The researchers noted several unique phenomena across these overlapping scales of analysis.
From the ground stations, weather balloons, and radar measurements, they found areas of unexpected refreezing. Typical weather models for these locations predicted freezing rain; however, fully frozen ice pellets fell instead. The paper suggests that secondary ice crystals, like those observed in photos a and b, may have sped up this transformation.
The team also observed terrain-modified air flows from their doppler radars and weather balloons. These cold surface winds moved up the valley due to the surrounding topography, against the general wind pattern. These winds brought with them sub-zero temperatures that modified precipitation, in some cases contributing to the rapid refreezing they noted on the ground. At different times during the storm, these winds varied in intensity and location- causing shifting mixes of sleet and freezing rain across the valley.
For the researchers, the phenomena observed through their multiscale methodology brought as many new questions as answers. Why did this sudden refreezing occur during this storm? How did secondary ice crystals play in this ice pellet formation? Why did terrain-modified flows persist in some places and not in others? How can we use these observations to make weather forecasts better?
Thanks to this first paper, scientists are one storm closer to fully grasping the complexity of near-freezing precipitation. And as with all good things in science, the WINTRE-MIX experiment has inspired many new research questions. Best of all, it has provided a season’s worth of high-quality, open-source data with which to investigate them.
About the researchers
The WINTRE-MIX project is led by American researchers from University of Albany (Dr. Justin Minder and Dr. Nick Bassill), University of Wyoming (Dr. Jeffrey R. French and Dr. David Kingsmill), University of Colorado (Dr. Katja Friedrich, Dr. Andrew Winters), and the National Research Council (Dr. Leonid Nichman, Dr. Cuong Nguyen).
They collaborated with local scientists Dr. John Gyakum, Dr. Frédéric Fabry and Dr. Daniel Kirshbaum from the Atmospheric and Oceanic Sciences department of McGill University and Dr. Julie M. Thériault from UQAM (Université du Québec à Montréal).
Learn more about the WINTRE-MIX project by visiting their website or follow them on Twitter to get updates.
About the article
Minder, J. R., Bassill, N., Fabry, F., French, J. R., Friedrich, K., Gultepe, I., Gyakum, J., Kingsmill, D. E., Kosiba, K., Lachapelle, M., Michelson, D., Nichman, L., Nguyen, C., Thériault, J. M., Winters, A. C., Wolde, M., & Wurman, J. (2023). P-type Processes and Predictability: The Winter Precipitation Type Research Multiscale Experiment (WINTRE-MIX). Bulletin of the American Meteorological Society, 1(aop). https://doi.org/10.1175/BAMS-D-22-0095.1
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Header: Researchers Karel Veilleux (left) and Juliann Wray (right) are ready to launch their first meteorological sounding system of the night (photo: Alex Tran)