scholarly journals A new parameterization of particle dry deposition over rough surfaces

2014 ◽  
Vol 14 (22) ◽  
pp. 12429-12440 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao
Keyword(s):  
Dry Deposition ◽  
Particle Deposition ◽  
Rough Surfaces ◽  
Deposition Velocity ◽  
Deposition Flux ◽  
Data Set ◽  
Roughness Elements ◽  
Drag Partition ◽  
Wind Tunnel Data ◽  
Surface Particle

Abstract. In existing particle dry deposition schemes, the effects of gravity and surface roughness elements on particle motion are often poorly represented. In this study, we propose a new scheme to overcome such deficiencies. Particle deposition velocity is a function of aerodynamic, surface-collection and gravitational resistances. In this study, the effect of gravitation settling is treated analytically. More importantly, the new scheme takes into consideration the impacts of roughness elements on turbulent particle diffusion and surface particle collection. A relationship between aerodynamic and surface-collection processes is established by using an analogy between drag partition and deposition-flux partition. The scheme is then tested against a wind-tunnel data set for four different surfaces and a good agreement between the scheme predictions and the observations is found. The sensitivity of the scheme to the input parameters is tested. Important factors which affect particle deposition in different particle size ranges are identified. The scheme shows good capacity for modeling particle deposition over rough surfaces.

scholarly journals A new parameterization of dust dry deposition over rough surfaces

2014 ◽  
Vol 14 (6) ◽  
pp. 8063-8094 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao
Keyword(s):  
Dry Deposition ◽  
Rough Surfaces ◽  
Deposition Flux ◽  
Dust Deposition ◽  
Dust Collection ◽  
Surface Dust ◽  
Roughness Elements ◽  
Drag Partition ◽  
Dust Diffusion ◽  
Good Agreement

Abstract. The performances of existing dust dry deposition schemes are rather unsatisfactory for rough surfaces. In this study, we propose a new scheme to overcome some of the deficiencies. The scheme takes into consideration of the impacts of roughness elements on turbulent dust diffusion and surface dust collection. A relationship between the aerodynamics and surface collection process is established by using an analogy between deposition-flux partition and drag partition. The scheme is then tested against a wind-tunnel dataset for four different surfaces and a good agreement between the scheme predictions and the observations is found. The sensitivity of the scheme to the input parameters is tested. Important factors which affect dust deposition in different particle size ranges are identified. The scheme shows good capacity for modeling dust deposition over rough surfaces.

scholarly journals Effects of aerosol dynamics and gas–particle conversion on dry deposition of inorganic reactive nitrogen in a temperate forest

2020 ◽  
Vol 20 (8) ◽  
pp. 4933-4949 ◽  
Author(s):  
Genki Katata ◽  
Kazuhide Matsuda ◽  
Atsuyuki Sorimachi ◽  
Mizuo Kajino ◽  
Kentaro Takagi
Keyword(s):  
Dry Deposition ◽  
Particle Deposition ◽  
Chemical Transport ◽  
Reactive Nitrogen ◽  
Surface Model ◽  
Deposition Flux ◽  
Transport Models ◽  
Inorganic Particles ◽  
Aerosol Dynamics ◽  
Chemical Transport Models

Abstract. Dry deposition has an impact on nitrogen status in forest environments. However, the mechanism for the high dry-deposition rates of fine nitrate particles (NO3-) observed in forests remains unknown and is thus a potential source of error in chemical transport models (CTMs). Here, we modified and applied a multilayer land surface model coupled with dry-deposition and aerosol dynamic processes for a temperate mixed forest in Japan. This represents the first application of such a model to ammonium nitrate (NH4NO3) gas–particle conversion (gpc) and the aerosol water uptake of reactive nitrogen compounds. Thermodynamics, kinetics, and dry deposition for mixed inorganic particles are modeled by a triple-moment modal method. Data for inorganic mass and size-resolved total number concentrations measured by a filter pack and electrical low-pressure impactor in autumn were used for model inputs and subsequent numerical analysis. The model successfully reproduces turbulent fluxes observed above the canopy and vertical micrometeorological profiles noted in our previous studies. The sensitivity tests with and without gpc demonstrated clear changes in the inorganic mass and size-resolved total number concentrations within the canopy. The results also revealed that within-canopy evaporation of NH4NO3 under dry conditions significantly enhances the deposition flux of fine-NO3- and fine-NH4+ particles, while reducing the deposition flux of nitric acid gas (HNO3). As a result of the evaporation of particulate NH4NO3, the calculated daytime mass flux of fine NO3- over the canopy was 15 times higher in the scenario of “gpc” than in the scenario of “no gpc”. This increase caused high contributions from particle deposition flux (NO3- and NH4+) to total nitrogen flux over the forest ecosystem (∼39 %), although the contribution of NH3 was still considerable. A dry-deposition scheme coupled with aerosol dynamics may be required to improve the predictive accuracy of chemical transport models for the surface concentration of inorganic reactive nitrogen.

Measured Effects of Reduced Flow Velocity in a Laminar Flow Cleanroom

1994 ◽  
Vol 37 (3) ◽  
pp. 41-46
Author(s):  
Peter Carr ◽  
Angelo Rapa ◽  
William Fosnight ◽  
Robert Baseman ◽  
Douglas Cooper
Keyword(s):  
Laminar Flow ◽  
Particle Deposition ◽  
Deposition Velocity ◽  
Equivalent Diameter ◽  
Surface Deposition ◽  
Deposition Velocities ◽  
Airborne Concentration ◽  
Class 1 ◽  
Surface Particle ◽  
Contamination Levels

Vertical laminar flow (VLF) cleanrooms generally operate with airflows between 60 feet per minute (fpm) and 110 fpm. Tests were performed to evaluate the effects on particle contamination levels when the airflow velocity in a FED-STD-209 Class 1 VLF cleanroom was reduced. The cleanroom normally operates at 90 fpm. Measurements of surface particle concentrations were made on settling monitor wafers and on wafers carried in an open cassette. Optical particle counters measured the airborne particle concentrations at several locations. Results at 100 fpm and 50 fpm, respectively, for particles larger than or equal to 0.3 μm in optical equivalent diameter were −0.0002 and +0.0029 particles/sq cm/hr for the settling wafers and 0.009 and 0.024/sq cm total for the wafers carried for 5 hr in the open cassettes. Summary statistics are provided for the airborne and surface particle counts. Deposition velocity is the ratio of surface deposition rate to airborne concentration. For the monitor wafers at the lower flow, the calculated particle deposition velocities were near 0.003 cm/sec, which is within the range expected from theory and experiments in the literature.

scholarly journals How are NH<sub>3</sub> dry deposition estimates affected by combining the LOTOS-EUROS model with IASI-NH<sub>3</sub> satellite observations?

2018 ◽  
Author(s):  
Shelley C. van der Graaf ◽  
Enrico Dammers ◽  
Martijn Schaap ◽  
Jan Willem Erisman
Keyword(s):  
Dry Deposition ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Deposition Velocity ◽  
Deposition Flux ◽  
Deposition Fluxes ◽  
Po Valley ◽  
Atmospheric Remote Sensing ◽  
Spatial Coverage ◽  
Recent Developments

Abstract. Atmospheric levels of reactive nitrogen have substantially increased during the last century resulting in increased nitrogen deposition to ecosystems, causing harmful effects such as soil acidification, reduction in plant biodiversity and eutrophication in lakes and the ocean. Recent developments in the use of atmospheric remote sensing enabled us to resolve concentration fields of NH3 with larger spatial coverage and these observations may be used to improve the quantification of NH3 deposition. In this paper we use a relatively simple, data-driven method to derive dry deposition fluxes and surface concentrations of NH3 for Europe and for the Netherlands. The aim of this paper is to determine for the applicability and the limitations of this method for NH3 using space-born observations of the Infrared Atmospheric Sounding Interferometer (IASI) and the LOTOS-EUROS atmospheric transport model. The original modelled dry NH3 deposition flux from LOTOS-EUROS and the flux inferred from IASI are compared to indicate areas with large discrepancies between the two and where potential model improvements are needed. The largest differences in derived dry deposition fluxes occur in large parts of Central Europe, where the satellite-observed NH3 concentrations are higher than the modelled ones, and in Switzerland, northern Italy (Po Valley) and southern Turkey, where the modelled NH3 concentrations are higher than the satellite-observed ones. A sensitivity analysis of 8 model input parameters important for NH3 dry deposition modelling showed that the IASI-derived dry NH3 deposition fluxes may vary from ~ 20 % up to ~ 50 % throughout Europe. Variations in the dry deposition velocity used for NH3 led to the largest deviations in the IASI-derived dry NH3 deposition flux and should be focused on in the future. A comparison of NH3 surface concentrations with in-situ measurements of several established networks (EMEP, MAN and LML) showed no significant, or consistent improvement in the IASI-derived NH3 surface concentrations compared to the originally modelled NH3 surface concentrations from LOTOS-EUROS. It is concluded that the IASI-derived NH3 deposition fluxes do not show strong improvements compared to modelled NH3 deposition fluxes and there is future need for better, more robust, methods to derive NH3 dry deposition fluxes.

scholarly journals Technical note: How are NH<sub>3</sub> dry deposition estimates affected by combining the LOTOS-EUROS model with IASI-NH<sub>3</sub> satellite observations?

2018 ◽  
Vol 18 (17) ◽  
pp. 13173-13196 ◽  
Author(s):  
Shelley C. van der Graaf ◽  
Enrico Dammers ◽  
Martijn Schaap ◽  
Jan Willem Erisman
Keyword(s):  
Dry Deposition ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Deposition Velocity ◽  
Monitoring And Evaluation ◽  
Technical Note ◽  
Deposition Flux ◽  
Deposition Fluxes ◽  
Po Valley ◽  
Spatial Coverage

Abstract. Atmospheric levels of reactive nitrogen have increased substantially during the last century resulting in increased nitrogen deposition to ecosystems, causing harmful effects such as soil acidification, reduction in plant biodiversity and eutrophication in lakes and the ocean. Recent developments in the use of atmospheric remote sensing enabled us to resolve concentration fields of NH3 with larger spatial coverage. These observations may be used to improve the quantification of NH3 deposition. In this paper, we use a relatively simple, data-driven method to derive dry deposition fluxes and surface concentrations of NH3 for Europe and for the Netherlands. The aim of this paper is to determine the applicability and the limitations of this method for NH3. Space-born observations of the Infrared Atmospheric Sounding Interferometer (IASI) and the LOTOS-EUROS atmospheric transport model are used. The original modelled dry NH3 deposition flux from LOTOS-EUROS and the flux inferred from IASI are compared to indicate areas with large discrepancies between the two. In these areas, potential model or emission improvements are needed. The largest differences in derived dry deposition fluxes occur in large parts of central Europe, where the satellite-observed NH3 concentrations are higher than the modelled ones, and in Switzerland, northern Italy (Po Valley) and southern Turkey, where the modelled NH3 concentrations are higher than the satellite-observed ones. A sensitivity analysis of eight model input parameters important for NH3 dry deposition modelling showed that the IASI-derived dry NH3 deposition fluxes may vary from ∼ 20 % up to ∼50 % throughout Europe. Variations in the NH3 dry deposition velocity led to the largest deviations in the IASI-derived dry NH3 deposition flux and should be focused on in the future. A comparison of NH3 surface concentrations with in situ measurements of several established networks – the European Monitoring and Evaluation Programme (EMEP), Meetnet Ammoniak in Natuurgebieden (MAN) and Landelijk Meetnet Luchtkwaliteit (LML) – showed no significant or consistent improvement in the IASI-derived NH3 surface concentrations compared to the originally modelled NH3 surface concentrations from LOTOS-EUROS. It is concluded that the IASI-derived NH3 deposition fluxes do not show strong improvements compared to modelled NH3 deposition fluxes and there is a future need for better, more robust, methods to derive NH3 dry deposition fluxes.

Aerosol acidity as a driver of aerosol formation and nutrient deposition to ecosystems

2020 ◽  
Author(s):  
Athanasios Nenes ◽  
Maria Kanakidou ◽  
Spyros Pandis ◽  
Armistead Russell ◽  
Shaojie Song ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particulate Matter ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Liquid Water Content ◽  
Reactive Nitrogen ◽  
Deposition Flux ◽  
Deposition Rates ◽  
Dry Deposition Flux ◽  
Nitrate Aerosol

&lt;p&gt;Nitrogen oxides (NOx) and ammonia (NH&lt;sub&gt;3&lt;/sub&gt;) from anthropogenic and biogenic emissions are central contributors to particulate matter (PM) concentrations worldwide. Ecosystem productivity can also be strongly modulated by the atmospheric deposition of this inorganic &quot;reactive nitrogen&quot; nutrient. The response of PM and nitrogen deposition to changes in the emissions of both compounds is typically studied on a case-by-case basis, owing in part to the complex thermodynamic interactions of these aerosol precursors with other PM constituents. In the absence of rain, much of the complexity of nitrogen deposition is driven by the large difference in dry deposition velocity when a nitrogen-containing molecule is in the gas or condensed phase.&lt;/p&gt;&lt;p&gt;Here we present a simple but thermodynamically consistent approach that expresses the chemical domains of sensitivity of aerosol particulate matter to NH&lt;sub&gt;3&lt;/sub&gt; and HNO&lt;sub&gt;3&lt;/sub&gt; availability in terms of aerosol pH and liquid water content. From our analysis, four policy-relevant regimes emerge in terms of sensitivity: i) NH&lt;sub&gt;3&lt;/sub&gt;-sensitive, ii) HNO&lt;sub&gt;3&lt;/sub&gt;-sensitive, iii) combined NH&lt;sub&gt;3&lt;/sub&gt; and HNO&lt;sub&gt;3&lt;/sub&gt; sensitive, and, iv) a domain where neither NH&lt;sub&gt;3&lt;/sub&gt; and HNO&lt;sub&gt;3&lt;/sub&gt; are important for PM levels (but only nonvolatile precursors such as NVCs and sulfate). When this framework is applied to ambient measurements or predictions of PM and gaseous precursors, the &amp;#8220;chemical regime&amp;#8221; of PM sensitivity to NH3 and HNO3 availability is directly determined.&amp;#160;&lt;/p&gt;&lt;p&gt;The same framework is then extended to consider the impact of gas-to-particle partitioning, on the deposition velocity of NH&lt;sub&gt;3&lt;/sub&gt; and HNO&lt;sub&gt;3&lt;/sub&gt; individually, and combined affects the dry deposition of inorganic reactive nitrogen. Four regimes of deposition velocity emerge: i) HNO&lt;sub&gt;3&lt;/sub&gt;-fast, NH&lt;sub&gt;3&lt;/sub&gt;-slow, ii) HNO&lt;sub&gt;3&lt;/sub&gt;-slow, NH&lt;sub&gt;3&lt;/sub&gt;-fast, iii) HNO&lt;sub&gt;3&lt;/sub&gt;-fast, NH&lt;sub&gt;3&lt;/sub&gt;-fast, and, iv) HNO&lt;sub&gt;3&lt;/sub&gt;-slow, NH&lt;sub&gt;3&lt;/sub&gt;-slow. Conditions that favor strong partitioning of species to the aerosol phase strongly delay the deposition of reactive nitrogen species and promotes their accumulation in the boundary layer and potential for long-range transport.&amp;#160;&lt;/p&gt;&lt;p&gt;The use of these regimes allows novel insights and is an important tool to evaluate chemical transport models. Most notably, we find that nitric acid displays considerable variability of dry deposition flux, with maximum deposition rates found in the Eastern US (close to gas-deposition rates) and minimum rates for North Europe and China. Strong reductions in deposition velocity lead to considerable accumulation of nitrate aerosol in the boundary layer &amp;#8211;up to 10-fold increases in PM2.5 nitrate aerosol, eventually being an important contributor to high PM2.5 levels observed during haze episodes. With this new understanding, aerosol pH and associated liquid water content can be understood as control parameters that drive PM formation and dry deposition flux and arguably can catalyze the accumulation of aerosol precursors that cause intense haze events throughout the globe.&lt;/p&gt;

scholarly journals Elemental carbon in snow at Changbai Mountain, Northeastern China: concentrations, scavenging ratios and dry deposition velocities

2013 ◽  
Vol 13 (5) ◽  
pp. 14221-14248 ◽  
Author(s):  
Z. W. Wang ◽  
C. A. Pedersen ◽  
X. S. Zhang ◽  
J. C. Gallet ◽  
J. Ström ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Elemental Carbon ◽  
Deposition Velocity ◽  
Northeastern China ◽  
Changbai Mountain ◽  
Deposition Flux ◽  
Upper Limit ◽  
The Mean ◽  
Scavenging Ratio ◽  
Scavenging Ratios

Abstract. Light absorbing aerosol, in particular elemental carbon (EC), in snow and ice enhance absorption of solar radiation, reduce the albedo, and is an important climate driver. In this study, measurements of EC concentration in air and snow are performed concurrently at Changbai Station, Northeastern China, from 2009 to 2012. The mean EC concentration for surface snow is 987 &amp;pm; 1510 ng g−1 with a range of 7 to 7636 ng g−1. EC levels in surface snow around (about 50 km) Changbai Mountain are lower than those collected on the same day at Changbai station, and decrease with distance from Changbai station, indicating that EC load in snow around Changbai Mountain is influenced by local source emissions. Scavenging ratios of EC by snow are calculated through comparing the concentrations of EC in fresh snow with those in air. The upper-limit of mean scavenging ratio is 137.4 &amp;pm; 99.7 with median 149.4, which is smaller than those reported from Arctic areas. The non-rimed snow process may be one of significant factors for interpreting the difference of scavenging ratio in this area with the Arctic areas. Finally, wet and dry depositional fluxes of EC have been estimated, and the upper-limit of EC wet deposition flux is 0.46 &amp;pm; 0.38 μg cm−2 month−1 during the three consecutive snow season, and 1.32 &amp;pm; 0.95 μg cm−2 month−1 for dry deposition flux from December to February during study period. During these three years, 77% of EC in snow is attributed to the dry deposition, indicating that dry deposition processes play a major role for EC load in snow in the area of Changbai, Northeastern China. Based on the dry deposition fluxes of EC and hourly black carbon (BC) concentrations in air, the estimated mean dry deposition velocity is 2.81 × 10−3 m s−1 with the mean median of 3.15 × 10−3 m s−1. These preliminary estimates for the scavenging ratio and dry deposition velocity of EC on snow surface will be beneficial for numerical models, and improve simulations of EC transport, fate and radiative forcing in order to ultimately make better climate prediction.

scholarly journals A comparison of dry and wet season aerosol number fluxes over the Amazon rain forest

2009 ◽  
Vol 9 (6) ◽  
pp. 26881-26924
Author(s):  
L. Ahlm ◽  
E. D. Nilsson ◽  
R. Krejci ◽  
E. M. M&amp;aring;rtensson ◽  
M. Vogt ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Rain Forest ◽  
Particle Deposition ◽  
Particle Flux ◽  
Friction Velocity ◽  
Deposition Velocity ◽  
Dry Season ◽  
Wet Season ◽  
Deposition Velocities ◽  
Amazon Rain Forest

Abstract. Vertical number fluxes of aerosol particles and vertical fluxes of CO2 were measured with the eddy covariance method at the top of a 53 m high tower in the Amazon rain forest as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment. The observed aerosol number fluxes included particles with sizes down to 10 nm in diameter. The measurements were carried out during the wet and dry season in 2008. In this study focus is on the dry season aerosol fluxes, with significant influence from biomass burning, and these are compared with aerosol fluxes measured during the wet season. The primary goal is to quantify the dry deposition sink and to investigate whether particle deposition velocities change when going from the clean wet season into the more polluted dry season. Furthermore, it is tested whether the rain forest is always a net sink of particles in terms of number concentrations, or if particle emission from the surface under certain circumstances may dominate over the dry deposition sink. The particle deposition velocity vd increased linearly with increasing friction velocity in both seasons and the relations are described by vdd=(2.7 u* −0.2)×10−3 (dry season) and vdw=2.5 u*×10−3 (wet season), where u* is the friction velocity. The fact that the two relations are very similar to each other indicates that the seasonal change in aerosol number size distribution is not enough for causing any significant change in deposition velocity. In general, particle deposition velocities in this study are low compared to studies over boreal forests. The reason is probably domination of accumulation mode particles in the Amazon boundary layer, both in the dry and wet season, and low wind speeds in the tropics compared to the midlatitudes. Net particle deposition fluxes prevailed in daytime in both seasons and the deposition flux was considerably larger in the dry season due to the much higher dry season particle concentration. In the dry season, nocturnal particle fluxes behaved very similar to the nocturnal CO2 fluxes. Throughout the night, the measured particle flux at the top of the tower was close to zero, but early in the morning there was an upward particle flux peak that is not likely a result of entrainment or local pollution. It is possible that these morning upward particle fluxes are associated with emission of natural biogenic particles from the rain forest. Emitted particles may be stored within the canopy during stable conditions at nighttime, similarly to CO2, and being released from the canopy when conditions become more turbulent in the morning.

scholarly journals Aerosol acidity and liquid water content regulate the dry deposition of inorganic reactive nitrogen

2021 ◽  
Vol 21 (8) ◽  
pp. 6023-6033
Author(s):  
Athanasios Nenes ◽  
Spyros N. Pandis ◽  
Maria Kanakidou ◽  
Armistead G. Russell ◽  
Shaojie Song ◽  
...  
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Liquid Water Content ◽  
Reactive Nitrogen ◽  
Deposition Flux ◽  
Eastern United States ◽  
Total Ammonia ◽  
The Individual

Abstract. Ecosystem productivity is strongly modulated by the atmospheric deposition of inorganic reactive nitrogen (the sum of ammonium and nitrate). The individual contributions of ammonium and nitrate vary considerably over space and time, giving rise to complex patterns of nitrogen deposition. In the absence of rain, much of this complexity is driven by the large difference between the dry deposition velocity of nitrogen-containing molecules in the gas or condensed phase. Here we quantify how aerosol liquid water and acidity, through their impact on gas–particle partitioning, modulate the deposition velocity of total NH3 and total HNO3 individually while simultaneously affecting the dry deposition of inorganic reactive nitrogen. Four regimes of deposition velocity emerge: (i) HNO3 – fast, NH3 – slow, (ii) HNO3 – slow, NH3 – fast, (iii) HNO3 – fast, NH3 – fast, and (iv) HNO3 – slow, NH3 – slow. Conditions that favor partitioning of species to the aerosol phase strongly reduce the local deposition of reactive nitrogen species and promote their accumulation in the boundary layer and potential for long-range transport. Application of this framework to select locations around the world reveals fundamentally important insights: the dry deposition of total ammonia displays little sensitivity to pH and liquid water variations, except under conditions of extreme acidity and/or low aerosol liquid water content. The dry deposition of total nitric acid, on the other hand, is quite variable, with maximum deposition velocities (close to gas deposition rates) found in the eastern United States and minimum velocities in northern Europe and China. In the latter case, the low deposition velocity leads to up to 10-fold increases in PM2.5 nitrate aerosol, thus contributing to the high PM2.5 levels observed during haze episodes. In this light, aerosol pH and associated liquid water content can be considered to be control parameters that drive dry deposition flux and can accelerate the accumulation of aerosol contributing to intense haze events throughout the globe.

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