MODIS Atmosphere

You have accessed a U.S. Government Computer System. Visitors are authorized to use this system to acquire MODIS-Atmosphere related data information, images, products, and services only. Access to this system constitutes visitors consent to keystroke monitoring. Any malicious action or intent on this system is prohibited and punishable under Federal Law. Privacy Policy and Important Notices

Overview

One of the most important ecological issues concerning our planet is climate change. It is generally agreed that the Earth's climate will modify in response to radiative forcing induced by changes in atmospheric trace gases, cloud cover, cloud type, solar radiation, and tropospheric aerosols (liquid or solid particles suspended in the air). In order to develop conceptual and predictive global climate models, it is vital 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 changes.

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 part of the HDF filename. There have been five 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, and 051. 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 under development. Processing and availability of Collection 006 data is not expected until late Spring 2013. Documents have been generated that outline the changes and improvements offered in each Collection:

Collection 006 Change Summary (future collection, under development)
Collection 051 Change Summary (most recent collection)
Collection 005 Change Summary (previous 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 2011, a combination of Collection 051 and Collection 005 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 051 MODIS Data (LAADS ftp site)
FTP Download Collection 005 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)

SECURITY WARNING PRIVACY STATEMENT ACCESSIBILITY STATEMENT
Last Updated: Saturday, 13-April-2013 11:30 AM EDT

Spotlight

MODIS Aqua Cloud Mask (MYD35_L2) and Atmospheric Profile (MYD07_L2) products have been updated with Collection 6 algorithms - Cloud Mask updates include (see details) use of NDVI background maps to fine-tune classifications over desert and vegetated surfaces. The C6 product adds a "cloud adjacency flag" and adjusts night classifications to use thresholds based on total precipitable water. The new product better detects transmissive cirrus and reduces "probably cloudy" retrievals in very humid tropical conditions. Thick smoke and aerosols are also better distinguished from cloud by the new algorithm. Atmospheric Profile updates include (see details) use of a new layer scheme for total precipitable water and application of spectral shifts with some reduction in biases seen in dry atmospheres. Spectral adjustments and new radiative transfer modeling have improved Total Ozone retrieval comparisons against OMI and surface measurements. [DETAILS]

Collection 006 Documentation - The documents linked on the page below (at the bottom of hte page) describes Collection 006 changes to all L2 and L3 MODIS data. This next generation of MODIS data products (C006) is expected to began production late Spring 2013. [DETAILS]

MODIS Atmosphere QA Plan for Collection 005 & 051 Corrected - An updated version (v3.10, 12 Jan 2012) of the MODIS Atmosphere Quality Assurance (QA) Plan is available. This plan contains corrections to the to the Cloud Mask Quality_Assurance Bit Flags listed on pages 32-35. [VIEW]

Notice to Terra Data Users - The reflective solar bands (RSB) of Terra MODIS have experienced relatively large degradation in recent years. The current calibration algorithm used in deriving the Collection 5 LUTS does not completely capture and correct for this degradation, which is both wavelength and angle-of-incidence dependent. Science data products that utilize the shorter wavelength bands, especially Bands 8 (412 nm), 9 (443 nm) and 3 (469 nm), can expect to see an observable impact in data quality. The proposed calibration algorithm improvements in development for Collection 6 LUTs are expected to significantly reduce these impacts. These LUTs will be put into production after a thorough review and testing process is completed. [MCST STATEMENT]

Near Real-time Hi-Res L1 & L2 Mosaics - View near-real time mosaic images of MODIS granules from either the Terra (February 2000 to current) or Aqua (June 2002 to current) platforms. [HI-RES MOSAICS]

MODIS Cloud Mask User's Guide - This MODIS Cloud Mask User's Guide was written by Kathy Strabela (UW) in 2008. [Cloud Mask Users Guide]

Error Found in Terra Collection 051 Data - An error involving incorrect Clear Sky Radiances was found in the Collection 051 Terra reprocessing in HDF files with data dates prior to April 1, 2010 (2010 091). The error impacted all Cloud-related (Cloud Top and Cloud Optical Property) SDSs. Since this error was found, all Terra C051 data has been correctly reprocessed and updated HDF files are available for download. However the bad C051 was distributed to users prior to September 2010. Users of Collection 051 should make sure they did not acquire bad C051 data by following the link below, which tells you how to identify bad data. If you acquired bad data, you should redownload the corrected data. [IDENTIFICATION DETAILS & IMAGES]

Terra Collection 051 L2 Data Available - Collection 051 Terra processing began in late March 2010. Forward stream Terra C051 products are available starting with data day of April 1st, 2010 Users should note that the Deep Blue Aerosol SDSs will not be populated for data days after January 1st, 2008. LAADS Web is the web interface to the Level-1 and Atmosphere Archive and Distribution System (LAADS). The mission of LAADS is to provide quick and easy access to MODIS Level-1 and Atmosphere data products. Through this interface, one can visually browse MODIS atmosphere products, selected products may then be downloaded directly from the website or retrieved from the FTP site. [LADSWEB]

L3 Algorithm Theoretical Basis Document - A MODIS Atmosphere Level 3 ATBD is now available. This document describes the theoretical basis of MODIS Atmosphere Level 3 (L3) products. Topics covered include computational approaches and scenarios, subsampling and gridding characteristics and caveats, the impact of Level 2 (L2) confidence flags on L3, and finally a breakdown of the parameters and statistics computed in L3. [L3 ATBD]

MODIS Online Visualization and Analysis System (Giovanni MOVAS) - This new and powerful web-based MODIS data analysis tool is designed for visualization and analysis of the Terra / MODIS Level-3 Atmosphere Monthly global product (MOD08_M3). Users can plot area average (area plot) and time series (time plot) or generate ASCII output for selected area and time period. Spatial coverage is 90°N - 90°S, spatial resolution is 1° x 1°, and temporal resolution is monthly. [MORE]

Near Real-time MODIS L1B Images - View near-real time RGB mapped images of all daytime MODIS granules from either the Terra (February 2000 to current) or Aqua (June 2002 to current) platforms. [TERRA] [AQUA]

Near Real-time Monthly Global Images - View monthly global images of the full set of L3 MODIS Atmosphere products from either the Terra (March 2000 to current) or Aqua (July 2002 to current) platforms. [TERRA] [AQUA]