scholarly journals The Relative Importance of Scavenging, Oxidation, and Ice-Phase Processes in the Production and Wet Deposition of Sulfate

2005 ◽  
Vol 62 (7) ◽  
pp. 2118-2135 ◽  
Author(s):  
Vlado Spiridonov ◽  
Mladjen Curic
Keyword(s):  
Wet Deposition ◽  
Lower Percentage ◽  
Relative Importance ◽  
Total Sulfur ◽  
Sulfate Production ◽  
Relative Contribution ◽  
Cloud Resolving Model ◽  
Cloud Scavenging ◽  
Nucleation Scavenging ◽  
Ice Phase

Abstract The relative importance of various processes to sulfate production and wet deposition is examined by using a cloud-resolving model coupled with a sulfate chemistry submodel. Results using different versions of the model are then compared and principal differences with respect to their dynamics, microphysics, and chemistry are carefully discussed. The results imply that the dominant microphysical and chemical conversions of sulfate in the 3D run are nucleation, scavenging, and oxidation. Due to the lower cloud water and rainwater pH, oxidation does not contribute as significantly to the sulfate mass in the 2D run as the 3D. Sensitivity tests have revealed that in-cloud scavenging in the 2D run for continental nonpolluted and continental polluted clouds accounted for 29.4% and 31.5% of the total sulfur deposited, respectively. The 3D run shows a lower percentage contribution to sulfur deposition for about 28.2% and 29.6%. In addition, subcloud scavenging for the 2D run contributed about 32.7% and 38.2%. In-cloud oxidation in the 2D run accounted for about 24.5% to 30.4% of the total sulfur mass deposited. Subcloud oxidation contributed from 21.0% to 20.6% of the total sulfur mass removed by wet deposition. In-cloud oxidation for the 3D run shows slightly lower percentage values when compared to those from the 2D run. The relative contribution of subcloud oxidation for continental nonpolluted and polluted clouds exceeds those values in the 2D run by approximately 7% and 10%, respectively. Ignoring the ice phase and considering those types of convective clouds in the 2D run may lead to a higher value of the total sulfur mass removed by the wet deposition of about 33.9% to 39.2% for the continental nonpolluted and 36.2% to 45.6% for the continental polluted distributions relative to the base runs.

scholarly journals Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

2009 ◽  
Vol 9 (5) ◽  
pp. 22041-22101 ◽  
Author(s):  
B. Croft ◽  
U. Lohmann ◽  
R. V. Martin ◽  
P. Stier ◽  
S. Wurzler ◽  
...  
Keyword(s):  
Wet Deposition ◽  
Cloud Droplet ◽  
Ice Crystal ◽  
Cloud Processing ◽  
Aerosol Cloud ◽  
Aerosol Mass ◽  
Cloud Scavenging ◽  
Nucleation Scavenging ◽  
Scavenging Ratios ◽  
Global Mean

Abstract. A diagnostic nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. Sensitivity studies are presented, which compare aerosol concentrations, and deposition between a variety of in-cloud scavenging approaches, including prescribed fractions, several diagnostic schemes, and a prognostic aerosol cloud processing treatment that passes aerosol in-droplet and in-ice crystal concentrations between model time steps. For one sensitivity study, assuming 100% of the in-cloud aerosol is scavenged into the cloud droplets and ice crystals, the annual global mean accumulation mode number burden is decreased by 65%, relative to a simulation with prognostic aerosol cloud processing. Diagnosing separate nucleation scavenging ratios for aerosol number and mass distributions, as opposed to equating the aerosol mass scavenging to the number scavenging ratios, reduces the annual global mean sulfate burden by near to 10%. The annual global mean sea salt burden is 30% lower for the diagnostic approach, which does not carry aerosol in-droplet and in-crystal concentrations between model time-steps as compared to the prognostic scheme. Implementation of in-cloud impaction scavenging reduced the annual, global mean black carbon burden by 30% for the prognostic aerosol cloud processing scheme. Better agreement with observations of black carbon profiles from aircraft (changes near to one order of magnitude for mixed phase clouds), 210Pb surface layer concentrations and wet deposition, and the geographic distribution of aerosol optical depth are found for the new diagnostic scavenging as compared to prescribed ratio scavenging scheme of the standard ECHAM5-HAM.

scholarly journals Influences of in-cloud aerosol scavenging parameterizations on aerosol concentrations and wet deposition in ECHAM5-HAM

2010 ◽  
Vol 10 (4) ◽  
pp. 1511-1543 ◽  
Author(s):  
B. Croft ◽  
U. Lohmann ◽  
R. V. Martin ◽  
P. Stier ◽  
S. Wurzler ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Droplet ◽  
Ice Crystal ◽  
Aerosol Mass ◽  
Order Of Magnitude ◽  
Cloud Scavenging ◽  
Nucleation Scavenging ◽  
Ice Phase

Abstract. A diagnostic cloud nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This scheme is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. The aerosol mass scavenged in stratiform clouds is found to be primarily (>90%) scavenged by cloud nucleation processes for all aerosol species, except for dust (50%). The aerosol number scavenged is primarily (>90%) attributed to impaction. 99% of this impaction scavenging occurs in clouds with temperatures less than 273 K. Sensitivity studies are presented, which compare aerosol concentrations, burdens, and deposition for a variety of in-cloud scavenging approaches: prescribed fractions, a more computationally expensive prognostic aerosol cloud processing treatment, and the new diagnostic scheme, also with modified assumptions about in-cloud impaction and nucleation scavenging. Our results show that while uncertainties in the representation of in-cloud scavenging processes can lead to differences in the range of 20–30% for the predicted annual, global mean aerosol mass burdens, and near to 50% for accumulation mode aerosol number burden, the differences in predicted aerosol mass concentrations can be up to one order of magnitude, particularly for regions of the middle troposphere with temperatures below 273 K where mixed and ice phase clouds exist. Different parameterizations for impaction scavenging changed the predicted global, annual mean number removal attributed to ice clouds by seven-fold, and the global, annual dust mass removal attributed to impaction by two orders of magnitude. Closer agreement with observations of black carbon profiles from aircraft (increases near to one order of magnitude for mixed phase clouds), mid-troposphere 210Pb vertical profiles, and the geographic distribution of aerosol optical depth is found for the new diagnostic scavenging scheme compared to the prescribed scavenging fraction scheme of the standard ECHAM5-HAM. The diagnostic and prognostic schemes represent the variability of scavenged fractions particularly for submicron size aerosols, and for mixed and ice phase clouds, and are recommended in preference to the prescribed scavenging fractions method.

Demography of Xenosaurus platyceps (Squamata: Xenosauridae): a comparison between tropical and temperate populations

2008 ◽  
Vol 29 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Carissa Jones ◽  
Isaac Rojas-González ◽  
Julio Lemos-Espinal ◽  
Jaime Zúñiga-Vega
Keyword(s):  
Life History ◽  
Population Growth ◽  
Adult Mortality ◽  
Life History Strategies ◽  
Relative Importance ◽  
Theoretical Frameworks ◽  
Population Growth Rates ◽  
Relative Contribution ◽  
Two Populations ◽  
Average Fitness

Abstract There appears to be variation in life-history strategies even between populations of the same species. For ectothermic organisms such as lizards, it has been predicted that demographic and life-history traits should differ consistently between temperate and tropical populations. This study compares the demographic strategies of a temperate and a tropical population of the lizard Xenosaurus platyceps. Population growth rates in both types of environments indicated populations in numerical equilibrium. Of the two populations, we found that the temperate population experiences lower adult mortality. The relative importance (estimated as the relative contribution to population growth rate) of permanence and of the adult/reproductive size classes is higher in the temperate population. In contrast, the relative importance for average fitness of fecundity and growth is higher in the tropical population. These results are consistent with the theoretical frameworks about life-historical differences among tropical and temperate lizard populations.

scholarly journals Plant assemblages in atmospheric deposition

2019 ◽  
Author(s):  
Ke Dong ◽  
Cheolwoon Woo ◽  
Naomichi Yamamoto
Keyword(s):  
Atmospheric Deposition ◽  
Dry Deposition ◽  
Wet Deposition ◽  
High Throughput Sequencing ◽  
Sampling Site ◽  
Its2 Region ◽  
Dry And Wet Deposition ◽  
Custom Made ◽  
Plant Assemblages ◽  
Cloud Scavenging

Abstract. Plants disperse spores, pollen, and fragments into the atmosphere. The emitted plant particles return to the pedosphere by sedimentation (dry deposition) and/or by precipitation (wet deposition) and constitute part of the global cycle of substances. However, little is known regarding the taxonomic diversities and flux densities of plant particles deposited from the atmosphere. Here, plant assemblages were examined in atmospheric deposits collected in Seoul in South Korea. A custom-made automatic sampler was used to collect dry and wet deposition samples for which plant assemblages and quantities were determined using high-throughput sequencing and quantitative PCR with universal plant-specific primers targeting the internal transcribed spacer 2 (ITS2) region. Dry deposition was dominant for atmospheric deposition of plant particles (87 %). The remaining 13 % was deposited by precipitation, i.e., wet deposition, via rainout (in-cloud scavenging) and/or washout (below-cloud scavenging). Plant assemblage structures did not differ significantly between dry and wet deposition, indicating that washout, which is likely taxon-independent, predominated rainout, which is likely taxon-dependent, for wet deposition of atmospheric plant particles. A small number of plant genera were detected only in wet deposition, indicating that they might be specifically involved in precipitation through acting as nucleation sites in the atmosphere. Future interannual monitoring will control for the seasonality of atmospheric plant assemblages observed at our sampling site. Future global monitoring is also proposed to investigate geographical differences and investigate whether endemic species are involved in plant-mediated bioprecipitation in regional ecological systems.

A Dynamic Structural Model of Education and Skills Requirements for Careers in Information Systems

2011 ◽  
pp. 1-26 ◽  
Author(s):  
Glenn R. Lowry ◽  
Rodney L. Turner ◽  
Julie Fisher
Keyword(s):  
Professional Development ◽  
Information Systems ◽  
Structural Model ◽  
Soft Skills ◽  
Working Environment ◽  
Relative Importance ◽  
Relative Contribution ◽  
Dynamic Structural Model ◽  
Is Professionals ◽  
Career Progress

This chapter presents a dynamic structural model of the relative contribution and importance of education and skills required of information systems (IS) professionals. Model development took into account the technical skills found in many tertiary IS programs, other business-oriented academic studies, and soft skills sought by employers in new graduates. The model also includes features of the working environment which influence the career progress of IS graduates. Acknowledging the importance of these four areas, the authors present a second-order structural model that links these areas and compares the application of this model to IS students and decision makers who employ graduates. The model fits the data for the two groups and exhibits some unexpected outcomes in the area of soft skills, with students attributing more importance to soft skills than IS managers. The model was employed to identify gender differences in perceptions of the relative contribution and importance of education and skills required of IS professionals. The model also includes features of the working environment which influence the career progress of IS graduates. The model was used to describe how attitudes and perceptions of IS professionals change across career stages as measured by age groupings. Changes in perceptions across four major age groupings show significant differences with respect to these factors according to age groups and by inference, career stage. The model allows, with some confidence, a quantitative interpretation of the relative importance of the respective variables from the perspectives of the student and employer stakeholder groups toward the education and professional development of IS professionals. The model also suggests the presence of contrasting, gender-based quantitative views of the relative importance of the respective variables to the education and professional development of IS professionals.

scholarly journals Impacts of aerosol-cloud interactions on past and future changes in tropospheric composition

2009 ◽  
Vol 9 (12) ◽  
pp. 4115-4129 ◽  
Author(s):  
N. Unger ◽  
S. Menon ◽  
D. M. Koch ◽  
D. T. Shindell
Keyword(s):  
Air Quality ◽  
Wet Deposition ◽  
Wide Spectrum ◽  
Surface Ozone ◽  
Tropospheric Chemistry ◽  
Atmospheric Composition ◽  
Sulfate Production ◽  
Aerosol Cloud ◽  
Aerosol Cloud Interactions ◽  
The Impact

Abstract. The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embrace a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be −2.0 Wm−2 for PD-PI and −0.6 Wm−2 for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and ~10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions (~10–30%). Nitric acid wet deposition is dampened by 15–20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1–2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality.

Above-ground biomass estimation for a shrubby mistletoe in an Amazonian savanna

2019 ◽  
Vol 36 (1) ◽  
pp. 6-12 ◽  
Author(s):  
Sarah Rosane M. C. Fadini ◽  
Reinaldo I. Barbosa ◽  
Rafael Rode ◽  
Viviane Corrêa ◽  
Rodrigo F. Fadini
Keyword(s):  
Life Form ◽  
Food Resource ◽  
Keystone Species ◽  
Host Size ◽  
Biomass Estimation ◽  
Relative Importance ◽  
Above Ground Biomass ◽  
Ground Biomass ◽  
Relative Contribution ◽  
Poor Predictor

AbstractMistletoes are considered keystone species on woodlands and savannas worldwide, providing a food resource for a diversified fauna, as well as a nutrient-enriched litter. Infections can be large (∼1–3 m) and, in some parts of the Amazonian savannas, parasitize up to 70% of hosts locally. Despite these facts, biomass of mistletoes is rarely investigated. Here we constructed allometric models to predict the biomass stock of the shrubby mistletoe Psittacanthus plagiophyllus in an Amazonian savanna. In addition, we determined whether host size could be used as a proxy for mistletoe biomass. Finally, we compared the biomass of mistletoes with that of trees, to evaluate their relative importance. We have shown that: (1) biomass of leaves (46.1% ± 13.5%) are as important as of stems (47.8% ± 13.5%), and relative contribution of stems increases as plant grows; (2) the model including width, breadth and vertical depth was the best (SE = 0.39, R2 = 0.9) for predicting individual mistletoe biomass; (3) mistletoe load and biomass per host had a positive, but weak (R2 = 0.11 and 0.09, respectively), relationship with host size, and thus such host information is a poor predictor of mistletoe biomass; and (4) in comparison with trees, mistletoes constituted less than 0.15% (0.5–22 kg ha−1) of the total above-ground biomass, suggesting that this life-form is irrelevant to the local biomass stock despite its unequivocal biological importance.

scholarly journals Nitrate retention and removal in Mediterranean streams bordered by contrasting land uses: a <sup>15</sup>N tracer study

2009 ◽  
Vol 6 (2) ◽  
pp. 181-196 ◽  
Author(s):  
D. von Schiller ◽  
E. Martí ◽  
J. L. Riera
Keyword(s):  
Agricultural Land ◽  
N Cycling ◽  
Urban Stream ◽  
Relative Importance ◽  
Transfer Velocity ◽  
Nitrate Retention ◽  
Relative Contribution ◽  
Uptake Length ◽  
Agricultural Stream ◽  
Forested Stream

Abstract. We used 15N-labelled nitrate (NO3−) additions to investigate pathways of nitrogen (N) cycling at the whole-reach scale in three stream reaches with adjacent forested, urban and agricultural land areas. Our aim was to explore among-stream differences in: (i) the magnitude and relative importance of NO3− retention (i.e. assimilatory uptake) and removal (i.e. denitrification), (ii) the relative contribution of the different primary uptake compartments to NO3− retention, and (iii) the regeneration, transformation and export pathways of the retained N. Streams varied strongly in NO3− concentration, which was highest in the agricultural stream and lowest in the forested stream. The agricultural stream also showed the lowest dissolved oxygen (DO) concentration and discharge. Standing stocks of primary uptake compartments were similar among streams and dominated by detritus compartments (i.e. fine and coarse benthic organic matter). Metabolism was net heterotrophic in all streams, although the degree of heterotrophy was highest in the agricultural stream. The NO3− uptake length was shortest in the agricultural stream, intermediate in the urban stream, and longest in the forested stream. Conversely, the NO3− mass-transfer velocity and the areal NO3− uptake rate were highest in the urban stream. Denitrification was not detectable in the forested stream, but accounted for 9% and 68% of total NO3− uptake in the urban and the agricultural stream, respectively. The relative contribution of detritus compartments to NO3− assimilatory uptake was greatest in the forested and lowest in the agricultural stream. In all streams, the retained N was rapidly regenerated back to the water column. Due to a strong coupling between regeneration and nitrification, most retained N was exported from the experimental reaches in the form of NO3−. This study provides evidence of fast in-stream N cycling, although the relative importance of N retention and removal varied considerably among streams. Results suggest that permanent NO3− removal via denitrification may be enhanced over temporary NO3− retention via assimilatory uptake in heterotrophic human-altered streams characterized by high NO3− and low DO concentrations.

scholarly journals Selection of criteria for multi-criteria decision making of reservoir flood control operation

2017 ◽  
Vol 19 (4) ◽  
pp. 558-571 ◽  
Author(s):  
Feilin Zhu ◽  
Ping-an Zhong ◽  
Yimeng Sun ◽  
Bin Xu
Keyword(s):  
Neural Network ◽  
Bp Neural Network ◽  
Flood Control ◽  
Relative Importance ◽  
Contribution Ratio ◽  
Control Operation ◽  
Relative Contribution ◽  
Flood Control Operation ◽  
Reservoir Flood Control Operation ◽  
Selection Of

In reservoir flood control operation, selection of criteria is an important part of the multi-criteria decision making (MCDM) procedure. This paper proposes a method to select criteria for MCDM of reservoir flood control operation based on the back-propagation (BP) neural network. According to the concept of ideal and anti-ideal points, we propose a method to generate training samples of the BP neural network via stochastic simulation. The topological structure of a three-layer BP neural network used for criteria selection is established. The relative importance of criteria is derived via the learned connection weights of a trained BP neural network, and its calculation method is proposed. The sensitivity curve method is employed to conduct sensitivity analysis, and the relative contribution ratio is defined to quantify the relative sensitivity strength of each criterion. We present the principle and threshold value of criteria selection based on the comprehensive discrimination index defined by the combination of the relative importance and relative contribution ratio. The Pubugou reservoir is selected as the case study. The results show that the proposed method can provide an effective tool for decision makers to select criteria before MCDM modeling of reservoir flood control operation.

scholarly journals Inter-annual variations of wet deposition in Beijing from 2014–2017: implications of below-cloud scavenging of inorganic aerosols

2021 ◽  
Vol 21 (12) ◽  
pp. 9441-9454
Author(s):  
Baozhu Ge ◽  
Danhui Xu ◽  
Oliver Wild ◽  
Xuefeng Yao ◽  
Junhua Wang ◽  
...  
Keyword(s):  
Air Pollution ◽  
Wet Deposition ◽  
Major Ions ◽  
Action Plan ◽  
Sequential Sampling ◽  
Pollution Prevention ◽  
Weighted Average ◽  
Chemical Components ◽  
Wet Scavenging ◽  
Cloud Scavenging

Abstract. Wet scavenging is an efficient pathway for the removal of particulate matter (PM) from the atmosphere. High levels of PM have been a major cause of air pollution in Beijing but have decreased sharply under the Air Pollution Prevention and Control Action Plan launched in 2013. In this study, 4 years of observations of wet deposition have been conducted using a sequential sampling technique to investigate the detailed variation in chemical components through each rainfall event. We find that the major ions, SO42-, Ca2+, NO3-, and NH4+, show significant decreases over the 2013–2017 period (decreasing by 39 %, 35 %, 12 %, and 25 %, respectively), revealing the impacts of the Action Plan. An improved method of estimating the below-cloud scavenging proportion based on sequential sampling is developed and implemented to estimate the contribution of below-cloud and in-cloud wet deposition over the four-year period. Overall, below-cloud scavenging plays a dominant role to the wet deposition of four major ions at the beginning of the Action Plan. The contribution of below-cloud scavenging for Ca2+, SO42-, and NH4+ decreases from above 50 % in 2014 to below 40 % in 2017. This suggests that the Action Plan has mitigated PM pollution in the surface layer and hence decreased scavenging due to the washout process. In contrast, we find little change in the annual volume weighted average concentration for NO3- where the contribution from below-cloud scavenging remains at ∼ 44 % over the 2015–2017 period. While highlighting the importance of different wet scavenging processes, this paper presents a unique new perspective on the effects of the Action Plan and clearly identifies oxidized nitrogen species as a major target for future air pollution controls.

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