Analysis of In-situ Precipitation Measurement across Four sites near the Ross Ice Shelf of Antarctica for Identification of Snowfall Events

Analysis of In-situ Precipitation Measurement across Four sites near the Ross Ice Shelf of Antarctica for Identification of Snowfall Events

Rahul Kar ^(1,2), Scott Landolt ⁽²⁾ and Mustafa Aksoy ⁽¹⁾

(1) Electrical and Computer Engineering, University at Albany-State University of New York, Albany NY 12222, USA

(2) Research Applications Laboratory, National Center for Atmospheric Research, Boulder CO 80301, USA

In-situ measurements of precipitation across the Antarctic continent are extremely difficult due to the extreme weather conditions. With the onset of climate change, the Antarctic Icesheets have been melting but little information is available on the accumulation of snow to offset this loss. The Antarctic precipitation measurement project, an NSF-funded collaborative effort between CU Boulder and the NSF National Center for Atmospheric Research, deployed sensors at four different sites across the Ross Ice shelf between November 2017 and November 2019. OTT Pluvio2 precipitation gauges were installed along with other sensors such as a sonic ranging “snow depth” sensor and a GPS Interferometric (GPS-IR) sensor for measuring the snow height. Additional instrumentation for wind speed and temperature measurement, field cameras, an ETI Optical Particle Detector (OPD), and a Parsivel laser disdrometer were also available. A study was developed to assess snow accumulation events focused on a few months of early 2019, which is during the summer and early fall in Antarctica. After post processing and quality control measures, analysis of the OPD count data and the Pluvio2 data each month allowed for identification of all the events where an increase in the Pluvio2 data coincided with an increase in the OPD count to establish accumulation events. Additional time series plotting of the monthly precipitation data, snow depth data (from both the sonic sensor and GPS-IR sensor), and wind speed, events were analyzed to assess where snow could have been blown away due to high wind speeds, thereby leading to a deficit in accumulation observed by the snow depth sensor. The disdrometer was installed at a height of the opening of the precipitation gauge to capture snow particle count and size for better distinguishing between precipitating and blowing snow. The snow grain radius of the snow particles, along with the particle count from the disdrometer data for the sites where it was available were analyzed. The OPD count data and particle count data from the disdrometer were also compared to distinguish between the events of blowing snow and/or precipitating snow as the OPD can help assess both types of events, as it was installed much closer to the ground. Using the Pluvio2 data and the snow depth data (from both sonic ranging sensor and GPS-IR sensor), each individual event of snow accumulation was determined, and the density of the snow during those snow events was calculated to validate with the typical snow densities of freshly falling snow (50-100 kg/m³), which helps in distinguishing the fresh precipitating snow from the snow which was already there. All these direct in-situ measurements of Antarctic precipitation provide a wider insight and understanding of the snow accumulation events across the different sites.