5:15 PM - 7:15 PM
[MIS13-P02] Four-dimensional observation of natural snow using laser interferometry
Keywords:Crystal Growth, ice, In situ observation, Interferometer
Natural snow changes its geometry, such as platy, needle and column, depending on slight differences in temperature and humidity. In addition, characteristic patterns appear inside and outside the snowflake as a result of crystal growth. Ukichiro Nakaya showed the relationship between the geometry of snow and their formation environment (temperature and humidity) based on experiments on the growth of artificial snow in a low-temperature room, and the relationship is known as the Nakaya diagram. There are many studies on the reasons for the geometry of snow and the growth mechanisms so far [e.g., Sanchez et al. PNAS 114 (2017) 227; Brumberg et al., PNAS 114 (2017) 5349]. We went back to basics and brought laser interferometers and various optical microscopes to the base of Asahi-dake in the Taisetsu area, Hokkaido, Japan, where we observed snow crystals. We conducted in-situ observations of natural snow crystals and sublimation/regrowth experiments in an originally designed environment controllable cell.
We set up equipment in a handmade snow lab like an igloo and performed observations and experiments inside the lab. This snow lab has the ability to absorb sound and vibration, and to maintain humidity at nearly 100%, therefore it has greater characteristics than the latest laboratory in terms of observing snow.
We collected snow that had fallen at temperatures of -10 to -20°C directly onto a black felt surface, selected a single snowflake from it, and placed it on the tip of a glass rod with a diameter of 1.4 mm for observation using a laser interferometer. Here, we succeeded in simultaneously measuring the sublimation and regrowth rates in the thickness (1D) of a snow crystal in addition to the planar direction (2D). Adding the time variation (1D) means that we have carried out 4D observation. Here, the snow was placed in a controlled supersaturated environment in the environment controllable cell. The cell is equipped with a Peltier cooling unit, which has a water vapor source with a heater and a chromel-alumel thermocouple on top, windows for optical observation, capillary to handle a snow crystal and a platinum resistance temperature detector for temperature measurement of the cell.
Observations were carried out on a total of 28 nights over eight winter seasons between 2015 and 2025, except for the period of the coronavirus pandemic. More than 40 people have participated in the observations to see the beautiful geometry, symmetry, and diversity of snow crystals with their own eyes. In the presentation, we will mainly report on the results of the four-dimensional observation of natural snow using modified Mach–Zehnder-type interferometer.
Acknowledgments: We thank Y. Hirata, F. Saito and S. Mori of the Technical Division in the Institute of Low Temperature Science, Hokkaido University, for their help in the development of the experimental system and the snow lab. This study was supported partly by the Grant for Joint Research Program of the Institute of Low Temperature Science, Hokkaido University.
We set up equipment in a handmade snow lab like an igloo and performed observations and experiments inside the lab. This snow lab has the ability to absorb sound and vibration, and to maintain humidity at nearly 100%, therefore it has greater characteristics than the latest laboratory in terms of observing snow.
We collected snow that had fallen at temperatures of -10 to -20°C directly onto a black felt surface, selected a single snowflake from it, and placed it on the tip of a glass rod with a diameter of 1.4 mm for observation using a laser interferometer. Here, we succeeded in simultaneously measuring the sublimation and regrowth rates in the thickness (1D) of a snow crystal in addition to the planar direction (2D). Adding the time variation (1D) means that we have carried out 4D observation. Here, the snow was placed in a controlled supersaturated environment in the environment controllable cell. The cell is equipped with a Peltier cooling unit, which has a water vapor source with a heater and a chromel-alumel thermocouple on top, windows for optical observation, capillary to handle a snow crystal and a platinum resistance temperature detector for temperature measurement of the cell.
Observations were carried out on a total of 28 nights over eight winter seasons between 2015 and 2025, except for the period of the coronavirus pandemic. More than 40 people have participated in the observations to see the beautiful geometry, symmetry, and diversity of snow crystals with their own eyes. In the presentation, we will mainly report on the results of the four-dimensional observation of natural snow using modified Mach–Zehnder-type interferometer.
Acknowledgments: We thank Y. Hirata, F. Saito and S. Mori of the Technical Division in the Institute of Low Temperature Science, Hokkaido University, for their help in the development of the experimental system and the snow lab. This study was supported partly by the Grant for Joint Research Program of the Institute of Low Temperature Science, Hokkaido University.