Multi-instrument “Forensic” Approach to Understanding NSA Winter Precipitation Events

 
Poster PDF

Authors

Jennifer S. Delamere — University of Alaska, Fairbanks
Matthew Sturm — University of Alaska, Fairbanks
Kenneth C Irving — University of Alaska, Fairbanks

Category

High-latitude clouds and aerosols

Description

Precipitation is one of the most significant processes in the Arctic atmosphere yet one of the most challenging to measure as wind-transported ground snow can appear to be a precipitation event. Over the past three years, the ARM program has expanded its suite of instruments to better quantify the relationship between snowfall and snow transport at its North Slope of Alaska observatory sites in Utqiagvik (formerly Barrow) and Oliktok Point. In 2016, laser precipitation monitors (LPMs) and Campbell snow depth sensors (SR50As) were deployed at both sites, with additional weighing bucket precipitation gauges (Geonor) as well. In 2018, additional instruments were added to the Utqiagvik facility to allow us to better elucidate the relationship between snowfall and snow transport. A three-dimensional ultrasonic anemometer for cold climates was deployed adjacent to the LPM; the vertical component of the wind velocity may be indicative of whether or not snow particles are falling through the LPM field-of-view for the first time or are being swept up from the ground. Two vertically-aligned FlowCapt sensors were installed to measure solid-particle mass flux and indicative wind-speed measurements--such measurements will yield quantitative information on the remobilization of material that has already been precipitated, become airborne, and once again fallen back to the surface. Additional snow depth sensors, manufactured by Judd, were installed as the SR50As were not reliable for the entirety of earlier winter season. Finally, AXIS dome cameras were installed at each site. Every 15 minutes the cameras cycle through a sequence of instrument and landscape views. These images are invaluable for many reasons, including assisting in the identification of snowfall versus snow transport events, snow bedforms under the snow-depth sensors, and of sensor-riming events that disrupt measurements. This poster will discuss forensic precipitation analyses of select events at both the NSA and OLI observatories using multiple lines of evidence. From these suite of measurements, we are, for the first time, able to separate true precipitation events from ground-snow transport events, as well as examine the time-dependent nature of the falling particle flux. Additionally, a short status report of the flow of this data through the ARM archive will be presented.