Preprints
https://doi.org/10.5194/hess-2020-553
https://doi.org/10.5194/hess-2020-553

  26 Nov 2020

26 Nov 2020

Review status: this preprint is currently under review for the journal HESS.

Unshielded precipitation gauge collection efficiency with wind speed and hydrometeor fall velocity. Part I: modelling results

Jeffery Hoover1, Pierre E. Sullivan2, Paul I. Joe1, and Michael E. Earle1 Jeffery Hoover et al.
  • 1Environment and Climate Change Canada, Toronto, ON, M3H 5T4, Canada
  • 2Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, M5S 3G8, Canada

Abstract. A new method for assessing collection efficiency using wind speed and hydrometeor fall velocity is presented for the unshielded Geonor T-200B3 precipitation gauge based on computational fluid dynamics results. Time-averaged Navier–Stokes simulations with a ke turbulence model were used to determine the airflow around the gauge for 0 to 10 m s−1 wind speeds. Hydrometeor trajectories and collection efficiencies were determined using Lagrangian analysis for spherical 10 hydrometeor fall velocities between 0.25 to 10 m s−1 for rain (0.01–3.9 mm diameter), wet snow (0.2–21 mm diameter), dry snow (0.2–7.1 mm diameter), and ice pellets (1.5–4.3 mm diameter). The model results demonstrate that gauge collection efficiency strongly depends on both wind speed and hydrometeor fall velocity. Collection efficiency differences for identical hydrometeor fall velocities are within 0.05 for wind speeds less than 4 m s−1, despite differences in hydrometeor type, diameter, density, and mass. An empirical expression for collection efficiency with dependence on wind speed and fall velocity is 15 presented based on the numerical results, giving a RMSE of 0.03 for dry snow, wet snow, and rain, for wind speeds between 0 and 10 m s−1. The use of fall velocity captures differences in collection efficiency due to different hydrometeor types and sizes, and can be broadly applied even where the precipitation type may be unknown or uncertain. Results are compared to previous models and good model agreement with experimental results is demonstrated in Part II.

Jeffery Hoover et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Login for authors/editors] [Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement

Jeffery Hoover et al.

Jeffery Hoover et al.

Viewed

Total article views: 314 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
249 62 3 314 5 5
  • HTML: 249
  • PDF: 62
  • XML: 3
  • Total: 314
  • BibTeX: 5
  • EndNote: 5
Views and downloads (calculated since 26 Nov 2020)
Cumulative views and downloads (calculated since 26 Nov 2020)

Viewed (geographical distribution)

Total article views: 295 (including HTML, PDF, and XML) Thereof 289 with geography defined and 6 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 19 Apr 2021
Download
Short summary
Using numerical simulations to examine the influence of wind speed and fall velocity on collection efficiency for unshielded precipitation gauges, a computationally cost-effective, universally applicable, and quantitative method is developed for adjusting unshielded precipitation gauge measurements for wind-induced undercatch. This method provides low RMSE values across liquid and solid precipitation types and can be broadly applied even where the precipitation type may be unknown or uncertain.