Blaine L. Blad, Professor and Head
Elizabeth A. Walter-Shea, Asst. Professor
University of Nebraska
Measuring and Modeling Near-Surface Reflected and Emitted Radiation Fluxes at the FIFE Site.
Contact 1:
Cynthia J. Hays
Lincoln, NE
(402) 472-6701
Contact 2:
Mark A. Mesarch
Lincoln, NE
(402) 472-5904
agme012@unlvm.unl.edu
Contact 3:
Elizabeth A. Walter-Shea
Lincoln, NE
(402) 472-1553
agme012@unlvm.unl.edu
The Surface Reflectance Measured with a Mast-borne MMR data were collected by B.L. Blad, E.A. Walter-Shea, C.J. Hays, and M.A. Mesarch of the University of Nebraska. Their contribution of these data is particularly appreciated.
Light radiation striking a vegetative canopy interacts with individual phytoelements (leaves, stems, branches) and the underlying substrate. The interaction depends on light quality, radiative form (direct or diffuse), illumination incidence angle, vegetative component optical properties and canopy architecture. Radiation is reflected, transmitted or absorbed. Researchers have shown that phytoelements and substrates are not perfect Lambertian reflectors, i.e., they do not reflect equally in all directions (Breece and Holmes 1971; Walter-Shea et al., 1989; Brakke et al., 1989; Irons et al., 1989). The amount of leaf area and leaf angle distribution will determine the amount of vegetation and substrate that is sunlit and shaded. The amount of vegetative and substrate and respective amounts of sunlit and shaded components in a scene will vary depending upon the angle at which it is viewed, i.e., the canopy is itself a non-Lambertian surface. Thus, canopy, illumination and viewing geometry's are critical in determining the amount of reflected radiation received at the sensor. The measurements reported in the mast-borne MMR data set were predominantly made in the solar principal plane since the greatest variation in observed reflected radiation is expected to occur in that plane due to extremes in sunlit and shaded portions of the canopy (Norman and Walthall 1985).
Reflected radiation measurements were converted to radiances and reflectance factor. The reflectance factor is the ratio of the target reflected radiant flux to an ideal radiant flux reflected by an ideal Lambertian standard surface irradiated in exactly the same way as the target. Reflected radiation from a field reference panel corrected for non-perfect reflectance and sun angle was used as an estimate of the ideal Lambertian standard surface (Walter-Shea and Biehl 1990).
Thermal radiant energy (Rb) is composed of an emitted component (e * a * Ts**4) and a reflected component [(1 - e) ILW]:
where:
The Barnes Modular Multiband Radiometer (MMR) produces analog voltage responses to scene radiance in 8 spectral bands, and to the instrument chopper and detector temperatures. The 8 wavebands are approximately 0.45-0.52, 0.52-0.60, 0.63-0.69, 0.76-0.90, 1.15-1.30, 1.55-1.75, 2.08-2.35, and 10.4-12.5 um. Wavebands 1 - 4 have silicon detectors, wavebands 5 - 7 have lead sulfide detectors and waveband 8 has a Lithium Tantalum trioxide detector. The MMR's dimensions are 26.4 cm by 20.5 cm by 22.2 cm and weighs 6.4 kg.
In 1987 3 MMRs were used. The serial numbers and dates when they were used are:
In 1988 SN 108 was used.
In 1989 SN 114 was used.
Ground-based.
A portable, pointable mast.
Not applicable.
Surface radiances and reflectance factors in 8 wavebands (0.45-0.52, 0.52-0.60, 0.63-0.69, 0.76-0.90, 1.15-1.30, 1.55-1.75, 2.08-2.35 um), surface temperature in one waveband (10.4-12.5 um).
The MMR is a multi-sensor optical device operating in the visible, near infrared, middle infrared and thermal wavelengths. A mechanical chopper is used and the temperatures of the sensors and the chopper are monitored and stored with each 8-channel observation. Analog voltages from each sensor, detector thermistor, and chopper thermistor are converted to digital numbers and stored in the data logger. The MMR was mounted 3.4 m above the soil surface on a portable, pointable mast which allowed the MMR to view approximately the same surface area, regardless of the view zenith angle.
The MMR was mounted on a portable, pointable mast. The mast allowed the MMR to view approximately the same surface area, regardless of the view zenith angle. The MMR was located at 3.4 m above the soil surface with a 15 degree field-of-view and a spot size of approximately 0.75 m diameter at nadir. The filter characteristics of the MMR are described in the literature (Markham 1987).
Barnes Engineering Company
30 Commerce Road
Stamford, Connecticut 07904
(203) 348-5381
Not available at this revision.
The absolute error in calibration is estimated to be approximately 5% in wavebands 1-4 and approximately 10% in wavebands 5 - 7 (Sellers et al., 1990). The error in the thermal waveband is + or - 0.5 degrees Centigrade (Markham 1987).
Described above in the Calibration Section.
The MMR instruments used during FIFE showed good stability over the study period, changing a maximum of 5% between calibrations (Markham et al., 1988).
Changing the field-of-view changed the gains and offsets but did not change the temperature sensitivity coefficients.
1987 Calibration coefficients used for data reduction (Markham 1987):
SN 103
Waveband Gain Offset Temperature Temperature
Sensitivity Sensitivity
coefficient coefficient
in degrees in degrees
Centigrade Centrigrade
(IFC1-IFC3) (IFC-4)
_______________________________________________________
1 0.00696 -0.0028 597.0 590.0
2 0.00726 -0.0043 -1067.0 -1780.0
3 0.00738 -0.0066 -695.0 -732.0
4 0.01014 -0.0066 325.0 334.0
5 0.02207 0.0038 -64.7 -65.5
6 0.06377 0.0155 -62.1 -62.7
7 0.14616 -0.0105 -63.8 -63.8
Gains in [Volts][Watts^-1][m^-2][sr^-1][um^-1]
Offsets in Volts
Reference Temperature 25.8 degrees Centigrade.
There are no coefficients for the Thermal waveband because of malfunction.
SN 111
Waveband Gain Offset Temperature Temperature
Sensitivity Sensitivity
coefficient coefficient
in degrees in degrees
Centigrade Centigrade
(IFC1-IFC3) (IFC-4)
_______________________________________________________
1 0.00676 -0.0022 11170.0 11530.0
2 0.00711 -0.0048 1108.0 1040.0
3 0.00778 -0.0083 -778.0 -810.0
4 0.01045 -0.0083 421.0 430.0
5 0.02612 0.0089 -73.8 -76.2
6 0.04901 0.0002 -71.0 -71.7
7 0.14986 -0.0074 -71.0 -72.4
Gains in [Volts][Watts^-1][m^-1][sr^-1][um^-1]
Offsets in Volts
Reference Temperature 25.5 degrees Centigrade.
Thermal waveband 8 coefficients
AC = 0.16091
BC = 14.508
AA = -0.83334E-03
AB = -0.50983E-06
KA = 0.41768E-03
KB = 0.24520E-06
Where AC and BC are calibration coefficients for the equation used to calculate the calibration corrected temperature (Tc), and AA, AB, KA and KB are the calibration coefficients for the equation used to calculate the surface radiance (Ls). All of these coefficients are unitless.
SN 128
Waveband Gain Offset Temperature Temperature
Sensitivity Sensitivity
coefficient coefficient
in degrees in degrees
Centigrade Centigrade
(IFC1-IFC3) (IFC-4)
_______________________________________________________
1 0.00692 0.0012 6768.0 2758.0
2 0.00715 -0.0013 779.0 639.0
3 0.00748 -0.0037 -837.0 -1144.0
4 0.01004 -0.0057 465.0 415.0
5 0.02314 0.0055 -70.3 -71.5
6 0.05439 0.0105 -70.4 -71.9
7 0.14673 -0.0019 -67.1 -67.7
Gains in [Volts][Watts^-1][m^-2][sr^-1][um^-1]
Offsets in Volts
Reference Temperature 25.5 degrees Centigrade.
Thermal waveband 8 coefficients
AC = 0.15173
BC = 13.727
AA = -0.93338E-03
AB = -0.38504E-05
KA = 0.43947E-03
KB = 0.19048E-05
Where AC and BC are calibration coefficients for the equation used to calculate the calibration corrected temperature (Tc), and AA, AB, KA and KB are the calibration coefficients for the equation used to calculate the surface radiance (Ls). All of these coefficients are unitless.
See the Formulae Section for details on calibration equations.
1988 Calibration coefficients use for data reduction (Markham 1988):
SN 108
Waveband Gain Offset Temperature
Sensitivity
coefficient
in degrees
Centigrade
___________________________________________
1 0.00503 -0.0022 860.0
2 0.00607 -0.0026 3460.0
3 0.00694 -0.0056 -961.0
4 0.00978 -0.0067 269.0
5 0.01967 0.0037 -68.5
6 0.04201 0.0298 -72.0
7 0.07451 0.0027 -70.7
Gains in [Volts][Watts^-1][m^-2][sr^-1][um^-1]
Offsets in Volts
Reference Temperature 27.0 degrees Centigrade.
There are no coefficients for the Thermal waveband because of malfunction.
See the Formulae Section for details on calibration equations.
1989 Calibration coefficients used for data reduction (Markham 1989):
SN 114
Waveband Gain Offset Temperature
Sensitivity
coefficient
in degrees
Centigrade
________________________________________
1 0.00601 -0.0039 625.00
2 0.00689 -0.0039 1112.00
3 0.00712 -0.0042 -1486.00
4 0.01024 -0.0094 286.00
5 0.02048 0.0096 -74.40
6 0.04108 0.0322 -73.12
7 0.12229 0.0076 -70.24
Gains in [Volts][Watts^-1][m^-2][sr^-1][um^-1]
Offsets in Volts
Reference Temperature 28.5 degrees Centigrade.
Thermal waveband 8 coefficients AC = 0.1296
BC = 14.42
AA = -0.75249E-03
AB = -0.43519E-05
KA = 0.39019E-03
KB = 0.19078E-05
Where AC and BC are calibration coefficients for the equation used to calculate the calibration corrected temperature (Tc), and AA, AB, KA and KB are the calibration coefficients for the equation used to calculate the surface radiance (Ls). All of these coefficients are unitless.
See the Formulae Section for details on calibration equations.
In 1987 the MMR was mounted on a pointable, portable mast at a height of 3.4 m above the soil surface. The mast allowed the sensor to view the same surface area regardless of the viewing direction. A reference panel was positioned at a height of approximately 1 m above the soil surface. This panel was located within easy access to our plots and was measured to estimate the incoming radiation needed for data reduction. A measurement of the reference panel was made at the beginning of the measurement period. The mast was then positioned within the plot and aligned in the solar principal plane or the desired plane. Measurements were usually made at nadir and at 20, 35 and 50 degree view-zenith angles at each view-azimuth angle (occasionally 30 degrees was substituted for the 35 degree view-zenith angle). The angles were measured by an inclinometer mounted on the mast. The mast was then moved from plot to plot. After 20 to 25 minutes another measurement of the reference panel was made and the above procedure was repeated ending with a measurement of the reference panel. During IFC-1 in 1987 only one replication at each view zenith angle was recorded. Afterwards three replications were made (Blad et al., 1990).
In 1988 measurements were usually made in the solar principal plane and the view zenith angles were at nadir and 20, 35 and 50 degrees at each view azimuth angle. Three replications at each view zenith angle were recorded. Unless otherwise noted, the same procedure as in 1987 was followed.
In 1989 at sites 906 (SITEGRID_ID = 2133-MMR) and 916 (SITEGRID_ID = 4439-MMR) measurements were always made in the solar principal plane and the view-zenith angles were nadir and 20, 35 and 50 degrees at each view azimuth angle. Three replications at each view zenith angle were recorded. At site 966 (SITEGRID_ID = 2437-MMR) the measurements were made parallel to the aspect of the plot (i.e. north-south or east-west). In addition to the view-zenith angles measured at sites 906 (SITEGRID_ID = 2133-MMR) and 916 (SITEGRID_ID = 4439-MMR) a view zenith angle perpendicular to the slope of the plot was added at the appropriate view azimuth angle. The reference panel was measured periodically with the MMR mounted on the pointable mast, and at one minute intervals with a different MMR. The 1-minute data were primarily for the use of helicopter's radiometers but was also used as estimates of the incoming radiation for our data reduction on August 9 and 11. Unless otherwise noted, the same procedure as in 1987 and 1988 was followed.
All view-zenith angles were measured with respect to gravity not in relation to the slope of the plot.
Not available.
1987:
1988 (all data collected at Site 811(4439-PAM)):
1989:
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.
Measurements were made at the following twelve locations scattered throughout the FIFE study area. However, most sites were located in the northwest quadrant of the study area.
SITEGRID STN NORTHING EASTING LATITUDE LONGITUDE ELEV
-------- --- -------- ------- -------- --------- ----
0847-MMR 29 4332344 714439 39 06 57 -96 31 11 418
0939-MMR 170 4332200 712750 39 06 54 -96 32 22
1246-MMR 40 4331666 714212 39 06 35 -96 31 21 365
1445-MMR 42 4331160 714090 39 06 19 -96 31 27 400
2123-MMR 5 4329866 709506 39 05 41 -96 34 39 405
2133-MMR 906 4329726 711604 39 05 34 -96 33 12 443
2437-MMR 966 4329150 712375 39 05 15 -96 32 41
3129-MMR 8 4327702 710711 39 04 30 -96 33 51 430
4268-MMR 32 4325626 718579 39 03 15 -96 28 27 445
4439-MMR 18 4325218 712792 39 03 07 -96 32 28 445
4439-MMR 916 4325193 712773 39 03 06 -96 32 28 443
4439-MMR 811 4325219 712795 39 03 07 -96 32 27 445
6943-MMR 28 4320147 713500 39 00 22 -96 32 04 415
8739-MMR 26 4316699 712845 38 58 31 -96 32 35 442
SITEGRID SLOPE ASPECT
-------- ----- ------
0847-MMR 1 TOP
0939-MMR
1246-MMR
1445-MMR
2123-MMR 1 TOP
2133-MMR 1 TOP
2437-MMR
3129-MMR
4268-MMR
4439-MMR
4439-MMR 2 N
4439-MMR 2 N
6943-MMR
8739-MMR
In 1987 and 1988 measurement plots generally encircled the AMS station located at that site. In 1989 measurements plots were located northeast of the Wind Aligned Blob (WAB) site (Sellers et al., 1989). Topography files containing the northing and easting of the plots at each site, except for site 18 (SITEGRID_ID=4439-MMR) and 170 (SITEGRID_ID = 0939-MMR) in 1987 and site 966 (SITEGRID_ID = 2437-MMR) in 1989, are available in the GRABBAG section of FIFE CD-ROM Volume 1 in the UNL directory, in files UNL_PLOT.T87, UNL_PLOT.T88, UNL_PLOT.T89. These files also include the slope, aspect, soil depth, species and vegetative height of the plots.
Not available.
The footprint (surface area viewed by the MMR) had a diameter of 0.75 m at nadir and changed with view-zenith angle. The plot size was approximately 3 m x 3 m.
The overall coverage for these data is from June 3, 1987 through August 11, 1989. During this period there are 46 days of data. In 1987 there are 27 days of data during the growing season (June 3-October 13). Measurements in 1988 were made on seven days from May 24-August 11. Finally in 1989, measurements were made on twelve days from June 15-August 11.
Not available.
Not available.
The measurement time ranged from 1351 to 2200 GMT. Measurements were not continuously made over this range but were in discrete measurement periods depending on the number of plots in a site and coordination with aircraft and satellite overpasses.
In 1987 data were generally obtained at several sites during a day, hence a lot of time was spent moving and resetting equipment.
In 1988 data were obtained at site 811 (4439-MMR) only. A maximum of five (5) discrete measurement periods throughout the day was obtained.
In 1989 data were obtained at only one site per day. A maximum of five (5) discrete measurement periods throughout the day was obtained.
Not available.
The optimum time interval between plot measurements was approximately 5 minutes. The typical time interval between plots was approximately 10 minutes. The time interval depended on the distance between the plots, the terrain, and sky conditions.
The SQL definition for this table is found in the MMR_GRND.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. FIS Site grid codes (SSEE-III) give the south (SS) and east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument identifier.
STATION_ID The FIS site identifier used to min = 5, FIS designate this site. max = 966
OBS_DATE The date on which the data were min = 03-JUN-87, collected. max = 11-AUG-89
OBS_TIME The time that the observation was min = 1351, [GMT] taken. max = 2220
PLOT_NUM The plot number at the site where min = 1, FIS the data was collected. max = 999
SOLAR_ZEN_ANG The solar zenith angle, the min = 15.6, [degrees] vertical angle of the sun from max = 73.4 zenith. Zero degrees is straight up; 90 degrees is on the horizon.
SOLAR_AZIM_ANG The solar azimuth angle, the min = 84.2, [degrees horizontal angle of the sun from max = 269.3 from North] north.
VIEW_ZEN_ANG The view zenith angle, the angle min = 0, [degrees] from the surface normal (straight max = 50 up) to the observing instrument.
VIEW_AZIM_ANG The view azimuth angle, the min = 0, [degrees horizontal angle of the max = 360 from North] measurement from north.
BAND1_RADNC + The reflected radiance for band 1 min = .69, [Watts] (.45 - .52 microns) of the MMR. max = 347.51 [meter^-2] [ster^-1] [mic^-1]
BAND2_RADNC + The reflected radiance for band 2 min = 7.41, [Watts] (.51 - .60 microns) of the MMR. max = 334 [meter^-2] [ster^-1] [mic^-1]
BAND3_RADNC + The reflected radiance for band 3 min = 6.49, [Watts] (.63 - .68 microns) of the MMR. max = 300.11 [meter^-2] [ster^-1] [mic^-1]
BAND4_RADNC + The reflected radiance for band 4 min = 11.6, [Watts] (.75 - .88 microns) of the MMR. max = 202.6 [meter^-2] [ster^-1] [mic^-1]
BAND5_RADNC + The reflected radiance for band 5 min = 6.74, [Watts] (1.17 - 1.33 microns) of the MMR. max = 64.75 [meter^-2] [ster^-1] [mic^-1]
BAND6_RADNC + The reflected radiance for band 6 min = 2.19, [Watts] (1.57 - 1.80 microns) of the MMR. max = 24.54 [meter^-2] [ster^-1] [mic^-1]
BAND7_RADNC + The reflected radiance for band 7 min = .082, [Watts] (2.08 - 2.37 microns) of the MMR. max = 17.971 [meter^-2] [ster^-1] [mic^-1]
BAND8_RADNC + The reflected radiance for band 8 [Watts] (10.4 - 12.3 microns) of the MMR. [meter^-2] [ster^-1] [mic^-1]
RADIANT_TEMP The radiant temperature of the min = 11.35, [degrees site. max = 99.9 Celsius]
CHOPPER_TEMP The radiometer chopper temperature. min = 14.43, [degrees max = 99.9 Celsius]
DETECTOR_VOLTAGE The voltage reading of the min = 10.62, [Volts] detector. max = 37.91
BAND1_REFL The reflectance for band 1 (.45 - min = .26, [percent] .52 microns) of the MMR. max = 95.85
BAND2_REFL The reflectance for band 2 (.51 - min = 2.8, [percent] .60 microns) of the MMR. max = 96.66
BAND3_REFL The reflectance for band 3 (.63 - min = 2.4, [percent] .68 microns) of the MMR. max = 95.87
BAND4_REFL The reflectance for band 4 (.75 - min = 6.85, [percent] .88 microns) of the MMR. max = 91.25
BAND5_REFL The reflectance for band 5 (1.17 min = 12.49, [percent] - 1.33 microns) of the MMR. max = 80.33
BAND6_REFL The reflectance for band 6 (1.57 min = 7.43, [percent] - 1.80 microns) of the MMR. max = 64.44
BAND7_REFL The reflectance for band 7 (2.08 min = .44, [percent] - 2.37 microns) of the MMR. max = 96.87
DATASET_ID An identification code for this min = UNL154, group of data to link it to max = UNL89223 other information in the inventory table.
FIFE_DATA_CRTFCN_CODE * The FIFE Certification Code for CPI = checked the data, in the following format: by principal CPI (Certified by PI), CPI-??? investigator (CPI - questionable data).
LAST_REVISION_DATE data, in the format (DD-MMM-YY). max = 05-AUG-91
Footnotes:
+ mic = micrometers
* 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 is "merged" from two separate receiving stations to eliminate transmission errors. CPI-??? Investigator thinks data item may be questionable.
SITEGRID_ID STATION_ID OBS_DATE OBS_TIME PLOT_NUM SOLAR_ZEN_ANG
----------- ---------- ---------- -------- -------- -------------
4439-MMR 18 07-AUG-87 1754 5 23.9000
4439-MMR 18 07-AUG-87 1754 5 23.9000
4439-MMR 18 07-AUG-87 1754 5 23.9000
4439-MMR 18 07-AUG-87 1754 5 23.9000
SOLAR_AZIM_ANG VIEW_ZEN_ANG VIEW_AZIM_ANG BAND1_RADNC BAND2_RADNC
-------------- ------------ ------------- ----------- -----------
160.6000 50.0000 160.0000 31.440 55.290
160.6000 50.0000 160.0000 31.290 55.290
160.6000 35.0000 160.0000 30.830 53.100
160.6000 35.0000 160.0000 30.670 53.100
BAND3_RADNC BAND4_RADNC BAND5_RADNC BAND6_RADNC BAND7_RADNC
----------- ----------- ----------- ----------- -----------
45.360 118.940 49.400 15.750 3.073
45.500 119.130 49.510 15.830 3.098
45.360 112.330 47.680 15.700 3.235
45.230 111.940 47.250 15.400 3.125
BAND8_RADNC RADIANT_TEMP CHOPPER_TEMP DETECTOR_VOLTAGE BAND1_REFL
----------- ------------ ------------ ---------------- ----------
99.9000 99.9000 32.0100 8.010
99.9000 99.9000 32.0100 7.980
99.9000 99.9000 32.0200 7.860
99.9000 99.9000 32.0200 7.820
BAND2_REFL BAND3_REFL BAND4_REFL BAND5_REFL BAND6_REFL BAND7_REFL
---------- ---------- ---------- ---------- ---------- ----------
13.200 12.240 46.630 50.210 33.510 16.110
13.200 12.270 46.700 50.320 33.670 16.240
12.680 12.240 44.030 48.460 33.400 16.960
12.680 12.200 43.880 48.020 32.760 16.380
DATASET_ID FIFE_DATA_CRTFCN_CODE LAST_REVISION_DATE
---------------- --------------------- ------------------
UNL219 CPI 30-JAN-89
UNL219 CPI 30-JAN-89
UNL219 CPI 30-JAN-89
UNL219 CPI 30-JAN-89
The overall coverage for these data is from June 3, 1987 through August 11, 1989. During this period there are 46 days of data. The plot size was approximately 3 m x 3 m.
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.
WAVEBAND'S 1-7 FORMULAE
where:
where:
where:
where:
where:
WAVEBAND 8 (THERMAL) FORMULAE
where:
where:
where:
where:
where:
where:
SURFACE TEMPERATURE FORMULA
where:
REFERENCE PANEL CORRECTIONS
In 1987 two pressed barium sulfate reference panels were used (NEB1 and NEB2). NEB1 was used for the first IFC and NEB2 was used for the last three IFC's. The panels were calibrated in July, 1987 by Dr. Ray D. Jackson at the U.S. Water Conservation Laboratory in Phoenix, Arizona. The method of Jackson et al., (1987) was used.
In 1988 and 1989 a Lapsphere molded halon reference panel was used. This panel was calibrated in September 1989 by the University of Nebraska following the procedure of Jackson et al., (1987).
The calibration yields the coefficients to a third order polynomial of the form:
where:
The result of this equation RFp(j) is used in equation [5].
Panel coefficients
1987:
NEB1
Waveband C0 C1 C2 C3
1 97.45057 5.584734E-02 -3.959692E-03 9.882025E-06
2 97.54819 5.666440E-02 -3.940689E-03 9.039184E-06
3 97.83009 2.959063E-02 -3.426001E-03 6.630198E-06
4 97.99712 1.562715E-02 -2.707314E-03 1.116180E-06
5 96.42652 -2.559037E-02 -9.758750E-04 -9.890963E-06
6 93.98231 2.807484E-02 -1.788550E-03 -2.213021E-06
7 88.83311 7.468207E-02 -2.506758E-03 3.913525E-06
1987:
NEB2
Waveband C0 C1 C2 C3
1 102.40660 -7.996049E-02 5.068796E-04 -3.423062E-05
2 102.23610 -8.242803E-02 1.107736E-03 -4.046916E-05
3 102.87460 -1.375718E-01 2.305963E-03 -4.769363E-05
4 102.78210 -1.352304E-01 2.514470E-03 -4.980858E-05
5 101.74110 -2.097449E-01 4.728492E-03 -6.302641E-05
6 98.79391 -1.605808E-01 3.859259E-03 -5.455406E-05
7 92.51772 -1.235733E-01 3.302859E-03 -4.998493E-05
1988 and 1989:
Halon
Waveband C0 C1 C2 C3
1 105.79300 0.9812652E-01 -0.5175089E-02 0.1390845E-04
2 106.73860 0.8086680E-02 -0.2866652E-02 -0.3902893E-05
3 106.30450 0.4490710E-01 -0.3717498E-02 0.1859340E-05
4 105.94070 0.7618627E-01 -0.4686755E-02 0.9638660E-05
5 104.80800 0.8175281E-01 -0.3934094E-02 0.2798061E-05
6 103.11720 0.6749086E-01 -0.2412556E-02 -0.8442320E-05
7 101.17420 0.1416389E-00 -0.4732779E-02 0.6610390E-05
SURFACE TEMPERATURE CALCULATIONS
The surface temperature was calculated using the calibration corrected temperature measurement, incoming longwave radiation (ILW) and surface emissivity values (Eq. 12).
Values for incoming longwave radiation were calculated for each MMR data record.
where:The equation is valid for clear daytime conditions (Deacon 1970). These values were averaged over the measurement period at a specific site. The values are in the data set described in the Longwave Radiation UNL data document found on FIFE CD-ROM Volume 1.
Surface emissivity measurements were made under completely overcast sky conditions or at night and not in conjunction with the MMR measurements. An Everest model 112C IRT measured the temperature of the surface (Tu) and the temperature of the surface covered by an aluminum tent (Ta). The incoming longwave radiation under these conditions was determined using an IRT temperature measurement of an aluminum plate (T) of known emissivity (ep) and a thermocouple temperature of the plate (Tp).
The incoming longwave at the time of the surface emissivity measurement was calculated as:
where:
SN 680 a=1.175373885 (C) b=0.980765782 (unitless)
SN 680 was calibrated and adjusted pre-season so no calibration coefficients were applied.
Emissivity measurements were made over a sampling of plots at a specific site during each IFC period in 1987. The emissivity is calculated as:
where:
Emissivity values were averaged per site per IFC for calculation of true surface temperatures. The following is a listing of the emissivity values used in 1987.
Emissivity measurements were made over a sampling of plots at site 811(4439-MMR) close to days of MMR measurements in 1988. The measurements were averaged per site for the specific days listed. The following is a listing of the emissivity values used in 1988.
Emissivity measurements were made over a sampling of plots at Sites 906(2133-MMR), 916(4439-MMR), and 966(2437-MMR) close to days of MMR measurements in 1989. The values were averaged per site for specific days for the canopy and bare soil. The following are the emissivity values used in 1989:
Wavebands 1 - 7 Processing Steps
Equation 1 is used to correct the MMR wavebands for the detectors' thermal sensitivity. This equation adjusts the MMR voltage to that which would occur at a reference temperature (Td,0). The temperature sensitivity coefficient and reference temperature for each MMR is listed in the Other Calibration Information Section. Equation 2 is then used to change the corrected voltages to radiances. The gains and offsets for each MMR are listed in the Other Calibration Information Section(Markham 1987). Usage of Equations 3 and 4 is dependent on the measurement interval of the reference panel. These equations interpolate the reference panel radiance output for the time of surface reflectance measurements. If measurements of the reference panel are made less then every 30 minutes but not every minute, Equation 3 is then applied (Bauer et al., 1981). If the measurements of the reference panel are greater then 30 minutes apart then Equation 4 is used. If the reference panel was measured every minute Equations 3 and 4 can be omitted. The reference panel Reflectance Factor for each surface measurement time is determined as explained in the Derivation Techniques and Algorithms Section. This provides a correction for the reference panel's non-Lambertian properties and the dependence on the solar zenith angle. Equation 5 is then used to calculate the surface reflectance factor using surface and reference panel radiances and the reference panel reflectance factor.
Waveband 8 (thermal) processing Steps
If the chopper thermistor is functioning Equations 6 and 7 are used to calculate the chopper temperature and radiance. Then Equation 9 is used to calculate a surface radiance. If the chopper thermistor is malfunctioning then Equation 8 is used to calculate the detector radiance and Equation 10 is used to calculate a surface radiance. Equation 11 is then used to convert the surface radiance to a calibration corrected temperature measurement (Markham 1987).
The calibration corrected temperature measurement, incoming longwave radiation and surface emissivity values are used to calculate surface temperature using Equation 12 (Blad et al., 1976).
Not applicable.
Not applicable.
None.
Errors associated with the measurements can occur due to orientation of the MMR. The view-zenith angle could only be measured to +/- 2 degrees Centigrade and the view-azimuth angle could only be measured to +/- 10 degrees Centigrade.
The shadowing caused by the MMR and the mast in measuring the "hot spot" area is another source of error.
Variable cloud cover could be an error source with reflectance factors since the incoming radiation measurements were not made simultaneously with the surface measurements.
Comparisons have been made with Surface Reflectance Measured by the PARABOLA, helicopter mounted radiometers (MMR, SE590, Surface Radiant Temperatures) and SE590 measurements (Ground and Leaf).
On days with variable cloud conditions the data should be used with caution. The AMS incoming solar radiation data at the site or nearby site should be consulted.
On clear days the measurements fall within the precision of the instrument and errors that were discussed in previous sections.
Not available at this revision.
FIS staff applied a general QA procedure to the 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. Inconsistencies and problems found in the QA check are described is 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.
For 1987 the following data are erroneous for Waveband 7:
Channel 7 occasionally malfunctioned. Other problems were with the surface and chopper temperatures. A value of 99.9 was assigned to erroneous data. During IFC's 3 and 4 the detector for waveband 8 (thermal) on SN 103 was malfunctioning so there are no surface temperatures. During IFC's 1 and 2 the chopper detector on SN 128 was malfunctioning.
In 1988 all of the surface temperature values are assigned a value of 99.9 because the detector for waveband 8 in SN 108 was malfunctioning.
In 1989 there are no known problems.
Before using reflectance factors the incoming radiation from the AMS station at the site or nearby site should be checked for possible cloud-induced error in reflectance factors.
Always check plot numbers before constructing a site average. Plot 999 is an artificially created and maintained bare soil plot.
One day when Ghassem Asrar was handling FIFE Operations, he called on the radio and told Blaine Blad and Don Deering that he was sending the helicopter up and for them to start taking measurements. Both Blaine and Don answered that it was too cloudy and that he shouldn't send the helicopter. Ghassem replied that it was clear since Erwin had forecast clear skies. The moral of this story is that one should always look out the window before commenting on sky conditions.
This data set can be utilized to characterize bi-directional reflectance factor distributions in the solar principal plane for a tall grass prairie; estimate surface albedo from bi-directional reflectance factor and radiance data; determine the variability of reflected and emitted fluxes in selected spectral wavebands as a function of topography, vegetative community and management practice; determine the influence of plant water status on surface reflectance factors; and determine sun angle effects on radiation fluxes.
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 Surface Reflectance Measured with a Mast-borne MMR data are available on FIFE CD-ROM Volume 1. The CD- ROM filename is as follows:
DATA\SUR_REFL\MMR_GRND\GRIDxxxx\Yyyyy\ydddgrid.MRG.
Where xxxx is the four digit code for the location within the FIFE site grid, yyyy are the four digits of the century and year (e.g., Y1987 = 1987). 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 filenames is: ydddgrid.sfx, where grid is the four-number code for the location within the FIFE site grid, 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 .MRG for this data set.
Barnes Engineering. 1982. Calibration and data book: Multispectral 8- channel radiometer. Barnes Engineering Company. Stamford, CT.
Markham, B.L. 1987. Memo on review of Phoenix calibration of MMR Channel 8. GSFC/NASA, Greenbelt, MD 20771.
Markham, B.L. 1987. FIFE MMR Calibration Report. GSFC/NASA, Greenbelt, MD 20771.
Robinson, B.F., M.E. Bauer, D.P. DeWitt, L.F. Silva and V.C. Vanderbilt. 1979. Multiband radiometer for field research. Measurements of Optical Radiation. Proceedings of the Society of Photo-Optical Instrumentation Engineers. 196:8-15.
Robinson, B.F., and L.L. Biehl. 1979. Calibration procedures for measurement of reflectance factor in remote sensing field research. Measurements of Optical Radiation. Proceedings of the Society of Photo-Optical Instrumentation Engineers. 196:16-26.
Bauer, M.E., B.F. Robinson, C. Daughtry, and L.L. Biehl. 1981. Field Measurement Workshop. Oct. 14-16, Laboratory for application of Remote Sensing. Purdue University. Lafayette, Indiana.
Blad, B.L. and N.J. Rosenberg. 1976. Measurement of crop temperature by leaf thermocouple, infrared thermometry and remotely sensed thermal imagery. Agronomy Journal. 68:635-641.
Blad, B.L., E.A. Walter Shea, C.J. Hays, and M.A. Mesarch. 1990. Calibration of field reference panel and radiometers used in FIFE 1989. AgMet Progress Report 90-3. Department of Agricultural Meteorology. University of Nebraska-Lincoln. Lincoln, Nebraska. 68583-0728.
Blad, B.L., E.A. Walter Shea, P.J. Starks, R.C. Vining, C.J. Hays, and M.A. Mesarch. 1990. Measuring and modeling near-surface reflected and emitted radiation fluxes at the FIFE site. AgMet Progress Report 90-1. Department of Agricultural Meteorology. University of Nebraska- Lincoln. Lincoln, Nebraska. 68583-0728.
Breece, H.T. III and R.A. Holmes. 1971. Bi-directional scattering characteristics of healthy green soybean and corn leaves in vivo. Applied Optics. 10:119-127.
Deacon, E.L. 1970. The derivation of Swinbank's long-wave radiation formula. Quarterly Journal of the Royal Meteorological Society. 96:313-319.
Irons, J.R., R.A. Weismiller, and G.W. Peterson. 1989. Soil reflectance In G. Asrar (ed.). Theory and Applications of Optical Remote Sensing. John Wiley & Sons. New York. p.66-106.
Jackson, R.D., D.A. Dusek, and E.E. Ezra. 1983. Calibration of the thermal channel on four Barnes model 12-1000 multi-modular radiometers. United States Water Conservation Laboratory Report 12. Phoenix, Arizona.
Jackson, R.D., S.M. Moran, P.N. Slater, and S.F. Biggar. 1987. Field calibration of reference reflectance panels. Remote Sensing of Environment. 17:103-108.
Markham, B.L., F.M. Wood, and S.P. Ahmad. 1988. Radiometric calibration of the reflective bands of NS001 Thematic Mapper Simulator (TMS) and Modular Multispectral Radiometers (MMR). Society of Photo-Optical Instrumentation Engineers Recent Advances in Sensors, Radiometers, and Data Processing for Remote Sensing. 924:96- 108.
Markham, B.L. 1988. personal communication. GSFC/NASA, Greenbelt, MD 20771.
Markham, B.L. 1989. MMR Calibration data for FIFE 89 and related studies. GSFC/NASA, Greenbelt, MD 20771.
Norman, J.M. and C.L. Walthall. 1985. Analysis of an empirical model for hemispherical albedo computation. Final Report for Contract #S- 19583-D.
Sellers, P.J. and F.G. Hall. 1989. FIFE-89 Experiment Plan. GSFC/NASA, Greenbelt, MD 20771.
Sellers, P.J., F.G. Hall, D.E. Strebel, R.D. Kelly, S.B. Verma, B.L. Markham, B.L. Blad, D.S. Schimel, J.R. Wang, and E. Kanemasu. 1990. FIFE Interim Report. GSFC/NASA, Greenbelt, MD 20771.
Walter-Shea, E.A. and L.L. Biehl. 1990. Measuring vegetation spectral properties. Remote Sensing Review. 5:179-205.
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 27, 1994 (citation revised on October 16, 2002).
This document has been reviewed by the FIFE Information Scientist to eliminate technical and editorial inaccuracies. Previous version 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.
August 8, 1996.
ORNL- FIFE_MMR_GRND.
Blad, B. L., and E. A. Walter-Shea. 1994. MMR Ground Data (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/52. 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).