This posting is from Sunny(!) California where I am out at the American Geophysical Union Fall Meeting in San Francisco. It is cold for SF (in the 30's, with frost in the morning) but it is not like home in Baltimore where there is now snow on the ground and the risk of freezing rain over the next 24 hours. Drive carefully in the east.

The MODIS image from this morning shows that the system that started in the Rockies by dumping on Denver has left a veil of snow all across the US. There are only a few places in the country that you can see the unsnowcovered surface. California and Washington are two of them. The AQI map for the country shows that PM is elevated to the unhealthy for sensitive groups range in Oregon and the very northern part of California. Generally, woodsmoke is a contributor to those elevated PM readings. For much of the rest of the US, the AQI is good.

In other AQI news, a new paper has been published in Lancet which says that the AQ standards in Europe are too lax. I have not yet read the paper which is featured in Monday's Independent newspaper.

Looking at the NOAA HMS Smoke and Fire Product (top left), the small red dots indicate some small fires along the West Coast and Florida. There are no noticeable smoke plumes corresponding to this, and the cloud cover over the majority of the United States prohibits most AOD data for today. In terms of ground-based data, the EPA AIRNow AQI loop (bottom left) shows Code Yellow AQIs on the West Coast and some of the Northeast, but most of those areas dissipated over the day, as the current high AQI is in Reno-Sparks, NV with 83 (North Pole, AK had a Code Yellow of 73.)

Even with the cloud cover, the air quality today seems to have bettered for the start of the weekend as compared to earlier in the week. The NRL NAAPS Aerosol model for sulfates (bottom left) has projected elevated surface SOx concentration on the East Coast, although the total column for optical depth has no significant increases over the entire United States (bottom right).

NASA aircraft and scientists have returned to the United States after a short ice-surveying mission to Antarctica. Despite having only a week of flying time, the team returned with crucial scientific data and a trove of spectacular aerial photographs.

The flights over Antarctica were part of Operation IceBridge, a multi-year mission to monitor conditions in Antarctica and the Arctic until a new ice-monitoring satellite, ICESat-2, launches in 2016. ICESat-1 was decommissioned in 2009, and IceBridge aircraft have been flying ever since. Previous Antarctic IceBridge flights took off from Punta Arenas, Chile, but this time NASA's P-3 took off from the sea ice runway at McMurdo Station, a first for the team. Operated by the National Science Foundation, the station is located on Antarctica's Ross Island. Flying from McMurdo meant the IceBridge team was able to survey some areas that were unreachable from Chile.

In 43 hours across five science flights in late November, the P-3 collected more than 20,000 kilometers (12,000 miles) worth of science data. Instruments gathered information about the thickness of the ice over subglacial lakes, mountains, coasts, and frozen seas.
Laser altimeter and radar data are the primary products of the mission, but IceBridge project scientist Michael Studinger almost always has his digital camera ready as well. On November 24, 2013, he took the top photograph of a multi-layered lenticular cloud hovering near Mount Discovery, a volcano about 70 kilometers (44 miles) southwest of McMurdo. (Full article:Earth Observatory)

Air quality in the Eastern half of the US continue to be in the Moderate to Unhealthy for Sensitive Groups for PM2.5. Limited vertical mixing, light surface winds, warmer and humid weather fueled PM2.5 concentrations to reached high levels, as shown in the Airnow AQI animation. Maryland's PM2.5 timeseries (top right image, courtesy for Airnowtech) for December 2-4 show that concentrations from 8-60 ug/m3, with highest values recorded in Hagerstown (NW Maryland). Concentrations in downtown Baltimore fluctuated between 20-45 ug/m3.

Lidar and sunphotometer measurements at UMBC show a shallow cloud (red signal returns in lidar image) capped boundary layer, where all particulates are confined to. There no signs of particulate aloft, except an occasional cloud above 3 km (not sown in image. The boundary layer over Baltimore has not reached heights beyond a kilometer since yesterday. December 3 optical column size distribution (clouds where persistent on Monday and today) retrieved from our CIMEL sun photometer (data and image available at AERONET) show the presence of fine particulate (radius smaller than 1 micron) within the boundary layer.

The first image below, courtesy NOAA HMS, shows the fire locations across the United States. The red dots correspond to active fires, and the grey areas are plumes. The major concentration of fires is in the Southeast region and Pacific Northwest region. Although there is a large concentration of fires, there is little smoke being picked up by HMS. The next image shows the retrieved AOD image for the day, courtesy MODIS Terra. The image shows an increase in the northeast due to PM 2.5 formation. With a high pressure system resting over the northeast over the past few days, it is has allowed for stagnation and light winds to increase production of wintertime aerosols. A strong temperature inversion near 700 m ASL has been seen in the radiosonde data from Aberdeen Proving Ground. This temperature inversion mixed with light winds has caused stagnation that has allowed for nitrates to increase in production.

The next image, courtesy EPA AIRNOW, shows the AQI values the Mid Atlantic region. There is an increase in the AQI values due to PM 2.5 at the surface. As mentioned above, overnight temperature inversions will reduce atmospheric mixing, and light winds will limit pollutant dispersion. These conditions, combined with pollutant carryover from day to day, have yielded Unhealthy for Sensitive Groups particle levels for the region (yesterday and tomorrow as well). The next image, courtesy OMI NRT, shows the retrieved NO2 column for the troposphere. This image shows a large amount of NO2 in this same region in the Mid Atlantic/Great Lakes regions. This enhancement in column NO2 shows a strong correlation with the increase in PM 2.5 at the surface.

Much of the Central Plains, Great Lakes, Southeast, Mid-Atlantic and Northeast experienced elevated air quality indices (AQIs) today (top left). Peak PM2.5 measurements reached Code Yellow (Moderate) levels, however several isolated areas across the Great Lakes and Mid-Atlantic reached the Code Orange (Unhealthy for Sensitive Groups) range. Unfortunately, widespread cloud cover over the polluted regions of the United States impeded Aerosol Optical Depth (AOD) readings from the MODIS overpass on board NASA's Terra satellite (top right). High pressure associated with atmospheric ridging in the upper-levels of the atmosphere over the Mid-Atlantic weakened the low-level flow over the region, likely contributing to low particulate dispersion in the planetary boundary layer, and therefore elevated PM2.5 (middle left). Observations from various stations across Maryland support this notion, as surface wind measurements were nearly stagnant throughout the afternoon (middle right). This weather pattern is forecast to remain in the region, tomorrow, motivating air quality forecasters to call for another, perhaps more widespread poor air quality day for Maryland (bottom).

We are moving into pollution season in the California Central Valley. As we discussed here last year, DISCOVER-AQ studied the lower San Joaquin Valley last year and found that while the PM levels could be very high, the Aerosol Optical Depth was generally not a good indicator of that since the planetary boundary layer in the valley is so shallow. High pollution in a thin layer does not give elevated AOD. Papers will be presented on these results at the upcoming American Geophysical Union meeting next week. The loop left shows those elevate PM readings overnight in the AIRNOW loop. The 3day composite history from IDEA shows the orange and red AQI's that have been seen in the west. Generally at this time of year, those readings are woodsmoke related as people fire up their fireplaces for heating. In the Central Valley, however, we found that smudge burning still exists in the valley to protect the crops and people tend to be careless in what they burn in their stoves, including waste wood and garbage. Not a pretty story for air quality.

Satellites are not much help today with the Pacific Northwest as those elevated PM levels are beneath cloud in Washington, Oregon and Idaho. The overnight peaks in PM, however, are indicative of home heating.

On Sunday, the MPLNET lidar at UMBC recorded an almost uniform PBL of 1000m all day long. The changes in scattering were frequent and could be due to the increased traffic from the end of the Thanksgiving holiday.