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3-day composite MODIS aerosol optical depth (AOD, ta), cloud optical thickness(COT), hourly in-situ PM2.5 mass concentrations, NAM 850mb wind vectors, and WF-ABBA fire locations

3-day composite MODIS image

Sample 3-day MODIS ta hourly PM2.5 mass concentration animation

The data fusion animation plots the most recent three days data of available daily MODIS (the Moderate Resolution Imaging Spectroradiometer) aerosol optical depth (in color contours), daily MODIS cloud optical thickness (in gray contours), hourly PM2.5 (Particulate Matter with a diameter smaller than 2.5 microns) concentrations for the in-situ continuous monitors (vertical color bars), NAM (North American Mesoscale Model) 850mb wind field vectors, and half-hourly WF-ABBA (Wildfire Automated Biomass Burning Algorithm) fire counts (pink and purple diamonds) . This data fusion visualizes the relationship between the MODIS ta, hourly PM2.5 mass concentration and the air quality index, providing a pseudo-synoptic view of aerosol events across North America.

MODIS derived aerosol optical depth, ta (AOD)

The MODIS ta used for these plot is based on the MOD04_L2 aerosol product (MODIS ATBD Kaufman and Tanré 1998) and is from the MODIS sensor aboard the Terra satellite which has a descending orbit and a 10:30 equatorial overpass time. The predicted and actual overpass time for a given day can be found at The MODIS ta is at a 10 x 10 km2 spatial resolution and is plotted on a scale of 0.0 to 1.0 with ta > 1.0 shown as dark red.

Aerosol Optical Depth scale

MODIS cloud optical thickness (COT)

The MODIS COT used for these plots is based on the MOD06_L2 cloud products (cite ATBD) and is from the MODIS sensor aboard the Terra satellite with a descending orbit and a 10:30 equatorial overpass time. A ta is not derived for cloud filled pixels, therefore the clouds fields derived from MODIS are plotted to help define synoptic weather features important to the movement of aerosols.

Cloud Optical Depth scale

In-situ hourly PM2.5 mass concentrations

The location of each continuous PM2.5 monitor from the State and Local Air Monitoring Stations (SLAMS) and National Ambient Monitoring Stations (NAMS) is represented by a color circle. The color of the circle represents the hourly PM2.5 concentration (ug/m3) and the color represents the associated US EPA Air Quality Index (AQI) level based on a 24 hour running average, see table below. An AQI above 100 means PM levels are unhealthy for sensitive groups.

Air Quality Index for Particles

Index values Category Cautionary Statements PM2.5
0 - 50 Good None 0 - 15.4 0 - 54
51 - 100 Moderate Unusually sensitive people should consider reducing prolonged or heavy exertion. 15.5 - 40.4 55 - 154
101 - 150 Unhealthy for Sensitive Groups Sensitive groups should reduce prolonged or heavy exertion. 40.5 - 65.4 155 - 254
151 - 200 Unhealthy Sensitive groups should avoid prolonged or heavy exertion; everyone else should reduce prolonged or heavy exertion. 65.5 - 150.4 255 - 354
201 - 300 Very Unhealthy Sensitive groups should avoid all physical activity outdoors; everyone else should avoid prolonged or heavy exertion. 150.5 - 250.4 355 - 424
Source: US EPA, 1997

NAM forecast 850 mb wind vectors

The 850 mb wind field vectors are plotted to show wind direction and speed. Often this can be used to qualitatively show areas of convergence and divergence, and is one indicator of vertical air motion.

GOES Wildfire Automated Biomass Burning Algorithm (WF-ABBA)

Half-hourly fire locations as identified by the GOES (Geostationary Operations Environmental Satellite) WF-ABBA are plotted to identify fire activity. The fire locations plotted are temporally filtered, reporting fire pixels that appeared more than once within 24 hours (0Z – 24Z). The locations of the fire pixels are color coded by the assigned flags explained below.

Pink diamonds include fire pixels flagged at 0, 1, or 2

0. Fire pixel that could be processed for sub-pixel instantaneous estimates of fire size and temperature.
1. Saturated pixel. The temperature of the hot spot was higher than the sensor could evaluate.
2. The fire pixel was cloudy.

Violet diamonds include fire pixels flagged at 3 or 4

3. This is a high probability fire pixel. Keep monitoring for future development.
4. This is a medium probability fire pixel. Keep monitoring for future development.

Pixels flagged as 5 are not plotted.

5. This is a low probability fire pixel. This category is often indicative of false alarms in North America along cloud edges and at high viewing angles at sunrise and sunset, but should be monitored over time

For additional information on GOES WF-ABBA go to

MODIS aerosol optical depth and cloud optical thickness data is being obtained from the Cooperative Institute for Meteorological Satellite Studies University of Wisconsin, Madison through MODIS Direct Broadcast (DB).

In-situ PM2.5 mass concentration data is being obtained from the US EPA AIRNow Program in cooperation with State and Local Air Agency Partners

NAM meteorological data is being obtained from the Air Resource Laboratory of NOAA (National Oceanic and Atmospheric Administration).

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