Moderate PM2.5 concentrations were measured in several stations across the US. Easter states in the Northeast, Mid-Atlantic and the Great Lakes region experienced moderate levels. The west coast on the other hand, reached moderate levels in Oregon, Washington and California (top left). Although several fires were observed in Central and Western Canada and some scattered fires in the US, these fires are not producing significant smoke (top right). Regional tropospheric NO2 columns from OMI detected high NO2 in Southern California (bottom left). Finally, high AOD levels were retrieved by MODIS in the central states during the afternoon (bottom right).
International Feature: Haze in northeastern China
Chinese authorities shut down much of Harbin - a city of more than 10 million people - as unusually high levels of pollution shrouded the city and the surrounding region in mid-October, 2013. Measurements taken on October 20, 2013 scored the air quality index in the city at 500, the highest possible reading. Levels above 300 are considered hazardous to human health.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite acquired this true-color image of northeastern China on October 21. The brightest areas are fog, which is tinged with gray or yellow due to the air pollution. Other cloud-free areas have a pall of gray and brown smog that blots out the city and surrounding towns. Harbin lies under the Y-shaped patch of fog and smog in the south-central section of the image, completely obscured from view.
Some neighborhoods experienced concentrations of fine particulate matter (PM 2.5) as high as 1,000 micrograms per cubic meter. For comparison the U.S. Environmental Protection Agency's air quality standards state that PM 2.5 should remain below 35 micrograms per cubic meter. It is extremely rare for particulate levels to reach such high levels in the absence of a dust storm or forest fire.