Two areas of the US are showing Code Red conditions, one in Alabama which is under cloud and the other is the predictable problem in the San Joaquin Valley. The MODIS RGB image shows a noticeable haze in the valley which by the afternoon has thinned out. This is clearly the low intense layer of haze which fogs the valley in evening and morning hours. The Aerosol Optical Depth does not reach values which should be about 1 or greater for these surface aerosol amount, except that the haze is only a few hundred meters thick. Below the spaceborne image, AIRNOW shows the hazardous levels of PM2.5 in the valley. Remember that the limit now is 35 µg m-3 over an eight hour period.
And in a remarkable image from space, the Terra RGB this morning shows the low cloud over Lake Ontario, Toronto, and the Niagara Peninsula. For those of you who don't know the geography, the line at the southern edge of the clouds is the Niagara escarpment and forms a 100m drop off which Niagara Falls goes over. South of that line, clear air was evident in southern Ontario and Northern New York. An interesting big of micrometeorology.
Update Dec 29, 2013
Not much changes on Sunday and the poor air quality in California and Alabama continue. In Alabama, the high PM2.5 is only in Montgomery so one can be skeptical about a misfunctioning monitor. Webcams in the area do not seem to show these elevated levels of PM2.5.
In California, however, haze continues to hug the lower San Joaquin valley and there is a slight sign of respite from the high PM2.5 levels in Bakersfield starting Sunday afternoon.