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Oliktok Point, Alaska, United States
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- Description:
- Detailed ground-based observations of snow are scarce in remote regions such as the Arctic. Here, Multi-Angle Snowflake Camera (MASC) measurements of over 55,000 solid hydrometeors — obtained during a two-year period from August 2016 to August 2018 at Oliktok Point, Alaska — are analyzed and compared to similar measurements from an earlier experiment at Alta, Utah. In general, distributions of hydrometeor fall speed, fall orientation, aspect ratio, flatness, and complexity (i.e., riming degree) were observed to be very similar between the two locations, except that Arctic hydrometeors tended to be smaller. In total, the slope parameter defining a negative exponential of the size distribution was approximately 50% steeper in the Arctic as at Alta. 66% of particles were observed to be rimed or moderately rimed, with some suggestion that riming is favored by weak boundary layer stability. On average, the fall speed of rimed particles was not notably different from aggregates. However, graupel density and fall speed increase as cloud temperatures approach the melting point.
- Keyword:
- Oliktok Point, Alaska, hydrometeor fall orientation, Alta, fhydrometeor latness, snow, hydrometeor aspect ratio, hydrometeors, hydrometeor complexity, and hydrometeor fall speed
- Subject:
- Atmospheric Science
- Creator:
- Kyle E. Fitch and Timothy J. Garrett
- Owner:
- Based Near Label Tesim:
- Oliktok Point, Alaska, United States and Alta, Utah, United States
- Date Uploaded:
- 02/06/2022
- Date Modified:
- 12/06/2023
- Date Created:
- 2013-01-07 to 2013-04-22
- License:
- CC BY – Allows others to use and share your data, even commercially, with attribution.
- Resource Type:
- Dataset
- Identifier:
- https://doi.org/10.7278/S50d-0nmg-6bs4
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- Description:
- Thin boundary layer Arctic mixed-phase clouds are generally thought to precipitate pristine and aggregate ice crystals. Here we present automated surface photographic measurements showing that only 35\% of precipitation particles exhibit negligible riming and that graupel particles $\geq1\,\rm{mm}$ in diameter commonly fall from clouds with liquid water paths less than $50\,\rm{g\,m^{-2}}$. A simple analytical formulation predicts that significant riming enhancement can occur in updrafts with speeds typical of Arctic clouds, and observations show that such conditions are favored by weak temperature inversions and strong radiative cooling at cloud top. However, numerical simulations suggest that a mean updraft speed of $0.75\,\rm{m\,s^{-1}}$ would need to be sustained for over one hour. Graupel can efficiently remove moisture and aerosols from the boundary layer. The causes and impacts of Arctic riming enhancement remain to be determined.
- Subject:
- Atmospheric sciences, Computational research, and Arctic research
- Creator:
- Garrett, Timothy J. and Fitch, Kyle E.
- Contributor:
- Shkurko, Konstantin , Talaei, Ahmad, Gaustad, Krista, and Maahn, Maximilian
- Owner:
- BRIAN MCBRIDE
- Based Near Label Tesim:
- Oliktok Point, Alaska, United States
- Language:
- English
- Date Uploaded:
- 06/04/2020
- Date Modified:
- 07/21/2020
- Date Created:
- Code creation dates from 20161208 to 20180609 and Processed between 20170627 and 20190320
- Resource Type:
- Software or Program Code and Dataset
- Identifier:
- https://doi.org/10.7278/s50dva5jk2pd