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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
- Description:
- The Differential Emissivity Imaging Disdrometer (DEID) is a new evaporation-based optical and thermal instrument designed to measure the mass, size, density, and type of individual hydrometeors and their bulk properties. Hydrometeor spatial dimensions are measured on a heated metal plate using an infrared camera by exploiting the much higher thermal emissivity of water compared with metal. As a melted hydrometeor evaporates, its mass can be directly related to the loss of heat from the hotplate assuming energy conservation across the hydrometeor. The heat-loss required to evaporate a hydrometeor is found to be independent of environmental conditions including ambient wind velocity, moisture level, and temperature. The difference in heat loss for snow versus rain for a given mass offers a method for discriminating precipitation phase. The DEID measures hydrometeors at sampling frequencies up to 1 Hz with masses and effective diameters greater than 1 µg and 200 µm, respectively, determined by the size of the hotplate and the thermal camera specifications. Measurable snow water equivalent (SWE) precipitation rates range from 0.001 to 200 mm h−1, as validated against a standard weighing bucket. Preliminary field-experiment measurements of snow and rain from the winters of 2019 and 2020 provided continuous automated measurements of precipitation rate, snow density, and visibility. Measured hydrometeor size distributions agree well with canonical results described in the literature. and A new precipitation sensor, the Differential Emissivity Imaging Disdrometer (DEID), is used to provide the first continuous measurements of the mass, diameter, and density of individual hydrometeors. The DEID consists of an infrared camera pointed at a heated aluminum plate. It exploits the contrasting thermal emissivity of water and metal to determine individual particle mass by assuming that energy is conserved during the transfer of heat from the plate to the particle during evaporation. Particle density is determined from a combination of particle mass and morphology. A Multi-Angle Snowflake Camera (MASC) was deployed alongside the DEID to provide refined imagery of particle size and shape. Broad consistency is found between derived mass-diameter and density-diameter relationships and those obtained in prior studies. However, DEID measurements show a generally weaker dependence with size for hydrometeor density and a stronger dependence for aggregate snowflake mass.
- Keyword:
- multi-angle snowflake camera, differential emissivity imaging disdrometer, snow, density , mass, disdrometer, DEID, MASC, hydrometeors, and atmospheric science
- Subject:
- Atmospheric Science
- Creator:
- Rees, Karlie N., Pardyjak, Eric R., Garrett, Timothy J., and Singh, Dhiraj K.
- Contributor:
- Blackmer, Alex, Donovan, Spencer, Reaburn, Allan, and Roper, Peter
- Owner:
- Karlie Rees
- Based Near Label Tesim:
- Red Butte Canyon, Utah, United States
- Language:
- English
- Date Uploaded:
- 08/18/2021
- Date Modified:
- 12/08/2023
- Date Created:
- 2020-01-14 to 2020-02-06
- License:
- CC BY – Allows others to use and share your data, even commercially, with attribution.
- Resource Type:
- Software or Program Code and Dataset
- Identifier:
- https://doi.org/10.7278/S50D-SPT1-FNHH