Optical Thickness Data: Ground (OTTER)

Summary:

Field sun photometer data collected from 1990 through 1991 is used to provide quantitative atmospheric correction to remotely sensed data of forest reflectance and radiance.

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:

Data Set Identification:

Optical Thickness Data: Ground (OTTER)

Data Set Introduction:

The Oregon Transect Ecosystem Research (OTTER) Project was a cooperative effort between NASA and several universities to discern the ecology of western coniferous forests using remote sensing technology supported by gound observations. OTTER is an interdisciplinary project that tested a model that estimated the major fluxes of carbon, nitrogen, and water through a temperate coniferous forest ecosystem.

Six Oregon sites across an elevational and climatic gradient were intensively studied. The transect began at the Pacific coast at the site called Cascade Head, passed through the outskirts of Corvallis, through a dense Douglas fir forest at Scio, through a mountain hemlock/subalpine fir community at Santiam Pass, through a Ponderosa pine community near Metolius, and ended at a site east of Sisters called Juniper. In all, the transect stretched some 300 kilometers west to east.

Goals of the project were to simulate and predict ecosystem processes such as photosynthesis, transpiration, above-ground production, nitrogen transformation, respiration, decomposition, and hydrologic processes; combine field, lab, and remote sensing techniques to estimate key vegetaion and environmental parameters; construct a "geo-referenced" database for extrapolation and testing of principles, techniques, and prediction; and verify the predictions through direct measurements of process rates or controls on processes.

Objective/Purpose:

OTTER was designed to study the ability of remote sensing to detect biophysical characteristics of plant canopies. The data sets correlating to this document provide quantitative atmospheric correction to remotely sensed data of forest reflectance and radiance.

Summary of Parameters:

One parameter was investigated: The total optical thickness.

Discussion:

Field sunphotometer data were acquired during the OTTER Multi-sensor Aircraft Campaigns (MAC) in 1990 and 1991. Sunphotometer data were acquired concurrently with ER-2 (TMS and AVIRIS) and C-130 (ASAS and NS001) overpasses, when possible. In addition, some of the sunphotometer measurements were acquired simultaneously with ultra-light flights (Barnes MMR and Spectron 590 and 393). Two sunphotometers were used during the OTTER MAC; both were manufactured by Dr. John Reagan at the University of Arizona. Measurements made by the two sunphotomers are nearly identical, therefore, data from instruments 1 and 2 can be used interchangeably.

Related DataSets:

Canopy Chemistry Forest-BGC Model Leaf Area Index Data Leaf Reflectances: LICOR Leaf Reflectances: Perkin-Elmer Meteorology Optical Thickness Data: Aircraft Reflectance Reference Targets SE-590 Field-Measured Reflectances SE-590 Lab-Measured Reflectances SE-590 Landscape Reflectances SE-590 Low Altitude Reflectances Timber Measurements

2. Investigator(s):

Investigator(s) Name and Title:

Name: Michael Spanner

Addresses: NASA Ames Research Center

Telephone Numbers: 1-(415)-604-3620

Electronic Mail Address: mspanner@gaia.arc.nasa.gov

Title of Investigation:

Field Sunphotometer Data

Contact (for Data Production Information):

Name: ORNL DAAC User Services Office

Address: Oak Ridge National Laboratory U.S.A.

Telephone Number: 1-(865)-241-3952

Electronic Mail Address: ornldaac@ornl.gov

3. Theory of Measurements:

Information not available.

4. Equipment:

Sensor/Instrument Description:

Sunphotometer data were acquired concurrently with ER-2 (TMS and AVIRIS) and C-130 (ASAS and NS001) overpasses, when possible. In addition, some of the sunphotometermeasurements were acquired simultaneously with ultra-light flights (Barnes MMR and Spectron 590 and 393). Measurements made by the two sunphotomers are nearly identical, therefore, data from instruments 1 and 2 can be used interchangeably.

Collection Environment:

Sunphotometer data were acquired at each OTTER site during the aircraft overflight periods in February, March, June, August and October of 1990 and in May and June of 1991.

Source/Platform:

Field Investigation.

Source/Platform Mission Objectives:

To collect field sunphotometer data on the OTTER site.

Key Variables:

Not applicable.

Principles of Operation:

The sunphotometers are ten channel filter wheel instruments which are operated manually. They measure direct incoming solar radiation with 10 nm filter bandpasses centered at 370, 400, 440, 520, 610, 670, 780, 870, 940 and 1020 nm. The 940 nm channel was not calibrated, therefore this channel and it's values should not be used.

Sensor/Instrument Measurement Geometry:

Not applicable.

Manufacturer of Sensor/Instrument:

The sunphotometers that were used were manufactured by Dr. John Reagan at the University of Arizona.

Calibration:

Specifications:

The instruments were calibrated at Mt. Shasta on June 21 and June 22 using the Langley plot technique.

Tolerance:

Information not available.

Frequency of Calibration:

Information not available.

Other Calibration Information:

Details of the calibration procedure and processing of the sunphotometer data are found in Spanner et al., 1990, Journal of Spacecraft and Rockets, 27(4):373-379.

5. Data Acquistion Methods:

Sunphotometer data were acquired by remote sensing techniques at each OTTER site during the aircraft overflight periods in February, March, June, August and October of 1990 and in May and June of 1991.

6. Observations:

Data Notes:

Data collections listed in PLDS for the Metolius site were actually gathered at the Sisters airport. The latitude and longitude given for this site are from the airport.

Field Notes:

Information not available.

7. Data Description:

Spatial Characteristics:

Site 1: Cascade Head Latitude 44 03' N, Longitude 123 57' 30" W Site 1A: Cascade Head Alder Stand Latitude 44 03' N, Longitude 123 57' 30" W Site 2: Warings Woods Latitude 44 36' N, Longitude 123 16' W Site 3: Scio Control Latitude 44 40' 30" N, Longitude 123 36' 40" W Site 3F: Scio Fertilized Latitude 44 40' 30" N, Longitude 123 36' 40" W Site 4: Santiam Pass Latitude 44 025' 20" N, Longitude 121 50' 20" W Site 5: Metolius Control Latitude 44 25' N, Longitude 121 40' W Site 5: Metolius Fertilized Latitude 44 25' N, Longitude 123 40' W Site 6: Juniper Latitude 44 17' 30" N, Longitude 121 20' W

Spatial Coverage:

Information not available.

Spatial Coverage Map:

Information not available.

Spatial Resolution:

Information not available.

Projection:

Information not available.

Grid Description:

Information not available.

Temporal Characteristics:

Temporal Coverage:

22 February 1990 21 March 1990 18 June 1990 19 June 1990 20 June 1990 21 June 1990 25 June 1990 26 June 1990 13 August 1990 14 August 1990 15 August 1990 8 October 1990 22 May 1991 9 June 1991 10 June 1991

Temporal Coverage Map:

All six OTTER sites were covered by two sunphotometers once or twice each day.

Temporal Resolution:

Sunphotometer measurements were made approximately every 5 minutes for a minimum of 20 minutes. 1-2 minutes were required to acquire data in all ten channels.

Data Characteristics:

Parameter/Variable:

Total optical thickness.

Variable Description/Definition:

Optical thickness or depth related to the distance a frequency will travel within the atmosphere. It includes aerosol, ozone and Rayleigh optical thickness.

Unit of Measurement:

unitless

Data Source:

Field Investigation.

Data Range:

Rayleigh Optical Thickness 0.37000: Approximately .410 <--> .500 0.40000: Approximately .310 <--> .360 0.44000: Approximately .200 <--> .240 0.52000: Approximately .100 <--> .130 0.61000: Approximately .050 <--> .070 0.67000: Approximately .030 <--> .050 0.78000: Approximately .010 <--> .030 0.87000: Approximately .010 <--> .020 0.94000: Approximately .009 <--> .010 1.03000: Approximately .006 <--> .008

Net Optical Thickness 0.37000: Approximately .100 <--> 1.00 0.40000: Approximately .080 <--> .900 0.44000: Approximately .070 <--> .800 0.52000: Approximately .050 <--> .500 0.61000: Approximately .040 <--> .500 0.67000: Approximately .030 <--> .500 0.78000: Approximately .030 <--> .300 0.87000: Approximately .020 <--> .300 0.94000: Approximately .400 <--> 1.00 1.03000: Approximately .020 <--> .300

Sample Data Record:

Rayleigh Optical Thickness 0.37000: 0.44697 0.44697 0.44697 0.44697 0.44697 0.44697 0.44697 0.44697 0.40000: 0.32302 0.32302 0.32302 0.32302 0.32302 0.32302 0.32302 0.32302 0.44000: 0.21775 0.21775 0.21775 0.21775 0.21775 0.21775 0.21775 0.21775 0.52000: 0.10969 0.10969 0.10969 0.10969 0.10969 0.10969 0.10969 0.10969 0.61000: 0.05724 0.05724 0.05724 0.05724 0.05724 0.05724 0.05724 0.05724 0.67000: 0.03912 0.03912 0.03912 0.03912 0.03912 0.03912 0.03912 0.03912 0.78000: 0.02116 0.02116 0.02116 0.02116 0.02116 0.02116 0.02116 0.02116 0.87000: 0.01362 0.01362 0.01362 0.01362 0.01362 0.01362 0.01362 0.01362 0.94000: 0.00997 0.00997 0.00997 0.00997 0.00997 0.00997 0.00997 0.00997 1.03000: 0.00690 0.00690 0.00690 0.00690 0.00690 0.00690 0.00690 0.00690

Net Optical Thickness 0.37000: 0.46138 0.46505 0.47404 0.47458 0.47441 0.48239 0.47611 0.48324 0.40000: 0.35989 0.35631 0.36042 0.36327 0.36527 0.36520 0.35909 0.34856 0.44000: 0.33080 0.32907 0.33280 0.33925 0.34137 0.33809 0.33492 0.34490 0.52000: 0.26389 0.25838 0.26393 0.26704 0.26018 0.27189 0.26613 0.27299 0.61000: 0.19931 0.19703 0.19953 0.20121 0.20422 0.20369 0.20140 0.20562 0.67000: 0.15872 0.15676 0.15904 0.16067 0.16265 0.16303 0.16068 0.16145 0.78000: 0.10863 0.10845 0.11190 0.10987 0.11549 0.11199 0.11214 0.11365 0.87000: 0.09465 0.08950 0.09360 0.09263 0.09366 0.09411 0.09228 0.09325 0.94000: 0.71633 0.72502 0.72735 0.72974 0.73434 0.73590 0.73662 0.73921 1.03000: 0.05747 0.06121 0.06287 0.06338 0.06629 0.06659 0.06521 0.06723

8. Data Organization:

Data Granularity:

A total of 26 fields exist for each file in the data set. The first six fields give such data about the site as the date the measurements were taken, the site where the data was taken, the instrument used to record the data, the time at which the measurements were recorded, the solar angle, and the airmass. The next 10 fields give data about the Rayleigh optical thickness, and the last 10 fields give data about the net optical thickness.

Data Format:

There are six ASCII data sets: field_sunp.aug90, field_sunp.febmar90, field_sunp.jun90, field_sunp.jun91, field_sunp.may91, and field_sunp.oct90. Datasets 2, 4, 5, and 6 have an associated XY plot. In addition, a data set companion file is also available: fldsunp.doc and is included in the complete data set.

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

Information not available.

Data Processing Sequence:

Processing Steps:

The sunphotometer data provided to PLDS were processed using A10software developed by John Reagan's group at the University of Arizona. The format of the processed data was modified to conform to the Pilot Land Data System (PLDS). The following fields are associated with each data record which corresponds to a 1-2 minute measurement period for all ten channels of the sunphotometers.

Date: Date when sunphotometer data were acquired (ie 8/13/90).

Site: Site where sunphotometer data were acquired using the site numbers plus the PLDS site description code, (ie 1-CH, 2-WW, 3-SC, 4-SP, 5-ME, 6-JU).

Instrument: Instrument that made measurement (ie. Reagan1 or Reagan2).

Time: Pacific Standard Time for data acquired in February and March. Pacific Daylight Time for data acquired in June, August and October. Local time is given in the PLDS database as LOCAL DATE. Greenwich Mean Time (GMT) is also given.

Solar Angle: Solar elevation during acquisition period.

Airmass: Atmospheric airmass.

Rayleigh Optical Depths: For wavelengths at 370, 400, 440, 520, 610, 670,780, 870, 940 and 1030 nm. Calculated from atmospheric pressure and solar elevation.

Net Optical Depths: For wavelengths at 370, 400, 440, 520, 610, 670, 780, 870, 940 and 1030 nm. Net Optical Depth is equivalent to the aerosol optical depth. The Net Optical Depth is calculated from the total optical depth minus the Rayleigh optical depth, ozone optical depth and nitrogen dioxide optical depth. Ozone optical depth is calculated from the climatological tables of (Van Heuklon, 1979, Solar Energy, 22:63-68). Nitrogen Dioxide optical depths calculated from (Noxon, 1979, Journal of Geophysical Research, 84:5067-5076).

Processing Changes:

Information not available.

Calculations:

Calculation information is not available.

Graphs and Plots:

Not applicable.

10. Errors:

No information is available on the possible errors that were encountered during the field sun photometer measurements.

11. Notes:

Notes about the data are not available.

12. Application of the Data Set:

The field sunphotometer measurements are a key portion in the OTTER project goals. They give hard, physical data about the sites in the study. The combination of these remote sensing techniques with field work and laboratory study will help to simulate and predict ecosystem processes.

13. Future Modifications and Plans:

No future plans, the OTTER campaign is complete.

14. Software:

Software Description:

The public domain software package, Imdisp, is provided for image diplay on IBM compatibles. The popular shareware program, Stuffit, is necessary to extract the execution file for the Macintosh image display program, Image4pds.

Software Access:

Software to display most of the OTTER image data (except Aviris and Asas data) on Macintosh and IBM personal computers (and compatibles) is provided on the CD-Rom disc containing the data sets.

15. Data Access:

Contacts for Archive/Data Access Information:

Name: ORNL DAAC User Services Office

Address: ORNL DAAC User Services Office Oak Ridge National Laboratory U.S.A.

Telephone Number: 1-(865)-241-3952

Electronic Mail Address: ornldaac@ornl.gov

Data Center Identification:

ORNL DAAC

Procedures for Obtaining Data:

Contact the ORNL DAAC User Services Office Oak Ridge National Laboratory U.S.A.

Telephone: 1-(865)-241-3952 FAX: 1-(865)-574-4665 Internet: ornldaac@ornl.gov

Data Center Status/Plans:

To be determined.

16. Output Products and Availability:

Available via FTP file or on CD-ROM.

Also available on-line via the World Wide Web at http://daac.ornl.gov.

17. References:

Ozone optical depth is calculated from the climatological tables of (Van Heuklon, 1979, Solar Energy, 22:63-68). Nitrogen Dioxide optical depths calculated from (Noxon, 1979, Journal of Geophysical Research, 84:5067-5076).

18. Glossary of Terms:

Glossary terms can be found in the Glossary list.

19. List of Acronyms:

Additional acronyms can be found in the Acronyms list. AVIRIS Airborne Visible and Infrared Imaging Spectrometer ESD Environmental Sciences Division (Oak Ridge National Laboratory) FTP File Transfer Protocol GMT Greenwich Mean Time MAC Multi-sensor Aircraft Campaigns NASA National Aeronautics and Space Administration nm nanometers ORNL Oak Ridge National Laboratories Oak Ridge, Tennessee, U.S.A. OTTER Oregon Transect Ecosystem Research PLDS Pilot Land Data System TMS Thematic Mapper Simulator

20. Document Information:

30 July 1996 (data set citation revised on 19 November 2002)

Document Review Date:

30 July 1996

Document ID:

ORNL-OTTER-009

Citation:

Please cite this data set as follows (citation revised on 19 November 2002):

Spanner, M. 1994. Optical Thickness Data: Ground (OTTER). [Optical Thickness Data: Ground (Oregon Transect Ecosystem Research)]. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC), Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/65.

Curator:

DAAC Staff

Document URL:

http://daac.ornl.gov