Virga Detection Tool based on Micro Rain Radar in Arctic

Virga known as precipitation that fails to reach to the ground due to evaporation/sublimation beneath the cloud base. Virga is commonly observed in hot and arid regions where dry air helps in the process [1]. In a warming climate, virga is increasingly observed in cold environments such as Antarctica and Switzerland as sublimation of snow [2,3]. Virga precipitation constitutes occurrences over 30% in TRMM, GPM and 50% in Cloudsat in arid regions and accounts for 50% (30%) of false precipitation detections by TRMM (GPM) satellites. Virga plays a crucial role in quantifying total precipitation, particularly in remote regions like the Arctic where virga is poorly studied. Accurate identification of virga is essential to improve precipitation estimates derived from satellite radar observations, which are limited in Arctic regions. This study introduces the Arctic Virga Detection Algorithm (ArViDAM), which uses ground-based vertical precipitation observations from Micro Rain Radar (MRR) deployed at Ny-Ålesund (78° 55' N, 11° 56' E) in the Arctic to identify virga events based on reflectivity and fall velocity profiles up to 6 km.

Figure: (top) Time-height series profile of (a) Ze, (b) W, and (c) SW for 13th–14th June, 2020 includes virga and surface precipitation with detected virga height with black line. (bottom) Seasonal variation of occurrence of virga and surface precipitation during 2020-2023.

A summer event presented in Figure shows the sensibility of the ArViDAM with detected virga height on the time-height profile of reflectivity (Ze), fall velocity (W), and spectral width (SW) during 13th–14th June, 2020. ArViDAM outcomes from 2020–23 indicate that summer has the highest virga occurrence with∼40%, followed by spring and autumn with∼30% and winter with the lowest∼22%. The outcomes are expected to enhance understanding of Arctic precipitation processes and contribute to quantitative precipitation estimation. 

Keywords—Virga, Arctic Precipitation, Sublimation, Micro Rain Radar, Climate Change

 

References

 

[1] Wang, Y. You, and M. Kulie, “Global virga precipitation distribution derived from three spaceborne radars and its contribution to the false radiometer precipitation detection,” Geophysical Research Letters, vol. 45, no. 9, pp. 4446–4455, 2018. [Online]. Available: https://agupubs.onlinelibrary.wiley. com/doi/abs/10.1029/2018GL077891.

 

[2] N. Jullien, E. Vignon, M. Sprenger, F. Aemisegger, and A. Berne, “Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal ad´elie land in Antarctica,” The Cryosphere, vol. 14, no. 5, pp. 1685–1702, 2020. [Online]. Available: https://tc.copernicus.org/articles/14/1685/2020/. 

 

[3] R. Beynon and K. Hocke, “Snow virga above the swiss plateau observed by a micro rain radar,” Remote Sensing, vol. 14, no. 4, 2022. [Online]. Available: https://www.mdpi.com/2072-4292/14/4/890.