Exceptional events monitoring using S-NPP VIIRS aerosol products

The Suomi National Polar-orbiting Partnership (SNPP) Vis ible Infrared Imaging Radiometer (VIIRS) instrument was launched on October 28, 2011 to provide operational environmental monitoring which includes exceptional events such as dust storms, smoke, urban haze, and volcanic ash. The VIIRS aerosol products include pixel-level (∼750m) aerosol optical thickness (AOT) and aerosol detection which includes dust and smoke mask/aerosol index. The VIIRS aerosol product resolutions and its large swath width (∼3000 km) provide an unprecedented capability to observe small-to-large scale exceptional events that impact human health and economy. The VIIRS aerosol products have a demonstrated accuracy, precision, and measurement range to reliably observe and track exceptional events and aid operational air quality forecasters in providing warnings and alerts to the public. This presentation will illustrate VIIRS aerosol product capabilities and limitations using examples of exceptional events such as a multi-day smog blanketing China (November-December 2015), long range transport of smoke from forest fires in Alaska and Canada impacting regional air quality in the northeast United States (June 2015), and long range transport of dust from Africa impacting air quality in the south eastern United States (June 2015). While the aerosol imagery is very valuable to forecasters in providing the regional extent of an exceptional event (e.g., upwind conditions and their impact downwind), drawing quantitative estimates of surface concentrations of particles smaller than 2.5 μm in diameter (PM2.5, μg/m³) from AOT often times requires additional information or assumptions. The Chinese smog case where the observed VIIRS AOT values did not necessarily reflect the high surface PM2.5 values (∼600 μg/m³) observed by ground stations and the identification of aerosol type in the smog as smoke due to the presence of highly absorbing brown carbon will be used as an example to demonstrate the strengths and limitations of applying remotely sensed aerosol products to air quality monitoring and forecasting.