We have reprocessed the entire AMSR2 data set from May 2012 to present.  Forward processing is now V7.2    Data formats are identical. 

Changes to the data include two fixes: 

AMSR2 / AMSRE

Introduction

The Advanced Microwave Scanning Radiometer has operated on three satellites: 

  • AMSR-2 on JAXA's GCOM-W1 spacecraft, launched May 18, 2012.  This instrument is currently operating.
  • AMSR-E on NASA's EOS Aqua spacecraft, launched May 4, 2002.  The instrument stopped rotating Oct 4, 2011.
  • AMSR on JAXA's ADEOS-II spacecraft, launched Dec 14, 2002.  The satellite solar panels failed Oct 25, 2003.

In this web site, we use the term AMSR-J to represent the AMSR radiometer flown by JAXA on ADEOS-II.  This distinguishes it from the AMSR-E on the NASA Aqua satellite and the AMSR-2 instrument on the GCOM-W1 satellite.

We have processed data from all these instruments to provide the typical RSS microwave radiometer ocean measurement product suite consisting of: Sea Surface Temperature(SST), Surface Wind Speeds (low and medium frequency), Atmospheric Water Vapor, Cloud Liquid Water, and Rain Rate.  The AMSR-2 and AMSR-E ocean products are created with the Version-7 processing, making them consistent with WindSat and the SSM/I  and SSMIS.   AMSR-J currently remains as Version-5 data.  The AMSR2 data were reprocessed in July 2014 to version-7.2.  The small changes include a correction for non-linearity in the 11 V low noise amplifier when it gets very hot and using a correct footprint size which decreases the rain rates a little from version-7.1.

A key feature of these AMSR instruments is the ability to see through clouds, thereby providing an uninterrupted view of ocean measurements.  There are differences between the three instruments as outlined in the table below. 

  AMSR-2 AMSR-E AMSR-J
Satellite Platform GCOM-W1 AQUA ADEOS-II
Altitude 700 km 705 km 802.9 km
Equator Crossing Time
(Local time zone)
1:30 PM Ascending
1:30 AM Descending
1:30 PM Ascending
1:30 AM Descending
10:30 PM Ascending
10:30 AM Descending
Antenna Size 2 m 1.6 m 2 m
Swath Width 1450 km 1450 km 1600 km

The wider swath of AMSR-J provides greater coverage, but comes at the expense of accuracy near the swath edges. Here is a worst case example:

 

Figure 1.  AMSR-J swath edge artifacts are only obvious in SST, and are most prominent early in the mission, when the spacecraft position was most unstable and least accurately known.

Instrument Description

The AMSR instruments are dual-polarized, conical scanning, passive microwave radiometers.  Each is placed in a near-polar orbit which allows for up to twice daily sampling of a given Earth location.  The eight instrument channels are summarized in the following tables. 

We use an on-orbit calibration method developed by RSS to convert counts to brightness temperatures. Calibration methodology and preliminary validation results are described in the following conference paper:  "On-Orbit Calibration of AMSR-E and the Retrieval of Ocean Products"

AMSR-2 on GCOM-W1

Band [GHz] Polarization

Spatial Resolution
(3-dB footprint size)
[km x km]

6.93 V,H 62 x 35
7.3 V,H 62 x 35
10.65 V,H 42 x 24
18.7 V,H 22 x 14
23.8 V 19 x 11
36.5 V,H 12 x   7
89.0 V,H   5 x   3

 

AMSR-E on Aqua

Band [GHz] Polarization

Spatial Resolution
(3-dB footprint size)
[km x km]

6.93 V,H 75 x 43
10.65 V,H 51 x 29 
18.7 V,H 27 x 16 
23.8 V 32 x 18
36.5 V,H 14 x   8
89.0 V,H   6 x   4

 

AMSR on ADEOS-II

Band [GHz]

Polarization

Spatial Resolution
(3-dB footprint size)
[km x km]

6.93 V,H 70 x 40
10.65 V,H 46 x 27
18.7 V,H 25 x 14
23.8 V,H 29 x 17
36.5 V,H 14 x   8
50.3 V 10 x   6
52.8 V 10 x   6
89.0 V,H   6 x   3

 

RSS AMSR Data Products

The current version of the RSS radiative transfer model and radiometer processing code is Version-7.  Both AMSR-2 (v7.2) and AMSR-E (v7) are available as version-7 products.  AMSR-J data products remain Version-5.  The AMSR-2 V7 data were first available as V7.1 in January 2014 and reprocessed to V7.2 in July 2014, the AMSR-E V7 data were released October 2011.  We recommend using only the latest data. 

We produce Daily binary data files and Time-Averaged (3-day, weekly and monthly) data files for all instruments. The daily files consist of ocean measurements mapped to a regular grid complete with data gaps between orbits. Two maps exist for each parameter, one of ascending orbit segments (local daytime passes) and the other of descending orbit segments (local nighttime passes). Data on each of the segment maps are overwritten at both the high latitudes where successive orbits cross and at the "seam" or region where the last orbit of the day overlaps the first orbit of the day. Daily data files contain time maps consisting of the UTC observation time for each set of passes (ascending and descending). Time-Averaged data files do not contain any time information.

Gridded data are organized according to observation date. All dates and times are Coordinated Universal Time (UTC), also known as Greenwich Mean Time (GMT), Zulu Time (Z), Universal Time (UT), and World Time. Data products include daily and time averaged geophysical data as follows:

Daily orbital data mapped to 0.25 degree grid divided into 2 maps based on ascending and descending passes early data may be overwritten by later data at high latitudes and daily "seam"
3-Day average of 3 days ending on and including file date
Weekly average of 7 days ending on and including the Saturday file date
Monthly average of all data within the calendar month

Each binary data file available from our ftp site consists of fourteen (daily) or six (averaged) 0.25 x 0.25 degree grid (1440,720) byte maps. For daily files, seven daytime, ascending maps in the following order, Time (UTC), Sea Surface Temperature (SST), 10 meter Surface Wind Speed (WSPD-LF), 10 meter Surface Wind Speed (WSPD-MF), Atmospheric Water Vapor (VAPOR), Cloud Liquid Water (CLOUD), and Rain Rate (RAIN), are followed by seven nighttime maps in the same order. Time-Averaged files contain just the geophysical layers in the same order [SST, WSPD-LF, WSPD-MF,VAPOR, CLOUD, RAIN].

Acronym Product
Name
Product
Description
Scale Offset Valid Data Range Reason for No Data
TIME Time

Minutes since midnight GMT
Fractional hour of day GMT

6.0
0.1

0.
0.

0 to 1440
0.0 to 24.0

no data
SST Sea surface temperature Temperature of top layer (skin) of
water ~1 mm thick
0.15 -3.0 -3 to 45 deg high winds (<20 m/s), sun glint, rain, RFI, near sea ice or land (~75 km)
WSPD_LF 10-m wind speed Wind speed using 10.7 GHz channel 0.2 0. 0. to 50.0 m/s sun glint, rain, RFI, near sea ice or land (~50 km)
WSPD_MF 10-m wind speed Wind speed using 18.7 GHz channel 0.2 0. 0. to 50.0 m/s sun glint, rain RFI, near sea ice or land (~50 km)
VAPOR Columnar atmospheric water vapor Total gaseous water contained in a
vertical column of atmosphere
0.3 0.

0. to 75.0 mm
1 gm/cm2= 10mm

heavy rain or near land (~25 km)
CLOUD* Columnar cloud liquid water Total cloud liquid water contained in a
vertical column of atmosphere
0.01 -0.05 -0.05 to 2.45 near land (~25 km)
RAIN Rain rate Rate of liquid water precipitation 0.1 0. 0. to 25.0 mm/hr near land (~25 km)

* Note:  The Version-5 AMSR-J data do not have the cloud offset shown in this table.  For Version-5, the valid cloud range is 0 to 2.5 mm.  These files also only contain 1 wind (LF) for a total of 6 instead of 7 data layers.

The data values between 0 and 250 need to be scaled to obtain meaningful geophysical data. To scale the data, multiply by the scale factors listed in the table above.

We produce two standard rain-free radiometer wind products:  WSPD_LF (low-frequency) and  WSPD_MF (medium frequency).  The first, WSPD_LF is created using the frequency channels at 10.65 GHz and above (see tables above) and is most similar to the only wind offered in the version-5 AMSR-E data files or the first wind of the TMI files. The second, WSPD_MF, uses frequency channels at 18.7 GHz and above and is most similar to the SSM/I and SSMIS winds.

Each wind product has distinct advantages.  The WSPD_LF is less affected by the atmosphere and rain, but is affected by 10.65 GHz RFI and sun glitter effects. The WSPD_MF has a higher effective spatial resolution, is less affected by ice and land contamination, and is only slightly affected by sun glitter effects and RFI. The WSPD_MF are a little noisier than the WSPD_LF.

The daily, 3-day and monthly maps are stored in appropriate year and month subdirectories. The weekly data files are stored in the /weeks directory.

The file names have the following naming conventions:

Time Directory Path File Name
Daily [year]/[month]/ sat_yyyymmddv7.#.gz
3-Day [year]/[month]/ sat_yyyymmddv7.#_d3d.gz
Weekly weeks/ sat_yyyymmddv7.#.gz
Monthly [year]/[month]/ sat_yyyymmv7.#.gz

Where "sat",  "yyyy", "mm", "dd", and "#" stand for:

sat satellite f34(amsr2), amsre, amsrj

yyyy 

 year 2002, 2003 etc.
mm   month 01 (Jan), 02 (Feb), etc.
dd  day 01, 02, etc.
#   version 7,  7.1,  7.2,  etc

 

The center of the first cell of the 1440 column and 720 row map is at 0.125 E longitude and -89.875 latitude. The center of the second cell is 0.375 E longitude, -89.875 latitude. The data values fall between 0 and 255. Specific values have been reserved:

0 to 250 =  valid geophysical data
251 = missing SST or wind speed due to rain, or missing water vapor due to heavy rain
252 = sea ice
253 = observations exist, but are bad (not used in composite maps)
254 = no observations
255 = land mass

Missing Data

There are gaps within these data. Missing data generally affect Daily and 3-Day products, but can also reduce the number of observations in Weekly and Monthly averages.

When browsing imagery, the navigation may skip dates with no data, or you may see a blank map stating that no data are available for that time.

Binary data files for dates with completely missing data are not produced; they will be absent from our FTP server.

Data gaps are generally due to missing data upstream from our processing facility, such as the instrument being turned off. Occasionally, there are delays in obtaining and/or processing recently recorded data; beyond several weeks, it is unlikely that missing data will become available.

Dates for which AMSR-E data are completely missing include:

date range # days
2002.06.28 1
2002.07.30 - 2002.08.07 9
2002.09.13 - 2002.09.19 7
2003.10.30 - 2003.11.05 7
2004.11.19 1
2006.11.18 1
2007.11.28 1
2008 none 0
2009 none 0
2010.02.03 - 2010.02.04 2
2011 instrument stopped Oct 4th 2011 88

 

Dates for which AMSR2 data are completely missing include:

date range # days
2013.05.11 - 2013.05.13    3

Browse Images

Each daily, 3-day, weekly and monthly browse image map displays one geophysical parameter: Sea Surface Temperature (SST), 10 meter Surface Wind Speed (WSPD-LF), 10 meter Surface Wind Speed (WSPD-MF), Columnar Water Vapor (VAPOR), Cloud Liquid Water (CLOUD), or Rain Rate (RAIN). The daily maps display the daytime or nighttime satellite passes separately. The date of the data displayed is the UTC date when the data were collected. The scale for each map is located next to the map for reference. The scale bar extends between zero (-1 for sst and -0.05 for cloud) and the defined maximum listed below:

Measurement Daily 3-Day Weekly Monthly Units
Sea Surface Temperature: 34 34 34 34 degree Celsius
Surface Wind Speed: 30 30 30 30 meters/second
Atmospheric Water Vapor: 75 75 75 75 millimeters
Cloud Liquid Water: 0.3 0.3 0.3 0.3 millimeters
Rain Rate: 20 10 5 2 millimeters/hour

There are many gaps within the AMSR-J data set. Please use the browse imagery or FTP site to determine specific availability.

 

Read Routines

Binary file read routines and verification files are available on our ftp server in the amsre/support directory.  Routines are written in IDL, Matlab, Fortran and Python.

Validation

Validation of AMSR2 products like all microwave ocean products from RSS undergo continual validation.  We post important findings here.

Rain Rates

AMSR2 rain rates are higher in the tropics than other RSS satellite products.  The figure below shows that the difference between AMSR2 and SSMIS (F17) in the tropics is +9.9%.  The difference between AMSR2 rain rates and the 10-minute rain rates from the tropical buoy array is +8.3% using a 3-hour collocation radius.  In the mid-latitudes, AMSR2 rain rates are lower than SSMIS, leading to a zero overall global difference.  The source of this latitude-dependent difference in AMSR2 rain is currently under investigation as part of our “Complete Uncertainty Characterization of the DISCOVER Earth System Data Records” project.

rain rate comparison figure

 

Related Data

AMSR ocean product data are also available from other sources.  AMSR-E data are produced at the NASA Snow and Ice Data Center (NSIDC) using RSS processing algorithms.  Visit NSIDC for data description and data access.

AMSR-J and AMSR-2 data are also available from the Japanese Space Agency (JAXA). 

References

Wentz, F. J. and T. Meissner, (2000), AMSR Ocean Algorithm, Version 2, vol. 121599A-1, p. 66, Remote Sensing Systems, Santa Rosa, CA

Wentz, F. J. and T. Meissner, (2007), AMSR-E Ocean Algorithms; Supplement 1, vol. 051707, p. 6, Remote Sensing Systems, Santa Rosa, CA.

Wentz, F. J., C. L. Gentemann and P. D. Ashcroft, On-orbit calibration of AMSR-E and the retrieval of ocean products, paper presented at 83rd AMS Annual Meeting, Long Beach, CA, 2003.

Wentz, F. J., C. L. Gentemann and K. A. Hilburn (2005), Three years of ocean products from AMSR-E: Evaluation and applications, paper presented at Proceedings of the 2005 IEEE International Geoscience and Remote Sensing Symposium,Seoul, Korea.

Hilburn, K. A. and F. J. Wentz, (2008) Intercalibrated Passive Microwave Rain Products From the Unified Microwave Ocean Retrieval Algorithm (UMORA), J. Clim. Appl. Meteorol., 47, 778-794.

Acknowledgements

AMSR data are produced by Remote Sensing Systems and sponsored by the NASA Earth Science MEaSUREs DISCOVER Project and the NASA AMSR-E Science Team.  We are grateful to JAXA and JPL for providing us with AMSR-2, AMSR and AMSR-E instrument data.

How to Cite These Data

Continued production of this data set requires support from NASA.  We need you to be sure to cite these data when used in your publications so that we can demonstrate the value of this data set to the scientific community.  Please include the following statement in the acknowledgement section of your paper:

"AMSR data are produced by Remote Sensing Systems and sponsored by the NASA Earth Science MEaSUREs DISCOVER Project and the NASA AMSR-E Science Team. Data are available at www.remss.com. "

Sign up for our instrument alert email list

If you would like to be alerted when we have problems delivering these data, please add your name to our email list by submitting a request to support@remss.com.  Use "add me to the mail list" for the subject line and be sure to specify the instruments you wish to be informed about in the body of the message.