Efforts continue under this contract to develop algorithms for the computation of sea surface temperature (SST) from MODIS infrared retrievals. This effort includes radiative transfer modeling, comparison of in situ and satellite observations, development and evaluation of processing and networking methodologies for algorithm computation and data accession, evaluation of surface validation approaches for IR radiances, and participation in MODIS (project) related activities. Efforts in this contract period have focused on radiative transfer modeling, evaluation of atmospheric correction methodologies, involvement in field studies, production and evaluation of new computer networking strategies, and objective analysis approaches

Brown, Otis B.

English

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NASA-CR-200204
/AJ-+
TECHNICAL REPORT O
Contract Title: Infrared Algorithm Development for Ocean Observations
with EOS/MODIS
Contract: NAS5-31361
Type of Report: Semi-annual
Time Period: July-December 1995
Principal Investigator: Otis B. Brown
RSMAS/MPO
University of Miami
4600 Rickenbacker Causeway
Miami, Florida 33149-1098
INFRARED ALGORITHM DEVELOPMENT FOR OCEAN OBSERVATIONS
WITH EOS/MODIS
Abstract
Efforts continue under this contract to develop algorithms for the computation of sea
surface temperature (SST) from MODIS infrared retrievals. This effort includes radiative transfer
modeling, comparison of in situ and satellite observations, development and evaluation of
processing and networking methodologies for algorithm computation and data accession,
evaluation of surface validation approaches for IR radiances, and participation in MODIS (project)
related activities. Efforts in this contract period have focused on radiative transfer modeling,
evaluation of atmospheric correction methodologies, involvement in field studies, production and
evaluation of new computer networking strategies, and objective analysis approaches.
MODIS INFRARED ALGORITHM DEVELOPMENT
A. Near Term Objectives
A.I. Continue algorithmic development efforts based on experimental match-up databases and
radiative transfer models.
A.2. Continue interaction with the MODIS Instrument Team through meetings and electronic
communications.
A.3 Continue evaluation of different approaches for global SST data assimilation and work on
statistically based objective analysis approaches.
A.4 Continue evaluation of high-speed network interconnection technologies.
A.5 Continue evaluation of various in situ validation approaches for the MODIS IR bands.
A.6 Provide investigator and staff support for the preceding items.
(NASA-CR-200204) INFRARED N96-18743
ALGORITHM DEVELOPMENT FOR OCEAN
OBSERVATIONS Semiannual Report,
Jul. - Dec. 1995 (Miami Univ.) Unclas
7 P
G3M3 0100337
https://ntrs.nasa.gov/search.jsp?R=19960012506 2020-06-16T04:43:58+00:00Z
B. Overview of Current Progress
B.I July-December 1995
Activities during the past six months have continued on the previously initiated tasks.
There have been specific continuing efforts in the areas of (a) radiative transfer modeling, (b)
generation of model based retrieval algorithms, (c) continued work on IR calibration/validation as
part of the MODIS Ocean Science Team cruise effort, and (e) work on test and evaluation of an
experimental wide area network based on ATM technology. Previously initiated activities such as
team related activities are ongoing.
Special foci during this six month period have been:
1) completion of the first draft of the MODIS Oceans Infrared Validation Plan,
2) laying the foundations for a DOE/NOAA/NASA ARM joint cruise in the Tropical
Western Pacific in the spring of 1996,
3) exploring the potential sources of radiosondes to compile a global marine data set that
correctly represents the distributions of conditions in the atmosphere,
4) initiating a study of the probability distribution of near-surface diurnal gradients in the
global ocean, and,
5) writing the SST sections of the EOS Science Plan (and have been submitted to Dr.
Rothrock for inclusion in the draft document).
In early November Dr. R. Sikorski joined the team in a post doctoral position. He is currently
working on the compilation of a marine radiosonde database and will do some of the radiative
transfer simulations.
B. 1.1 Radiative Transfer Modeling
Initial work is underway to examine correction approaches based on fast-forward codes
and those based on EOF decompositions of atmospheric profiles with exact forward calculated
coefficients. It is currently unclear whether computer capability will permit implementation of the
fast, forward RTE-based correction approach for routine atmospheric correction of MODIS
retrievals.
The RAL radiation transfer code is being rewritten to extend its spectral coverage to
include the MODIS infrared channels, to improve its performance on Digital "Alpha" machines,
and to permit it to provide profiles of channel radiance through the atmosphere. Discussions have
continued between P. Minnett and A. Zavody concerning enhancements to the RTE radiative
transfer simulation code. Zavody has agreed to furnish up-to-date spectral data to permit the
simulation's use over the complete MODIS-IR band set, but as yet this has not been completed.
B. 1.2 Algorithm Development Efforts Based on Experimental Match-up Data bases
The main objective of our recent work is to explore the associations between atmospheric
water vapor content and various AVHRR-derived quantities. Insight gained on the nature of these
associations will allow us to better understand the performance of existing SST algorithms, as well
as to improve the parameterization of various terms in such algorithms. The difference in
brightness temperatures in AVHRR channels 4 and 5 is the quantity most often used as a proxy for
atmospheric effects. Therefore, during this period we have dedicated considerable attention to
exploring the association between this quantity and water vapor, including the effects of AVHRR
viewing geometry, geographic location, and season
Simultaneously, studies were conducted to improve "clearing" of potentially contaminated
retrievals from imagery and the comparison database. It was found that the database was
contaminated by a number of "OC" values from the NOAA TAO buoys (they use "OC" to denote a
missing observation).
The distribution of buoy positions in the satellite-buoy comparison data base is strongly
biased away from high latitudes, having hardly any values north of 50° N. Polar and sub-polar
regions represent an extreme in the atmospheric conditions, and it is known that atmospheric
correction algorithms optimized for global conditions perform less well here than at mid-latitudes.
This is suspected to be because, even though the low water-vapor burden of the high-latitude
atmospheres makes them more transmissive, the spectral gradient in the 10-12 \im window
becomes increasingly the result of that of the surface emissivity and less of that of the atmospheric
water vapor effects. To study this using the AVHRR retrieval and drifting-buoy temperature data
base, it is necessary to increase the population of high-latitude samples. The NATO SACLANT
Undersea Research Centre in La Spezia, Italy, has conducted research in the Nordic (Greenland,
Icelandic and Norwegian Seas) for many years and has deployed more than one hundred drifting
buoys in that area. Data from this drifting buoy program were made available by Dr. P.M.
Poulain, and the trajectories of the buoys are shown in Figure 1. After quality control, nearly
150,000 records of buoy position and surface temperature are now awaiting to be merged with the
corresponding AVHRR data and be incorporated into the database of AVHRR-buoy comparisons.
These buoy data are also being incorporated into the WOCE Surface Velocity Program (SVP)
database by the NOAA Atlantic Oceanographic and Meteorological Laboratory.
Nordic Seas Drifter tracks.
Figure 1. Trajectories of the buoys deployed by the NATO SCALANT Undersea Research Centre
in the Nordic Seas. The period covered is mid-1991 to 1994.
Latitude-time diagrams of zonal averages of the differences between AVHRR and
Reynolds' composite SST fields for the years 1990-1993 have revealed some intriguing
differences. Discrepancies fall in the range of ±1.5K with extreme positive values appearing at
high latitudes in the summer season, with the northern hemisphere being more effected, and with a
coherent seasonal migration between the hemispheres. A secondary band of extreme positive
values is found in the tropics. It is hypothesized that these are caused by either diurnal gradients in
the near-surface layers, or by residual atmospheric water vapor contamination.
B.I.3 Wide Area Networking
A network between heterogeneous machines, switches and adapters (FORE, SGI and
DEC) has been implemented and is in use in a production environment. This configuration
routinely carries 40-60 Gigabytes of traffic per day. Tasks include disk-to-disk, disk-to-tape and
tape-to-disk transfers.
B. 1.4 In Situ Calibration/Validation of MODIS IR Radiances
An offer for joint work with DOE and NOAA investigators has been accepted to make
measurements using a prototype M-AERI (Marine-Atmospheric Emitted Radiance Interferometer;
Revercombe et al., 1993; Smith et al., 1996) on a research cruise of the NOAA R/V Discoverer in
the Tropical Western Pacific from mid-March to mid-April 1996. The cruise, called the Combined
Sensor Cruise, brings together an unprecedented selection of sensors to characterize the marine
atmosphere. This cruise is in a region of extreme sea and atmospheric conditions. In addition to
providing measurements for the validation of the atmospheric corrections used with existing
satellite infrared radiometers (AVHRR, ATSR, GMS), this cruise will enable us to test strategies
and tactics for the validation of MODIS infrared measurements and SST retrievals. It also facilitates
measurement of the sea-surface emissivity at the extreme of environmental conditions. The
dependence of sea-surface emissivity on external parameters (especially wind speed; e.g. Masuda
et al., 1988) will be measured, and the cruise will provide data with which to study the diurnal
thermocline and the skin effect. It also provides us with the opportunity to test a prototype M-
AERI at sea before the contractual delivery date, so that potential difficulties can be identified and
corrected. Funding to participate in the cruise has been secured from the DOE ARM (Atmospheric
Radiation Measurements) Program, and additional funding to enhance the instrument suite with an
all-sky camera and broad-band infrared radiometric thermometer to characterize the cloud fields and
to support extra data analysis has been requested from NASA. Equipment used during the Pelican
cruise (please refer to previous reports; Smith et al., 1996) is currently being refurbished for this
cruise.
B.I.5. Diurnal thermocline study
A study of the global probability distribution has begun using monthly-averaged U.S.
Navy 'climatology' of the surface parameters, and monthly ERBE surface insolation fields. The
spatial resolution of the data used in this study is 1°. The winds, given as means and standard
deviations, have been recast into the shape and scale factors of the Weibull distribution, and this
allows the calculation of probabilities of winds being above or below given values. The ERBE
measurements have been interpolated to match the wind fields resolution. SST, air temperatures
and surface humidities will be extracted from the Navy climatology, and other parameters that are
necessary to drive a diurnal thermocline model (e.g. Price et al., 1986) will be calculated. Results
from this study will assist in the interpretation of the discrepancies between in situ and satellite
derived SSTs, and guide strategy formulation for the validation of MODIS SSTs.
B.I.6 MODISIR Validation Plan
The first version of the MODIS-Infrared Sea Surface Temperature Algorithm, Science Data
Validation Plan has been written and submitted. A copy can be obtained using the World Wide
Web on URL http://www.rsmas.miami.edu: 80/modis/ in both/w andpdf formats. The document
discusses the need for, and requirements of, an extensive validation strategy to ensure confidence
in the MODIS infrared measurements and derived sea-surface temperature fields. The approach
recommended includes validation of top-of-the-atmosphere radiances, surface radiances and
surface temperatures, using a variety of methods, instruments and platforms. These include
radiometers or other satellites, high-flying and low-flying aircraft, ships and research platforms.
Both highly-focused, intensive measurement campaigns to study the physical processes at the
ocean surface and in the atmosphere that influence the MODIS measurements, and long-term
global-scale monitoring of the MODIS data will be required. Synergism and collaboration will be
sought with groups involved in the validation of MODIS ocean color and atmospheric properties
derived from EOS instruments.
The Validation Plan will be revised when appropriate to take into account new and relevant
findings, and to document new collaborative opportunities that are pertinent to the MODIS AM-1
infrared validation activities.
C. Investigator Support
July
August
Sept.
J. Brown
V. HalliweU
A. Li
D.Li
P. Minnett
W. Baringer V. HalliweU
J. Brown A. Li
P. Evans D. Li
G. Goni P. Minnett
W. Baringer G. Goni
J. Brown A. Li
P. Evans D. Li
Oct.
Nov.
Dec.
J. Brown
G. Goni
W. Baringer
O. Brown
P. Evans
W. Baringer
P. Evans
A. Li
D.Li
V. Halliwell
A. Li
V. HalliweU
A. Li
D. Future Activities
D.I Current:
D.I.I Algorithms
a. Continue to develop and test algorithms on global retrievals
b. Evaluation of global data assimilation statistics for SST fields
c. Continue radiative transfer modeling using RAL code
d. Participate in Combined Sensor Cruise, and analyze data
e. Continue to study near-surface temperature gradients
f. ATBD updates (as needed)
g. Validation Plan updates (as needed)
h. EOS Science Plan updates (as needed)
i. Define and implement an extended ATM based network test bed
j. Evaluate and analyze results of calibration/validation experiment
k. Continued integration of new workstations into algorithm development environment
D.I.2 Investigator support
Continue current efforts
E. Problems
No new problems to report.
F. Publications
None to report.
G. References:
Masuda, K., T. Takashima, Y. Takayama, 1988:
Emissivity of Pure and Sea Waters for the Model Sea Surface in the Infrared Window
Regions. Remote Sensing of the Environment, 24, 313-329.
Price, J.F, R.A. Weller and R. Pinkel, 1986:
Diurnal cycling: observations and models of the upper ocean response to diurnal heating,
cooling and wind mixing. J. Geophys. Research, 91, 8411-8427.
Revercomb, H.E., F.A. Best, R.G. Dedecker, T.P. Dirkx, R.A. Herbsleb, R.O. Knuteson, J.F.
Short, and W.L. Smith, 1993:
Atmospheric Emitted Radiance Interferometer for ARM. Symposium on Global Change
Studies. January 17-22, 1993, Preprint.
Smith, W. L., R.O. Knuteson, H.E. Revercomb, W. Feltz, H.B. Howell, W.P. Menzel,
N. Nalli, O.B. Brown, J. Brown, P. Minnett and W. McKeown, 1996:
Observations of the Infrared Radiative Properties of the Ocean-Implications for the
Measurement of Sea Surface Temperature via Satellite Remote Sensing. Bull. Amer.
Meteor. Soc., (In the press).


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