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FAQ
General Questions Documentation Questions Data Access Questions AIRS Subsetting Questions AIRS Imagery Questions Science | Answers to General Questions - What is AIRS?
The Atmospheric Infrared Sounder (AIRS) is a facility instrument onboard the polar-orbiting Earth Observing System (EOS) Aqua satellite which was successfully launched on May 4, 2002. In combination with the Advanced Microwave Sounding Unit (AMSU-A) and the Humidity Sounder for Brazil (HSB), the AIRS instrument suite constitutes an innovative atmospheric sounding group of visible, infrared, and microwave sensors. - What does the AIRS instrument suite measure?
The AIRS instrument is a high resolution spectrometer with 2378 bands in the thermal infrared spectral region (3.74 - 15.4 micrometers) and 4 bands in the visible spectral region (0.4 - 1.0 micrometers). These ranges have been specifically selected to determine atmospheric temperature with an accuracy of of 1 K per 1 km thick layer in the troposphere and moisture profiles at an accuracy of 20% per 2 km thick layer in the lower troposphere (20% 60% in the upper troposphere). See the AIRS instrument guide for details. AMSU-A is a multi-channel microwave temperature/humidity sounder that measures global atmospheric temperature profiles and provides information on atmospheric water in all of its forms (with the exception of small ice particles, which are transparent at microwave frequencies). Information from AMSU-A in the presence of clouds is used to correct the AIRS infrared measurements for the effects of clouds. See the AMSU-A instrument guide for details. HSB is primarily a humidity sounder providing supplementary water vapor and liquid data to be used in the cloud clearing process. Due to its higher spatial resolution (which equals that of AIRS) and a higher scan rate, the measurement density is 2.4 times that of AMSU-A. See the HSB instrument guide for details. The HSB instrument failed on February 5th, 2003. - What AIRS data products are available from Goddard GES DISC? Does the data cost anything?
See AIRS Data Product page for the complete list of publicly available products. AIRS data is available to thepublic at NO COST. - What is AIRS Algorithm Version versus Data Collection?
Version 2.7 Algorithm produced Collection 1 Version 3 Algorithm produced Collection 2 Version 4 Algorithm produced Collection 3 Version 5 Algorithm produces Collection 5 Starting with the delivery of Algorithm Version 4 in 2005, AIRS Instrument Team began to produce two types of retrievals due to the failure of HSB on February 5, 2003. Data types that encompass retrievals using HSB data will have "H" letter in the short name of the data type, e.g. AIRH2RET. Retrievals without HSB have the familiar names, e.g. AIRX2RET. Documentation is associated with the Version of the Algorithm, which is embedded in the data filenames. Data are organized and stored as Collections at GES DISC. Collections are different from the Algorithm Version until Version 5 where data version became the same as the collection. Our search engines will naturally show Collections. Because reprocessing earlier data takes time and multiple months are scheduled concurrently, Collections generated by the previous Algorithm Version will necessarily coexist for a period of time along with Collections generated by the current Algorithm Version. Users are cautioned to double-check the Collection before downloading to ensure the data are those desired. - How do I apply QA filtering on Level-1B IR and Level-2 standard products?
AIRS products contain a comprehensive set of QA flags that allow users to select the best quality data in their research. AIRS documentation package contains 3 documents that address this topic. For convenience, GES DISC has produced a summary document on how to apply QA filtering. It has links to the full AIRS QA documents. - What is the format of AIRS data products? Are conversion tools available?
All AIRS data products are in HDF-EOS format. See our Tools page for details. - What is the daily volume of AIRS L1B and L2 data products, and the size of each granule?
The daily volume of AIRS L1B products is: - L1B-AIRS-IR-Rad: 13,440 Mb
- L1B-Vis/NIR-Rad: 2,640 Mb
- L1B-AMSU-Rad: 144 Mb
- L1B-HSB-Rad: 408 Mb
- L2-Standard-Product: 552 Mb
- L2-Support-Product: 2,496 Mb
- L2-Cloud-Cleared-Rad: 2,280 Mb
The average size of each granule: - L1B-AIRS-IR-Rad: 56 Mb
- L1B-Vis/NIR-Rad: 11 Mb
- L1B-AMSU-Rad: 0.6 Mb
- L1B-HSB-Rad: 1.7 Mb
- L2-Standard-Product: 2.3 Mb
- L2-Support-Product: 10.4 Mb
- L2-Cloud-Cleared-Rad: 9.5 Mb
- May I order data in smaller units than your granules (subsets of the granules)?
Yes. When you order data from GES DISC, you can add on channel or variable subsetting options to be applied on L1B and L2 products. - What is the length of time between satellite measurement and data availability?
There will typically be a 30-hour to 36-hour lag for AIRS L1B processed data. - Where do I go online to search and order AIRS data?
There are several options available for obtaining AIRS data, see our Data Access page for a list of options. Because all the AIRS data are online, these data access methods will converge on the FTP step at the end. Pick one method that suits your preference. - Why AIRS L1B HSB radiation data (AISRHBRAD brightness temperature) always display -9999.0 for channel 1?
HSB channel 1 was never implemented and so always -9999.0. There are four channels (channel 2-5) in HSB and their characteristics are summarized below. Channel | Central Frequency (GHz) | Bandwidth (MHz) | 1 | Deleted (89Ghz) | | 2 | 150.0 | 4000 | 3 | 183.31
± 1.0 | 2x500 | 4 | 183.31
± 3.0 | 2x1000 | 5 | 183.31
± 7.0 | 2x2000 | | Answers to Documentation Questions - Where can I find information about the 2378 AIRS IR channel properties?
A channel-by-channel list which describes all 2378 of the AIRS IR channels can be found at: http://disc.sci.gsfc.nasa.gov/AIRS/documentation - What document gives a description of the AIRS data field attributes (geolocation, swath)?
The document called AIRS Processing Files Description provides a detailed description of the dimensions, geolocation fields, full swath data fields and other attributes. - What are the AIRS Earth Science Data Type (EDST) data collection descriptors?
AIRS ESDT collection descriptors contain all AIRS HDF-EOS metadata attributes (headers) such as version number, data date, spatial coordinates, etc. AIRS ESDTs as well as other platform instrument ESDTs can be found at: The EOS Core System (ECS) Information page: http://ecsinfo.gsfc.nasa.gov/ECSInfo/ecsmetadata/ESDT/ESDT_descriptors.html - Where can I access disclaimers about AIRS data?
Disclaimers document is prepared by the AIRS science team and it can be found at: http://disc.sci.gsfc.nasa.gov/AIRS/documentation - From where can I get the current version of AIRS Level 2 retrieval algorithms?
The source code has not been cleared for public release at this time. The plan is to release the source code in the future, via Direct Broadcast contacts, but no schedule has been established for the release of Level 2 code. If you wish to compare retrieval products, the AIRS project is happy to cooperate and work with you as long as you choose to use actual AIRS data instead of simulation data. | Answers to Data Access Questions - Who can order AIRS data products?
All NASA Earth Observing System (EOS) mission data including AIRS data is freely available to the public. Anyone can order these data products free of charge. - Do I need to register to become a new user?
Registration is not required to obtain AIRS data from GES DISC. On the other hand, the AIRS science team at NASA JPL encourages you to register with them so that you will receive announcements of discovered features and caveats which are directly applicable to your area of research. You will also receive the AIRS Newsletter. - Is AIRS data available via FTP to/from any site?
See our Data Access page for the server names and directory paths. You may also subscribe to the AIRS data so that the data products can be pushed to your site. Please contact User Services to set up FTP push. - Why would there be missing data for certain days?
There are several possible reasons for missing data: The launch of the Aqua satellite that carries the AIRS instrument occurred on May 4, 2002. Processing on AIRS data to be distributed to the public began on data date March 12, 2003. If you are seeking most recent data, it is possible the data is still in the processing pipeline and will soon be available. There is typically a lag from the time instrument observations are made on the satellite until the data is processed and made available to the public. Sometimes satellite maneuvers, other necessary onboard procedures or technical problems will cause gaps in the data collection. Those instances will be documented and found at the NASA JPL AIRS website when appropriate. - Who can I contact for help with ordering AIRS data?
If you need assistance with ordering via GES DISC or WIST, please contact the GES DISC User Service group at 301-614-5224 or send an email to help-disc@listserv.gsfc.nasa.gov GES DISC User Services NASA GSFC Code 610.2 Greenbelt, MD 20771 FAX (301) 614-5268 - How can I find Level 1 and Level 2 granules corresponding to various combinations of time/location?
For many different search combination, below is the command line search against Mirador using Python script. Usage: python mirador_cmd.py < input.txt > urls.txt Sample input file (start, end, lat, long, lat, long) : 2007-01-01T00:00:00 2007-01-01T23:59:59 (-15.8,-69.4),(-15.8,-69.4) where Input file format is start and end are CCSDS format time, yyyy-mm-ddThh:mm:ss start end (lat,long),(lat,long). Once getting urls.txt, type wget -i urls.txt to get all the necessary files "mirador_cmd.py" contains the following. Depending on the data set, one has to change shortname (AIRX2RET below for AIRS Level 2 standard product). #!/usr/local/bin/python import os, sys, urllib, re, string def search_mirador(shortname, begin, end, bbox): url_root = 'http://mirador.gsfc.nasa.gov/cgi-bin/mirador/granlist.pl?' # Maxgranules set low for testing. For ops, set high (e.g. 1000). maxgranules = 1000 params = (url_root, maxgranules, shortname, bbox, begin, end) url='%sformat=rss&maxgranules=%d&dataSet=%s&version=005&location=%s&searchType=Location&startTime=%s&endTime=%s' % params # print url #Sample url = 'http://mirador.gsfc.nasa.gov/cgi-bin/mirador/granlist.pl?format=rss&maxgranules=100&dataSet=AIRIBRAD&version=005&location=(-15.8,-69.4),(-15.8,-69.4)&searchType=Location&event=&startTime=2007-01-01%2000:00:00&endTime=2007-12-31%2023:59:59' # Make HTTP request file=urllib.urlopen(url) lines=file.readlines() file.close() # Parse lines for data URLs pattern = re.compile('<item>.*?<link>(.*?)</link>') for line in lines: mobj = pattern.search(line) # print line if (mobj): print mobj.group(1) shortname='AIRX2RET' for line in sys.stdin.readlines(): (start, end, bbox) = string.split(line) search_mirador(shortname, start, end, bbox) | Answers to AIRS Subsetting Questions - What are the AIRS subset services at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC)?
When you order data through WHOM or Mirador search engine, you can choose variable or channel subsetting on AIRS L1B and L2 products. L3 subsetting can be done in Giovanni. What is "Golden Set of Channels" offered for AIRS channel subsetting services ? These are the groups of channels recommended by the AIRS Science Team for channel subsetting of AIRS L1B and L2 products. See table below. The grouping is generally based on hardware module in the AIRS instrument. The channel number range and the frequency range in addition to module name for each set are also listed to give a better description of each set. These are meant to make it easy for users to select all channels in various frequency ranges. The "comments" in this table are only meant as comments to let users know typical uses for data in this range. For example M-06 has the comment "Ozone". Not all channels in this set are necessarily good for ozone and not all ozone channels are in this set. It is the set of all channels on module 6, and the most prominent feature of this section of the spectrum is ozone sensitivity. One may also note that frequency ranges overlap somewhat between the modules, so frequency ranges can be deceptive. Hardware Module | Frequency Range | Channel Number Range | Number of Channels | Comments | All | 649.61 - 2665.24cm-1 | 1 - 2378 | 323 | The Numerical Weather Prediction sets | M-12 | 649.61 - 681.99cm-1 | 1 - 130 | 130 | Long-wave temperature sounding | M-11 | 687.60 - 728.44cm-1 | 131-274 | 143 | Long-wave temperature sounding | M-10 | 728.06 - 781.88cm-1 | 275 - 441 | 166 | Long-wave surface | M-09 | 789.26 - 852.43cm-1 | 442 - 608 | 166 | Long-wave surface | M-08 | 851.49 - 903.78cm-1 | 609 - 769 | 160 | Long-wave surface | M-07 | 911.24 - 974.29cm-1 | 770 - 936 | 166 | Long-wave surface | M-06 | 973.82 - 1046.20cm-1 | 937 - 1103 | 166 | Ozone | M-05 | 1056.10 - 1136.66cm-1 | 1104 - 1262 | 158 | Long-wave surface, Ozone | M-04d | 1216.97 - 1272.59cm-1 | 1263 - 1368 | 105 | Water vapor | M-04c | 1284.35 - 1338.86cm-1 | 1369 - 1462 | 93 | Water vapor, methane | M-03 | 1338.16 - 1443.07cm-1 | 1463 - 1654 | 191 | Water vapor | M-04b | 1460.27 - 1527.00cm-1 | 1655 - 1760 | 105 | Water vapor | M-04a | 1541.10 - 1613.86cm-1 | 1761 - 1864 | 103 | Water vapor | M-02b | 2181.50 - 2325.06cm-1 | 1865 - 2014 | 149 | Shortwave temperature sounding, CO | M-01b | 2299.80 - 2422.85cm-1 | 2015 - 2144 | 129 | Shortwave temperature sounding | M-02a | 2446.20 - 2569.75cm-1 | 2145 - 2260 | 115 | Shortwave Surface | M-01a | 2541.90 - 2665.24cm-1 | 2261 - 2378 | 117 | Shortwave Surface | - What are the channels contained in the "Numerical Weather Prediction (NWP) Set"?
The NWP set is the set of channels used by Numerical Weather Prediction centers. These channels were selected as key well-behaved channels (as of 2003) that collectively have almost as much information as the full 2378 channel set. Index | Channel Number | Frequency (wavenumber) | 1 | 1 | 649.612976 | 2 | 6 | 650.807007 | 3 | 7 | 651.046021 | 4 | 10 | 651.765015 | 5 | 11 | 652.005005 | 6 | 15 | 652.968018 | 7 | 16 | 653.208984 | 8 | 17 | 653.450012 | 9 | 20 | 654.174988 | 10 | 21 | 654.416992 | 11 | 22 | 654.658997 | 12 | 24 | 655.143982 | 13 | 27 | 655.872986 | 14 | 28 | 656.116028 | 15 | 30 | 656.604004 | 16 | 36 | 658.070007 | 17 | 39 | 658.80603 | 18 | 40 | 659.052002 | 19 | 42 | 659.544006 | 20 | 51 | 661.767029 | 21 | 52 | 662.015015 | 22 | 54 | 662.512024 | 23 | 55 | 662.760986 | 24 | 56 | 663.008972 | 25 | 59 | 663.757019 | 26 | 62 | 664.507019 | 27 | 63 | 664.757019 | 28 | 68 | 666.010986 | 29 | 69 | 666.262024 | 30 | 71 | 666.765991 | 31 | 72 | 667.018005 | 32 | 73 | 667.27002 | 33 | 74 | 667.521973 | 34 | 75 | 667.775024 | 35 | 76 | 668.028015 | 36 | 77 | 668.281006 | 37 | 78 | 668.533997 | 38 | 79 | 668.786987 | 39 | 80 | 669.041016 | 40 | 82 | 669.549011 | 41 | 83 | 669.802979 | 42 | 84 | 670.057983 | 43 | 86 | 670.567017 | 44 | 92 | 672.099976 | 45 | 93 | 672.356995 | 46 | 98 | 673.640991 | 47 | 99 | 673.898987 | 48 | 101 | 674.414001 | 49 | 104 | 675.189026 | 50 | 105 | 675.447998 | 51 | 108 | 676.226013 | 52 | 110 | 676.744995 | 53 | 111 | 677.005005 | 54 | 113 | 677.526001 | 55 | 116 | 678.307983 | 56 | 117 | 678.570007 | 57 | 123 | 680.142029 | 58 | 124 | 680.403992 | 59 | 128 | 681.45697 | 60 | 129 | 681.721008 | 61 | 138 | 689.491028 | 62 | 139 | 689.762024 | 63 | 144 | 691.119019 | 64 | 145 | 691.390991 | 65 | 150 | 692.755005 | 66 | 151 | 693.028992 | 67 | 156 | 694.400024 | 68 | 157 | 694.674011 | 69 | 159 | 695.224976 | 70 | 162 | 696.052002 | 71 | 165 | 696.880981 | 72 | 168 | 697.711975 | 73 | 169 | 697.98999 | 74 | 170 | 698.267029 | 75 | 172 | 698.823975 | 76 | 173 | 699.10199 | 77 | 174 | 699.380981 | 78 | 175 | 699.659973 | 79 | 177 | 700.218018 | 80 | 179 | 700.776978 | 81 | 180 | 701.057007 | 82 | 182 | 701.617981 | 83 | 185 | 702.460999 | 84 | 186 | 702.742004 | 85 | 190 | 703.869995 | 86 | 192 | 704.435974 | 87 | 193 | 704.718994 | 88 | 198 | 706.137024 | 89 | 201 | 706.991028 | 90 | 204 | 707.846985 | 91 | 207 | 708.705994 | 92 | 210 | 709.565979 | 93 | 213 | 710.429016 | 94 | 215 | 711.005005 | 95 | 216 | 711.29303 | 96 | 218 | 711.870972 | 97 | 221 | 712.739014 | 98 | 224 | 713.609009 | 99 | 226 | 714.190979 | 100 | 227 | 714.481995 | 101 | 232 | 715.940979 | 102 | 239 | 717.994019 | 103 | 248 | 720.651001 | 104 | 250 | 721.244019 | 105 | 251 | 721.541016 | 106 | 252 | 721.838013 | 107 | 253 | 722.13501 | 108 | 256 | 723.028992 | 109 | 257 | 723.328003 | 110 | 261 | 724.523987 | 111 | 262 | 724.823975 | 112 | 267 | 726.325989 | 113 | 272 | 727.833984 | 114 | 295 | 734.150024 | 115 | 299 | 735.382019 | 116 | 300 | 735.690002 | 117 | 305 | 737.236023 | 118 | 308 | 738.166992 | 119 | 309 | 738.478027 | 120 | 310 | 738.789001 | 121 | 318 | 741.286011 | 122 | 321 | 742.22699 | 123 | 325 | 743.484985 | 124 | 333 | 746.013977 | 125 | 338 | 747.603027 | 126 | 355 | 753.057007 | 127 | 362 | 755.325012 | 128 | 375 | 759.573975 | 129 | 453 | 793.171021 | 130 | 475 | 801.098999 | 131 | 484 | 804.385986 | 132 | 497 | 809.179993 | 133 | 528 | 820.833984 | 134 | 587 | 843.913025 | 135 | 672 | 871.289001 | 136 | 787 | 917.30603 | 137 | 791 | 918.747009 | 138 | 843 | 937.90802 | 139 | 870 | 948.184021 | 140 | 914 | 965.43103 | 141 | 950 | 979.127991 | 142 | 1003 | 1001.38397 | 143 | 1012 | 1005.263 | 144 | 1019 | 1008.29999 | 145 | 1024 | 1010.48102 | 146 | 1030 | 1013.10901 | 147 | 1038 | 1016.63501 | 148 | 1048 | 1021.07703 | 149 | 1069 | 1030.52795 | 150 | 1079 | 1035.08899 | 151 | 1082 | 1036.46497 | 152 | 1083 | 1036.92395 | 153 | 1088 | 1039.22705 | 154 | 1090 | 1040.151 | 155 | 1092 | 1041.07703 | 156 | 1095 | 1042.46802 | 157 | 1104 | 1056.104 | 158 | 1111 | 1059.44397 | 159 | 1115 | 1061.36096 | 160 | 1116 | 1061.84094 | 161 | 1119 | 1063.28503 | 162 | 1120 | 1063.76697 | 163 | 1123 | 1065.21594 | 164 | 1130 | 1068.60999 | 165 | 1138 | 1072.51501 | 166 | 1142 | 1074.47803 | 167 | 1178 | 1092.45105 | 168 | 1199 | 1103.19897 | 169 | 1206 | 1106.82605 | 170 | 1221 | 1114.67505 | 171 | 1237 | 1123.16199 | 172 | 1252 | 1131.229 | 173 | 1260 | 1135.57495 | 174 | 1263 | 1216.974 | 175 | 1266 | 1218.49597 | 176 | 1278 | 1224.62305 | 177 | 1285 | 1228.22498 | 178 | 1290 | 1230.81104 | 179 | 1301 | 1236.53894 | 180 | 1304 | 1238.10999 | 181 | 1329 | 1251.35706 | 182 | 1371 | 1285.47498 | 183 | 1382 | 1291.70898 | 184 | 1400 | 1302.03699 | 185 | 1401 | 1302.61499 | 186 | 1402 | 1303.19397 | 187 | 1403 | 1303.77295 | 188 | 1415 | 1310.76599 | 189 | 1424 | 1316.05798 | 190 | 1449 | 1330.97595 | 191 | 1455 | 1334.60498 | 192 | 1466 | 1339.68701 | 193 | 1471 | 1342.23804 | 194 | 1477 | 1345.31201 | 195 | 1479 | 1346.34094 | 196 | 1488 | 1350.98804 | 197 | 1500 | 1357.23596 | 198 | 1519 | 1367.25305 | 199 | 1520 | 1367.78503 | 200 | 1538 | 1377.42603 | 201 | 1545 | 1381.21301 | 202 | 1565 | 1392.15295 | 203 | 1574 | 1397.13501 | 204 | 1583 | 1402.15295 | 205 | 1593 | 1407.77295 | 206 | 1614 | 1419.72595 | 207 | 1627 | 1427.229 | 208 | 1636 | 1432.47095 | 209 | 1644 | 1437.16394 | 210 | 1652 | 1441.88794 | 211 | 1669 | 1468.82703 | 212 | 1674 | 1471.91003 | 213 | 1681 | 1476.24695 | 214 | 1694 | 1484.36902 | 215 | 1708 | 1493.21497 | 216 | 1717 | 1498.95801 | 217 | 1723 | 1502.81006 | 218 | 1740 | 1513.83203 | 219 | 1748 | 1519.07397 | 220 | 1751 | 1521.04895 | 221 | 1756 | 1524.35205 | 222 | 1763 | 1542.44897 | 223 | 1766 | 1544.48206 | 224 | 1771 | 1547.88196 | 225 | 1777 | 1551.98096 | 226 | 1780 | 1554.03796 | 227 | 1783 | 1556.10095 | 228 | 1794 | 1563.70898 | 229 | 1800 | 1567.89001 | 230 | 1803 | 1569.98901 | 231 | 1806 | 1572.09204 | 232 | 1812 | 1576.31702 | 233 | 1826 | 1586.25903 | 234 | 1843 | 1598.495 | 235 | 1852 | 1605.04602 | 236 | 1865 | 2181.49512 | 237 | 1866 | 2182.3999 | 238 | 1867 | 2183.30688 | 239 | 1868 | 2184.21411 | 240 | 1869 | 2185.12207 | 241 | 1872 | 2187.8501 | 242 | 1873 | 2188.76099 | 243 | 1875 | 2190.58496 | 244 | 1876 | 2191.49805 | 245 | 1877 | 2192.41211 | 246 | 1881 | 2196.07495 | 247 | 1882 | 2196.99292 | 248 | 1883 | 2197.91089 | 249 | 1884 | 2198.83008 | 250 | 1897 | 2210.8479 | 251 | 1901 | 2214.57202 | 252 | 1911 | 2223.93604 | 253 | 1917 | 2229.59204 | 254 | 1918 | 2230.53711 | 255 | 1921 | 2233.37695 | 256 | 1923 | 2235.2749 | 257 | 1924 | 2236.2251 | 258 | 1928 | 2240.03296 | 259 | 1937 | 2248.64795 | 260 | 1938 | 2249.60889 | 261 | 1939 | 2250.57104 | 262 | 1941 | 2252.49707 | 263 | 1946 | 2257.3269 | 264 | 1947 | 2258.29492 | 265 | 1948 | 2259.26392 | 266 | 1958 | 2269.00098 | 267 | 1971 | 2281.78101 | 268 | 1973 | 2283.75903 | 269 | 1988 | 2298.70508 | 270 | 1995 | 2305.7439 | 271 | 2084 | 2363.98389 | 272 | 2085 | 2364.94092 | 273 | 2097 | 2376.48999 | 274 | 2098 | 2377.45801 | 275 | 2099 | 2378.42603 | 276 | 2100 | 2379.39502 | 277 | 2101 | 2380.36499 | 278 | 2103 | 2382.30811 | 279 | 2104 | 2383.28003 | 280 | 2106 | 2385.22705 | 281 | 2107 | 2386.2019 | 282 | 2108 | 2387.17798 | 283 | 2109 | 2388.15405 | 284 | 2110 | 2389.13208 | 285 | 2111 | 2390.11011 | 286 | 2112 | 2391.08911 | 287 | 2113 | 2392.06812 | 288 | 2114 | 2393.04907 | 289 | 2115 | 2394.03003 | 290 | 2116 | 2395.01196 | 291 | 2117 | 2395.99512 | 292 | 2118 | 2396.979 | 293 | 2119 | 2397.96411 | 294 | 2120 | 2398.94897 | 295 | 2121 | 2399.93604 | 296 | 2122 | 2400.9231 | 297 | 2123 | 2401.91089 | 298 | 2128 | 2406.86304 | 299 | 2134 | 2412.83203 | 300 | 2141 | 2419.83496 | 301 | 2145 | 2446.19507 | 302 | 2149 | 2450.2981 | 303 | 2153 | 2454.41406 | 304 | 2164 | 2465.80396 | 305 | 2189 | 2492.0791 | 306 | 2197 | 2500.60205 | 307 | 2209 | 2513.49292 | 308 | 2226 | 2531.97803 | 309 | 2234 | 2540.76904 | 310 | 2280 | 2561.12891 | 311 | 2318 | 2600.49902 | 312 | 2321 | 2603.65991 | 313 | 2325 | 2607.88696 | 314 | 2328 | 2611.06592 | 315 | 2333 | 2616.38306 | 316 | 2339 | 2622.79199 | 317 | 2348 | 2632.46606 | 318 | 2353 | 2637.87207 | 319 | 2355 | 2640.04102 | 320 | 2363 | 2648.75195 | 321 | 2370 | 2656.4231 | 322 | 2371 | 2657.52197 | 323 | 2377 | 2664.13794 | | Answers to AIRS Imagery Questions - Where can I get browse images of AIRS data? Do the images cost anything?
AIRS Daily summary browse images can be viewed through AIRS summary browse search option in GES DAAC Search and Order. The AIRS summary browse data is used as only ordering tool and cannot be distributed to public users as a data product. Starting from Version 5, the summary browse images are discontinued. All browse images SHOULD NOT be used as the basis of any science research and do not constitute a research-quality product. The images are available at NO COST. - What purpose do browse images serve?
Browse images are low-resolution visualizations used in search and order tools. The purpose of having browse images is to allow science data users to get an idea about what is in the data before ordering the data. For example, users should be able to tell if a location they have selected is sufficiently cloud-free or cloudy enough for cloud studies. In other words, the browse images have a role in helping users to select and organize the science data they have obtained. - Why should I take time to preview an image?
In the GES DISC Search and Order interface (Mirador), there is an option to preview a data granule before ordering the data granule. Previewing an image of the data can help to determine the extent and location of cloud cover, confirm its geographical location, or observe quality problems such as speckling, line drops, and sun glint. However, this is not to be confused with our AIRS summary browse image which is a daily product (i.e., some anomalies may not be visible on a summary browse image due to the sub-sampling process). - Can I use the browse image for research and analysis purposes?
No. Browse images represent only a fraction of the original data or have a low-resolution. They should not be used for analysis, evaluation or interpretation of data content. - What is the volume of a browse image?
The size of the browse images for L1B products are less than 200 kilobytes with most ranging from 100 to 150 kilobytes. | Answer to Science Questions - What is the repeat cycle of AIRS?
The AIRS swath repeat cycle is 16 days. - What is the vertical resolution of AIRS Level-2 products?
Standard product is on 28 pressure levels and Support product is on 100 pressure levels. Complete lists of those levels can be found at http://disc.sci.gsfc.nasa.gov/AIRS/documentation, under Level-2 Products section (Pressure Arrays). The documentation on AIRS Levels and Layers is also useful and can be found at the same web location. - What is cloud-clearing method?
The cloud-clearing approach is used to retrieve atmospheric and surface properties. It relies on the fact that cloud amount tends to vary appreciably among nearby 15 km AIRS footprints, but that other atmospheric and cloud properties (averaged within AIRS footprints) are more uniform. This means that radiance differences between adjacent AIRS footprints are primarily caused by changes in cloud amount. Adjacent, multi-spectral observations can then be solved in a least squares sense for the infrared radiance that is common to the clear portions of all field of view. Since the effect of clouds has been removed, atmospheric and surface variables can be retrieved from these radiances as if no clouds were present. Cloud properties can be also determined based on the difference between observed and cloud-cleared radiances. In this technique, any aerosols that interact with IR radiation can be treated as an unusual cloud layer. As with water clouds, there must be a clear region somewhere within each AMSU-A footprint. Thus, narrow smoke plumes are not a problem, but a uniform dust layer extending more than 45 km across would get folded into the "clear-column" radiances and could degrade the atmospheric retrieval. To assess the impact of such horizontally widespread aerosols, it should be noted that stratospheric sulfuric acid aerosols are optically thin in the IR, except after large volcanic eruptions. Tropospheric anthropogenic aerosols are also optically thin to AIRS because of their small size. Although this method has been used and proved by existing systems (TOVS), it should be noticed that the higher spectral resolution of AIRS allows this technique to be exploited to a higher degree than ever before. - Does AIRS Level-2 product include measurements from AMSU and HSB?
One flavor of the AIRS Level-2 Standard and Support Products does. Their product names are AIRH2RET and AIRH2SUP respectively. The end date for these products is 2003-Feb-05 due to HSB instrument failure. The Standard Product (AIRX2RET) and Support Product (AIRX2SUP) are careated using only the AIRS and AMSU, without HSB. - Can radiance value be negative?
In general, AIRS can have negative radiances for shortwave channels. When the scene temperature is low, below 200K, shortwave AIRS channels can have negative radiances. This happens over very high cloud in tropics and over Antartica. In bad channels, radiance can be negative for several different reasons: 1) -9999.0 is used as a flag value when input data is missing or out of range. Out of range data happens most frequently as a result of sun glint causing saturation. 2) Radiances can go negative when the noise is greater than the scene. This will happen in very noisy detectors (so users should check the channel properties file and/or the ExcludedChans field in the data. Note ExcludedChans is not defined correctly in the docs. Any channel with a value 3 or higher should be ignored. NeN is also a good diagnostic of channels experiencing transient high noise episodes.) The users should be warned to use only the channels that are marked good ( BadFlag = 0 in the channel property file.). - Where can I find AIRS-RTA?
You can find AIRS-RTA in AIRS Level-2 ATBD, http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/AIRS/atbd-airs-L2.pdf Section 4.2 Radiative Transfer of the Atmospheric in the Infrared. - Where can I find AIRS band chart?
AIRS band chart can be found in AIRS channel properties files: http://disc.sci.gsfc.nasa.gov/AIRS/documentation under Level-1B Products section. - How can I find when AIRS is over a particular area?
Various maps of the orbital tracks of Aqua (the satellite carrying AIRS) are available from University of Wisconsin's web site: http://www.ssec.wisc.edu/datacenter/aqua/ |
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