Browsing by Author "Pierce, Jeffrey R., committee member"
Now showing 1 - 11 of 11
Results Per Page
Sort Options
Item Open Access Aerosol parameterizations in space-based near-infrared retrievals of carbon dioxide(Colorado State University. Libraries, 2019) Nelson, Robert Roland, author; Kummerow, Christian D., advisor; O'Dell, Christopher W., advisor; Denning, A. Scott, committee member; Pierce, Jeffrey R., committee member; Hoeting, Jennifer A., committee memberThe scattering effects of clouds and aerosols are one of the primary sources of error when making space-based measurements of carbon dioxide. This work describes multiple investigations into optimizing how aerosols are parameterized in retrievals of the column-averaged dry-air mole fraction of carbon dioxide (XCO2) performed on near-infrared measurements of reflected sunlight from the Orbiting Carbon Observatory-2 (OCO-2). The primary goal is to enhance both the precision and accuracy of the XCO2 measurements by improving the way aerosols are handled in the NASA Atmospheric CO2 Observations from Space (ACOS) retrieval algorithm. Two studies were performed: one on using better informed aerosol priors in the retrieval and another on reducing the complexity of the aerosol parameterization. It was found that using ancillary aerosol information from the Goddard Earth Observing System Model, Version 5 (GEOS-5) resulted in a small improvement against multiple validation sources but that the improvements were restricted by the accuracy and limitations of the model. Implementing simplified aerosol parameterizations that allowed for the retrieval of fewer parameters sometimes resulted in small improvements in XCO2, but further work is needed to determine the optimal way to handle the scattering effects of clouds and aerosols in near-infrared measurements of XCO2. With several multi-million dollar space-based greenhouse gas measurement missions scheduled and in development, the massive amount of measurements will be an incredible boon to the global scientific community, but only if the precision and accuracy of the data are sufficient.Item Open Access Aqueous atmospheric organic processing: effects of fog and cloud composition(Colorado State University. Libraries, 2016) Boris, Alexandra Jeanne, author; Collett, Jeffrey L., advisor; Farmer, Delphine K., committee member; Kreidenweis, Sonia M., committee member; Pierce, Jeffrey R., committee memberCloud and fog droplets are well-suited venues for organic reactions leading to the formation of suspended particulate matter in the atmosphere. Suspended particulate matter formed through aqueous reactions is called "aqueous secondary organic aerosol" or aqSOA, and can interact with solar radiation and adversely impact human and ecosystem health. Although atmospheric observations and lab simulations have verified the formation of aqSOA, little is known about where and when it occurs in the atmosphere. The organic (carbonaceous) reactions leading to aqSOA formation also degrade chemicals in the atmosphere, impacting the potential health effects of fog water deposited to ecosystems and crops. In the present work, studies are described that approach these aqueous oxidation reactions from field and lab perspectives, capturing both complex and simple experiments. Some results will be presented that capture the dynamics of aqSOA formation from studies of in-situ fog chemistry, but the lack of control over environmental variables in these observations will be highlighted. Lab-based reactions of fog and cloud water will also be presented, which oppositely underscore the missing variables in such simplified lab experiments. Despite the need for more advanced experimental design to quantify aqSOA formation and identify its sensitivities to real atmospheric variables, these field and lab approaches have garnered new insight into some key aspects of aqueous oxidation. Fog at Baengnyeong Island (BYI) in the Yellow Sea of Korea was collected in July 2014. Fog chemistry was exemplary of aged atmospheric components: sulfur was almost entirely oxidized (98.9 to 99.8% was present as S(VI) versus S(IV)), and peroxides, which can serve as oxidants, were depleted. Organic acids at times accounted for >50% of the total organic carbon (TOC) by carbon mass, indicating that organic matter was highly oxidized. Although formic and acetic acids were the most abundant, concentrations of ten out of the 18 organic acids quantified were above 1 μM. Some organic sulfur and organic nitrogen species were additionally observed, which may have formed during aqueous reactions in the fog or in humid conditions as air traveled to BYI. Back trajectories demonstrated that the relative humidities of the air masses arriving at BYI were typically >80%, suggesting that oxidation could have taken place in the aqueous phase. The Southern California coast is frequently foggy during the summer months, but in contrast to BYI, is closer to many atmospheric chemical emissions sources. Fog water was collected at Casitas Pass (CP) near Ventura, California in June 2015. Regional oil drilling and/or refinery emissions influenced the composition of foggy air, as did biogenic and marine emissions. Only 20% of TOC on average was contributed by organic acids, suggesting influence of fresher organic emissions than observed at BYI. After 3-5 hours of foggy conditions, however, organic sulfur and organic nitrogen species were observed, suggesting possible in-fog oxidation. A contrast between the 2015 study and a 1985/6 study demonstrated improved air quality compared to 1985/6, with lower concentrations of anthropogenically derived species (NH4+, NO3-, SO42-, acetate, formate, and formaldehyde), but similar concentrations of naturally derived species (Na+, Cl-, Ca2+, and Mg2+). Lab work involving aqueous oxidation within real cloud water revealed that organic constituents of cloud water caused oxidation reactions to slow due to competition for oxidant. Inorganic species (NH4+, SO42- and NO3-) at concentrations relevant to polluted cloud water did not have a statistically significant effect on oxidation. Mechanisms of oxidation were also surprisingly unaffected by cloud water components: similar low molecular mass organic acids were observed as products of oxidation in pure and cloud water. Oxidation of real cloud water sample constituents in the lab revealed that organosulfate species were produced when sufficient SO42- and organic species concentrations were present. Four fog and cloud water samples were oxidized, demonstrating different oxidation regimes: a BYI fog was clearly more aged such that organosulfate esters were formed; cloud water from Mount Tai, China contained biomass burning and anthropogenic aromatic emissions and produced organic acids similar to those observed from nitrophenol chemical standard oxidations; and fog water from CP containing fresher emissions produced mainly low molecular mass organic acids. The aqueous oxidation of biomass burning emissions collected using a mist chamber resulted in the formation of a variety of low molecular mass organic acids. No apparent structure-activity relationship was observed: aliphatic and aromatic species were oxidized at similar rates when exposed to OH radicals. The degradation of potentially toxic organic nitrogen species as well as net production of semi-volatile organic acid products were observed, demonstrating that in-cloud oxidation of biomass burning emissions likely contributes to the chemical evolution and organic aerosol mass within smoke plumes. Overall, there is still a need for advanced experiment development in the field of aqueous organic atmospheric chemistry. The finding that physical processes obscured effects of aqueous reactions during fog field studies should, likewise, guide future field work toward the concurrent measurement of microphysical parameters and possible development of higher efficiency techniques for droplet collection and/or real-time chemical analyses. However, the combination of bulk reactions and fog studies employed within this thesis has allowed the effects of real fog and cloud water chemistry on aqSOA formation to be demonstrated. The common oxidation products identified under most aqueous atmospheric regimes, including low molecular mass organic acid species, but specific environmental requirements for other products such as organosulfates, should guide future research in identifying molecular tracers of aqSOA and sensitivity studies of aqSOA formation to environmental factors.Item Open Access Daytime evolution of oxidized reactive nitrogen in western U.S. wildfire smoke plumes: in situ and satellite observations(Colorado State University. Libraries, 2020) Juncosa Calahorrano, Julieta Fernanda, author; Fischer, Emily V., advisor; Bond, Tami, committee member; Pierce, Jeffrey R., committee member; Ravishankara, A. R., committee memberThe Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) deployed the NSF/NCAR C-130 aircraft in summer 2018 across the western U.S. to sample wildfire smoke during its first day of atmospheric evolution. We present a summary of a subset of oxidized nitrogen species (NOy) in plumes sampled in a pseudo-lagrangian fashion. Emissions of nitrogen oxides (NOx = NO + NO2) and nitrous acid (HONO) are rapidly converted to more oxidized forms. Within 4 hours, ∼86% of the measured NOy (∑ NOy) is in the form of peroxy acyl nitrates (PANs) (∼37%), particulate nitrate (pNO3) (∼26%) and gas-phase organic nitrates (∼23%). The average e-folding time and distance for NOx are ∼90 minutes and ∼40 km, respectively. Nearly no enhancements in nitric acid (HNO3) were observed in plumes sampled in a pseudo-lagrangian fashion, implying HNO3-limited ammonium nitrate (NH4NO3) formation, with one notable exception that we highlight as a case study. We also summarize the observed partitioning of ∑ NOy in all the smoke-impacted samples intercepted during WE-CAN. In the smoke-impacted samples intercepted below 3 km above sea level (ASL), HNO3 is the dominant form of ∑ NOy and its relative contribution increases with smoke age. Above 3 km ASL, the contributions of PANs and pNO3 to ∑ NOy increase with altitude. WE-CAN also sampled smoke from multiple fires mixed with anthropogenic emissions over the California Central Valley. We distinguish samples where anthropogenic NOx emissions appear to lead to an increase in NOx abundances by a factor of 4 and contribute to additional PAN formation. We utilize data from the Cross-Track Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite, which continues the thermal infrared peroxyacetyl nitrate (PAN) satellite record established by the Tropospheric Emission Spectrometer (TES) onboard the Aura satellite. CrIS provides improved spatial resolution, allowing for improved analysis opportunities. Here we present an analysis of CrIS PAN retrievals over the western US during the summer 2018 wildfire season. The analysis period coincides with WE-CAN. CrIS is capable of detecting PAN and CO enhancements from smoke plumes sampled during WE-CAN, especially those that became active before the satellite overpass or burned for several days (e.g., Carr Fire, Mendocino Complex Fire). The analysis show that ∼40 - 70% of PAN over the western U.S. can be attributed to smoke from wildfires. The contribution of smoke from wildfires to free tropospheric PAN generally increases with latitude. We calculate peroxyacetyl nitrate (PAN) excess mixing ratios normalized by CO (NEMRs) in fresh smoke plumes from fires and follow the evolution as these plumes are transported several hours to days downwind. This analysis shows that elevated PAN within smoke plumes can be detected several states downwind from the fire source. The combination of high CrIS spatial resolution and favorable background conditions on 13 September 2018 permits detecting chemical changes within the Pole Creek smoke plume in Utah. In this plume, CrIS PAN NEMRs increase from < 1% to 3.5% within 3 - 4 hours of physical aging. These results are within the range observed in fresh plumes sampled during WE-CAN, where PAN NEMRs increased from 1.5% to 4% within 4 hours of physical aging.Item Open Access Development, characterization, and deployment of a high-resolution time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS) for the detection of carboxylic acids and trace-gas species in the troposphere(Colorado State University. Libraries, 2016) Brophy, Patrick M., author; Farmer, Delphine, advisor; Bernstein, Elliot R., committee member; McNaughton, Brian, committee member; Pierce, Jeffrey R., committee member; Ravishankara, Akkihebbal R., committee memberA historical account of the advances leading to modern high-resolution time-of-flight chemical ionization mass spectrometers (HR-TOF-CIMS) for gas-phase measurements is presented. Recent literature detailing the description of the HR-TOF-CIMS is critically evaluated and put into the context of the historical literature. The development of the HR-TOF-CIMS with reagent ion switching capabilities in the negative mode (acetate and iodide reagent ions), and a novel, low-pressure high-flow inlet with online calibration system is shown to work well in the field. Findings from the deployment of this measurement system during the 2013 Southern Oxidant and Aerosol Study are discussed. Subsequent work with voltage scanning methodologies for controlling cluster transmission is presented and applied to potential aerosol mass chamber experiments examining the oxidation of alpha-pinene. The applicability of acetate chemical ionization to the direct headspace analysis of beer samples is presented. Lastly, the future directions of acetate chemical ionization and voltage scanning are discussed in relation to numerous recent developments related to both gas-phase measurements and new particle formation.Item Open Access Emissions, evolution, and transport of ammonia (NH₃) from large animal feeding operations: a summertime study in northeastern Colorado(Colorado State University. Libraries, 2024) Juncosa Calahorrano, Julieta Fernanda, author; Fischer, Emily V., advisor; Collett, Jeffrey L., Jr., committee member; Pierce, Jeffrey R., committee member; Jathar, Shantanu H., committee memberThe Transport and Transformation of Ammonia (TRANS2Am) airborne field campaign occurred over northeastern Colorado during the summers of 2021 and 2022. TRANS2Am measured ammonia NH3 emissions from cattle feedlots and dairies with the goal of describing the near-field evolution of the NH3 emitted from animal feeding operations. Most of the animal husbandry facilities in Colorado are co-located with oil and gas development within the Denver-Julesburg basin, an important source of methane (CH4) and ethane (C2H6) in the region. Leveraging TRANS2Am observations, this dissertation presents estimates of NH3 emissions ratios with respect to CH4 (NH3 EmR), with and without correction of CH4 from oil and gas, for 29 feedlots and dairies in the region. The data show larger emissions ratios than previously reported in the literature with a large range of values (i.e., 0.1 - 2.6 ppbv ppbv-1). Facilities housing cattle and dairy had a mean (std) of 1.20 (0.63) and 0.29 (0.08) ppbv ppbv-1, respectively. NH3 emissions have a strong dependency with time of day, with peak emissions around noon and lower emissions earlier in the morning and during the evening. Only 15% of the total ammonia (NHx) is in the particle phase (i.e., NH4+) near major sources during the warm summer months. Finally, estimates of NH3 emission rates from 4 optimally sampled facilities range from 4 - 29 g NH3 · h-1 · hd-1. This work also investigates the nearfield evolution of NH3 in five plumes from large animal husbandry facilities observed during TRANS2Am using a mass balance approach with CH4 as a conservative tracer in the timescales of plume transport. Since the plumes in TRANS2Am were not sampled in a pseudo-lagrangian manner, an empirical model is needed to correct for variations in summertime NH3 emissions as a function of local time (LT) (CF = 1.87ln(LT) - 3.95). Results from the mass balance approach show that the average summertime NH3 decay time below 80% and 60% against deposition in plumes from large animal feeding operations is ~1 and ~2 hours, respectively. Additionally, we present estimates of deposition/emission fluxes every 5 km downwind of the plume. We found that deposition almost always happens in the first 10 km from the emission source. Beyond that, the complex environmental exchange of NH3 between the atmosphere and the surface suggests that fresh NH3 emissions from small nearby sources, water bodies, and crops/soil could contribute to sufficient NH3 to switch the direction of the flux (to emission). Large uncertainties still remain in emission and deposition fluxes, shining light on the need for more measurements in the region. To our knowledge, this is the first study presenting NH3 evolution in the atmosphere using a conservative tracer and airborne measurements. The second goal of TRANS2Am was to investigate easterly wind conditions capable of moving agricultural emissions of ammonia (NH3) through urban areas and into the Rocky Mountains. TRANS2Am captured 6 of these events, unveiling important commonalities. 1) NH3 enhancements are present over the mountains on summer afternoons when easterly winds are present in the foothills region. 2) The abundance of summertime gas-phase NH3 is 1 and 2 orders of magnitude higher than particle-phase NH4+ over the mountains and major agricultural sources, respectively. 3) During thermally driven circulation periods, emissions from animal husbandry sources closer to the mountains likely contribute more to the NH3 observed over the mountains than sources located further east. 4) Transport of summertime plumes from major animal husbandry sources in northeastern Colorado westward across the foothills requires ~5 hours. 5) Winds drive variability in the transport of NH3 into nearby mountain ecosystems, producing both direct plume transport and recirculation. A similar campaign in other seasons, including spring and autumn, when synoptic scale events can produce sustained upslope transport, would place these results in context.Item Open Access Evidence for a biological control on emissions of marine ice nucleating particles: laboratory, field and modeling results(Colorado State University. Libraries, 2017) McCluskey, Christina Song, author; Kreidenweis, Sonia M., advisor; DeMott, Paul J., advisor; Collett, Jeffrey L., committee member; Pierce, Jeffrey R., committee member; Mykles, Donald L., committee memberTo view the abstract, please see the full text of the document.Item Open Access Formation and evolution of secondary organic aerosol in laboratory experiments: precursors, processes, and properties(Colorado State University. Libraries, 2022) He, Yicong, author; Jathar, Shantanu H., advisor; Pierce, Jeffrey R., committee member; Bond, Tami C., committee member; Volckens, John, committee memberSecondary organic aerosol (SOA) is an important fraction of atmospheric PM2.5 which is defined as fine-mode aerosols with diameters less than 2.5 μm. SOA is ubiquitous in the atmosphere and can have considerable impacts on the climate, air quality and human health. We are limited in our ability to predict the spatial and temporal distribution of SOA and assess its environmental impacts, because current three-dimensional chemical transport models (CTM) still have large biases and relatively weak correlations with observations of SOA. One reason for the model-observation discrepancy could be that we still lack a full understanding of the precursors, chemical/physical processes, and properties of SOA that govern its formation and evolution. Therefore, there is a need to further study the precursors, processes, and properties of SOA in laboratory experiments, and to develop more accurate SOA parameterizations that can be used to update the current CTMs. In Chapter 2, I studied SOA formation from several novel precursors which were vapors from biofuels that were under development at the National Renewable Energy Laboratory (NREL) to be used as future blendstocks to gasoline, and I developed SOA parameterizations for these biofuel precursors that corrected for the influence of vapor wall loss, using a kinetic SOA model called SOM-TOMAS (Statistical Oxidation Model coupled with TwO-Moment Aerosol Sectional Model). Although vapor wall loss has been shown to significantly impact SOA formation in environmental chamber experiments, it has rarely been corrected for in the development of SOA parameters used in atmospheric models. Our parameterizations predicted that under atmospherically relevant conditions, some of the biofuels may produce similar or even more SOA than gasoline, possibly offsetting the environmental benefits they offered. In addition, the parameterizations predicted that correcting for vapor wall loss in chambers always resulted in similar or increased atmospheric SOA mass yields compared to chamber yields, highlighting the potential for vapor wall loss correction to increase SOA predictions from CTMs and to bridge the gap with observations. In Chapter 3, I demonstrated a novel technique to constrain the SOA particle bulk diffusivity (Db) in chamber experiments, using a kinetic model (i.e., SOM-TOMAS) and measurements of the particle size distribution. Db is a property that controls the gas/particle partitioning timescale of SOA, where a higher Db (i.e., liquid aerosol) means faster partitioning and a lower Db (i.e., semi-solid aerosol) means slower partitioning. Here, I showed that the measured particle size distribution in SOA formation experiments contained sufficient information to constrain Db without direct measurement of the particle phase state or viscosity. In Chapter 4, I investigated the differences in the SOA mass yields measured in environmental chambers and oxidation flow reactors. Both chambers and flow reactors can simulate the photooxidation of Volatile Organic Compounds (VOCs), but flow reactors can achieve higher aging time (>2 weeks) than chambers (<1 day) by using very high oxidant concentrations. Their photooxidation chemistry pathways have been thought to be similar, but they produce different SOA mass yields at similar photochemical ages, which remains an unsolved problem. Here, I integrally simulated vapor and particle wall loss, semi-solid phase state, heterogeneous oxidation, particle-phase oligomerization, and new particle formation in chambers and flow reactors with experimentally constrained parameters for these processes. I showed that the SOA mass yield difference could be explained by the different contribution of these processes to SOA formation and evolution in chambers and flow reactors. Furthermore, with a single set of SOA parameterizations for photooxidation, the model was able to simultaneously predict the SOA mass concentration, bulk chemical composition (O:C ratio), and size distribution in chambers and flow reactors. The results highlight that flow reactor data can be modeled consistently with chamber data, and they should be used in synergy with chamber data to develop SOA parameterizations applicable to long photochemical aging times. In Chapter 5, in collaboration with Dr. Kelsey Bilsback, we investigated a widely employed assumption for particle wall loss correction in chamber experiments, regarding the interaction between wall-deposited particles and suspended vapors. Furthermore, as a continuation of the work from Chapter 2, we developed SOA parameterizations that corrected for both vapor and particle wall loss, and integrated these updated parameterizations into a CTM to assess the impacts on atmospheric SOA predictions. Specifically, we first showed that the interaction between vapors and wall-deposited particles was negligible through kinetic modeling, and accurate particle wall loss correction should assume no interaction between the two. We then found that the wall-loss-corrected SOA parameterizations greatly enhanced SOA formation in the CTM, reducing the gap with the observations. We argue that vapor and particle wall loss should be routinely accounted for in developing SOA parameterization.Item Open Access Impacts of unconventional oil and gas development on atmospheric aerosol particles(Colorado State University. Libraries, 2017) Evanoski-Cole, Ashley R., author; Collett, Jeffrey L., advisor; Kreidenweis, Sonia M., committee member; Pierce, Jeffrey R., committee member; Ham, Jay, committee memberRising demands for global energy production and shifts in the economics of fossil fuel production have recently driven rapid increases in unconventional oil and gas drilling operations in the United States. Limited field measurements of atmospheric aerosol particles have been conducted to understand the impacts of unconventional oil and gas extraction on air quality. These impacts can include emissions of greenhouse gases, the release of volatile organic compounds that can be hazardous and precursors to tropospheric ozone formation, and increases in atmospheric aerosol particles. Aerosol particles can also contribute to climate change, degrade visibility and negatively impact human health and the environment. Aerosol formation can result from a variety of activities associated with oil and gas drilling operations, including emission of particles and/or particle precursors such as nitrogen oxides from on-site power generation, evaporation or leaking of fracking fluids or the produced fuel, flaring, the generation of road dust, and increases in traffic and other anthropogenic emissions associated with growing populations near drilling locations. The work presented here details how activities associated with unconventional oil and gas extraction impact aerosol particle characteristics, sources, and formation in remote regions. An air quality field study was conducted in the Bakken formation region during a period of rapid growth in oil production by unconventional techniques over two winters in 2013 and 2014. The location and time of year were chosen because long term IMPROVE network monitoring records show an increasing trend in particulate nitrate concentrations and haze in the Bakken region during the winter, strongly contrasting with sharp decreases observed across most of the U.S. The comprehensive suite of instrumentation deployed for the Bakken Air Quality Study (BAQS) included measurements of aerosol concentrations, composition, and scattering, gaseous precursors important for aerosol formation, volatile organic compounds, and meteorology. Regional measurements of inorganic aerosol composition were collected, with average concentrations of total inorganic PM2.5 between 4.78 – 6.77 µg m-3 and 1.99 – 2.52 µg m-3 for all sampling sites during the 2013 and 2014 study periods, respectively. The maximum inorganic PM2.5 concentration observed was 21.3 µg m-3 for a 48 hour filter sample collected at Fort Union National Historical Site, a site located within a dense area of oil wells. Organic aerosol measurements obtained during the second study at the north unit of Theodore Roosevelt National Park (THRO-N) featured an average concentration of 1.1 ± 0.7 µg m-3. While oil production increased from 2013 to 2014, the lower PM2.5 in 2014 can be explained by the meteorological differences. During the first study, increased snow cover, atmospheric stability, solar illumination, and differences in the dominant wind direction contributed to higher PM2.5. The enhanced concentrations of inorganic PM2.5 measured in the Bakken region were tied to regional oil and gas development. Elevated concentrations of PM2.5 were observed during periods of air mass stagnation and recirculation and were associated with VOC emissions aged less than a day, both indicating a predominant influence from local emissions. High PM2.5 concentrations occurred when low i-/n-pentane VOC ratios were observed, indicating strong contributions from oil and gas operations. The hourly measurements of gas and aerosol species in an extremely cold environment also provided a unique data set to investigate how well thermodynamic aerosol models represent the partitioning of ammonium nitrate. In general, during the coldest temperatures, the models overpredicted the formation of particulate nitrate. The formation of additional PM2.5 in this region is more sensitive to availability of N(-III) species during the coldest periods but increasingly sensitive to available N(V) when temperatures are relatively warmer and ammonia availability increases. These measurements and modeling results show that continued growth of oil and gas drilling operations in remote areas such as the Bakken region could lead to increased PM2.5 and impact haze formation in nearby federally protected lands.Item Embargo Marine ice nucleating particles: sources, composition, emissions, and model parameterizations(Colorado State University. Libraries, 2023) Moore, Kathryn A., author; Kreidenweis, Sonia M., advisor; DeMott, Paul J., advisor; Farmer, Delphine K., committee member; Pierce, Jeffrey R., committee member; van den Heever, Susan C., committee memberSea spray aerosol has received increasing attention over the last decade as a source of ice nucleating particles (INPs) to the atmosphere. Sparse measurements in remote marine regions indicate both marine INP concentrations and ice nucleating efficiency are several orders of magnitude lower than those of mineral or soil dusts, which dominate the INP budget on a global scale. The Southern Ocean (SO) surrounding Antarctica is thought to be the only region where marine INPs are the predominant INP type due to its remoteness from continental and anthropogenic aerosol sources and persistent strong westerlies, although several recent studies have suggested this may also be true of the high Arctic seasonally or intermittently. INPs are critical for initiating cloud glaciation at temperatures warmer than ~-36 °C and can thus have an outsize effect on cloud phase and related climate feedbacks due to their relative scarcity. This is particularly true over the polar oceans, where low and mid-level mixed phase and supercooled clouds are ubiquitous and especially sensitive to aerosols due to the generally low background particle concentrations. The research presented here aimed to improve our understanding of the factors influencing marine INP emissions and the sources and composition of INPs in remote marine regions, as well as to evaluate and improve current INP model parameterizations. This was accomplished using observations made in the Southern Ocean, one of the few remaining pristine aerosol environments, during the Southern Ocean Cloud Radiation Aerosol Transport Experimental Study (SOCRATES) aircraft campaign on the NSF/NCAR G-V, and the second Clouds, Aerosols, Precipitation, Radiation and atmospherIc Composition Over the southeRN ocean (CAPRICORN-2) ship campaign on the R/V Investigator in 2018. Ambient observations were supplemented by measurements from the CHaracterizing Atmosphere-Ocean parameters in SOARS (CHAOS) mesocosm experiment in the new Scripps Ocean-Atmosphere Research Simulator (SOARS) wind-wave channel. CHAOS measurements allowed for isolation of the role of wind speed in marine INP production, which had not previously been characterized through controlled experiments. SOCRATES and CAPRICORN-2 are notable for collecting the first vertically resolved INP measurements over the Southern Ocean, including the first in situ observations in and above cloud in the region. Both aerosol and INP concentrations showed excellent agreement between G-V and R/V Investigator observations during overflights of the ship, supporting the use of such a multi-platform measurement approach for future campaigns interested in aerosol and INP vertical profiles. New techniques for estimating marine aerosol surface area and the number of particles >0.5 μm, key quantities often used in INP parameterizations, were developed based on lidar and nephelometer measurements. An additional parameterization for marine INPs is proposed, which uses both wind speed and activation temperature, and reduces bias compared to the existing parameterization based solely on temperature. Marine boundary layer (MBL) and above cloud INP concentrations from the same SOCRATES flight support the hypothesis suggested by several modeling studies that marine INPs dominate at low altitudes, and mineral dust becomes increasingly important with height. Unexpectedly, enhanced INP and aerosol iron concentrations, but low iron solubilities, were observed for samples collected south of 60 °S during CAPRICORN-2. Antarctica is suggested as a potential source of both biological and inorganic INPs to the Southern Ocean marine boundary layer through the emission of mineral and soil dusts from ice-free areas. Similar high latitude dust sources in Iceland and Svalbard have been observed to contribute to INPs in the Arctic atmosphere, and are anticipated to increase in importance as the climate warms.Item Open Access The simultaneous influence of thermodynamics and aerosols on deep convection and lightning(Colorado State University. Libraries, 2016) Stolz, Douglas C., author; Rutledge, Steven A., advisor; Pierce, Jeffrey R., committee member; van den Heever, Susan C., committee member; Reising, Steven C., committee memberThe dissertation consists of a multi-scale investigation of the relative contributions of thermodynamics and aerosols to the observed variability of deep convective clouds in the Tropics. First, estimates of thermodynamic quantities and cloud-condensation nuclei (CCN) in the environment are attributed to convective features (CFs) observed by the Tropical Rainfall Measuring Mission (TRMM) satellite for eight years (2004-2011) between 36⁰S-36⁰N across all longitudes. The collection of simultaneous observations was analyzed in order to assess the relevance of thermodynamic and aerosol hypotheses for explaining the spatial and temporal variability of the characteristics of deep convective clouds. Specifically, the impacts of normalized convective available potential energy (NCAPE) and warm cloud depth (WCD) as well as CCN concentrations (D ≥ 40 nm) on total lightning density (TLD), average height of 30 dBZ echoes (AVGHT30), and vertical profiles of radar reflectivity (VPRR) within individual CFs are the subject of initial curiosity. The results show that TLD increased by up to 600% and AVGHT30 increased by up to 2-3 km with increasing NCAPE and CCN for fixed WCD on the global scale. The partial sensitivity of TLD/AVGHT30 to NCAPE and CCN individually are found to be comparable in magnitude, but each independent variable accounts for a fraction of the total range of variability observed in the response (i.e., when the influences of NCAPE and CCN are considered simultaneously). Both TLD and AVGHT30 vary inversely with WCD such that maxima of TLD and AVGHT30 are found for the combination of high NCAPE, high CCN, and shallower WCD. The relationship between lightning and radar reflectivity is shown to vary as a function of CCN for a fixed thermodynamic environment. Analysis of VPRRs shows that reflectivity in the mixed phase region (altitudes where temperatures are between 0⁰C and -40⁰C) is up to 5.0-5.6 dB greater for CFs in polluted environments compared to CFs in pristine environments (holding thermodynamics fixed). A statistical decomposition of the relative contributions of NCAPE, CCN, and WCD to the variability of convective intensity proxies is undertaken. Simple linear models of TLD/AVGHT30 based on the predictor set composed of NCAPE, CCN, and WCD account for appreciable portions of the variability in convective intensity (R2 ≈ 0.3-0.8) over the global domain, continents, oceans, and select regions. Furthermore, the results from the statistical analysis suggest that the simultaneous contributions from NCAPE, CCN, and WCD to the variability of convective intensity are often comparable in magnitude. There was evidence for similar relationships over even finer-scale regions [O(106 km2)], but differences in the relative prognostic ability and stability of individual regression parameters between regions/seasons were apparent. These results highlight the need to investigate the connection between statistical behavior and local meteorological variability within individual regions. Following the global and regional analyses, data from Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign (2011-2012; central equatorial Indian Ocean (CIO)) and other sources was used to assess the relative impact of aerosols on deep convective clouds within a fine-scale environment with spatially homogeneous thermodynamics and variable aerosols in a pristine background over the CIO (CCN ~50-100 cm-3, on average; NCAPE and WCD are hypothesized to be approximately constant, spatially). The experiment was designed to compare differences in the convective cloud population developing in more-polluted and pristine regions, north and south of the equator, respectively. Analysis of the covariability of rainfall, cold cloud frequency, CCN, NCAPE, and lightning/radar reflectivity in deep convective clouds over multiple (> 20) episodes of the Madden-Julian Oscillation (MJO) leads to a hypothesis for a potential bi-directional interaction between aerosols and convective clouds that develop in association with the MJO. Close scrutiny of the results from climatology leads to the conclusion that thermodynamics and aerosols both influence deep convective cloud behavior over the CIO in a manner similar to that observed on the global scale, but the possibility that other factors are required to reproduce the full range of variability of deep convective clouds on fine-scales is acknowledged. The research presented in this dissertation constitutes one of the first efforts to link the documented variability of radar reflectivity and lightning within convective features observed by the TRMM satellite to their environment using novel representations of thermodynamic and aerosol quantities from reanalysis and a chemical transport model, respectively. The independent variables studied here (i.e., NCAPE, CCN, and WCD) were chosen specifically to address preeminent hypotheses in the literature and the results from this investigation suggest that NCAPE, CCN, and WCD each contribute significantly to the variability of deep convective clouds throughout the Tropics and Subtropics (and perhaps seasonally). Implications of the findings from the current investigations and the relevance of these results to future studies are discussed.Item Open Access Variability in observed remote marine aerosol populations and implications for haze and cloud formation(Colorado State University. Libraries, 2020) Atwood, Samuel A., author; Kreidenweis, Sonia M., advisor; van den Heever, Susan C., committee member; Pierce, Jeffrey R., committee member; Cooley, Daniel, committee memberIn many oceanic regions of the planet, once pristine environments are known to have a high degree of sensitivity to changing aerosol populations and perturbations from anthropogenic emissions. However, difficulties in modeling and remote sensing efforts in remote marine regions have led to continued uncertainties in aerosol-cloud-climate interactions. Numerous properties of the aerosol and environment affect these interactions in complex and often non-linear ways. In this work, I examine the variability in observed remote marine aerosol properties and its implications for classifying aerosol impacts on cloud development and radiative transfer in the atmosphere. The results from several field campaigns that measured aerosol and environmental properties relevant to these processes in marine and coastal regions are first presented. An unsupervised classification methodology was used to identify periods of impacts associated with distinct fine-mode aerosol population types and to quantify the observed range of variability associated with these types. A specific focus was placed on differentiating between internal variability in relevant properties within a given population type and external variability between the average values for each population type. The result was a set of aerosol population type models observed in marine regions that allowed for further investigation of the impact of different sources of variability on subsequent atmospheric processes. Next presented are the results of several observationally driven sensitivity studies using the aerosol models. First, initial cloud properties were investigated using a cloud parcel model driven by the observed aerosol population types to examine relative sensitivity to updraft velocity, extensive aerosol properties including number concentration, and a range of intensive aerosol properties. It was found that the parameter space across which initial cloud property sensitivity to variability in the observed aerosol dataset was investigated could be simplified to incorporate relevant intensive aerosol properties into a single population type parameter. Previous work using simpler mono-modal aerosol populations had identified several regimes of sensitivity of initial cloud properties to updraft velocity and total particle number concentration. When driven by the more complex and atmospherically relevant marine population types additional sensitivity to population type was identified through portions of these two regimes, and a new regime was identified that was more sensitive to population type than either of the other parameters. A Monte Carlo optical reconstruction model was then used to investigate sensitivity of atmospheric optical properties to observed variability in aerosol and environmental properties. As expected, aerosol dry mass concentrations were the largest contributors to overall sensitivity of extensive optical properties. However, in terms of intensive optical properties, the range of expected variability due to internal variability within a given population type was on the same order as impacts expected due to differences between population types. Specific aerosol population type models may therefore provide little advantage for further constraining expected optical property variability in this dataset. Additionally, the combined impacts of variability in environmental relative humidity (RH) and intensive aerosol properties within a nominally consistent population type could be quantified with coefficients of variation on the order of 0.3 in this dataset—a value that was relatively constant and independent of total mass concentration, aerosol population type, and RH. Overall, this work produced new representations of fine-mode aerosol types encountered in marine environments that were broadly consistent with those currently applied in remote sensing and climate modeling. However, the models presented here can account explicitly for the effects of ambient relative humidity, and thus may be useful for next-generation modeling that includes those effects. Future work focused on similar observationally-constrained model development for the marine and littoral coarse mode would be beneficial, as large particles are often significant fractions of optical depth in these regions.