Colloquium, Friday, Sept. 11, 12:30pm, EN6085A (NOTE DIFFERENT DAY/TIME) (ical.ics)

This work presents an analysis of data from six wintertime precipitation (snow) sensors operated at the windy and forested Glacier Lakes Ecosystem Experiments Site (GLEES) located in the Medicine Bow Mountains of southeastern Wyoming. The research had two areas of focus: 1) the intercomparison of the six data sets, and 2) the investigation of the inadvertent registration of wind-resuspended ice particles as precipitation (blowing snow aliasing as snowfall).   The second objective was met by comparing surface-based snow precipitation measurement to a new type of precipitation sensor, the Hotplate, operated above the forest canopy on top of a 30 m tower.

There are two findings.   First, a comparison of precipitation measurements from the tower-based Hotplate and the surface-based Vaisala precipitation sensor (VRG) showed that during cold-season conditions the VRG measurement is positively biased relative to the Hotplate.   After accounting for a known bias in the Hotplate measurement (which decreases the positive bias), it is concluded that the VRG substantially exceeds the Hotplate.   Second, one of the surface-based National Atmospheric Deposition Program sensors, an Alter-shielded Belfort precipitation gauge, is also positively biased; by as much as a factor 1.6 relative to the Brooklyn Lake Snow Telemetry gauge (SNOTEL).  Both of these biases (VRG>Hotplate and NADP-gauge>SNOTEL gauge) are attributed to the enhanced registration of wind-redistributed ice particles by the overestimating gauge.