scholarly journals Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition

2016 ◽  
Vol 16 (5) ◽  
pp. 3145-3160 ◽  
Author(s):  
Üllar Rannik ◽  
Luxi Zhou ◽  
Putian Zhou ◽  
Rosa Gierens ◽  
Ivan Mammarella ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Dry Deposition ◽  
Particle Deposition ◽  
Turbulent Transport ◽  
Flux Measurement ◽  
Vertical Transport ◽  
Forest Site ◽  
Aerosol Dynamics ◽  
Order Of Magnitude ◽  
The Impact

Abstract. A 1-D atmospheric boundary layer (ABL) model coupled with a detailed atmospheric chemistry and aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of 10 days in May 2013 to a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive aerosol transformation. The aim of the study was to analyze and quantify the role of aerosol and ABL dynamics in the vertical transport of aerosols. It was of particular interest to what extent the fluxes above the canopy deviate from the particle dry deposition on the canopy foliage due to the above-mentioned processes. The model simulations revealed that the particle concentration change due to aerosol dynamics frequently exceeded the effect of particle deposition by even an order of magnitude or more. The impact was, however, strongly dependent on particle size and time. In spite of the fact that the timescale of turbulent transfer inside the canopy is much smaller than the timescales of aerosol dynamics and dry deposition, leading us to assume well-mixed properties of air, the fluxes at the canopy top frequently deviated from deposition inside the forest. This was due to transformation of aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of timescales of aerosol dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of aerosol dynamics for vertical transport above the canopy. We conclude that under dynamical conditions reported in the current study the micrometeorological particle flux measurements can significantly deviate from the dry deposition into the canopy. The deviation can be systematic for certain size ranges so that the time-averaged particle fluxes can be also biased with respect to deposition sink.

scholarly journals Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition

2015 ◽  
Vol 15 (14) ◽  
pp. 19367-19403 ◽  
Author(s):  
Ü. Rannik ◽  
L. Zhou ◽  
P. Zhou ◽  
R. Gierens ◽  
I. Mammarella ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Time Scales ◽  
Atmospheric Chemistry ◽  
Dry Deposition ◽  
Particle Deposition ◽  
Vertical Transport ◽  
Forest Site ◽  
Aerosol Dynamics ◽  
The Impact

Abstract. One dimensional atmospheric boundary layer (ABL) model coupled with detailed atmospheric chemistry and aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of ten days in May 2013 for a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive aerosol transformation. Throughout this study we refer to nucleation, condensational growth and coagulation as aerosol dynamical processes, i.e. the processes that govern the particle size distribution evolution. The aim of the study was to analyze and quantify the role of aerosol and ABL dynamics in vertical transport of aerosols. It was of particular interest to what extent the fluxes above canopy deviate due to above mentioned processes from the particle dry deposition on the canopy foliage. The model simulations revealed that the particle concentration change due to aerosol dynamics can frequently exceed the effect of particle deposition even an order of magnitude or more. The impact is however strongly dependent on particle size and time. In spite of the fact that the time scale of turbulent transfer inside canopy is much smaller than the time scales of aerosol dynamics and dry deposition, letting to assume well mixed properties of air, the fluxes at the canopy top frequently deviate from deposition inside forest. This is due to transformation of aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of time scales of aerosol dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of aerosol dynamics for vertical transport within canopy. We conclude that under dynamical conditions the micrometeorological particle flux measurements such as performed by the eddy covariance technique do not generally represent the dry deposition. The deviation can be systematic for certain size ranges so that the conclusion applies also to time averaged particle fluxes.

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.

scholarly journals The influence of weather-driven processes on tropospheric ozone

2021 ◽  
Author(s):  
Tamara Emmerichs ◽  
Bruno Franco ◽  
Catherine Wespes ◽  
Vinod Kumar ◽  
Andrea Pozzer ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Dry Deposition ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Air Pollutant ◽  
Chemical Production ◽  
Ozone Monitoring Instrument ◽  
Near Surface ◽  
The Impact

Abstract. Near-surface ozone is an harmful air pollutant, which is determined to a considerable extent by weather-controlled processes, and may be significantly impacted by water vapour forming complexes with peroxy radicals. The role of water in the reaction of HO2 radical with nitrogen oxides is known from the literature, and in current models the water complex is considered by assuming a linear dependence on water concentrations. In fact, recent experimental evidence has been published, showing the significant role of water on the kinetics of one of the most important reaction for ozone chemistry, namely NO2 + OH. Here, the available kinetic data for the HOx + NOx reactions have been included in the atmospheric chemistry model ECHAM5/MESSy (EMAC) to test its global significance. Among the modified kinetics, the newly added HNO3 channel from HO2 + NO, dominates, significantly reducing NO2. A major removal process of near-surface ozone is dry deposition accounting for 20 % of the total tropospheric ozone loss mostly occurring over vegetation. However, parameterizations for modelling dry deposition represent a major source of uncertainty for tropospheric ozone simulations. This potentially belongs to the reasons why global models, such as EMAC used here, overestimate ozone with respect to observations. In fact, the employed parameterization is hardly sensitive to local meteorological conditions (e.g., humidity) and lacks non-stomatal deposition. In this study, a dry deposition scheme including these features have been used in EMAC, affecting not only the deposition of ozone but of its precursors, resulting in lower chemical production of ozone. Additionally, we improved the emissions of isoprene and nitrous acid (HONO). Namely, for isoprene emissions we have accounted for the impact of drought stress which confers a higher model sensitivity to meteorology leading to reduced annual emissions down to 32 %. For HONO, we have implemented soil emissions, which depend on soil moisture and thus on precipitation. We estimate for the first time a global source strength of 7 Tg(N) a−1. Furthermore, the usage of a parameterization for the production of lightning NOx that depends on cloud top height contributes to a more realistic representation of NO2 columns over remote oceans with respect to the satellite measurements of the Ozone Monitoring Instrument (OMI). The combination of all the model modifications reduces the simulated global ozone burden by ≈ 20 % to 337 Tg, which is in better agreement with recent estimates. By comparing simulation results with measurements from the Infrared Atmospheric Sounding Interferometer (IASI) and the Tropospheric Ozone Assessment Report (TOAR) databases (of 2009) we demonstrate an overall reduction of the ozone bias by a factor of 2.

scholarly journals The global impact of the transport sectors on atmospheric aerosol in 2030 – Part 1: Land transport and shipping

2015 ◽  
Vol 15 (2) ◽  
pp. 633-651 ◽  
Author(s):  
M. Righi ◽  
J. Hendricks ◽  
R. Sausen
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Aerosol ◽  
Radiative Forcing ◽  
Global Climate ◽  
Climate Impact ◽  
Radiation Budget ◽  
Intergovernmental Panel ◽  
Surface Level ◽  
Aerosol Dynamics ◽  
The Impact

Abstract. Using the EMAC (ECHAM/MESSy Atmospheric Chemistry) global climate-chemistry model coupled to the aerosol module MADE (Modal Aerosol Dynamics model for Europe, adapted for global applications), we simulate the impact of land transport and shipping emissions on global atmospheric aerosol and climate in 2030. Future emissions of short-lived gas and aerosol species follow the four Representative Concentration Pathways (RCPs) designed in support of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We compare the resulting 2030 land-transport- and shipping-induced aerosol concentrations to the ones obtained for the year 2000 in a previous study with the same model configuration. The simulations suggest that black carbon and aerosol nitrate are the most relevant pollutants from land transport in 2000 and 2030 and their impacts are characterized by very strong regional variations during this time period. Europe and North America experience a decrease in the land-transport-induced particle pollution, although in these regions this sector remains a major source of surface-level pollution in 2030 under all RCPs. In Southeast Asia, however, a significant increase is simulated, but in this region the surface-level pollution is still controlled by other sources than land transport. Shipping-induced air pollution is mostly due to aerosol sulfate and nitrate, which show opposite trends towards 2030. Sulfate is strongly reduced as a consequence of sulfur reduction policies in ship fuels in force since 2010, while nitrate tends to increase due to the excess of ammonia following the reduction in ammonium sulfate. The aerosol-induced climate impact of both sectors is dominated by aerosol-cloud effects and is projected to decrease between 2000 and 2030, nevertheless still contributing a significant radiative forcing to Earth's radiation budget.

Pound Wise and Penny Foolish? Weight Loss and The Dynamics of Health Care Spending

2011 ◽  
Vol 14 (2) ◽  
Author(s):  
Thomas G Koch
Keyword(s):  
Weight Loss ◽  
Cost Savings ◽  
Cost Effective ◽  
Economic Consequences ◽  
Health Care Spending ◽  
Order Of Magnitude ◽  
Dynamic Measures ◽  
The Cost ◽  
The Impact ◽  
The Relationship

Current estimates of obesity costs ignore the impact of future weight loss and gain, and may either over or underestimate economic consequences of weight loss. In light of this, I construct static and dynamic measures of medical costs associated with body mass index (BMI), to be balanced against the cost of one-time interventions. This study finds that ignoring the implications of weight loss and gain over time overstates the medical-cost savings of such interventions by an order of magnitude. When the relationship between spending and age is allowed to vary, weight-loss attempts appear to be cost-effective starting and ending with middle age. Some interventions recently proven to decrease weight may also be cost-effective.

scholarly journals Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 691
Author(s):  
Yugang Zhao ◽  
Zichao Zuo ◽  
Haibo Tang ◽  
Xin Zhang
Keyword(s):  
Vapor Pressure ◽  
Substrate Temperature ◽  
Water Drop ◽  
Industrial Processes ◽  
Aircraft Icing ◽  
Ice Coverage ◽  
Fundamental Understanding ◽  
Order Of Magnitude ◽  
The Impact ◽  
Kinetics Of

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

Comparison of soot models for reacting sprays in diesel engine-like conditions

2021 ◽  
pp. 095440702110154
Author(s):  
Pavan Prakash Duvvuri ◽  
Rajesh Kumar Shrivastava ◽  
Sheshadri Sreedhara
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Modeling Framework ◽  
Aerosol Dynamics ◽  
Significant Difference ◽  
Polycyclic Aromatic ◽  
Order Of Magnitude ◽  
Detailed Kinetics ◽  
Soot Model

Stringent emission legislations and growing health concerns have contributed to the evolution of soot modeling in diesel engines from simple empirical relations to methods involving detailed kinetics and complex aerosol dynamics. In this paper, four different soot models have been evaluated for the high temperature, high pressure combusting dodecane spray cases of engine combustion network (ECN) spray A which mimics engine-relevant conditions. The soot models considered include an empirical, a multistep, a method of moments based, and a discrete sectional method soot model. Two experimental cases with ambient oxygen volume of 21% and 15% have been modeled. A good agreement between simulations and experiments for vapor penetration and heat release rate has been obtained. Quasi-steady soot volume fraction contours for the four soot models have been compared with experiments. Contours of the species and source terms involved in soot modeling have also been compared for a better understanding of soot processes. The empirical soot model results in higher magnitude and spread of soot due to a lack of modeling framework for oxidation through OH species. Among the four models studied, the multistep soot model has been observed to provide the most promising agreement with the experimental data in terms of distribution of soot and location of peak soot volume fraction. Due to a two-way coupling of soot models, the detailed models predict an upstream location for soot as compared to the multi-step soot model which is one way coupled. A significant difference (of an order of magnitude) in the concentration of PAH (polycyclic aromatic hydrocarbons) precursor between multistep and detailed soot models has been observed because of precursor consumption due to the coupling of detailed soot models with chemical kinetics. It is recommended that kinetic schemes, especially those concerning PAH, be validated with experimental data with a kinetics-coupled soot model.

scholarly journals Application of random forest regression to the calculation of gas-phase chemistry within the GEOS-Chem chemistry model v10

2019 ◽  
Vol 12 (3) ◽  
pp. 1209-1225 ◽  
Author(s):  
Christoph A. Keller ◽  
Mat J. Evans
Keyword(s):  
Machine Learning ◽  
Random Forest ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Random Forest Regression ◽  
Data Set ◽  
Gas Phase Chemistry ◽  
Chemical Conditions ◽  
Phase Chemistry ◽  
The Impact

Abstract. Atmospheric chemistry models are a central tool to study the impact of chemical constituents on the environment, vegetation and human health. These models are numerically intense, and previous attempts to reduce the numerical cost of chemistry solvers have not delivered transformative change. We show here the potential of a machine learning (in this case random forest regression) replacement for the gas-phase chemistry in atmospheric chemistry transport models. Our training data consist of 1 month (July 2013) of output of chemical conditions together with the model physical state, produced from the GEOS-Chem chemistry model v10. From this data set we train random forest regression models to predict the concentration of each transported species after the integrator, based on the physical and chemical conditions before the integrator. The choice of prediction type has a strong impact on the skill of the regression model. We find best results from predicting the change in concentration for long-lived species and the absolute concentration for short-lived species. We also find improvements from a simple implementation of chemical families (NOx = NO + NO2). We then implement the trained random forest predictors back into GEOS-Chem to replace the numerical integrator. The machine-learning-driven GEOS-Chem model compares well to the standard simulation. For ozone (O3), errors from using the random forests (compared to the reference simulation) grow slowly and after 5 days the normalized mean bias (NMB), root mean square error (RMSE) and R2 are 4.2 %, 35 % and 0.9, respectively; after 30 days the errors increase to 13 %, 67 % and 0.75, respectively. The biases become largest in remote areas such as the tropical Pacific where errors in the chemistry can accumulate with little balancing influence from emissions or deposition. Over polluted regions the model error is less than 10 % and has significant fidelity in following the time series of the full model. Modelled NOx shows similar features, with the most significant errors occurring in remote locations far from recent emissions. For other species such as inorganic bromine species and short-lived nitrogen species, errors become large, with NMB, RMSE and R2 reaching >2100 % >400 % and <0.1, respectively. This proof-of-concept implementation takes 1.8 times more time than the direct integration of the differential equations, but optimization and software engineering should allow substantial increases in speed. We discuss potential improvements in the implementation, some of its advantages from both a software and hardware perspective, its limitations, and its applicability to operational air quality activities.

scholarly journals Individual Condensation Trails in Aircraft Trajectory Optimization

2019 ◽  
Vol 11 (21) ◽  
pp. 6082 ◽  
Author(s):  
Judith Rosenow ◽  
Hartmut Fricke
Keyword(s):  
Global Warming ◽  
Trajectory Optimization ◽  
Wind Shear ◽  
Impact Factors ◽  
Factors Influencing ◽  
Order Of Magnitude ◽  
Aircraft Trajectory ◽  
The Impact ◽  
Arbitrary Trajectory ◽  
Significant Factors

Contrails are one of the driving contributors to global warming, induced by aviation. The quantification of the impact of contrails on global warming is nontrivial and requires further in-depth investigation. In detail, condensation trails might even change the algebraic sign between a cooling and a warming effect in an order of magnitude, which is comparable to the impact of aviation-emitted carbon dioxides and nitrogen oxides. This implies the necessity to granularly consider the environmental impact of condensation trails in single-trajectory optimization tools. The intent of this study is the elaboration of all significant factors influencing on the net effect of single condensation trails. Possible simplifications will be proposed for a consideration in single-trajectory optimization tools. Finally, the effects of the most important impact factors, such as latitude, time of the year, and time of the day, wind shear, and atmospheric turbulence as well as their consideration in a multi-criteria trajectory optimization tool are exemplified. The results can be used for an arbitrary trajectory optimization tool with environmental optimization intents.

scholarly journals Analysis of actinic flux profiles measured from an ozonesonde balloon

2015 ◽  
Vol 15 (8) ◽  
pp. 4131-4144 ◽  
Author(s):  
P. Wang ◽  
M. Allaart ◽  
W. H. Knap ◽  
P. Stammes
Keyword(s):  
Atmospheric Chemistry ◽  
Low Cost ◽  
Green Light ◽  
Single Layer ◽  
Radiative Transfer Model ◽  
Cloud Base ◽  
Transfer Model ◽  
Actinic Flux ◽  
Clear Sky ◽  
The Impact

Abstract. A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozonesonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analysed using the Doubling–Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK-simulated actinic flux profiles and the observations for single-layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth further developing the instrument and launching it together with atmospheric chemistry composition sensors.

Sign in / Sign up

Export Citation Format

Share Document