Air-quality forecasting for the Pacific Northwest


OMI Satellite/AIRPACT-3 Comparisons

(View additional imagery:  CO from AIRS instrument)

Explanation of Images

Monthly Average NO2 from OMI (Ozone Monitoring Instrument) and AIRPACT are for 1pm-2pm values only (when OMI passes over the region). Pixels with over 35% cloud cover are not included in the averaging function. An assumed GEOS-CHEM profile is used to add an estimated "below cloud" contribution to the Tropospheric Column derived from OMI.

OMI values are from the tropospheric NO2 Vertical Column Data Product from NASA. AIRPACT values are taken from mixing ratio forecasts for all vertical layers and then vertically integrated into a single Vertical Column Density value. Ratios and Residuals are also calculated and provided to give a quantitative factor & difference between the satellite observations and the modeling system.

The OMI Tropospheric NO2 algorithm assumes an annually averaged stratospheric contribution, which is subtracted from the total column measurement. Since seasonal changes in stratospheric NO2 are not factored in, a shifting bias over the whole domain can be seen. Overall, this results in OMI Tropospheric NO2 showing larger summer values and smaller winter values.

These AIRPACT results have been spatially averaged to the coarser OMI pixel resolution.  Select from the monthly tabs below.

Additional satellite products links:

Mirador ( is a new search and order Web interface at NASA. It has a clean interface and employs the Google mini appliance for metadata keyword searches. Other features include quick response, data file hit estimator, Gazetteer (geographic search by feature name capability), and an interactive shopping cart.

Giovanni ( is a Web-based application developed by NASA that provides a simple and intuitive way to visualize, analyze and access vast amounts of Earth science remote sensing data without having to download the data.



US OMI March2007

Airpact March2007

Ratio March2007

Residual March2007


US OMI April2007

Airpact April2007

Ratio April2007

Residual Arpil2007


US OMI May2007

Airpact May2007

Ratio May2007

Residual May2007


US OMI June2007

Airpact June2007

Ratio June2007

Residual June2007


US OMI July2007

Airpact July2007

Ratio July2007

Residual July2007


US OMI Aug2007

Airpact Aug2007

Ratio Aug2007

Residual Aug2007


US OMI Sept2007

Airpact Sept2007

Ratio Sept2007

Residual Sept2007


US OMI Oct2007

Airpact Oct2007

Ratio Oct2007

Residual Oct2007


US OMI Nov2007

Airpact Nov2007

Ratio Nov2007

Residual Nov2007


US OMI Dec2007

Airpact Dec2007

Ratio Dec2007

Residual Dec2007



US OMI Jan2008

Airpact Jan2008

Ratio Jan2008

Residual Jan2008


US OMI Feb2008

Airpact Feb2008

Ratio Feb2008

Residual Feb2008


US OMI Mar2008

Airpact Mar2008

Ratio Mar2008

Residual Mar2008


US OMI Apr2008

Airpact Apr2008

Ratio Apr2008

Residual Apr2008


US OMI May2008

Airpact May2008

Ratio May2008

Residual May2008


US OMI Jun2008

Airpact Jun2008

Ratio Jun2008

Residual Jun2008


US OMI Jul2008

Airpact Jul2008

Ratio Jul2008

Residual Jul2008


US OMI Aug2008

Airpact Aug2008

Ratio Aug2008

Residual Aug2008

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