John H. Seinfeld - US grants

The atmospheric chemistry and gas-to-particle conversion phenomena of biogenic hydrocarbon systems will be investigated in this research project. The goals of the research are to elucidate the gas-phase photooxidation pathways of key biogenic hydrocarbons, to identify the aerosol-forming capability of these hydrocarbons, to further understanding of gas-to-particle conversion phenomena in atmospheric organic systems, and to evaluate the applicability of nucleation theories to atmospheric species. Outdoor smog chamber experiments will be conducted with isoprene/NOx and beta pinene/NOx mixture over a spectrum of concentration levels. Quantities to be measured include hydrocarbon, O3, NO, NO2 concentrations, aerosol size distributions by differential mobility analyzer, optical particle counter and epiphianiometer, and aerosol molecular composition by GC/MS and FTIR analyses. Aerosol species identified will be studied for nucleation either as single component or binary, with water. Theoretical work will continue on the development of a kinetic theory of nucleation. Analysis of the experimental data will involve a description of gas-phase chemical reaction mechanisms, including the generation of condensable species, the nucleation of these species, either homomolecular or binary, and the diffusion of these and additional species to particles.

Seinfeld 9307603 Gas-to-particle conversion is a ubiquitous process in the atmosphere, understanding the detailed chemistry and physics of which will allow one to predict the effects of primary gaseous and particulate emissions on airborne particulate matter composition and size. This comprehensive research program determine the mechanisms of secondary organic aerosols formation in the atmosphere for a number of important anthropogenic and biogenic hydrocarbons. Experiments in a 1000 liter indoor reactor will be used to probe gas-phase photooxidation mechanisms. A 4 m3 outdoor smog chamber will be used to generate organic aerosols for molecular speciation analysis by gas chromatography/mass spectrometry, while the 60 m3 outdoor smog chamber will be employed to study the integrated gas-phased and gas-to-particle conversion dynamics. Vapor pressures of individual secondary organic aerosol constituents and of the aerosol generated by hydrocarbon photooxidation will be determined with the tandem differential mobility analyzer (TDMA). Information from the individual experiments studies will be integrated in the data analysis phase. Gas-phase photooxidation mechanisms will be formulated and aerosol physics models will be developed based on the concentration dynamics, molecular speciation, and the physical properties deduced from the TDMA studies.

The goal of this project is to help scientists and engineers carry out computational tasks more effectively by doing research on: - The integration of symbolic and numeric computation to facilitate problem specification, exploration and result verification. - Hierarchies of reusable computational abstractions organized in libraries with well-defined navigational structures. - Exploiting commercial standards and tools for object-request brokers, compound documents, and collaboration infrastructure. The project takes a novel approach to problem-solving environments (PSEs). Its focus is on the entire process of problem-solving from initial conception, symbolic specification, solution, visualization, comparison with experimental data, and feed back. The project focuses on problem-solving environments, not merely programming environments. This focus leads to research on reusable abstractions at all levels of problem-solving. Important abstractions include the problem-solving method itself, method-specific abstractions for sequential and parallel program design, reasoning and debugging, performance analysis and tuning, and frameworks for class libraries. PSEs are more useful when they are more specific. However, rather than build one problem- solving environment for one class of user, application domain, programming language and machine, this project aims at the basic research that will enable us to develop tools for building specific PSEs. To use a metaphor, rather than doing research on workbenches we want to do research on machine tools that can be used to build workbenches. Traditional PSEs deal with extending a workstation environment whereas this project is concerned with developing structured environments for problem-solving. Scientists and engineers collaborate when they solve problems, and they share much more than code. PSEs based on collaboration also provide object-request brokering and compound multimedia document interfaces. Since this vision is both novel and ambitious, a critical aspect of the project is leveraging methods and tools developed for scientific, commercial and home-computing applications.

Recent observations indicate that the air surrounding growing cumulus clouds is sometimes nearly saturated with water vapor. Calculations show that these vapor shrouds or "halos" around clouds can account for a significant increase in the absorption of solar radiation. The purpose of this project is to measure the vapor field around cumulus clouds with high accuracy and resolution and to use the information in calculations of radiative transfer and in assessing the consequences of cloud-environment interactions on cloud microphysics. The specific objectives are as follows:
- To measure the vapor field in and around convective clouds with sufficient detail to characterize the 3-dimensional vapor structure relative to cloud edges;
- To measure concurrently the size distribution, composition, and optical properties of aerosols within the cloud halo;
- To analyze the resulting measurements in order to provide several completely documented cases for use in radiative transfer calculations;
- To carry out radiative transfer analyses including absorption and heating rate calculations for the observed distributions of water vapor, aerosols, and cloud;
- To determine the implications of the radiation analysis for climate modeling.
The measurements will be conducted with the CIRPAS Twin Otter aircraft, equipped with a new instrument called the Fast Water Vapor Monitor developed by Aerodyne Research along with instruments for measuring aerosols, CCN, cloud droplets, and liquid water content. Computer codes with different degrees of complexity will be used for the radiative transfer calculations. The results bear on the question of anomalous cloud absorption, which refers to the discrepancies that have been observed between the observed solar absorption by clouds and the absorption calculated using Mie scattering theory applied to populations of cloud drops. This is a collaborative research project between Cal Tech and Aerodyne Research, Inc. The Aerodyne component of the collaboration is supported by ATM-9910744, Dr. John T. Jayne, PI.

William Goddard, Mario Blanco, and John Seinfeld of the California Institute of Technology are supported by the Division of Chemistry, the Office of Multidisciplinary Activities, and the Division of Chemical and Transport Systems to develop theoretical methodologies which generate thermodynamic properties for use in chemical process simulation and pollutant behavior prediction. This grant is made under the NSF/EPA Partnership for Environmental Research (Technology for a Sustainable Environment). This research will integrate quantum mechanics, molecular dynamics, and statistical mechanics into the next generation of chemical process simulation and design technology. Needed thermodynamic data, such as excess free energies, activity coefficients, and phase diagrams, will be accurately provided by first-principles molecular simulations of aqueous mixtures of organic solvents.

Efficiency in chemical manufacturing is greatly dependent on the quality of the thermodynamic data employed during the chemical process design phase. Due to the enormous number of possible binary and multicomponent mixtures present in a chemical process, such data are often unavailable. Recent advances in atomistic simulations, combined with statistical models for predicting thermodynamic properties of mixtures, will lead to a new approach of achieving pollution prevention through more optimal design of chemical processes.

This project supports the deployment of a Twin Otter aircraft and ground-based measurements as part of ACE-Asia (Aerosol Characterization Experiment). A comprehensive instrument package for the Twin Otter will be available for measurements of aerosol physical, chemical, and optical properties, including size distribution, hygroscopic properties (Tandem Differential Mobility Analyzer), size-segregated chemistry, and a novel single particle spectrometer. The objectives of the research flights are to characterize the aerosol in the Asian outflow region and to perform local and column radiative closure studies. In collaboration with a scientist at HKUST (Hong Kong University of Science and Technology), aerosol samples collected by the aircraft and at ground stations in Cheju Island, Korea, and other locations will be analyzed for organic/elemental carbon (EC/OC) and speciated organics via extraction, derivatization, and GC/MS analysis. Modeling studies will be performed in collaboration with Dr. Carmichael (University of Iowa) using a three-dimensional atmospheric chemical transport model which includes gas-phase chemistry, aerosol microphysics, thermodynamics, gas/particle conversion and anthropogenic emissions.

The effect of aerosols on clouds (aerosol indirect effect) has critically important relevance to radiative transfer and climate forcing. The aerosol indirect effect is still poorly understood, this aggravated by a severe paucity of high quality experimental field data required to produce accurate parameterizations and properly constrain analytical models. This project involves a series of field experiments on the Office of Naval Research Center for Interdisciplinary Remotely-Piloted Aircraft Studies (ONR/CIRPAS) Twin Otter research aircraft (with extramural funding from ONR confirmed) as part of the Intercontinental Transport and Chemical Transformation (ITCT) project during summer 2004 over the Northeastern United States. The California Institute of Technology (CalTech) group will collect a variety of meteorological, aerosol microphysical and chemical data from the Twin Otter and follow with detailed analyses and three-dimensional radiative transfer modeling. The ultimate goal of this project is a robust closure study comparing measured terms in the radiation budget to predictions of those terms from aerosol and cloud properties. Taking into account more advanced aerosol-cloud interaction parameterizations involving low-altitude clouds will lead to more representative modeling of aerosol-cloud-radiation processes on a variety of scales under a general circulation model framework. Results from this study will provide new data and improved insight to our understanding of clouds and climate, reducing present large uncertainties related to quantifying current and predicting future climate change. Broader educational impacts include support for one postdoctoral scholar and two graduate students at CalTech. Through a subcontract to Georgia Institute of Technology to incorporate field data into a general circulation model aerosol-cloud interaction module an additional graduate student will be supported.

This Major Research Instrumentation award supports the acquisition and development of state-of-the art instrumentation for aerosol research. It will enable simultaneous characterization of the chemistry occurring in the gas and condensed phases as secondary aerosol forms and evolves in a laboratory setting. A benchtop instrument for gas chromatography - time-of-flight mass spectrometry (GC-TOF-MS) will be purchased to provide rapid chemical analysis of hydrocarbons and oxygenated volatile organic compounds. A triple quadrupole mass spectrometer will be coupled to an ion chemical ionization front end (TSQ-SICIMS) for real-time analysis of short-lived, reactive compounds. A preparative capillary gas-liquid chromatography (PCGC) instrument will be used to isolate larger quantities of volatile organic compounds for subsequent analysis with a broad array of instruments. Finally, an aerosol trap / concentrator will be developed for use as a front end to the mass spectrometers for rapid analysis of the chemical composition of aerosol.

Studies using these new instruments will provide improved constraints on the mechanisms responsible for production of organic aerosol in Earth's atmosphere. This instrumentation, in combination with the aerosol instrumentation currently available on the Caltech environmental chamber, will enable significant progress in addressing questions such as:
- How important is the formation of low volatility oxidation products in the gas phase to the budget of organic aerosol and how does this chemistry influence the physical properties and environmental effects of atmospheric aerosols?
- How important are aerosol-phase reactions relative to gas-phase oxidation followed by gas-to-particle uptake for determining the chemical composition of the aerosol?
- What are the molecular mechanisms and kinetics of the processes involved in aerosol production?
- What are the most important chemicals leading to aerosol formation (organic acids, oligomers/polymers, etc.) and what are their physicochemical properties (functional groups, molecular mass, stability, volatility, solubility, hygroscopicity, optical absorption, etc.)?
- How do the gas phase and the aerosol composition evolve in the presence of atmospheric oxidants?

Accurate characterization of the chemistry leading to the formation of aerosol in Earth's atmosphere is essential for understanding the interactions of the biosphere and climate as well as for designing appropriate air quality improvement strategies. This aerosol plays a major role in the environment through its deleterious influence on human and animal health and through its impact on visibility in both urban and regional areas. The chemical and physical nature of atmospheric aerosol also determines its light scattering and absorption properties that, in part, control the Earth's radiation field and climate. Finally, the hygroscopicity of the aerosol plays an important role in controlling how efficient an aerosol particle will be for formation of cloud droplets. The instrumentation acquired through this award will provide substantially improved understanding of the nature of the organic chemistry that controls the chemical makeup of atmospheric organic aerosol. The new instrumentation will enhance new and interdisciplinary collaborations of graduate and undergraduate chemists, geochemists, and physicists and their faculty mentors.

Particles in the atmosphere play a key role in cloud formation, acting as nuclei for water droplets. Clouds play an important role in absorbing and reflecting heat, hence they can potentially mitigate or exacerbate global warming. Aerosol-cloud radiative interactions are widely held to be the largest single source of uncertainty in climate model projections of future climate change due to increasing anthropogenic emissions (IPCC, 2007). The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models on these important questions. However, the quantitative representation of these processes is nontrivial and limits our ability to represent them in global climate models (GCMs), resulting in the largest uncertainties in predictions of future climate. Given the timeliness of these questions for advancing GCMs, it is essential to address the unanswered questions in cloud dynamical response to aerosol perturbations.

Intellectual merit. This research is a targeted aircraft campaign with embedded modeling studies to inform the experiment planning and to facilitate the interpretation of the results. The study will use the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft in July 2011 off the coast of Monterey, California, with a full payload of instruments to measure particle and cloud number, mass and composition distributions. The research is composed of three novel and important additional, climate-focused studies:
1. Controlled release and atmospheric distribution of three different size ranges of particles in flight and on or by a dedicated ship;
2. Large Eddy Simulations and Aerosol-Cloud Parcel modeling studies constrained by the observations to test our ability to quantitatively predict the dynamical response to increases in particle concentrations in the natural atmosphere;
3. Satellite analyses of marine stratocumulus to constrain the radiative properties of the natural, perturbed, and regional cloud systems.

Broader impacts. The broader scientific impacts of the research will be the improved understanding of fundamental aerosol-cloud processes that can be incorporated in global climate models to better inform decision makers. The broader educational impacts of the research will be realized through: (1) Promotion of teaching, training and learning through development and piloting of an informal science education program targeting an underserved audience; (2) Broadened participation of underrepresented groups - in this case, retired and elderly people - in research as well as in outreach; (3) Enhancement of infrastructure for teaching through partnerships with an established educational organization (Osher Lifelong Learning Institute); (4) Broad dissemination of results through presentations, peer-reviewed publications and via the web; and (5) Societal benefits in terms of improved understanding of climate science and the related ethical issues.

This project supports a comprehensive study of the role of water in the formation of secondary organic aerosol (SOA). SOA forms as a result of atmospheric oxidation of volatile organic compounds, leading to products that partition between the gas and particle phases. Observed atmospheric levels of organic aerosol, of which the preponderance is SOA, exceed those predicted by current models. Water is ubiquitous in atmospheric particles, but the role of aerosol water in the gas-particle partitioning of organics and in particle-phase chemistry is unclear.

The project will include: (1) application of a rigorous model of the phase behavior and gas-particle partitioning of inorganic-organic aerosol systems; (2) laboratory chamber studies with a full spectrum of volatile organic compounds (VOCs) designed to reveal the mechanism and importance of water in gas-particle partitioning and heterogeneous chemistry in SOA formation; and (3) analysis of ambient data with respect to the role of particle-phase chemistry and acidity in determining SOA formation.

Thermodynamic modeling will be applied to: (1) artificial, well-defined organic-inorganic mixtures; (2) controlled aerosol chamber experiments; and (3) ambient data. The overall goal of the experimental chamber research program is to address comprehensively the effects of relative humidity (RH), aerosol acidity, and particle-phase chemistry on SOA formation. The experiments to be conducted will involve: (1) a full spectrum of VOCs; (2) high and low nitrogen oxide (NOx) levels; (3) variation of seed aerosol acidity; and (4) variation of RH. These include mechanisms of organic aerosol aging that lead to the highly oxidized state found in the atmosphere. In the laboratory chamber studies, unique marker compounds for both particulate-phase chemistry and acidity-enhanced SOA formation will be identified. Evaluation of the extent to which such compounds are present in ambient aerosol samples can shed light on the question of whether it is possible to discern the sources of organic carbon as the aerosol "ages" toward its homogenized, highly oxidized state.

This work will contribute to understanding of climate sensitivity by improving our knowledge of the radiative forcing of atmospheric aerosols. Aerosol radiative forcing depends directly on the mass of aerosols in the atmosphere. Organic aerosols comprise roughly one-half of the global aerosol mass, and as much as 90% of the organic aerosol mass is formed as a result of the gas-phase oxidation of volatile organic compounds. The model of aerosol composition to be developed and the laboratory data to be obtained will be made available to the community.

A postdoctoral scholar and two Ph.D. students will be trained in the project, all of whom will attend scientific conferences to present their research results, which will also be published in peer-reviewed journals.

This research is focused on the study of secondary organic aerosol (SOA), very small particles condensed from the gas phase, in environmental chambers and the effects of gas and particle deposition onto the chamber walls. Modeling studies generally utilize fundamental data from environmental chambers in predicting ambient aerosol concentrations in the atmosphere. Currently a discrepancy exists between model predictions and atmospheric measurements of SOA. The reanalysis of historical chamber experiments indicates that prior reported SOA yields may have been underpredicted. The information from this research is critical for understanding aerosol-induced health effects and contributions to global aerosol radiative forcing.

The proposed work includes: (1) Measurements of the wall deposition rates of individual organic species on the Teflon walls of a chamber and correlation of those rates to molecular properties of the species; (2) Chamber experiments with a wide range of important biogenic and anthropogenic volatile organic compounds in which the competition between vapor transport to particles and the walls is modulated; and (3) Development of a comprehensive model of chamber vapor dynamics that allows quantitative assessment from data on individual species of the impact of vapor wall deposition and extrapolation to atmospheric "wall-less" conditions.

This is a collaborative proposal to build an online, open-access, searchable, central repository for atmospheric chamber data in the United States called ICARUS (Index of Chamber Atmospheric Research in the United States). Fundamental data obtained from chamber studies are routinely used as empirical inputs and constraints in atmospheric models. There are nine major U.S. research institutions participating in this project, including the National Center for Atmospheric Research (NCAR). This sustainable web-based infrastructure for storing, sharing, and using atmospheric chamber data will synergistically facilitate atmospheric chemistry research in the U.S.

The specific objectives of the project are to (1) provide a searchable public index of the chamber experiments from each participating research group; (2) archive past chamber data from each participating group under their indexed chamber experiment; (3) standardize chamber data reporting formats; (4) provide a uniform template for chamber metadata; and (5) streamline future data submissions. The data products included in ICARUS are: (A) gas phase data that describes the time-resolved profiles of volatile organic compounds (VOCs) such as gaseous hydrocarbons, oxidized VOCs, oxidants (OH, O3, NO3), NOx, SO2, and other data; (B) particle phase data that describes yields of secondary organic aerosols (SOA) as well as optical properties, composition (detailed molecular and bulk elemental ratios), and chemical functional groups; (C) supporting information such as relative humidity, temperature, and light flux; (D) the experimental notes required to understand the data (such as reaction timing, mixing procedures, seed particle addition, and so on); and (E) vapor and particulate wall deposition rates that are needed to correct chamber data. At the end of the 3-year project, the database will be transitioned to the Data Stewardship Engineering Team at NCAR.

Atmospheric aerosols, such as fine particles from the incomplete combustion of fossil fuels, wood and other fuels, can modify cloud formations and precipitation. Thus, they have profound impacts on the Earth’s weather and climate systems. The lack of understanding of complex aerosol properties, aerosol-cloud interactions, and aerosol variations in space and time contributes to large uncertainties in the climate assessment and projection. The project aims to investigate how aerosols vary vertically and how aerosols influence cloud development and properties over a large area. Findings of this project are expected to advance our knowledge on aerosol-cloud interactions and address uncertainties in climate change studies. This research project will provide opportunities to integrate research and education by involving underrepresented minority students to conduct the research and incorporating the outcomes from this research into classes at University of California at Los Angeles and California Institute of Technology.

The overarching objective of this research is to characterize the vertical distributions of various types of aerosols and to study their impacts on convective clouds and precipitation through a combination of data analysis based on state-of-the-art satellite data and in situ measurements, as well as aerosol-aware and cloud-resolving WRF modeling. The key scientific questions are (1) what are the specific characteristics and seasonal and regional variations of the vertical distribution of different aerosol types? (2) how do the vertical distributions of various aerosol types affect the micro- and macro-physical properties of convective clouds and the associated precipitation? Three specific tasks will be performed to answer these questions: (1) to examine the specific and unique characteristics of the vertical distributions of various aerosol types in different regions and seasons; (2) to investigate the relationships between vertical distributions of various aerosol types and convective clouds and associated precipitation; (3) to disentangle different aerosol effects (i.e., microphysical effect and radiative effect) as well as meteorological influence, and assess effects of aerosol vertical distributions on convective clouds and precipitation on the seasonal timescale using process-level models. Results from observational analyses will be used to evaluate and constrain model simulations to reduce the uncertainties associated with aerosol-cloud-precipitation interactions.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.