Current Visiting Fellows
A critical assessment of fine particulate matter in ambient air and associated toxicological impact over urban coastal regions in tropical and temperate zones
A rise in industrialization and modern living practices have immensely contributed to a wide range of complex pollutants into the atmosphere, many of which are unexplored. Although we have gathered important information about their role in atmospheric chemistry and their climate implications, uncertainties pertaining to their diverse primary and secondary emissions sources, composition, and health impacts are high. We have a long way to go to establish solid links that would lead to identify ways to curb/control/diversify these pollutants in the atmosphere. Therefore, In Prof. Joost de Gouws’s group, Trupti will study the inorganic and organic composition of ambient aerosols (particulate matter <2.5µm dimeter). There will be simultaneous observations in the Indian tropics and the temperate zones of the USA, having different socio-economic standards and health challenges etc. We plan to compare the characteristics and effects of PM2.5 pollution in two urban coastal locations; one situated on the Eastern coast of the Indian Sub-continent and the other in the West coast of the United States of America. PM2.5 is capable of triggering free radical formation thus generating oxidative stress in vivo in the respiratory system including other potential organs through translocation by the blood stream. Therefore, the evaluation of specific components, which has the potential of generating maximum reactive oxygen species (ROS), would help establish a possible link between exposure to specific components in PM2.5 and their adverse health risks.
Using observations of a “natural” experiment to constrain the sensitivity of clouds to pollution and global warming in climate models
Summary: Clouds confound our understanding of how human activities are changing our climate system. The cooling effect of interactions between small airborne pollution particles (aerosol) and clouds has “masked” some of the warming from increasing greenhouse gas concentrations. Unknowns about how much such masking has already occurred and about how clouds will respond to warming make it difficult to estimate future climate changes. A major factor that complicates the study of aerosol-cloud interactions is the challenge of disentangling aerosol effects on cloud properties from other weather-related changes. "Natural experiments," in which there is a known aerosol change that is independent of the weather, offer a promising framework for improving our understanding of causation in aerosol-cloud relationships. Michael Diamond will work with Graham Feingold and Jen Kay to study one such natural experiment: a highly-trafficked shipping corridor in the southeast Atlantic in which cloud brightening from pollution effects has been observed. I will use a hierarchy of models to determine whether biases in simulated cloud changes are related to aerosol effects on how much clouds precipitate or how much dry air is mixed into the cloudy layer by turbulent motions. These processes are key to understanding how clouds respond to both pollution and global warming.
Turbulent fluxes in the atmospheric boundary layer over Arctic sea-ice during MOSAiC
Ulrike will work with John Cassano and Matt Shupe on analyzing turbulent energy fluxes in the Arctic cloudy atmospheric boundary layer (ABL). Turbulent fluxes constitute a major part of the atmospheric energy budget and influence the surface heat balance by distributing energy vertically in the atmosphere. However, only few in-situ measurements exist of the vertical profile of turbulent fluxes in the Arctic ABL, especially under cloudy conditions. The project is based on measurements with an uncrewed aerial vehicle (UAV) during the field campaign MOSAiC in the central Arctic ocean during the sea-ice melt season 2020. First, a suitable method will be elaborated to derive turbulent fluxes from the UAV turbulence measurements. Second, the resulting vertical profiles of turbulent fluxes will be analyzed concerning different ABL and sea-ice conditions, including the influence of atmospheric stability, stratification, clouds, leads, and melt ponds. This study will help to advance our understanding of how the turbulent fluxes influence the surface energy budget and interact with the melting sea ice.
The role of the 'cloud twilight zone' in Earth's energy budget
Clouds play a dominant role in Earth's energy budget as they cover more than half of the globe and strongly interact with both solar and terrestrial radiation. Nevertheless, they are poorly understood and represented in models and hence cause high uncertainty in climate prediction. The study of clouds’ processes by remote sensing and quantification of their radiative effects are based on a binary separation between clouds and clear skies that contain aerosol particles. This separation is ambiguous in practice as humidified aerosols continuously grow to become cloud droplets by condensation of water vapor. Moreover, the radiative signal of aerosols and cloud droplets has been shown to overlap and was named the “cloud twilight zone” (CTZ). Eshkol Eytan will work with Graham Feingold, Jake Gristey, Jennifer Kay, and Rainer Volkamer. The studies will use modeling and remote sensing data to quantify the effects of the CTZ on the global energy budget and to study the contribution of different processes to the total CTZ radiative effect. This will help to advance our understanding of clouds’ role in the energy budget and improve remote sensing areas that are neighboring clouds.
Resiliency of Arctic Infrastructure – Strategies to Adapt in a Rapidly Changing Environment
The Arctic has been warming at twice the global rate since the 1980s, known as the Arctic Amplification. Due to climate warming, the Earth is undergoing rapid changes in all cryospheric components, and Arctic infrastructures are crumbling under thawing permafrost. Thian Yew Gan will work with Mark Serreze on a project to investigate environmental changes taking place in the Arctic and the impacts they are having on the built environment of coastal and inland Arctic communities. They will evaluate strategic management and development options to increase the resiliency of Arctic Infrastructure in a rapidly changing environment, and mitigation measures effective for the Arctic communities to adapt to the impact of rapid loss of Arctic sea ice to the Arctic climate system, changes in atmospheric and ocean circulations, Arctic hydrologic processes, and societal costs, and to identify knowledge gaps regarding changes in freshwater resources, catchments and rivers and the impact on societies and peoples of the northern communities.
Understanding climate impacts of a changing Pacific
Ulla will work with Kris Karnauskas and Ben Livneh on understanding climate impacts from large scale changes in ocean and atmospheric circulation with particular focus on changes in the tropical Pacific and climate impacts in the Americas. Recent observations have revealed a multi-decadal strengthening of the Walker circulation in the tropical Pacific, yet climate models robustly predict a weakening of the Walker cell emerging in the 21st century. How such a potential future reversal of the Walker cell trend will impact society through changes to regional hydrology, fire susceptibility, and extreme events is, however, largely unknown, which poses a big challenge for adaptation and mitigation strategies. Through a hierarchy of modelling experiments, this project aims to address this knowledge gap by developing a framework which traces the effect of large-scale circulation changes on societally relevant climate impacts. An additional component of the project, in collaboration with Anne Gold, is to present outcomes of this research in education and outreach in communities affected by climate change impacts across Colorado.
Automatically quantifying the development of retrogressive thaw slumps in northern Alaska
Lingcao Huang will work with Kevin Schaefer, Kristy Tiampo, and Michael Willis on a project using machine learning to automatically quantify the development of retrogressive thaw slumps (RTS) whose formation is due to the thawing the ice-rich permafrost. Retrogressive thaw slumps are the most dynamic landforms in cold regions and in which thaw of ice-rich permafrost on slopes causes mass-wasting of soil and vegetation. As reported by many local studies, their number and affected areas have increased dramatically in recent decades. However, their spatial distribution as well as development are poorly quantified and understood because they are widespread but localized features. By applying machine learning technology, especially, deep learning, Lingcao will develop a method to delineate and quantify RTS occurrence and dynamics in northern Alaska. The objectives are to provide a tool to monitor RTS dynamics in larger areas and also advance the understanding of permafrost degradation in northern Alaska related to external controlling factors such as climatic variables.
Characterization of enzymes in a newly evolved microbial metabolic pathway that can mineralize the toxic pesticide pentachlorophenol (PCP)
Anthropogenic compounds such as pesticides, textile dyes, solvents, explosives, and pharmaceuticals can persist in the environment for years and cause toxicity to humans and wildlife. Pentachlorophenol (PCP) is a highly toxic pesticide in use since the 1930s. It is designated as a priority pollutant by the US EPA. Interestingly, environmental microbes have evolved new metabolic pathways for degradation of some of these chemicals. Evolution begins with promiscuous activities of enzymes that normally serve other functions. These enzymes assemble in a patchwork fashion to catalyze the conversion of the pollutants into metabolites that can be utilized by other existing metabolic networks. The bacterium Sphingobium chlorophenolicum, which was isolated from PCP-contaminated sediment, has a newly evolved pathway for the degradation of PCP. The purpose of this study is to elucidate mechanistic details of this pathway. Our focus will be on a tandem of enzymes that enable the process. The proposed questions will be addressed using site directed mutagenesis, kinetic assays, and electron paramagnetic resonance (EPR) spectroscopy. The data obtained will quantitatively demonstrate how the pathway evolved, how highly reactive intermediates in the pathway are sequestered for protection, and how a toxic contaminant can be converted to a nutrient for the bacterium.
Building political coalitions for climate mitigation through economic opportunity: a model of household opinion and migration
Mitigating the consequences of climate change and reducing political polarization are two of the biggest problems facing society today. These problems are intertwined, since meeting international climate-mitigation targets requires implementing policies that accelerate the rate of decarbonization, and these policies can succeed only with widespread bipartisan support. Ekaterina will work with Matt Burgess to provide a road map for how to build momentum for climate action and counteract polarization around climate policies. She will study this problem through the lens of economic opportunity and migration in the United States. While concerns about the cost of decarbonizing and job loss in the fossil fuel energy sector have been barriers to clean energy policies, recent forecasts show that the transition to clean energy could be cheaper and faster than previously thought. The economic opportunity created by the low cost of clean energy is interwoven with the patterns of state-to-state migration in the U.S., which is often driven by economic factors. The goal of the project is to evaluate how the geographic siting of renewable energy projects can affect political support for climate change mitigation.
Drivers of Pacific Decadal Variability and its changing impacts in a warming world
Nicola Maher will work with Jen Kay and Antonietta Capotondi to investigate what drives Pacific Decadal Variability and how this variability and its impacts are projected to change under varying levels of global warming. The far reaching impacts of Pacific Decadal Variability mean that it is highly relevant under a changing climate to investigate these questions. Previously it was difficult to investigate the decadal variability under a changing climate due to the low sampling of decadal modes in both climate models and observations. By using a new set of large-ensembles, where there is enough data to investigate the decadal variability and by combining new deep learning techniques with other more traditional analyses this research project aims to further the understanding of the mechanisms that drive IPO phase transitions, and how extreme events are modulated by the IPO around the globe under different levels of global warming.
Using Distributed Acoustic Sensing to Monitor Induced Seismicity and Evaluate Seismic Hazard in Paradox Valley, Colorado
Deep injection of wastewater fluid associated with oil and gas production is known to be responsible for the triggering of earthquakes near dense population centers. This practice increases the seismic hazard for regions that are typically devoid of earthquakes and poses a risk to buildings and critical structures where appropriate safety measures are deficient. To address this, I will work with Anne Sheehan and Ge Jin (CSM) in utilizing a novel seismological technique known as distributed acoustic sensing (DAS), in Paradox Valley, Colorado, to improve our understanding of induced seismicity where conventional seismic networks may be insufficient or absent. DAS operates by using an opto-electronic system that emits pulses of light down a fiber optic cable and records naturally backscattered energy returning from varying segments. In essence, this instrument acts as a dense and mechanically flexible seismic array that consists of multitudinous broadband sensors sensitive enough to detect tiny subsurface strain events in high fidelity. We aim to exploit the capabilities of DAS to identify key features missed by the surrounding (yet sparse) network of seismometers in Paradox Valley; features that can offer more detailed and accurate information on the evolution of faults and stress transfer mechanisms that drive the induced seismicity phenomenon.
Aerosols in Earth’s atmosphere vary widely in size, composition, and other properties. These characteristics evolve as aerosols are exposed to sunlight, temperature fluctuations, changes in humidity, and collisions with other particles. This project will contribute to a molecular-level and particle-level understanding of reactions of organic acids and their effects on aqueous aerosol particles. The common organic acids pyruvic acid, lactic acid, and their long-chain analogues will be studied in aqueous environments. Rebecca will collaborate with Veronica Vaida to elucidate reaction pathways and surface activity of the acids. She will work with Maggie Tolbert to observe reactions and particle properties of individually levitated microdroplets. These laboratory experiments will contribute to a detailed picture of aerosols in Earth’s environment, the refinement of regional and global atmospheric models, and potentially reduce the uncertainty from aerosols in climate models.
Interactions between tectonics, erosion, climate during Late Cenozoic global cooling and Northern Hemisphere glaciation
Yani Najman will work with Peter Molnar to understand interactions between tectonics, erosion and climate during the onset of Late Cenozoic global cooling and Northern Hemisphere glaciation. The degree of interaction between these entities is debated, in part because the records are incomplete and difficult to disentangle. For example, is the Late Cenozoic proposed increase in global erosion rates the result of a change to a cooler, less equable, perhaps stormier climate, or the result of mountain ranges rising, or simply the result of an incomplete record of sediment accumulation? Moreover, the feedbacks between these variables are multifaceted: erosion affects climate both by increasing silicate weathering which causes drawdown of atmospheric CO2, and because higher sedimentation rates result in faster burial of organic carbon; growth of mountain belts impacts climate by interfering with atmospheric circulation patterns; and the influence of isostasy moderates these variables. Understanding the complex interlinkages and feedbacks requires a knowledge of the precise timing of events. This project will undertake a new approach to interrogating these records, utilising a compilation of low temperature thermochronology data to seek to determine the level of temporal correlation between such events.
Leveraging multi-mission satellites to assess the impacts of recent storage changes in global lakes and reservoirs on sea level change and land surface modeling
Fangfang Yao is working with Ben Livneh and Balaji Rajagopalan to improve the understanding of recent global changes in surface water storage. Surface water provides easily accessible water resources for human beings. Spatial and temporal variations of surface water storage not only affect local water supply, but also have implications for the hydrological cycle. Despite its importance, changes in open surface water (especially lakes and reservoirs) are not simulated by existing land surface models due to the challenges of modeling human impacts including damming and water withdrawal. Partially owing to this, land surface models have large uncertainties in estimating both seasonality and long-term trends of terrestrial water storage (TWS; the summation of surface water, soil moisture, groundwater, snow and ice). In this context, Fangfang proposes to investigate global surface water storage dynamics and the impacts on the hydrological cycle using a combination of satellite observations and land surface models. He aims to answer two science questions: i) how global open-surface water has contributed to the recent sea level change, and ii) how an improved observation of open-surface water changes can further benefit the modeling of other terrestrial water components (such as soil moisture and groundwater). These questions are essential to the understanding of terrestrial water cycle and the closure of global sea level budget.
Using Reanalysis and MOSAiC’s Field Campaign to Explore the Role of Arctic Cyclone on Arctic Atmospheric Rivers and Their Associated Sea Ice Effects
Atmospheric rivers (AR) are one conspicuous pathway for poleward moisture transport from lower latitudes. They have been known to influence Arctic warming and sea ice decline in the boreal winter. Likewise, cyclones play an important role in the Arctic climate: Arctic cyclones strongly interact with the diminishing sea ice. While over the Arctic, the dynamic and physical process of how Arctic cyclones influence ARs and the associated sea ice effects are still missing in the literature. Thus, Chen Zhang will work with Profs. John Cassano, Mark Serreze, and Matthew Shupe use reanalysis and MOSAiC data to provide a comprehensive dynamic/thermodynamic analysis to quantify the influence of Arctic cyclones’ dominant physical factors on ARs and the associated sea ice evolution via the subsequent surface radiative budgets. Such physical understanding will lead to improved cyclone and AR predictions in the changing climate and bridge a knowledge gap in Arctic amplification.