There are no author-identified significant results in this report

Anding, D. C.

Walker, J. P.

English

NASA Technical Reports Server

JRB-75-201-AA
E 7.5- 1 0. 1. 4 6
USE OF SKYLAB EREP DATA IN A
SEA SURFACE TEMPERATURE EXPERIMENT
Interim Report
, David C. Anding ud WSl
Ih P "MIade avaitable under E -John P. Walker
iz In the int!er~e c e'r!~
semination of Ea.., R,:e ,rc's Survey
Program inform3tion : ,;l i ou, iiabitity
ior any use made therect."
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4 u ScienBe Applications, Incorporated
H 94 u Ann Arbor, Michigan 48103
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04 0 ~Prepared for
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-, A National Aeronautics and Space Administration
>rd Johnson Space Center
L .O W Houston, Texas 77058
P Q)
Su u oContract NAS9-13277
< l March 1975
J suiumuuuhs
https://ntrs.nasa.gov/search.jsp?R=19750009690 2020-03-22T23:03:21+00:00Z
JRB-75-201-AA
USE OF SKYLAB EREP DATA IN A
SEA SURFACE TEMPERATURE EXPERIMENT
Interim Report
David C. Anding
John P. Walker
Science Applications, Incorporated
Ann Arbor, Michigan 48103
Prepared for
National Aeronautics and Space Administration
Johnson Space Center
Houston, Texas 77058
Contract NAS9-13277
March 1975
FOREWORD
The research described herein, which was conducted by JRB
Associates - a wholly owned subsidiary of Science Applications, Inc-
orporated, was performed under NASA Contract NAS9-13277. This
interim report covers the period from 1 September 1974 to 28 February
1975.
ii
ABSTRACT
This report discusses the status of an experiment to utilize S191
spectrometer data acquired over ocean areas to access the ability of
spaceborne infrared multispectral sensing to function as a means of
providing improved estimates of sea-surface temperature over that
obtainable with a single channel radiometric instrument. All data pro-
ducts from SL-2, -3 and -4 and all support data have been received
and critiqued, and a plan for data analysis has been established. The
details and rationale for the data analysis plan are presented. Also
presented are preliminary results for two test sites.
iii
Use of Skylab EREP Data in a
Sea Surface Temperature Experiment
INTRODUCTION
NASA is planning to launch an ocean observation satellite in the near
future (Nimbus G) which will contain a two-channel infrared radiometric
instrument capable of measuring the sea surface temperature to an accuracy
of , 1 Kelvin. The initial design of the instrument has been postulated but
the spectral response of each of the two channels has not been finalized. It
is expected that the results of EREP will influence the spectral response
selection. An experiment of particular relevance consists of acquiring
S191 infrared spectrometer data (- 6 to . 15 psm) over ocean areas for
which the atmospheric and sea surface conditions and temperatures are
known. The measured data will be compared with theoretical predictions
and postulated radiometric techniques for measuring sea surface tempera-
tures will be tested. The results are expected to provide an important in-
put to the final selection of the spectral response of each of the two radio-
metric channels. The status of this experiment is described herein.
EXPERIMENT SUMMARY AND DATA
The candidate test sites scheduled for analysis are given in Table 1.
In a previous report (see quarterly report dated September 1974) two
additional test sites were scheduled for analysis (i. e., SL-3 pass 16 and
SL-3 pass 43). These were for coastal stratus test sites and have been
eliminated from consideration because of data problems (see quarterly re-
port dated September 1974 for further justification). For each test site the
time, location, support data, and EREP data products received are noted.
The present plan for analysis (and the status thereof) of the data for each
test site is as follows:
1
Table 1.
Test Site Data Products
LATITUDE-.
PASS DESCRIPTION GMT LONGITUDE GROUND TRUTH NOAA SATELLITE DATA COMMENTS
MISSION: SL-2 START: 18:03:05 START: 28N, 95W AIRBORNE PRT-5 SEA-SURFACE NONE AVAILABLE 4 4 NADIR SCAN.
PASS: 5 END: 18:03:35 END: 27N, 94W TEMPERATURE. AIRCRAFT- SCATTERED CUMULUS.
DAY: 156 BORNE AIR TEMPERATURE AND LWIR RADIANCE DATA NOT
DATE: 5 June 73 DEW POINT DEPRESSION. AVAILABLE.
MISSION: SL-2 START: 15:21:44 START: 26N, 89W AIRBORNE PRT-5 SEA-SURFACE ITOS (12991) VHRR VISIBLE/ 1 4 4 7 NADIR SCAN.
PASS: 8 END: 15:23:03 END: 23N, 85W TEMPERATURE. AIRCRAFT- IR MAPS. ITOS (#2991) SR. SCATTERED CUMULUS.
DAY: 162 BORNE AIR TEMPERATURE AND
DATE: 11 June 73 DEW POINT DEPRESSION.
MISSION: SL-3 START: 17:08:20 TARGET BUCKET TEMPERATURE. NO NONE AVAILABLE 1 1 TRACKED TARGET.
PASS: 36 END: 17:09:33 LOCATION: AIR OR RADIOMETRIC SURFACE VERY HAZY.
DAY: 255 37N, 76W TRUTH.
DATE: 12 Sept. 73
MISSION: SL-3 START: 15:06:54 TARGET BUCKET TEMPERATURE. NO ITOS (#4219) VHRR VISIBLE/ 4 7 7 7 TRACKED TARGET.
PASS: 46 END: 15:07:00 LOCATION: AIR OR RADIOMETRIC SURFACE IR.MAPS. ITOS (14219) SR SCATTERED CUMULUS
DAY: 260 37N, 76W TRUTH. AND VTPR
DATE: 17 Sept. 73
MISSION: SL-4 START: 16:29:03 START: 19N, 86W AIRBORNE PRT-5 SEA-SURFACE ITOS (115633) VHRR VISIBLE/ 4 1 4 4 TRACKED TARGET. DAC
PASS: 78 END: 16:31:47 END: 27N, 79W TEMPERATURE. IR MAPS. ITOS (115633) SR NOT TURNED ON SO GIMBAL
DAY: 8 TARGET BUCKET TEMPERATURE. AND VTPR ANGLES DURING DATA TAKE
DATE: 8 Jan. 74 LOCATION: RADIOSONDE. PERIOD ARE UNKNOWN: TARGET
UNKNOWN LOCATION NOT DETERMINABLE.
MISSION: SL-4 START: 15:50:23 TARGET NO GROUND OR AIR TRUTH ITOS VHRR VISIBLE/IR MAPS 7 4 * I TRACKED TARGET.
PASS: 79 END: 15:52:59 LOCATION: AVAILABLE
DAY: 9 32.5N, 66.3W
DATE: 9 Jan.74 * NO POST AUTOCAL
MISSION: SL-4 START: 20:10:25 TARGET AIRBORNE PRT-5 SEA-SURFACE ITOS (!/5802) VHRR VISIBLE 7 I 4 1 TRACKED TARGET. FIELD-OF-
PASS: " 87 END: 20:13:19 LOCATION: TEMPERATURE. MAP. ITOS (!!5802) VHRR IR, VIEW APPEARED GREENISH-
DAY: 21 24.5N, 82.4W BUCKET TEMPERATURE. SR, AND VTPR BLUE INDICATING BOTTOM
DATE: 21 Jan. 74 REFLECTIONS.
MISSION: SL-2
PASS: 5
DAY: 156
DATE: 5 June 73
The long wavelength detector temperatures were high during EREP
passes 1 through 5 and valid long wavelength responsivities could not be
calculated. Consequently, LWIR radiance data are not available for this
pass. Therefore, these data cannot be analyzed.
MISSION: SL-2
PASS: 8
DAY: 162
DATE: 11 June 73
The data for this EREP pass is quite comprehensive; surface and air
truth plus NOAA satellite support data. The major uncertainty, as in-
dicated by the data acquisition camera (DAC), is possible contamination of
the S191 field-of-view by clouds. The processing and analysis plan is to
check the instrument calibration and correct the data for responsivity drift
errors if necessary. Subsequently predictions and measurement results
will be compared. Errors larger than measurement and calibrational un-
certainties will be attributed to clouds and the corresponding data will be
rejected. This analysis is planned for the next quarter.
MISSION: SL-3
PASS: 36
DAY: 255
DATE: 12 Sept 73
The data for this pass have marginal utility because the surface and
air truth data are minimal. No air or radiometric surface truth are avail-
able, only bucket temperatures. Also, no satellite data are available. Air
3
truth data may be obtainable from local weather stations, but would likely
not be coordinated closely in time. Because of time and funding limitations
these data will not be processed initially, pending the results of data analysis
for other more promising missions.
MISSION: SL-3
PASS: 46
DAY: 260
DATE: 17 Sept 73
These data are similar in potential utility as those for pass 36. Ground
truth data consists of bucket temperatures only. The data have a further
problem in that the field-of-view was probably contaminated by clouds (as
indicated by the DAC). As for pass 36, these data will not be processed
initially, pending the results of other analyses.
MISSION: SL-4
PASS: 78
DAY: 8
DATE: 8 Jan 74
The data for this pass, by design, are the most comprehensive of all
EREP passes. The ground and air truth data consists of radiometric sur-
face temperatures, bucket temperatures, and radiosonde data. Additional
support data include ITOS D-G scanning radiometric data and temperature
and humidity profiles from the VTPR. A comprehensive analysis of these
data should provide more information relative to the satisfaction of experi-
mental objectives than any other EREP pass. The effort will basically in-
clude examining the data for responsivity drift errors and correcting them
if necessary, and then comparing measurement results with analytical pre-
dictions. The first stages of this analysis have been completed and the re-
sults are given in the Data Analysis Section.
4
MISSION: SL-4
PASS: 79
DAY: 09
DATE: 9 Jan 74
The data for this mission were acquired by tracking a water surface
area near Bermuda. The area was totally cloud free and from the DAC
appeared to occur at a time of high visibility. Unfortunately no ground
or air truth data are available for the test site area. Consequently, these
data appear to have little utility in satisfying experimental objectives and
will, therefore, not be analyzed further.
MISSION: SL-4
PASS: 87
DAY: 21
DATE: 21 Jan 74
As for the data for EREP pass 78, these data are fairly comprehen-
sive. The ground truth consists of both PRT-5 radiometric temperatures
and bucket temperatures. Although no radiosonde data are available tem-
perature and humidity data are available from the vertical temperature
profile radiometer (VTPR) aboard ITOS. The analysis plan is to check for
responsivity drift errors and make corresponding corrections to the data if
necessary. Subsequently, analytical predictions and measurement data will
be compared and interpreted. Analysis of these data has not yet begun.
DATA ANALYSIS
The main thrust of the analysis to be performed for this study is verifi-
cation of existing analytical radiative transfer models. The verification
procedure will involve inputting measured values of sea-surface tempera-
ture, air temperature and humidity into atmospheric radiance models and
5
calculating the spectral radiance one would expect at the entrance apera-
ture of the S191 spectrometer. These calculated radiances will then be
compared with measured values and any discrepancies resolved. Calculated
and measured radiances are compared for the Monroe Reservoir, Salem,
Illinois (EREP data acquisition on 6 June 1973) in Figure 1. Observe that
the general agreement is good, and probably within experimental and an-
alytical predictive uncertainties, with the exception of the spectral region
from approximately 8 to 11 im. Here the predicted values are consistently
higher than measured values. This difference may be caused by measure-
ment error, improper treatments in the predictive model, or both. Since
such discrepancies can have a significant impact upon spaceborne earth-
surface observations, a major remaining task will be to determine if such
differences are consistently observed for other test sights and, if so, to
identify the basis for such differences.
The Florida Keys test site, EREP pass 78 (data acquisition on 8 January
1974), has been the major subject of analysis thus far because of the compre-
hensive nature of the support data, which provides for a more definitive
analysis. The support data include:
1) PRT-5 sea-surface temperatures acquired at an altitude of 1500 feet.
2) Bucket temperatures.
3) Radiosonde data giving temperature and humidity data to the 300 mb
pressure level.
4) ITOS Vertical Temperature Profile Radiometer (VTPR) data giving
temperature and humidity data to the 400 mb pressure level.
5) ITOS Very High Resolution Radiometer (VHRR) data giving upwelling
radiance at 0.5 km spatial resolution between 10.5 and 12.5 pm.
The initial step in the analysis was to check for responsivity drift
errors. This was achieved by computing the average spectral radiance
6
1000
800
S600
S400 -Measured
Theoretical------
200
0 I I .1 I I I I I I I
5 6 7 8 9 10 11 12 13 14 15 16
WAVELENGTH ( m)
Figure 1. Comparison of Measured and Predicted Spectral Radiance for the Monroe Reservoir,
Salem, Illinois, on 6 June 1973. Water Surface Temperature = 298 K.
for 30 sequential scans of the ambient calibration source and comparing
the results with a blackbody radiance spectrum evaluated at the temperature
of the ambient calibration source, as determined from the housekeeping
data. The result is shown in Figure 2. The calibration source temperature
at the time of the post autocal sequence was determined to be 291.67 Kelvins.
The best fit blackbody curve for the post autocal radiance was determined to
be 290.81 Kelvins, 0.86 degrees less. The lapsed time between the pre-pass
calibration and the post-pass autocal was 1 hour and 30 minutes and data
acquisition occurred 30 minutes after pre-pass calibration. Assuming the
total difference is caused by a linear responsivity drift, the correction re-
quired is only approximately 0.3 Kelvins. In the context of the present ex-
periment this is a negligible amount.
The next step in the analysis was to prepare the support data for cal-
culation of the radiance at the entrance aperture of the S191. The radio-
sonde and VTPR data were processed and analyzed and a representative
model atmosphere was constructed. The temperature and humidity pro-
files are shown in Figures 3 and 4, respectively. The actual radiosonde
and VTPR data are given in Tables 2 and 3, respectively. The PRT-5
radiometric sea-surface temperatures and the bucket temperatures were
obtained by NOAA and are shown in Figure 5. The difference between
radiometric and bucket temperatures is not known at the present time.
The remaining step in the analysis is to use the model atmosphere
data, and the sea-surface temperature data, and calculate the spectral
radiance at the entrance aperture of the S191 for comparison with mea-
sured data. This effort is currently in progress.
FUTURE PLANS
The planned effort for the remaining quarter is primarily to perform
a comprehensive analysis on the data from EREP passes 78 and 87, and
8
1000
800
+
* 600
4I +
+
Z 400
Autocal Radiance Data +++++
Ambient Blackbody Radiance -200
5.0 7.0 9.0 11.0 13.0 15. 0
WAVELENGTH (um)
Figure 2. Comparison of Autocal Radiance Data with Ambient Blackbody Radiance for a
Blackbody Temperature of 291.67 Kelvins.
10
-D
100
a-
1000180 200 220 240 260 280 300 320
TEMPERATURE (K)
Figure 3. Atmospheric Temperature for Key West on 8 Jan 74.
10
65
4
3
2
11
0 0. 1 1.0 10..0
WATER VAPOR CONCENTRATION (PR. CM/KM)
Figure 4. Water Vapor Concentration for Key West on 8 Jan 74.
Table 2.
Radiosonde Data for Key West on 8 Jan 74
Latitude = 24.6N Longitude = 81.7W
H(m) P(mb) T(K) R.H. (o)
0.0 1021.0 298.0 .79.0
83.2 1011.0 294.8 82.0
175.4 1000.0 296.2 85.0
1035.9 902.0 290.3 86.0
1342.8 869.0 289.1 63.0
1523.8 850.0 288.3 64.0
1935.9 808.0 286.0 66.0
2026.4 799.0 285.4 34.0
2138.2 788.0 284.4 72.0
2282.4 774.0 283.1 66.0
2641.5 740.0 281.5 72.0
2837.0 722.0 281.7 30.0
3081.5 700.0 281.0 31.0
3413.5 671.0 278.4 55.0
3781.5 640.0 276.5 42.0
4014.3 621.0 276.3 22.0
5216.6 530.0 266.9 21.0
5649.8 500.0 263.8 13.0
6104.6 470.0 255.8 10.0
7553.6 384.0 248.3 14.0
9250.4 300.0 234.1 14.0
10453.8 250.0 224.3 0.0
11159.3 224.0 222.9 0.0
11510.6 212.0 224.3 0.0
11882.5 200.0 222.9 0.0
13719.2 150.0 210.6 0.0
16309.7 100.0 196.1 0.0
18590.3 70.0 197.5 0.0
18966.6 66.0 198.0 0.0
19470.7 61.0 201.7 0.0
19793.3 58.0 200.5 0.0
20250.7 54.0 205.6 0.0
20744.2 50.0 205.4 0.0
21421.8 45.0 208.5 0.0
21714.9 43.0 215.1 0.0
24050.5 30.0 222.0 0.0
25791.3 23.0 226.9 0,0
26712.9 20.0 225.8 0.0
27789.6 17.0 225.2 0.0
28192.6 16.0 225.0 0.0
29326.3 13.5 229.3 0.0
12
Table .3.
VTPR Data for Key West on 8 Jan 74
Latitude = 23.98N Longitude = 80.78W
P(mb) T air (K) T (K) P 0 (mb)air dew H2
1000 298.12 294. 87 25. 96
850 288.35 285.37 14.21
700 279.06 271.77 5. 51
500 262.62 252. 79 1. 21
400 250. 90 240. 58 0. 40
300 236.07 - -
250 227.39 - -
200 219.79 - -
150 212.73 - -
100 207.04 - -
70 199.43 - -
50 206. 10
30 217. 36
20 222. 16
10 229. 47
13
36.0 -il. x I0 - 3
F-
9. x 10-3
p (45*) at 546 nm
\ (45 ° ) at 436nm 5.x10 3
- --- , -3. x 10-3
26 -I.x10
Bucket Temperature25"
24'
2Rodiometric Temperature23'
22° C isotherm
r 200-a--
400- t
4 24039.1 N 23033.2' N
81"08.1' W 8i'55.5' W
Figure 5. Sea Temperature Data from NOAA for Key West on
8 Jan 74.
14
analyze the data for other missions as time and funds permit. Passes 78
and 87 are the only passes for which; 1) the support data were of adequate
scope and reliability to perform a definitive analysis, and 2) did not have
possible field-of-view contamination by scattered cumulus. It is felt that
the results of this effort will satisfy the experimental objectives to the ex-
tent possible from available EREP S191 data.
15


Use of Skylab EREP data in a sea surface temperature experiment

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