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Giovanni-3 Online Users Manual 10.; OMI L2G Giovanni

  


All of the questions below are linked to descriptive answers in this chapter of the Giovanni Online Users Manual regarding theOMI instance and the OMI L2G instance. Click the question of interest.

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1. What does "L2G" in "OMI L2G" stand for?

2. Why is there a separate Giovanni instance for OMI L2G data?

3. What are the available data parameters in the OMI L2G instance?  What do OMAERUVG, OMTO3G, and OMNO2G represent?

4. Is the time period for OMI L2G data availability the same as the time period for Level 3 OMI data?

5. What is the difference between the Column Amount Ozone data parameter from the OMDOAO3G and OMTO3G data products?

 

6. What is the difference between Aerosol Extinction Optical Depth and Aerosol Absorption Optical Depth?

7. I see there is awavelength-specific option for OMAERUVG data products.  What can I use this for?

 

What does "L2G" in "OMI L2G" stand for?

The L2G data are special gridded level 2 OMI products. All of the information from the original high-resolution level 2 data for a single day (00:00:00 to 23:59:59 UTC) are binned into 0.25 x 0.25 degree grids (except for the OMI SO2 product which is binned at 0.125 x 0.125 degrees). All data pixels which fall within a grid cell are stored without averaging. Duplicate pixels which fall in the same grid cell called 'Candidates' are indexed in a third 'nCandidate'  dimension.

Why is there a separate Giovanni instance for OMI L2G data?

We maintain two separate OMI instances, one for the gridded daily Level 3 data, and a second for the Level 2G data products.

What are the available data parameters in the OMI L2G instance?

Currently the available data parameters are listed in the table below.

Is the time period for OMI L2G data availability the same as the time period for Level 3 OMI data?

In general yes. Sometimes one data level is processed and delivered before  the other is ready. Thus one may at times see a difference in the end date  between the level 2G and its corresponding level 3 data product.

What is the difference between the Column Amount Ozone data parameter from the OMDOAO3G and OMTO3G data products?

OMI provides two different Total column ozone values that are based on two different ozone retrieval algorithms. These are referred as NASA TOMS-Like algorithm (OMTO3) and KNMI/TIhe Netherlands DOAS algorithm( OMDOAO3). The KNMI Differential Optical Absorption Spectroscopy (DOAS) approach takes advantage of OMI's hyperspectral measurements. In the current version 003, the two datasets are in good agreement, though some differences still exist in high latitudes and over snow/ice.

What is the difference between Aerosol Extinction Optical Depth and Aerosol Absorption Optical Depth?

Aerosol Extinction Optical Depth represents the Total Optical Depth, a measure of absorbing and scattering aerosols while Aerosol Absorption Optical Depth is a measure of absorbing aerosols only.

I see there is a wavelength-specific option for OMAERUVG data products.  What can I use this for?

The OMAERUVG aerosol data are available at 3 different wavelengths: 354,  388 and 500 nm. When using any of the OMAERUVG parameters you must select  which wavelength you want to view. Currently, you may only select one  wavelength at a time.

 

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