Preprints
https://doi.org/10.5194/amt-2023-148
https://doi.org/10.5194/amt-2023-148
18 Aug 2023
 | 18 Aug 2023
Status: this preprint is currently under review for the journal AMT.

Time-resolved measurements of the densities of individual frozen hydrometeors and of fresh snowfall

Dhiraj Kumar Singh, Eric Pardyjak, and Timothy Garrett

Abstract. It is a challenge to obtain accurate measurements of the microphysical properties of delicate, structurally complex, frozen and semi-frozen hydrometeors. We present a new technique for the real-time measurement of the density of freshly fallen individual snowflakes. A new thermal-imaging instrument, the Differential Emissivity Imaging Disdrometer (DEID), is shown through laboratory and field experiments to be capable of providing accurate estimates of individual snowflake and bulk-snow hydrometeor density (which can be interpreted as snow-to-liquid ratio or SLR). The method exploits the rate of heat transfer during the melting of a hydrometeor on a heated metal plate, which is a function of the temperature difference between the hotplate surface and the top of the hydrometeor. The product of the melting speed and melting time yields an equivalent particle thickness normal to the hotplate surface, which can then be used in combination with the particle mass and area on the plate to determine a particle density. Uncertainties in estimates of particle density are approximately 4 % based on calibrations with laboratory-produced particles made from water and frozen solutions of salt and water, and from field comparisons with both high-resolution imagery of falling snow and traditional snowpack density measurements obtained at 12-hour intervals. For 17 storms, individual particle densities vary from 19 to 495 kg m-3 and storm-mean snow densities vary from 40 to 100 kg m-3. We observe probability distribution functions for hydrometeor density that are nearly Gaussian with kurtoses of ≈ 3 and skewnesses of ≈ 0.01.

Dhiraj Kumar Singh, Eric Pardyjak, and Timothy Garrett

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2023-148', Anonymous Referee #1, 09 Oct 2023
    • AC1: 'Reply on RC1', Eric Pardyjak, 31 Jan 2024
  • RC2: 'Comment on amt-2023-148', Anonymous Referee #2, 31 Oct 2023
    • AC2: 'Reply on RC2', Eric Pardyjak, 31 Jan 2024
Dhiraj Kumar Singh, Eric Pardyjak, and Timothy Garrett
Dhiraj Kumar Singh, Eric Pardyjak, and Timothy Garrett

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Latest update: 18 Mar 2024
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Short summary
Accurate measurements of the properties of snowflakes are challenging to make. We present a new technique for the real-time measurement of the density of freshly fallen individual snowflakes. A new thermal-imaging instrument, the Differential Emissivity Imaging Disdrometer (DEID), is shown to be capable of providing accurate estimates of individual snowflake and bulk-snow hydrometeor density. The method exploits the rate of heat transfer during the melting of a snowflake on a hotplate.