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Upcoming Seminars
| Title: | (TBD)
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| Speaker: |
Multiple
Student Intern Symposium
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| Date/Time: |
Tuesday, July 22, 2025 01:00 PM MDT (-0600)
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| Location: |
David Skaggs Research Center, Room GC402
Google Meet |
Abstract
Multiple
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| Title: | Where does snow become rain with atmospheric warming?
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| Speaker: |
Jen Kay
Dr. Jennifer Kay is an Professor with tenure in the Department of Atmospheric and Oceanic Sciences (ATOC) and a CIRES Fellow at the University of Colorado at Boulder. With her research group and scientific collaborators around the world, Dr. Kay works at the nexus of observations and modeling to connect physics-based models with observed cloud, precipitation, radiation, and sea ice processes.
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| Date/Time: |
Wednesday, July 23, 2025 01:00 PM MDT (-0600)
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| Location: |
David Skaggs Research Center, Room GC402
Google Meet |
Abstract
A sharp phase transition occurs when snow becomes rain in the atmosphere. When rain falls instead of snow, it decreases the land surface albedo, decreases land surface water storage, enhances ice sheet melt, and has impacts on human infrastructure. In this work, we assess this atmospheric snow-to-rain transition using high-frequency outputs from earth system models and spaceborne radar observations. To be conservative and focus on impactful precipitation events, we use the 275 K air temperature isotherm in the bottom atmospheric level during large (>5 mm/day, > 1 dBZ) precipitation events as a proxy for snow-to-rain transitions. Over Greenland, we find present-day rain observations consistent with rain are rare, occurring only along the coasts and during the summer. Applying warming alone we can constrain possible additional rain that could fall. We find rain doubles with 2.3 degrees C of near-surface warming. Next, we assess the snow-to-rain transition during the northern hemisphere water year (October to April). During the early 21st century, this isotherm spans 10 degrees of latitude. Starting at 44 degrees North in October, it moves equatorward to 34 degrees North in January/February and then returns poleward to 42 degrees North in April. Under ~3 degrees of global warming, the isotherm moves poleward by 4.4 degrees latitude (~500 km). The 21st poleward isotherm shift exceeds the climatological month-to-month isotherm migration, especially during the coldest months (January, February). Additional analysis is focused on geographic variations and on the sensitivity of these results to conditioning based on precipitation occurrence. Overall, these results provide new insights into where snow becomes rain during impactful atmospheric events.
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