# Presentation: 531432

## MODIS DATA WORKSHOPUnderstanding and Accessing MODIS Atmosphere ProductsISRO-NASA MODIS Workshop

- Rich Kleidman   Science Systems and Applications
- Rob Levy            Science Systems and Applications
- Lorraine Remer  NASA Goddard Space Flight Center
- Shana Mattoo,, Alan Chu, Vanderlei Martins, Rong-Rong Li, and Yoram Kaufman

## Outline:

- Organization of MODIS Atmosphere Products
- Finding and Ordering Data (Review)
- Detailed Examination of the Atmosphere Data Products
- Visualizing and Analyzing the Data

## Always remember your friends.http://modis-atmos.gsfc.nasa.govThe most important resource for all informationconcerning MODIS atmosphere products.

- But First:

## Organization of the MODIS DATA   MOD - Terra product   MYD - Aqua product   Granule - A 5 minute piece of a MODIS orbitLevel 1 Products (granule)      Level II Products (granule)    Level III Products (global)      

- Geophysical parameter derived from MODIS radiances

- Organization of the MODIS DATA   MOD - Terra product   MYD - Aqua product   Granule - A 5 minute piece of a MODIS orbitLevel 1 Products (granule)      Level II Products (granule)    Level III Products (global)

- MOD02  Level 1B Calibrated geolocated radiancesMOD03  1Km Geolocation Fields

- And now back to our show:

## Level II Products (5 minute granules) Aqua (MYD) products are currently collection 5.  They will   be reprocessed to collection 5.1 beginning in May Terra (MOD) products are collection 5.  Reprocessing to    collection 5.1 will begin after Terra is completed. Collection refers to a coherent grouping of the data.  A collection is usually processed by the same set of algorithms  Changes from one collection to another are totally separate from issues having to due with calibration of the instrument.Reprocessing: Applying the same set of algorithms to the wholedata set.Forward Processing: Applying the current algorithm to newlyacquired data.

## MOD04   Aerosol MOD06   CloudMOD05   Water VaporMOD07   Atmosphere ProfileMOD35   Cloud Mask

- MODIS LEVEL II Product List

## MODIS Level II Products

- MOD04   Aerosol
- The Aerosol Product monitors aerosol type, aerosol optical thickness, particle size distribution, aerosol mass concentration, optical properties, and radiative forcing.
- MOD06   Cloud
- The Cloud Product monitors the physical and radiative properties of clouds including cloud particle phase (ice vs. water, clouds vs. snow), effective cloud particle radius, cloud optical thickness, cloud shadow effects, cloud top temperature, cloud top height, effective emissivity, cloud phase (ice vs. water, opaque vs. non-opaque), and cloud fraction under both daytime and nighttime conditions.
- MOD05   Water Vapor
- The Water Vapor Product monitors atmospheric water vapor and precipitable water.
- MOD07   Atmosphere Profile
- The Atmosphere Profile Product monitors profiles of atmospheric temperature and moisture, atmospheric stability, and total ozone burden.
- MOD35   Cloud Mask
- The Cloud Mask Product indicates whether a given instrument field of view (FOV) of the Earth's surface is unobstructed by clouds or affected by cloud shadows. The cloud mask also provides additional information about the FOV including the presence of: cirrus clouds, ice/snow, and sunglint contamination. Finally flags denoting day/night and land/water are included.

- _[http://modis-atmos.gsfc.nasa.gov/products](http://modis-atmos.gsfc.nasa.gov/products)_

## MOD04           MODIS AEROSOL PRODUCTS         MYD04Important Points to Remember for MODIS Aerosol Products- Ocean and Land Products are produced using totally separateand distinct algorithms.  All current aerosol products are in 10Km (10 x 10) resolution.- The most important products are aerosol optical depth and fine fraction.- There have been major changes and improvements made with collection 5 most significantly to the land algorithm.- Fine fraction over land should be seen as a qualitative     indicator not as a quantitative measurement.

## Formatting of MODIS products

- All MODIS products come in HDF format.
- In HDF format each file contains both data and metadata
- SDS - Each parameter within a MODIS HDF file is referred to as an SDS
- (Scientific Data Set)
- An SDS must be referenced precisely according to name when analyzing the data
- with your own computer code.

## MOD04   Aerosol Products

- Main Products - Ocean
- Effective_Optical_Depth_Average_Ocean
- Retrieved AOD at  .47, .55, .66, .86, 1.24, ***1.63***, 2.13
- Optical_Depth_Ratio_Small_Ocean_0.55*
- Fraction of Fine Mode AOD at 0.55
- Optical_Depth_Small_Average_Ocean
- AOD * Fine Mode Ratio

## A First Look at the DATAHDFLook and MOD04 Products

## HDFLook               A free tool for easy visualization and simple analysis of MODIS products.Display Capabilities   Display images    Display valuesGraphing Capabilities   Plot Transect    Plot HistogramTasks can be scriptedMore complex analysis can be done with Msphinx, Mgraph (also free) or commercial products like IDL, Matlab etc.

- _[http://modis-atmos.gsfc.nasa.gov/tools.html](http://modis-atmos.gsfc.nasa.gov/products)_

## MOD04 SDS and What They Really Mean

- Land or Ocean separately is preferred because
-          - it contains more wavelengths
-          - gives more information about quality
-          - at level 3 it gives a quality weighted product that screens
-              out anomolies
- Land_And_Ocean  Useful if you need both together and may not
-                                 give the same results as Land or Ocean

- Land_And_Ocean  vs Land or Ocean

- Average_Ocean  vs  Best_Ocean

## The Satellite Signal is complicated

**Assumptions**
- Aerosol physics: size, optical properties
- Radiative Transfer (including Rayleigh and wavelength)
- Surface Properties
- Retrieval Math

- (not to mention cloud masking, pixel selection, etc)

## Radius (μm)

- MODIS aerosol retrieval over ocean

- Find one coarse mode and
-   one fine mode
-     that combine to match the
-       observed spectral reflectances

## Although there is usually a unique best solution to the MODIS ocean

- retrieval algorithm there may be many solutions within acceptable
- error limits.  These solutions are used to obtain the
- Average_Ocean SDS results.
- For all practical purposes our group at NASA Goddard uses the
- Average_Ocean SDS rather than Best_Ocean

## MOD04 SDS and What They Really Mean

- Land or Ocean separately is preferred because
-          - it contains more wavelengths
-          - gives more information about quality
-          - at level 3 it gives a quality weighted product that screens
-              out anomolies
- Land_And_Ocean  Useful if you need both together and may not
-                                 give the same results as Land or Ocean

- Land_And_Ocean  vs Land or Ocean

## Corrected_Optical_Depth_Land

- Optical_Depth_Land_and_Ocean

- Image_Optical_Depth_Land_and_Ocean

## MOD04 SDS and What They Really Mean

- Land or Ocean separately is preferred because
-          - it contains more wavelengths
-          - gives more information about quality
-          - at level 3 it gives a quality weighted product that screens
-              out anomolies
- Land_And_Ocean  Useful if you need both together and may not
-                                 give the same results as Land or Ocean

- Land_And_Ocean  vs Land or Ocean

- Average_Ocean  vs  Best_Ocean
- Average_Ocean  is the average of all solutions to the AOT retrieval algorithm having results within acceptable error limits.
- Best_Ocean is the single best solution to the AOT retrieval algorithm
- There are several SDS results that have two dimensions one corresponding to the average solution and one correponding to the best solution.

## Retrieval information

**NEW (c005)**
- Aerosol information at 2.1 m
- Inversion of 3channels yields  (fine aerosol weighting) and s (surface reflectance)
- Retrieved at 0.55 m

- Spectral reflectance of different aerosol

**OLD (c004)**
- No aerosol at 2.1 m
- 2.1 for surface only
- Independent retrievals at 0.47 and 0.66 m
- Interpolated to 0.55 m

## Retrieval: The Inversion

- Coarse

- Fine

- Radius (μm)

- wavelength

- reflectance

- Calculate amount and weighting of fine-dominated model (to total ), combined with the surface reflectance s, that best matches the observed spectral reflectance (0.47, 0.66 and 2.1m)

- Ghosts from L. Remer

- coarse

- surface

- fine

- combo

- 0.55 m

## MOD04   Aerosol Products

- Main Products - Land
- Corrected_Optical_Depth_Land
- Retrieved AOD at  .47, .55, and .66
- Optical_Depth_Ratio_Small_Land
- Fraction of Fine Mode Aerosol
- Not reported for AOD < 0.2
- Optical_Depth_Small_Land
- AOD * Fine Mode Ratio
- (may be a threshold)

- A Qualitative Product Only!

## MOD04   Aerosol Products    Additional SDS

- Optical_Depth_Large_Average_Ocean
- (1 - Fine Fraction) * AOD   for the 7 ocean wavelenghts
- Mass_Concentration_Ocean*
- Mass_Concentration_Land
- Total column mass per unit area in units of 1.0e-6g/cm2
- Angstrom_Exponent_Land
- Ratio of .47/.66     This product does not compare well with Aeronet
- Angstrom_Exponent_1_Ocean*  0.55/0.86
- Angstrom_Exponent_2_Ocean*  0.86/2.1
- Optical_Depth_by_models_ocean
- Retrieval AOT per model.  This information is carried into the level 3 products.
- Effective_Radius_Ocean
- Effective Radius at 0.55 for both the fine and coarse modes.

## Level 3 - Where all atmospheric products come together

- _[http:](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[//modis](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[.](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[gsfc](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[.](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[nasa](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[.gov/data/dataprod/pdf/MOD_08.](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)__[pdf](http://modis.gsfc.nasa.gov/data/dataprod/pdf/MOD_08.pdf)_

- 1 degree resolution, so products are averaged from
- their native retrieval resolution.
- Averaging is either straightforward or weighted by
- QA flag.
- Daily
- 8-Day
- Monthly averages available.

- Note that one grid square can contain multiple orbits.
- Level 3 is not synchronous in time!

## Daily L3 aerosol optical thickness over land and ocean

- Note the gaps between orbits, the gaps over ocean due to
- Sunglint, the gaps over land due to bright surfaces and
- the gaps due to cloud systems.

## The standard MODIS aerosol LAND algorithm

-  relies on finding dark targets.
- For this reason it is unable to make retrievals over bright
- surfaces such as deserts.
- To correct this problem a new algorithm called
- “Deep Blue” was developed.
- Deep Blue relies on the blue wavelengths and libraries
- of surface reflectance to make retrievals in these areas.

## Daily Level 3

- MOD08_D3

- Cloud optical thickness

- Cloud top
- pressure

- Gaps due to
- No clouds

## Cloud optical

- Properties
- Come with an
- Estimate of the
- Errors for each
- retrieval

## Daily

- 8 day

- monthly

- Daily = MOD08_D3
- 8-day = MOD08_E3
- Monthly =MOD08_M3

## Level 3

- Also comes with an array of statistics:
- Means, standard deviations, max and min retrieval
-    in each grid box.
- Histograms and joint histograms between products.
- Number of pixels that went into the mean of
-    each grid box

## http://www.mcst.ssai.biz/mcstweb/L1B/product.html

- _[http://www.](http://www.mcst.ssai.biz/mcstweb/L1B/product.html)__[mcst](http://www.mcst.ssai.biz/mcstweb/L1B/product.html)__[.](http://www.mcst.ssai.biz/mcstweb/L1B/product.html)__[ssai](http://www.mcst.ssai.biz/mcstweb/L1B/product.html)__[.biz/mcstweb/L1B/product.html](http://www.mcst.ssai.biz/mcstweb/L1B/product.html)_

- Level 1 Products

## Level 1 Products   MOD021KM - 1KM calibrated georeferenced radiances    MOD02HKM - .5 KM calibrated georeferenced radiances	   Bands                Nm             Name  	       3		459-479          .47	                         4	             545-565          .55     	        5	           1230-1250       1.2                     6	           1628-1652       1.6	        7	           2105-2155       2.1    MOD02QK -   .25 KM calibrated georeferenced radiances               Bands                Nm             Name                      1		620-660           .66                  2                841-876          .87       http://www.mcst.ssai.biz/mcstweb/L1B/product.html

## *MODIS  Reflected Solar Bands* 

- Keep this page nearby for ready reference !

## A First Look at the DATAHDFLook and MOD02, MYD02 ProductsHDFLook,  Msphinx and Mgraphhttp://www-loa.univ-lille1.fr/Hdflook/http://www-loa.univ-lille1.fr/Msphinx/index.htmlhttp://www-loa.univ-lille1.fr/Mgraph/mgraphE.html

## ALWAYS CHECK YOUR DATA VISUALLY!

- AQUA Reprojected Granule

- Terra Reprojected Granule

- Flight
- Direction
- of the
- Overpass
- Gives a
- “Tilt” to the reprojected
- granule

- ~10:30 Local Time

- ~1:30 Local Time

- Unreprojected “raw” granules come as rectangles

## Things to remember from HDFLookFreeEasy to use for quick visualizationIt really has two separate visualization streams:1) Reprojected Images2) SDS visualizationHDFLook, Mgraph and Msphinx become very powerful tools whenused with scripts.MODIS, AIRS, ASTER, CERES can all be analyzed with MsphinxSee http://www-loa.univ-lille1.fr/Hdflook/ for step by step examples of how to use these tools with scripts

## How to Find and Order MODIS Data

- Some new friends:
- The MODIS Rapid Response Site
- For visually finding MODIS images and related data
- _[http://rapidfire.sci.gsfc.nasa.gov/](http://rapidfire.sci.gsfc.nasa.gov/)_
- http://rapidfire.sci.gsfc.nasa.gov/subsets/
- Ladsweb
- The gateway for ordering MODIS data products
- _[http://ladsweb.nascom.nasa.gov/](http://ladsweb.nascom.nasa.gov/)_
- And an old friend:
- _[http:](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[//modis-atmos](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[.](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[gsfc](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[.](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[nasa](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[.](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[gov/IMAGES/index](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)__[.html](http://modis-atmos.gsfc.nasa.gov/IMAGES/index.html)_

## A Quick and Dirty Way to Analyze MODIS DATAGiovannihttp://g0dup05u.ecs.nasa.gov/Giovanni/The tool uses monthly means of degree by degree data to generate graphical output over time or area. The user can interactively choose any area of the globe, for any time period for land and/or ocean, for several MODIS products. The data used to generate each graph can be downloaded as an ASCII file. Currently Giovanni data is limited to monthly means.  There are plans to add daily data to the system._x0013_It is important to understand what Giovanni can and cannot do.Before attempting to use Giovanni as a real research tool carefully read the documentation.  Contact the Giovanni or MODIS teams to verify that this data can be legitimately used for the proposed project.

## MAPPS

- _[http://modis-atmos.gsfc.nasa.gov/validation_corrdata.html](http://modis-atmos.gsfc.nasa.gov/validation_corrdata.html)_
- Go down to the yellow box on the page.
- Two types of data.
- Yearly Site Data
-       Organized by Site for Aqua or Terra
-  Includes hundreds of locations around the world, many that
-     are associated with AERONET sites.
- Data is a downloadable ASCII file of a complete year of MODIS
-     retrieval statistics (mean/stdev etc) of a 50km box surrounding
-     that location.
- 2)  Daily Global Data
- For a particular day, you can download the complete global
- data set of match-ups between MODIS and AERONET
- A single file for each day.

## ReferencesAll things MODIS atmosphere products:http://modis-atmos.gsfc.nasa.govMODIS Level 1 Products Descriptionhttp://www.mcst.ssai.biz/mcstweb/L1B/product.htmlMODIS Level II Products Descriptionhttp://modis-atmos.gsfc.nasa.gov/products.htmlDetailed description of the aerosol product and a link to the ATDBwhich describes the aerosol algorithms in detail.http://modis-atmos.gsfc.nasa.gov/MOD04_L2/index.html