NMC_SST.DOC
1. TITLE
1.1 Data Set Identification.
Sea surface temperature.
(Monthly ; NMC)
1.2 Data Base Table Name.
Not applicable.
1.3 CD-ROM File Name.
\DATA\SN_ICSST\NMC_SST\YyyMmm.SST
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: YyyMmm.sfx, where yy is the last
two digits of the year (e.g., Y87=1987), and mm is the month of the year
(e.g., M12=December). The filename extension (.sfx), identifies the
parameter in the file (i.e. SST=Sea Surface Temperature).
1.4 Revision Date Of This Document.
April 5, 1995.
2. INVESTIGATOR(S)
2.1 Investigator(s) Name And Title.
Dr. Richard W. Reynolds
Ms. Diane Stokes
National Meteorological Center
5200 Auth Road, Room 807
Camp Springs, MD 20746, USA
2.2 Title Of Investigation.
National Meteorological Center (NMC) global sea surface temperature
analyses.
2.3 Contacts (For Data Production Information).
_______________________________________________________________________
| Contact 1 | Contact 2 |
______________|___________________________|____________________________|
2.3.1 Name |Dr. Richard W. Reynolds |Ms. Diane Stokes |
2.3.2 Address |National Meteorological |National Meteorological |
| Center | Center |
|5200 Auth Road, Room 807 |5200 Auth Road, Room 807 |
City/St.|Camp Springs, MD |Camp Springs |
Zip Code|20746 |20746 |
2.3.3 Tel. |(301) 763-8396 |(301) 763-8396 |
2.3.4 Email | wd01rr@sgi11.wwb.noaa.gov |wd01dm@sgi26.wwb.noaa.gov |
| (internet) | (internet) |
______________|___________________________|____________________________|
2.4 Requested Form of Acknowledgment.
Please cite the following publication when these data are used:
Reynolds, R. W. and T. M. Smith, 1994. Improved global sea surface
temperature analyses. J. Climate, 7:929-948.
3. INTRODUCTION
3.1 Objective/Purpose.
Develop high resolution gridded Sea Surface Temperature (SST) fields
using in situ and satellite data.
3.2 Summary of Parameters.
Gridded monthly sea surface temperature.
3.3 Discussion.
The National Meteorological Center (NMC) global sea surface
temperature analyses use seven days of in situ (ship and buoy) and
satellite SST. These analyses are produced weekly using optimum
interpolation (OI) on a 1-degree grid. The OI technique requires
the specification of data and analysis error statistics. These
statistics show that the SST rms data errors from ships are almost
twice as large as the data errors from buoys or satellites. In
addition, the average e-folding spatial error scales have been
found to be 850 km in the zonal direction and 615 km in the
meridional direction.
The analysis also includes a preliminary step that corrects any satellite
biases relative to the in situ data using Poisson's equation. The
importance of this correction is demonstrated using recent data following
the 1991 eruptions of Mt. Pinatubo. The OI analysis has been computed
using the in situ and bias corrected satellite data for the period
November 1981 to present.
The monthly analyses presented here were computed by linearly
interpolating the weekly fields to produce daily fields and then
averaging the appropriate days within a month to produce monthly
averages.
4. THEORY OF MEASUREMENTS
There are two main sources of SST measurements: in situ and
satellite. The in situ observations are direct temperature
measurements made from ships (roughly 80%) and buoys. The ship
observations are primarily (roughly 70%) made by measuring the
temperature of water used for engine cooling. Almost all the
remaining ship measurements are obtained from thermometers placed
in insulated buckets which have been thrown overboard and filled
with sea water. The buoy observations are made by thermistors
which evaluate ocean temperature by either measuring the hull
temperature of the buoy or measuring the temperature of the water
directly. The depth of the measurement varies from roughly 20
meters (intake for engine cooling) to several meters (small
buoys).
The satellite observations are obtained by measuring the infrared
radiation using the Advanced Very High Resolution Radiometer
(AVHRR) on the U.S. National Oceanic and Atmospheric
Administration polar orbiting satellites. These data were
produced operationally by NOAA's Environmental Satellite, Data
and Information Service (NESDIS). The satellite retrieval
algorithms actually measure the temperature of the ocean using
several different infrared frequencies to eliminate the
interference caused by atmospheric water vapor. These algorithms
only work in cloud free areas. Because the algorithms only
measure a skin temperature (with depths on the order of
millimeters), the retrivevals are tuned against in situ
temperatures from drifting buoys. A discussion of these
algorithms can be found in:
McClain, E. P., W. G. Pichel, and C. C. Walton, 1985: Comparative
performance of AVHRR-based multichannel sea surface
temperatures. J. Geophys. Res., 90, 11587-11601.
Walton, C. C., 1988: Nonlinear multichannel algorithms for
estimating sea surface temperature with AVHRR satellite
data.
5. EQUIPMENT
5.1 Instrument Description.
Not available at this revision.
5.1.1 Platform (Satellite, Aircraft, Ground, Person...).
Not available at this revision.
5.1.2 Mission Objectives.
Not available at this revision.
5.1.3 Key Variables.
Not available at this revision.
5.1.4 Principles of Operation.
Not available at this revision.
5.1.5 Instrument Measurement Geometry .
Not available at this revision.
5.1.6 Manufacturer of Instrument.
Not available at this revision.
5.2 Calibration.
Not available at this revision.
5.2.1 Specifications.
Not available at this revision.
5.2.1.1 Tolerance.
Not available at this revision.
5.2.2 Frequency of Calibration.
Not available at this revision.
5.2.3 Other Calibration Information.
Not available at this revision.
6. PROCEDURE
6.1 Data Acquisition Methods.
For the data in this archive, the in situ data were obtained from a
preliminary version of the Comprehensive Ocean Atmosphere Data Set
(COADS) for the 1980s. These data consist of logbook and radio reports.
The satellite data were produced at the University of Miami's Rosenteil
School of Marine and Atmospheric Sciences from analyses of satellite
retrievals obtained from AVHRR. COADS data procedures are described in:
Slutz, R. J., S. J. Lubker, J. D. Hiscox, S. D. Woodruff, R. L.
Jenne, D. H. Joseph, P. M. Steurer, and J. D. Elms, 1985:
COADS: Comprehensive Ocean-Atmosphere Data Set. Release 1,
262 pp. [Available from Climate Research Program,
Environmental Research Laboratories, 325 Broadway, Boulder,
CO 80303.]
6.2.1 Spatial Coverage.
The coverage is global. Data in each file are ordered from North
to South and from West to East beginning at 180 degrees West and
90 degrees North. Point (1,1) represents the grid cell centered
at 89.5 N and 179.5 W (see section 8.4).
6.2.2 Spatial Resolution.
The data are given in an equal-angle lat/long grid that has a
spatial resolution of 1 X 1 degree lat/long.
6.3 Temporal Characteristics.
6.3.1 Temporal Coverage.
January 1987 through December 1988.
6.3.2 Temporal Resolution.
Monthly mean.
7. OBSERVATIONS
7.1 Field Notes.
Not applicable.
8. DATA DESCRIPTION
8.1 Table Definition With Comments.
Not applicable.
8.2 Type of Data.
--------------------------------------------------------------------------------
| 8.2.1 | | | |
|Parameter/Variable Name | | | |
--------------------------------------------------------------------------------
| | 8.2.2 | 8.2.3 | 8.2.4 | 8.2.5 |
| |Parameter/Variable Description |Range |Units |Source |
--------------------------------------------------------------------------------
|NMC_SST | | | |
| |NMC sea surface temperature in |min = 271.4, | [K] |NMC |
| |degrees Kelvin. |max = 308.2 | |analysis |
| | | | | |
--------------------------------------------------------------------------------
8.3 Sample Data Base Data Record.
Not applicable.
8.4 Data Format.
The CD-ROM file format is ASCII, and consists of numerical fields of
varying length, which are space delimited and arranged in columns and
rows. Each column contains 180 numerical values and each row contain 360
numerical values.
Grid arrangement
ARRAY(I,J)
I = 1 IS CENTERED AT 179.5W
I INCREASES EASTWARD BY 1 DEGREE
J = 1 IS CENTERED AT 89.5N
J INCREASES SOUTHWARD BY 1 DEGREE
90N - | - - - | - - - | - - - | - -
| (1,1) | (2,1) | (3,1) |
89N - | - - - | - - - | - - - | - -
| (1,2) | (2,2) | (3,2) |
88N - | - - - | - - - | - - - | - -
| (1,3) | (2,3) | (3,3) |
87N - | - - - | - - - | - - - |
180W 179W 178W 177W
ARRAY(360,180)
8.5 Related Data Sets.
Not available.
9. DATA MANIPULATIONS
9.1 Formulas.
9.1.1 Derivation Techniques/Algorithms.
The analysis technique consists of preliminary elimination of SST
data with bad position or bad SST values. All observations are
then averaged over onto a 1-degree weekly grid. These "super
observations" are then used in the analysis. The analysis
consists of two steps. First, the satellite super observations
are corrected for any large scale (1000 km) biases relative to
the in situ super observations. Finally, the in situ and corrected
satellite super observations are processed using optimum
interpolation to produce an analyzed SST field. A complete
description of all the data processing and analysis techniques
may be found in:
Reynolds, R. W. and T. M. Smith, 1994. Improved global sea surface
temperature analyses. J. Climate, 7:929-948.
9.2 Data Processing Sequence.
9.2.1 Processing Steps and Data Sets.
See reference in 9.1
9.2.2 Processing Changes.
Not available at this revision.
9.3 Calculations.
9.3.1 Special Corrections/Adjustments.
The NASA Goddard DAAC applied the inverse of the ISLSCP Initiative
1 land/sea mask to the SST data. Land values are 0.
The Goddard DAAC converted data values from centigrade to Kelvin.
9.4 Graphs and Plots.
Not available at this revision.
10. ERRORS
10.1 Sources of Error.
Errors in the final SST product are caused by errors in the
data and errors in the analysis method. Reynolds and Smith
(1994) determined that the rms errors from different types of
data were: ship, 1.5C; buoy, 0.8C; day satellite, 0.8C; and night
satellite, 0.5C.
To determine the analysis error, the SSTs from the OI were
compared with SSTs from three equatorial moored buoys located at
110W, 140W and 165E. The SST data from these buoys were not used
in the analysis. The monthly difference between buoys and the
analysis were computed for the period 1982-93. The rms
errors were: 0.38C at 110W, 0.39C at 140W and 0.24C at 165E. The
bias errors (buoy - analysis) were -0.21C at 110W; -0.26C at 140W
and -0.05C at 165E. The errors are larger in the eastern Pacific
because of the gradients and variability are larger than in the
west. Analysis rms errors less that 0.4C can be expected over
much of globe except in regions of the western boundary currents
(e.g., the Gulf Stream) where the rms errors can be 2 to 3 times
larger.
10.2 Quality Assessment.
10.2.1 Data Validation by Source.
Not available at this revision.
10.2.2 Confidence Level/Accuracy Judgment.
Not available at this revision.
10.2.3 Measurement Error for Parameters and Variables.
Not available at this revision.
10.2.4 Additional Quality Assessment Applied.
Not available at this revision.
11. NOTES
11.1 Known Problems With The Data.
Not available at this revision.
11.2 Usage Guidance.
Not available at this revision.
11.3 Other Relevant Information.
Not available at this revision.
12. REFERENCES
12.1 Satellite/Instrument/Data Processing Documentation.
Not available at this revision.
12.2 Journal Articles and Study Reports.
Reynolds, R. W., 1988. A real-time global sea surface temperature
analysis. J. Climate, 1:75-86.
Reynolds, R.W., 1993. Impact of Mount Pinatubo Aerosols on
Satellite-Derived Sea Surface Temperatures. Journal of
Climate, 6:768-774.
Reynolds, R. W., C. K. Folland and D. E. Parker, 1989. Biases in
satellite derived sea-surface-temperatures, Nature, 341:728-731.
Reynolds, R. W. and D. C. Marsico, 1993. An improved real-time global
sea surface temperature analysis. J. Climate, 6:114-119.
Reynolds, R. W. and T. M. Smith, 1994: Improved global sea surface
temperature analyses. J. Climate, 7:929-948.
12.3 Archive/DBMS Usage Documentation.
Contact the EOS Distributed Active Archive Center (DAAC) at NASA Goddard
Space Flight Center (GSFC), Greenbelt Maryland (see Section 13 below).
Documentation about using the archive or information about access to the
on-line information system is available through the GSFC DAAC User
Services Office.
13. DATA ACCESS
13.1 Contacts for Archive/Data Access Information.
GSFC DAAC User Services
NASA/Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Phone: (301) 286-3209
Fax: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.2 Archive Identification.
Goddard Distributed Active Archive Center
NASA Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Telephone: (301) 286-3209
FAX: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.3 Procedures for Obtaining Data.
Users may place requests by accessing the on-line system, by sending
letters, electronic mail, FAX, telephone, or personal visit.
Accessing the GSFC DAAC Online System:
The GSFC DAAC Information Management System (IMS) allows users to
ordering data sets stored on-line. The system is open to the public.
Access Instructions:
Node name: daac.gsfc.nasa.gov
Node number: 192.107.190.139
Login example: telnet daac.gsfc.nasa.gov
Username: daacims
password: gsfcdaac
You will be asked to register your name and address during your first
session.
Ordering CD-ROMs:
To order CD-ROMs (available through the Goddard DAAC) users should
contact the Goddard DAAC User Support Office (see section 13.2).
13.4 GSFC DAAC Status/Plans.
The ISLSCP Initiative I CD-ROM is available from the Goddard DAAC.
14. OUTPUT PRODUCTS AND AVAILABILITY
14.1 Tape Products.
Gridded data is available from NMC.
14.2 Film Products.
Not available at this revision.
14.3 Other Products.
Not available at this revision.
15. GLOSSARY OF ACRONYMS
AVHRR Advanced Very High Resolution Radiometer
CD-ROM Compact Disk (optical), Read Only Memory
DAAC Destributed Active Archive Center
EOS Earth Observation System
GSFC Global Change Data Center
NMC National Meteorological Center
OI optimum interpolation
SST sea surface temperature
COADS Comprehensive Ocean Atmosphere Data Set