A team of scientists from the Laboratoire Atmosphères, Milieux, Observations Spatiales claim to have found a way to quantify concentrations of carbon monoxide, sulfur dioxide and ammonia levels in the atmosphere using satellite images acquired by IASI infrared sounder.
Their dataset for the study was collected over Beijing and the nearby areas, and the results from the analyses appeared last week in the online edition of the journal Geophysical Research Letters. The authors believe that their findings could significantly contribute to the improvement of air pollution monitoring systems.
IASI-B sounders collect infrared data and provide it comercially since January 2013. The team decided to use images from this instrument in order to test its suitability for air pollution monitoring. They were able to detect a boundary layer pollution, which serves as an indicator for increased levels of toxic chemicals in the atmosphere and claim to have found a fast and effective way to monitor chemical concentrations.
Unfortunately, as most of these studies that use satellite data for detecting any type of chemicals, there are assumptions and/or conditions for the study to work. In this case, the scientists found that in order to get meaningful values, the weather should be stable, meaning no air-circulation, and there should be a significant difference between the ground surface temperature and the air. Both of these conditions mean that the pollution levels should be already very high in order to be detected, as they are during pollution episodes, for example. The former rule indicates that the chemicals should have built-up already, while the latter indicates that the molecules should be dense enough to prevent the light from hitting the surface.
But if I am to be very critical about this, the method that the team provided does not quantify concentrations. At best, the scientists could be able to detect the chemicals when they are above certain levels, and as the above conditions suggest, these levels should already be quite high before the satellite could provide meaningful data.
So if this is the case, wouldn’t we be able to note the high concentrations only by trying to look through the fog? I would think that if the pollution episode, as the one that occurred earlier this year in Beijing, should already have occurred before this technique can be put into work, we do not really require an expensive satellite image or complicated analysis to figure out that we cannot see further than 5 meters or have difficulties breathing because of the toxic smog.
An early warning system, this is what we should aim to develop, not a method that states the obvious, and unfortunately satellites cannot yet provide us with this, considering the gap between revisit times and current lack of real-time data (‘current’ because of Google’s plans to change this and everything). Just a thought.
Image (c) Geophysical Research Letters