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Investigation of the Impact of Aerosols on Clouds During May 2003 Intensive Operational Period at the Southern Great Plains

Description: The effect of aerosols on the clouds, or the so-called aerosol indirect effect (AIE), is highly uncertain (Penner et al. 2001). The estimation of the AIE can vary from 0.0 to -4.8 W/m2 in Global Climate Models (GCM). Therefore, it is very important to investigate these interactions and cloud-related physical processes further. The Aerosol Intensive Operation Period (AIOP) at the Southern Great Plains (SGP) site in May 2003 dedicated some effort towards the measurement of the Cloud Condensation Nucleus concentration (CCN) as a function of super-saturation and in relating CCN concentration to aerosol composition and size distribution. Furthermore, airborn measurement for the cloud droplet concentration was also available. Therefore this AIOP provides a good opportunity to examine the AIE. In this study, we use a Cloud Resolving Model (CRM), i.e., Active Tracer High-resolution Atmospheric Model (ATHAM), to discuss the effect of aerosol loadings on cloud droplet effective radius (Re) and concentration. The case we examine is a stratiform cloud that occurred on May 17, 2003.
Date: March 18, 2005
Creator: Guo, H.; Penner, J.E. & Herzog, M.
Partner: UNT Libraries Government Documents Department

Short-term Variability of Extinction by Broadband Stellar Photometry

Description: Aerosol optical depth variation over short-term time intervals is determined from broadband observations of stars with a whole sky imager. The main difficulty in such measurements consists of accurately separating the star flux value from the non-stellar diffuse skylight. Using correction method to overcome this difficulty, the monochromatic extinction at the ground due to aerosols is extracted from heterochromatic measurements. A form of closure is achieved by comparison with simultaneous or temporally close measurements with other instruments, and the total error of the method, as a combination of random error of measurements and systematic error of calibration and model, is assessed as being between 2.6 and 3% rms.
Date: March 18, 2005
Creator: Musat, I.C. & Ellingson, R.G.
Partner: UNT Libraries Government Documents Department

Representing Cloud Processing of Aerosol in Numerical Models

Description: The satellite imagery in Figure 1 provides dramatic examples of how aerosol influences the cloud field. Aerosol from ship exhaust can serve as nucleation centers in otherwise cloud-free regions, forming ship tracks (top image), or can enhance the reflectance/albedo in already cloudy regions. This image is a demonstration of the first indirect effect, in which changes in aerosol modulate cloud droplet radius and concentration, which influences albedo. It is thought that, through the effects it has on precipitation (drizzle), aerosol can also affect the structure and persistence of planetary boundary layer (PBL) clouds. Regions of cellular convection, or open pockets of cloudiness (bottom image) are thought to be remnants of strongly drizzling PBL clouds. Pockets of Open Cloudiness (POCs) (Stevens et al. 2005) or Albrecht's ''rifts'' are low cloud fraction regions characterized by anomalously low aerosol concentrations, implying they result from precipitation. These features may in fact be a demonstration of the second indirect effect. To accurately represent these clouds in numerical models, we have to treat the coupled cloud-aerosol system. We present the following series of mesoscale and large eddy simulation (LES) experiments to evaluate the important aspects of treating the coupled cloud-aerosol problem. 1. Drizzling and nondrizzling simulations demonstrate the effect of drizzle on a mesoscale forecast off the California coast. 2. LES experiments with explicit (bin) microphysics gauge the relative importance of the shape of the aerosol spectrum on the 3D dynamics and cloud structure. 3. Idealized mesoscale model simulations evaluate the relative roles of various processes, sources, and sinks.
Date: March 18, 2005
Creator: Mechem, D.B. & Kogan, Y.L.
Partner: UNT Libraries Government Documents Department


Description: The absorption coefficients determined by the integrating plate method and the laser transmission method are found to be comparable and highly correlated. Furthermore, a high correlation is found between these absorption coefficients and the carbon content of the aerosol in urbanized regions.
Date: July 1, 1980
Creator: Sadler, M.; Charlson, R.J.; Rosen, H. & Novakov, T.
Partner: UNT Libraries Government Documents Department

Data Quality Assessment and Control for the ARM Climate Research Facility

Description: The mission of the Atmospheric Radiation Measurement (ARM) Climate Research Facility is to provide observations of the earth climate system to the climate research community for the purpose of improving the understanding and representation, in climate and earth system models, of clouds and aerosols as well as their coupling with the Earth's surface. In order for ARM measurements to be useful toward this goal, it is important that the measurements are of a known and reasonable quality. The ARM data quality program includes several components designed to identify quality issues in near-real-time, track problems to solutions, assess more subtle long-term issues, and communicate problems to the user community.
Date: June 26, 2012
Creator: Peppler, R.
Partner: UNT Libraries Government Documents Department

Response of California temperature to regional anthropogenic aerosol changes

Description: In this paper, we compare constructed records of concentrations of black carbon (BC)--an indicator of anthropogenic aerosols--with observed surface temperature trends in California. Annual average BC concentrations in major air basins in California significantly decreased after about 1990, coincident with an observed statewide surface temperature increase. Seasonal aerosol concentration trends are consistent with observed seasonal temperature trends. These data suggest that the reduction in anthropogenic aerosol concentrations contributed to the observed surface temperature increase. Conversely, high aerosol concentrations may lower surface temperature and partially offset the temperature increase of greenhouse gases.
Date: May 12, 2008
Creator: Kirchstetter, Thomas; Novakov, T.; Kirchstetter, T.W.; Menon, S. & Aguiar, J.
Partner: UNT Libraries Government Documents Department

Applying EMSL Capabilities to Biogeochemistry and Environmental Research

Description: The Environmental Molecular Sciences laboratory (EMSL) is a national scientific user facility operated by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy's Office of Biological and Environmental Research. Located in Richland, Washington, EMSL offers researchers a comprehensive array of cutting-edge capabilities unmatched anywhere else in the world and access to the expertise of over 300 resident users--all at one location. EMSL's resources are available on a peer-reviewed proposal basis and are offered at no cost if research results are shared in the open literature. Researchers are encouraged to submit a proposal centered around one of EMSL's four Science Themes, which represent growing areas of research: (1) Geochemistry/Biogeochemistry and Subsurface Science; (2) Atmospheric Aerosol Chemistry; (3) Biological Interactions and Dynamics; and (4) Science of Interfacial Phenomena. To learn more about EMSL, visit www.emsl.pnl.gov.
Date: April 19, 2007
Creator: Felmy, Andy
Partner: UNT Libraries Government Documents Department

Aerosol penetration of leak pathways : an examination of the available data and models.

Description: Data and models of aerosol particle deposition in leak pathways are described. Pathways considered include capillaries, orifices, slots and cracks in concrete. The Morewitz-Vaughan criterion for aerosol plugging of leak pathways is shown to be applicable only to a limited range of particle settling velocities and Stokes numbers. More useful are sampling efficiency criteria defined by Davies and by Liu and Agarwal. Deposition of particles can be limited by bounce from surfaces defining leak pathways and by resuspension of particles deposited on these surfaces. A model of the probability of particle bounce is described. Resuspension of deposited particles can be triggered by changes in flow conditions, particle impact on deposits and by shock or vibration of the surfaces. This examination was performed as part of the review of the AP1000 Standard Combined License Technical Report, APP-GW-GLN-12, Revision 0, 'Offsite and Control Room Dose Changes' (TR-112) in support of the USNRC AP1000 Standard Combined License Pre-Application Review.
Date: April 1, 2009
Creator: Powers, Dana Auburn
Partner: UNT Libraries Government Documents Department


Description: Experimental results are reviewed which demonstrate that combustion-generated soot particles can oxidize SO{sub 2} in both the absence ('dry' mechanism) and the presence ('wet' mechanism) of liquid water. The 'wet' mechanism is much more efficient than the 'dry' one, and is applicable to situations where the aerosol particles are covered with a liquid water layer. Calculations are presented which suggest that the soot-catalyzed oxidation of SO{sub 2} can be the dominant mechanism under realistic atmospheric conditions.
Date: May 1, 1978
Creator: Chang, S.G. & Novakov, T.
Partner: UNT Libraries Government Documents Department

A study of cloud and drizzle properties in the Azores using Doppler Radar spectra

Description: Understanding the onset of coalescence in warm clouds is key in our effort to improve cloud representation in numerical models. Coalescence acts at small scales, and its study requires detailed high-resolution dynamical and microphysical measurements from a comprehensive suite of instruments over a wide range of environmental conditions (e.g., aerosol loading). The first AMF is currently in its second year of a two-year deployment at Graciosa Island in the Azores, offering the opportunity to collect a long data set from a stable land-based platform in a marine stratocumulus regime. In this study, recorded WACR Doppler spectra are used to characterize the properties of Doppler spectra from warm clouds with and without drizzle, and from drizzle only, in an effort to observe the transition (onset) to precipitation in clouds. A retrieval technique that decomposes observed Doppler spectra into their cloud and/or drizzle components is applied in order to quantify drizzle growth.
Date: March 15, 2010
Creator: Luke, E.; Remillard, J. & Kollias, P.
Partner: UNT Libraries Government Documents Department

The First Aerosol Indirect Effect: Beyond Twomey

Description: The traditional first aerosol indirect effect or the Twomey effect involves several fundamental assumptions. Some of the assumptions (e.g., constant liquid water content) are explicitly stated in studies of the Twomey effect whereas others are only implicitly embedded in the quantitative formulation. This work focuses on examining the implicit assumptions. In particular, we will show that anthropogenic pollution not only increases aerosol loading and droplet concentrations but also alters the relative dispersions of both the aerosol and subsequent droplet size distributions. The indirect effects resulting from the two altered relative dispersions (aerosol dispersion effect and droplet dispersion effect) are likely opposite in sign and proportional in magnitude to the conventional Twomey effect. This result suggests that the outstanding problems of the Twomey effect (i.e., large uncertainty and overestimation reported in literature) may lie with violation of the constant spectral shapes of aerosol and droplet size distributions implicitly assumed in evaluation of the Twomey effect, and therefore, further progress in understanding and quantification of the first aerosol indirect effect demands moving beyond the traditional paradigm originally conceived by Twomey.
Date: March 10, 2008
Creator: Liu, Y.; Dunn, M. & Daum, P.
Partner: UNT Libraries Government Documents Department


Description: The operating performance of air-cleaning facilities at AEC installations is reviewed, and fundamental information obtained from basic studies of aerosol behavior is presented. Separate abstracts have been prepared for each paper. (W.L.H.)
Date: November 1, 1954
Partner: UNT Libraries Government Documents Department

Lead Exposures and Biological Responses in Military Weapons Systems: Aerosol Characteristics and Acute Lead Effects among US Army Artillerymen: Final Report

Description: This study was to determine the concentration and chemical nature of lead (Pb) aerosols produced during the firing of artillery and to determine the exposures and biological responses of crew members exposed to lead aerosols during such firing. The concentrations of lead-containing aerosols at crew positions depended on wind conditions, with higher concentrations when firing into a head wind. Aerosol concentrations were highest in the muzzle blast zone. Concentrations of lead in the blood of crew members rose during the first 12 days of exposure to elevated airborne lead concentrations and then leveled off. There was no rapid decrease in blood lead concentrations after completion of firing. Small decreases in hematocrit and small increases in free erythrocyte porphyrin were correlated with increasing exposure to airborne lead. These changes were reversed by seven weeks after firing. Changes in nerve conduction velocity had borderline statistical significance to airborne lead exposure. In measuring nerve conduction velocity, differences in skin temperature must be taken into account.
Date: March 1993
Creator: Bhattacharyya, M. H.
Partner: UNT Libraries Government Documents Department

Modeling the wind-fields of accidental releases with an operational regional forecast model

Description: The Atmospheric Release Advisory Capability (ARAC) is an operational emergency preparedness and response organization supported primarily by the Departments of Energy and Defense. ARAC can provide real-time assessments of atmospheric releases of radioactive materials at any location in the world. ARAC uses robust three-dimensional atmospheric transport and dispersion models, extensive geophysical and dose-factor databases, meteorological data-acquisition systems, and an experienced staff. Although it was originally conceived and developed as an emergency response and assessment service for nuclear accidents, the ARAC system has been adapted to also simulate non-radiological hazardous releases. For example, in 1991 ARAC responded to three major events: the oil fires in Kuwait, the eruption of Mt. Pinatubo in the Philippines, and the herbicide spill into the upper Sacramento River in California. ARAC`s operational simulation system, includes two three-dimensional finite-difference models: a diagnostic wind-field scheme, and a Lagrangian particle-in-cell transport and dispersion scheme. The meteorological component of ARAC`s real-time response system employs models using real-time data from all available stations near the accident site to generate a wind-field for input to the transport and dispersion model. Here we report on simulation studies of past and potential release sites to show that even in the absence of local meteorological observational data, readily available gridded analysis and forecast data and a prognostic model, the Navy Operational Regional Atmospheric Prediction System, applied at an appropriate grid resolution can successfully simulate complex local flows.
Date: September 11, 1995
Creator: Albritton, J.R.; Lee, R.L. & Sugiyama, G.
Partner: UNT Libraries Government Documents Department

Emergency Protection from Aerosols

Description: Expedient methods were developed that could be used by an average person, using only materials readily available, to protect himself and his family from injury by toxic (e.g., radioactive) aerosols. The most effective means of protection was the use of a household vacuum cleaner to maintain a small positive pressure on a closed house during passage of the aerosol cloud. Protection factors of 800 and above were achieved.
Date: November 13, 2001
Creator: Cristy, G.A.
Partner: UNT Libraries Government Documents Department

Scanning Transmission X-ray Microscopy: Applications in Atmospheric Aerosol Research

Description: Scanning transmission x-ray microscopy (STXM) combines x-ray microscopy and near edge x-ray absorption fine structure spectroscopy (NEXAFS). This combination provides spatially resolved bonding and oxidation state information. While there are reviews relevant to STXM/NEXAFS applications in other environmental fields (and magnetic materials) this chapter focuses on atmospheric aerosols. It provides an introduction to this technique in a manner approachable to non-experts. It begins with relevant background information on synchrotron radiation sources and a description of NEXAFS spectroscopy. The bulk of the chapter provides a survey of STXM/NEXAFS aerosol studies and is organized according to the type of aerosol investigated. The purpose is to illustrate the current range and recent growth of scientific investigations employing STXM-NEXAFS to probe atmospheric aerosol morphology, surface coatings, mixing states, and atmospheric processing.
Date: January 20, 2011
Creator: Moffet, Ryan C.; Tivanski, Alexei V. & Gilles, Mary K.
Partner: UNT Libraries Government Documents Department

Real time in situ detection of organic nitrates in atmospheric aerosols

Description: A new field instrument is described that quantifies total particle phase organic nitrates. The instrument is based on the thermal dissociation laser induced fluorescence (TD-LIF) method that thermally converts nitrates to NO2 which is then detected by LIF. This instrument is unique in its ability to provide fast sensitive measurements of particle phase organic nitrates, without interference from inorganic nitrate. Here we use it to quantify organic nitrates in SOA generated from high-NOx photooxidation of limonene, a-pinene, D-3-carene, and tridecane. In these experiments the organic nitrate moiety is observed to be 6-15percent of the total SOA mass, depending on the organic precursor.
Date: June 11, 2010
Creator: Rollins, Andrew W.; Smith, Jared D.; Wilson, Kevin R. & Cohen, Ronald C.
Partner: UNT Libraries Government Documents Department