scholarly journals The A-LIFE field experiment in the Eastern Mediterranean - Overview and selected highlights 

2021 ◽  
Author(s):  
Bernadett Weinzierl ◽  
Keyword(s):  
Field Experiment ◽  
Field Experiments ◽  
Dispersion Model ◽  
Eastern Mediterranean ◽  
Particle Dispersion ◽  
Saharan Dust ◽  
Aerosol Layer ◽  
Particle Removal ◽  
Data Set ◽  
Coarse Mode

<p>In April 2017, the A-LIFE aircraft field experiment (Absorbing aerosol layers in a changing climate: aging, lifetime and dynamics; (www.a-life.at) was carried out in the Eastern Mediterranean. The overall goal of the ERC-funded A-LIFE project is to investigate the properties of mixtures of absorbing aerosols (in particular mineral dust and black carbon) during their atmospheric lifetime to gather a new data set of key parameters of absorbing aerosol mixtures, to investigate their microphysical and optical properties, and to study potential links between the presence of absorbing particles, aerosol layer lifetime and particle removal.</p><p>In 22 research flights (~80 flight hours), several outbreaks of Saharan and Arabian dust, as well as pollution, biomass burning, and dust-impacted clouds were studied, and a unique aerosol and cloud data set was collected. During a number of flights, coordinated observations including overflights of the ground-based sites in Cyprus (Limassol, Paphos, Agia Marina), Crete (Finokalia), and over Austria (Vienna, Sonnblick Observatory) were performed. The A-LIFE campaign was carried out in close coordination with the 18-month field observations conducted in the framework of CyCARE (October 2016 – March 2018) organized by the Leibniz Institute for Tropospheric Research, and with the PreTECT initiative of the National Observatory of Athens.</p><p>To perform source apportionment, the Lagrangian transport and dispersion model FLEXPART (FLEXible PARTicle dispersion model) version 8.2 was used. Based on FLEXPART model results and aerosol measurements, the observations were classified into 12 aerosol types including background aerosol, clean and polluted mixtures without coarse mode aerosol as well as three sub-classes (clean, moderately-polluted and polluted) for Saharan dust, Arabian dust and mixtures with coarse mode. For each of the 12 aerosol classes, microphysical and optical aerosol properties were derived. One surprising finding of A-LIFE is that scattering properties of polluted dust aerosol do not show the typical dust signature, but rather show a wavelength-dependency of the scattering coefficient.</p><p>We will give an overview of the A-LIFE field experiment and available data sets, compare the properties of the different aerosol mixtures, and discuss the question which aerosol component (natural vs. anthropogenic) dominates the properties in mixed aerosols. We will also compare the A-LIFE dust observations with results from other field experiments (SAMUM, SALTRACE, ATom).</p><p> </p><p>Acknowledgements: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 640458 (A-LIFE). Two EUFAR projects clustered with A-LIFE provided funding for 16 additional flight hours. We would also like to thank the University of Vienna, LMU and DLR for a significant amount of funding for instrumentation, aircraft certification costs, extra flight hours and aircraft allocation days.</p>

scholarly journals Atmospheric rivers moisture sources from a Lagrangian perspective

2016 ◽  
Vol 7 (2) ◽  
pp. 371-384 ◽  
Author(s):  
Alexandre M. Ramos ◽  
Raquel Nieto ◽  
Ricardo Tomé ◽  
Luis Gimeno ◽  
Ricardo M. Trigo ◽  
...  
Keyword(s):  
North Atlantic ◽  
Dispersion Model ◽  
Local Maximum ◽  
Detection Algorithm ◽  
Ocean Basin ◽  
Particle Dispersion ◽  
Western Coast ◽  
Moisture Uptake ◽  
Lagrangian Analysis ◽  
Data Set

Abstract. An automated atmospheric river (AR) detection algorithm is used for the North Atlantic Ocean basin, allowing the identification of the major ARs affecting western European coasts between 1979 and 2012 over the winter half-year (October to March). The entire western coast of Europe was divided into five domains, namely the Iberian Peninsula (9.75° W, 36–43.75° N), France (4.5° W, 43.75–50° N), UK (4.5° W, 50–59° N), southern Scandinavia and the Netherlands (5.25° E, 50–59° N), and northern Scandinavia (5.25° E, 59–70° N). Following the identification of the main ARs that made landfall in western Europe, a Lagrangian analysis was then applied in order to identify the main areas where the moisture uptake was anomalous and contributed to the ARs reaching each domain. The Lagrangian data set used was obtained from the FLEXPART (FLEXible PARTicle dispersion) model global simulation from 1979 to 2012 and was forced by ERA-Interim reanalysis on a 1° latitude–longitude grid. The results show that, in general, for all regions considered, the major climatological areas for the anomalous moisture uptake extend along the subtropical North Atlantic, from the Florida Peninsula (northward of 20° N) to each sink region, with the nearest coast to each sink region always appearing as a local maximum. In addition, during AR events the Atlantic subtropical source is reinforced and displaced, with a slight northward movement of the sources found when the sink region is positioned at higher latitudes. In conclusion, the results confirm not only the anomalous advection of moisture linked to ARs from subtropical ocean areas but also the existence of a tropical source, together with midlatitude anomaly sources at some locations closer to AR landfalls.

scholarly journals Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set

2015 ◽  
Vol 15 (16) ◽  
pp. 9413-9433 ◽  
Author(s):  
S. Eckhardt ◽  
B. Quennehen ◽  
D. J. L. Olivié ◽  
T. K. Berntsen ◽  
R. Cherian ◽  
...  
Keyword(s):  
Black Carbon ◽  
Atmospheric Chemistry ◽  
Emission Inventory ◽  
Dispersion Model ◽  
Measurement Data ◽  
Particle Dispersion ◽  
The Arctic ◽  
Late Winter ◽  
Data Set ◽  
Arctic Haze

Abstract. The concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of 2 years (2008–2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC or rBC and sulfate concentrations quite well, compared to previous comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January–March underestimated by 59 and 37 % for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44 % for July–September), but with overestimates as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is 3 times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modeling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution.

Validation of a Lagrangian particle dispersion model with wind tunnel and field experiments in urban environment

2018 ◽  
Vol 193 ◽  
pp. 273-289 ◽  
Author(s):  
S. Trini Castelli ◽  
P. Armand ◽  
G. Tinarelli ◽  
C. Duchenne ◽  
M. Nibart
Keyword(s):  
Wind Tunnel ◽  
Urban Environment ◽  
Field Experiments ◽  
Dispersion Model ◽  
Particle Dispersion ◽  
Lagrangian Particle

scholarly journals Comparisons of Transport and Dispersion Model Predictions of the Joint Urban 2003 Field Experiment

2008 ◽  
Vol 47 (7) ◽  
pp. 1910-1928 ◽  
Author(s):  
Steve Warner ◽  
Nathan Platt ◽  
Jeffry T. Urban ◽  
James F. Heagy
Keyword(s):  
Field Experiment ◽  
Urban Environment ◽  
Field Experiments ◽  
Dispersion Model ◽  
Urban Environments ◽  
Urban Transport ◽  
Release Time ◽  
Tracer Gas ◽  
Urban Dispersion ◽  
Computationally Intensive

Abstract For a hazardous material release in a city or densely populated area, effective mitigation requires an understanding of the transport and dispersion of these hazards in the complex urban environment. Improved characterization and understanding of urban transport and dispersion will allow for more robust modeling. The Defense Threat Reduction Agency has developed a Hazard Prediction Assessment Capability (HPAC) that includes features to address hazardous releases within an urban environment. During the summer of 2003, a series of tracer gas releases were carried out in Oklahoma City, Oklahoma, and extensive meteorological and tracer concentration measurements were collected in a field experiment known as Joint Urban 2003 (JU03). This analysis uses the observations of JU03 to evaluate “Urban HPAC.” Twenty sets of simulations, or “predictions,” using four Urban HPAC modes and five meteorological input options, were created and compared using a variety of metrics. Strong consistency was found between the conclusions of this study and those of two previously reported Urban HPAC evaluations. For example, improved predictions were associated with the inclusion of a simple empirically based urban dispersion model within HPAC, whereas improvements associated with the inclusion of a more computationally intensive urban wind module were not found. In this study, two new results are reported. First, there was a substantial difference in the performance of Urban HPAC as a function of release time—day or night—that was not discovered earlier because the previously examined urban field experiments focused on nighttime releases only. Daytime releases tended to be underpredicted and nighttime releases tended to be overpredicted. Second, and with respect to the under- and overpredictions described above, the inclusion of the new “Micro” Stationary Wind Fit and Turbulence (SWIFT) “SPRAY” (MSS) Urban HPAC mode typically led to less underprediction during the day and less overprediction at night than the other Urban HPAC modes. In addition, predictions that included MSS typically resulted in the least scatter between observations and predictions. These improvements warrant further investigation to determine whether this conclusion can be extended to other urban environments.

scholarly journals North Atlantic Ocean–Atmosphere Driven Variations in Aerosol Evolution along Lagrangian Cold-Air Outbreak Trajectories

2021 ◽  
Author(s):  
Kevin J. Sanchez ◽  
Bo Zhang ◽  
Hongyu Liu ◽  
Matthew D. Brown ◽  
Ewan C. Crosbie ◽  
...  
Keyword(s):  
North Atlantic ◽  
Dispersion Model ◽  
Temporal Variations ◽  
Particle Dispersion ◽  
Rate Of Change ◽  
Data Set ◽  
Cold Air ◽  
Accumulation Mode ◽  
Cloud Properties ◽  
Cold Air Outbreak

Abstract. Atmospheric marine particle concentrations impact cloud properties, which strongly impact the amount of solar radiation reflected back into space or absorbed by the ocean surface. While satellites can provide a snapshot of current conditions at the overpass time, models are necessary to simulate temporal variations in both particle and cloud properties. However, poor model accuracy limits the reliability with which these tools can be used to predict future climate. Here, we leverage the comprehensive ocean ecosystem and atmospheric aerosol-cloud data set obtained during the third deployment of the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES3). Airborne and ship-based measurements were collected in and around a cold-air outbreak during a three-day intensive operations period from September 17–19, 2017. Cold-air outbreaks are of keen interest for model validation because they are challenging to accurately simulate, which is due, in part, to the numerous feedbacks and sub-grid scale processes that influence aerosol and cloud evolution. The NAAMES observations are particularly valuable because the flight plans were tailored to lie along Lagrangian trajectories, making it possible to spatiotemporally connect upwind and downwind measurements with the state-of-the-art FLEXible PARTicle (FLEXPART) Lagrangian particle dispersion model and then calculate a rate of change in particle properties. Initial aerosol conditions spanning an east-west, closed-cell cloudy to clear air transition region of the cold-air outbreak indicate similar particle concentrations and properties. However, despite the similarities in the aerosol fields, the cloud properties downwind of each region evolved quite differently. One trajectory carried particles through a cold-air outbreak, resulting in a decrease in accumulation mode particle concentration (−42 %) and cloud droplet concentrations, while the other remained outside of the cold-air outbreak and experienced an increase in accumulation mode particle concentrations (+62 %). The variable meteorological conditions between these two adjacent trajectories result from differences in the local sea surface temperature altering stability of the marine atmospheric boundary layer because of the location of the Labrador Current. Further comparisons of historical satellite observations indicate that the observed pattern occurs annually in the region, making it an ideal location for future airborne Lagrangian studies tracking the evolution of aerosols and clouds over time under cold air outbreak conditions.

scholarly journals Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set

2015 ◽  
Vol 15 (7) ◽  
pp. 10425-10477 ◽  
Author(s):  
S. Eckhardt ◽  
B. Quennehen ◽  
D. J. L. Olivié ◽  
T. K. Berntsen ◽  
R. Cherian ◽  
...  
Keyword(s):  
Black Carbon ◽  
Atmospheric Chemistry ◽  
Emission Inventory ◽  
Dispersion Model ◽  
Measurement Data ◽  
Particle Dispersion ◽  
The Arctic ◽  
Late Winter ◽  
Data Set ◽  
Arctic Haze

Abstract. The concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of two years (2008–2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry-transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry-climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC/rBC and sulfate concentrations quite well, compared to past comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January-March underestimated by 59 and 37% for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44% for July–September), but with over- as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is three times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modelling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution.

Integrating the Urban Canopy Layer in a Lagrangian Particle Dispersion Model

2021 ◽  
Author(s):  
Stefan Stöckl ◽  
Mathias W. Rotach ◽  
Natascha Kljun
Keyword(s):  
Field Experiments ◽  
Dispersion Model ◽  
Model Performance ◽  
Urban Canopy ◽  
Sensitivity Study ◽  
Particle Dispersion ◽  
Lagrangian Particle ◽  
Canopy Layer ◽  
Wind Speed Profile ◽  
Urban Canopy Layer

<p>Traditional Lagrangian particle dispersion models reflect particles at the zero-plane displacement height and therefore cannot properly take near-ground effects into account. In this study, we investigate whether including the urban canopy layer improves the performance of such a Lagrangian particle dispersion model. Here, spatially averaged flow and turbulence profiles throughout the urban canopy are constructed based on data from the literature (mostly from wind tunnel and numerical modeling studies).</p><p>We apply a first-order approach to test to what degree the explicit inclusion of the urban canopy changes the simulated concentration distributions. In a comprehensive sensitivity study, we show that most of the parameters introduced to describe the turbulence and flow profiles in the canopy have a relatively minor impact on the dispersion (and hence concentration distribution) – despite their inherent uncertainty. In particular, concentration fields are more sensitive to previously existing parameters of the model. One exception is a parameter describing the mean canopy wind speed profile, to which the model is sensitive.</p><p>When compared to data from the BUBBLE tracer experiment, the results show that the inclusion of the urban canopy layer slightly improves the modelled concentration values. The improvement is minor and might likely differ when comparing with other field experiments. However, the key point here is that the increased complexity and added capability of near-ground concentration simulation did not fundamentally change the model performance.</p><p>Ultimately, inclusion of the urban canopy layer will allow the model to be used as the dispersion core for an urban footprint model with footprint estimates near the ground.</p>

scholarly journals Temporally delineated sources of major chemical species in high Arctic snow

2018 ◽  
Vol 18 (5) ◽  
pp. 3485-3503 ◽  
Author(s):  
Katrina M. Macdonald ◽  
Sangeeta Sharma ◽  
Desiree Toom ◽  
Alina Chivulescu ◽  
Andrew Platt ◽  
...  
Keyword(s):  
Black Carbon ◽  
Carboxylic Acids ◽  
Major Ions ◽  
Dispersion Model ◽  
High Arctic ◽  
Particle Dispersion ◽  
Photochemical Reactions ◽  
Sea Salt ◽  
The Arctic ◽  
Data Set

Abstract. Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian High Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analyzed for black carbon, major ions, and metals, and this rich data set provided an opportunity for a temporally refined source apportionment of snow composition via positive matrix factorization (PMF) in conjunction with FLEXPART (FLEXible PARTicle dispersion model) potential emission sensitivity analysis. Seven source factors were identified: sea salt, crustal metals, black carbon, carboxylic acids, nitrate, non-crustal metals, and sulfate. The sea salt and crustal factors showed good agreement with expected composition and primarily northern sources. High loadings of V and Se onto Factor 2, crustal metals, was consistent with expected elemental ratios, implying these metals were not primarily anthropogenic in origin. Factor 3, black carbon, was an acidic factor dominated by black carbon but with some sulfate contribution over the winter-haze season. The lack of K+ associated with this factor, a Eurasian source, and limited known forest fire events coincident with this factor's peak suggested a predominantly anthropogenic combustion source. Factor 4, carboxylic acids, was dominated by formate and acetate with a moderate correlation to available sunlight and an oceanic and North American source. A robust identification of this factor was not possible; however, atmospheric photochemical reactions, ocean microlayer reaction, and biomass burning were explored as potential contributors. Factor 5, nitrate, was an acidic factor dominated by NO3−, with a likely Eurasian source and mid-winter peak. The isolation of NO3− on a separate factor may reflect its complex atmospheric processing, though the associated source region suggests possibly anthropogenic precursors. Factor 6, non-crustal metals, showed heightened loadings of Sb, Pb, and As, and correlation with other metals traditionally associated with industrial activities. Similar to Factor 3 and 5, this factor appeared to be largely Eurasian in origin. Factor 7, sulfate, was dominated by SO42− and MS with a fall peak and high acidity. Coincident volcanic activity and northern source regions may suggest a processed SO2 source of this factor.

scholarly journals A Non-Uniform Broadcast Fertilization Method and Its Performance Analysis under Basin Irrigation

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 292
Author(s):  
Kai Zhang ◽  
Meijian Bai ◽  
Yinong Li ◽  
Shaohui Zhang ◽  
Di Xu
Keyword(s):  
Field Experiment ◽  
Field Experiments ◽  
Transport Model ◽  
Inflow Rate ◽  
Application Performance ◽  
Solute Content ◽  
Basin Surface ◽  
Movement Characteristics ◽  
The Difference ◽  
Basin Irrigation

The broadcast fertilization method is widely used under basin irrigation in China. A reasonable broadcast fertilization method can effectively improve application performance of fertilization and reduce pollution from non-point agricultural sources. In this study, firstly, a non-uniform broadcast fertilization method and a non-uniform application coefficient were proposed. The value of non-uniform application coefficient is defined in this paper. It represents the ratio of the difference between the maximum and the average fertilization amount of fertilizer applied on the basin surface to the average fertilization amount of fertilizer applied on the basin surface. Secondly, field experiments were conducted to study the movement characteristics of fertilizer under non-uniform broadcast fertilization for basin irrigation. Field experiment results showed that under the condition of basin irrigation, the non-uniform broadcast fertilization method could weaken the non-uniform distribution of fertilizer due to erosion and transport capacity of solid fertilizer by irrigation water flow, which could significantly improve the uniformity of soil solute content. Thirdly, the solute transport model for broadcast fertilization was corroborated by the field experiment results. The variation rule of fertilization performance with non-uniform application coefficient under different basin length and inflow rate was achieved by simulation. The simulation results showed that fertilization uniformity and fertilization storage efficiency increased first and then decreased with the increase of non-uniform application coefficient. In order to be practically applicable, suitable irrigation programs of non-uniform application coefficient under different basin length and inflow rate conditions were proposed by numerical simulation.

High phosphorus concentrations in seed of wheat and annual medic are related to higher rates of dry matter production of seedlings and plants

1988 ◽  
Vol 28 (6) ◽  
pp. 765 ◽  
Author(s):  
MDA Bolland ◽  
MJ Baker
Keyword(s):  
Triticum Aestivum ◽  
Field Experiment ◽  
Western Australia ◽  
Dry Matter ◽  
Field Experiments ◽  
Medicago Polymorpha ◽  
P Concentration ◽  
Pot Experiments ◽  
Matter Production ◽  
Burr Medic

Seed of 2 cultivars of wheat (Triticum aestivum) and 1 burr medic (Medicago polymorpha) with increasing phosphorus (P) concentrations (wheat 1.4-3.7 g P/kg dry matter, medic 3.3-7.9 g P/kg dry matter) were collected from field experiments with variable levels of applied superphosphate (wheat 0- 577 kg P/ha, medic 0-364 kg P/ha) in south-western Australia. These seeds were used in further experiments to examine the effect of seed P concentration on the subsequent dry matter (DM) production of seedlings and plants in 3 glasshouse pot experiments and 1 field experiment. Seed of the same size (wheat, 35 mg/seed; medic, 3.6 mg/seed) but with increasing P concentration produced substantially higher DM yields in the absence or presence of freshly applied superphosphate P up to 28-35 days after sowing in the pot experiments and 67 days after sowing in the field experiment.

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