Assessing the Relative Catch Efficiencies of the WMO-SPICE Double Fence Automated Reference with an Automated Bush Shielded Gauge at the Caribou Creek WMO-SPICE Intercomparison Site

Prior to the start of the current WMO Solid Precipitation Intercomparison Experiment (SPICE), the WMO secondary reference for the measurement of solid precipitation was the Double Fence Intercomparison Reference (DFIR) using a manually observed Tretyakov gauge. This reference gauge configuration was compared extensively to what was considered the primary reference which was the very same Tretyakov gauge installed within a bush shield where the bushes are trimmed to the same height as the gauge orifice. Unfortunately, the only location that hosted this intercomparison was in Valdai, Russia. For the current WMO SPICE project, with a focus on automated instruments, an automated reference is required. This reference configuration, called the Double Fence Automated Reference (DFAR) or R2 reference, has not previously been compared to a bush shielded gauge. Beginning in February 2013, the DFAR (with a Geonor automated gauge) is being compared to the bush shielded gauges (one Geonor and one Pluvio2) at the Caribou Creek SPICE intercomparison site located in the Canadian southern boreal forest (north of Prince Albert, Saskatchewan). The bush shielded gauges are sheltered by regenerating (2002 harvested) Jack Pine trees trimmed to gauge height while the DFAR is installed in a clearing with the top of the gauge at 3.5m and extending above the regenerating Jack Pine canopy. In theory, the DFAR should have a lower catch efficiency for snowfall than the bush shielded gauges due to exposure to higher wind speeds, allowing for the development of wind speed – catch efficiency relationships for the DFAR. The first complete field season for this intercomparison is ongoing and preliminary results will be presented.