is assumed (Halthore and Markham 1992). This approach allows measurement of aerosol, but is limited by the accuracy of the ozone data. For more details, see the Theory of Measurements Section in the Optical Thickness Calibration Reference Guide Document on FIFE CD-ROM Volume 1.
The Reagan Sunphotometer is a spectrally filtered, solar-pointing radiometer. It has 10 spectral channels, each about 10 nm in bandwidth, fast response, low noise, and an internal filter wheel. Features of Reagan Sunphotometer are:
The Normal Incident Pyrheliometer (NIP) is an Eppley-type autotracking sunphotometer. The NIP measures at six wavelength channels: 0.485, 0.56, 0.66, 0.83, 1.65, and 2.2 um. The instrument has a thermopile detector, low output voltage (millivolts) and a slow response (seconds). The instrument used for FIFE in 1987 frequently required a dark current reading to be subtracted from the direct beam results.
Ground-based.
Ground-based stationary tripod.
The aim was to measure aerosol optical thickness and characterize the effects of atmospheric absorption and scattering on remotely sensed imagery.
Aerosol optical thickness, pressure, and temperature.
The output voltages of the instruments are proportional to the incident irradiances within a given band, although no calibration relating voltage to physical units is required. Data are acquired every minute at high airmass, and every 15 minutes near Solar noon. A Langley plot method is used to obtain optical thickness.
The instrument tracks the Sun, and the full field of view is about 2 degrees for both the Reagan and NIP sunphotometers.
Reagan Sunphotometer
University of Arizona
Tucson, AZ 85721
NIP
Eppley Laboratory
12 Sheffield Avenue
Newport, RI 24840
Instrument calibration for each sunphotometer was achieved using in-situ data acquired on clear days, with a minimal airmass span of 3. Only morning data collections were considered for a calibration.
See the Sensor/Instrument Description Section.
Temperature stability of +/- 0.5 degrees C.
Calibration was made continuously throughout the experiment, using data acquired under clear conditions (i.e., aerosol optical depth of less than 0.17 in the mid-visible wavelength).
The Reagan was calibrated alongside the SXM-2 (a Goddard instrument also used to report FIFE optical depth data) during IFC-5. Pre- and post-FIFE calibration were performed at mountain sites for SXM-2 with frequent inter-comparisons with both Reagan sunphotometer and the C-130 airborne tracking sunphotometer. A description of the calibration performed during IFC-4 is given in the Optical Thickness Calibration Reference Document. found on FIFE CD-ROM Volume 1.
Data were acquired during the first IFC with the NIPS, and during the rest of the FIFE study with the Reagan sunphotometer. The Reagan instrument was first aligned to the Sun, then a 10-position filter wheel was manually rotated allowing relative spectral irradiances to be recorded. Data acquisition cycle was about 30 seconds. The next cycle was repeated 30 seconds to 15 minutes later, depending upon time of day. NIPS was used in a similar manner to acquire data, except that the instrument tracks the Sun automatically and measures radiation in only six channels.
Not available.
Available from PI upon request (see the Investigator(s) Name And Title Section).
The FIFE study area, with areal extent of 15 km by 15 km, is located south of the Tuttle Reservoir and Kansas River, and about 10 km from Manhattan, Kansas, USA. The northwest corner of the area has UTM coordinates of 4,334,000 Northing and 705,000 Easting in UTM Zone 14.
The sunphotometer measurements were made at the following locations for the NIPS and Reagan instruments:
SITEGRID INSTRUMENT NORTHING EASTING LATITUDE LONGITUDE ELEV
-------- ---------- -------- -------- -------- --------- -----
0506-SPN NIPS 4332962 706132 39 07 24 -96 36 56 315
2730-SPN NIPS 4328558 711081 39 04 57 -96 33 35 440
1140-SPR REAGAN 4331819 713013 39 06 41 -96 32 11 420
1709-SPR REAGAN 4330541 706748 39 06 05 -96 36 33 345
2730-SPR REAGAN 4328558 711081 39 04 57 -96 33 35 440
3639-SPR REAGAN 4326756 712885 39 03 57 -96 32 22 443
4631-SPR REAGAN 4324830 711253 39 02 56 -96 33 32 405
8739-SPR REAGAN 4316698 712892 38 58 31 -96 32 33 440
Not available.
These are point data. Retrieved optical depth data is valid for 0.5 km horizontally. The atmosphere is assumed to be spatially homogeneous over this scale.
Not available.
Not available.
NIPS data were collected during IFC-1, from May 30, through June 6, 1987. The REAGAN data were collected during IFCs 2-5, from June 26, 1987 through October 8, 1987, and from July 28 through August 8 in 1989.
Not available.
Sampling frequency varies between 1 and 15 minutes. Data were recorded continuously from morning until Solar noon during cloud-free days. Several afternoon data sets were recorded for comparison. Data were always collected coincident with an aircraft or satellite overpass.
The SQL definition for this table is found in the OT_BRUG.TDF file located on FIFE CD-ROM Volume 1.
Parameter/Variable Name
Parameter/Variable Description Range Units Source
SITEGRID_ID This is a FIS grid location code. Site grid codes (SSEE-III) give the south (SS) and the east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument
STATION_ID The station ID designating the location of the observations.
OBS_DATE The date of the observations, in the format (DD-MMM-YY).
START_TIME The starting time of the [GMT] observation run in GMT. The format is (HHMM).
DURATION The duration of the observation run in the format HHMM. The data are averaged over this interval starting at START_TIME.
INSTR_ID The code name for the instrument used to make the observations.
SURFACE_PRESS The surface pressure at the time [millibars] of the observation.
SURFACE_TEMP The temperature during the [degrees observation. Celsius]
OPTCL_VISIBILITY The optical visibility in km, as [km] computed from AEROSOL at 550 nm using Elterman vertical profile. [km]
WAVLEN The wavelength at which the [nm] observation was made.
OZONE_OPTCL_THICK The Ozone Optical Thickness, caused by ozone particles in the air.
RAYLEIGH_OPTCL_THICK The Rayleigh Optical Thickness, caused by molecular scattering.
AEROSOL_OPTCL_THICK The Aerosol Optical Thickness, caused by colloidal particles suspended in the air.
TOTAL_OPTCL_THICK The Total Optical Thickness, on a vertical path from surface to space.
MIE_CONSTANT_1 MIE_1 and MIE_2 are used to compute AEROSOL_OPTCL_THICK at arbitrary wavelengths.
MIE_CONSTANT_2 MIE_1 and MIE_2 are used to compute AEROSOL_OPTICAL_THICK at arbitrary wavelengths.
ABUNDANCE_OF_OZONE The column abundance of ozone, reduced to Standard Temperature and Pressure.
WEATHER A comment on the weather conditions at the time of the observation.
FIFE_DATA_CRTFCN_CODE * The FIFE Certification Code for the data, in the following format: CPI (Certified by PI), CPI-??? (CPI - questionable data).
LAST_REVISION_DATE data, in the format (DD-MMM-YY).
Footnote:
Valid levels.
The primary certification codes are: EXM Example or Test data (not for release). PRE Preliminary (unchecked, use at your own risk). CPI Checked by Principal Investigator (reviewed for quality). CGR Checked by a group and reconciled (data comparisons and cross-checks).
The certification code modifiers are: PRE-NFP Preliminary - Not for publication, at the request of investigator. CPI-MRG PAMS data that are "merged" from two separate receiving stations to eliminate transmission errors. CPI-??? Investigator thinks data item may be questionable.
SITEGRID_ID STATION_ID OBS_DATE START_TIME DURATION INSTR_ID
----------- ---------- ---------- ---------- -------- --------
0506-SPN 401 30-MAY-87 1900 300 NIPS
0506-SPN 401 30-MAY-87 1900 300 NIPS
0506-SPN 401 30-MAY-87 1900 300 NIPS
0506-SPN 401 30-MAY-87 1900 300 NIPS
SURFACE_PRESS SURFACE_TEMP OPTCL_VISIBILITY WAVLEN OZONE_OPTCL_THICK
------------- ------------ ---------------- ------- -----------------
950.00 27.0 83.2 485.0 9.9999
950.00 27.0 83.2 560.0 9.9999
950.00 27.0 83.2 660.0 9.9999
950.00 27.0 83.2 830.0 9.9999
RAYLEIGH_OPTCL_THICK AEROSOL_OPTCL_THICK TOTAL_OPTCL_THICK MIE_CONSTANT_1
-------------------- ------------------- ----------------- --------------
.1541 .1605 .3210 -1.354
.0856 .1243 .2393 -1.354
.0439 .0927 .1884 -1.354
.0174 .0617 .0810 -1.354
MIE_CONSTANT_2 ABUNDANCE_OF_OZONE WEATHER
-------------- ------------------ -----------
-1.780 999.90 CLDY/CIR
-1.780 999.90 CLDY/CIR
-1.780 999.90 CLDY/CIR
-1.780 999.90 CLDY/CIR
FIFE_DATA_CRTFCN_CODE LAST_REVISION_DATE
--------------------- ------------------
CPI 04-AUG-88
CPI 04-AUG-88
CPI 04-AUG-88
CPI 04-AUG-88
These are point data. Retrieved optical depth data is valid for 0.5 km horizontally. Sampling frequency varied between 1 and 15 minutes.
A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.
The CD-ROM file format consists of numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe. There are no spaces between the fields. Each file begins with five header records. Header records contain the following information: Record 1 Name of this file, its table name, number of records in this file, path and name of the document that describes the data in this file, and name of principal investigator for these data. Record 2 Path and filename of the previous data set, and path and filename of the next data set. (Path and filenames for files that contain another set of data taken at the same site on the same day.) Record 3 Path and filename of the previous site, and path and filename of the next site. (Path and filenames for files of the same data set taken on the same day for the previous and next sites (sequentially numbered by SITEGRID_ID)). Record 4 Path and filename of the previous date, and path and filename of the next date. (Path and filenames for files of the same data set taken at the same site for the previous and next date.) Record 5 Column names for the data within the file, delimited by commas. Record 6 Data records begin. Each field represents one of the attributes listed in the chart in the Data Characteristics Section and described in detail in the TDF file. These fields are in the same order as in the chart.
Junge aerosol model was assumed (Bruegge et al., 1992a). Langley plot method was used. This method has been discussed extensively in the literature (Shaw et al., 1973; Halthore et al., 1992). Average optical depths are reported. The following formulae were used to derive aerosol and column abundance of ozone:
where:
The optical thickness data is created by:
None.
None available at this revision.
None available at this revision.
Aerosol and column abundance of ozone.
None.
Temporally varying atmosphere may introduce errors when using average optical depth, rather than instantaneous values. Instantaneous data were available and reported for latter IFCs only.
Extensive intercomparison was done with other sunphotometer teams in 1989. For a full description see the Optical Thickness Calibration Reference Document. on FIFE CD-ROM Volume 1.
Reagan data had the state-of-art accuracy. The total optical depth data obtained during IFCs 2-5 are believed to be accurate to within +/- 0.01 absolute. These data are sufficient to retrieve surface reflectance to within 0.01. The accuracy of data acquired during IFC-1 are believed less accurate (to 0.05) due to the NIPS instrument limitations.
All data submitted to FIFE have an uncertainty of 1% in the calibration, which translates to an absolute uncertainty in aerosol optical thickness of 0.01 per airmass.
Sensitivity studies and intercomparisons were used to infer error. The Reagan data were believed to be good to 0.01 in optical depth.
No quantitative assessment was made for the NIPS data, or the errors referred to in the Sources of Error Section.
FIS staff applied a general Quality Assessment (QA) procedure to these data to identify inconsistencies and problems for potential users. As a general procedure, the FIS QA consisted of examining the maximum, minimum, average, and standard deviation for each numerical field in the data table. An attempt was made to find an explanation for unexpected high or low values, values outside of the normal physical range for a variable, or standard deviations that appeared inconsistent with the mean. In some cases, histograms were examined to determine whether outliers were consistent with the overall distribution of the data.
The discrepancies, which were identified, are reported as problems in the Known Problems with the Data Section.
The data verification performed by the ORNL DAAC deals with the quality of the data format, media, and readability. The ORNL DAAC does not make an assessment of the quality of the data itself except during the course of performing other QA procedures as described below.
The FIFE data were transferred to the ORNL DAAC via CD-ROM. These CD-ROMs are distributed by the ORNL DAAC unmodified as a set or in individual volumes, as requested. In addition, the DAAC has incorporated each of the 98 FIFE tabular datasets from the CD-ROMs into its online data holdings. Incorporation of these data involved the following steps:
Each distinct type of data (i.e. "data set" on the CD-ROM), is accompanied by a documentation file (i.e., .doc file) and a data format/structure definition file (i.e., .tdf file). The data format files on the CD-ROM are Oracle SQL commands (e.g., "create table") that can be used to set up a relational database table structure. This file provides column/variable names, character/numeric type, length, and format, and labels/comments. These SQL commands were converted to SAS code and were used to create SAS data sets and subsequently to input data files directly from the CD-ROM into a SAS dataset. During this process, file names and directory paths were captured and metadata was extracted to the extent possible electronically. No files were found to be corrupted or unreadable during the conversion process.
Additional Quality Assurance procedures were performed as follows:
As errors are discovered in the online tabular data by investigators, users, or DAAC staff, corrections are made in cooperation with the principal investigators. These corrections are then distributed to users. CD-ROM data are corrected when re-mastering occurs for replenishment of CD-ROM stock.
Not available.
None known at this revision.
Among all the optical thickness data reported by the various FIFE teams, IFC-2 data had the largest (0.05) discrepancy. This was believed to be an instrument calibration problem. Data quality was still good.
None.
These data can be used to atmospherically correct remotely sensed data (see Markham and Halthore 1992). They can also be used to derive aerosol size distribution (King et al., 1978) and thereby estimate the phase function.
The FIFE field campaigns were held in 1987 and 1989 and there are no plans for new data collection. Field work continues near the FIFE site at the Long-Term Ecological Research (LTER) Network Konza research site (i.e., LTER continues to monitor the site). The FIFE investigators are continuing to analyze and model the data from the field campaigns to produce new data products.
Software to access the data set is available on the all volumes of the FIFE CD-ROM set. For a detailed description of the available software see the Software Description Document.
ORNL DAAC User Services
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
USA
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
Users may place requests by telephone, electronic mail, or FAX. Data is also available via the World Wide Web at http://daac.ornl.gov.
FIFE data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.
The NIPS and Reagan Sunphotometer Optical Thickness data are available on FIFE CD-ROM Volume 1. The CD-ROM filename is as follows:
\DATA\OPTICAL\OT_BRUG\GRIDxxxx\ydddgrid.0TB.
Where xxxx is the four digit code for the location within the FIFE sitegrid. Note: capital letters indicate fixed values that appear on the CD-ROM exactly as shown here, lower case indicates characters (values) that change for each path and file.
The format used for the filename is: ydddgrid.sfx, where grid is the four-number code for the location within the FIFE sitegrid, y is the last digit of the year (e.g., 7 = 1987, and 9 = 1989), and ddd is the day of the year (e.g., 061 = sixty-first day in the year). The filename extension (.sfx), identifies the data set content for the file (see the Data Characteristics Section) and is equal to .OTB for this data set.
Halthore, R.N., C.J. Bruegge, and B.L. Markham. 1990. Aerosol optical thickness measurements during FIFE'89. Presented at the AMS Symposium on the First ISLSCP Field Experiment (FIFE). Anaheim, CA.
Bruegge, C.J., R.N. Halthore, B.L. Markham, M. Spanner and R. Wrigley. 1992a. Aerosol optical depth retrievals over the Konza Prairie. J. Geophys. Res. 97:18,743-18,758.
Bruegge, C.J., J.E. Conel, R.O. Green, J.S. Margolis, G. Toon and R.G. Holm. 1992b. Water-vapor column abundance retrievals. J. Geophys. Res. 97:18,759-18,768.
Halthore, R.N., and B.L. Markham. 1992. Overview of Atmospheric Correction and radiometric calibration efforts during FIFE. J. Geophys. Res. 97:18,731-18,742.
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.
Markham, B.L., R.N. Halthore, and S.J. Goetz. 1992. Surface reflectance retrieval from satellite and aircraft sensors during FIFE. J. Geophys. Res. 97:18,785-18,795.
Shaw, G.E., J.A. Reagan, and B.M. Herman. 1973. Investigations of atmospheric extinction using direct solar radiation measurements made with a multiple wavelength radiometer. J. Appl. Meteorol. 12:374-380.
Contact the EOS Distributed Active Archive Center (DAAC) at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee (see the Data Center Identification Section). Documentation about using the archive and/or online access to the data at the ORNL DAAC is not available at this revision.
A general glossary for the DAAC is located at Glossary.
A general list of acronyms for the DAAC is available at Acronyms.
April 26, 1994 (citation revised on October 14, 2002).
This document has been reviewed by the FIFE Information Scientist to eliminate technical and editorial inaccuracies. Previous versions of this document have been reviewed by the Principal Investigator, the person who transmitted the data to FIS, a FIS staff member, or a FIFE scientist generally familiar with the data. It is believed that the document accurately describes the data as collected and as archived on the FIFE CD-ROM series.
Bruegge, C. J. 1994. Optical Thickness Data: Bruegge (FIFE). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/62. Also published in D. E. Strebel, D. R. Landis, K. F. Huemmrich, and B. W. Meeson (eds.), Collected Data of the First ISLSCP Field Experiment, Vol. 1: Surface Observations and Non-Image Data Sets. CD-ROM. National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. (available from http://www.daac.ornl.gov).