The author demonstrates that, over a rather wide range of important conditions, total mass deposition rates from polydispersed aerosols resulting from coagulation, can be readily calculated from the corresponding depo...
详细信息
The author demonstrates that, over a rather wide range of important conditions, total mass deposition rates from polydispersed aerosols resulting from coagulation, can be readily calculated from the corresponding deposition rate from a hypothetical 'monodispersed' aerosol in which all particles have the prevailing average size (volume) v¯(=φp/Np). The author illustrates his approach for the frequently encountered case of high-Peclet-number convective diffusion across nearly isothermal boundary layers, obtaining results that are remarkably insensitive to fluid dynamic conditions [laminar or turbulent boundary layer (BL)], particle Knudsen number (free-molecule or continuum Brownian diffusion) or particle morphology (dense spherical particles or low-density agglomerates).
January is the month of the northeasterly monsoon over the Indian peninsula. Continental and anthropogenic aerosols are advected from the land to the ocean and mix with the marine atmosphere. This is an ideal time to ...
详细信息
January is the month of the northeasterly monsoon over the Indian peninsula. Continental and anthropogenic aerosols are advected from the land to the ocean and mix with the marine atmosphere. This is an ideal time to study the dispersal of continental aerosols into the marine atmosphere. This communication presents the results of the sun-photometer-measured aerosol optical depth (AOD) onboard Sagar Kanya over the northern Arabian Sea on its 186th mission, from 3 to 20 January 2003. The temporal, spectral and spatial variations of AOD are investigated. Relationship between AOD and relative humidity and variations in AOD and the Angstrom exponent from coastal to far-coastal regions of the ocean with respect to the prevailing wind conditions has been presented.
The chemical composition of aerosol particles is much less important than their size in determining their ability to nucleate clouds, a result that will clarify aerosol effects on climate.
The chemical composition of aerosol particles is much less important than their size in determining their ability to nucleate clouds, a result that will clarify aerosol effects on climate.
A new cryogenic instrument was designed for the trapping of aerosols such as cigarette mainstream smoke at low temperature. The technique enabled the trapping of the mainstream smoke of a single cigarette and the part...
详细信息
A new cryogenic instrument was designed for the trapping of aerosols such as cigarette mainstream smoke at low temperature. The technique enabled the trapping of the mainstream smoke of a single cigarette and the particulate and vapor phases were trapped simultaneously. 2R4F reference cigarettes were smoked under International Standard Organization (ISO) regime and trapped at low temperature using the cryogenic instrument. After trapping, the mainstream smoke of the 2R4F reference cigarette was diluted with a solvent and selected smoke components could be quantified using gas-mass spectrometry (GCMS) and high-performance liquid chromatography (HPLC). The capability of the instrument for trapping the mainstream smoke was demonstrated. The feasibility of the procedure for the detection and the quantification of a large range of smoke components including carbonyls, alkaloids and organic volatile compounds (VOC) in the mainstream of a single cigarette was also shown. (c) 2006 Elsevier Ltd. All rights reserved.
Aerosol droplets in monodisperse sprays produced by spinning disc generators are shown to correlate with a simple law when the controlling parameters are represented in an appropriate dimensionless form. This correlat...
详细信息
Aerosol droplets in monodisperse sprays produced by spinning disc generators are shown to correlate with a simple law when the controlling parameters are represented in an appropriate dimensionless form. This correlation holds for liquid of widely differing physical properties, viz. with surface tensions varying between 31.5 and 465 dyne/cm. The results implies that the Bond number based on the droplet size (i.e., the ratio of the body force to the surface tension) has a constant value of approximately 1.63. (C) 1997 American Association for Aerosol Research.
Most of the so-called 'CO2 effect' is, in fact, an 'H2O effect' brought into play by the climate modeler's assumption that planetary average temperature dictates water-vapor concentration (followin...
详细信息
Most of the so-called 'CO2 effect' is, in fact, an 'H2O effect' brought into play by the climate modeler's assumption that planetary average temperature dictates water-vapor concentration (following Clapeyron-Clausius). That assumption ignores the removal process, which cloud physicists know to be influenced by the aerosol, since the latter primarily controls cloud droplet number and size. Droplet number and size are also influential for shortwave (solar) energy. The reflectance of many thin to moderately thick clouds changes when nuclei concentrations change and make shortwave albedo susceptible to aerosol influence.
Inhaled therapy is routinely employed during mechanical ventilation. Several factors affect aerosol delivery: the aerosol device, particle size, ventilator parameters, ventilator circuit and hygrometry. Non invasive v...
详细信息
Inhaled therapy is routinely employed during mechanical ventilation. Several factors affect aerosol delivery: the aerosol device, particle size, ventilator parameters, ventilator circuit and hygrometry. Non invasive ventilation is commonly used for treatment of exacerbations of chronic obstructive pulmonary disease. However, there are few data concerning the factors affecting aerosol delivery during this mode of ventilation. Optimal aerosol delivery during mechanical ventilation depends on the aerosol device, the respirator circuit and settings, and the patient himself.
Anthropogenic aerosols are hypothesized to enhance planetary albedo and offset some of the warming due to the buildup of greenhouse gases in Earth's atmosphere. aerosols can enhance the coverage, reflectance, and ...
详细信息
Anthropogenic aerosols are hypothesized to enhance planetary albedo and offset some of the warming due to the buildup of greenhouse gases in Earth's atmosphere. aerosols can enhance the coverage, reflectance, and lifetime of warm low-level clouds. However, the relationship between cloud lifetime and aerosol concentration has been challenging to measure from polar orbit-ing satellites. We estimate two timescales relating to the for-mation and persistence of low-level clouds over 1 degrees x 1 degrees spatial domains using multiple years of geostationary satellite observa-tions provided by the Clouds and Earth's Radiant Energy System (CERES) Synoptic (SYN) product. Lagrangian trajectories span-ning several days along the classic stratus-to-cumulus transition zone are stratified by aerosol optical depth and meteorology. Clouds forming in relatively polluted trajectories tend to have lighter precipitation rates, longer average lifetime, and higher cloud albedo and cloud fraction compared with unpolluted tra-jectories. While liquid water path differences are found to be negligible, we find direct evidence of increased planetary albedo primarily through increased drop concentration (Nd) and cloud fraction, with the caveat that the aerosol influence on cloud fraction is positive only for stable atmospheric conditions. While the increase in cloud fraction can be large typically in the beginning of trajectories, the Twomey effect accounts for the bulk (roughly 3/4) of the total aerosol indirect radiative forcing estimate.
Between 15 January and 26 February 1987, 51 fine and coarse mode aerosol samples were collected at the Universidad de Santiago de Chile Planetarium using a dichotomous sampler. The samples were analyzed by X-ray fluor...
详细信息
Between 15 January and 26 February 1987, 51 fine and coarse mode aerosol samples were collected at the Universidad de Santiago de Chile Planetarium using a dichotomous sampler. The samples were analyzed by X-ray fluorescence for up to 17 elements (Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb). Aerosol particles were individual studied by Electron Probe Microanalysis (EPMA) and Laser Microprobe Mass Analysis (LAMMA). The data set consisting of aerosol element concentrations and meterological variables was subjected to Principal Factor Analysis (PFA), allowing the identification of six fine mode particle source classes (soil, industrial, sulfate particles, traffic, residual oil, wood-burnings), and five coarse mode particle source classes (soil, industrial, traffic, residual oil, sulfate particles). Both PFA solutions explained about 81 and 90% of the total variance in the data set, respectively. The regression of element mass concentrations on the Absolute Principal Factor Scores allowed the estimation of the contribution of the different source clases to the Santiago aerosol. Within the fine fraction, secondary SO42- particles were responsible for about 49% of the fine mode aerosol mass concentration, while 26, 13, 6.4 and 5.6% were attributed to wood-burning/car exhausts, residual oil combustion, soil dust/metallurgical, and soil dust/wood-burning releases, respectively. The coarse fraction source apportionment was mainly dominated by soil duct, accounting for 74% of the coarse mode aerosol mass concentration. A composite of soil dust and industrial release accounted for 13%;a composite of secondary sulfates contributed with 9%;a composite of soil dust and automotive emissions, and secondary sulfate were responsible for 4 and 0.03% of the coarse aerosol mass concentration, respectively. EPMA results are in satisfactory agreement with those from the bulk analysis and allowed the identification of eight particle types in both fine and coarse mode
Chamber experiments were conducted to study the aerosol products from the ozonolysis of the major atmospheric monoterpenes;α-pinene, β-pinene and limonene. It was found that the α-pinend-O3 reaction produced mainl...
详细信息
暂无评论