Today was an Air Quality Action Day in Utah and the National Weather Service issued a Hazardous Weather Outlook for the next week for western two thirds of Utah and southwest Wyoming. A high pressure system will promote the development of valley inversions through the week resulting in an increase of fog and urban haze. Hazy is visible over Utah's Cache Valley in Logan, Utah (image courtesy of Utah State University) skies can be seen in today's Utah State University webcam image (top left image). PM2.5 concentrations ranged between 18 to 40 ug/m3 after 8:00 am LT, as shown in the PM2.5 timeseries (courtesy of Airnowtech). The contribution of this haze to AOD retrievals was not possible today due to the presence of clouds, as shown in MODIS RGB image.
Urban air quality is influenced by the spatial and temporal distribution of emissions in cities, the topography of the urban area and its vicinity and the weather, including its atmospheric circulation patterns. Particulate matter (PM) pollution events are enhanced by temperature inversions that trap pollutants near the surface from reduced turbulence and mixing with air aloft. Surface temperature inversions play a major role in air quality, especially during the winter, when these inversions are the strongest. The warm air aloft on top of cooler air acts like a lid, suppressing vertical mixing and trapping the cooler air at the surface. As pollutants are emitted into the air, the inversion traps these pollutants near the ground, leading to poor air quality.
In the Mid-Atlantic United States, we experienced Good air quality. Lidar observations over Baltimore show a homogeneous boundary layer that extended up to 1 km. Clouds were also present through our observations at heights above 8 km.