Microphysics of Snowfall Over Coastal East Antarctica Simulated by Polar WRF and Observed by Radar

Vignon, Étienne; Bešič, Nikola; Jullien, Nicolas; Gehring, Josué; Berne, Alexis

doi:10.1029/2019jd031028

Cited by 34 publications

(43 citation statements)

References 89 publications

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“…As for the new ECMWF products, the polar WRF used in AMPS runs with a microphysics scheme based on five prognostic variables (WSM, Hong and others, 2004). Vignon and others (2019b) showed that polar WRF simulations, based on different state-of-the-art microphysical schemes, for two summertime precipitation events at DDU, show large discrepancies with respect to observations. Also, for results from MZS, some differences appear compared to the observations.…”

Section: Discussionmentioning

confidence: 99%

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

et al. 2020

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Knowledge of the precipitation contribution to the Antarctic surface mass balance is essential for defining the ice-sheet contribution to sea-level rise. Observations of precipitation are sparse over Antarctica, due to harsh environmental conditions. Precipitation during the summer months (November–December–January) on four expeditions, 2015–16, 2016–17, 2017–18 and 2018–19, in the Terra Nova Bay area, were monitored using a vertically pointing radar, disdrometer, snow gauge, radiosounding and an automatic weather station installed at the Italian Mario Zucchelli Station. The relationship between radar reflectivity and precipitation rate at the site can be estimated using these instruments jointly. The error in calculated precipitation is up to 40%, mostly dependent on reflectivity variability and disdrometer inability to define the real particle fall velocity. Mean derived summer precipitation is ~55 mm water equivalent but with a large variability. During collocated measurements in 2018–19, corrected snow gauge amounts agree with those derived from the relationship, within the estimated errors. European Centre for the Medium-Range Weather Forecasts (ECMWF) and the Antarctic Mesoscale Prediction System (AMPS) analysis and operational outputs are able to forecast the precipitation timing but do not adequately reproduce quantities during the most intense events, with overestimation for ECMWF and underestimation for AMPS.

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Section: Discussionmentioning

confidence: 99%

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

et al. 2020

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“…This type of precipitation system is typical for DDU (Jullien et al, 2020). The accumulated precipitation at the ground during the event was 3.4 mm (Vignon et al, 2019a).…”

Section: Application Of the Methodology To Two Case Studiesmentioning

confidence: 81%

“…Albeit intriguing, the thin upper layer of SUB visible around 3000 m between 28 December at 14:00 UTC and 29 December at 09:00 UTC is likely explained by a sub-saturated layer with respect to ice visible in the radiosoundings (not shown, see Fig. 2h from Vignon et al (2019a)).…”

Section: Illustration Of the Methodsmentioning

confidence: 93%

Identification of snowfall microphysical processes from vertical gradients of polarimetric radar variables

Planat¹,

Gehring²,

Vignon³

et al. 2020

Preprint

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Abstract. Polarimetric radar systems are commonly used to study the microphysics of precipitation. While they offer continuous measurements with a large spatial coverage, retrieving information about the microphysical processes that govern the evolution of snowfall from the polarimetric signal is challenging. The present study develops a new method, called Process Identification based on Vertical gradient Signs (PIVS), to spatially identify the occurrence of the main microphysical processes (aggregation and riming, crystal growth by vapor deposition, and sublimation) in snowfall from dual-polarization Doppler radar scans. We first derive an analytical framework to assess in which meteorological conditions the local vertical gradients of radar variables reliably inform about microphysical processes. In such conditions, we then identify regions dominated by (i) vapor deposition, (ii) aggregation and riming and (iii) snowflake sublimation and possibly snowflake breakup based on the sign of the local vertical gradients of the reflectivity ZH and the differential reflectivity ZDR. The method is then applied to data from two frontal snowfall events: one in coastal Adélie Land, Antarctica and one in the Taebaeck mountains in South Korea. The validity of the method is assessed by comparing its outcome with snowflake observations using a Multi-Angle Snowflake Camera and with the output of a hydrometeor classification based on polarimetric radar signal. The application of the method further makes it possible to better characterize and understand how snowfall forms, grows and decays in two different geographical and meteorological contexts. For the Antarctic case study, we show that crystal growth by vapor deposition dominates above 2500 m a.g.l., aggregation and riming prevail between 1500 and 2500 m a.g.l. and snowflake sublimation by low-level katabatic winds occurs below 1500 m a.g.l.. For the event in South Korea, aggregation and riming dominate between 4000 and 4800 m a.g.l., with local sublimation below and vapor deposition above. We infer some microphysical characteristics in terms of radar variables from statistical analysis of the method output (e.g. ZH and ZDR distribution for each process). We finally highlight the potential for extensive application to cold precipitation events in different meteorological contexts.

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“…As a first order approximation, we assume that the so called 'precipitating air parcels' in the ERA5 dataset are those for which the snow water content (SWC) vertical gradient in the column above DDU is significantly negative: dSW C/dz < SW C T where SW C T has been set to −1.5 10 −9 kg kg −1 m −1 after inspection of the distribution of dSW C/dz above DDU (not shown). The underlying reason is that if we neglect the advection -which is a reasonable hypothesis for Antarctic stratiform precipitation as the one over the Antarctic coast and given the ≈ 30 km horizontal resolution of ERA5 -a negative vertical gradient of SWC typically corresponds to a situation with auto-conversion of ice to snow or snowflake growth through vapor deposition, aggregation or riming (see Vignon et al, 2019a for examples above DDU). Examination of individual vertical profiles of SWC reveals that positive vertical gradients are almost always located in the katabatic layer, where sublimation occurs.…”

Section: Back-trajectories Of Precipitating Air Parcelsmentioning

confidence: 99%

Synoptic conditions and atmospheric moisture pathways associated to virga and precipitation over coastal Adélie Land in Antarctica

Jullien¹,

Vignon²,

Sprenger³

et al. 2019

Preprint

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Abstract. Precipitation falling over the coastal regions of Antarctica often experiences low-level sublimation within the dry katabatic layer. The amount of water that reaches the ground surface is thereby considerably reduced. This paper investigates the synoptic conditions and the atmospheric transport pathways of moisture that lead to either virga – when precipitation is completely sublimated – or actual surface precipitation events over coastal Adélie Land, East Antarctica. For this purpose, the study combines ground-based lidar and radar measurements at Dumont d'Urville station (DDU), Lagrangian back-trajectories, Eulerian diagnostics of extratropical cyclones and fronts as well as moisture source estimations. It is found that precipitating systems at DDU are associated with warm fronts of cyclones that are located to the west of Adélie Land. Virga – corresponding to 36 % of the hours with precipitation above DDU – and surface precipitation cases are associated with the same precipitating system but they correspond to different phases of the event. Virga cases more often precede surface precipitation. They sometimes follow surface precipitation in the warm sector of the cyclone's frontal system, when the associated cyclone has moved to the east of Adélie Land and the precipitation intensity has weakened. On their way to DDU, the air parcels that ultimately precipitate above the station experience a large-scale lifting across the warm front. The lifting generally occurs earlier in time and farther from the station for virga than for precipitation. It is further shown that the water contained in the snow falling above DDU during pre-precipitation virga has an oceanic origin farther away (about 30° more to the west) from Adélie Land than the one contained in the snow that precipitates down to the ground surface.

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Microphysics of Snowfall Over Coastal East Antarctica Simulated by Polar WRF and Observed by Radar

Cited by 34 publications

References 89 publications

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

Identification of snowfall microphysical processes from vertical gradients of polarimetric radar variables

Synoptic conditions and atmospheric moisture pathways associated to virga and precipitation over coastal Adélie Land in Antarctica

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