Ocean Remote Sensing Group
Faculty Advisor: Henry Houskeeper, Woods Hole Oceanographic Institution
Introduced by Katherine Cavanaugh, University of California, Los Angeles
Satellite Evaluation of Oil Seepage Trends After the Decommission of Platform Holly
Annette Yang, University of California, Davis
Marine hydrocarbon seepage is a natural source of petroleum and methane pollution, affecting ocean chemistry, marine life health, and Earth’s atmosphere. One of the largest and most studied natural seepage zones is the Coal Oil Point seep field, located offshore from Coal Oil Point in the Santa Barbara Channel. Adjacent to the oil seeps sits Platform Holly, an offshore oil rig that took advantage of the natural oil field for 50 years until its decommission in 2015. Previous sonar studies identified a 50% reduction in seepage area near Holly from 1973 to 1995, suggesting that offshore oil production decreases seepage rates by alleviating pressure in oil and gas reservoirs. Potential changes in seepage rates related to the recent decommissioning of Platform Holly are presently unknown. While sonar is effective at detecting volumes of oil underwater, passive remote sensing through satellite imagery provides a larger and more accessible data source that can also be used to remotely detect oceanic macroseeps. The Landsat archive dates back to the 1980s and provides global coverage every 16 days at 30 m resolution. However, Landsat imagery lacks fine spatial and temporal resolution useful for capturing dynamic oil slick surface expression variability. A recent CubeSat constellation, PlanetScope, consists of 200 nano satellites that support 3 m resolution with near-daily global coverage, effective for detecting thin oil slicks in marine environments by leveraging sun glint. This study supports the further development and utilization of high resolution multispectral data to distinguish oil seepage from water, allowing us to quantify seep size and flux.
Landsat Mission Reveals Nearly 50 Years of New Zealand Giant Kelp Forest Dynamics
Rylie Mundell, University of Denver
Giant kelp (Macrocystis pyrifera) plays a foundational role in supporting both ocean and beach ecosystems. Inhabiting a quarter of the world’s coastlines, the spatial extent of kelp populations contributes to their importance as an ecosystem engineer. However, this quality also creates obstacles for monitoring and management, especially over long time periods.
Fortunately, floating giant kelp canopies are easily identifiable using satellite remote sensing.
The historical continuity of the Landsat program serves an important role in remote observations of kelp dating as far back as 1972. Recently, the Kelpwatch web browser was developed to provide an interactive platform that hosts Landsat-based kelp canopy maps, which have been completed for some regions of the world. Despite widespread data availability and the existence of Kelpwatch, many global regions still have not been mapped. For example, the coast of Otago, New Zealand, lacks the multi-decadal assessment afforded by Landsat. A recent anecdotal study of Otago documented kelp bed disappearance in the late 1970s. Landsat imagery dating from as early as 1977 confirms the anecdotal accounts of historical kelp forest beds not observed in recent decades. Additionally, we expanded the geographic extent of global kelp forest observations by incorporating Landsat 4, 5, 7, and 8 imagery to support future research investigating kelp stressors and aid in the development of kelp conservation for the Otago region.
Understanding the Drivers of Kelp Growth at Fine Temporal Resolution
Sophia Brieler, Tulane University
Giant kelp forests are highly dynamic with high spatial coverage and therefore difficult to monitor on adequate spatial scales with existing field methods. However, airborne and satellite remote sensors like NASA’s next generation airborne visible/infrared imaging spectrometer (AVIRIS-ng), present opportunities to explore kelp population dynamics using imagery with high spatial and spectral resolution. Previous studies have demonstrated that spectral data can be used to determine the chlorophyll a to carbon ratio (Chl:C), an indicator of kelp growth associated with health and environmental factors. Here I use weekly AVIRIS-ng observations obtained during the SHIFT campaign from February through May 2022 within the Santa Barbara channel. AVIRIS-ng observations enable assessment of ecological patterns at finer scales than supported by satellite imagery. AVIRIS-ng data was used to quantify Chl:C, canopy biomass, and canopy fraction, a measurement for the fraction of the pixel made up of kelp canopy. Time series of all three variables indicate positive correlations with light and highlight high variability in Chl:C throughout the season. Additionally, nitrate availability has been previously identified as the primary driver of regional kelp growth in the Santa Barbara Channel but this dataset indicates that light availability has a greater correlation to both Chl:C and biomass. This glimpse into how the relationships between kelp and external drivers vary on fine time scales indicates that greater coverage over time and area of hyperspectral data would contribute to better understanding the dynamics of kelp populations. Understanding drivers of kelp growth and mortality could provide an opportunity to respond to these dynamics in real time.
Comparing the status of micro- and macro-algal populations in Monterey Bay, CA following the 2014-2016 marine heatwave
Odai Natsheh, University of Texas at San Antonio
The eastern boundary of the North Pacific constitutes a major coastal upwelling system, the California Current System (CCS), that provides upwelled nutrients to fuel production for both kelp and phytoplankton. In Monterey Bay, a marine sanctuary within the CCS, phytoplankton and kelp dynamics are controlled, in part, by the availability of nitrogen. Seasonal changes in the alongshore intensity of southward winds drive a ‘spring transition’ to upwelling conditions, which provide nutrient-rich water that support algal growth. From 2014-2016, the west coast of North America experienced an unprecedented, multi-year marine heatwave (MHW), which coincided with increased Sea Surface Temperature (SST) and decreased nutrients. As a result, kelp populations in the Monterey region drastically declined, with low population densities persisting. The sustained decline of kelp canopy after the end of the heatwave in 2016 – compared to apparent resistance of phytoplankton – was assessed by evaluating SST and chlorophyll a concentration data products. SST and chlorophyll a concentrations are obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Aqua satellite. Regional scale drivers of kelp declines may have included a lack of nutrients in the Monterey region. Here, results indicate that kelp populations in Santa Cruz and Monterey displayed strong seasonal variability, where the highest kelp canopy areas tended to occur in the spring and summer seasons when nitrate concentrations were low. Chlorophyll a concentrations displayed weak correlations with nitrate. No seasonal pattern was observed, as high and low concentrations were present during each season. High SST anomalies during the MHW coincided with a decline in nitrate in both Santa Cruz and Monterey. However, nitrate and chlorophyll a concentrations both increased to near-historical levels following the MHW, suggesting that inadequate nitrate availability was likely not a primary driver of persistent, low kelp canopy area in the years following the MHW.
Detecting Jellyfish Aggregations in the Puget Sound with PlanetScope CubeSats
Joseph Dale, University of Northern Colorado
Assessing global variability in jellyfish populations, e.g., due to overfishing of jellyfish competitors, ocean acidification, eutrophication, and basin-scale climate oscillations is presently challenged by observing capabilities for monitoring jellyfish stocks. Presently, methods include primarily in situ approaches such as plankton nets, diving, and visual observations, which confer low spatiotemporal coverage that is inadequate to resolve drivers of population dynamics and evaluate potential trends. To increase spatial coverage, aerial surveys support spatially resolved jellyfish observations with moderate coverage. Additional improvements in coverage and temporal resolution for airborne surveys are limited by high expense. An alternate approach, uncrewed aerial vehicles (UAVs) mitigate financial restrictions but confer separate technological and logistical limitations. Although not widely leveraged for monitoring jellyfish stocks, recent satellite technological advances provide potentially useful advantages. A recent CubeSat constellation, PlanetScope, supports 3m spatial resolution and a global 30 hour median average revisit frequency, thereby conferring high spatiotemporal resolution and expansive spatial coverage. In this study, jellyfish aggregations were found by pairing aerial photographs of jellyfish obtained via “Eyes Over Puget Sound” with PlanetScope’s satellite imagery. Results document large aggregations of jellyfish are detectable using existing PlanetScope satellite infrastructure, and that jellyfish aggregations have spectral signals that are unique from water. Future work will test whether jellyfish targets are discernable from other aquatic targets such as sediment plumes, algal blooms, and fish spawning.
Evaluating Aquatic Applications for the NASA EMIT Instrument Using the Tijuana River Estuary as a Case Study
Sierra Whiteman, Stony Brook University
Untreated wastewater and stormwater runoff in the Tijuana River Estuary (TRE) introduce pollutants including sediments, nutrients, and bacteria into the surrounding ocean. As a result, runoff causes major water quality issues and poses a hazard to human health in Southern California. Multispectral satellite remote sensing observations have been used to distinguish spectral characteristics, turbidity, and sea surface temperature between surfacing plumes of water pollution. One recent multispectral study utilized Landsat 8, Sentinel-2 A/B, and Rapideye satellite data, along with in situ data, to characterize plumes exiting the TRE into adjacent ocean environments. The newly launched NASA Earth Surface Mineral Dust Source Investigation (EMIT) instrument aims to determine mineral signatures and soil composition over the Earth’s surface and provides hyperspectral (8nm resolution) remote sensing observations spanning 380-2500nm. Here, we leverage observations of the TRE obtained by EMIT and evaluate potential opportunities to determine the turbidity of TRE wastewater and stormwater runoff. Initial results demonstrate that EMIT data products of bright aquatic targets (e.g., sediment plume) capture broad gradients in turbidity. Using a combination of multispectral and newly developed hyperspectral neural network algorithms, we assessed turbidity data products and evaluated potential performance enhancements supported by increased spectral range and resolution of aquatic data products. Preliminary results have shown that the hyperspectral mixture density network (MDN) produced improved turbidity estimates compared to multispectral estimates based on nearby in situ data. Further evaluations of aquatic applications for the EMIT instrument would advance understanding of hyperspectral satellite remote sensing relevant to future NASA hyperspectral oceanographic instruments including GLIMR and PACE.
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Atmospheric Aerosols
Faculty Advisor: Dr. Andreas Beyersdorf, California State University-San Bernardino
Introduced by Ariana Deegan, University of Georgia
Tracking the Progression of DMS Oxidation over the Central ValleyTricia Hutton, SUNY Brockport
During the marine sulfur cycle, dimethyl sulfide (DMS) produced from phytoplankton oxidizes to form sulfur dioxide (SO2) and methane sulfonic acid (MSA). In 2017, a third oxidation product of DMS, hydroperoxy methylthioformate (HPMTF), was observed in the atmosphere for the first time. This new sulfur molecule raised questions regarding the understanding of the marine sulfur cycle. Understanding the formation and fate of marine sulfur is important as these gas phase products can go on to form aerosol particles, which can have implications on climate, visibility, and human health. Aerosols in the atmosphere influence the formation of clouds, which can have an effect on Earth’s radiation budget. Investigations into the aging of marine sulfur species and their influence on aerosol-cloud interactions may help to decrease uncertainty in climate models. Instruments from the NASA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) campaign during the Student Airborne Research Program (SARP) confirmed high concentrations of DMS, HPMTF, and SO2 in California’s Central Valley on June 26th, 2023. Initially, a DMS hotspot was observed near Sacramento with an average concentration of 0.135 parts per billion (ppb). Using outputs from the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) forward trajectory models, northwest winds were observed. Downwind of the DMS hotspot, an HPMTF hotspot was found near Fresno with an average concentration of 0.027 ppb. Similarly, an SO2 hotspot was found downwind near Bakersfield with an average concentration of 2.616 ppb. This research examines the progression of DMS oxidation of aerosol cloud properties in this urban area. Since there is large uncertainty in the interaction between aerosols and cloud formation, the evolution of the gas phase marine sulfur is also examined in conjunction with cloud condensation nuclei (CCN) and sea salt fraction. The findings of this research will help increase the understanding of the newly updated marine sulfur cycle and potentially highlight the implications aerosols have on cloud formation.
Impact of the Recurrence of Tulare Lake on Local Atmospheric Composition
Patrick Djerf, Carleton College
Once with a greater surface area than Lake Tahoe, Tulare Lake in California’s Central Valley has been mostly empty for over a century, after its water was diverted for agricultural and municipal use. However, Tulare Lake has reemerged after several atmospheric river events brought a historic level of precipitation to California in early 2023. Marine bodies can significantly impact the chemistry of the atmosphere by emitting trace gases and aerosols, which can modulate the climate, alter visibility, affect human health, and modify biogeochemical cycles. This study investigates how aerosol data can be used to classify the composition of the Tulare Lake atmosphere as compared to those surrounding other marine bodies, such as the Salton Sea and the Pacific Ocean. Land-based environments, including the agricultural Central Valley region and urban Los Angeles area, were also investigated. Airborne measurements collected during the combined 2023 NASA Student Airborne Research Program (SARP) and NOAA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) campaign were used to observe the difference in aerosol and gas phase composition using a Particle Analysis by Laser Mass Spectrometry (PALMS) instrument and Proton Transfer Reaction-Mass Spectrometer (PTR-MS), respectively. With the increase in lake surface area, the atmosphere over Tulare Lake is expected to begin more closely resembling that of a marine environment. As climate change continues to impact weather patterns and cause more extreme weather events, the Tulare Lake case study provides insight into how extreme weather can impact local environments, and in turn, how these changes are impacting atmospheric aerosol composition.
Investigating the Impact of Particulate Ammonium on Surface Water Eutrophication
Emily Rademacher, University of Minnesota
California’s Central Valley (CV) is known for its poor air quality conditions largely due to agricultural and industrial pollution sources. Ammonia (NH3) is a gas-phase agricultural emission that can react with other gas-phase species to form aerosols such as ammonium nitrate and ammonium sulfate. These ammonium-containing aerosols have the potential to deposit onto soils and surface water bodies, potentially increasing available nutrients and leading to excess algae growth. This overgrowth of algae causes a depletion of dissolved oxygen; a condition better known as eutrophication. This study focuses on the transport of ammonium from particulate matter with diameters ≤ 1 micron (PM1) from the San Joaquin Valley (SJV) to a cluster of lakes on the western edge of the Sierra Nevada Mountain Range. Summer months are highlighted in this study because pollution can be more readily transported due to higher planetary boundary layer heights (PBLH) that result from increased atmospheric mixing. The lakes near the Sierra Nevada Mountain Range are expected to be impacted by SJV emissions due to summer weather patterns, such as northwest winds, which would transport emissions from the valley eastward into the mountains. The airborne aerosol datasets utilized in this study are from the NASA Student Airborne Research Program (SARP) flights from 2016 and 2019 and the Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) payload from 2023. Particle phase ammonium concentrations measured by the Aerosol Mass Spectrometer (AMS) are analyzed for emission hotspots in the San Joaquin Valley. Remote sensing data from SENTINEL-3 is used to calculate the chlorophyll-a abundance of the lake ecosystems, which will indicate the extent of eutrophication in the lakes. Analysis is expected to show a proportional relationship between ammonium concentrations and chlorophyll-a abundance. This study will help increase our understanding of how agricultural aerosol emissions influence adjacent biological ecosystems.
Investigation of Aging on the Radiative Properties of Aerosols in Los Angeles
Maria Vabson, Johns Hopkins University
The Los Angeles (LA) skyline is often hazy, filled with particulate aerosols. The major sources of pollution are vehicle traffic, industrial processes, and forest fires. Aerosols have numerous implications, such as reducing visibility, influencing Earth’s radiation budget, and affecting human health. There is high uncertainty regarding the cooling effect of aerosols in the atmosphere and whether this can be attributed to the direct or indirect effect of aerosols. Most aerosols contribute to the direct effect by reflecting radiation. Some darker colored particles, like black carbon from combustion, typically absorb more radiation, enhancing the greenhouse effect. Additionally, aerosols can act as cloud condensation nuclei (CCN), particles that water droplets and clouds form upon with the necessary humidity. Clouds also reflect light, which is known as the indirect effect. To better understand the radiative properties of atmospheric aerosols on LA, the optical and physical properties of aerosols were studied as they aged over the course of a day. Data from the morning and afternoon flights on June 27th for the 2023 NOAA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) campaign during the NASA Student Airborne Research Program (SARP) was analyzed. Initial results show increasing aerosol size, hygroscopicity, extinction, absorption, and CCN concentration throughout the day. However, the proportion of CCN to the total number of particles decreases, meaning while more aerosols are present, fewer have the potential to form clouds. With an increase in absorption, more of the aerosols could potentially contribute to atmospheric warming. This study investigates the progression of aerosol aging and why it is crucial to monitor emissions, even with improving precautions.
Effect of Atmospheric Aerosols on The Imperial Valley Radiation Budget
Julia Alvarez, University of Texas at Arlington
The Salton Sea is an endorheic, high-salinity lake in Southern California with water levels that have rapidly declined in recent years. New dust emissions from the exposed playa and polluted soil from agricultural runoff have been resuspended into the air surrounding the Imperial Valley. These aerosols have a strong impact on Earth’s incoming and outgoing radiation budget, often causing a cooling effect via scattering in the troposphere. This research focuses on the integrated study of aerosol size and composition in correlation to the Imperial Valley’s radiative forcing. Data was collected from the 2023 NASA Student Airborne Research Program (SARP) under the Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) campaign. Featured instruments include the Single Particle Analysis by Laser Mass Spectrometry – New Generation (PALMS-NG) for composition and Aerosol Optical Properties (AOP) for absorption and extinction data. Radiative forcing efficiency and backscatter calculations were carried out in Python using Mie Theory; utilizing constants obtained from the Langley Aerosol Research Group Experiment (LARGE). A concurrent analysis of size distribution and particle composition for urban, biomass, soot, dust, and sea salt aerosols were used to identify the type that has the heaviest influence on the Imperial Valley climate. Biomass particles from agricultural practices such as land clearing and waste incineration were shown to significantly influence the Imperial Valley climate. Although dust and salt fractions were found to be substantially lower influencers on radiative forcing, this model likely underestimates the importance of their effects on radiative scattering. By better understanding the contribution of aerosols to the Imperial Valley’s radiative budget, preventative measures can be taken to monitor and potentially reduce these emissions. As different elements absorb different wavelengths, future work involves investigating how mineralogical variations relate to scattering and absorption in regions that experience high dust and salt concentrations.
Vertical Distribution of Saharan Dust during the CPEX-CV Campaign
Sarothi Ghosh, University of Florida
Dust from the Sahara is regularly lofted into the atmosphere and transported across the Atlantic Ocean as part of the Saharan Air Layer. This aerosol layer has a number of impacts on the planet, such as suppression of tropical cyclone development, fertilization of downstream ecosystems, and changes to radiative forcing. To fully understand the effects of Saharan dust, it is crucial to know its vertical distribution in the atmosphere. Prior research has extensively investigated the climatological distribution of Saharan dust, as well as examined case studies of dust plumes as they traverse the Atlantic. However, interactions near meteorological phenomena, such as tropical cyclones, are more complex. NASA’s 2022 Convective Processes Experiment – Cabo Verde (CPEX-CV) airborne campaign offers a chance to study the vertical distribution of dust. This research aims to characterize the vertical distribution of Saharan dust in the tropical eastern Atlantic during CPEX-CV. To accomplish this, data are mainly sourced from the High Altitude Lidar Observatory (HALO) instrument that deployed during CPEX-CV. We determine vertical distribution from backscatter profiles, and aerosol composition from aerosol ID and dust mixing ratio. Broader meteorological context is provided by dropsondes and satellite data. Results show that dust distribution for the overall campaign, including a specific outbreak from September 15-16, follows the established understanding of Saharan dust vertical distribution: much of the dust is observed in the mid-troposphere, while a significant amount of dust, possibly mixed with marine aerosol, is also observed in the mixed layer of the troposphere. Further research will focus on the vertical distribution of dust around Tropical Storm Hermine, which formed during the CPEX-CV campaign and was studied during one flight. A case study of this event, utilizing detailed information from the CPEX-CV flight and satellite data, will improve our understanding of interactions between dust and tropical cyclones.
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Whole Air Sampling Group (WAS)
Faculty Advisor: Dr. Don Blake, University of California, Irvine
Introduced by Katherine Hopstock, University of California Irvine
NASA SARP Airborne Data Suggests California Airports as Sources for Halon 1211 and Halon 1301
DJ Viray, Drexel University
Anthropogenic emissions of volatile organic compounds (VOCs), such as halocarbons, may have unintended negative consequences on the global climate. Halons, such as bromochlorodifluoromethane (H-1211) and bromotrifluoromethane (H-1301), are a class of halocarbons that are effective at extinguishing fires through a combination of cooling and inhibition of the combustion chain reaction. They are also “clean agents,” meaning that they leave no residue after use, and non-corrosive, which makes them attractive in industries such as the military, aviation, and healthcare, where damage to essential equipment should be minimized. While these brominated compounds have desirable fire extinguishing properties, they also have high global warming potentials, long atmospheric lifetimes, and high stratospheric ozone-depletion potentials, which has led to restrictions on their production and usage. The goal of this study is to use airborne data to gain insight into the emission trends of H-1211 and H-1301 in California. Using 2009-2022 whole air sampling (WAS) data from the NASA Student Airborne Research Program (SARP), enhanced emissions of H-1211 and H-1301 were observed near airports in Southern and Central California. 130 ppt of H-1211 was observed near Los Angeles International Airport in 2016, whereas the global mean background concentration was ~3.5 ppt. In addition, 93 ppt of H-1301 was observed near the Joint Forces Training Base in 2014, whereas the global mean background concentration was ~3.3 ppt. Emission hotspots of H-1211 and H-1301 and possible reasons for these observations will be explored, helping to positively influence regulation and policy on the usage of these halons.
Geothermal VOC Emissions in the Imperial Valley: Health and Air Quality Implications
Alexandria Savagian, Bowdoin College
Benzene and toluene are carcinogenic volatile organic compounds (VOCs) known to be emitted from a variety of sources, including coal and oil combustion, wildfires, mud volcanoes (or mud pots), and geothermal plants. In 2022, NASA Student Airborne Research Program (SARP) interns conducted whole air sampling (WAS) field work at natural mud pots in Calipatria, CA, near the Salton Sea. These preliminary mud pot samples yielded surprising concentrations of benzene and toluene, which were orders of magnitude above background. While studies of benzene and toluene near mud pots have been carried out in Indonesia and Italy, such research has not occurred in the United States and the relationship between geothermal plants and mud pots has not been previously explored. The goal of this work is to characterize mud pot emissions, determine emission connections to nearby geothermal plants, and understand the environmental justice implications of mud pot emissions in the Imperial Valley. In 2023, NASA SARP interns returned to the Imperial Valley and collected WAS samples at the mouths of the natural mud pots. WAS gas chromatography results showed that benzene and toluene concentrations were up to one million times that of the measured background. Transport of these emissions was visualized using the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT). NASA Socioeconomic Data and Applications Center’s (SEDAC) Social Vulnerability Index data for the Imperial Valley was utilized to understand the impact of mud pot emissions on nearby communities. Of the variety of trajectories modeled, airmasses delivered mud pot plumes directly toward the nearby towns of Niland and Calipatria, which are indexed as some of the most socially vulnerable communities in the US. Results from this work suggest that more attention to air quality surrounding Calipatria’s mud pots is needed, and that similar monitoring should occur at the Imperial Valley’s geothermal plants.
Kinetic Evaluations of Sulfur Dioxide over the Salton Sea and Pacific Ocean
Christine Harper, Bowling Green State University
Dimethyl sulfide (DMS), commonly emitted from phytoplankton, is a known precursor to secondary sulfur dioxide (SO2). SO2 plays important roles in the atmosphere regarding cloud optical properties, as the presence of sulfur can cause an increase in the reflectance leading to localized cooling and global climate impacts. Additionally, SO2 is crucial in the concentration of atmospheric sulfuric acid, as SO2 can react to form sulfuric acid. Determining the role of temperature on SO2 formation in aquatic environments is vital to better understand atmospheric sulfur cycles and climate change impacts. In this study, rate coefficients from NASA’s Jet Propulsion Laboratory Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling (1997) were used to determine the relationship between temperature and the rate of the DMS oxidation reactions with OH, NO3, and free chlorine. DMS and SO2 measurements from the NASA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) and NASA Student Airborne Research Program (SARP) flights over the Salton Sea and portions of the Pacific Ocean were obtained from a Laser Induced Florescence SO2 (LIF-SO2) instrument and a Proton-Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS), respectively. Analysis of the rate coefficients with respect to temperature and the observed flight data showed that the observed concentration of SO2 over the Salton Sea cannot solely be attributed to DMS oxidation. Kinetic evaluations determined that additional sulfur sources, such as dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS), from the Salton Sea contribute to larger SO2 concentrations than over the Pacific Ocean. Whole air samples collected on the ground at the Salton Sea support this, as significant concentrations of DMDS and DMTS were observed. Further investigations of the sources of sulfur, as well as the temperature dependence on oxidation rates, is necessary to comprehend the cycle of sulfur in the atmosphere.
The Human-Made Forest: How Isoprene Emissions Vary Based on Tree Populations in Urban Southern California
Summer Coleman, University of Colorado, Boulder
Isoprene (C5H8) is a biogenic volatile organic compound (BVOC) that is emitted by plants and trees at an estimated 350 million tons per year. It is produced as a direct by-product of photosynthesis and emission rates increase exponentially with increases in light and temperature. Urban greenspaces place trees directly in the presence of high anthropogenic emissions (NOx and elevated OH) not naturally found in forested areas. Due to the highly volatile and reactive nature of isoprene, it quickly forms ozone with urban emissions. High concentrations of ozone have negative impacts on human health including inflammation of human airways, which makes the lungs more susceptible to infection and aggravates existing respiratory conditions. Despite the health risks involved, an in situ approach has never been used to examine isoprene output from urban trees. To obtain this information, tree population densities in urban regions from southern California counties Ventura, Los Angeles, Orange, San Bernardino, and Riverside were mapped. Trees included were the most populous within these regions, including: the Red Gum Eucalyptus, Blue Gum Eucalyptus, Engelmann Oak, Coast Live Oak, Desert Willow, Carrotwood, and California Fan Palm. Isoprene whole air sampling (WAS) measurements from 2009-2022 NASA Student Airborne Research Program (SARP) flights were examined in the regions overlapping with known tree populations. Airborne isoprene concentrations were examined against tree species population density and all tree species reported contradictory high levels of isoprene in areas of low tree population density. This skewed result is due to the lack of correlation between flight altitudes and tree population density. This implies that an airborne approach is unfavorable to generate a taxonomic breakdown of isoprene emissions. This information will guide future research of the topic, allowing chemists to formulate datasets which quantify isoprene more effectively.
Using Supervised Machine Learning and HYSPLIT Backwards Trajectories to Predict Airborne VOC Concentrations
Victor Geiser – Saint Louis University
Algorithms for supervised machine learning are growing more accessible to research and the predictive power they offer have important scientific implications. The use of machine learning in predicting volatile organic compound (VOC) concentrations in whole air sampling (WAS) has not previously been explored. The model created in this study was initialized with trajectory data generated using the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) integrated with the Global Data Assimilation System (GDAS) to calculate meteorological variables along a 24 hour backwards trajectory path. The endpoints of these trajectories were then treated as inputs to train this model using the Random Forest Regression algorithm provided by the Python module Scikit-Learn. The goal of this study is to predict the airborne concentrations of selected VOCs: dimethyl sulfide (DMS), methane, benzene, toluene, isoprene, ethane, and Halon 1301. These concentrations were compared against the gas chromatography results from WAS data collected by NASA Student Airborne Research Program (SARP) flights from 2009 to 2022. It was found that the Random Forest Regression model created for this study can predict the concentrations of the selected VOCs with R2 values of 0.71 (DMS), 0.62 (methane), 0.47 (ethane), 0.37 (benzene), 0.38 (toluene), 0.24 (isoprene), and 0.16 (Halon 1301). These results predict airborne DMS and methane concentrations with fair confidence based on the initial model parameters. The concentrations of benzene, toluene, isoprene, ethane, and halon-1301 can be evaluated using the same process, but with a larger degree of uncertainty. These results, in combination with analysis of model sensitivity and performance, yield consistent trends regarding known properties governing the locality of VOC concentrations and lifetime in the atmosphere. The model created in this study can be applied and modified in future works to predict other VOC concentrations using different time scales, longer backwards trajectories, and higher resolution meteorological data.
The Importance of Ground, Airborne, and Satellite Data for Field Campaigns: A Case Study of Ammonia and Dimethyl Sulfide in the Central Valley
Andrew Bower, PennWest California University
Ammonia and dimethyl sulfide (DMS) emissions contribute to the formation of secondary organic aerosol (SOA), which can impact human health, air quality, and climate. Livestock manure and other agricultural processes are the largest source of primary ammonia emissions, while DMS is a gaseous product of livestock manure and slurry decomposition under aerobic or anaerobic conditions. Measurements of DMS and ammonia are constrained due to limitations of satellite capabilities and ground sampling strategies, respectively. Additionally, comparison of ammonia measurements from satellites and in situ observations on or near the ground remain under-investigated. In this study, agricultural ammonia and DMS emissions were quantified and compared using alternative measurement techniques, while highlighting the importance and limitations of remote and in situ data sampling. Ammonia columns from the Infrared Atmospheric Sounding Interferometer (IASI) satellite were compared to boundary layer ammonia measurements from the Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) above agricultural ammonia hotspots in the Central Valley. Boundary layer DMS concentrations from the Proton Transfer Reaction Mass Spectrometer (PTR-MS) were compared to whole air sampling (WAS) canister data collected on the ground at the Tipton, CA manure pile. Airborne data obtained from the QC-TILDAS and PTR-MS were collected onboard the NASA DC-8 on June 26th, 2023, during the combined NASA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) and NASA Student Airborne Research Program (SARP) field campaign. DMS measurements from the flight compared well with ground-level WAS results. Additionally, IASI ammonia concentrations aligned with flight data away from intense agricultural sources, whereas hotspot locations (Tipton and Harris Feeding Company) lacked agreement. Results of this study highlight the limitations associated with satellite and ground sampling techniques of ammonia and DMS, while providing insight into measurement comparison from the ground to space.
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Terrestrial Ecology
Faculty Mentor: Dr. Dan Sousa, San Diego State University
Introduced by Jean Allen, University of California, Santa Barbara
Quantifying Healthy Vegetation Dynamics in Southern California After a Record 2023 Wet Season
Ethan Greeley, University of Richmond
After a record-breaking wet season in Southern California at the beginning of 2023, caused by a series of atmospheric rivers, the diverse vegetation of the region experienced unusually high levels of productivity. Various studies have suggested that an abundance of photosynthetically active vegetation reduces wildfire risk. However, the impacts of this year’s increased precipitation has not yet been adequately quantified across different land cover types in the state’s rural landscape. This project aims to compare the magnitudes of phenological green-ups between dry years over the past decade and this recent historic wet year, to explore differential effects of these atmospheric river events on different ecosystems. Vegetation change was assessed using the Normalized Difference Vegetation Index (NDVI) calculated from the Landsat 8 time series from 2013-2023 for three regions of interest (ROIs), including agricultural, semi-arid, and riparian lands across Southern California. Agricultural and semi-arid land were found to experience the largest relative increases in healthy vegetation in response to the record rainfall event, whereas riparian areas exhibited only subtle differences. To explore the interplay between healthy and senesced vegetation across the study area and over time, we performed a spectral mixture analysis (SMA) for a pair of hyperspectral images taken by EMIT, a new NASA imaging spectrometer, captured in summer 2022 and 2023, respectively. Using SMA, green vegetation fraction (GVF), non-photosynthetic vegetation fraction (NPVF), and soil fraction (SF) were calculated for an agriculturally rural region west of Bakersfield. In this time period, SF significantly declined while NPVF increased across both natural and manmade land cover types, indicating significant greening during the winter but a potentially quick die-off in response to the summer dry season. This build-up of dry vegetation raises the risk for severe wildfires within California and the Western U.S.
Assessing Heat Stress in Oak Trees Using Airborne Thermal Spectroscopy
Duncan Jurayj, Brown University
Increasingly severe and frequent drought conditions in Southern California subject
semi-arid ecosystems to unprecedented levels of thermal and hydrologic stress. To cope with this stress, trees can reduce canopy temperatures through evaporative cooling to avoid thermal damage; however, this places additional demand on the tree’s already limited water supply and increases the risk of hydraulic damage. In the oak savannas of the Santa Ynez Valley, California, it is unclear how well oak trees will respond to increasing thermal stress and water scarcity. Optical and thermal imaging spectroscopy enables spatially continuous measurements of canopy properties that are linked to water scarcity and thermal stress. This data can help us understand the observed variability in levels of thermal stress among oak trees when paired with in-situ measurements such as species, leaf area index, and leaf water potential. Tree canopy temperature and surface emissivity, derived from the Hyperspectral Thermal Infrared
Spectrometer (HyTES), was compared to a variety of potential contributing variables, including slope and aspect, and in situ measurements of soil water status and midday evaporative demand. Interestingly, soil water status was inversely related to canopy temperature. The inverse relationship between soil water and canopy temperature could be the result of structural overshoot during the 2022 drought in Southern California. Trees with more soil water may have developed larger canopies and experienced greater evaporative water losses, leading to more thermal stress. Surface emissivity was a stronger predictor of soil water status than land surface temperature, highlighting the potential of emissivity data products in studying hydrologic and thermal stress in oak trees.
Sudden Oak Death and its Forecasted Threat to California Oaks
Tierney Cantwell, Gettysburg College
The pathogen Phytophthora ramorum has significantly impacted oak populations within the state of California. P. ramorum, commonly known as Sudden Oak Death (SOD), can cause nonlethal foliar and twig damage in some species, while causing lethal twig and stem cankers in others. It is currently understood that the extent of SOD’s distribution is heavily controlled by climatic factors. As such it is expected that the change to earth’s climate factors, such as temperature and precipitation, will affect the distribution of SOD. However, as oak species ranges are also likely to change in response to increasing temperatures and aridity, it remains unclear how climate change will affect the threat posed by P. ramorum in future decades. Quercus douglassi (Blue Oak), Quercus agrifolia (Coast Live Oak), and Quercus kelloggii (California Black Oak) were modeled and compared to the current species distribution of SOD in CA to predict the future distribution of both species order to determine the risk to future oak populations. The current and future species distributions of SOD and three oak species were modeled using a Maximum Entropy model (maxent) using RCP scenario 4.5 in the year 2070. Maxent was fed occurrence data from the Global Biodiversity Information Facility (GBIF), and utilized the CMIP5 dataset for its climate model. The results show that SOD and each individual oak species responds to different amounts and types of bioclimatic variables and thus their projected future change in distribution is expected to correlate with the change in climate factors. SOD distribution responded most strongly to climate factors relating to both temperature and precipitation. However, the oak species were most accurately modeled through climate factors related solely to precipitation. The results further intend to suggest that significant co-occurrence is expected for Coast Live Oak and the California Black Oak. Predicted co-occurrence of oak species and SOD should be considered when working to understand the changing terrestrial ecology of California because of the pathogen’s negative impact on economically and historically important species. Expected co-occurrence should be further monitored due to its relevance to conservation efforts in managing species under multifaceted pressures.
Revisiting Rewilding at Atwell Island using Hyperspectral Images
Eva Coleman, Denison University
The Atwell Island Restoration Project in the San Joaquin Valley in California is an experimental site of rewilded agricultural land that was used to test the effects of clearing practices, tillage, and seeding methods on native species recovery. While rewilding progress was closely monitored in the decade following the initial restoration effort in 2000, there has not been a large-scale analysis on rewilding success since 2010. Imaging spectroscopy offers a low-cost method to continuously monitor ecosystem health. Fortunately, several years of historical airborne spectroscopic data was collected over Atwell island by NASA’s Airborne Visible InfraRed Imaging Spectrometer (AVIRIS). Here, we assess vegetation health for plots with different rewilding treatments in Atwell Island throughout and following the historic 2014-2017 drought using three metrics: the lignin cellulose absorption index (LCAI), the normalized difference vegetation index (NDVI), and green vegetation fraction (GVF) from spectral mixture analysis. PlanetScope EVI2 time series was additionally used to characterize vegetation phenology. While fire-cleared land had marginally better growth from 2014 to 2017 (p=0.02), indicating that prescribed burns may aid in regeneration over long time scales, tillage and seeding methods had little discernible effect on plot success. Spectral diversity for each plot was also assessed by quantifying spatial variance in NDVI and GVF. On average, all plots exhibited a decline in spectral diversity from 2014-2022. However, burned plots lost less spectral diversity than unburned plots, suggesting that burning fallow land has a potential positive impact on habitat resilience. Taken together, these results provide useful context for planning restoration outcomes for future fallowed land in the San Joaquin Valley.
Refining Spectral and Spatial Resolution through Spectroscopic Analysis in the El Paso Mountains
Ivan Tochimani-Hernandez, Dartmouth College
The El Paso Mountains in Inyo County, California, exhibit a complex geological history characterized by metamorphism and geologic displacement. The region acts as an alluvial basin controlled by the Garlock fault with a left-lateral movement. The site continuously experiences sedimentation, volcanic activity, tectonic events, and metamorphism, resulting in a diverse array of geologic formations composed of a variety of rock types and structural features. Utilizing hyperspectral data collected by the Airborne Visible/Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) I evaluate spectroscopic variability within and among mapped geologic units. Computational analysis of the airborne data reveals lithological and mineralogical variations between and within units. The analysis complements existing maps of geological structures and their relationships by providing additional models of the separation between lithology. Spectral separability analysis of reflectance spectra from mapped geologic units reveals a range of transformed divergence and Jeffries-Matusita scores. Spectral separability was highest (TD = 1.999) for discriminating the meta-argillite and Greenstone units composed of metamorphosed basalt breccia. Units with similar lithologies score lower values (TD = 1.943) displaying strong similarities in spectral features such as those in the meta-argillite members of the Robbers Mountain Formation. These results reveal how airborne imaging spectroscopy can complement traditional geologic mapping, satellite multispectral imagery, and lab observations in planning, collecting, and interpreting geologic data, providing valuable insights into the geological processes and composition of inaccessible regions of interest.
Differential Drought Impacts on Green Space Across Different Income Areas in Los Angeles, California
Miriam Bartleson, University of Michigan
Access to green space in urban areas contributes positively to human health, with documented benefits such as reducing risks of psychiatric disorders, as well as reducing heat exposure by contributing to urban heat island mitigation through evapotranspirative cooling. However, in many urban areas, low-income communities have less access to green space than high-income communities, which could explain differential health outcomes such as higher heat exposure in lower income communities. In California, this problem may be exacerbated by increasingly severe and frequent drought conditions that may have different effects on green spaces in different communities. This study mapped green space across Los Angeles and compared the impacts of the 2012-2016 drought on green space in different income areas. Urban green space was mapped using imagery captured by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and calculating green vegetation fraction (GVF) with Multiple Endmember Spectral Mixture Analysis (MESMA). Income data was retrieved from the 2010 US census. We confirmed an unequal distribution of green space across Los Angeles for the duration of the drought, finding GVF to be highest in high-income areas such as Bel Air and Glendale and lowest in low-income areas such as downtown Los Angeles and Westmont. While GVF was found to decline throughout the drought in nearly all of Los Angeles, low- and middle- income areas were more severely impacted, with greater reduced GVF by percent on average. This suggests that green space resiliency acts within a threshold, where high-income areas are better able to maintain green space during droughts, potentially due to differences in recreational water access.
