The Advanced Microwave Scanning Radiometer has operated on two satellites:
- AMSR-E on NASA's Aqua spacecraft, launched May 4, 2002. The instrument stopped rotating Oct 4, 2011.
- AMSR on JAXA's MIDORI-II spacecraft, launched Dec 14, 2002. The instrument operated for 237 days in 2003 (January through October).
In this web site, we use the term AMSR-J to represent the AMSR radiometer flown by JAXA on Midori-II. This distinguishes it from the AMSR-E on Aqua.
We have processed data from both instruments to provide the typical RSS microwave radiometer ocean measurement suite consisting of: Sea Surface Temperature(SST), Surface Wind Speed, Atmospheric Water Vapor, Cloud Liquid Water, and Rain Rate. The AMSR-E ocean products are currently Version-7, making them consistent with WindSat and SSMI/SSMIS. AMSR-J remains as Version-5 for now.
A key feature of both AMSR instruments is the ability to see through clouds, thereby providing an uninterrupted view of ocean measurements. There are differences between these instruments as outlined in the table below.
|Altitude||705 km||802.9 km|
|Equator Crossing Time
(Local time zone)
|1:30 PM Ascending
1:30 AM Descending
|10:30 PM Ascending
10:30 AM Descending
|Antenna Size||1.6 m||2 m|
|Swath Width||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.
Both AMSR-J (on ADEOS-2) and AMSR-E (on Aqua) are a dual-polarized, conical scanning, passive microwave radiometers. The near-polar orbit of these satellites allow for up to twice daily sampling of a given Earth location. The six instrument channels are summarized in the following table.
The AMSR-E Ocean Products produced for this website are made using a modified version of the AMSR-E Direct Broadcast (DB) algorithm developed for NASA. 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 paper: "On-Orbit Calibration of AMSR-E and the Retrieval of Ocean Products"
|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|
RSS AMSR Data Products
The current version of AMSR-E data products is Version-7. The current version of AMSR-J data products is Version-5. The AMSR-E V7 data were released October 2011. We recommend no longer using any previous version as significant improvements have been made.
We produce Daily binary data files and Time-Averaged (3-day, weekly and monthly) data files for both these 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].
|Scale||Offset||Valid Data Range||Reason for No Data|
Minutes since midnight GMT
0 to 1440
|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. to 75.0 mm
|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
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.
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|
Where "yyyy", "mm", "dd", and "vv" stand for:
|year||2002, 2003 etc.|
|mm||month||01 (Jan), 02 (Feb), etc.|
|dd||day||01, 02, 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|
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|
|2002.07.30 - 2002.08.07||9|
|2002.09.13 - 2002.09.19||7|
|2003.10.30 - 2003.11.05||7|
|2010.02.03 - 2010.02.04||2|
|2011 instrument stopped Oct 4th 2011||88|
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:
|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|
There are many gaps within the AMSR-J data set. Please use the browse imagery or FTP site to determine specific availability.
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.
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.
AMSR-E 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 and AMSR-E 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-E 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. "
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