image: Ceilometers are traditionally used to measure the height of the lowest layer of clouds in a convenient way. However, a newer ceilometer model that was recently introduced has a built-in function that allows it to distinguish between ice and liquid clouds across multiple cloud layers. Researchers recently validated this new capability in a comparative study in northern Japan, paving the way to a better understanding of the effects of clouds in the context of climate change. view more
Credit: Jun Inoue from National Institute of Polar Research, Japan
The more we learn about climate systems, the more we realize that we are barely scratching the surface. Recent studies have revealed intricate links between seemingly unrelated phenomena, such as how changes in ocean winds and wave height can increase the organic matter that changes cloud properties and alter their optical properties. Unfortunately, our understanding of climate systems in the polar regions, which are the most vulnerable to global warming, are rather limited owing to a general lack of data.
In general, climate models can poorly represent the effects of the phase of clouds, particularly in polar regions. Liquid clouds, which are composed mostly of suspended water droplets, scatter and reflect much more solar radiation than ice clouds, in which the liquid droplets have merged and solidified into larger ice particles. However, accurately measuring the phase of multiple cloud layers is challenging and costly, and climatologists are somewhat in the dark as to how much global warming affects cloud phase and vice-versa in polar regions.
To address this problem, a pair of Japanese researchers from the National Institute of Polar Research and Kitami Institute of Technology have been trying out a new tool for conducting measurements of cloud phase in a convenient way. As explained in their latest paper published in Polar Science, the researchers sought to test the ability of a new lidar ceilometer called the Vaisala CL61 to gather much-needed data on clouds in polar regions.
So what is a lidar ceilometer and why is this new model more useful than previous ones? A lidar ceilometer is a portable instrument that shoots a laser beam up into the sky and captures the portion of the laser reflected back down by the clouds. While they are typically used to determine how high the cloud base is, the new ceilometer tested in this study offers an additional functionality. Thanks to its higher beam power and a built-in depolarization function, the CL61 ceilometer can be used to distinguish between solid and liquid particles, which in turn provides information about cloud phase.
Motivated by these new capabilities, the researchers carried out measurements with the new ceilometer in northern Japan and compared them with measurements taken using a cloud particle sensor (CPS) sonde. The CPS sonde is a balloon-launched device that can very accurately determine cloud phase it passes through as it rises. Compared to a ceilometer, however, CPS sonde measurements are more time-consuming and expensive for long-term operational use. The researchers also compared the measurements of the new ceilometer with those of an older model without the depolarization function.
Overall, the new ceilometer was able to accurately measure the vertical distribution of cloud phases across multiple cloud layers with good sensitivity to cloud water content. Associate Professor Jun Inoue of the National Institute of Polar Research, lead author of the study, remarks on the importance of this comparative analysis on the latest cloud observation equipment. “The long-term data acquisition by this new ceilometer will be crucial for understanding the relationship between changes in clouds and climate,” he states, “Making visible the response of cloud phase to rapid changes in climate systems will hopefully make people think more about how to act under the current global warming scenario.”
Besides climate science, the new features of this new ceilometer could be useful in other practical applications in the short-term. “This new ceilometer could be used to estimate the probability of icing on aircrafts in supercooled liquid clouds,” explains Associate Professor Inoue, “Additionally, it could also be used to measure aerosols. By detecting the sphericity and relative amount of aerosol particles, their type can be inferred, which could be helpful to identify threats to human health in urban areas.”
In any case, this study made it clear that there is much untapped potential in the novel capabilities of modern ceilometers. With any luck, their increased use in polar climate science will let us prepare better for the consequences of global warming.
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About National Institute of Polar Research, Japan
The National Institute of Polar Research (NIPR) engages in comprehensive research via observation stations in Arctic and Antarctica as a member of the Research Organization of Information and Systems (ROIS). It provides researchers throughout Japan and other countries with infrastructure and support for polar observations and works actively to promote polar science. By working under the same frameworks as various international academic organizations, NIPR is the core Japanese representative institution operating in both poles, conducting cutting-edge research on polar ecosystems, polar climate science, geology, sustainability in polar regions, and more.
Website: https://www.nipr.ac.jp/english/index.html
About Associate Professor Jun Inoue from National Institute of Polar Research, Japan
Dr. Jun Inoue has been with NIPR since 2012 and currently serves there as Associate Professor. He obtained his master’s and PhD degrees from Hokkaido University, Japan, in 1999 and 2001, respectively. His research interests lie in the fields of atmospheric and hydrospheric science, particularly in the Arctic and Antarctic regions. He has published over 100 papers on these topics and has received awards from the Japan Meteorological Society on three occasions.
About the Research Organization of Information and Systems (ROIS)
ROIS is a parent organization of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROIS's mission to promote integrated, cutting-edge research that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.
Journal
Polar Science