Drops in a Cloud: An SBIR-funded spectrometer is at the forefront of global climate research

Weeks before the athletes took to the ice and snow at the 2018 Winter Olympics in South Korea, Dr. Duncan Axisa was in the mountains around PyeongChang, studying ice-forming particles. Later in the year, Axisa traveled to India to study monsoon clouds, and to France to participate in a trans-national ice-nucleation experiment. Axisa and his team travel around the globe to help scientists better predict the weather—specifically precipitation. Precipitation prediction is a difficult science, made more complicated by the varied composition of clouds, which affect their propensity to drop rain, ice or snow. But Axisa and his team had an advantage: a specialized, SBIR-funded instrument that can accurately measure not only the size of particles within a cloud but their shapes (important for discriminating between water and ice), as well as water content and atmospheric pressure and temperature.

Named CAPS (Cloud, Aerosol and Precipitation Spectrometer), the measurement device was developed in 1996 by Longmont, Colorado-based Droplet Measurement Technologies, LLC. (Droplet), with help from an SBIR contract from the Office of Naval Research. More than 20 years and several iterations later, the tool has become an industry standard, used in everything from climate change research to private sector studies on weather applications around the globe.

A few measurement campaigns later, Axisa, currently Droplet’s Director of Science Programs, and his team had all the data they needed. Their findings helped

scientists and meteorologists better predict precipitation and high impact weather. Axisa said the work they did with the CAPS globally demonstrated the power, versatility and ease-of-use of the instrument.

If anyone knows about particles and aerosols, it’s Axisa. He received his PhD in aerosol physics from the University of Denver, and, before joining Droplet, spent a decade with the National Center for Atmospheric Research (NCAR), based in Boulder, Colorado, where he helped various institutions (NASA, private industry and university groups among them) deploy research aircraft to study aerosol, clouds and precipitation. But his primary area of study is the potential impact of aerosols and clouds on climate change. While scientists have a strong understanding, based on years of research, of many of the various mechanisms of climate change, one question that until recently remained largely unanswered was exactly how particles affect the climate.

“It is still a hugely debated scientific question whether aerosol impacted clouds have a net positive warming effect on climate or a cooling effect,” Axisa said. “This question contributes to the largest uncertainty of our understanding of climate change.”

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