Convective Snowfalls Linked to the Interaction of a Boundary-Layer Front with a Mesoscale Cyclone Near Terra Nova Bay, Antarctica

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Genesis of diamond dust, ice fog and thick cloud episodes observed and modelled above Dome C, Antarctica

Abstract. Episodes of thick cloud and diamond dust/ice fog were observed during 15 March to 8 April 2011 and 4 to 5 March 2013 in the atmosphere above Dome C (Concordia station, Antarctica; 75°06′ S, 123°21′ E; 3233 m a.m.s.l.). The objectives of the paper are mainly to investigate the processes that cause these episodes based on observations and to verify whether operational models can evaluate them. The measurements were obtained from the following instruments: (1) a ground-based microwave radiometer (HAMSTRAD, H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers) installed at Dome C that provided vertical profiles of tropospheric temperature and absolute humidity every 7 min; (2) daily radiosoundings launched at 12:00 UTC at Dome C; (3) a tropospheric aerosol lidar that provides aerosol depolarization ratio along the vertical at Dome C; (4) down- and upward short- and long-wave radiations as provided by the Baseline Surface Radiation Network (BSRN) facilities; (5) an ICE-CAMERA to detect at an hourly rate the size of the ice crystal grains deposited at the surface of the camera; and (6) space-borne aerosol depolarization ratio from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) platform along orbits close to the Dome C station. The time evolution of the atmosphere has also been evaluated by considering the outputs from the mesoscale AROME and the global-scale ARPEGE meteorological models. Thick clouds are detected during the warm and wet periods (24–26 March 2011 and 4 March 2013) with high depolarization ratios (greater than 30 %) from the surface to 5–7 km above the ground associated with precipitation of ice particles and the presence of a supercooled liquid water (depolarization less than 10 %) clouds. Diamond dust and/or ice fog are detected during the cold and dry periods (5 April 2011 and 5 March 2013) with high depolarization ratios (greater than 30 %) in the planetary boundary layer to a maximum altitude of 100–300 m above the ground with little trace of precipitation. Considering 5-day back trajectories, we show that the thick cloud episodes are attributed to air masses with an oceanic origin whilst the diamond dust/ice fog episodes are attributed to air masses with continental origins. Although operational models can reproduce thick cloud episodes in the free troposphere, they cannot evaluate the diamond dust/ice fog episodes in the planetary boundary layer because they require to use more sophisticated cloud and aerosol microphysics schemes

Analysis of multi-year near-surface ozone observations at the WMO/GAW "Concordia" station (75°06′S, 123°20′E, 3280 m a.s.l. – Antarctica)

Abstract This work focuses on the near-surface O3 variability over the eastern Antarctic Plateau. In particular, eight years (2006–2013) of continuous observations at the WMO/GAW contributing station "Concordia" (Dome C–DMC: 75°06′S, 123°20′E, 3280 m) are presented, in the framework of the Italian Antarctic Research Programme (PNRA). First, the characterization of seasonal and diurnal O3 variability at DMC is provided. Then, for the period of highest data coverage (2008–2013), we investigated the role of specific atmospheric processes in affecting near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DMC (average monthly frequency peaking up to 60% in December). As deduced by a statistical selection methodology, these OEEs are affected by a significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed OEEs as a function of specific atmospheric variables and processes: (i) total column of O3 (TCO) and UV-A irradiance, (ii) long-range transport of air masses over the Antarctic Plateau (by Lagrangian back-trajectory analysis – LAGRANTO), (iii) occurrence of "deep" stratospheric intrusion events (by using the Lagrangian tool STLEFLUX). The overall near-surface O3 variability at DMC is controlled by a day-to-day pattern, which strongly points towards a dominating influence of processes occurring at "synoptic" scales rather than "local" processes. Even if previous studies suggested an inverse relationship between OEEs and TCO, we found a slight tendency for the annual frequency of OEEs to be higher when TCO values are higher over DMC. The annual occurrence of OEEs at DMC seems related to the total time spent by air masses over the Antarctic plateau before their arrival to DMC, suggesting the accumulation of photochemically-produced O3 during the transport, rather than a more efficient local production. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusion events by STEFLUX suggested only a minor influence (up to 3% of the period, in November) of "deep" events on the variability of near-surface summer O3 at DMC

Extraordinary blowing snow transport events in East Antarctica

In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. Snow transport observations from instruments and satellite images were acquired at the wind convergence zone of Terra Nova Bay (East Antarctica) throughout 2006 and 2007. Snow transport features are well-distinguished in satellite images and can extend vertically up to 200 m as first-order quantitatively estimated by driftometer sensor FlowCapt™. Maximum snow transportation occurs in the fall and winter seasons. Snow transportation (drift/blowing) was recorded for ~80% of the time, and 20% of time recorded, the flux is >10-2 kg m-2 s-1 with particle density increasing with height. Cumulative snow transportation is ~4 orders of magnitude higher than snow precipitation at the site. An increase in wind speed and transportation (~30%) was observed in 2007, which is in agreement with a reduction in observed snow accumulation. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value. © 2009 The Author(s)

Endoscopic endonasal resection of adenoid cystic carcinoma of the sinonasal tract and skull base

Adenoid cystic carcinoma (ACC) is a locally aggressive salivary gland malignancy prone to perineural invasion and local recurrences. In the literature, few data exist to guide treatment when this tumor involves the paranasal sinuses and skull base. We report our experience in the management of sinonasal adenoid cystic carcinoma through an endoscopic endonasal approach

Could we find any signal of the stratosphere-ionosphere coupling in Antarctica?

An investigation searching for a possible coupling between the lower ionosphere and the middle atmosphere in Antarctica is here performed on the basis of stratospheric vertical temperature profiles and ionospheric absorption data observed at the Antarctic Italian Base of Terra Nova Bay (74.69°S, 164.12°E) during local summer time. The result obtained by applying a multi-regression analysis and a Superimposed Epoch Analysis (SEA) shows a statistically significant ionosphere-stratosphere interaction. In particular, by selecting stratospheric temperature maxima occurring at different heights as the referring epoch («zero day») for the SEA approach, the ionospheric absorption is found to show a positive and/or negative trend (several days) around it. The tendency for an increasing/decreasing absorption is obtained for temperature maxima occurring below/above the stratospheric level of about 17-19 km, respectively

Genesis of Diamond Dust and Thick Cloud Episodes observed above Dome C, Antarctica

<p><strong>Abstract.</strong> From 15 March to 8 April 2011 and from 4 to 5 March 2013, the atmosphere above Dome C (Concordia station, Antarctica, 75°06' S, 123°21' E, 3233 m amsl) has been probed by several instruments and model to study episodes of thick cloud and diamond dust (cloud constituted of suspended ice crystals). 1) A ground-based microwave radiometer (HAMSTRAD, H<sub>2</sub>O Antarctica Microwave Stratospheric and Tropospheric Radiometers) installed at Dome C that provided vertical profiles of tropospheric temperature and absolute humidity to calculate Integrated Water Vapour (IWV). 2) Daily radiosoundings launched at 12:00 UTC at Dome C. 3) A tropospheric aerosol Lidar that provides aerosol depolarization ratio along the vertical at Dome C. 4) Down- and upward short- and longwave radiations as provided by the Baseline Surface Radiation Network (BSRN) facilities. 5) Space-borne aerosol depolarization ratio from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Lidar aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) platform along orbits close to the Dome C station. The time evolution of the atmosphere has also been evaluated by considering the outputs from the meso-scale AROME and the global-scale ARPEGE meteorological models. Two distinct periods are highlighted by all the datasets: the warm and wet periods (24–26 March 2011 and 4 March 2013) and the cold and dry periods (5 April 2011 and 5 March 2013). Combining radiation and active measurements of aerosols with nebulosity calculations, a thick cloud is detected during the warm and wet periods with high depolarization ratios (greater than 30 %) from the surface to 5–7 km altitude associated with precipitation of ice particles and the presence of a supercooled liquid water (depolarization of about 10 %) cloud. During the cold and dry periods, high depolarization ratios (greater than 30 %) to a maximum altitude of 100–500 m are measured suggesting that the cloud is constituted of ice crystals with no trace of precipitation. These ice crystals in suspension in the air are named diamond dust. Considering 5-day back trajectories from Dome C and global distributions of IWV over the Antarctic show that the thick-cloud episode is attributed to air masses with an oceanic origin whilst the diamond dust episode is attributed to air masses with continental origins. This is consistent with ARPEGE temperature and water vapour tendency favouring predominantly advection processes including microphysical processes for water vapour.</p&gt

Long Stent Implantation on the Left Anterior Descending Coronary Artery at a Follow-Up of More Than Five Years

Background: Stent implantation represents the standard of care in coronary intervention. While a short stent implanted on a focal lesion located on the left anterior descending artery (LAD) seems a reasonable alternative to an internal mammary implant, the same for long stents is still debated. Methods: We reported the long-term data of 531 consecutive patients who underwent Percutaneous Coronary Intervention (PCI) with long stents in two highly specialized centres. The main inclusion criteria were the implantation of stents longer than 30 mm on the LAD and a minimum follow-up (FU) of five years. The primary endpoint was mortality, and the secondary endpoints were any myocardial infarction (MI), target vessel and lesion revascularization (TVR and TLR, respectively), and stent thrombosis (ST) observed as definite, probable, or possible. Results: In this selected population with characteristics of complex PCI (99.1%), the long-term follow-up (mean 92.18 ± 35.5 months) estimates of all-cause death, cardiovascular death, and any myocardial infarction were 18.3%, 10.5%, and 9.3%, respectively. Both all-cause and cardiovascular deaths are significantly associated with three-vessel disease (HR 6.8; confidence of interval (CI) 95% 3.844–11.934; p &lt; 0.001, and HR 4.7; CI 95% 2.265–9.835; p &lt; 0.001, respectively). Target lesion (TLR) and target vessel revascularization (TVR) are associated with the presence of three-lesion disease on the LAD (HR 3.4; CI 95% 1.984–5.781; p &lt; 0.001; HR 3.9 CI 95% 2.323–6.442; p &lt; 0.001, respectively). Re-PCI for any cause occurred in 31.5% of patients and shows an increased risk for three-lesion stenting (HR 4.3; CI 95% 2.873–6.376; p &lt; 0.001) and the treatment of bifurcation with two stents (HR 1.6; 95% CI 1.051–2.414; p = 0.028). Stent thrombosis rate at the 5-year FU was 4.4% (1.3% definite; 0.9% probable; 2.1% possible), including a 1.7% rate of very-late thrombosis. The stent length superior to 40 mm was not associated with poor outcomes (all-cause death p = 0.349; cardiovascular death p = 0.855; MI p = 0.691; re-PCI p = 0.234; TLR p = 0.805; TVR p = 0.087; ST p = 0.189). Conclusion: At an FU of longer than five years, patients treated with stents longer than 30 mm in their LAD showed acceptable procedural results but poor outcomes.</p

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

AbstractKnowledge 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

Long Stent Implantation on the Left Anterior Descending Coronary Artery at a Follow-Up of More Than Five Years

Background: Stent implantation represents the standard of care in coronary intervention. While a short stent implanted on a focal lesion located on the left anterior descending artery (LAD) seems a reasonable alternative to an internal mammary implant, the same for long stents is still debated. Methods: We reported the long-term data of 531 consecutive patients who underwent Percutaneous Coronary Intervention (PCI) with long stents in two highly specialized centres. The main inclusion criteria were the implantation of stents longer than 30 mm on the LAD and a minimum follow-up (FU) of five years. The primary endpoint was mortality, and the secondary endpoints were any myocardial infarction (MI), target vessel and lesion revascularization (TVR and TLR, respectively), and stent thrombosis (ST) observed as definite, probable, or possible. Results: In this selected population with characteristics of complex PCI (99.1%), the long-term follow-up (mean 92.18 ± 35.5 months) estimates of all-cause death, cardiovascular death, and any myocardial infarction were 18.3%, 10.5%, and 9.3%, respectively. Both all-cause and cardiovascular deaths are significantly associated with three-vessel disease (HR 6.8; confidence of interval (CI) 95% 3.844–11.934; p &lt; 0.001, and HR 4.7; CI 95% 2.265–9.835; p &lt; 0.001, respectively). Target lesion (TLR) and target vessel revascularization (TVR) are associated with the presence of three-lesion disease on the LAD (HR 3.4; CI 95% 1.984–5.781; p &lt; 0.001; HR 3.9 CI 95% 2.323–6.442; p &lt; 0.001, respectively). Re-PCI for any cause occurred in 31.5% of patients and shows an increased risk for three-lesion stenting (HR 4.3; CI 95% 2.873–6.376; p &lt; 0.001) and the treatment of bifurcation with two stents (HR 1.6; 95% CI 1.051–2.414; p = 0.028). Stent thrombosis rate at the 5-year FU was 4.4% (1.3% definite; 0.9% probable; 2.1% possible), including a 1.7% rate of very-late thrombosis. The stent length superior to 40 mm was not associated with poor outcomes (all-cause death p = 0.349; cardiovascular death p = 0.855; MI p = 0.691; re-PCI p = 0.234; TLR p = 0.805; TVR p = 0.087; ST p = 0.189). Conclusion: At an FU of longer than five years, patients treated with stents longer than 30 mm in their LAD showed acceptable procedural results but poor outcomes.</p