All of the questions below are linked to descriptive answers in this chapter of the Giovanni Online Users Manual regarding the Giovanni Air Quality Data instance. Click the question of interest.
- What is the Giovanni Air Quality instance?
- What is PM2.5?
- How is the PM2.5 data obtained?
- What date types are available in Giovanni Air Quality? How are the satellite data different from the PM2.5 data ?
- How can I compare satellite and ground based PM2.5 data using Giovanni ?
- What data parameters are currently available from Giovanni Air Quality?
- How are the data parameters selected in Giovanni Air Quality?
- How is the spatial area of interest selected in Giovanni Air Quality?
- Why is there a pre-selected area ?
- How is the temporal range of interest selected in Giovanni Air Quality?
- Are there any limits on the geographical or time range that can be selected in Giovanni Air Quality?
- What are the current data analysis and visualization (output) capabilities in Giovanni Air Quality?
- Where else can I obtain additional MODIS and OMI data ?
- What other air quality products are available in Giovanni?
What is the Giovanni Air Quality instance?
The Giovanni Air Quality instance combines remote-sensing data with ground-based monitoring data for visualization and exploration of air quality-related data. Giovanni Air Quality includes gridded U.S Environmental Protection Agency (EPA) AIRNow (http://airnow.gov/) concentrations of fine particulate matter or PM2.5 over the continental United States at 1°x1° resolution.
What is PM2.5 ?
PM2.5 is the concentration in micrograms per cubic meter of particles with a diameter of 2.5 micrometers or less. PM2.5 is an air pollutant because due to the small size of these particles, they can lodge deep in the lungs, leading to potential health problems.
Giovanni parameter definition: Fine Particulate Matter – PM2.5
Click the link below to learn more about the health and environmental effects of PM2.5:
Particulate Matter: Health and Environment
PM2.5 is also one of six criteria pollutants, which means that it is regulated by the EPA, which has established maximum allowable concentrations, as required by the U.S Clean Air Act. Click the link below for additional information:
PM [Particulate Matter] Standards
How is the PM2.5 data obtained?
The Giovanni PM2.5 data are obtained from the U.S Environmental Protection Agency (EPA) AIRNow (http://airnow.gov) real-time concentrations over the continental U.S. PM2.5 concentrations are originally obtained at DATAFED , where they are mapped to a 1° x 1° degree grid, then temporally averaged, and then transferred to Giovanni via WCS internet protocol.
What date types are available in Giovanni Air Quality? How are the satellite data different from the PM2.5 data ?
The MODIS and OMI aerosol satellite data in Giovanni Air Quality are column measurements, and do not include information on the vertical distribution of aerosols. This means that satellite detected aerosols may or may not be located at the surface. PM2.5 concentrations are in situ surface measurements, where air quality will affect human health.
How can I compare satellite and ground based PM2.5 data using Giovanni ?
Giovanni provides several services that allow comparisons among these datasets, including time-series, scatter plots and correlation plots. See below for more detailed description of each service.
What data parameters are currently available from Giovanni Air Quality?
(Note that Cloud Optical Depth may also be termed Cloud Optical Thickness. The two terms describe the same data parameter.)
How are the data parameters selected in Giovanni Air Quality?
Individual parameters are selected by clicking in the check boxes. An entire group may be selected by clicking the group box (leftmost column heading bar, next to the collection name and date range information). If this selection is performed, individual parameters may then be deselected by clicking in the appropriate check box(es).
How is the spatial area of interest selected in Air Quality Giovanni?
The spatial area of interest can be selected by either of the two methods described below:
Java applet map: The Java applet map can be utilized to "click and drag" a selection box to designate the spatial area of interest.
Geographic coordinates: The geographic coordinates of the corners of the spatial area box can be input individually. This method can be used if Java is not enabled. Note that decimal and not degree (seconds and minutes) coordinates must be entered.
Why is there a pre-selected area ?
Giovanni Air Quality has a pre-selected data of interest because currently the PM2.5 data are only available over the continental U.S. Other satellite data are available globally. (Zoom out of the current map to obtain global data.)
How is the temporal range of interest selected inGiovanni Air Quality?
The starting date (year/month/day), and the ending date (year/month/day) for the analysis are selected using the calendrical menus on the Giovanni interface page. Error messages will be generated if the beginning month or the end month are out of the data set time range, or if the end month is before the beginning month.
Are there any limits on the geographical or time range that can be selected in Giovanni Air Quality?
The PM2.5 data are only available over the continental U.S. All of the satellite data in the Giovanni Air Quality instance (from MODIS and OMI) are available globally. For the MODIS data the time ranges are for MODIS-Terra Collection 5 data set. If a temporal range in the MODIS-Terra dataset time range is chosen, but with MODIS-Aqua data selected for analysis, an error message will be generated if this temporal range is not in the MODIS-Aqua dataset time range. This error will be generated primarily with an incorrect starting date.
What are the current data analysis and visualization (output) capabilities in Giovanni Air Quality?
There are currently 12 data analysis and visualization options in the Air Quality Instance:
Where else can I obtain additional MODIS and OMI data ?
The MOVAS Giovanni instanceand the OMI Giovanni instanceprovide additional parameters related to atmospheric chemistry.
What other Air Quality Products are available in Giovanni ?
MISR and GOCART Modeldata are also available through Giovanni.
The Giovanni A-Train Instance provides CALIPSO aerosol flag vertical profile data, and MODIS Aqua, OMI, and AIRS data collocated along the CloudSat track.