Portrait of a Polluted Land

Annalee Newitz — Fri, 06 Nov 2009 16:25:29 PST

NASA's Aqua satellite captured this image of a massive smog bank smothering huge portions of China today. This blanket of pollution has been hovering over the country for over a week now, exacerbated by cool air and smoke from fires.

According to NASA, whose researchers first wrote about this lingering smog bank on Oct. 30:

A temperature inversion may be responsible for the build up of pollution over eastern China. Normally, air cools with altitude, but occasionally, a layer of cool air will be trapped beneath a layer of warm air. Since the cool air is more dense than the air above it, the two layers don't mix and pollutants build up in the cool air near Earth's surface.

Temperature inversions develop most often during the winter, when long, cool nights chill the ground. The cold land cools the air nearest the ground, leaving the air at higher altitudes warmer. The two layers of air do not easily mix, and the temperature inversion can last for days if winds are calm.

So far it has lasted for more than a week. Is this the future of weather?

via NASA

Beneath the Sulfurous Skies

Annalee Newitz — Wed, 06 Aug 2008 07:00:00 PDT

Nothing like a stark data visualization to impress upon you just how bad pollution has gotten in Beijing. Here you can see the levels of sulfur in the air over the past several years in three similarly-sized regions of the world: on the far left is the U.S. midwest, the middle is eastern Europe, and the right is the Beijing region. Areas shaded red have the highest sulfur emissions. Created by researchers at the University of Maryland, Baltimore County, these images are a stark reminder that economic development is often accompanied by environmental degradation.

The New York Times' Dot Earth blog asked one of the researchers, Simon Carn, to interpret the satellite photos. Carn said:

The images clearly show the high SO2 emissions from sources in northeast China. China is the world’s largest SO2 emitter, mostly due to the burning of high-sulfur coal in its many coal-fired power plants, which lack the technology used in many other countries to remove sulfur from smoke stack emissions. The eastern Europe image shows a few SO2 ‘hot spots’ in Romania, Bulgaria, Greece and Turkey - these are probably also power plants or metal smelters. The hot spot in Sicily is the active volcano Mt Etna - volcanoes are probably the second largest source of SO2 after anthropogenic emissions.

The main region of elevated SO2 in the USA image is the Ohio Valley and SW Pennsylvania, where there is a high concentration of coal-fired power plants (shown as diamond symbols on the image).

The significance of SO2 (apart from as a component of acid rain) is that it is a precursor of sulfate aerosol (sulfuric acid droplets), which is the main ingredient of the haze often seen in polluted regions. Sulfate aerosol is a health hazard, limits visibility, degrades buildings, reflects solar radiation (cooling the climate) and also impacts cloud properties (increasing their lifetime and reducing rainfall).

No word on how the Chinese cloud-seeding techniques to prevent rain during the Olympics are affecting any of this.

What Will Cure China's Sulfurous Skies? [Dot Earth]

io9: mega pollution

Portrait of a Polluted Land

Beneath the Sulfurous Skies