Improved Understanding of Trends, Variations, and Causes of Atmospheric Aerosols Using Ground Measurements, Satellite Observations, and Atmospheric Chemistry Modeling PDF Download

Author: Xueke Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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A good understanding of trends, variations, and causes of atmospheric aerosols is vital to quantifying the role of air quality in climate change and health concerns and for informing relevant regulatory policies. This thesis presents four projects that exploit a range of observational data and modeling tools to characterize and interpret aerosol dynamics and its potential determinates. An econometric model is implemented to identify aerosol variations, predictions, and the driving forces using six sites spreading across North America and East Asia during 2003-2015. Regional differences caused by impacts of climatology and land cover types are observed. Statistical validation of time series ARIMA models indicates the applicability and feasibility of ARIMA modeling. The reasonably-predicted AOD values could provide reliable estimates to inform better the decision-making for sustainable environmental management and the initiative of reforestation on emission sinks could have potential implications for climate change mitigation. The time series analyses and modeling of aerosol variability are further investigated in a spatially continuous framework based on the valuable spatiotemporal dimension of the remote sensing data over the contiguous United States (U.S.) and China. By comparing variations and trends in these two countries, we attribute the large differences to the energy strategies, economic and urban development, and lifestyle activities. Areas most suitable for applying the model for prediction are those with high AOD quality, high completeness of AOD data, low-AOD values, and AOD time series with clear seasonal variations. Then, a geographically weighted regression (GWR) model is employed to estimate PM2.5 concentration and analyze its relationships with AOD, meteorological variables, and nighttime light (NTL) data across the Northeastern United States in 2013. Improved GWR model performance is found for the warm season when applying the index that incorporates normalized difference vegetation index (NDVI) into NTL (17% and 7.26% better than GWR model without NDVI and NTL data and GWR model without NTL data, respectively). The spatial distribution of the estimated PM2.5 levels clearly reveals patterns consistent with those densely populated areas and high traffic areas. Finally, an evaluation framework to identify both mean and extreme conditions of PM2.5 is proposed and applied to the WRF-CMAQ simulations over the contiguous U.S. for the period of 2001-2010. While the model exhibits satisfactory performance over the eastern U.S., PM2.5 mean variations and extreme trends in the western U.S. are not well represented partly due to the complex terrains and active fire activities. Moreover, the relationship between extreme PM2.5 pollution episodes and abnormal synoptic conditions is quantified. More extreme PM2.5 pollution episodes are expected in a warming climate, with rural stations and the western U.S. suffer the most.

Author: Melanie Hammer
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Atmospheric aerosols have significant impacts on climate and human health. However, the exact magnitude of the climate and health effects of aerosols remains highly uncertain, due to the large variability in aerosol physical and chemical properties. The use of satellite observations of aerosol properties in conjunction with global chemical transport models can improve our understanding of the interactions of aerosols with radiation and their impacts on health. Using GEOS-Chem coupled with a radiative transfer model, we develop a global simulation of the Ultraviolet Aerosol Index (UVAI) to interpret satellite UVAI observations. This simulation allows us to constrain the absorption by brown carbon (BrC) aerosol produced from biomass burning. Inclusion of absorption by BrC in GEOS-Chem reduces tropospheric hydroxyl radical by reducing the frequency of the photolysis of ozone. We calculate the direct radiative effect (DRE) of BrC, and find that absorbing BrC changes the global annual mean all-sky top of atmosphere DRE by +0.03 W m−2 and all-sky surface DRE by −0.08 W m−2. We interpret trends in satellite observed UVAI values using our UVAI simulation for 2005-2015 to improve our understanding of trends in global aerosol composition. Trends in absorption by dust dominate the simulated UVAI trends over desert regions. The UVAI simulation underestimates positive UVAI trends over Central Asia, possibly due to an increasing dust source from the desiccating Aral Sea that may not yet be represented by models. Trends in absorption by BrC dominate UVAI trends over biomass burning regions. Trends in scattering by secondary inorganic aerosol dominate UVAI trends over the eastern United States and eastern India. We estimate surface PM2.5 concentrations using information from satellites, simulation, and ground monitors for the years 2000-2017. These combined PM2.5 estimates benefit from recent updates to satellite AOD sources, developments in chemical transport models, and expanded ground monitor measurements. We find improved agreement between our PM2.5 estimates and ground monitors versus prior work. We use our improved estimates to calculate trends in PM2.5 both globally and regionally in order to understand the exposures of the global population.

Author: Caroline Parworth
Publisher:
ISBN: 9780355594157
Category :
Languages : en
Pages : 0

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Aerosols, or particulate matter (PM), can affect climate through scattering and absorption of radiation and influence the radiative properties, precipitation efficiency, thickness, and lifetime of clouds. Aerosols are one of the greatest sources of uncertainty in climate model predictions of radiative forcing. To fully understand the sources of uncertainty contributing to the radiative properties of aerosols, measurements of PM mass, composition, and size distribution are needed globally and seasonally. To add to the current understanding of the seasonal and temporal variations in aerosol composition and chemistry, this study has focused on the quantification, speciation, and characterization of atmospheric PM in urban and rural regions of the United States (US) for short and long periods of time. In the first two chapters, we focus on 1 month of aerosol and gas-phase measurements taken in Fresno, CA, an urban and agricultural area, during the National Aeronautics and Space Administration's (NASA) field study called DISCOVER-AQ. This air quality measurement supersite included a plethora of highly detailed chemical measurements of aerosols and gases, which were made at the same time as similar aircraft column measurements of aerosols and gases. The goal of DISCOVER-AQ is to improve the interpretation of satellite observations to approximate surface conditions relating to air quality, which can be achieved by making concurrent ground- and aircraft-based measurements of aerosols and gases. We begin in chapter 2 by exploring the urban aerosol and gas-phase dataset from the NASA DISCOVER-AQ study in California. Specifically, we discuss the chemical composition and mass concentration of water-soluble PM2.5 that were measured using a particle-into-liquid sampler with ion chromatography (PILS-IC) in Fresno, California from January 13–February 10, 2013. This data was analyzed for ionic inorganic species, organic acids and amines. Gas-phase species including HNO3 and NH3 were collected with annular denuders and analyzed using ion chromatography. Using the thermodynamic E-AIM model, inorganic particle water mass concentration and pH were calculated for the first time in this area. Organic particle water mass concentration was calculated from [kappa]-Köhler theory. In chapter 3 further analysis of the aerosol- and gas-phase data measured during DISCOVER-AQ was performed to determine the effectiveness of a local residential wood burning curtailment program in improving air quality. Using aerosol speciation and concentration measurements from the 2013 winter DISCOVER-AQ study in Fresno, CA, we investigate the impact of residential wood burning restrictions on fine particulate mass concentration and composition. Key species associated with biomass burning in this region include K+, acetonitrile, black carbon, and biomass burning organic aerosol (BBOA), which represents primary organic aerosol associated with residential wood burning. Reductions in acetonitrile associated with wood burning restrictions even at night were not observed and most likely associated with stagnant conditions during curtailment periods that led to the buildup of this long-lived gas. In chapter 4 we transition to the rural aerosol dataset from the DOE SGP site. We discuss the chemical composition and mass concentration of non-refractory submicron aerosols (NR-PM1) that were measured with an aerosol chemical speciation monitor (ACSM) at the DOE SGP site from November 2010 through June 2012. Positive matrix factorization (PMF) was performed on the measured organic aerosol (OA) mass spectral matrix using a newly developed rolling window technique to derive factors associated with distinct sources, evolution processes, and physiochemical properties. The rolling window approach captured the dynamic variations of the chemical properties of the OA factors over time. Three OA factors were obtained including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a BBOA factor. Sources of NR-PM1 species at the SGP site were determined from back trajectory analyses. NR-PM1 mass concentration was dominated by organics for the majority of the study with the exception of winter, when NH4N33 increased due to transport of precursor species from surrounding urban and agricultural regions and also due to cooler temperatures. Chapter 5 is a continuation of chapter 4, where we will explore the use of the multilinear engine (ME-2) as a factor analysis technique, which is an algorithm used for solving the bilinear model called positive matrix factorization (PMF). The importance of ME-2 and its potential application on the long-term aerosol chemical speciation monitor (ACSM) data collected from the Department of Energy (DOE) Southern Great Plains (SPG) site will be discussed. ME-2 was performed on 19 months of OA mass spectral data obtained from the ACSM at the SGP site. Evaluation of ME-2 results are presented, followed by comparison of ME-2 factor results with corresponding OACOMP factor results reported in chapter 4. We show that ME-2 can determine a biomass burning organic aerosol (BBOA) factor during periods when OACOMP cannot. (Abstract shortened by ProQuest.)

Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309443458
Category : Science
Languages : en
Pages : 53

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Book Description
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.

Author: Panel on Aerosol Radiative Forcing and Climate Change
Publisher: National Academies Press
ISBN: 0309588871
Category : Science
Languages : en
Pages : 180

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Book Description
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.

Author: Ken S. Carslaw
Publisher: Elsevier
ISBN: 0128231726
Category : Science
Languages : en
Pages : 856

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Book Description
The ever-diversifying field of aerosol effects on climate is comprehensively presented here, describing the strong connection between fundamental research and model applications in a way that will allow both experienced researchers and those new to the field to gain an understanding of a wide range of topics. The material is consistently presented at three levels for each topic: (i) an accessible "quick read" of the essentials, (ii) a more detailed description, and (iii) a section dedicated to how the processes are handled in models. The modelling section in each chapter summarizes the current level of knowledge and what the gaps in this understanding mean for the effects of aerosols on climate, enabling readers to quickly understand how new research fits into established knowledge. Definitions, case studies, reference data, and examples are included throughout. Aerosols and Climate is a vital resource for graduate students, postdoctoral researchers, senior researchers, and lecturers in departments of atmospheric science, meteorology, engineering, and environment. It will also be of interest to those working in operational centers and policy-facing organizations, providing strong reference material on the current state of knowledge. Includes a section in each chapter that focuses on the treatment of relevant aerosol processes in climate models Provides clear exposition of the challenges in understanding and reducing persistent gaps in knowledge and uncertainties in the field of aerosol-climate interaction, going beyond the fundamentals and existing knowledge Authored by experts in modeling and aerosol processes, analysis or observations to ensure accessibility and balance

Author: Erica J. Alston
Publisher:
ISBN:
Category : Air
Languages : en
Pages :

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Book Description
Tropospheric aerosol information from NASA satellites in space has reached the milestone of ten years of continuous measurements. These higher resolution satellite aerosol records allow for a broader regional perspective than can be gained using only sparsely located ground based monitoring sites. Decadal satellite aerosol data have the potential to advance knowledge of the climatic impacts of aerosols through better understanding of solar dimming/brightening and radiative forcings on regional scales, as well as aid in air quality applications. The goal of this thesis is to develop and implement methodologies for using satellite remotely sensed data in conjunction with ground based observations and modeling for characterization of regional aerosol variations with applications to air quality and climate studies in the Southeastern U.S. This region is of special interest because of distinct aerosol types, less warming climate trends compared to the rest of U.S., and growing population. To support this primary goal, a technique is developed that exploits the statistical relationship between PM2.5 (particulate matter that has an aerodynamic radius of 2.5 æm or less) and satellite AOD (Aerosol Optical Depth) from MODIS (Moderate resolution Imaging Spectroradiometer) where a probabilistic approach is used for air quality assessments in the metropolitan Atlanta area. The metropolitan Atlanta area experiences the poorest air quality during the warmer seasons. We found that satellite AODs capture a significant portion of PM2.5 concentration variability during the warmer months of the year with correlation values above 0.5 for a majority of co-located (in time and space) ground based PM2.5 monitors, which is significant at the 95% confidence interval. The developed probabilistic approach uses five years of satellite AOD, PM2.5 and their related AQI (Air Quality Index) to predict future AQI based solely on AOD retrievals through the use of AOD thresholds, e.g., 80% of Code Green AQI days have AOD below 0.3. This approach has broad applicability for concerned stakeholders in that it allows for quick dissemination of pertinent air quality data in near-real time around a satellite overpass. Examination of the use of multiple satellite sensors to aid in investigating the impacts of biomass burning in the region is performed. The utility of data fusion is evaluated in understanding the effects of the large wildfire that burned in May 2007. This wildfire caused PM2.5 in the metropolitan Atlanta area to exceed healthy levels with some measurements surpassing 150 æg/m3 during the month. OMI (Ozone Monitoring Instrument) AI (Aerosol Index), which qualitatively measures absorbing aerosols, have high values of more than 1.5 during May 26 - 31, 2007. CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) a space based lidar was used to determine the vertical structure of the atmosphere across the region during the active fire period. CALIPSO was able to identify wildfire aerosols both within the planetary boundary layer (likely affects local air quality) and aloft where aerosol transport occurs. This has important implications for climatic studies specifically aerosol radiative effects. In-depth analysis of the satellite and ground based aerosol data records over the past decade (2000 - 2009) are performed from a climatic perspective. The long temporal scale allowed for better characterization of seasonality, interannual variability, and trends. Spatial analysis of ten years of AOD from both MODIS and MISR (Multi-angle Imaging Spectroradiometer) showed little variability of AOD during the winter with mean AOD below 0.1 for the entire region, while the summer had decidedly more variability with mean AOD around 0.33 for MODIS and 0.3 for MISR. Seasonal analysis of the PM2.5 revealed that summer means are twice as high as winter means for PM2.5. All of the datasets show interannual variability that suggests with time AOD and PM2.5 are decreasing, but seasonal variability obscured the detection of any appreciable trends in AOD; however, once the seasonal influence was removed through the creation of monthly anomalies there were decreasing trends in AOD, but only MODIS had a trend of -0.00434 (per month) that statistically significant at the 95% confidence level. Satellite and ground-based data are used to assess the radiative impacts of aerosols in the region. The regional TOA (Top Of the Atmosphere) direct radiative forcing is estimated by utilizing satellite AOD from MODIS and MISR both on Terra, along with satellite derived cloud fraction, surface albedo (both from MODIS), and single scattering albedo (SSA) from MISR data from 2000 - 2009. Estimated TOA forcing varied from between - 6 to -3 W/m2 during the winter, and during the warmer months there is more variation with [delta]F varying between -28 to -12.6 W/m2 for MODIS and -26 to -11 W/m2 for MISR. The results suggest that when AOD, cloud fraction and surface albedo are all consider they add an additional 6 W/m2 of TOA forcing compared to TOA forcing due to aerosol effects only. Varying SSA can create changes in TOA forcing of about 5 W/m2. With removal of the seasonal variability timeseries anomaly trend analysis revealed that estimated TOA forcing is decreasing (becoming less negative) with MODIS based estimates statistically significant at the 95% confidence level. Optical and radiative 1-D radiative transfer modeling is performed to assess the daily mean TOA forcing and forcing at the surface for representative urban and background aerosol mixtures for summer and winter. During the winter, modeled TOA forcing is -2.8 and -5 W/m2 for the WB and WU cases, and the modeled summer TOA forcings (SB = -13.3 W/m2) also generally agree with earlier estimates. While surface forcings varied from -3 to -210 W/m2. The radiative forcing efficiency at the TOA (amount of forcing per unit of AOD at 550 nm) varied from -9 to - 72 W/m2 [tau]-1, and RFE at the surface varied from -50 to -410 W/m2 [tau]-1. It was found that the forcing efficiency for biomass burning aerosols are similar to the forcing efficiency of background aerosols during the summer that highlights the importance of possible increased biomass burning activity. Ultimately, the methodologies developed in this work can be implemented by the remote sensing community and have direct applicability for society as a whole.

Author: Jing Li
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Based on the sensitivity studies, an optimal fitting technique based on AERONET data is developed to better constrain aerosol dry size parameterization in the GCM. Model results for AOD and SSA are also improved by adjusting the size and applying "uncertainty parameters". The fitting results indicate an overall underestimate in GCM aerosol loading. In particular, aerosol absorption has been underestimated by approximately a factor of 2. The low bias might be attributed to insufficient aerosol mass loading, lack of internal mixing of black carbon with other species, etc. After incorporating the optimized sizes and uncertainty parameters into the GCM, estimated global mean DRF is significantly larger than the original aerosol field. Regionally the changes in DRF are more diverse due to the relative fraction of absorbing and non-absorbing aerosols. The method still has limitations. Further improvements are required including examining the fine/coarse aerosol fraction, better identifying the absorbing species, and using advanced observations with global coverage.

Author: Hayder Abdul-Razzak
Publisher: BoD – Books on Demand
ISBN: 9535107283
Category : Science
Languages : en
Pages : 494

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Book Description
The book is divided into two sections. The first section presents characterization of atmospheric aerosols and their impact on regional climate from East Asia to the Pacific. Ground-based, air-born, and satellite data were collected and analyzed. Detailed information about measurement techniques and atmospheric conditions were provided as well. In the second section, authors provide detailed information about the organic and inorganic constituents of atmospheric aerosols. They discuss the chemical and physical processes, temporal and spatial distribution, emissions, formation, and transportation of aerosol particles. In addition, new measurement techniques are introduced. This book hopes to serve as a useful resource to resolve some of the issues associated with the complex nature of the interaction between atmospheric aerosols and climatology.

Author: Zev Levin
Publisher: Springer Science & Business Media
ISBN: 1402086903
Category : Science
Languages : en
Pages : 399

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Book Description
Life on Earth is critically dependent upon the continuous cycling of water between oceans, continents and the atmosphere. Precipitation (including rain, snow, and hail) is the primary mechanism for transporting water from the atmosphere back to the Earth’s surface. It is also the key physical process that links aspects of climate, weather, and the global hydrological cycle. Changes in precipitation regimes and the frequency of extreme weather events, such as floods, droughts, severe ice/snow storms, monsoon fluctuations and hurricanes are of great potential importance to life on the planet. One of the factors that could contribute to precipitation modification is aerosol pollution from various sources such as urban air pollution and biomass burning. Natural and anthropogenic changes in atmospheric aerosols might have important implications for precipitation by influencing the hydrological cycle, which in turn could feed back to climate changes. From an Earth Science perspective, a key question is how changes expected in climate will translate into changes in the hydrological cycle, and what trends may be expected in the future. We require a much better understanding and hence predictive capability of the moisture and energy storages and exchanges among the Earth’s atmosphere, oceans, continents and biological systems. This book is a review of our knowledge of the relationship between aerosols and precipitation reaching the Earth's surface and it includes a list of recommendations that could help to advance our knowledge in this area.