Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adélie Land, Antarctica

2020 ◽  
Author(s):  
Nicolas Jullien ◽  
Etienne Vignon ◽  
Michael Sprenger ◽  
Franziska Aemisegger ◽  
Alexis Berne
Keyword(s):  
Large Scale ◽  
Atmospheric Transport ◽  
Ground Surface ◽  
The West ◽  
Transport Pathways ◽  
Back Trajectories ◽  
Surface Precipitation ◽  
Actual Surface ◽  
Warm Front ◽  
Synoptic Conditions

<p>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. We investigate the synoptic conditions and the atmospheric transport pathways of moisture that lead to virga – when precipitation is completely sublimated – or actual surface precipitation at Dumont d’Urville (DDU) station, coastal Adélie Land, Antarctica. We combine ground-based radar measurements, Lagrangian back-trajectories, Eulerian diagnostics of extratropical cyclones and fronts as well as with moisture source estimations based on ERA5 reanalyses. Virga periods – corresponding to 36% of the precipitating events – often precede and sometimes follow surface precipitation periods. Pre-precipitation virga, surface precipitation and post-precipitation virga correspond to different phases of the same precipitating system. Precipitation and virga are always associated with the warm front of an extratropical cyclone that sets to the west of coastal Adélie Land but the exact locations of the cyclone and front differ between the three phases. 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 water contained in the precipitation falling above DDU during pre-precipitation virga has an oceanic origin farther away (30 degrees more to the west) from Adélie Land than the one that precipitates down to the ground surface.</p>

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

2019 ◽  
Author(s):  
Nicolas Jullien ◽  
Étienne Vignon ◽  
Michael Sprenger ◽  
Franziska Aemisegger ◽  
Alexis Berne
Keyword(s):  
Large Scale ◽  
Atmospheric Transport ◽  
Ground Surface ◽  
The West ◽  
Transport Pathways ◽  
Back Trajectories ◽  
Surface Precipitation ◽  
Actual Surface ◽  
Synoptic Conditions ◽  
Ground Based Lidar

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.

scholarly journals Synoptic conditions and atmospheric moisture pathways associated with virga and precipitation over coastal Adélie Land in Antarctica

2020 ◽  
Vol 14 (5) ◽  
pp. 1685-1702
Author(s):  
Nicolas Jullien ◽  
Étienne Vignon ◽  
Michael Sprenger ◽  
Franziska Aemisegger ◽  
Alexis Berne
Keyword(s):  
Large Scale ◽  
Atmospheric Transport ◽  
Ground Surface ◽  
The West ◽  
Transport Pathways ◽  
Back Trajectories ◽  
Surface Precipitation ◽  
Actual Surface ◽  
Synoptic Conditions ◽  
Ground Based Lidar

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, and 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.

Global age of air spectrum from the earth surface to the upper troposphere and tropopause: a model study

2020 ◽  
Author(s):  
Aurelien Podglajen ◽  
Edward Charlesworth ◽  
Felix Ploeger
Keyword(s):  
Time Scales ◽  
Atmospheric Chemistry ◽  
Large Scale ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Convective Transport ◽  
Transport Pathways ◽  
Upper Troposphere ◽  
Major Player ◽  
Interhemispheric Transport

<p>Transport of air masses from the surface into the atmosphere occurs via a variety of processes (including clear-air turbulence, atmospheric convection and large-scale circulations), which entails a multitude of transport time scales. This complexity can be characterized in an atmospheric transport model by calculating the age of air spectrum (transit time distribution from the surface). Up to now, mainly the slow time scales of stratospheric and interhemispheric transport (>10 days) have thus been studied. Vertical transport through the troposphere, for which convection is the major player, has only been evaluated using a handful of measured compounds (Radon, CO2 and SF6). However, a wealth of chemically relevant species are affected by the detailed structure of the age spectrum. Recent work (Luo et al., 2018) have used this sensitivity in order to gain observational insights into the tropospheric age spectrum, calling for a comparison with models.</p><p>To that end, we derive upper tropospheric and tropopause age spectra in the EMAC (ECHAM/MESSy Atmospheric Chemistry) model using the Boundary Impulse Response (BIR) method. Because of the large range of time scales involved in tropospheric transport, which extend from tens of minutes (convective transport) to years (stratospheric intrusions), we rely on a suite of pulses with variable durations providing hourly resolution for short time scales (< 12 hours) and monthly for long ones (> 1 month). We first describe the age spectra obtained and their diurnal and seasonal variability. Then, we examine the transport properties from a few specific surface regions to the upper troposphere and stratosphere, with an emphasis on fast pathways from the tropical Western Pacific and on interhemispheric transport. Finally, we investigate the sensitivity of different transport pathways to changes in some of the available model parameterizations (convection) and to different set-ups (using nudging or not).</p>

scholarly journals On the heat waves in Bangladesh, their trends and associated large scale tropospheric conditions

2020 ◽  
Vol 11 (1) ◽  
pp. 19-36
Author(s):  
Samarendra Karmakar ◽  
Mohan Kumar Das
Keyword(s):  
Large Scale ◽  
Heat Waves ◽  
Maximum Temperature ◽  
Chittagong Hill Tracts ◽  
The West ◽  
Southwestern Part ◽  
Synoptic Conditions ◽  
Annual Frequency ◽  
Upper Level ◽  
Increasing Trends

Attempts have been made to study the heat waves along with the trends in Bangladesh and the large-scale tropospheric conditions over Bangladesh and neighbourhood responsible for generating heat waves in the country. Maximum temperature (Tmax) for the period 1981-2016 has been used in the study. Based on the definition of heat waves of Bangladesh Meteorological Department (BMD), the frequencies of days with Tmax≥360C and ≥ 380C have been computed and their trends are investigated to delineate the areas of heat waves in Bangladesh. During the period 1981-2016, Tmax≥360C is found to prevail annually for 79 days at Rajshahi, 51 days at Mongla, 50 days at Khulna in 2014 whereas it is found to prevail annually for 85 days at Chuadanga in 1992, 78 days at Jessore in 2010, 72 days at Satkhira in 1986 and 68 days at Ishurdi in 1995. In 2014, Tmax≥360C is found to exist annually for many days in western pat of Bangladesh in comparison to the eastern and costal region of the country. That is why year 2014 has been selected to study waves extensively. The study reveals that the monthly, seasonal and annual frequency of Tmax≥360C have increasing trends in Bangladesh except a very few places, having the highest increasing trends over southwestern part of the country with increasing rates of 0.816 day/year and 1.02 day/year, respectively at Mongla. The highest increasing trends over southwestern part may be due to the advection and penetration of higher Tmax due to northwesterly winds and less rainfall over the area. The seasonal and annual frequencies of Tmax≥380C have increasing trends at less than 50% stations in Bangladesh; some of the increasing trends of the seasonal and annual frequency of maximum temperature ≥380C are statistically significant up to 95-99% level of significance. The large-scale synoptic conditions show that heat waves are found to enter Bangladesh from the west/northwest due to the advection of higher Tmax from the west. Heat waves extend from west to east up to about central Bangladesh and a separate area of heat waves develop over the Chittagong Hill Tracts, the reason of which may be due to the diverging pattern of wind flows near the Chittagong Hill Tracts in the year of heat waves. Heat waves are absent along Sandwip-M.Court-Feni-Comilla region. In 2014, heat waves are found to be due to the influence of sub-tropical high over India and its extension over Bangladesh at the surface and at 850 hPa level with strong westerly/northwesterly winds at 850 hPa, influence of anticyclones persisting for many days over the Bay of Bengal at 300 hPa level, absence of upper level westerly troughs over India and Bangladesh Journal of Engineering Science 11(1), 2020, 19-36

scholarly journals Synoptic Weather Types for the Ross Sea Region, Antarctica

2013 ◽  
Vol 26 (2) ◽  
pp. 636-649 ◽  
Author(s):  
Lana Cohen ◽  
Sam Dean ◽  
James Renwick
Keyword(s):  
Large Scale ◽  
Ross Sea ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Amundsen Sea ◽  
Transport Pathways ◽  
Local Climate ◽  
Synoptic Classification ◽  
Synoptic Conditions ◽  
Precipitation And Temperature

Abstract Synoptic classifications over the Southern Ocean in the Ross Sea region of Antarctica (50°S–Antarctic coast, 150°E–90°W) have been derived from NCEP reanalysis data (1979–2011), producing a set of six synoptic types for the region. These types describe realistic synoptic conditions for the region and represent the moisture-bearing low pressure systems that circulate around Antarctica. The types are described as follows: low Bellingshausen/Amundsen (L-BA), low (L), zonal (Z), low Ross (L-R), ridge (R), and low Amundsen (L-A). Seasonal frequencies of the synoptic types reflect the seasonal zonal shift of the Amundsen Sea low (ASL) and also correlate well with the Southern Oscillation index (SOI) and the southern annular mode (SAM). Variability in the occurrences of the synoptic types L-R and L-BA indicate a shifting of the position of the ASL farther east (west) toward (away from) the Antarctic Peninsula during La Niña (El Niño) and positive (negative) SAM conditions. A joint linear regression of the SOI and SAM indices show the strongest correlations with the types L-BA and L-R in the spring and quantifies the joint forcing effect of these climate cycles on synoptic variability in the region. As a demonstration of how synoptic classification provides links between large-scale atmospheric circulation and local climate parameters, the synoptic types are related to precipitation and temperature at Roosevelt Island, an ice core site on the Ross Ice Shelf (80°S, 160°W). The synoptic types provide quantification of distinct precipitation and temperature regimes at this site, which allows for more fundamental understanding of the precipitation source regions and transport pathways that drive the variability in snow and ice proxies.

scholarly journals Airmass Classification and Analysis of Aerosol Types at El Arenosillo (Spain)

2009 ◽  
Vol 48 (5) ◽  
pp. 962-981 ◽  
Author(s):  
C. Toledano ◽  
V. E. Cachorro ◽  
A. M. de Frutos ◽  
B. Torres ◽  
A. Berjón ◽  
...  
Keyword(s):  
Source Region ◽  
Receptor Site ◽  
Spectral Signature ◽  
Back Trajectory ◽  
Transport Pathways ◽  
Back Trajectories ◽  
Air Masses ◽  
Wide Range ◽  
Synoptic Conditions ◽  
Aerosol Types

Abstract The Aerosol Robotic Network (AERONET) site “El Arenosillo,” equipped with a Cimel sun photometer, has been in operation since 2000. The data collected there are analyzed to establish an aerosol synoptic climatological description that is representative of the region. Different air masses and aerosol types are present over the site depending on the synoptic conditions. The frequent intrusion of dust from the Sahara Desert at El Arenosillo suggested the use of back trajectories to determine the airmass origins of other types of aerosol observed there. The focus of this study is to classify the air masses arriving at El Arenosillo by means of back-trajectory analyses and to characterize the aerosol within each type by means of the aerosol optical depth (AOD) and its spectral signature, given as the Ångström exponent (AE). The goal is to determine how aerosols observed over the station (receptor site) differ depending on source region and transport pathways. Two classification methods are used, one based on sectors and a second based on cluster analysis. The period analyzed is from 2000 to 2004. Both methods show that maritime air masses are predominant, occurring 70% of the time and having relatively low AOD (≈0.1 at 440 nm) and a wide range of AE (from about 0 to 2.0). Air masses with continental characteristics are moderately turbid and have values of AE that average ≈1.4. Air masses arriving from the south and southwest show the distinct features of the desert dust, having moderate to high values of AOD (0.30–0.35 at 440 nm) and low values of AE.

scholarly journals Colonial management as a social field: The Palestinian remaking of Israel’s system of spatial control

2021 ◽  
pp. 001139212110246
Author(s):  
Walid Habbas ◽  
Yael Berda
Keyword(s):  
Large Scale ◽  
Central Component ◽  
Colonial Rule ◽  
Spatial Mobility ◽  
The West ◽  
Social Field ◽  
Spatial Control ◽  
Racial Hierarchy ◽  
Economic Elite ◽  
The Everyday

This article delves into the everyday dynamics of colonial rule to outline a novel way of understanding colonized–colonizer interactions. It conceives colonial management as a social field in which both the colonized and colonizers negotiate and exchange resources, despite their decidedly unequal positions within a racial hierarchy. Drawing their example from the West Bank, the authors argue that a Palestinian economic elite has proactively participated in the co-production of the colonial management of spatial mobility, a central component of Israeli colonial rule. The study employs interviews and document analysis to investigate how the nexus between Palestine’s commercial-logistical needs and Israel’s security complex induced large-scale Palestinian producers to exert agency and reorder commercial mobility. The authors describe and explain the evolution of a ‘Door-to-Door’ logistical arrangement, in which large-scale Palestinian traders participate in extending Israeli’s system of spatial control in exchange for facilitating logistical mobility. This horizontal social encounter that entails pay-offs is conditioned, but not fully determined, by vertical relations of domination and subordination.

scholarly journals Evaluation of the atmospheric transport in a GCM using radon measurements: sensitivity to cumulus convection parameterization

2008 ◽  
Vol 8 (10) ◽  
pp. 2811-2832 ◽  
Author(s):  
K. Zhang ◽  
H. Wan ◽  
M. Zhang ◽  
B. Wang
Keyword(s):  
Vertical Distribution ◽  
Radon Concentration ◽  
Large Scale ◽  
Atmospheric Transport ◽  
Surface Concentration ◽  
Transport Processes ◽  
Cumulus Convection ◽  
Models Comparison ◽  
Convection Schemes ◽  
Convection Parameterization

Abstract. The radioactive species radon (222Rn) has long been used as a test tracer for the numerical simulation of large scale transport processes. In this study, radon transport experiments are carried out using an atmospheric GCM with a finite-difference dynamical core, the van Leer type FFSL advection algorithm, and two state-of-the-art cumulus convection parameterization schemes. Measurements of surface concentration and vertical distribution of radon collected from the literature are used as references in model evaluation. The simulated radon concentrations using both convection schemes turn out to be consistent with earlier studies with many other models. Comparison with measurements indicates that at the locations where significant seasonal variations are observed in reality, the model can reproduce both the monthly mean surface radon concentration and the annual cycle quite well. At those sites where the seasonal variation is not large, the model is able to give a correct magnitude of the annual mean. In East Asia, where radon simulations are rarely reported in the literature, detailed analysis shows that our results compare reasonably well with the observations. The most evident changes caused by the use of a different convection scheme are found in the vertical distribution of the tracer. The scheme associated with weaker upward transport gives higher radon concentration up to about 6 km above the surface, and lower values in higher altitudes. In the lower part of the atmosphere results from this scheme does not agree as well with the measurements as the other scheme. Differences from 6 km to the model top are even larger, although we are not yet able to tell which simulation is better due to the lack of observations at such high altitudes.

Chronique d’une écologie décoloniale dans C’est ma terre de Fabrice Bouckat

2020 ◽  
Vol 23 (3) ◽  
pp. 189-205 ◽  
Author(s):  
Françoise Naudillon
Keyword(s):  
West Indies ◽  
Large Scale ◽  
Documentary Film ◽  
Ecological Crisis ◽  
Agent Orange ◽  
Time And Space ◽  
The West ◽  
The One

The documentary film C’est ma terre by Fabrice Bouckat screened during the 2019 edition of Terrafestival is one of the first large-scale films produced locally on the crisis of the chlordecone molecule. This article will examine from a decolonial perspective, how its director, a Martinican with Gabonese origins who lives and works in Guadeloupe, develops a synthetic and universal vision of environmental crises, and thus demonstrates that destruction of ecosystems crosses time and space, cultures and lands, languages and peoples by bringing ecological crisis in the West Indies closer to the one experienced by the Vietnamese victims of Agent Orange.

scholarly journals 14C in the Deep Water of the East Atlantic

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 391-396 ◽  
Author(s):  
Reiner Schlitzer
Keyword(s):  
Deep Water ◽  
Large Scale ◽  
Bottom Water ◽  
Source Parameters ◽  
Potential Temperature ◽  
Source Terms ◽  
East Atlantic ◽  
The West ◽  
Model Calculations ◽  
Inflowing Water

The renewal of east Atlantic deep water and its large-scale circulation and mixing have been studied in observed distributions of temperature, silicate, ΣCO2, and 14C. 14C variations in northeast Atlantic deep water below 3500m depth are small. Δ14C values range from − 100‰ to −125‰. 14C bottom water concentrations decrease from Δ14C =−117‰ in the Sierra Leone Basin to Δ14C = − 123‰ in the Iberian Basin and are consistent with a mean northward bottom water flow. The characteristic of the water that flows from the west Atlantic through the Romanche Trench into the east Atlantic was determined by inspection of θ/Δ14C and θ/SiO2 diagrams. A mean potential temperature of θ = 1.50 ± .05°C was found for the inflowing water. A multi-box model including circulation, mixing, and chemical source terms in the deep water has been formulated. Linear programing and least-squares techniques have been used to obtain the transport and source parameters of the model from the observed tracer fields. Model calculations reveal an inflow through the Romanche Trench from the west Atlantic, which predominates over any other inflow, of (5 ± 2) Sv (potential temperature 1.50°C), a convective turnover of (150 ± 50) years and a vertical apparent diffusivity of (4 ± 1) cm2/s. Chemical source terms are in the expected ranges.

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