Fire hazard maps are important for promoting the safety of homeowners and firefighters and providing useful information to policymakers. In 2008, the California Department of Forestry and Fire Protection (CAL FIRE) created a fire hazard map for the state. This map considered broad variables of fire hazard such as weather patterns, slope and fuel levels. On July 6th, 2018 the Holiday Fire occurred on the Wildland Urban Interface (WUI) of Goleta, California burning over 40 hectares including 28 structures. However, CAL FIRE’s 2008 map did not identify Goleta as having high fire hazard. In this study, I created a fire risk assessment of Goleta using Airborne Visible / Infrared Imaging Spectrometer (AVIRIS) data taken 16 days prior to the Holiday Fire with 6.5m resolution. I built a spectral library that was optimized using Iterative Endmember Selection (IES). I then used Multiple Endmember Spectral Mixture Analysis (MESMA) to map land cover and classify the area into low, medium and high areas of risk. Areas of low fire risk were mapped around roads and soil. Areas of medium fire risk were mapped around green vegetation (GV). High levels of fire risk were mapped around non-photosynthetic vegetation (NPV). The Holiday Fire parcels showed high levels of fire risk. Medium regional values of fire risk were found north of the WUI while low values were found to the south. This study shows that highly specific and valid assessments can be developed around fire risk using a multifaceted remote sensing approach.

Understanding the dynamics of a watershed is critical for estimating ground water change, stream flow, and ocean runoff. The amount of runoff occurring in a system is highly correlated with the surface properties of the watershed because different surfaces have different infiltration capacities. Impervious surfaces do not allow any infiltration and therefore increase runoff. Urban impervious surfaces, such as pavement, are well studied and understood, however, less attention has been given to the natural impervious surfaces such as exposed rock. We predict that given a consistent rainfall rate, more natural impervious surfaces such as exposed rock, would correlate to more overall runoff in a watershed. In addition, accurate maps of exposed rock are rarely produced and not often used in hydrological models. In this study, we used Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS NG) data collected in 2014 to map exposed rock in the Santa Barbara front range. We implemented Multiple Endmember Spectral Mixture Analysis (MESMA) to compute fractional cover of rock, soil, green vegetation (GV), and non-photosynthetic vegetation (NPV). We then used Long Term Ecological Research (LTER) watershed data for precipitation, discharge rates, slope, and area of each watershed within our study site and compared the LTER to our impervious surface fractions. We found a positive correlation between impervious surface cover and runoff rates per watershed. We speculate that there are other parameters such as green vegetation cover, and slope that may also affect runoff rates in a given watershed.

California is subject to numerous wildfires every year, and recently the fire season has been increasing. In December of 2017, the Thomas Fire burned over 114,078 hectares and destroyed 1,063 structures while claiming 15 lives. In order to understand the dynamics of these fires, we need to study fire movement on a day-to-day basis.  One of the unique qualities about the Thomas Fire was that multiple sensors, both satellite and airborne, were used to take measurements of the fire. In this project, I set out to map the fire front of the Thomas Fire using Airborne Visible / Infrared Imaging Spectrometer (AVIRIS) at a 16.5-m resolution , the Operational Land Imager (OLI) at 30-m resolution, and the Moderate Resolution Imaging Spectroradiometer (MODIS) which has 1-km resolution in the thermal infrared. All 3 of my sensors have different temporal resolution. MODIS had daily measurements, OLI had 16-day and AVIRIS which has variable sampling. I created an active fire product for both AVIRIS and Landsat-OLI and used NASA’s active fire product for MODIS. I compared the active fire product for AVIRIS on December 6th and 7th, Landsat OLI on December 9th and 25th to MODIS on the same dates. MODIS overestimated the maximum area of the fire by over 600% when compared to both Landsat-OLI and AVIRIS. However, the temporal resolution of MODIS allowed us to track the fire movement every day. This shows that we need a combination of high spatial and high temporal resolution sensors to accurately map fire fronts.

Hot spots are characteristics of a fire in which multiple subsequent ignitions are present ahead of the primary fireline. This can increase the fires burn rate, ignite fires in locations the fire would not have naturally traversed, and seriously complicate firefighting efforts. Our objective was to study this phenomenon and evaluate potential factors promoting spotting, including wind conditions and fuel type. We manually mapped hot spots using the Airborne Visual/Infrared Imaging Spectrometer (AVIRIS) data acquired during the Thomas Fire with the hyper-spectral fire detection index (HFDI) and a radiance threshold in the short-wave infrared (SWIR). These hot spot locations were combined with a land cover classification model built from LANDSAT data to determine the associated fuel types, and wind data from local weather stations were plotted and analyzed as well. Our results conclude that wind conditions, rather than fuel types, are the primary indicators of hot spot probability in our study area.

The Thomas Fire in the winter of 2017-2018 was the largest wildfire in California history. As wildfires have become more common in recent years, it is important to better understand the impact that these fires have on the environment, and to gain an understanding of how well the environment can recover after disturbance by wildfire. This study aims to assess the partial recovery of an area that burned in the Thomas Fire and determine whether the amount of recovery has any correlation with burn severity or dominant plant type in an area. Data from  before the fire (June 26, 2017), immediately after the fire (December 21, 2017), and then six months later (June 20, 2018) were used to study the change in vegetation cover as a result of the fire and environmental recovery. Images of the study area were taken with the Airborne Visual/Infrared Imaging Spectrometer (AVIRIS). The land cover and green vegetation fractions before and after the fire were modeled using Multiple Endmember Spectral Mixture Analysis (MESMA). Burn severity was calculated using Difference Normalized Burn Ratio (dNBR). Fractional cover change was used to analyze the amount of recovery that had taken place in the six months following the fire. For the pre-fire data set, the vegetation cover was classified into chaparral, trees, and grassland and burn severity and recovery were analyzed in the context of dominant plant type in an area.  Analysis of the data shows grassland has the highest amount of recovery in the six months following the fire and lowest burn severity. In contrast, areas of chaparral and oak woodland had higher burn severities and lower recovery amounts, although recovery did take place in those areas.

Wildfires are one of the most destructive and common threats to people and property in Southern California. An important attribute of wildfires is the fuel available. Knowing the amount of fuel present helps predict fire intensity and post fire recovery. Since fires burn organic matter, measuring biomass can be an effective way to know the potential fuel available. Remote sensing can be used to estimate biomass values over a large region and aid in understanding wildfire and its potential destruction. To study the feasibility of remotely measuring biomass for wildfires, we used Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data from before and after the 2017 Thomas Fire in Santa Barbara and Ventura counties, CA. The pre-fire image was classified into Chaparral, Oak Woodland, Senesced (non-photosynthetic) Grassland, and Soil classes using a 2-endmember spectral mixture analysis (SMA). Known biomass values for each class were drawn from literature. The Normalized Difference Vegetative Index (NDVI), Normalized Differenced Water Index (NDWI), and Water Band Index (WBI) were calculated for the pre- and post-fire imagery. Linear regression was then used to create models based on each index for estimating biomass. Burn severity was also estimated using the differenced Normalized Burn Ratio (dNBR). The results of the NDVI analysis showed that an estimated 88% of biomass within the study area was lost due to the fire. The NDWI and WBI analyses, however, estimated a 26%-35% loss and a gain of 80%-100% after the fire, respectively. Since much of the study area had high burn severity, the results for NDWI and WBI indicate that these are likely poor indices for estimating biomass. We also found that the dNBR did not correlate well with amount of biomass lost. Further study needs to be done to confirm the accuracy of remotely sensed biomass estimates as well as the most effective index for measuring biomass loss after fires.

The recent Thomas Fire in December 2017 was the largest wildfire in modern California history, burning over 114,000 hectares in Santa Barbara and Ventura counties before it was fully contained in January 2018. On January 9th, 2018, a cold front moved over Montecito, CA and dropped a record 18.54 mm of rain in 15 minutes which initiated massive debris flows that led to the loss of 23 lives and over $421 million in property damage. In order to better understand the factors that created these destructive flows, we utilized Airborne Visual/Infrared Imaging Spectrometer (AVIRIS) data from two days: a December 21, 2017 post-fire pre-debris flow image and a January 11, 2018 post-debris flow image, both covering the Montecito area. We used Multiple End Member Spectral Analysis (MESMA) to determine, on a sub-pixel level, the fractional cover of soil, ash, rock, green vegetation, and non-photosynthetic vegetation in the images. Fractional cover of ash calculated from MESMA was used to quantify burn severity in the December image. To estimate debris flow severity, a change detection was calculated on the soil fractional cover between the December and January images. An increase in soil fraction between the two images was used as a proxy for the mass movement of soil/mud, and this was successfully used to map multiple tracks of the debris flows. We then compared the burn severity, debris flow severity, watershed characteristics, and precipitation in Montecito to adjacent watersheds in Summerland/Carpenteria (where debris flows were less severe). The Montecito watersheds showed greater burn severity, greater ash fractional cover, greater 5-minute precipitation levels, and greater percent area of the watershed burned, pointing towards these variables as potential factors in determining the occurrence and severity of post-fire debris flows in the Santa Barbara County area.

The boundary layer height separates turbulently mixed air and pollutants emitted at the ground from the free troposphere above and is an important parameter in numerical weather prediction. Discerning the boundary layer height over mountainous terrain is difficult due to complex interactions with upper level winds, venting of humidity and aerosols into the free troposphere, and large spatiotemporal variability. Mountain boundary layers can closely follow the terrain, be flat, or be shallower than valleys below depending on the time of day, season, and synoptic conditions. To determine the extent to which the boundary layer height follows terrain, I used aircraft meteorological and trace gas data collected onboard the NASA DC-8 during accents and descents over mountains across Central and Southern California. Meteorological parameters considered include water vapor, potential temperature, and turbulence. Carbon monoxide, methane, and carbon dioxide enhancement ratios were used to consider when observed atmospheric layers were last in contact with the ground surface. Vertical profiles over the southern Sierra Nevada, San Emigdio, and San Bernardino Mountains indicate that boundary layer heights closely follow the topography of these areas, being higher over ridges and lower over valleys.

Global climate change may alter the magnitude and dynamics of energy fluxes between the surface and atmosphere. The airborne eddy-covariance technique gives an opportunity to observe surface energy fluxes over large regions and in locations without established research towers. To increase observational constraints on the surface energy balance, I derive sensible and latent heat fluxes using the airborne eddy-covariance technique over two different land cover types in the San Joaquin Valley of California, a large agricultural area and the city of Bakersfield, and in the late morning and afternoon. I use aircraft observations of 3-D winds, temperature, and water at 20Hz, 10Hz, and 1Hz, respectively, collected onboard the NASA DC-8 and interpret observed differences in the surface energy budget as a function of location and time of day.

In California’s San Joaquin Valley, anthropogenic sources of long-lived greenhouse gases (CO2, CH4, and N2O) are various, distributed, and, consequently, difficult to distinguish. Due to the region’s complex land use, sources from livestock operations, farming, oil extraction, and urban traffic are all co-located on spatial scales of tens of kilometers. This study aims to understand the contribution of several source types have on atmospheric composition. Sources can be identified through enhancements ratios, as they emit distinct ratios of these long-lived greenhouse gases and other pollutants. Using in-situ airborne data from the NASA DC-8 aircraft, I identify enhancement ratios for agriculture, urban traffic sources, and biomass burning and adapt a multivariate mixing model to quantify the contributions of these sources along the DC-8 flight track. I then use HYSPLIT backward dispersion trajectories to calculate dilution factors over known source areas to augment the spatial resolution of my apportionment.

Nitrous oxide (N2O) is a long-lived greenhouse gas with a global warming potential almost 300 times that of carbon dioxide and the dominant destroyer of stratospheric ozone. While the free troposphere concentration of N2O is well-constrained, there are large uncertainties in both the identity of N2O sources and in controls over variability in these sources. N2O emissions are particularly difficult to quantify because of their high spatiotemporal heterogeneity, with sources often characterized as hotspots and/or hot moments. Because of this variability, it has proven difficult to upscale research conducted using chamber measurements, which gather information at meter to tens of meter spatial scales. Aircraft data are useful because they provide insight into N2O sources on kilometer spatial scales. I use data collected onboard the NASA DC-8 to look at spatial patterns in N2O concentrations and its agricultural sources over the California San Joaquin Valley, a place of dense agricultural activities including crop cultivation, feedlots, and dairies. I correlate measured N2O concentrations with methane (CH4) and feedlot and dairy location to determine relationships between N2O and cattle operations and discuss factors driving the observed correlations.

Formaldehyde (CH2O) plays an important part role in atmospheric oxidation chemistry, including the production of the harmful air pollutant tropospheric ozone (O3). O3 production is driven by the oxidation of numerous different gaseous organic compounds, most of which will at some point be oxidized to CH2O. Because the total concentration and composition of gaseous organic compounds is often unknown, CH2O provides valuable insight into O3 production rates. In this study, I use airborne CH2O data collected from onboard the NASA DC-8 over the city of Bakersfield, California, one of the most O3-polluted cities in the U.S. I observationally derive the CH2O production rates using changes in CH2O along upwind to downwind transects across the Bakersfield urban plume. Comparisons of morning and afternoon transects, as well as data at four different altitudes (500m, 800m, 1200m, and 1800m) are also used. I link inferred CH2O production rates to O3 production over this area.

Ozone (O3) air pollution is harmful to human health, affecting rates and exacerbation of respiratory diseases, hospital admissions, and mortality. O3 health impacts are predicted to worsen, as O3 production in Central and Southern California is temperature-dependent and global climate change is projected to increase regional temperatures. Simultaneously, as California’s population ages, residents become more vulnerable to respiratory diseases. Understanding how O3 affects mortality is critical to effectively shaping pollution control policies. Aircraft data is valuable in such assessments as it provides high spatial resolution data necessary for evaluating impacts below the county level. Using airborne data collected on the NASA C-23 Sherpa in 2017, I examine the potential health effects due to changes in O3 exposure and age in Central and Southern California using the EPA’s Environmental Benefits Mapping and Analysis Program (BenMAP). First, I model future mortality as a result of a 5 ppb increase in O3 concentrations and an artificially-aged population. Second, I decrease high O3 concentrations with the artificially-aged population to the World Health Organization recommendation of 50 ppb to simulate the results of a policy change on mortality incidence.

Tropospheric ozone (O3) is a harmful pollutant regulated by the U.S. Environmental Protection Agency. O3 is formed by complex chemical reactions that involve sunlight, volatile organic compounds (VOCs), and nitrogen oxides (NOx). O3 formation is non-linear and O3 chemistry within a region can be classified as either NOx– or VOC-limited. In NOx-limited regions, reductions in NOx lead to reductions in O3. In VOC-limited regions, reductions in NOx lead to increases in O3. Therefore, to effectively regulate O3, it is important to know whether local O3 chemistry is NOx or VOC sensitive. Formaldehyde (HCHO) is a short-lived oxidation product of many VOCs, making it a useful indicator of total VOC reactivity. The ratio of HCHO to NO2 is an accurate indicator of O3 sensitivity to NOx and VOCs. Low ratios suggest VOC-limited areas and high ratios suggest NOx-limited areas. Trees remove O3 and NOx by uptake through their leaf stomata and by reactions on surface waxes. In order to reduce O3 pollution, tree planting in urban and surrounding areas may be effective, but also has the potential to worsen O3 pollution as trees emit O3-forming VOCs. In this study, I use aircraft and ground-based data to examine the local variability of the HCHO to NO2 ratio over Bakersfield, California. The HCHO to NO2 ratio and wind patterns are used to determine the location of a NOx-limited region downwind of Bakersfield optimal for tree planting. I then quantify NO2 and O3 reductions for low, moderate, and high tree planting scenarios based on percentages of suitable land cover within this NOx-limited region. My work suggests that the HCHO to NO2 ratio can play a key role in urban forestry planning and associated land management decisions, especially in regions with O3 pollution problems.

While field surveys and aerial imagery can provide detailed biological data, satellite remote sensing enables consistent, long-term imagery over a large spatial scale. Such imagery enables us to track changes in vegetation over time, monitoring how environmental conditions have affected ecosystems. Long-term time series from satellite imagery have been developed for giant kelp in Southern California, but there have been no such surveys for bull kelp. Bull kelp is a Northern California brown algae species that supports fisheries and provides a habitat for keystone species. Decreases in bull kelp canopy cover are believed to result from warm waters, low nutrient levels, and intense storms, conditions typically associated with El Niño Southern Oscillation (ENSO). Using Multiple Endmember Spectral Mixture Analysis (MESMA) of Landsat imagery, we test bull kelp classification methods using California Department of Fish and Wildlife (CDFW) aerial bull kelp surveys for validation. Of MESMA models using 30, 19, 7, and 3 seawater endmembers, we find that the 7-endmember model records the lowest Root-Mean-Square Error (0.2352; 3.69%) during CDFW validation. Using the 7-endmember model on Landsat imagery, we construct a 36-year time series of bull kelp canopy coverage in Northern California. Canopy reductions and recovery are compared to ENSO and other basin-scale oscillations. We find that bull kelp decreased sharply during historical strong ENSO events, notably during 1982-1983, 1997-1998, and 2015-2016. We also found, however, that bull kelp recovered quickly from these events, as years with large decreases in canopy coverage were frequently followed by years with large bull kelp canopy increases.

Since plastic pollution began entering the ocean in the 1950s, trends have shown that this pollution has been and will continue to increase in the future. Once plastics reach the ocean they never fully biodegrade; instead they break down into smaller and smaller pieces until they reach the microplastic stage.  The only methods to gather ocean plastic data are by plankton net tows, which are costly, inefficient, and time consuming, and computer-generated models. A reliable method to locate floating ocean plastic via remote sensing has yet to be discovered. Although the ocean absorbs nearly all light beyond the 700 nm range, suspended microplastics are expected to backscatter light in the near-infrared (NIR) range resulting in non-negligible signals.  This project investigates the potential to detect ocean microplastics with remote sensing based on elevated reflectance within the NIR region. We present modeled inherent optical properties of plastics in water derived from above-water radiance measurements to evaluate expected signals for water with high concentrations of microplastics. We also develop matchups between satellite imagery and in-situ plastic abundance measurements from the Sea Education Association’s dataset in a region that has a statistically higher prevalence of microplastics.

Dinoflagellates constitute 75% of all harmful algal species and are the phytoplankton functional type responsible for producing the vast majority of toxic red tides. Areas along the California coastline, known as retention zones, are popular seeding sites for dinoflagellates, particularly during the autumn, from August to November. Retention zones are confined areas downstream of capes or headlands where cold, nutrient-rich water becomes trapped beneath a shallow, distinct thermocline, in lieu of a contiguous active upwelling system. The stratification and localized mixing of these “upwelling shadows” traps heat and microorganisms. Dinoflagellates’ ability to vertically migrate deeper into the water column to retrieve nutrients at depth provides them with a competitive advantage in areas where nutrient-rich water is not upwelled to the sea surface. Airborne and satellite measurements (AVIRIS and HICO) of retention zones in Monterey Bay, Santa Barbara, Point Reyes, and Santa Monica, with Newport Beach used as a non-retention baseline, were processed using PHYDOtax, an algorithm that discriminates phytoplankton functional types. We present advection models derived using the General NOAA Operational Modeling Environment (GNOME) software and compare with sea surface temperature and salinity profiles to evaluate the potential of retention zones for seeding broader regions of the California coastline.

Phytoplankton are the foundation of the oceanic ecosystem, and the composition of different phytoplankton functional groups is relevant to many ocean biogeochemical cycles. Remote sensing methods provide novel tools to measure phytoplankton size, a key metric for understanding ecological structure. Using remote sensing methods, we are able to measure and analyze a larger area than when using in-situ methods, but with lower accuracy. Different phytoplankton cell shapes and sizes are potential sources of error for satellite size class estimates. We compare multiple remote sensing algorithms that discriminate phytoplankton sizes and groups (e.g. diatoms, dinoflagellates) with in-water imagery of phytoplankton cells to evaluate whether changes in phytoplankton size and shape correspond to shifts in remote sensing size retrievals. We validate the size class algorithms derived using MODIS-Aqua and AVIRIS imagery from Monterey Bay during June 2018 using matchups with the Imaging Flow Cytobot, an in-situ flow cytometer that collects water from the environment and takes images of particles containing chlorophyll. Snapshots from the Imaging Flow Cytobot allow real time observation of phytoplankton cells during environmental perturbations and provide a rich dataset for evaluating remote sensing algorithms.

In January 2018, Santa Barbara, California suffered from a devastating combination of rainfall, historic drought, and fires, leading to the Montecito Mudslide. The year preceding the mudslide had anomalously low precipitation, and during December 2017 the Thomas fire killed off large amounts of vegetation that normally protected soils on the sloping hills of Santa Barbara County. When the torrential January rains arrived, local rivers and creeks were overwhelmed, and large amounts of debris ended up on the CA 101 highway and in residential neighborhoods. To remove the debris, several hundred thousand cubic meters of debris were dumped on local Santa Barbara County beaches, with the expectation that ocean waves and tides would remove the debris. Here we present remote sensing imagery from MODIS-Aqua to track the plume of the dumped debris. We test how long the perturbation persisted in the region and estimate whether the retention and flushing observed would be comparable if the dumping occurred during different months or in different locations. Our results suggest that the plume dispersed within the Santa Barbara channel within weeks of the dumping event.  Advection by currents within the Santa Barbara Channel is compared with dynamics of other, more retentive coastal zones.

The Thomas Fire was the biggest fire in California state history, burning an astounding 201,893 acres. Based on NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua imagery, the event filled the Santa Barbara Channel (SBC) with a smoke plume, transporting ash towards the marine environment. Although the effect of ash from fires on marine ecosystems is unknown, volcanic ash has been shown to fertilize oceanic environments with nutrients and stimulate the growth of diatoms and other phytoplankton. Nutrient over-enrichment, which may occur from ash deposition, may favor specific phytoplankton groups. But little work has been done to study the implications that ash from wildfires has on the biology of nearby ocean regions. Since ash deposition brings nutrients to the oceans, we use the Thomas Fire as an opportunity to evaluate the effects of the changing atmospheric and land environments on the ocean ecosystem. Due to the lack of in situ data, ash deposition is difficult to quantify accurately. Hence, the smoke plume track was evaluated with MODIS imagery and with the NOAA model HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory). Advection of deposited ash in the ocean was estimated using the GNOME (General NOAA Operational Modeling Environment) model, which utilizes dispersion properties of surface-associated materials (originally designed for oil) while taking meteorological conditions and SBC currents into consideration. Furthermore, a cruise coincidentally collected data under the location where the smoke plume was prominent, confirmed by satellite observations and model results of the plume itself. An Imaging Flow Cytobot deployed onboard observed species uncharacteristic for the region during that season. We analyze phytoplankton community during the ash fertilization event and compare with phytoplankton climatology for the region to test whether the ash conditions led to biological anomalies in the SBC. Because fires frequently deposit ash into rivers, lakes, and coastal waters, understanding the role of ash in fertilizing phytoplankton blooms is important to understanding the importance of fires on biogeochemical processes of marine and aquatic ecosystems.

As the only remaining supertanker berth on the West Coast, the Port of Long Beach is one of the largest marine oil traffic routes in the United States. Each day, at least 50 million gallons of oil arrive by ship somewhere in the Los Angeles County region.  This vessel traffic transits heavily along the Western Approach and Southern Approach elements of the Traffic Separation Scheme (TSS) set for the area. Both of these port access approaches require that vessels transit near areas deemed by federal, state and local governments as Marine Protected Areas (MPAs). These MPAs include the Channel Islands National Marine Sanctuary, Catalina Island South Coast MPA, and beaches in Santa Barbara, Ventura, Los Angeles and Orange counties. Currently, proposals to modify the TSS regions exist, and if implemented would alter the proximity of some ship traffic to the MPAs. This study evaluates potential environmental impacts and benefits from modification of the TSS regions, for example in the case of a major oil spill event. Using a spill trajectory experiment within the General NOAA Operational Modeling Environment (GNOME) software, we compare modeled spill trajectories between existing and proposed TSS regions, and find reduced likelihood of beaching of spilled particles after modification of the TSS lanes. We then analyze the GNOME data using ArcMap geoprocessing tools to determine which protected areas would be at risk for a spill at each location. Finally, we test adherence of large tanker ships to current TSS requirements using Automatic Identification System (AIS) data. The findings provide additional environmental rationale for modifications to the TSS in order to protect MPAs in the event of an oil spill within the Western Approach element of the Long Beach / Los Angeles TSS.

As pollutants are emitted, removal processes prevent their accumulation in the atmosphere. One removal process is oxidation via the hydroxyl radical, OH. Commonly referred to as the “detergent of the atmosphere” the hydroxyl radical is highly reactive and is a major sink for greenhouse gases and pollutants such as carbon monoxide and methane. Previous studies indicate that CO and methane are the main removal processes for OH.  Thus, by increasing carbon monoxide and methane emissions, it is likely that the lifetime of other OH removed gases may increase due to the loss of an oxidizing sink. In this study, the relative reaction rates of 36 compounds measured on NASA airborne science missions from 2012-2018 in Los Angeles and Oildale, California are compared in order to determine the effect that different compounds have on the reactivity of OH. Calculated at STP, relative reaction rates are combined with mixing ratios to determine the percent of OH consumed by each compound. These results show that at altitudes less than 3500 feet, carbon monoxide emissions react with hydroxyl on average 6% more in Los Angeles than in Oildale. In addition, at altitudes less than 3500 feet, methane emissions react with hydroxyl on average 7% more in Oildale.  Acetaldehyde, a compound used in the manufacture of acetic acid and also the product of ethanol oxidation in the atmosphere, was found to react with 14% and 20% of hydroxyl in Los Angeles and Oildale. Altitudinal data depict significant changes in relative hydroxyl consumption. These data may aid in the determination of effective emission reduction proposals. Future estimations should include OH photolysis and reactions with NOx, which are additional sinks of hydroxyl that will increase the accuracy of these estimations.

Formed anthropogenically in 1905 the Salton Sea, CA is a saline endorheic lake. Dimethyl sulfide (DMS) is an organic sulfide compound, mainly emitted by marine organisms, which oxidizes and forms reactive sulfur compounds. The reaction of DMS + OH → Products is known to draw-down hydroxyl (OH) radical concentrations in the atmosphere and produce sulfuric acid (H2SO4). Ground samples were taken downwind of the Salton Sea in five locations using 2-Liter stainless steel cans by the National Aeronautics and Space Administration (NASA) Student Airborne Research Program whole air sampling group in June 2018. These samples were then analyzed at the Rowland-Blake Laboratory at University of California, Irvine. The Salton Sea was found to have mixing ratios of 80-280 pptv DMS, greatly enhanced compared to airborne samples. In order to determine if DMS is drawing down the OH radical, a relative rate percentage was calculated with R[DMS]/R[CO]. A minimum reaction ratio of 5% indicated that DMS does draw down the OH radical at the Salton Sea via the DMS oxidation reaction, which allows for the formation of H2SO4. Using pseudo-first order assumptions, the amount of H2SO4 created by the DMS on the ground was calculated to be a maximum of 0.8 µg/m3 or 205 pptv. This is lower than the California Air Resources Board’s twenty-four hour average ambient air quality standard for sulfates of 25 µg/m3. Hence, the H2SO4 that is a product of the DMS oxidation reaction at the Salton Sea is not harmful to the local community. Future studies should take whole air samples at ground locations around, as well as on, the Salton Sea, every hour for two to three days in order to determine DMS diurnal cycles. In addition, NASA DC-8 flights should take airborne samples to track DMS chemistry at higher altitudes.

On June 25, 26, and 27, 2018, the NASA Student Airborne Research Program collected whole air samples throughout Southern California using stainless steel canisters while aboard NASA’s DC-8. Ground samples were also collected around the Salton Sea, located in Southern California, on June 28 and 29, 2018.  Samples were analyzed in the Rowland-Blake Laboratory at the University of California, Irvine using gas chromatography and mass spectrometry. Historically, large mixing ratios of dimethyl sulfide (DMS) were found along the shores of the Salton Sea. However, in 2018 DMS was greatly enhanced relative to previous Imperial Valley sampling.  Dimethyl sulfide is a biological sulfur compound produced indirectly by phytoplankton. In the air, sulfate aerosols produced by DMS photochemistry can negatively impact human respiratory health and act as cloud condensation nuclei, influencing climate. In this study, we used HYSPLIT modeling (NOAA) to track the forward trajectory and the dispersion of sulfate aerosols so as to better understand how they travel through the atmosphere and impact the Salton Sea region. We found that DMS produced by the Salton Sea does not travel over any populated areas during the summer months; however, the HYSPLIT model showed that during the winter, DMS moves directly over populated areas in the region. We calculated that the DMS produced by the Salton Sea contributes an upward bound of 4% to the total Salton Sea’s annual regional aerosol load of 8 ug/m3, which has been recorded by California’s Air Resource Board. Because of the high mixing ratios of DMS and the potential for Salton Sea DMS to impact regional health and climate, future studies should take more rigorous sampling at the Salton Sea, ensuring that samples are collected along the entire perimeter, during different seasons, upwind and downwind, as well as farther from the shore of the Salton Sea.

Light alkyl nitrates, such as methyl nitrate (MeONO2) and ethyl nitrate (EtONO2), are commonly attributed to being carriers of reactive nitrogen species that help to regulate tropospheric ozone. In previous studies, MeONO2 and EtONO2 have been traced back to a common oceanic source with data showing the ratio of MeONO2 to EtONO2 changes based on latitudinal position. In order to observe MeONO2 and EtONO2 mixing ratios, samples were collected on board the Student Airborne Research Program (SARP) DC-8 during the fourth research flight using the UC Irvine Whole Air Sampler. Samples taken during the flight were analyzed at the UC Irvine Rowland/Blake laboratory using gas chromatography and mass spectrometry. Results showed that at low altitudes (<26K feet) and the top of the Total Carbon Column Observing Network (TCCON) spiral the mixing ratios of MeONO2 to EtONO2 are consistent with expected data. However, during the TCCON descent there was an increase in the mixing ratio of MeONO2 and EtONO2 between ~36K feet and 25K feet. The ratio of MeONO2 to EtONO2 in this plume was ~7:1. The C2H2/CO atmospheric processing scale for each sample in the plume was calculated to determine the air samples were found to be <1 (ppt/ppb) indicating aged air. Through the utilization of HYSPLIT a back trajectory was developed to locate sources of air over a number of time intervals. The back trajectory coupled with an understanding of photolysis rate it was determined that the elevated light alkyl nitrate ratio was a result of aged well mixed air moving up from the equator and mixing with air from the Gulf of Mexico.

Analyzing whole air samples from 2014 revealed elevated levels of pollutants 7.5-9.5 km above sea level at the Total Carbon Column Observation Network (TCCON) site at Edwards Air Force Base (Kern County, California).  Gas chromatography analysis of these samples revealed the presence of common trace tropospheric gases such as carbon monoxide, carbon dioxide, methane and non-methane hydrocarbons (NMHC’s) at higher levels. The presence of chloroform at 740 ± 24 pptv in five samples was a good indicator that the source was coal.   Bituminous coal has always been and still continues to be a cheap energy source.  Despite its benefits, combustion of it produces greenhouse gases and volatile organic compounds (VOC’s).   Using a model for depicting long range transport of hydrocarbons (Rudolph and Johnen, 1990), the times of transport of gases including ethane, ethyne, propane, butane and benzene were estimated.  Using literature values for Chinese coal burning emissions and comparing ratios of the aforementioned hydrocarbons to another hydrocarbon, such as ethene, five separate transit times for the five individual samples were determined. Interestingly, the variance for the individual points was very small and in most cases less than 10%.  There was a slight difference in the transit times for the air masses that contained the samples collected. The tight agreement in transit times for the hydrocarbons indicates that these gases were from the same source and they provided parameters for determining the locations of the emissions through HYSPLIT modeling.  The results of HYSPLIT model suggests that the emissions originated from Eastern and Central China. Solvents known to be used in China (eg. 1,2-DCE) were also enhanced in the plume samples further suggesting the air mass was affected by Chinese emissions.  This study indicates that surface emissions of VOCs from China can be transported to US airspace in less than one week.

Hydrochlorofluorocarbons (HCFCs) were developed as intermediate compounds to help wean the world off of chlorofluorocarbons (CFCs). Mandated through the Montreal Protocol and Clean Air Act (CAA), the EPA established guidelines and phase out plans for the usage of HCFCs in response to the rapid rise of HCFC use throughout the globe.  Whole air samples collected on board the DC-8 during the NASA Student Airborne Research Program (SARP) 2018 campaign contained compelling data for HCFC-22, HCFC-141b, and HCFC-142b; three compounds considered by the EPA to be the worst offenders out of all HCFCs due to their high ozone depletion potentials (ODP). Investigation into local air quality data can be used as a regulatory tool to check ‘problem areas’ for compliance to EPA standards. For example, air data collected at Mt. Wilson in Los Angeles County during 2014 showed highly elevated concentrations in HCFC-142b until the start of January 2015, which directly coincided with the Clean Air Act’s 2015 phase out goal for HCFC-142b and HCFC-22. This is an excellent example of compliance.  However, while analyzing this year’s data, concentration enhancements in mixing ratios for HCFC-22 and HCFC-141b were found around 33.8°N and 35.5°N. These elevated levels were located near the downtown LA area and Bakersfield. HCFC-22 levels reached up to 800 ppt; much higher than the 240 + 10 ppt background levels. HCFC-141b levels reached 50 ppt in certain areas, also much higher than its 24 + 2 ppt background levels. These values in close proximity to urban hubs suggest that these areas were emitting HCFCs. Emission information for these gases can be nebulous, and enforcement of this kind of policy has, historically, been difficult. In the future, local and/or federal regulatory agencies could utilize this sampling and analysis plan to improve their compliance monitoring techniques.

Halon-1301 is a potent ozone depletor that is mainly used for fire suppression in aviation and data centers. Its production was phased out by January 1, 1994 under the Montreal Protocol, but stocks made before then are legal and still in use today. “Good-faith” regulations have been put in place by the EPA to manage Halon 1301’s use, storage and disposal. Over the course of June 25-27, 2018, whole air samples of the atmosphere were collected in and around the California Central Valley on board the NASA DC-8 during four SARP 2018 research flights. These samples were then analyzed in the Rowland-Blake laboratory at University of California Irvine using gas chromatography and mass spectrometry. Enhancements of Halon-1301 (~2 ppt above ~3.5 ppt background level) were found in the southern part of the Central Valley spanning a range of ~150 km N-S from Bakersfield to Five Points, CA. This enhancement is most likely either from civilian aviation in the Bakersfield area or military activity in the valley. Although Halon-1301 concentrations were high in and around Bakersfield, amounts of other refrigerants and CFC compounds normally associated with civilian aviation were not present in proportional concentrations to Halon-1301 outside of Bakersfield. The nonlinear association indicates that civilian aviation and airports are not the cause of this increase throughout the southern part of the valley. A number of Air Force and Navy bases are located in California, including the new Master Jet Base at Naval Air Station Lemoore which stations more than 200 aircraft and is currently expanding. We flew within 10 kilometers of it and observed increased concentrations of Halon-1301. Increased Halon-1301 concentrations could be attributed to the expansion of the Lemoore Naval Base, and be an indicator of increased military activity