Download or read book Investigation of the Impact of Aerosols on Clouds During May 2003 Intensive Operational Period at the Southern Great Plains written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atmospheric Aerosol Properties and Climate Impacts written by Mian Chin and published by DIANE Publishing. This book was released on 2009-05 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Synthesis and Assessment Product (SAP) critically reviews current knowledge about global distributions and properties of atmospheric aerosols, as they relate to aerosol impacts on climate. It assesses possible next steps aimed at substantially reducing uncertainties in aerosol radiative forcing estimates. Current measurement techniques and modeling approaches are summarized, providing context. The objectives of this report are: (1) to promote a consensus about the knowledge base for climate change decision support; and (2) to provide a synthesis and integration of the current knowledge of the climate-relevant impacts of anthropogenic aerosols. Illustrations.

Download or read book Final Technical Report for Grant DE FG02 06ER64169 written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Atmospheric Radiation Measurement (ARM) program is funding this project to improve the methodology of ground-based remote sensing of the vertical distribution of aerosol and cloud optical properties, and their effect on atmospheric radiative transfer. Remotely-sensed and in situ observed aerosol, cloud physical, and optical properties collected during the May 2003 Aerosol Intensive Operational Period (AIOP) and the Aerosol Lidar Validation Experiment (ALIVE), conducted from September 11-22, 2005, are the basis for the investigation. We have used ground-based lidar, airborne sunphotometer and in situ measurements and other data to evaluate the vertical profile of aerosol properties. We have been pursuing research in the following three areas: (1) Aerosol Best Estimate Product--Sensitivity Study: ARM is developing an Aerosol Best Estimate (ABE) Value Added Product (VAP) to provide aerosol optical properties at all times and heights above its sites. The ABE is used as input for the Broadband Heating Rate Profile (BBHRP) VAP, whose output will be used to evaluate the radiative treatment of aerosols and clouds in climate models. ARM has a need to assess how much detail is required for the ABE and if a useful ABE can be derived for the tropical and arctic climate research facilities (CRFs) where only limited aerosol information in the vertical is available. We have been determining the sensitivity of BBHRP to the vertical profile of aerosol optical properties used in ABE. (2) Vertically Resolved Aerosol and Cloud Radiative Properties over the Southern Great Plains (SGP): The AIOP delivered an unprecedented airborne radiometric and in situ data set related to aerosols and clouds. The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS's) Twin Otter aircraft carried solar pointing, up- and down-looking radiometers (spectral and broadband, visible, and infrared) with the uplooking radiometers mounted on a stabilized platform. We are performing an integrated analysis of the largely unexploited radiometric data set to provide observation-based quantification of the effect of aerosols and clouds on the radiation field. We will link aerosol and cloud properties measured in situ with the observed radiative fluxes using radiative transfer models. This over-determined dataset will provide validation of the BBHRP VAP. (3) Integrated Analysis of Data from the Aerosol Lidar Validation Experiment: The ABE VAP relies on continuous lidar observations to provide the vertical distribution of the aerosols above the ARM sites. The goal of ALIVE, conducted in September 2005, was the validation of the aerosol extinction profiles obtained from the SGP Raman lidar, which has been recently refurbished/updated, and the Micro Pulse Lidar, for which a new algorithm to retrieve aerosol profiles has recently been developed, using the National Aeronautics and Space Administration (NASA) Ames Airborne Tracking 14 channel Sun photometer. We are performing and publishing the integrated analysis of the ALIVE data set.

Download or read book Atmospheric Aerosol Properties and Climate Impacts written by and published by . This book was released on 2009 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Observations of Hoppel Minima in CCN Spectra in Oklahoma written by Samantha Suzanne Tabor and published by . This book was released on 2015 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols are one of the most fundamental keys to understanding the future state of the climate. Aerosols impact the radiation budget of the Earth in numerous ways and are poorly understood. Some aerosols can act as cloud condensation nuclei (CCN) and can significantly change the properties of clouds; this is known as the Indirect Aerosol Effect (IAE) and it remains the largest climate change uncertainty. Most studies concerning CCN and the impacts of the CCN distributions occur over the ocean, leaving questions about the processing occurring over the continents. Eleven days of measurements from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site were taken from an Aerosol Intensive Operational Period (IOP) during May 2003. A ground based CCN spectrometer and differential mobility analyzer (DMA) were deployed to study the distributions of the CCN spectra and dry aerosol size distributions. 268 measurement periods were sorted by their spectral shapes by using two rating systems. Case studies of the characteristics of the spectra observed during specific times of day or particular meteorological conditions were created and it was shown that meteorological conditions have a significant impact on the shapes of the CCN distributions. Back trajectories were also analyzed and shown to have an even larger impact on the observations of the Hoppel Minima, a minima located between the processed and unprocessed CCN modes. Using vertical velocity and back trajectories along with numerous meteorological measurements it can be shown that cloud processing is not only occurring over the continent but transport of the cloud processed air to the surface is also occurring. The Hoppel Minima during this Oklahoma project had a mean critical supersaturation (Sc) of 0.68%.

Download or read book Examining Aerosol Direct and Indirect Effects Using a Radiative Transfer Model and a Cloud Resolving Model written by Huan Guo and published by . This book was released on 2006 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison Between Lidar and Nephelometer Measurements of Aerosol Hygroscopicity at the Southern Great Plains Atmospheric Radiation Measurement Site written by M. Pahlow and published by BiblioGov. This book was released on 2013-08 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosol hygroscopicity has a significant effect on radiative properties of aerosols. Here a lidar method, applicable to cloud-capped, well-mixed atmospheric boundary layers, is employed to determine the hygroscopic growth factor f(RH) under unperturbed, ambient atmospheric conditions. The data used for the analysis were collected under a wide range of atmospheric aerosol levels during both routine measurement periods and during the intensive operations period (IOP) in May 2003 at the Southern Great Plains (SGP) Climate Research Facility in Oklahoma, USA, as part of the Atmospheric Radiation Measurement (ARM) program. There is a good correlation (approx. 0.7) between a lidar-derived growth factor (measured over the range 85% RH to 96% RH) with a nephelometer-derived growth factor measured over the RH range 40% to 85%. For these RH ranges, the slope of the lidar-derived growth factor is much steeper than that of the nephelometer-derived growth factor, reflecting the rapid increase in particle size with increasing RH. The results are corroborated by aerosol model calculations of lidar and nephelometer equivalent f(RH) based on in situ aerosol size and composition measurements during the IOP. It is suggested that the lidar method can provide useful measurements of the dependence of aerosol optical properties on relative humidity, and under conditions closer to saturation than can currently be achieved with humidified nephelometers.

Download or read book Developing Models of Aerosol Representation to Investigate Composition Evolution Optical Properties and CCN Spectra Using Measurements of Size resolved Hygroscopicity written by Roberto Gasparini and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) was used to measure size distributions, hygroscopicity, and volatility during the May 2003 Aerosol Intensive Operational Period at the Central Facility of the Atmospheric Radiation Measurement Southern Great Plains site. Hygroscopic growth factor distributions for particles at eight dry diameters ranging from 0.012 [mu]m to 0.600 [mu]m were measured. These measurements, along with backtrajectory clustering, were used to infer aerosol composition and evolution. The hygroscopic growth of the smallest and largest particles analyzed was typically less than that of particles with dry diameters of about 0.100 [mu]m. Condensation of secondary organic aerosol on nucleation mode particles may be responsible for the minimal growth observed at the smallest sizes. Growth factor distributions of the largest particles typically contained a non-hygroscopic mode believed to be composed of dust. A model was developed to characterize the hygroscopic properties of particles within a size distribution mode through analysis of the fixed-size hygroscopic growth measurements. This model was used to examine three cases in which the sampled aerosol evolved over a period of hours or days. Additionally, size and hygroscopicity information were combined to model the aerosol as a population of multi-component particles. With this model, the aerosol hygroscopic growth factor f(RH), relating the submicron scattering at high RH to that at low RH, is predicted. The f(RH) values predicted when the hygroscopic fraction of the aerosol is assumed to be metastable agree better with measurements than do those predicted under the assumption of crystalline aerosol. Agreement decreases at RH greater than 65%. This multi-component aerosol model is used to derive cloud condensation nuclei (CCN) spectra for comparison with spectra measured directly with two Desert Research Institute (DRI) CCN spectrometers. Among the 1490 pairs of DMA/TDMA-predicted and DRI-measured CCN concentrations at various critical supersaturations from 0.02-1.05%, the sample number-weighted mean R2 value is 0.74. CCN concentrations are slightly overpredicted at both the lowest (0.02-0.04%) and highest (0.80-1.05%) supersaturations measured. Overall, this multi-component aerosol model based on size distributions and size-resolved hygroscopicity yields reasonable predictions of the humidity-dependent optical properties and CCN spectra of the aerosol.

Download or read book Aerosol Association with Severe Weather in the Great Plains written by Gabriel A. Lojero and published by . This book was released on 2014 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols particles may serve as cloud condensation nuclei (CCN) and therefore play an important role in modulating cloud microphysics, to the point where convective storm intensity may be altered. The purpose of this study is to determine the impacts of biomass burning aerosols on convective storms over the Great Plains, especially the southern Great Plains, and to show synoptic regimes characterizing differing aerosol concentrations. A new technique to identify days with a high concentration of biomass burning aerosols was developed by using organic carbon, potassium, zinc, and bromine as the predominant tracers. An eleven-year climatology (2002-2012) for the biomass burning tracers was produced to identify days on which biomass burning particles were present, and an average concentration of these tracers was obtained from two different sensors in western Oklahoma: Ellis and Wichita Mountains. Once prevalence of biomass burning particles was identified for each day, days were classified into high (upper 30%), medium (middle 40%), and low (lowest 30%) biomass burning particle concentration. Only March through June was considered since this is climatologically the convective season in the Southern Great Plains. Days with severe thunderstorms and with similar thermodynamic (CAPE) and kinematic (shear) environments were chosen as case study days, from which storm report data were obtained and compared. Additionally, composite synoptic regime and a set of trajectories were obtained for each aerosol concentration category. Lastly, differential reflectivity and correlation coefficient values were examined to compare the microphysics of thunderstorms occurring on days of different aerosol concentration. Case studies of High Plains and Oklahoma storms were examined. This study is one of the first observational studies to examine aerosol effects on convective storms in the Great Plains region.

Download or read book Efficacy of Aerosol Cloud Interactions Under Varying Meteorological Conditions written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several studies have demonstrated that cloud dynamical processes such as entrainment mixing may be the primary modulator of cloud optical properties in certain situations. For example, entrainment of dry air alters the cloud drop size distribution by enhancing drop evaporation. However, the effect of entrainment mixing and other forms or turbulence is still quite uncertain. Although these factors and aerosol-cloud interactions should be considered together when evaluating the efficacy of aerosol indirect effects, the underlying mechanisms appear to be dependent upon each other. In addition, accounting for them is impossible with the current understanding of aerosol indirect effect. Therefore, careful objective screening and analysis of observations are needed to determine the extent to which mixing related properties affect cloud optical properties, apart from the aerosol first indirect effect. This study addresses the role of aerosol-cloud interactions in the context of varying meteorological conditions based on ARM data obtained at the Southern Great Plains (SGP) site in Oklahoma and at Pt. Reyes, California. Previous analyses of the continental stratiform clouds at the SGP site have shown that the thicker clouds of high liquid water path (LWP) tend to contain sub adiabatic LWPs. These sub adiabatic LWPs, which result from active mixing processes, correspond to a lower susceptibility of the clouds to aerosol-cloud interactions, and, hence, to reduced aerosol indirect effects. In contrast, the consistently steady and thin maritime stratus clouds observed at Pt. Reyes are much closer to adiabatic. These clouds provide an excellent benchmark for the study of the aerosol influence on modified marine clouds relative to continental clouds, since they form in a much more homogeneous meteorological environment than those at the continental site.

Download or read book Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-08-31 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most significant and uncertain aspects of climate change projections is the impact of aerosols on the climate system. Aerosols influence the climate indirectly by interacting with nearby clouds leading to small changes in cloud cover, thickness, and altitude, which significantly affect Earth's radiative balance. Advancements have been made in recent years on understanding the complex processes and atmospheric interactions involved when aerosols interact with surrounding clouds, but further progress has been hindered by limited observations. The National Academies of Sciences, Engineering, and Medicine organized a workshop to discuss the usefulness of the classified observing systems in advancing understanding of cloud and aerosol interactions. Because these systems were not developed with weather and climate modeling as a primary mission objective, many participants said it is necessary for scientists to find creative ways to utilize the data. The data from these systems have the potential to be useful in advancing understanding of cloud and aerosol interactions. This publication summarizes the presentations and discussions from the workshop.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Atmospheric Radiation Measurement ARM Program written by D. D. Turner and published by . This book was released on 2018-03-09 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulation of Aerosol Cloud Interactions in the WRF Model at the Southern Great Plains Site written by Jonathan Michael Vogel and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aerosol direct and indirect effects were investigated for three specific cases during the March 2000 Cloud IOP at the SGP site by using a modified WRF model. The WRF model was previously altered to include a two-moment bulk microphysical scheme for the aerosol indirect effect and a modified Goddard shortwave radiation scheme for the aerosol direct effect. The three cases studied include a developing low pressure system, a low precipitation event of mainly cirrus clouds, and a cold frontal passage. Three different aerosol profiles were used with surface concentrations ranging from 210 cm^-3 to 12,000 cm^-3. In addition, each case and each aerosol profile was run both with and without the aerosol direct effect. Regardless of the case, increasing the aerosol concentration generally increased cloud water and droplet values while decreasing rain water and droplet values. Increased aerosols also decreased the surface shortwave radiative flux for every case; which was greatest when the aerosol direct effect was included. For convective periods during polluted model runs, the aerosol direct effect lowered the surface temperature and reduced convection leading to a lower cloud fraction. During most convective periods, the changes to cloud, rain, and ice water mixing ratios and number concentrations produced a nonlinear precipitation trend. A balance between these values was achieved for moderate aerosol profiles, which produced the highest convective precipitation rates. In non-convective cases, due to the presence of ice particles, aerosol concentration and precipitation amounts were positively correlated. The aerosol threshold between precipitation enhancement and suppression should be further studied for specific cloud types as well as for specific synoptic weather patterns to determine its precise values. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148070

Download or read book Investigation of the Aerosol Indirect Effect at the Southern Great Plains Using Ground Based Remote Sensors and Modeling written by Graham Feingold and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The attached document is the final report in association with closeout.

Download or read book A Plan for a Research Program on Aerosol Radiative Forcing and Climate Change written by National Research Council and published by National Academies Press. This book was released on 1996-04-17 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book recommends the initiation of an "integrated" research program to study the role of aerosols in the predicted global climate change. Current understanding suggest that, even now, aerosols, primarily from anthropogenic sources, may be reducing the rate of warming caused by greenhouse gas emissions. In addition to specific research recommendations, this book forcefully argues for two kinds of research program integration: integration of the individual laboratory, field, and theoretical research activities and an integrated management structure that involves all of the concerned federal agencies.

Download or read book Study of Aerosol Cloud Radiation Interactions Over the ARM SGP Site written by C. Chuang and published by . This book was released on 2006 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: While considerable advances in the understanding of atmospheric processes and feedbacks in the climate system have led to a better representation of these mechanisms in general circulation models (GCMs), the greatest uncertainty in predictability of future climate arises from clouds and their interactions with radiation. To explore this uncertainty, cloud resolving model has been evolved as one of the main tools for understanding and testing cloud feedback processes in climate models, whereas the indirect effects of aerosols are closely linked with cloud feedback processes. In this study we incorporated an existing parameterization of cloud drop concentration (Chuang et al., 2002a) together with aerosol prediction from a global chemistry/aerosol model (IMPACT) (Rotman et al., 2004; Chuang et al., 2002b; Chuang et al., 2005) into LLNL cloud resolving model (Chin, 1994; Chin et al., 1995; Chin and Wilhelmson, 1998) to investigate the effects of aerosols on cloud/precipitation properties and the resulting radiation fields over the Southern Great Plains.