Using Citizens to Map Atmospheric Particulates

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Dutch researchers were able to successfully map levels of atmospheric particulates by pulling data from over 8,000 smartphone users.  A team from the University of Leiden in the Netherlands developed a smart-phone adaptor called an iSPEX.  This inexpensive, mass-producible add-on is attached to the front of the phone’s camera that enables it to function as a spectropolarimetric instrument.  Over the course of three different cloud-free days, users of those phones were able to collect data about atmospheric dust levels at a level of accuracy that at times exceed measurements from ground-based networks and satellite instruments.

The technology works by having participants attached the small iSPEX device to their phone’s camera.  On the selected days of the experiment, those users were instructed to scan the sky with the phone’s camera which then captured pictures and collected information about the the spectrum and the linear polarization of the sunlight that is scattered by suspended dust particles.

the iSPEX device for atmospheric particulate mapping.

the iSPEX device for atmospheric particulate mapping.

The data collected by citizen scientists was averaged and a map showing Aerosol Optical Thickness (AOT) was created for each of the three days.  The spatial resolution of the data collected via the ISPEX devices was two kilometers and offered a finer grained resolution than comparable satellite data.

iSPEX map compiled from all iSPEX measurements performed in the Netherlands on July 8, 2013, between 14:00 and 21:00. Each blue dot represents one of the total of 6007 measurements that were submitted that day. At each location on the map, the 50 nearest iSPEX measurements were averaged and converted to Aerosol Optical Thickness, a measure for the total amount of atmospheric particles. This map can be compared to the AOT data from the MODIS Aqua satellite, which flew over the Netherlands at 16:12 local time. The relatively high AOT values were caused by smoke clouds from forest fires in North America, that were blown over the Netherlands at an altitude of 2-4 km. In the course of the day, the northerly winds brought clearer air to the northern provinces.

iSPEX map compiled from all iSPEX measurements performed in the Netherlands on July 8, 2013, between 14:00 and 21:00. Each blue dot represents one of the total of 6007 measurements that were submitted that day. At each location on the map, the 50 nearest iSPEX measurements were averaged and converted to Aerosol Optical Thickness, a measure for the total amount of atmospheric particles. This map can be compared to the AOT data from the MODIS Aqua satellite, which flew over the Netherlands at 16:12 local time. The relatively high AOT values were caused by smoke clouds from forest fires in North America, that were blown over the Netherlands at an altitude of 2-4 km. In the course of the day, the northerly winds brought clearer air to the northern provinces.

The results of the research was recently published in the journal Geophysical Research Letters.  The future goal is to expand the project globally.   Frans Snik, the lead researcher explained, “Our final goal is to establish a global network of citizen scientists who all contribute measurements to study the sources and societal effects of polluting atmospheric particles.” 


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More information about the project can be found on the iSPEX page.

 


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