DATA ACCESS AND FORMAT

As of the end of October 2009, the full GlobAEROSOL dataset is publicly available for download from the project FTP:

ftp.globaerosol.info

This dataset comprises the following product types:

ATSR-2 Orbit-based Pixel Counts. These are supplementary files generated for ATSR-2 alone, which contain the number of instrument pixels from each channel which were included in each retrieval grid cell.

Individual-sensor Orbit-based Aerosol Products (IOAP). These files contain all the output of the individual sensor retrievals, with coverage corresponding to that of the original level 1 (radiance) data from the sensor.

Individual-sensor Global Aerosol Products (IGAP). These constitute bias-corrected daily maps of aerosol properties derived from each sensor, at a specific time of day. For ORAC retrievals results are only reported for the "best" aerosol type (and this type is identified). In all cases the IGAPs contain estimates of aerosol optical depth (AOD) at 550 nm and 865 nm and the Angstrom coefficient.

Merged Global Aerosol Products (MGAP). One MGAP is produce per day which combines the results from all available sensors into a single map in the same format as the IGAPs, valid for the same specific time of day. The same algorithm is defined below to implement the merging steps necessary to generate both the IGAPs and MGAPs from the IOAPs. From the processing point of view IGAPs are produced by running the merging scheme using IOAPs from one instrument only.

Statistical products. These composite products are calculated from the previous IGAP or MGAP files over a certain period (i.e. weeks, months or years).

All products are based upon the NetCDF format, a machine-independent, self-describing, binary data format standard for the exchange of scientific data. The actual details on the format and contents of these files can be found in the GlobAEROSOL Product User Guide (PUG).

Additional questions or inquiries may be directed to:

Tools and source code

A simple IDL tool for plotting GlobAEROSOL products, and even convert them to Google Earth format, can be downloaded here, along with its source code. To execute it, you will need at least the IDL Virtual Machine installed in your computer.

A script is included for easily running it under Linux:

Usage:

  globaer_plot.sh [product] [options]

Options:

  --output xxx           Output filename
  --width  nnn           Width of the output plot
  --height nnn           Height of the output plot
  --projection xxx       IDL map projection to be used
  --center ddd.d ddd.d   Coordinates of the center of the map
  --rotation ddd.d       Angle the projection shall be rotated
  --region ddd.d [...]   Region of interest to be represented
  --variable xxx         Variable to represent from the product
  --minimum ddd.d        Lowest value to be used in the color scale
  --maximum ddd.d        Highest value to be used in the color scale
  --palette nnn          IDL color palette to be used
  --quicklook            Generate a quicklook (default)
  --thumbnail            Generate a thumbnail
  --kmz                  Generate a Google Earth file

In addition, some example IDL source code which illustrates how to directly read and plot data from the IOAPs and daily GAPs can be downloaded from here. At the IDL prompt type "plot_globaer_eg, 'FILE'", where 'FILE' is the name of either an IOAP (*ORBIT*.nc) or daily GAP (*DAILY*.nc).

Google Earth

The following files enable GlobAerosol products and validation results to be easily viewed on Google Earth:

Merged daily products, including AATSR dual view results:

GlobAerosol_MERGED-dual-view_200409.kmz

Time-series comparisons with Aeronet stations for which at least 3 acceptable coincidences are found during the test month of September 2004. Click on a station to view the comparisons. Refer to the Preliminary Validation Report for a description of these plots and discussion of the results.

aeronet_comparisons.kmz