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3D Radiative Aspects of the Increased Aerosol Optical Depth Near Clouds
To characterize aerosol-cloud interactions it is important to correctly retrieve aerosol optical depth in the vicinity of clouds. It is well reported in the literature that aerosol optical depth increases with cloud cover. ...
Sep 21, 2009 ... TARFOX Data and Information ... as well as the chemical, physical, and optical properties, of the aerosols carried over the ... Aerosol Backscattering Coeff, Aerosol Light Scattering Coeff, Cloud Condensation Nuclei, ...
Aerosol mobility size spectrometer
A device for measuring aerosol size distribution within a sample containing aerosol particles. The device generally includes a spectrometer housing defining an interior chamber and a camera for recording aerosol size streams exiting the chamber. The housing includes an inlet for introducing a flow medium into the chamber in a flow direction, an aerosol injection port adjacent the inlet for introducing a charged aerosol sample into the chamber, a separation section for applying an electric field to the aerosol sample across the flow direction and an outlet opposite the inlet. In the separation section, the aerosol sample becomes entrained in the flow medium and the aerosol particles within the aerosol sample are separated by size into a plurality of aerosol flow streams under the influence of the electric field. The camera is disposed adjacent the housing outlet for optically detecting a relative position of at least one aerosol flow stream exiting the outlet and for optically detecting the number of aerosol particles within the at least one aerosol flow stream.
Aerosol mobility size spectrometer
A device for measuring aerosol size distribution within a sample containing aerosol particles. The device generally includes a spectrometer housing defining an interior chamber and a camera for recording aerosol size streams exiting the chamber. The housing includes an inlet for introducing a flow medium into the chamber in a flow direction, an aerosol injection port adjacent the inlet for introducing a charged aerosol sample into the chamber, a separation section for applying an electric field to the aerosol sample across the flow direction and an outlet opposite the inlet. In the separation section, the aerosol sample becomes entrained in the flow medium and the aerosol particles within the aerosol sample are separated by size into a plurality of aerosol flow streams under the influence of the electric field. The camera is disposed adjacent the housing outlet for optically detecting a relative position of at least one aerosol flow stream exiting the outlet and for optically detecting the number of aerosol particles within the at least one aerosol flow stream.
Understanding Aerosol Direct Radiative Forcing - How Satellites Fit In
The aerosol data products from the NASA Earth Observing System's MISR and MODIS instruments provide significant advances in regional and global aerosol optical depth (AOD) mapping, aerosol type measurement, and ...
Understanding Aerosol Direct Radiative Forcing - How Satellites Fit In
The aerosol data products from the NASA Earth Observing System's MISR and MODIS instruments provide significant advances in regional and global aerosol optical depth (AOD) mapping, aerosol type measurement, and source plume ...
An Emerging Global Aerosol Climatology from the MODIS Satellite Sensors
The recently released Collection 5 MODIS aerosol products provide a consistent record of the Earth's aerosol system. Comparison with ground-based AERONET observations of aerosol optical depth (AOD) we ...
A Simple Model for the Cloud Adjacency Effect and the Apparent Bluing of Aerosols Near Clouds
In determining aerosol-cloud interactions, the properties of aerosols must be characterized in the vicinity of clouds. Numerous studies based on satellite observations have reported that aerosol optical depths increase with ...
Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report
The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles? lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.
Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report
2007-09-30
The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.
1996-12-31
Natural and anthropogenic sources of atmospheric aerosols are reviewed and indications of their concentrations and granulometry are given. Calculation of the lifetime of an atmospheric aerosol of a certain size is presented and the various modes of aerosol granulometry and their relations with photochemical and physico-chemical processes in the atmosphere are discussed. The main physical, electrical and optical properties of aerosols are also presented: diffusion coefficient, dynamic mobility and relaxation time, Stokes number, limit rate of fall, electrical mobility, optical diffraction
2009-03-05
The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.
This study compares aerosol optical depths (AOD) products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and their integrated products ...
Giovanni Online Users Manual: 19. Aerosol Optical Thickness ...
Personal tools ... What are the Giovanni Aerosol Optical Thickness Comparison ( Daily and Monthly) instances? ... Are there any limits on the spatial area or time range that can be selected? ... AOD) is a measure of radiation extinction due to the interaction of radiation with aerosol particles in the atmosphere, ...
Satellite remote sensing of nonspherical tropospheric aerosols
1995-12-31
In this paper the authors discuss the possible effect of nonsphericity of solid tropospheric aerosols on the accuracy of aerosol optical thickness retrievals from reflectance measurements over the ocean surface. To model light-scattering properties of nonspherical aerosols, they use a shape mixture of moderately aspherical, randomly oriented polydisperse spheroids. They assume that the size distribution and refractive index of aerosols are known and use the aerosol optical thickness 0.2 to compute the reflectivity for an atmosphere-ocean model similar to that used in the AVHRR aerosol retrieval algorithms. They then use analogous computations for volume-equivalent spherical aerosols with varying optical thickness to invert the simulated nonspherical reflectance. The computations demonstrate that the use of the spherical model to retrieve the optical thickness of actually nonspherical aerosols can result in errors which, depending on the scattering geometry, can well exceed 100%.
Physical metrology of aerosols; Metrologie physique des aerosols
1996-12-31
The various detection and measuring methods for aerosols are presented, and their selection is related to aerosol characteristics (size range, concentration or mass range), thermo-hydraulic conditions (carrier fluid temperature, pressure and flow rate) and to the measuring system conditions (measuring frequency, data collection speed, cost...). Methods based on aerosol dynamic properties (inertial, diffusional and electrical methods) and aerosol optical properties (localized and integral methods) are described and their performances and applications are compared
CARES: Carbonaceous Aerosol and Radiative Effects Study Science Plan
2010-05-27
Carbonaceous aerosol components, which include black carbon (BC), urban primary organic aerosols (POA), biomass burning aerosols, and secondary organic aerosols (SOA) from both urban and biogenic precursors, have been previously shown to play a major role in the direct and indirect radiative forcing of climate. The primary objective of the CARES 2010 intensive field study is to investigate the evolution of carbonaceous aerosols of different types and their effects on optical and cloud formation properties.
Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties
Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol ...
Gas-and-Aerosol Emission from Forest Fires
Gas and Aerosol Emissions from Forest Fires in Russia: Impacts on Chemical, Radiochemical and Optical Qualities of Atmosphere, Carbon Cycling, Radioecological Consequences, and Biocenosis Sustainability
Features of Aerosol optical depth observed at Barrow, March 10-20, 1983
Total vertical aerosol optical depth over Barrow, Alaska, during March 1983 was up to four times greater than the average for recent years, with part of the excess being due to stratospheric debris from El Chichon. The variability in optical depth during a 10-day period spanning the aircraft flights of the Arctic Gas and Aerosol Sampling Program (AGASP) suggests a major tropospheric aerosol event on March 12 and 13, which accounts for the maximum observed optical depths. Occurrence of the tropospheric event is substantiated with independent aerosol data from aircraft, surface sampling, and synoptic scale meteorological data. Analysis of the Barrow optical depth data yields information on the climatic effects of both the stratospheric aerosol from El Chichon and the tropospheric aerosol commonly called Arctic haze
Aerosol optical depth at Cape Grim, Tasmania 1986-1999
2002-01-01
The aerosol optical depth at 4 wavelengths (368, 500, 778 and 868nm) has been measured automatically at Cape Grim since 1986. The site, on the northwest tip of Tasmania, Australia was chosen to be representative of much of the southern ocean. Fourteen years of measurement have been calibrated and analyzed. The data have been filtered so that only measurements made under on-shore wind conditions are considered. The major feature observed in the record is the eruption of Mt Pinatubo, which resulted in the aerosol optical depth at 500 nm rising to 0.2 – 0.3. If the period of high stratospheric aerosol is ignored, the resulting record shows an average aerosol optical depth near 0.04 for all four wavelengths. In the winter months the observed optical depth correlates well with wind speed. This correlation indicates, that, as an annual average, 40% of the observed aerosol optical depth is due to wind-generated aerosol. The annual cycle of the aerosol optical depth can be understood in terms of the impact of photochemically generated aerosol in the summer months, and an injection of mid-tropospheric aerosol in September, presumably due to biomass burning. Publisher: Research Online Format: application/pdf Source: Faculty of Science - Papers
The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct., the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical ...
The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct., the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical ...
AEROSOL CHARACTERISTICS AND VISIBILITY
This report summarizes progress in measuring the optical properties of aerosols and in relating aerosol characteristics to visibility reduction made in the author's laboratory during the period 1965-1971. An instrument, the integrating nephelometer, which measures the scattering ...
It has been postulated that scattering of sunlight by aerosols can significantly reduce the amount of solar energy absorbed by the climate system. Aerosol measurement programs alone cannot provide all the information needed to evaluate the radiative forcing due to anthropogenic aerosols. Thus, comprehensive global-scale aerosol models, properly validated against surface-based and satellite measurements, are a fundamental tool for evaluating the impacts of aerosols on the planetary radiation balance. Analyzed meteorological fields from the European Centre for Medium-Range Weather Forecasts are used to drive a modified version of the PNL Global Chemistry Model, applied to the atmospheric sulfur cycle. The resulting sulfate fields are used to calculate aerosol optical depths, which in turn are compared to estimates of aerosol optical depth based on satellite observations.
Marine aerosols. (Latest citations from Oceanic abstracts). Published Search
The bibliography contains citations concerning the optical, chemical and physical properties of marine aerosols. The citations examine seasonal variations in aerosol composition, analysis of chemical pollutants contained in the aerosols, and identification of the sources of these pollutants. Attention is also given to mathematical modeling and computerized simulation of marine aerosols. (Contains 250 citations and includes a subject term index and title list.)
Marine aerosols. (Latest citations from Oceanic abstracts). Published Search
1993-03-01
The bibliography contains citations concerning the optical, chemical and physical properties of marine aerosols. The citations examine seasonal variations in aerosol composition, analysis of chemical pollutants contained in the aerosols, and identification of the sources of these pollutants. Attention is also given to mathematical modeling and computerized simulation of marine aerosols. (Contains 250 citations and includes a subject term index and title list.)
Techniques for measuring atmospheric aerosols at the High Resolution Fly's Eye experiment
2005-12-15
We describe several techniques developed by the High Resolution Fly's Eye experiment for measuring aerosol vertical optical depth, aerosol horizontal attenuation length, and aerosol phase function. The techniques are based on measurements of side-scattered light generated by a steerable ultraviolet laser and collected by an optical detector designed to measure fluorescence light from cosmic-ray air showers. We also present a technique to cross-check the aerosol optical depth measurement using air showers observed in stereo. These methods can be used by future air fluorescence experiments.
Stratospheric aerosol measurements from the University of Wyoming balloonborne optical particle counters (OPCs), the Stratospheric Aerosol and Gas Experiment (SAGE) II, and the Halogen Occultation Experiment (HALOE) ...
Thin film-coated plastic optical fiber probe for aerosol chemical sensing applications
2010-01-01
The increasing importance of aerosols in understanding environmental processes as well as the general use of aerosol technologies has led to great interest in aerosol characterization. Thus, we present the development of a thin film-coated plastic optical fiber probe for aerosol chemical composition sensing. To prepare the sensor probe, a small length of cladding was removed from the middle portion of the plastic optical fiber. A thin film of tetraethylorthosilane (TEOS), prepared using the sol-gel technique, was deposited on the surface of the unclad portion of the fiber via dip coating. Sensor responses are reported for various aerosols and are found to be encouraging. The thin film-coated plastic optical fiber is found to increase the sensitivity of the sensor. A plastic fiber optic aer...
2004-01-01
We present an update on the status of the global climatology of the aerosol column optical thickness and Angstrom exponent derived from channel-1 and -2 radiances of the Advanced Very High Resolution Radiometer (AVHRR) in the framework of the Global Aerosol Climatology Project (GACP). The latest version of the climatology covers the period from July 1983 to September 2001 and is based on an adjusted value of the diffuse component of the ocean reflectance as derived from extensive comparisons with ship sun-photometer data. We use the updated GACP climatology and Stratospheric Aerosol and Gas Experiment (SAGE) data to analyze how stratospheric aerosols from major volcanic eruptions can affect the GACP aerosol product. One possible retrieval strategy based on the AVHRR channel-1 and -2 data alone is to infer both the stratospheric and the tropospheric aerosol optical thickness ...
2002-02-19
The Twomey effect of enhanced cloud droplet concentration, optical depth, and albedo caused by anthropogenic aerosols is thought to contribute substantially to radiative forcing of climate change over...Full Text Available
Global Maps - earthobservatory.nasa.gov
To explore how key parts of Earth's climate system change from month to month, ... Aerosol Optical Depth 2010-07-00. Aerosol Optical Depth ... the Earth Observatory is part of the EOS Project Science Office located at NASA Goddard Space ...
Analysis of intensive aerosol optical properties measured at the Jungfraujoch station
1997-09-01
Characterisation of atmospheric aerosol optical properties at the Jungfraujoch has been conducted to deliver basic data for comparison with those from NOAA baseline atmospheric monitoring stations. (author) 2 figs., 2 refs.
A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES
Satellite data provide new opportunities to study the regional distribution of particulate matter. The aerosol optical depth (AOD) - a derived estimate from the satellite-measured radiance, can be compared against model estimates to provide an evaluation of the columnar ae...
A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES
Satellite data provide new opportunities to study the regional distribution of particulate matter. The aerosol optical depth (AOD) - a derived estimate from the satellite measured irradiance, can be compared against model derived estimate to provide an evaluation of the columnar ...
Characteristics of aerosol types from AERONET sunphotometer measurements
2010-01-01
By using observations from the Aerosol Robotic Network (AERONET), aerosol types are classified according to dominant size mode and radiation absorptivity as determined by fine-mode fraction (FMF) and single-scattering albedo (SSA), respectively. The aerosol type from anthropogenic sources is significantly different with regard to location and season, while dust aerosol is observed persistently over North Africa and the Arabian Peninsula. For four reference locations where different aerosol types are observed, time series and optical properties for each aerosol type are investigated. The results show that aerosol types are strongly affected by their sources and partly affected by relative humidity. The analysis and methodology of this study can be used to compare aerosol classification resu...
Optical and microphysical parameters of arid dust aerosol
2010-01-01
The parameters of heavily dusty air in an aerosol chamber under the conditions of an arid zone are studied. The transmission, optical density, Angstrom parameter, aerosol absorption coefficient, and visibility range are calculated. The temporal and spectral dependences of the optical parameters are analyzed. The regularities of the particle-size distribution function in strongly inhomogeneous dust aerosol are studied for coarsely (with a diameter more than 1 m) and finely dispersed (with a diameter of less than 1 m) fractions. The sizes and concentrations of the aerosol particles in air were determined using a photoelectric aerosol counter together with a 15-channel analyzer. We present the absorption spectra of coarsely and finely dispersed dust aerosol collected under different meteo...
Optimization of DBTT of Eurofer ODS steel by Controlled Heat Treatment
2007-01-01
Full text of publication follows: Eurofer ODS is a potential candidate for fusion reactor application due to its excellent swelling resistance and high temperature properties. One of the main issues is that high fluence neutron irradiation induces a significant increase of ductile-to-brittle transition temperature (DBTT) at temperatures below 400 deg. C which restricts its application. The aim of this study is to lower the initial DBTT of Eurofer ODS steel by heat treatment optimization. Two heats of Eurofer ODS steels with different C contents are heat-treated at different normalized temperatures, cooling rates and tempered conditions. Their microstructure is characterized by optical microscopy, FEG-TEM and OIM-EBSD techniques. The effect of normalization, cooling rate and temper on grain size, precipitation, grain boundary chemistry, grain boundary ...
Effect of heat treatment on microstructure and hardness of Eurofer 97, Eurofer ODS and T92 steels
2009-01-01
Eurofer ODS steel is a potential candidate for fusion reactor application due to its excellent swelling resistance, low thermal expansion coefficient and high temperature properties. One of the main issues is that high fluence neutron irradiation induces a significant increase of ductile-to-brittle transition temperature (DBTT) at temperatures below 400 deg. C which restricts its application. The aim of this study is to explore the methods to lower the initial DBTT of Eurofer ODS steel by heat treatment optimization. Two heats of Eurofer ODS steels with different C contents are heat-treated at different normalizing temperatures, cooling rates and tempering conditions, and are compared with Eurofer 97 and T92 steels heat-treated with similar conditions. The microstructure is characterized by optical microscopy, FEG-TEM and OIM-EBSD techniques. The effect of ...
Far infrared laser frequencies of CH3OD and N2H4
The frequencies of 26 laser lines with wavelengths between 57 and 534 microns are measured in the optically pumped laser gases CH3OD and N2H4. A pair of 12CO2 lasers are employed as a frequency standard for the heterodyne ...
Mechanical and microstructural properties of a hipped RAFM ODS-steel
2002-12-01
Oxide dispersion strengthened (ODS) materials for structural applications in future fusion power reactors would allow to increase the operating temperature to approximately 650 deg. C. Two ODS variants of the 9%CrWVTa-RAFM steel EUROFER 97 with Y{sub 2}O{sub 3} contents of 0.3 and 0.5 wt% have been produced. The microstructure of both powder and compacted material has been characterised by means of optical and electron microscopy (SEM, TEM). Tensile tests performed between RT and 850 deg. C show an increase of yield strength and ultimate tensile strength by 50% and more compared to the basic steel. The ductility values are sufficiently high. Creep tests between 600 and 700 deg. C up to test times of 5000 h confirm the superior creep strength of ODS-EUROFER. Impact tests reveal a similar impact behaviour to comparable ODS alloys, but the ductile-to-brittle transition temperature is substantially higher than that of EUROFER 97. Preliminary results of low-cycle fatigue show a promising fatigue behaviour of ODS-EUROFER.
Long-term monitoring of aerosol optical properties at a boreal forest AERONET site in interior Alaska was performed from 1994 through 2008 (excluding winter). Large interannual variability was observed, with some ...
Studies of the stratosphere aerosol layer based on polarization measurements of the twilight sky
2009-01-01
The paper is devoted to an analysis of observational manifestations of the aerosol layer in the Earths stratosphere and to a method of determining their optical properties. It is based on polarization measurements of the twilight sky background in the zenith vicinity and in a broad spectral band with an effective wavelength of 5250 . An increased abundance of the stratosphere aerosol was found in December 2006 for the first time in several years of observation. The suggested method allows one to determine the ratio of radiation scattering coefficients by the stratosphere aerosol and by air molecules, as well as the degree of polarization of aerosol scattering in the stratosphere. The appearance of the stratosphere aerosol is associated with explosive eruption of Rabaul volcano having ...
Field studies of a geo-engineering method of maintaining a modern climate with aerosol particles
2009-01-01
The paper describes the results of the field experiment on studying solar radiation transmission in the visible wavelength range through model aerosol media formed in the lower troposphere with the help of generators installed aboard helicopters. The refractive index and the average size of the aerosol particles formed are close to those characteristic of the natural stratospheric aerosol. The composition of the equipment complex used to control aerosol optical and microphysical aerosol parameters is considered. The measurement results are in satisfactory agreement with the results of theoretical and experimental studies in simulation chambers.
2002-03-01
The Multi-Angle Imaging Spectro-Radiometer (MISR) onboard the NASA satellite Terra observes the earth with 9 cameras at different view angles and at 4 spectral bands. Geo-rectified radiances at 275 m and 1100 m resolution are available. On a 17.6 km scale, an aerosol operational product is delivered, which includes gridded aerosol optical depths and aerosol mixtures typical for maritime and continental environments. In a preliminary study we analyzed data taken on September 11, 2000 and compared the aerosol optical depth (AOD) with sunphotometer measurements at Bern. (author)
Light scattering artefacts in a funnel phantom using optical CT
2009-01-01
A gelatin phantom containing a funnel-shaped region of high opacity (or optical density OD) was used to examine light-scattering induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To correctly simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. In line profiles of OD taken from 3-D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' artefact, while those of short pathlength exhibited the opposite effect - 'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light
1980-01-01
The phase I GAMETAG (global atmospheric measurements experiment of tropospheric aerosols and gases) aerosol measurements were to provide an initial assessment of the levels, types, and optical effects of tropospheric aerosols in remote marine and continental regions and examine the possible causal relationships between the observed distributions and the dominant factors controlling aerosol population. The aerosol population consists primarily of crustal aerosols with r less than or equal to 0.5 micrometer and sulfate and combustion aerosols with r < 0.5 micrometer, with only a minor sea salt component. Owing to vertical mixing, there are no qualitative differences between the boundary layer and the free troposphere. Our data indicate that crustal aerosols represent a significant component of a background tropospheric aerosol in western North America. Pacific marine measurements show a qualitative difference between the boundary layer and the free troposphere. The boundary-layer aerosol population is dominated by a bimodal sea spray aerosol; optical effects and mass concentration are dominated by a mode with a volume mean radius of approx 1 micrometer. Our measurements show only a small crustal component of the marine boundary-layer aerosol. We have inferred a background concentration of 0.2 ppBM for our measured particles that does not appear to be directly related to the sea spray aerosol. We have identified some of these particles as locally produced secondary aerosols; simultaneous measurements of gaseous species support this interpretation. Our Pacific free tropospheric aerosol measurements show a highly variable aerosol component, with local variations in concentration by 1 order of magnitude within a few kilometers. Our measured total aerosol and crustal component concentrations show a general decrease from north to south.
Experimental evaluation of atmospheric aerosol turbidity in different Atlantic regions
1994-12-31
The statistical estimation of the experimental values of atmospheric turbidity are considered over the different Atlantic regions: from clean atmospheric conditions to very turbid conditions influenced by air masses from Africa containing continental Sahara aerosol. The factors influencing the variability of atmospheric turbidity are also analyzed. The contribution of aerosol to atmospheric attenuation of the direct solar radiation is estimated. It is shown that aerosol is the main factor determining the values of the optical thickness and its variability. The single scattering albedo is evaluated. The influence of the Sahara dust on the total solar radiation over the ocean surface is estimated. Based on the found relationship between aerosol optical thickness, total atmosphere, and aerosol turbidity in the surface layer, the height of the homogeneous atmosphere has been estimated. In addition, the aerosol generation by ocean surface in storm conditions has been considered.
2010-01-01
The White Light Aerosol Spectrometer (welas) is an alternative method to multistage cascade impaction in the analysis of particle-size distribution (PSD) that allows measurements in high concentrations by single particle measurement. Correspondence of the PSD measured by the welas system in combination with a new aerosol sampling system has been discussed before for aqueous aerosols from nebulisers [M. Kuhli, M. Weiss, H. Steckel, A sampling and dilution system for droplet aerosols from medical nebulisers developed for use with an optical particle counter, Journal of Aerosol Science 40 (2009) 523-533]. For aerosols from solution-based pressurised metered-dose inhalers (pMDI), both the apparent density and the dynamic shape factor of the dry solid particles come into account for correlation...
2007-01-01
The large spatial and temporal variability of atmospheric aerosol load makes it a challenge to quantify aerosol effect on climate. This study is one of the first attempts to apply data assimilation for the analysis of global aerosol distribution. Aerosol optical thickness (AOT) observed from the Polarization and Directionality of the Earth Reflectances (POLDER) space-borne instrument are assimilated into a three-dimensional chemistry model. POLDER capabilities to distinguish between fine and coarse AOT are used to constrain them separately in the model. Observation and model errors are a key component of such a system and are carefully estimated on a regional basis using some of the high-quality surface observations from the Aerosol Robotic Network (AERONET). Other AERONET data provide an independent evaluation of the a posteriori fields. Results for the fine mode show ...
2006-01-01
The main aim of this work is to assess the performance of the Total Ozone Mapping Spectrometer (TOMS) on board the Earth Probe satellite aerosol index (AI) version 8.0 retrieved from the daily measurements of the TOMS instrument as an indicator of the presence of absorbing aerosols in the atmosphere. The analysis is carried out over the region of Northern Greece, an area exposed to various aerosol types from different sources. The aerosol optical depth (AOD) measured by a Brewer spectroradiometer situated in the centre of the city of Thessaloniki, at 40.6degreeN, 22.9degreeE, was employed as a measure of the aerosol loading in the atmosphere during the Earth Probe overpass. Discrete aerosol episodes that affect the area, such as biomass burning and Saharan dust events, have been isolated a...
Sonic and optical manipulation and sorting of aerosols.
2006-05-19
DescriptionThe study of aerosols is of great importance in the area of atmospheric science. The way in which aerosols interact and react with each other, their composition, morphology and size are all of importance in this area. The ability to study individual aerosol droplets is therefore an very useful technique. Making use of lasers we can carry out spectroscopic measurements that can provide very detailed information about the droplets. However in many current experiments this ability is hampered by th [continued...]
Some results of an experimental study of the atmospheric aerosol in Tomsk: A combined approach
1996-04-01
As widely accepted, aerosols strongly contribute to the formation of the earth`s radiation balance through the absorption and scattering of solar radiation. In addition, aerosols, being active condensation nuclei, also have a role in the cloud formation process. In this paper, results are presented of aerosol studies undertaken at the field measurement sites of the Institute of Atmospheric Optics in Tomsk and the Tomsk region.
The various methods of calculating the atmospheric aerosol backscattering function, beta(CO2), both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed ...
Measurement of the optical and physical properties of aerosols in the free troposphere
2007-11-16
DescriptionAerosols play an important role in controlling the processes of the upper troposphere. The quantification of aerosol behaviour is a complex problem, because of their high degree of temporal and spatial variability and, in the case of cloud forcing, the non-linear relationship of the processes and the presence of complex feedback mechanisms. In recent years the importance of accurately accounting for aerosol processes within global climate models has become recognised and much progress has been m [continued...]
Aerosol models of the atmosphere. Aerozol'nye modeli atmosfery
1981-01-01
An examination is made of research results obtained from the international program of global atmospheric studies program (PIGAP) jointly undertaken by the USSR and the USA. Detailed information is given on the formation of the basic types of tropospheric and stratospheric aerosols and their physico-chemical properties. Also discussed are the formalization of radiation characteristics of an aerosol for the purpose of developing adequate optical aerosol models of the atmosphere.
2005-07-01
Measurements on aerosol spectral optical depths and near surface mass-size distributions made at several locations in the states of Andhra Pradesh, Orissa and Chattisgarh, constituting the northeastern part of the peninsular India during the ISRO-GBP land campaign-I-show significant regional variations in aerosol physical properties. Higher spectral optical depths, were observed in the coastal regions and over southern latitudes. The optical depths, size index ''{alpha}'' and the near surface aerosol mass concentrations indicate a relative abundance of nucleation mode aerosols in the northern latitudes, in contrast to the dominance of the accumulation mode aerosols at the eastern coastal and southern latitudes. The airmass pathways derived from the back trajectory analysis indicate that the higher aerosol population in the accumulation mode, and consequently the higher optical depths in the southern locations, could be due to the transport of aerosol from the polluted north Indian regions via the oceanic region over the Bay of Bengal, where significant particle growth is expected, increasing the population of accumulation mode aerosols over these regions. (orig.)
2005-03-18
Aerosol extinction profiles measured by the Department of Energy Atmospheric Radiation Measurement (ARM) Climate Research Facility Raman lidar are used to evaluate aerosol extinction profiles and aerosol optical thickness (AOT) simulated by aerosol models as part of the Aerosol module inter- Comparison in global models (AEROCOM) project. This project seeks to diagnose aerosol modules of global models and subsequently identify and eliminate weak components in aerosol modules used for global modeling; AEROCOM activities also include assembling data sets to be used in the evaluations. The AEROCOM average aerosol extinction profiles typically show good agreement with the Raman lidar profiles for altitudes above about 2 km; below 2 km the average model profiles are significantly (30-50%) lower than the Raman lidar profiles. The vertical variability in the average aerosol extinction profiles simulated by these models is less than the variability in the corresponding Raman lidar pro files. The measurements also show a much larger diurnal variability than the Interaction with Chemistry and Aerosols (INCA) model, particularly near the surface where there is a high correlation between aerosol extinction and relative humidity.
2009-01-01
A series of campaigns involving a systematic investigation of the atmosphere over an urban area of Sofia city were carried out. A European Aerosol Research Lidar Network (EARLINET) scanning aerosol lidar, a spectroradiometer, a standard sun photometer and a ground meteorological station were used in the observations. Multiple aerosol layers of variable thickness (200-600 m) were observed systematically in the planetary boundary layer (PBL) over the study area and the experimental data were compared with theoretical data. A study of the optical characteristics of the atmospheric aerosol, including the extinction coefficient, aerosol optical depth (AOD) and Angstrom parameters α and β, was performed and their variations followed during the convective boundary layer (CBL) for...
2003-03-01
Since December 1999 the Multi-Angle Imaging Spectro-Radiometer (MISR) onboard the NASA satellite Terra observes the earth at 9 different view angles and at 4 spectral bands. This instrument is particularly suited to retrieve the angular and spectral dependencies of radiation scattered by aerosols. A novel algorithm is proposed that enables the simultaneous retrieval of surface reflectance and aerosol optical depth. (author)
Optical Properties of Atmospheric Aerosol in Maritime Environments
a large fraction of coarse mode aerosol of sea origin (sea salt) in the size distribution. ... and sources of aerosol presented in a historical perspective give a full- ..... in the tropical zone of the Atlantic ocean, Soviet Meteorology ..... Sakunov, G.G., et al., 1981: Optical properties of the Arctic atmosphere ...
Airborne Lidar Measurements of Aerosol Optical Properties During ...
One MPL was located at Skukuza in Kruger National Park in South Africa, the ..... Figure 7 shows an example from August 24, 2000 off the east coast of South ..... extinction cross section and inference of aerosol imaginary index in the ... Figure 2: Composite map of CPL-derived 1064 nm PBL aerosol optical depth. ...
Quantifying regional aerosol sources using space-borne observations of aerosol optical properties
DescriptionAtmospheric aerosols are tiny particles suspended in the air. The concentration and composition of atmospheric aerosols has serious implications for climate, air pollution, and human health. The largest man-made source is from the burning of fossil fuels (cars, power plants), while natural sources include desert dust, volcanoes, forest fires, and sea spray. The main sinks of aerosols include gravitational settling and scavenging due to rain, leading to atmospheric lifetimes of typically a few da [continued...]
PVC smoke and CsI aerosol mixture in moist atmosphere. An experimental study
1993-12-31
The mixture of hygroscopic CsI aerosol simulating nuclear aerosol and smoke from PVC cable fire were studied in a small scale reactor chamber. The atmosphere in the chamber represents the post-accident situations in nuclear reactor or reactor containment area. Changes with time in mixture aerosols were measured by optical particle counter (OPC). The aim of these experiments was to study experimentally the effect of PVC cable smoke and hygroscopic CsI aerosol mixture to humidity level in the reactor chamber. (12 refs., 4 figs.).
Fission-fragment attachment to aerosols and their transport through capillary tubes
1981-01-01
The transport of radioactive aerosols was studied using equipment, collectively called the Helium jet, that has been constructed to provide basic nuclear physics data on fission product nuclides. The transport of the fission products in the system depends on their attachment to aerosol particles. The system consists of 1) a tube furnace which generates aerosols by the sublimation or evaporation of source material, 2) a helium stream used to transport the aerosols, 3) a 25 m settling tube to eliminate the larger aerosols and smaller aerosols that would deposit in the capillary, 4) a Californium-252 self-fissioning source of fission product nuclides, and 5) a small capillary to carry the radioactive aerosols from the hot cell to the laboratory. Different source materials were aerosolized but NaCl is generally used because it yielded the highest transport efficiencies through the capillary. Particle size measurments were made with NaCl aerosols by using a cascade impactor, an optical light scattering device, and the capillary itself as a diffusion battery by performing radiation measurements and/or electrical conductivity measurements. Both radioactive and nonradioactive aerosols were measured in order to investigate the possibility of a preferential size range for fission product attachment. The measured size distributions were then used to calculate attachment coefficients and finally an attachment time.
Optimization of DBTT of Eurofer ODS steel by Controlled Heat Treatment
2007-07-01
Full text of publication follows: Eurofer ODS is a potential candidate for fusion reactor application due to its excellent swelling resistance and high temperature properties. One of the main issues is that high fluence neutron irradiation induces a significant increase of ductile-to-brittle transition temperature (DBTT) at temperatures below 400 deg. C which restricts its application. The aim of this study is to lower the initial DBTT of Eurofer ODS steel by heat treatment optimization. Two heats of Eurofer ODS steels with different C contents are heat-treated at different normalized temperatures, cooling rates and tempered conditions. Their microstructure is characterized by optical microscopy, FEG-TEM and OIM-EBSD techniques. The effect of normalization, cooling rate and temper on grain size, precipitation, grain boundary chemistry, grain boundary misorientation, hardness, and DBTT are investigated. Monte Carlo models of precipitation are used with thermodynamic software MTDATA to forecast the phase evolution kinetics in Eurofer ODS. The predicted results are compared with experimental data. (authors)
Characteristic results and prospects of the 13Cr-1W-0.3Ti-0.3Y{sub 2}O{sub 3} ODS steel
2009-04-30
For specific blanket and divertor applications in future fusion power reactors a replacement of presently considered reduced activation ferritic martensitic (RAFM) steels as structural material by suitable oxide dispersion strengthened (ODS) ferritic martensitic steels would allow a substantial increase of the operating temperature from {approx}550 deg. C to about 650 deg. C. Temperatures above 700 deg. C in the He cooled modular divertor concept necessitates the use of ferritic (RAF) ODS steels, which are not limited by a phase transition. Therefore a 13Cr-1W-0.3Ti-0.3Y{sub 2}O{sub 3} ferritic ODS steel is being developed, using an Attritor with varying milling parameters. Afterwards the mechanically alloyed powders were encapsulated, sealed and consolidated in a hot isostatic press device. In this work, the effects of several parameter variations on the microstructure of the produced ferritic ODS-alloys, analysed by optical microscopy (OM) and high resolution TEM, as well as results of conducted mechanical tests are presented.
Strategies for Improved CALIPSO Aerosol Optical Depth Estimates
In the spring of 2010, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) project will be releasing version 3 of its level 2 data products. In this paper we describe several changes to the ...
Strategies for Improved CALIPSO Aerosol Optical Depth Estimates
In the spring of 2010, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) project will be releasing version 3 of its level 2 data products. In this paper we describe several changes to the ...
Spectral Absorption Properties of Atmospheric Aerosols
We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We ...
Short-term Aerosol Trends: Reality or Myth
The main questions addressed in this slide presentation involve short-term trends of MODIS aerosol optical thickness (AOT) over 6 years: (1) Why are the trends different in different regions (2) How are these trends so high ...
Short-term Aerosol Trends: Reality or Myth
The main questions addressed in this slide presentation involve short-term trends of MODIS aerosol optical thickness (AOT) over 6 years: (1) Why are the trends different in different regions (2) How are these trends ...
Limitations of Remotely Sensed Aerosol as a Spatial Proxy for Fine Particulate Matter
2009-06-01
BackgroundRecent research highlights the promise of remotely sensed aerosol optical depth (AOD) as a proxy for ground-level particulate matter with aerodynamic diameter ≤...Full Text Available
2009-07-21
Our ability to predict how global temperatures will change in the future is currently limited by the large uncertainties associated with aerosols. Soot aerosols represent a major research focus as they...Full Text Available
HAZE OVER EASTERN NORTH AMERICA. PART 1. HAZE PROPERTIES
The fundamental properties of atmospheric aerosols pertinent to atmospheric optics are the size, shape, and refractive index for the entire aerosol population at a given point. Once these properties are established, their interaction with visible radiation can be calculated, and ...
An emerging ground-based aerosol climatology: Aerosol Optical ...
deciduous trees leafed out from late April through October. ..... Algeria, Libya and Chad. N'Tchayi et al., [1997]has shown that, in addition to ..... addition to the production of pollen in the spring, coniferous forests also produce ...
Aerosol and Cloud Interaction Observed From High Spectral Resolution Lidar Data
Recent studies utilizing satellite retrievals have shown a strong correlation between aerosol optical depth (AOD) and cloud cover. However, these retrievals from passive sensors are subject to many limitations, including ...
A New Look at Aerosol Optical Models in the MODIS/AERONET ERA
The MODerate resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite will permit the first time operational satellite retrievals of atmospheric aerosols over land. The retrieval uses dynamic ...
A New Look at Aerosol Optical Models in the MODIS/AERONET ERA
The MODerate resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite will permit the first time operational satellite retrievals of atmospheric aerosols over land. The retrieval uses dynamic ...
Recent studies have shown that the forecasting capability of an aerosol model can be significantly improved through the assimilation of aerosol retrievals from the operational MODIS aerosol products. The MISR aerosol product, with its unique multi-angle capability, could complement the MODIS aerosol data for data assimilation in various ways. For example, MISR aerosol retrievals are available over areas such as deserts and ocean glint regions that are not included in the operational MODIS aerosol products. Using nine years of collocated MISR and AERONET data, our study suggested that the quality of both over ocean and over land MISR aerosol products meet the published expectations. However, a quality assurance step is necessary to remove outliers before applying the MISR aerosol product to aerosol assimilation. The uncertainties in MISR aerosol product were evaluated as functions of observation conditions and aerosol properties. Quality assurance procedures were developed and a data-assimilation (DA) quality level 3 MISR aerosol product was constructed. The newly developed DA quality MISR product was inter-compared with the DA quality MODIS aerosol products, and was evaluated for its usage in aerosol modeling studies. Last, both DA quality MODIS and MISR aerosol products were used in the data assimilation for multi-sensor data fusion.
Remote sensing of aerosols over the Solar Village, Saudi Arabia
2008-01-01
Aerosol optical properties over Solar Village, Saudi Arabia have been studied using ground-based remote sensing observations through the Aerosol Robotic Network (AERONET). Our analysis covered 8 recorded years of aerosol measurements, starting from February 1999 through January 2007. The seasonal mean values of aerosol optical thickness (AOT), the ngstrm wavelength exponent and the surface wind speed (V), exhibit a one year cyclical pattern. Seasonal variations are clearly found in the shape and magnitude of the volume size distribution (VSD) of the coarse size mode due to dust emission. The Spring is characterized by dusty aerosols as the modal value of the exponent was low ~0.25 while that of AOT was high ~0.3. The modal value of wind speed was the highest ~3.6m/s in spring. ...
2010-01-01
Extensive aerosol optical properties, particle size distributions, and Aerodyne quadrupole aerosol mass spectrometer measurements collected during TRAMP/TexAQS 2006 were examined in light of collocated meteorological and chemical measurements. Much of the evident variability in the observed aerosol-related air quality is due to changing synoptic meteorological situations that direct emissions from various sources to the TRAMP site near the center of the Houston-Galveston-Brazoria (HGB) metropolitan area. In this study, five distinct long-term periods have been identified. During each of these periods, observed aerosol properties have implications that are of interest to environmental quality management agencies. During three of the periods, long range transport (LRT), both intra-continenta...
2010-01-01
Aerosols have been shown to affect the quantity and quality of solar radiation on the Earths surface. Savanna regions are subject to frequent burning and release of aerosols that may impact on radiation components and possibly vegetation productivity in this region. Therefore, in this study, we have analyzed the optical properties of aerosols (aerosol optical depth (AOD) and Angstrom coefficient) from the Atmospheric Radiation Measurement site in Darwin for the periods from April 2002 to June 2005 as measured by a multifilter rotating shadowband radiometer. The influence of aerosols and their effect on surface shortwave incoming solar radiation and savanna productivity were examined for the dry season using sky radiation collection of radiometers and eddy covariance measurements from th...
2006-01-01
The quantification strategy presented in this study is based on simultaneous measurements of laser ablation ICP-MS signal intensities and aerosol particle size distributions. Together with the bulk density of the sample ablated, this allows assessment of the relative mass of the particles introduced into the ICP-MS. This mass was reduced by the particles larger than the ionisation size limit of the ICP and was used to correct for variations in sample ablation and aerosol transport, allowing non matrix-matched calibration without using an internal standard element. A constant fraction of the aerosol (1%) was separated and diluted by a bucket wheel aerosol diluter and particle size distributions were measured by light scattering measurements in the diluted aerosol using an optical particle c...
Spatial mapping of aerosols on the basis of airborne imaging spectroscopy
2002-03-01
Quantification of the change in upwelling radiance at the top of atmosphere due to the presence of tropospheric aerosols (aerosol optical effect) by means of airborne imaging spectroscopy is a prerequisite for spatial mapping of aerosol parameters, such as optical depth and size distribution. In turn, the retrieval of Earth surface bio-/geophysical parameters from spectral imagery, e.g. chlorophyll content of vegetation, needs correction of the atmospheric radiance. The problem of separation between radiative contributions of surface and atmosphere in the spectrometer signal based on image pixels, especially over land areas, is being addressed in this work. (author)
The relationship between aerosol and drop size distributions in the marine atmosphere
1990-12-01
The characteristics of droplet size distributions near cloud base are initially determined by the aerosol particles that act as cloud condensation nuclei (CCN). Through physical and chemical processes that determine the fraction of aerosol particles that act as CCN, these particles profoundly affect the microphysical structure of clouds and their tendency to form precipitation. This paper provides a parametric study of the condensational growth on aerosol distributions from typical measurements in the marine atmosphere, and answers the following questions with respect to this process. (1) How does the condensationally produced droplet spectrum vary with the initial aerosol size distribution, aerosol number loading, and the updraft velocity (2) What is the fraction of aerosol particles that act as CCN This information can be applied to the future study to parameterize the number concentration of cloud droplets in climate models. (3) How do the optical properties of the cloud change as a result of the production of different droplet size distributions 8 figs.
African aerosol and large-scale precipitation variability over West Africa
2009-01-01
We investigated the large-scale connection between African aerosol and precipitation in the West African Monsoon (WAM) region using 8-year (2000-2007) monthly and daily Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol products (aerosol optical depth, fine mode fraction) and Tropical Rainfall Measuring Mission (TRMM) precipitation and rain type. These high-quality data further confirmed our previous results that the large-scale link between aerosol and precipitation in this region undergoes distinct seasonal and spatial variability. Previously detected suppression of precipitation during months of high aerosol concentration occurs in both convective and stratiform rain, but not systematically in shallow rain. This suggests the suppression of deep convection due to the aerosol. Based on the seasonal cycle of dust and smoke and their ...
Aerosol Parameter Inversion Over Land With Imaging Spectroscopy Using A Reference Spectrum Database
2003-03-01
A new method for aerosol parameter retrieval over land from airborne imaging spectroscopy is proposed that makes use of the contiguous and high-resolution spectral coverage of these data. Based on decomposition of the short-wave infrared (SWIR) sensor signal by pre-selected surface reflectance spectra, and assuming low aerosol radiative influence in the SWIR, surface reflectance in the visible is obtained, where aerosol influence is generally strongest. Numerical inversion leads to spatial mapping of aerosol parameters, such as aerosol optical depth {tau}, over land. Spectral autocorrelation of surface reflectances is a pre-condition, demonstrated for natural surfaces using a reference spectrum database. Our results show more realistic pictures of spatial aerosol distributions over land than obtained with existing methods. (author)
Status of optical disk (OD) technology for storage of seismic, geologic, and other information
1987-05-01
Advancements in the technology required for transcribing data from magnetic tape and the rapid optical scanning of written materials with subsequent recording by laser onto optical disk have been great. Energy Laser Storage, Inc. (ELSI), has developed systems for transcribing magnetic tapes containing seismic data and their associated documentation along with other data and geologic information onto OD storage. Advantages of this cost-effective conversion are (1) reduction of required storage volume; (2) elimination of required temperature- and humidity-controlled storage; (3) ruggedness and permanence of the OD storage medium; (4) access time to data greatly reduced; (5) transferability of materials, data, maps, etc, between offices in a streamlined, confidential manner; and (6) capital equipment utilized for systems is less expensive than mainframe computers and peripherals. The systems are compact and come in two distinct configurations: one for tape/optical disk copying and one for paper or film/optical disk transcription. The tape/optical disk system is comprised of a single tape drive with multiple density read/write capability. The paper or film/optical disk system consists of a scanner which can scan documents as wide as 42 in. Both systems are configured around a high-speed IBM-PC/AT central processor and have a single optical disk drive. A laser printer is used for output when reproducing documents from OD. The time has come for the miniaturization of their massive accumulations of data. Exact duplicates of the originals can be available in a few seconds even in remote locations by using ODs, and the unnecessary costs of wasted time, magnetic taps, and paper/films can now be minimized.
2009-01-01
Parameterization of the spectral dependence of the optical characteristics of Martian aerosols has been proposed for processing the results of measurements of outgoing radiation. A method for retrieving the altitude profiles of the microphysical characteristics of Martian aerosols from the limb spectrometry of the OMEGA instrument of the Mars Express mission have been developed. For one of the observational sessions, the altitude profiles of the concentration and the modal radius of the size distribution function of aerosol particles retrieved with the proposed parameterization are presented. For the purpose of the interpretation of the data acquired from the optical remote sensing of planetary atmospheres, we consider how the spectral dependence of aerosol optical characteristics, in part...
Strategy for studying nocturnal aerosol optical depth using artificial lights
2008-01-01
In this concept study, we develop a strategy for the monitoring of nighttime aerosol particle optical properties over land using artificial lights on the earth's surface. We demonstrate the possibility of detecting significant aerosol events and deriving variations in aerosol optical depth using the operational linescan system (OLS) on defence meteorological satellite program (DMSP) platforms. Since the OLS instruments have no on-board calibration, only a qualitative study of the potential to estimate aerosol and cloud properties using city lights at night is shown in this paper. The technique is demonstrated using China and India as test regions. With the launch of the visible/infrared imager/radiometer suite (VIIRS) instrument on the national polar-orbiting operational environmental sate...
Aerosol optical depth of the atmosphere over the ocean in the wavelength range 0.37-4 µm
2008-01-01
At least two problems, the climatic impact of aerosols and improvement in techniques for space-borne sensing, require investigation of the spatiotemporal variability of the aerosol optical depth (AOD) over the ocean. The marine atmosphere covers an area 2.5 times greater than the continental atmosphere and has essential differences in the composition and manner of aerosol variability, but the quantity of available data is significantly less. Hence, the importance of measurements of the aerosol optical characteristics in marine expeditions is clear. This paper generalizes the results of investigations of the AOD of the atmosphere carried out in the past decade onboard Russian scientific vessels in different regions of the Atlantic Ocean. Statistical characteristics of the AOD are presented ...
The uncertainties in current estimates of anthropogenic radiative forcing are dominated by the effects of aerosols, both in relation to the direct absorption and scattering of radiation by aerosols and also with respect to aerosol-related changes in cloud formation, longevity, and microphysics (See Figure 1; Intergovernmental Panel on Climate Change, Assessment Report 4, 2008). Moreover, the Arctic region in particular is especially sensitive to changes in climate with the magnitude of temperature changes (both observed and predicted) being several times larger than global averages (Kaufman et al. 2009). Recent studies confirm that aerosol-cloud interactions in the arctic generate climatologically significant radiative effects equivalent in magnitude to that of green house gases (Lubin and Vogelmann 2006, 2007). The aerosol optical depth is the most immediate representation of the aerosol direct effect and is also important for consideration of aerosol-cloud interactions, and thus this quantity is essential for studies of aerosol radiative forcing.
2009-09-01
The uncertainties in current estimates of anthropogenic radiative forcing are dominated by the effects of aerosols, both in relation to the direct absorption and scattering of radiation by aerosols and also with respect to aerosol-related changes in cloud formation, longevity, and microphysics (See Figure 1; Intergovernmental Panel on Climate Change, Assessment Report 4, 2008). Moreover, the Arctic region in particular is especially sensitive to changes in climate with the magnitude of temperature changes (both observed and predicted) being several times larger than global averages (Kaufman et al. 2009). Recent studies confirm that aerosol-cloud interactions in the arctic generate climatologically significant radiative effects equivalent in magnitude to that of green house gases (Lubin and Vogelmann 2006, 2007). The aerosol optical depth is the most immediate representation of the aerosol direct effect and is also important for consideration of aerosol-cloud interactions, and thus this quantity is essential for studies of aerosol radiative forcing.
Measurements of Atmospheric Aerosols by the VIIRS Instrument for NPOESS
The National Polar-orbiting Operational Environmental Satellite System [NPOESS] is being developed to replace the current NOAA Polar Orbiting Environmental Satellite (POES) and the DoD Defense Meteorological Satellite Program (DMSP) systems. The instruments will represent significant improvements over the current operational sensors. For example the Visible-IR Imager Radiometer Suite [VIIRS] with 22 channels will be replacing the 6-channel Advanced Very High Resolution [AVHRR] on the POES system and the 2-channel Operational Line Scanner [OLS] on the DMSP system. Measurements of the atmospheric aerosols from NPOESS, will come from the VIIRS instrument. VIIRS has 22 spectral bands including 16 radiometric bands plus 5 imaging bands and a day-night band. The aerosol related Environmental Data Records (EDRs) will be derived primarily from the radiometric channels covering the visible through the short-wave infrared spectral regions (412 to 2250 nm). The primary aerosol products will be the aerosol optical thickness, the aerosol particle size parameter, and the identification of suspended matter. These aerosol products and their derivation will be described. Performance estimates for aerosol optical thickness and aerosol particle size parameter based on comparison with AERONET match-up data will be presented.
1989-01-01
The spectra of stabilized solvent holes were obtained by the method of optically detected ESR (OD ESR) in glassy matrices at 77 K. Using this technique we obtained the spectra for radical-cations of cis-decalin, squalane, 2-methylpentane, 3-methylpentane, 3,3-dimethylpentane, 3-methylheptane and 2,3-dimethylbutane. For all matrices except that of squalane, an hf-structure in the OD ESR spectra belonging to the radical-cations of matrices used is detected. Thus an unpaired electron is shown to be localized mainly on one molecule. The efficiency of hole transfer to acceptors with a lower ionization potential is studied in squalane and cis-decalin. It increases with difference in ionization DELTAI
Appraising the Direct Impacts of Aerosol on Climate (ADIENT)
2010-04-30
ObjectivesThis project forms a consortium of leading UK experts in aerosol modelling and measurement with the overarching objective of quantifying the direct effect of aerosols on the Earth's radiation budget, via scattering and/or absorption of radiation. The objectives of the projects are to deliver: + new FAAM measurements of the physical, chemical and optical properties of aerosol over the UK and Europe, + a comprehensive description of the spatio-temporal evolution of anthropogenic aerosol, in [continued...]DescriptionAn aerosol particle is so small that you could line up one hundred in the width of a human hair. It can float in the air almost undetected. Aerosols play an important role in climate. Aerosols present in the atmosphere tend to reflect sunlight back into space, causing cooling of the Earth's atmosphere. Yet some aerosols, for example from fires and old diesel cars, are made from carbon and actually absorb the Sun's light. This warms the atmosphere. Aerosols also have an indirect effect on the cli [continued...]
Appraising the Direct Impacts of Aerosol on Climate (ADIENT)
2010-07-31
ObjectivesThis project forms a consortium of leading UK experts in aerosol modelling and measurement with the overarching objective of quantifying the direct effect of aerosols on the Earth's radiation budget, via scattering and/or absorption of radiation. The objectives of the projects are to deliver: + new FAAM measurements of the physical, chemical and optical properties of aerosol over the UK and Europe, + a comprehensive description of the spatio-temporal evolution of anthropogenic aerosol, in part [continued...]DescriptionAn aerosol particle is so small that you could line up one hundred in the width of a human hair. It can float in the air almost undetected. Aerosols play an important role in climate. Aerosols present in the atmosphere tend to reflect sunlight back into space, causing cooling of the Earth's atmosphere. Yet some aerosols, for example from fires and old diesel cars, are made from carbon and actually absorb the Sun's light. This warms the atmosphere. Aerosols also have an indirect effect on the cli [continued...]
Appraising the Direct Impacts of Aerosol on Climate (ADIENT)
2010-07-08
ObjectivesThis project forms a consortium of leading UK experts in aerosol modelling and measurement with the overarching objective of quantifying the direct effect of aerosols on the Earth's radiation budget, via scattering and/or absorption of radiation. The objectives of the projects are to deliver: + new FAAM measurements of the physical, chemical and optical properties of aerosol over the UK and Europe, + a comprehensive description of the spatio-temporal evolution of anthropogenic aerosol, in [continued...]DescriptionAn aerosol particle is so small that you could line up one hundred in the width of a human hair. It can float in the air almost undetected. Aerosols play an important role in climate. Aerosols present in the atmosphere tend to reflect sunlight back into space, causing cooling of the Earth's atmosphere. Yet some aerosols, for example from fires and old diesel cars, are made from carbon and actually absorb the Sun's light. This warms the atmosphere. Aerosols also have an indirect effect on the cli [continued...]
The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms.
The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms.
2005-03-18
The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms.
1976-12-01
Samples of selected laser-protection eyewear were tested for a 3-month period in the colorfastness part of the USAFSAM Laser-Protection Eyewear Evaluation Program. Results included some moderate to severe changes in optical density (OD), measured by a laser OD system, as well as changes in haze and refraction. Some protection devices underwent severe structural changes as a result of testing. A follow-on study to determine an appropriate revised cutoff for colorfastness testing is briefly described.
Colours of the Sun and Moon: the role of the optical air mass
2006-03-01
A geometric model for the optical air mass of the atmosphere is developed. Using the model, simple formulae are derived for the optical thickness of light passing through (1) a molecular atmosphere (2) an atmosphere with uniformly distributed tropospheric aerosols and (3) atmospheres with elevated aerosol layers. The formulae are used to model the spectra and perceived colours of the Sun and Moon.
Aerosol optical depth estimates based on nephelometer measurements at the SGP arm site
1996-03-01
The scattering of shortwave radiation by anthropogenic aerosols during clear-sky conditions, termed direct aerosol forcing, has been estimated to be roughly 1 W/m{sup 2} on a global annual average and may be as high as 50 W/m{sup 2} locally and instantaneously new source regions. The extent of the direct aerosol forcing effect at a given time and place depends primarily in the aerosol optical depth, {tau}, as well as on other factors including the solar zenith angle, aerosol upscatter fraction, and the single scatter albedo (ratio of light scattering to total extinction). The aerosol optical depth at a given wavelength ({tau}{sub {lambda}}) can be written as the integral with height to the top of the atmosphere (toa) of the aerosol extinction coefficient, b{sub ext,p}. Where b{sub ext,p} is the sum of the aerosol extinction (b{sub ap}) and scattering (b{sub sp}) coefficients. The objectives of this research are to use nephelometer measurements of the scattering coefficient to estimate the aerosol optical depth at a specific wavelength (530 nm), and to compare these results with optical depths measured by a Multi-Filter Rotating Shadowband Radiometer (MFRSR) and Cimel Sun Photometer. This comparison will used to determine if all of the key parameters related to aerosol optical depth are being measured at the SGP ARM site.
1982-09-01
The composition of tubing used to transport aerosols for extractive sampling or analysis can have a significant effect on the measured particle diameter and concentration. In an effort to quantify this effect and study possible methods of mitigation, four separate types of 1/4-inch O.D. tubing commonly used for aerosol transport were studied (i.e., stainless steel, tygon, polyflow, and natural rubber). The subject aerosol consisted of NaCl particles with a mean concentration of about 10/sup 6/ particles/cm/sup 3/ and a geometric mean particle diameter of about 0.02 microns with a standard deviation of 1.4. The size and the concentration of the transported aerosols were measured with an Electrical Aerosol Analyzer (EAA - TSI Model 3030) and a Condensation Nucleus Counter (CNC - TSI Model 3020), respectively. No effects of tubing type were apparent when the aerosols were passed through a radioactive charge neutralizer after transport through the test tubing. Stainless steel tubing gave the highest measured aerosol concentration in the absence of the charge neutralizer. During an initial conditioning interval, the measured aerosol concentration increased with time for all tubing types except stainless steel. As a result, presampling intervals of at least 30 minutes are recommended for conditioning of transport tubing to provide more consistent data. 5 figures, 5 tables.
Numerical study of overpopulation density for laser oscillation in recombining hydrogen plasmas
1983-06-01
The dependence of overpopulation density (OD) on ground-level population density (n1) and electron temperature (Te) in a recombining hydrogen plasma is evaluated for line pairs with the principal quantum numbers (2,3), (3,4), and (4,5). The approach is based on the simultaneouss solution of the quasi-steady-state rate equation (including interatomic-collision terms) and the optical-escape-factor equation for the Lyman series with Doppler profile. Calculations are performed for optically thin and thick plasmas at a fixed atomic temperature of 0.15 eV, over a Te range from 0.1 to 1 eV and an electron-density (ne) range from 10 to the 11th to 10 to the 17th per cu cm. It is shown that peak OD occurs at an ne slightly below that at which population inversion is destroyed, that peak OD is inversely sensitive to Te, and that peak OD(2,3) is the highest of the three peak OD. Laser oscillation is determined to be possible for (2,3) at Te higher than for (3,4) and (4,5), if self-absorption is negligible. The OD remains constant as n1 increases, up to the point at which significant self-absorption occurs. No laser oscillation is expected at level (4,5), nor in optically thick plasma at any level, for the realistic cavity parameters and temperatures used in the calculations. 21 references.
Simultaneous retrieval of aerosol and surface optical properties ...
is determined by solving a linear system of equations rather .... )Cf . The Lagrange mul- tiplier characterizes the contribution of the a priori term ..... gular resolution defined by an instantaneous field of view of ...
Characterization of the optical properties of biomass burning ...
In general, S was relatively constant as a function of aerosol loading, .... Embedded within this study are objectives to quantify the consumption of biomass ...... spectral reflectance for 10% green vegetation cover of Deering ...
In situ measurements of aerosol optical and hygroscopic properties were made on board the National Oceanic and Atmospheric Administration R/V Ronald H. Brown during the Texas Air Quality Study-Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS-GoMACCS). The aerosol light extinction coefficient (? ep) was measured at 355, 532, and 1064 nm at 25%, 60%, and 85% relative humidity (RH) for both sub-1- and sub-10-?m-diameter particles with a cavity ring-down aerosol extinction spectrometer. The 532-nm ? ep was coupled with the 532-nm light absorption coefficient (? ap) measured with a photoacoustic absorption spectrometer to calculate the aerosol single scattering albedo (?) with absolute uncertainty <0.01. The ? ep dependence on RH was expressed in terms of gamma (?). The sampled aerosols covered a broad spectrum of ? and ? values; aerosols from traffic emissions were hydrophobic and highly light-absorbing with ? ? 0.4 and ? ? 0.6, whereas the regional aerosols exhibited variable values of both ? and ?. Aerosols with the highest sulfate content also had the highest ? and ? values (>0.65 and >0.9, respectively). The optical data were used to estimate local, top of atmosphere aerosol-induced climate forcing (?F R ). The ?F R calculations were performed using both ? values measured at 25% RH and ? values converted to ambient RH. The calculated ambient ?F R ranged from ?7 to ?40 W/m2 with absolute uncertainty between 0.7 and 2.5 W/m2. The results show that including aerosol hygroscopic properties in climate calculations is critical for improving estimates of aerosol forcing on climate.
The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct, the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical thickness ...
The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct, the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical thickness ...
Laboratory studies of the dynamics of aerosol droplets.
2004-07-31
DescriptionThe dynamics of liquid aerosol droplets will be probed by non-intrusive optical laser methods that can be used to determine directly the composition and size of single aerosol particles. The condensation and evaporation dynamics of liquid droplets will be probed by cavity enhanced Raman scattering under controlled laboratory conditions, with a particular focus on examining multicomponent condensation rates and the influence of fundamental chemical factors on the size dynamics of droplets. To com [continued...]
Laboratory studies of the dynamics of aerosol droplets.
2006-02-05
Objectives'DescriptionThe dynamics of liquid aerosol droplets will be probed by non-intrusive optical laser methods that can be used to determine directly the composition and size of single aerosol particles. The condensation and evaporation dynamics of liquid droplets will be probed by cavity enhanced Raman scattering under controlled laboratory conditions, with a particular focus on examining multicomponent condensation rates and the influence of fundamental chemical factors on the size dynamics of droplets. To com [continued...]
1999-11-23
The effect of atmospheric aerosols and regional haze from air pollution on the yields of rice and winter wheat grown in China is assessed. The assessment is based on estimates of aerosol optical depths...Full Text Available
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