Scientists at the US National Oceanic and Atmospheric Administation (NOAA) have embarked on a month-long study of the chemistry of cold winter air near the Rocky Mountains. The atmosphere in winter is made up of layers that don’t mix well, so sampling the air at ground level doesn’t tell the whole story. To get round the problem, the researchers have installed a ‘tower laboratory’ that carries more than a tonne of instrumentation up and down a 300 metre tower, analysing the chemistry at different heights.
The central question the team is tackling is why and how nitryl chloride, which is usually associated with the atmosphere near oceans, forms at night during the winter in land-locked regions like the foothills of the Rocky Mountains.
Nitryl chloride breaks apart quickly as the sun rises, releasing chlorine that reacts with other air-borne compounds to generate smog. Alongside smog formation, the release of chlorine can influence chemical cycles that destroy or produce various greenhouse gases including ozone and methane.
The researchers will be trying to pin down the source of nitryl chloride in the air – likely suspects include wood burning, pollution from power plants and road de-icing chemicals.