October 21, 2014

Moderate AQI in Texas and Mississippi Valley Region. Increased NO2 in Ohio River Valley.

The EPA AQI image, below left, shows areas of Moderate AQI in parts of California, Texas, and the Mississippi Valley region. The VIIRS AOD retrieval, bottom right, shows very minimal increases in AOD throughout the country. There are some increases corresponding to the Moderate AQI in Texas.

The surface PM 2.5 model, courtesy NAAPS below left, shows continuing dust blowing in the Pacific Northwest region. This model also shows an increase in the surface sulfates in Texas and in the Ohio River Valley. The OMI NRT NO2 retrieval picks up an increases in the NO2 in the troposphere that appears to be in a similar region as the sulfates from the NAAPS model.

October 19, 2014

Weekend Edition: Lovely weather over the US

Outside of a curious code red in the eastern desert of California, most of the US is code green or isolated areas of moderate AQI. The AQI reading in California maximized Sunday morning at 11:00 AM but there are no stations shown on AIRNOW which correspond to such elevated AQI readings. Perhaps someone has an explanation or it may be an anomalous report.

In Maryland, we could not have had a more beautiful day. The Baltimore Webcam shows you can see forever and on the very left of the image, Baltimore's Ravens clobbered the Atlanta Falcons. Go birds. And good luck to the Giants on Tuesday.

October 17, 2014

Spots of Moderate AQI as Gonzalo hits Bermuda

The EPA AQI loop, below left, shows spots of Moderate AQI scattered throughout the country, with one area in southern California briefly reaching Unhealthy for Sensitive Groups. This may be related to the low pressure system shown draped across the eastern part of the country in the NWS imagery below right, which would have rained out some of the aerosols as it moved through and brought in a different air mass as it moved out.

The webcam image from Yosemite National Park below left shows visibility intermediate between that for the good and bad visibility example days shown below right, in keeping with its location somewhat near the edge of an area of Moderate AQI.

The MODIS Terra image below unfortunately does not capture the brilliant colors starting to appear on the trees, but it does catch a portion of Hurricane Gonzalo, currently making its way through Bermuda. Hurricane Gonzalo is not expected to affect mainland U.S. directly, although it will at least brush Newfoundland and will increase winds and wave heights along the Atlantic coast.

October 16, 2014

Good air quality in the US; Dust in Utah and Idaho

Today most of the U.S. experienced good air quality except in California where moderate levels were recorded throughout the day (top left). Moderate levels were also reached in Louisiana and in the Great lakes region. Although some fires took place in different states, HMS indicated that no significant smoke was produced out of those fires (top right). However, a relatively small area of blowing dust was visible moving eastward over northern Utah, over Great Salt Lake, into southern Idaho, and currently reaching the Utah/Wyoming border. This dust originates from sand dunes located directly west of Great Salt Lake. NRL modeling also predicted dust in the same region as well as sulfate in the Eastern states (bottom).

SPECIAL FEATURE: Smoke Above the Clouds

If you look at satellite imagery of Earth on a browser like Worldview or NOAAView, a few important features of the atmosphere become obvious. First, clouds dominate the view. They cover about 60 percent of the planet at all times, and the percentage is even higher over oceans, where banks of low-lying stratocumulus clouds often form. Second, plumes of smoke, dust, and industrial haze--which are made up of airborne particles called aerosols--often darken portions of the atmosphere.
What happens when these two atmospheric heavyweights--clouds and aerosols--meet? Scientists at NASA are working to understand this. "One of the key uncertainties remaining in climate science relates to how clouds and aerosols interact," explained Hiren Jethva, a scientist at Goddard Space Flight Center. "And one of the reasons for that relates to what happens when aerosols end up above the cloud layer."
Aerosols can rise or get blown above clouds. They often do just that between July and September in Central Africa, where agricultural fires produce plumes of smoke that blow offshore and drift over low-lying clouds in the southeastern Atlantic. Similar aerosol-over-cloud situations occur in other parts of the world. Saharan dust blows over clouds in the Atlantic, and smoke from southeast Asia hovers over clouds in the Pacific. "Aerosols elevated above clouds can travel faster and longer than those near the surface, implying far-reaching impacts," explained Hongbin Yu, an atmospheric scientist at Goddard.
The images above come from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the CALIPSO satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. They show a smoke plume elevated above a cloud layer in the southeastern Atlantic on September 10, 2014. The smoke came from agricultural fires in central Africa, which were widespread in that region in September. The background (top) image was captured by MODIS and provides a true-color view of the smoke and clouds from above. The yellow line indicates the path of the CALIPSO satellite and its laser, which sent pulses of light (lidar) down through the atmosphere and recorded the reflections in a vertical profile (lower image). The MODIS image has been rotated (north is to the right) so that the line that depicts the CALIPSO flight track is aligned horizontally.
Whether smoke or dust hovers above clouds or in a cloud-free environment can lead to very different impacts on the atmosphere and climate. "To put it simply, smoke or dust in cloud-free conditions generally causes a cooling of the Earth-atmosphere system," said Yu, "whereas the same types of particles may have a warming effect if they are located above clouds."
Why the difference? Smoke and dust plumes contain large number of "absorbing aerosols"--particles that both scatter and absorb the energy in sunlight. In cloud-free conditions, the scattering effect dominates, and the particles reflect more solar radiation back to space than underlying dark surfaces such as the ocean or a forest. This produces a cooling effect.

October 15, 2014

Code Yellow to Orange PM2.5 AQI levels in California; Hurricane Gonzalo Headed to Bermuda

California continued to experience Code Yellow to Orange (Moderate to Unhealthy for Sensitive Groups) PM2.5 AQI levels today. The presence of clouds hindered AOD retrievals over this region as shown in the MODIS Aqua RGB image (top right). In the eastern US AQI was good for PM2.5 and Ozone. Warm and humid weather conditions were experienced during the morning hours. A frontal passage made its way through washing out any pollutants in over this region. Infrared image from GOES East shows clouds along the eastern seabored. Hurricane Gonzalo is also captured in the GOES IR image. Hurricane Gonzalo, the strongest Atlantic hurricane in three years, is poised to deliver a direct hit on Bermuda by the end of the week and potentially eastern Canada over the weekend. Gonzalo is currently a Category 3 hurricane, with sustained winds of 125 mph, which is a which is a "major" hurricane. Category 3, 4, or 5 hurricanes are considered as "major" on the Saffir-Simpson wind scale with wind speeds of at least 111 mph.

October 14, 2014

Increased AOD from continued dust blowing in Plains region.

The EPA AQI loop, below left, shows areas of Moderate AQI in parts of California, with an area of Unhealthy for Sensitive Groups in the San Bernardino Valley persisting for most ofthe day. The HMS fire and smoke product, below right, shows scattered fires throughout the country and a larger concentration of fires in souther Canada. It is important to note that there are minimal fire sources in the Plains region.

The surface PM 2.5 model, courtesy NAAPS below left, shows continuing dust blowing in the Plains region. Below right, the GASP retrieved AOD for the day. Although heavy cloud cover persisted throughout the day, there are glimpses of increased AOD in the Plains region that is mostly likely correlated to dust blowing in the region.

October 13, 2014

Numerous Fires Dot the Nation; Dust Covers Central US

No heavy smoke hangs over the nation today, but there are numerous fires present in the Pacific Northwest, South, and Southeast creating patches of light smoke (NOAA HMS, left). Hundreds of fires can be seen leaking over the Canadian border into the Northern Plains States as well, also producing some small clouds of light smoke. The mix of elevated urban ozone and PM2.5 pollution in Southern California, especially, is resulting in USG AQIs in the area (EPA, right). PM2.5 pollution can also be seen spotting up the West Coast as well as in the Great Lakes Region and some parts of the East Coast, showing up as Unhealthy AQIs in the EPA AirNow combined loop.

Large amounts of dust are also predicted to be swarming over the Central US, reaching 102.4 mg/m^3 over, mainly, New Mexico (NAAPS Aerosol Model, left). The dust is presumably relatively domestic--kicked up by strong winds--and is predicted in the model to diffuse south and eastward as the week progresses. Sulfates also have a presence on the east coast, possibly affecting air quality there, which helps explain the presence of Unhealthy AQIs in the EPA AirNow loop. The nation is looking into warmer weather this week. The areas of high pressure covering most of the US will make it harder for dust or smoke in the nation to diffuse (NOAA Forecast, right).