California Air Resources Board

Application of satellite remote sensing data for air quality

Satellite remote sensing provides data on air quality. The spatial gaps of ground monitoring resources are inevitable, and satellite data are able to fill in air quality information in areas without a ground monitor. There are numerous satellite data that can indicate criteria air pollutants (e.g., PM2.5 and NO₂) and greenhouse gases (e.g., CH₄ and CO₂). The selection of satellite data to address specific air quality issues depends on data accuracy and spatial and temporal resolution among others.

CARB staff have been actively involved in satellite remote sensing research to answer air quality questions. We estimated ambient PM2.5 concentrations using NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD, 10 km resolution) data and land use regression in California for 2006-2012 (external link to journal article). AOD is a measure of light extinction (i.e., scattering + absorption) by atmospheric aerosols, thus enabling AOD to be a predictor of ambient PM2.5. This research enhanced our understanding of PM2.5 spatial distribution that might not be shown only with ground PM2.5 monitors. Due to the expanded spatial coverage of PM2.5 concentrations, estimates of PM2.5 concentrations from satellite data can be useful for numerous air quality studies including but not limited to the identification of air pollution hotspots, health effect studies, and air pollution trends.

CARB staff also participated in a collaborative research to estimate PM2.5 species concentrations (i.e., sulfate, nitrate, organic carbon, and elemental carbon) using satellite data in Southern California for 2001-2015 (external link to journal article). This research took advantage of recently developed 4.4 km resolution Multi-angle Imaging SpectroRadiometer (MISR) AOD data. Estimates of PM2.5 species concentrations are useful to show the relative contribution of each composition to total PM2.5 and thus strengthen our understanding of source types for PM2.5. Decreasing trends of all PM2.5 species concentrations for the 15-year period showed that air pollution mitigation strategies have been working in the study region.

Other remote sensing research for air quality and climate change

CARB has recently funded research projects using remote sensing techniques. Remote sensing instruments can be deployed not only on satellites but also at ground and in the aircrafts. The following research shows remote sensing applications for multiple air pollutants and greenhouse gases.

Determination of the Spatial Distribution of Ozone Precursor and Greenhouse Gas Concentrations and Emissions in the LA Basin (Contract 09-318, Completed in 2015) The investigators developed two remote sensing methods to scan the LA basin with remote sensing instruments located in NASA/JPL’s California Laboratory for Atmospheric Remote Sensing (CLARS) on Mt. Wilson (1673 meters ASL). Despite the single monitoring location of the instruments, the high-altitude deployment of the remote sensing instruments enabled the measurements of trace gases, aerosols, and greenhouse gases in the whole LA basin. This study also examined temporal variability in ozone production efficiency, indicated by (HCHO:NO2) ratios, and generated top-down estimates of CH₄ and CO₂.

Airborne Visible/Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) for California Statewide Methane Survey (Contract 15RD028). The Survey is a collaborative study of CARB, California Energy Commission (CEC), and NASA/JPL to identify methane emission sources at the facility level. NASA/JPL’s airborne methane imaging was performed by using the AVIRIS-NG instrument. Phase 1 of the Survey was funded by CARB, interim Phase 1 report is available for public review.