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The MODIS Atmosphere Group develops remote sensing algorithms for deriving parameters pertaining to atmospheric properties of the Earth. In order to develop conceptual and predictive global models, it is important to monitor these properties. Two MODIS (Moderate Resolution Imaging Spectroradiometer) instruments, the first launched on 18 December 1999 onboard the Terra Platform and the second on 4 May 2002 onboard the Aqua platform, are uniquely designed (wide spectral range, high spatial resolution, and near daily global coverage) to observe and monitor these and other Earth conditions.


Feature L1B Granule Image

  Armageddon-like Dust Storm

MODIS/Terra 9/23/09 00:05 UTC Dawn breaks over Sydney 9/23/09 click images to zoom

In September 2009, a record-breaking dust storm swept across the Australian states of New South Wales and Queensland. By 24 September, analysis using MODIS at NASA measured the length of the huge dust plume at 3,450 km. Dust particle concentration levels reached 15,400 micrograms per cubic meter of air. (Normal days register up to 20 micrograms and bushfires generate 500 micrograms.) It was estimated that the storm carried some 16 million tons of dust from the deserts of Central Australia. During the peak of the storm, the Australian continent was estimated to be losing 75,000 tons of dust per hour off the New South Wales coast north of Sydney. While the cloud was visible from space, on the ground the intense red-orange color and drop in temperature drew comparisons with nuclear winter (Armageddon), as well as the planet Mars. Some of the thousands of tons of soil lifted in the dust storm were dumped in Sydney Harbour and the Tasman Sea. This increased the nitrogen and phosphate levels in the water significantly. Measurements taken two weeks after the event indicated an explosion of microscopic plant life which led to an increase in fish population some months later.   (Source: Wikipedia.org)   Additional MODIS RGB images can be viewed in the L1B Granules section.

Frequently Asked Questions   (Quick Start Guide)


   What are MODIS Data "Collections"?

A MODIS data "Collection" is basically a MODIS data version. When new & improved science algorithms are developed, the entire MODIS dataset (from launch) is reprocessed and then tagged & distributed as a new "Collection". During the processing of a Collection, an attempt is made to use the same version of the Science Algorithms or Program Executables (PGEs). However, sometimes a bug is found in one or more of the PGEs in the middle of Collection processing; and if the bug is not serious, processing will complete with the new corrected PGE. These anomalies and problems in processing are noted on the Known Problems page. One can always identify the Collection number for a particular HDF file as it's always included (as a 3 digit number) as part of the HDF filename. There have been six MODIS data Collections (or Versions) processed since MODIS/Terra was launched in early 2000. The Collection versions created thus far are 001, 003, 004, 005, 051, and 006. It should be noted that Collection 051 only contained updates for some MODIS Data Products, which is why it was tagged with a 051 (a surrogate for version 5.1), since it was considered only a partial update of MODIS Data Products. Finally, changes for the next Collection (006) are for the most part completed. Processing and availability of Collection 006 data is progressing and not complete. Documents have been generated that outline the changes and improvements offered in each Collection:

  Collection 006 Change Summary (newly released collection, processing)
  Collection 051 Change Summary (last completed collection)

   How can I stay apprised of MODIS Data availability?

A MODIS Data Processing & Availability Calendar is available that shows the latest Collection and PGE version for each MODIS Data Product on a month by month basis. As of early 2014, a combination of Collection 006 and Collection 051 is the latest available for MODIS Atmosphere Data Products.

It should be noted that the MODIS data record began in March 2000 for Terra (10:30 LST nomimal daytime overpass) and July 2002 for Aqua (13:30 LST nominal daytime overpass). Finally, note that MODIS Terra HDF files always begin with the prefix "MOD", while MODIS Aqua HDF files always begin with the prefix "MYD".

  MODIS Data Processing & Availability Calendar

   How do I order MODIS Data?

MODIS Data is distributed free of charge through the Level 1 and Atmosphere Archive and Distribution System (LAADS). By utilizing the Search & Order Tool on the LAADS web site, one can search and subset data by collection, date & time, geographic area, science products, and selected metadata.

  Search & Order MODIS Data (LAADS web site)


It should be noted that LAADS web site searches (link above) are limited to 2000 files; so you may need to limit the time period or spatial coordinates to complete a search successfully. If you don't want to limit either field, you can go directly to the LAADS FTP site to download data (see links below). You will need to scroll down a bit in the FTP page to find the directories that start with "MOD" (for MODIS Terra HDF data) or "MYD" (for MODIS Aqua HDF data). The FTP directories that start with "MOB" or "MYB" contain Terra or Aqua browse images.

  FTP Download Collection 006 MODIS Data (LAADS ftp site)
  FTP Download Collection 051 MODIS Data (LAADS ftp site)

   How do I read, interpret, or visualize MODIS Data?

MODIS Data is stored in Heirarchical Data Format (HDF). There are a number of tools and programs already written to read and visualize MODIS data. These include GUI, web-based, and command line programs that are written in IDL, FORTRAN, and C. Many of these are distributed in our TOOLS section:

  MODIS Data Tools (for reading & visualizing)

Users that wish to unpack Level-2 (L2) Orbital Granule MODIS data (at 1km, 5km, or 10km resolution) are advised to become familiar with the MODIS QA Plan; which details how to read, as well as the content of the Level-2 QA arrays. These QA arrays contain bit-flags that detail input data source, processing path, quality, as well as detailed characteristics and properties of Level-2 retrievals. Also available on the page linked below are Algorithm Theoretical Basis Documents (ATBDs) for MODIS Data Products. These ATBDs provide the scientific background of MODIS data.

  QA Plan & ATBDs (L2 QA Flags & Science Basis)

Users working with Level-3 (L3) Daily, Eight-day, or Monthly Global Gridded MODIS data (at 1 degree resolution) are advised to become familiar with the Level-3 Algorithm Theoretical Basis Document. This document details characteristics, properties, and content of Level-3 data. Also included in this document are user caveats and frequently asked questions. The L3 ATBD is linked on the above 'QA Plan & ATBDs' page, as well as individual 'Theoretical Basis' pages in the L3 product sections. The link for the 'Theoretical Basis' page in the L3 Monthly product section is provided below. It should be noted that there is only one L3 ATBD for all L3 products (Daily, Eight-day, & Monthly).

  L3 ATBD (L3 primer)

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Last Updated: Tuesday, 24-January-2017   8:00 AM EST