Meteorology meets Metrology: Climate research high up in the clouds

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 Barely has the research aircraft HALO entered the kilometre-high clouds towering above the Brazilian rainforest than the researchers find themselves in a complete haze, but they can rely on the measuring instruments that are working at full capacity. HAI - a new, highly accurate hygrometer of the Physikalisch-Technische Bundesanstalt (PTB) - is aboard. The shooting star among hygrometers has been developed only recently by metrologists (metrology = the science of measurement) especially for use on board aircraft and in the clouds, but it has already been used in four research campaigns and has already clocked up more than 300 hours of active use. It is the only device worldwide that can determine precisely and simultaneously how much of the water present in the atmosphere is in the form of vapour, condensation, droplets or ice. These data help us understand natural and anthropogenic cloud formation processes and how they influence the climate. HAI is robust enough for field use at strongly varying temperatures and pressures and it is also coupled to the international humidity scale. Furthermore, it requires no time-consuming calibration. Its unique features combine applied climate research with metrology's most demanding requirements.

 

http://www.ptb.de/en/aktuelles/archiv/presseinfos/pi2014/pitext/pi141202.html