Operation Cloud Lab: Secrets of the Skies

In 2013, Dr Jim McQuaid took to the skies in an airship to find out what causes clouds – the result was last year’s BBC broadcast Operation Cloud Lab. We find out more about the project Ask someone in the high street where they might expect to find an analytical scientist, most will say, wearing a white coat in a lab, a few might mention CSI, well not this one! Most of my research involves flying around in research aircraft which is not entirely dissimilar to a lab with wings. In 2013 I got a phone call from a producer at the BBC who wanted to know what sort of instruments might be useful for a forthcoming project which was going to study clouds from an airship (the screened programme, entitled “Operation Cloud Lab: Secrets of the Skies” was broadcast in summer 2014). To a very small band of so-called cloud microphysicists this is literally like asking them the length of a piece of string! A few questions later, things became clearer, things like available space, power budget, speed and access to air outside helped to shorten the list to something a lot more manageable. The next major challenge was to locate our newly devised instrument wish list and persuade their keepers that it would be a good idea to loan them to the project! In the end this was surprisingly easy to do, what we proposed to do was to fly slowly across the southern states of America quite close to the surface, which held great appeal for the US scientists and companies I contacted. In general research projects are based in a single location and study a particular phenomenon, whereas our mission was to investigate the diversity of climates between the warm, humid Florida shores through the hot and arid dustiness of Texas, Arizona and New Mexico, finally nipping through a gap in the Rockies to the cool Pacific waters off the coast of California. So the Cloud Lab instrument suite took shape, first the basics, temperature, humidity and the like, followed by a cloud droplet probe. This uses light scattering to determine droplet diameter and a known sample volume means we can determine what we term the liquid water content. Beyond the cloud droplets themselves, we had instruments which target atmospheric particles (more commonly termed aerosols in the atmospheric community) these are critical in the formation of the cloud droplets. Needless to say, these come in a variety of ‘flavours’ which in turn require different approaches to their measurement. Soot is measured by firing a laser at it and following the incandescence as the particle heats up. Other aerosols are measured using their scattering properties. Biological aerosols are known to be extremely effective as the ‘seeds’ which accelerate cloud droplet formation. Biological aerosols can be detected by fluorescence following excitation by a xenon flash lamp. A LIDAR provided us with a remote sensing capability for detecting distant clouds and aerosols. In addition to the particulate instruments we installed spectrometers for carbon dioxide, methane, carbon monoxide, water vapour and ozone so that we could assess pollution levels alongside the aerosol. We used these instruments to illustrate many atmospheric properties including pollution making more and smaller cloud droplets than are generated in more pristine environments. Perhaps the most novel use of our flying lab was to weigh a cloud using the LIDAR to determine the volume of a cloud and our cloud droplet probe to determine the liquid water content. From this we discovered that even a small (1000 m long) cloud weighed 4 tonnes! Instrument list Cloud Droplets - http://dropletmeasurement.com/products/airborne/CDP-2 Bioaerosol - http://dropletmeasurement.com/products/ground-based/WIBS Soot - http://dropletmeasurement.com/products/airborne/SP2 Greenhouse gases - http://www.picarro.com/products_solutions/trace_gas_analyzers/co_co2_ch4_h2o Aerosol optical properties  - http://dropletmeasurement.com/products/airborne/PAX Ozone - http://www.twobtech.com/model_205.htm LIDAR - http://www.micropulselidar.com/ The author Dr Jim McQuaid is Director of Masters Education; Assoc. Prof of Atmospheric Composition in the School of Earth and Environment at University of Leeds.