JPL Product #001
Data is permanently staged on the FTP site ftp podaac.jpl.nasa.gov in the subdirectory: pub/data_collections/monthly_mean_atlas.
TOPEX/POSEIDON sea surface height, 1993-1999
TOPEX/POSEIDON significant wave height, 1998-1999
SSM/I surface wind speed, 1987-1999
AVHRR sea surface temperature, 1987-1999
TMI sea surface temperature, 1998-1999
ERS-1 surface wind velocity, 1992-1996
ERS-2 surface wind velocity, 1996-1999
NSCAT surface wind velocity, 1997
SeaWiFS Chlorophyll-a concentration, 1998-1999
ARGOS buoy drift of near-surface current, 1989-1992.
"Since about ten years ago, substantial advances in remote and in situ techniques to record temperature, sea level, horizontal current and surface wind have helped oceanographers define annual cycles and interannual variations. Innovative ideas of how the ocean and atmosphere are coupled together occurred in parallel with new instrumentation. Three examples are El Nino Southern Oscillation (Philander, 1989), the ocean-atmosphere flux of carbon (Oeschger, 1988), and the relationship between global sea surface temperature and precipitation over Africa (Palmer, 1986). Monthly mean distributions of geophysical variables, which cover the globe or a large- scale region like an ocean basin, are becoming de rigueur." (This material is taken directly from Halpern at al., 1994)
"Although both satellite- and ground-based recording systems provide essential information for global change studies, satellite-borne instrumentation yields unprecedented spatial and temporal coverage of the global ocean. This data product contains monthly mean distributions of satellite measurements of surface wind speed, sea surface temperature, and sea surface height variation from 1987 - 1993." (This material is taken directly from Halpern at al., 1994)
The data product displays observations from different satellites, operated by various agencies. "Very little averaging or interpolation of the data was made to retain the fundamental sampling characteristics of each data set. Deficiencies of current remote sensing systems are easily seen in maps of data sampling density, which should be especially interesting to developers of new and innovative satellite-borne instrumentation." (This material is taken directly from Halpern at al., 1994)
Descriptions of all data sets and color images of all monthly mean (and annual mean) global distributions of each data set are published by Halpern at al. in a series of annual hard-copy atlases. The atlases also contain images of ECMWF surface wind components, a data set which is not available from the JPL DAAC other than as hard-copy. Atlases also contain color images of analysis undertaken using the data sets that comprise this product.
AVHRR monthly global MCSST coregistered with CZCS data (Miami, GSFC) CD-ROM, JPL DAAC Product #015
AVHRR weekly global 18km global MCSST (Miami), JPL DAAC Product #016
AVHRR Oceans Pathfinder global equal-angle all SST (NOAA, NASA), JPL DAAC Product #050
AVHRR Oceans Pathfinder global equal-angle best SST (NOAA, NASA), JPL DAAC Product #051
AVHRR Oceans Pathfinder global equal-angle 0.5-degree resolution global SST (NOAA, NASA), JPL DAAC Product #053
TOPEX/Poseidon altimeter merged geophysical data record (NASA/PO.DAAC), JPL DAAC Product #028
DMSP F-8 SSM/I ocean wind speed, liquid water, water vapor '87-'91 (Wentz), JPL DAAC Product #033
DMSP F-10 SSM/I ocean wind speed, liquid water, water vapor '90-'92 (Wentz), JPL DAAC Product #034
SSM/I Pathfinder ocean wind speed level 2 and browse data (NOAA, NASA, MSFC, Wentz), JPL DAAC Product #054
SSM/I Pathfinder gridded ocean wind speed level 3 (NOAA, NASA, MSFC, Wentz), JPL DAAC Product #057
TOPEX/POSEIDON sea surface height:
Sea surface height is calculated from the round-trip travel time of the
radar altimeter pulse between the sea-surface and the satellite. "The
TOPEX/POSEIDON sea surface data set used in this report is based on the
Geophysical Data Record (GDR) that was described by Callahan (1994).
The technique is complex to convert a radar altimeter's travel time
measurement between the satellite and the sea surface into an accurate
estimate of the elevation of the sea surface relative to a reference
ellipsoid, which becomes the oceanographic signal of interest. Numerous
algorithms are involved." (Halpern at al., 1995)
TOPEX/POSEIDON significant wave height:
SSM/I surface wind speed:
Over water surfaces the geophysical retrieval algorithm developed by
Remote Sensing Systems (Wentz, 1989) for finding wind speed (W), water
vapor content (V), and cloud/rain liquid water content (L) uses the 22
and 37 GHz vertically polarized, and 37 GHz horizontally polarized
SSM/I channels. The algorithm fits a radiative transfer model
parameterized in terms of W, V, and L, to the 22 and 37 GHz
observations (Wentz et al.,1986). The model accounts for absorption and
scattering in the atmosphere and emissivity of wind-roughened sea
surface. The model does not account for Mie scattering by rain drops or
scattering by frozen hydrometers. For rain rates above 1.5 mm/hr the
model may no longer be valid due to radiative scattering.
AVHRR sea surface temperature:
The history of SST computation from AVHRR radiances is discussed at
length by (McClain et al., 1985). Briefly, radiative transfer theory is
used to correct for the effects of the atmosphere on the observations
by utilizing "windows" of the electromagnetic spectrum where little or
no atmospheric absorption occurs. Channel radiances are transformed
(through the use of the Planck function) to units of temperature, then
compared to a-priori temperatures measured at the surface. This
comparison yields coefficients which, when applied to the global AVHRR
data, give estimates of surface temperature which have been nominally
accurate to 0.3 degrees C.
TMI sea surface temperature:
The TRMM microwave imager (TMI) measures electromagnetic
radiation emitted at the sea surface at 10.7, 19.4, 21.3, 37
and 85 GHz. TMI represents the first satellite capable of
accurately recording SST in the presence of clouds.
ERS-1 and ERS-2 surface wind velocity:
"At moderate incidence angles typical of the ERS-1 measurement swath,
sigma-naught varies both with wind speed and relative azimuth angle
between the incident radiation and wind direction. Calculation of
vector winds from colocated sigma-naught measurements requires a
"model function" relating sigma-naught to wind velocity for given radar
viewing geometry, a "wind retrieval" algorithm that yields a set of
possible wind velocity solutions consistent with the sigma-naught
measurements, and an "ambiguity removal" algorithm that allows
selection of a unique wind velocity from among the (up to four)
possible solutions determined at each location by the wind retrieval
algorithm (Naderi et al., 1991)." (This material is taken directly from
Halpern et al., 1995)
SeaWiFS Chlorophyll-a concentration:
Water leaving radiance is correlated to water physical and
biological properties such as water absorption and scattering,
and chlorophyll pigment concentration. Typically empirical
formulae can be derived to relate band ratios of satellite
sensed upwelled radiance to biological parameters such as
chlorophyll-a concentration.
ARGOS buoy:
Buoy near surface drift is calculated from positions recorded by the
ARGOS system on NOAA satellites.
TOPEX/POSEIDON:
TOPEX/POSEIDON satellite, at ~1336km above sea level.
SSM/I:
SSM/I on a series of U.S. Air Force Defense Meteorological
Satellite Program (DMSP) spacecraft at ~860 km above sea level.
Two satellites, the F-8 and F-10 were involved.
AVHRR:
NOAA polar-orbiting satellites at 833 or 870 km.
TMI:
The Tropical Rainfall Measuring Mission (TRMM) satellite
carries the TMI passive radiometer. It is in a non
sun-synchronous polar orbit at 350 km altitude.
ERS-1, -2:
The European Space Agency (ESA) European Remote Sensing (ERS-1)
satellite orbits at approximately 780 km above sea level.
NSCAT:
The NSCAT was the scatterometer instrument on board the Japanese Advanced
Earth Observation System (ADEOS) spacecraft. It was launched in a near-polar
sun-synchronous orbit at a 800 km altitude.
SeaWiFS:
SeaStar satellite carrying the SeaWiFS sensor is polar-orbiting at a 705 km
altitude.
ARGOS buoys:
Free drifting ocean buoys tracked by ARGOS, a French navigation
system on NOAA satellites. Buoys are drogued to follow the
near-surface currents between 10m and 20m below the sea surface.
TOPEX/POSEIDON: TOPEX/POSEIDON satellite
SSM/I: DMSP F-8 and F-10 satellites
AVHRR: NOAA satellites
ERS-1: ESA ERS-1
ARGOS buoy: ARGOS buoy
TOPEX/POSEIDON:
The objective of the TOPEX/POSEIDON mission is to obtain an ongoing
global view of earth's ocean topography with sufficient accuracy to
improve models designed to forecast global ocean circulation. By
meeting this objective, scientists are: determining ocean
circulation and variability; learning to understand the wind's role
in circulation; developing descriptions of the nature of ocean
dynamics; contributing to the understanding of the transport of
heat, mass, nutrients, and salt through the oceans; determining
geocentric ocean tides; investigating the interaction of currents
with waves; improving our knowledge of the marine geoid; and
increasing our understanding of lithospheric and mantle processes.
The measurement objective of the TOPEX/POSEIDON mission was to
determine ocean topography with a sea surface height measurement
precision of 3 cm and a geocentric sea level measurement accuracy
of 13 cm. Two altimeters were used in this mission.
SSM/I (DMSP F-8 and F-10 satellites):
The mission of the DMSP is to provide global, visual and infrared
cloud data and other specialized near real-time meteorological,
oceanographic and solar-geophysical data required to support
worldwide Department of Defense operations and high-priority
programs. Timely data are supplied to Air Force Global Weather
Central, the Navy Fleet Numerical Oceanography Center and to
deployed tactical receiving terminals worldwide.
AVHRR:
Each of the NOAA polar-orbiting satellites have carried an AVHRR as
one of three sensors aboard the spacecraft. AVHRR was designed for
multispectral investigations of meteorological, oceanographic, and
hydrologic parameters, measuring emitted and reflected radiance in
four or five spectral bands, spanning the visible portion of the
spectrum to the thermal infrared. AVHRR data is used operationally
by NOAA for input into weather forecasts.
ERS-1 -2:
The ERS-1 satellite was designed as a forerunner of a new
generation of satellites for environmental monitoring. It is the
first civilian satellite since Seasat to carry active microwave
instruments. Objectives include: improved understanding of
ocean-atmosphere interactions, ocean circulation and energy
transfer, Arctic and Antarctic ice sheet mass balance, improved
monitoring of dynamic coastal processes and pollution, and improved
detection and management of land use changes.
TMI:
The TRMM is a joint mission between NASA and The National
Space Development Agency (NASDA) of Japan designed to
monitor and study tropical rainfall and the associated
release of latent heat energy. The measurement of SST from
the TMI was not a primary mission objective, but
nevertheless represents a breakthrough in the ability to
monitor ocean SST in the presence of clouds.
NSCAT:
The objective of the NSCAT was to provide daily global
coverage of ocean winds.
SeaWiFS:
The objective of the SeaWiFS instrument was to provide
daily global coverage of derived biological/physical
parameters such as chlorophyll-a concentration, primary
productivity and light attenuation/clarity.
ARGOS buoys:
The objective of these buoys is to provide weather data and
information concerning ocean circulation.
TOPEX/POSEIDON:
There are two altimeters which operate alternately; a NASA
altimeter, which operates approximately 90% of the time and the
Centre National d'Etudes Spatiale (CNES) altimeter which operates
approximately 10% of the time. The NASA altimeter has two
frequencies (13.6 and 5.3 GHz) to measure the ionospheric
electron content in addition to the measurement of the satellite
altitude above the ocean surface. The CNES altimeter operates at
13.6-GHz.
SSM/I:
SSM/I measures surface and/or atmospheric emitted passive microwave
radiation in the form of brightness temperatures at the following
frequencies: 19.3, 22.2, 37.0, and 85.5 GHz.
AVHRR:
The sensor measures emitted and reflected radiation from Earth in
two visible channels and three infrared channels.
ERS-1 -2:
The Active Microwave Instrument (AMI) operated at 5.3 GHz
(C-band).
TMI:
The TMI radiometer operates at 10.7, 19.4, 21.3, 37 and 85 GHz.
NSCAT:
The NSCAT is a active Ku band (14 GHz) radar instrument
that measures the backscattered radar reflection from the
ocean surface.
SeaWiFS:
The SeaWiFS sensor is an optical scanner that measures
light radiance in 8 bands: 402-422, 433-453, 480-500,
545-565, 660-680, 745-785, and 845-885 nm.
ARGOS buoy:
Information not available.
TOPEX/POSEIDON altimeter:
For a description of the principles of operation, please refer to
the
TOPEX altimeter instrument document . Further information is
available in
Perspectives on an Ocean Planet.
SSM/I:
For a description of the principles of operation, please refer to
the
SSM/I instrument document.
AVHRR:
Each AVHRR scan views Earth for 51.282 milliseconds, during which
time each channel of the analog data output is digitized. Scans
occur at the rate of 6 per second, and the sampling rate of the
AVHRR sensors is 39,936 samples per second per channel. During a
scan, the detectors view an internal target, cold space, and the
external scene. The temperature of the internal target is
monitored, and space is assumed to have a black- body temperature
of 3K. In this way, a simple two-point linear calibration is done
internally (Schwalb, 1978).
ERS-1 -2 AMI:
In the wind scatterometer mode the AMI operated by recording the
change in radar reflectivity of the sea due to small ripples
(capillary waves) generated by the wind. For further information
see ESA SP-1146.
TMI:
The TMI is a passive microwave radiometer. The primary
frequency for SST retrieval is 10.7 GHz where atmospheric
attenuation is very small, with 97% of the sea surface
radiation reaching the top of the atmosphere. Using the
19.4, 21.3 and 35 GHz bands, the SST algorithm precisely
estimates the residual 3% attenuation due to oxygen, water
vapor and clouds. Horizontal-to-vertical polarization
ratios of the radiances are used to estimate sea surface
roughness.
NSCAT:
The overall principle is the same as for the ERS-1 and -2
scatterometers.
SeaWiFS:
Visible band radiance sensed by the SeaWiFS
instrument is correlated with physical and biological
water properties.
ARGOS buoy:
Drift of near-surface current is determined by the location of the
buoy which is determined by a global positioning system which
relays data through a series of satellites to Canada's MEDS
(Marine Environmental Data System).
TOPEX/POSEIDON altimeters:
The pulse is transmitted at a vertical incidence. The inclination
orbit allows the altimeter to sample from 66 deg. N to 66 deg. S
latitudes. The repeat cycle is 10 days - i.e., the satellite
passes vertically over the same location every 10 days, with an
error of less than 1 km.
SSM/I:
The SSM/I orbit is circular, sun-synchronous, and near-polar, with
an altitude of 860 km and an inclination of 98.8 degrees. The
orbital period is 102 minutes, and the local time for the
ascending equatorial crossing is 6:12 am. This orbit provides
complete coverage of the Earth, except for two small circular
sectors of 2.4 degrees centered on the North and South poles
(Wentz, 1988).
The scene is viewed over a scan angle of 102.4 deg. centered on
the ground track aft of the satellite, resulting in a scene swath
width of 1394 km. The spatial resolution of the SSM/I footprints
vary from 13-70 km depending on the frequency. The spatial
sampling interval is 25 km for all frequencies, except 85.5 GHz,
which is sampled at 12.5 km intervals.
AVHRR:
The AVHRR has a cross-track scanning system which use an
elliptical beryllium mirror rotating at 360 RPM about an axis
parallel to the Earth. The 110.8 deg. cross-track scan equates to
a swath width of about 2700 km. This swath width is greater than
the 25.3 deg. separation between successive orbital tracks, and
provides overlapping coverage. Coverage is global, twice daily, at
an instantaneous field of view (IFOV) of ~1.4 milliradians, giving
a ground field of view of ~1.1 km at nadir for a nominal altitude
of 833 km.
ERS-1, -2:
The AMI has a 500 km groundtrack that is offset 225 km from nadir.
The spatial resolution is about 50 km.
TMI:
The orbital geometry of TRMM satellite results in non
sun-synchronous coverage of the tropics between 40N to 40S
latitude. Resolution of the TMI is about 50 km with a 780 km
swath.
NSCAT:
The antennae of the NSCAT produce a 600 km groundtrack on each
side of the satellite with a 325 km nadir gap. The ground resolution
is about 25 km.
SeaWiFS:
The SeaWiFS instrument is an optical scanner and has a
swath width of 1600 km for Global Area Coverage (GAC) with
a 4 km resolution, and a 2700 km swath width for Local
Area Coverage (LAC) with a 1 km resolution.
ARGOS buoy:
The buoys are free ocean drifters.
TOPEX/POSEIDON altimeter:
The altimeter was developed and built by the Applied Physics Laboratory of the John Hopkins University (APL/JHU) under contract to the Wallops Flight Facility of NASA's Goddard Space Flight Center (GSFC) on behalf of JPL.
SSM/I:
Hughes Aircraft Company
AVHRR:
ITT Aerospace
ERS-1, -2 AMI:
European Space Agency.
TMI:
NASA and NASDA
NSCAT:
NASDA (Japan)
SeaWiFS:
Orbital Sciences Corporation
ARGOS buoy:
Information not available.
TOPEX/POSEIDON altimeters:
The total measurement error, 4.7 cm for the TOPEX system, is
significantly less than the mission requirement, which specifies a
total error of 13.7 cm.
SSM/I:
For a complete discussion of the SSM/I calibration, please refer
to SSM/I Instrument Evaluation (Hollinger et al., 1990)
AVHRR:
Channels 1 and 2 are calibrated to produce at-satellite radiances
using a time dependent correction which accounts for sensor
degradation and intercalibration among the satellites. Channels 4
and 5 are calibrated using a non-linear function based on the
internal calibration targets, baseplate temperatures, instrument
dependent response curves, and NOAA-provided gains and offsets.
Channel 3 is calibrated using the gains and offsets in the GAC
data record. The thermal channels are then converted to equivalent
brightness temperatures using a lookup table based on the inverse
Planck function convolved with the instrument response.
ERS-1, -2 AMI:
Information not available at this time.
TMI:
Information not available at this time.
NSCAT:
Information not available at this time.
SeaWiFS:
Visible band calibration is performed daily using the sun and
monthly using the moon as calibration sources.
ARGOS buoy:
Information not available at this time.
TOPEX/POSEIDON:
The total measurement error, 4.7 cm for the TOPEX system, is
significantly less than the mission requirement, which specifies a
total error of 13.7 cm.
SSM/I:
For a complete discussion of the SSM/I calibration, please refer
to SSM/I Instrument Evaluation (Hollinger et al., 1990).
AVHRR:
The instrument is designed to maintain a constant operating
temperature for the IR detectors and provide a signal-to-noise
ratio (SNR) of 3:1 at 0.5% albedo.
ERS-1, -2 AMI:
Information not available at this time.
TMI:
Information not available at this time.
NSCAT:
Information not available at this time.
SeaWiFS:
Information not available at this time.
ARGOS buoy:
Information not available at this time.
TOPEX/POSEIDON:
During the first 6 months of the mission, an intensive
verification campaign was conducted jointly by NASA and
CNES to calibrate and validate the satellite measurements
against in situ observations at the two verification
sites. JPL performed calibration of TOPEX/POSEIDON at
Platform Harvest off the coast of California near Point
Conception. Using data for 21 overflights of TOPEX and 6
overflights of POSEIDON, TOPEX had 2.9 cm uncertainty in
sea level and POSEIDON had 3.1 cm uncertainty in sea level
[Christensen, et al., 1994]. CNES chose Lampedusa island
in the Mediterranean Sea for its calibration study
[Menard, et al., 1994].In addition, sea level accuracy was
ascertained to within 3 cm over the Great Lakes [Morris &
Gill, 1994]. In the tropical Pacific, comparisons with
tide gauges show the TOPEX/POSEIDON has an accuracy of 2
cm when averaged over spatial scales of a few hundred
kilometers [Cheney, et al., 1994].
SSM/I:
For a complete discussion of the SSM/I calibration, please refer
to SSM/I Instrument Evaluation [Hollinger et al., 1990].
AVHRR:
The thermal infrared channels are calibrated in flight using a
view of a stable blackbody and space as a reference. Channels 1
and 2 have no onboard calibration capabilities, however, they are
calibrated before launch.
ERS-1, 2 AMI:
Calibration consists of internal monitoring of functions and
parameters within the instrument and comparison of the return with
natural or man-made targets. The former is a constant process and
the latter largely occurred during the calibration and validation
phase which occurred shortly after launch.
TMI:
Information not available at this time.
NSCAT:
Information not available at this time.
SeaWiFS:
Daily solar calibration; monthly lunar calibration.
ARGOS buoy:
Information not available at this time.
TOPEX/POSEIDON:
The satellite was launched on August 10, 1992. Data collection started
in September 1992 and as of April 1996 is still operational.
Information about the data acquisition is contained in the
Perspectives on
an Ocean Planet which is also available on a WWW site.
SSM/I:
Data in this product comes from instruments on two satellites the F-8
and F-10. The data has been processed by Frank Wentz of Remote Sensing
Systems, Santa Rosa, CA using algorithms that he has developed.
AVHRR:
Full resolution AVHRR data are continuously transmitted and recorded in
High Resolution Picture Transmission (HRPT) format. The Global Area
Coverage (GAC) data are subsampled to approximately 4 km IFOV, recorded
internally, and downlinked daily. The Level-1B data are defined as
radiometrically-corrected and calibrated data in physical units at full
instrument resolution as acquired. To produce the NOAA GAC Level-1B
data, the Level-0 (unprocessed) instrument data are quality controlled,
assembled into discrete data sets, and have calibration and Earth
location information appended. Data are then stored as full orbits
consisting of both ascending (daytime) and descending (nighttime) data.
ERS-1, -2 AMI:
The satellite launched in July 1991. The AMI consists of two separate
radars- a Synthetic Aperture Radar (SAR) and a scatterometer. (ESA,
1992) Data used in this product is derived from the scatterometer and
from a SAR wave operating mode. (Halpern et al., 1995). Data is limited
owing to the maximum operating time of 12 minutes per orbit.
TMI:
The TRMM was launched in November 1997. It payload consists of
five instruments: the Precipitation Radar, the TMI, the
Visible Infrared Radiometer, the Cloud and Earth Radiant Energy
Sensor, and the Lightning Imaging Sensor.
NSCAT:
The NSCAT was launched 17 August 1996 on the Japanese ADEOS
spacecraft.
SeaWiFS:
The SeaStar satellite was launched on August 1, 1997 with the
SeaWiFS sensor as its only science payload. The SeaWiFS
instrument is an optical scanner with 4 km resolution for the
Global Area Coverage (GAC) data. Similar to AVHRR, GAC data
derived from subsampled higher resolution 1 km data, and is
stored onboard the satellite and downlinked daily.
ARGOS buoy:
Data is tracked by ARGOS which is the French navigation system on NOAA
satellites. It is relayed to Canada's MEDS (Marine Environmental Data
System), (Halpern et al., 1994)
TOPEX/POSEIDON:
The main data product from this mission are the Merged Geophysical Data
Records (MGDRs) which contain the GDRs for both the TOPEX and POSEIDON
altimeters. A Guide document exists for the
MGDRs.
In addition there are comprehensive user manuals (Benada, 1993,
Callahan, 1993). A more accurate release of the TOPEX/POSEIDON data is
planned for release by JPL by mid 1996.
SSM/I:
All wind speed over the ocean products are produced by Frank Wentz
(Remote Sensing Systems). The JPL carries a complete line of these
products in addition to two other products; water vapor over the
ocean and liquid water vapor over the ocean. Information on this data
can be found in the
SSM/I
section of the JPL DAAC data catalog. There are also
SSM/I guides for some SSM/I data sets and for the sensor and
platform.
AVHRR:
Data in this product are derived from daytime SST data produced
operationally by NOAA's National Environmental Satellite and Data
Information Service (NESDIS). (Halpern, 1992). Note: The NOAA/NASA
Pathfinder SST products, also distributed by JPL PO.DAAC, use a newer,
more accurate algorithm.
ERS-1 AMI:
Data in this product were produced by Freilich and Dunbar.
TMI:
All TMI SST were produced by Frank Wentz (Remote Sensing Systems).
NSCAT:
Information not available.
SeaWiFS:
SeaWiFS data were acquired from the NASA SeaWiFS Project.
ARGOS buoy:
Data in this product was produced by MEDS which is located in Ottawa,
Canada.
These data are global in coverage within the confines of the available coverage. All data are presented as two-dimensional arrays with flags to indicate missing data and land. The typical size of a pixel is 1/3 degree latitude by 1/3 degree longitude (sea surface height from TOPEX/POSEIDON is calculated on a 2/3 x 2/3 degree grid. The buoy data is not gridded, it consists of start and end positions of buoy drift with in the monthly time periods.
Color maps (one per month) exist for all data. These comprise the atlases produced by Dr. D. Halpern et al. They are not available on-line but can be obtained from D. Halpern (halpern@pacific.jpl.nasa.gov).
AVHRR sea surface temperature, 1987-1999:
Data extends from ~70 N to ~ 70 S. Data at high and low latitudes
is limited by ice cover and by cloud cover. In addition, because
this data was processed by NESDIS for operational purposes, areas
of less interest for operational purposes have less processed data.
For this data set, four consecutive 7-day averages (produced by
RSMAS) are arithmetically averaged to form 28-day mean MCSST
values, (Halpern et al., 1992). "A 1024 x 512 grid was created by
computing the arithmetic mean of four 18 km x 18 km MCSSTs adjacent
to each other in a two dimensional array. The average MCSSTs of
4-element groups, which were independent of each other, represent
an approximate 1/3 degree by 1/3 degree gridded MCSST data set."
(This material is taken directly from Halpern et al., 1992)
ERS-1 surface wind velocity, 1992-1996:
Data extends from 60N to 60 S. "Although the spatial resolution of
the ERS-1 sigma-naught measurements is about 50 km, sigma-naught
values are reported on a 25-km grid within the measurement swath.
Therefore, adjacent sigma-naught, and, consequently, wind velocity
measurements are not independent. Geographical coordinates are
provided at the center of each 25-km x 25-km region. All east-west
and north-south wind components within nonoverlapping 1/3 degree by
1/3 degree squares were arithmetically averaged each day. Monthly
mean 1/3 degree by 1/3 degree wind components were computed from
the daily data." (This material is taken directly from Halpern et
al., 1994) The global coverage of 1/3" x 1/3" wind increases
during periods of time when ERS-1 has a 35-day repeat orbit rather
than the 3-day repeat orbit. (ESA, 1992). The ERS-1 AMI data is on
a 1080 X 540 element grid with the origin at 90N latitude and 0
degrees longitude.
GEOSAT sea surface height 1987-1988:
Data consisting of monthly mean 1/3 degree by 1/3 degree values
extends from approximately 75N to 75 S. Along each groundtrack, the
corrected sea surface height values, (corrected for sources of
error as discussed in Halpern et al. 1992), "were resampled at
fixed latitudes at about every 7 km using a cubic spline. No
interpolation was made over a data gap larger than 3 s (~21 km)."
(This material is taken directly from Halpern et al. 1992)
SSM/I surface wind speed, 1987-1999:
"The Wentz(1989b) GDR contains wind speed values in nonoverlapping
areas of 25 km x 25 km, which are arrayed across the 1394-km SSM/I
swath width. Geographical coordinates are provided at the center of
each 25-km x 25-km region. SSM/I wind speeds within nonoverlapping
1/3 degree by 1/3 degree squares were arithmetically averaged to
form the basic data set for the report. The origin of the global
1/3 degree by 1/3 degree grid is 90 N and 0 longitude. Most of the
1/3 degree by 1/3 degree areas contain at least 50 wind speed
values per month, or about 1-2 values per day. Coverage of SSM/I
wind speeds over the global ocean is nearly complete every 3 days."
(This material is taken directly from Halpern, 1992).
TOPEX/POSEIDON sea surface height, 1993-1999:
Data
consisting of monthly mean 2/3 degree by 2/3 degree values
extends from approximately 66 N to 66 S. Data from both
altimeters was used in this data set, (Halpern, 1995).
Along each groundtrack, the values "were resampled a 6km
intervals using a cubic spline. No interpolation was made
over a data gap larger than 3 s (~20 km)." (This material
is taken directly from Halpern, 1995).
TMI SST, 1998-1999:
Data are 50 km x 50 km nighttime global SST maps.
NSCAT wind vectors, 1997:
The monthly maps are 1/3 x 1/3 degree maps of wind speed overlaid
with wind vectors at 2.5 x 2.5 degree resolution.
SeaWiFS Chlorophyll-a concentration, 1998-1999:
Data consists of 0.5 degree monthly mean maps of Chlorophyll-a
concentration. These data were derived from the 9 km monthly mean
data provided by the SeaWiFS Project.
ARGOS buoy drift of near-surface current, 1989-1992:
Data consists of monthly start and end points for ARGOS
drifting buoys. These buoys are distributed across the
world oceans. In the hard-copy atlas series monthly drift
vectors have been computed (Halpern et al., 1994).
ERS-1, -2 surface wind velocity:
Surface wind velocity refers to the wind velocity (two directional
components) at the surface of the ocean and it is measured in m/s. The
source of the data is the AMI (in wind or wave mode).
GEOSAT sea surface height:
Sea surface height is the height of the sea relative to the reference
ellipsoid (Halpern et al., 1991). The source of the data is the
altimeter. Heights are measured in cm.
SSM/I surface wind speed:
Surface wind speed is the wind speed at the air/ocean interface. It is
measured in m/s by the SSM/I onboard the DMSP series of satellites. In
this study SSM/I winds are referenced to a 10 m height.
(Halpern, 1994)
TOPEX/POSEIDON sea surface height:
Sea surface height is the height of the sea relative to the reference
ellipsoid (Halpern et al., 1991). The source of the data is the
altimeter. Heights are measured in cm.
TMI sea surface temperature:
Sea surface temperature is the temperature of the surface of
the ocean and is measured in degrees C. The data range is
greater than -3.0 deg. C and less than 35 deg. C.
NSCAT wind velocity:
The surface wind velocity is referenced to a 10 m height.
SeaWiFS chlorophyll-a concentration:
Chlorophyll-a concentration is measured in the upper
water column to a maximum depth of approximately the first
light attenuation length. This attenuation depends on the
water absorption and scattering properties for light.
ARGOS buoy drift in near-surface current:
The current can be derived from the location of the buoys, given as a
latitude and longitude. The data presented here gives the start and end
position for monthly intervals. The source is from the ARGOS equipment
on NOAA satellites.
This data consists of XXX granules as available through the IMS. If the data is ordered on 8mm tape, the minimum order able amount is one year.
Most users acquire the data via FTP from ftp podaac.jpl.nasa.gov/pub/data_collections/monthly_mean_atlas Data from this site is organized by year. Within each year there are 12 files and, in the most recent years, read software is located in the data sub-directory.
ERS-1, -2 surface wind velocity, 1992-1999:
"For the present study, Freilich and Dunbar (1993a) calculated 10-m
neutral stability wind velocities, named CMODFD wind component data,
from ERS-1 sigma-naught data using an empirical C-band model function
(Freilich and Dunbar, (1993a) see Freilich and Dunbar (1993b) for a
general description of the technique), a maximum likelihood wind
retrieval algorithm (Naderi et al., 1991 and references therein), and
a variant of the circular median filter ambiguity removal algorithm
(Schultz,1990; Shaffer et al., 1991), As the ERS-1 C-band system had
very little upwind downwind discrimination skill, a limited
initialization was performed by choosing the most likely ambiguity
closest to the direction interpolated from contemporary operational
NOAA National Meteorological Center (NMC) surface analyses. It should
be noted that the NMC products were used only to initialize the
circular median filter algorithm; in many cases, the final selected
vectors obtained after application of the algorithm had significantly
different directions from (land were not the closest ambiguities to)
the NMC directions used to initialize the field." (This material is
taken directly from Halpern et al., 1994)
GEOSAT sea surface height 1987-1988:
A detailed discussion of the processing is contained the appropriate
hard copy atlases (Halpern et al., 1991; Halpern et al., 1992).
SSM/I surface wind speed, 1987-1999:
Wentz prepared the data that is presented in this product. The hard
copy atlases (Halpern et contain information of the algorithm's used.
This data set includes data from F-8 and F-10.
TOPEX/POSEIDON sea surface height data, 1993-1999:
"The TOPEX/POSEIDON sea surface data set used in this report is based
on the Geophysical Data Record (GDR) that was described by Callahan
(1994). The technique is complex to convert a radar altimeter's
travel time measurement between the satellite and the sea surface into
an accurate estimate of the elevation of the sea surface relative to a
reference ellipsoid, which becomes the oceanographic signal of
interest. Numerous algorithms are involved. Data processing
procedures, including application of environmental corrections, were
the same for both TOPEX and POSEIDON measurements, unless otherwise
noted." (This material is taken directly from Halpern et al., 1995)
An overview of the processing is available on pages 10 to 12 of Halpern et al., 1995. This document is available from Dr. D. Halpern (halpern@pacific.jpl.nasa.gov).
TMI sea surface temperature, 1998-1999:
Information not available.
NSCAT surface wind velocity, 1997:
Information not available.
SeaWiFS Chlorophyll-a concentration, 1998-1999:
Information not available.
ARGOS buoy drift of near-surface current, 1989-1992:
From the MEDS data, only data from drifting buoys was selected. "Only
drifting buoy data indicated by MEDS to be of high quality were used.
Data were eliminated when the position did not change throughout the
month." (This material is taken directly from Halpern et al., 1994).
Halpern et al. 1994 contains a description of criteria for further
ensuring the high quality of the data set.
AVHRR sea surface temperature:
One of the greatest limitations is the obstruction by clouds in the
field of view. Other sources of error include atmospheric gases and
emissions as well as water surface characteristics. "Major sources of
error are water vapor absorption in the lower atmosphere and aerosol
extinction, Radiance measurements from only cloud-free areas are
processed by NOAA into SST. Very conservative cloud tests, which
involve various combinations of the visible and infrared AVHRR/2 data,
detect clouds so that cloud-free SSTs are computed (McClain et al.,
1985); On a typical day, less than 2% of the maximum possible number of
SSTs are retained." (This material is taken directly from Halpern et
al., 1991)
ERS-1, -2 surface wind velocity:
Sources of possible lie in the algorithms that relate surface roughness
to wins speed and in resolving the directional ambiguity. See Halpern
et al., 1994 for a discussion of accuracy.
GEOSAT sea surface height:
Sources of error in the calculation of sea surface height include the
orbit, tide corrections and environmental corrections (atmospheric and
ionospheric).
SSM/I surface wind speed:
Sources of error in the calculation are thought to be largely
environmental.
TOPEX/POSEIDON sea surface height data:
Sources of error in the calculation of sea surface height include the
orbit, tide corrections and environmental corrections (atmospheric and
ionospheric). A discussion of these factors is included in Halpern et
al, 1995. For additional information, please refer to Benada, 1993,
and some of the papers in the
post launch
bibliography maintained by the University of Texas.
TMI:
Major errors include uncorrected sea surface roughness effects
and atmospheric attenuation.
NSCAT:
Similar errors as with ERS-1 and -2 AMI.
SeaWiFS:
Sources of error include uncorrected atmospheric contamination,
uncorrected effects due in water light scattering (primarily in
coastal Case-2 waters), and sensor calibration drift and
instrument noise.
ARGOS buoy drift of near-surface current:
A variety of different buoys are used as free drifters and there are
fundamental differences between their behavior, (Halpern et al., 1994).
"Caution must be exercised in the interpretation of the buoy drift as
near-surface current because of the unknown status and quality of the
buoy and the drogue." (This material is taken directly from Halpern et
al., 1994). It should be noted that there is no information in this
data set concerning the movement of a buoy with in a month, i.e. if the
start point is close to the end point, it is not known whether the buoy
is in a slow moving current or whether it is in a fast moving eddy.
Phone: (626) 744-5508
Fax: (626) 744-5506
Email:
podaac@podaac.jpl.nasa.gov
URL:
http://podaac.jpl.nasa.gov
For hard-copy atlases contact Dr. D. Halpern:
E-mail: halpern@pacific.jpl.nasa.gov
Fax: (818) 393-6720
Phone: (818) 354-5327
The hard copy atlases are available from Dr. D. Halpern. The hard copy atlases are not available through the JPL DAAC.
Dr. D. Halpern can be contacted at halpern@pacific.jpl.nasa.gov.
Callahan, P., TOPEX/POSEIDON Project GDR Users Handbook, Rep. JPL D-8944, Rev. A, Jet Propulsion Laboratory, Pasadena, CA, 1993.
Callahan, P.S, (1994) TOPEX/POSEIDON Project GDR users handbook. JPL Internal Document D-8944, Revision A, Jet Propulsion Laboratory, Pasadena, 84pp
Chelton, D.B. (1988) WOCE/NASA altimeter algorithm workshop. U.S. WOCE Technical Report No. 2, U.S. Planning Office for WOC-E, Texas A&M University, College Station, 70pp.
Cheney, R.E., B.C. Douglas, R.W. Agreen, L.L. Miller, D.L. Porter and N.S. Doyle (1987) GEOSAT altimeter geophysical data record user handbook. NOAA Technical Memorandum NOS-NGS-46, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Washington, 32 pp.
Christensen, E.J., B.J, Haines, S.J. Keihm, C.S. Morris, R.A. Norman, G.H. Purcell, B.G. Williams, B.D. Wilson, G.H. Born, M.E. Parke, S.K. Gill, C.K. Shum, B.D. Tapley, R. Kolenkiewicz and R.S. Nerem (1994) Calibration of TOPEX/POSEIDON at Platform Harvest, Journal of Geophysical Research, 99, 24465-24486.
European Space Agency, 1992, "ERS-1 System", ESA SP-1146, 87 pp.
Freilich, M, H. and R. S. Dunbar (1993a) A preliminary C-band scatterometer Inodel function for the ERS-1 AMI instrument. Proceedings of First ERS-I Symposium, ESA SP-359, European Space Agency, Paris, 79-84.
Freilich, M. H, and R. S. Dunbar (1993b) Derivation of satellite wind model functions using operational surface wind analyses: An altimeter example. Journal of Geophysical Research 98, 14633-14649.
Frain, W.E., M. H. Barbagallo and R. J. Harvey (1987) The design and operation of GEOSAT. Johns Hopkins APL Technical Digest, 8, 184-189.
Halpern, D., P. Woiceshyn, V. Zlotnicki, O. Brown, G. Feldman, M. Freilich and F. Wentz (2000) An Atlas of Monthly Mean Distributions of SSMI Surface Wind Speed, AVHRR Sea Surface Temperature, TMI Sea Surface Temperature, AMI Surface Wind Velocity, SeaWiFS Chlorophyll-a, and TOPEX/POSEIDON Sea Surface Topography During 1998. JPL Publication 00-08, Jet Propulsion Laboratory, Pasadena, 101 pp
Halpern, D., L. Fu, W.Knauss, G.Pihos, O. Brown, M. Freilich and F. Wentz (1995) An atlas of monthly mean distributions of SSMI surface wind speed, AVHRR/2 sea surface temperature, AMI surface wind velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface wind velocity during 1993. JPL Publication 95-3, Jet Propulsion Laboratory, Pasadena, 86 pp.
Halpern, D., W. Knauss, O. Brown, M. Freilich and F. Wentz (1994) An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, AMI surface wind components, and ECMWF surface wind components during 1992. JPL Publication 94-4, Jet Propulsion Laboratory, Pasadena, 143 pp.
Halpern, D., W. Knauss, O. Brown and F. Wentz (1993a) An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1991. JPL Publication 93-10, Jet Propulsion Laboratory, Pasadena, 111 pp.
Halpern, D., W. Knauss, O. Brown and F. Wentz (1993b) An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1990. JPL Publication 93-1, Jet Propulsion Laboratory, Pasadena, 111 pp.
Halpern, D., W. Knauss, O. Brown and F. Wentz (1992a) An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1989. JPL Publication 92-17, Jet Propulsion Laboratory, Pasadena, 112 pp.
Halpern, D., V. Zlotnicki, J. Newman, D. Dixon, O. Brown and F. Wentz (1992b) An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1987. JPL Publication 92-3, Jet Propulsion Laboratory, Pasadena, 111 pp.
Halpern, D., V. Zlotnicki, J. Newman, O. Brown and F. Wentz (1991) An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1988. JPL Publication 91-8, Jet Propulsion Laboratory, Pasadena, 110 pp.
Hollinger, J.P , J.L. Pierce and G.A. Poe (1990) SSMI instrument evaluation. IEEE Transactions on Geoscience and Remote Sensing, 28, 781-790.
McClain, E. P., W. G. Pichel and C.C. Walton (1985) Comparative performance of AVHRR-based multichannel sea surface temperatures. Journal of Geophysical Research, 90, 11587-11601.
Menard, Y., E. Jeansou and P. Vincent (1994) Calibration of the TOPEX/POSEIDON altimeters over Lampedusa with additional results over Harvest. Journal of Geophysical Research, 99, 24487-24504.
Naderi, F. M., M. H. Freilich: and D. G. Long (1991) Spaceborne radar measurement of wind velocity over the ocean -- An overview of the NSCAT scatterometer system. Proceedings of IEEE, 79, 850-866.
Oescheger, H. (1988) The ocean system- ocean/climate and ocean/CO2 interactions. In: Scales and Global Change. Ed.: T. Rosswall, R.G. Woodmansee and P.G.Risser, John Wiley & Sons, New York, 319-352.
Palmer, T. N. (1986) Influence of the Atlantic, Pacific and Indian Oceans on sahel rainfall. Nature, 322, 251-253.
Philander, S.G.H. (1989) El Nino, La Nina, and the Southern Oscillation. Academic Press, San Diego, 293 pp.
Schultz, H. (1990) A circular median filter approach for resolving ambiguities in wind fields retrieved from spaceborne scatterometer data. Journal of Geophysical Research, 95, 5291- 5303.
Shaffer, S. J., R. S. Dunbar, S. V. Hsiao and D. G. Long (1991) A median-filter-based ambiguity removal algorithm for NSCAT. IEEE Transactions on Geoscience and Remote Sensing, 29, 167-174.
Stommel, H., and M, Fieux (1978) Oceanographic Atlases.'Woods Hole Press, Woods Hole, Massachusetts, 6 pp + 97 charts.
Wentz, F.J., L.A. Mattox and S. Peteherych (1986) New algorithms for microwave measurements of ocean winds: Applications to SEASAT and the special sensor microwave imager. Journal of Geophysical Research, 91, 2289-2307.
Wentz, F.J. (1988) Water vapor path length correction for altimeters. In: Appendix to U.S. WOCE Technical Report No. 2 edited by D.B. Chelton, U.S. Planning Office for WOCE, Texas A&M University, College Station, 5 pp
Wentz, F.J. (1989) Use's manual: SSMI geophysical tapes. RSS Technical Report 060989, Remote Sensing Systems, Santa Rosa, California 16 pp
Zlotnicki, V., A. Hayashi and L.-L. Fu (1990) The JPL-0ceans-8902 version of GEOSAT altimetry data. JPL Internal Document D-6939, Jet Propulsion Laboratory, Pasadena, 17 PP + 60 charts.
An on-line bibliography of TOPEX/POSEIDON Post-launch publications is available from the University of Texas