Oceanography and Atmospheric Sciences and Meteorology Commons^™

Microplastic Prevalence In Four Oregon Rivers Along A Rural To Urban Gradient Applying A Cost-Effective Validation Technique, Amy Valine, Ashley Peterson, Dorothy Horn, Kaegan M. Scully‐Engelmeyer, Elise F. Granek

Environmental Science and Management Faculty Publications and Presentations

Microplastics are ubiquitous in our environment and are found in rivers, streams, oceans, and even tap water. Riverine microplastics are relatively understudied compared to those in marine ecosystems. In Oregon, we sampled eight sites along four freshwater rivers spanning rural to urban areas to quantify microplastics. Plankton tow samples from sites along the Columbia, Willamette, Deschutes, and Rogue Rivers were analyzed using traditional light microscopy for initial microplastic counts. Application of Nile Red dye to validate microplastics improved microplastic identification, particularly for particles (Wilcox Test; p‐value=0.001). Nile Red‐corrected microfiber abundance was correlated with human population within five kilometers of the …

Climate From The Mcmurdo Dry Valleys, Antarctica, 1986–2017: Surface Air Temperature Trends And Redefined Summer Season, Maciej K. Obryk, Peter T. Doran, Andrew G. Fountain, M. Myers, Christopher P. Mckay

Geology Faculty Publications and Presentations

The weather of the McMurdo Dry Valleys, Antarctica, the largest ice‐free region of the Antarctica, has been continuously monitored since 1985 with currently 14 operational meteorological stations distributed throughout the valleys. Because climate is based on a 30‐year record of weather, this is the first study to truly define the contemporary climate of the McMurdo Dry Valleys. Mean air temperature and solar radiation based on all stations were −20°C and 102 Wm⁻², respectively. Depending on the site location, the mean annual air temperatures on the valleys floors ranged between −15°C and −30°C, and mean annual solar radiation varied …

Microplastics In Aquatic Organisms: Improving Understanding And Identifying Research Directions For The Next Decade, Elise F. Granek, Susanne Brander, E. B. Holland

Environmental Science and Management Faculty Publications and Presentations

The study of environmental microplastics has increased over the past decade, with hundreds of new studies and resultant papers on the presence, fate, and sources of microplastics in marine and freshwater systems (Fig. 1). Despite the explosion of interest in the topic and in comparison to the research on the presence of microplastics in marine or fresh waters, there have been notably fewer studies on the extent to which these debris items are ingested by aquatic organisms and far fewer on the potential consequences, or response to their presence in organismal guts, tissues, and food webs. Even less research has …

Dropsonde Observations Of The Ageostrophy Within The Pre-Cold-Frontal Low-Level Jet Associated With Atmospheric Rivers, Rueben Demirdgian, Joel R. Norris, Andrew Martin, F. Martin Ralph

Geography Faculty Publications and Presentations

The pre-cold-frontal low-level jet (LLJ) is an important contributor for water vapor transport within atmospheric rivers, though its dynamics are not completely understood. The present study investigates the LLJ using dropsonde observations from 24 cross-atmospheric river transects taken during the CalWater-2014, 2015 and the AR-Recon 2016, 2018 field campaigns. It is found that the LLJ, located at ;1-km elevation ahead of the cold front, has an average maximum wind speed of 30ms21 and is strongly supergeostrophic with an average ageostrophic component of 6ms21. The alongfront ageostrophy occurs within the atmospheric layer (750–1250 m) known to strongly control orographic precipitation associated …

Deuterium Excess And 17o-Excess Variability In Meteoric Water Across The Pacific Northwest, Usa, John Bershaw, Dougal Hansen, Andrew Schauer

Geology Faculty Publications and Presentations

High-precision triple oxygen isotope analysis of water has given rise to a novel second-order parameter, ¹⁷O-excess (often denoted as δ¹⁷O), which describes the deviation from a reference relationship between δ¹⁸O and δ¹⁷O. This tracer, like deuterium excess (d-excess), is affected by kinetic fractionation (diffusion) during phase changes within the hydrologic cycle. However, unlike d-excess, ¹⁷O-excess is present in paleowater proxy minerals and is not thought to vary significantly with temperature. This makes it a promising tool in paleoclimate research, particularly in relatively arid continental regions where traditional approaches have produced equivocal results. …

Urban-Rural Surface Temperature Deviation And Intra-Urban Variations Contained By An Urban Growth Boundary, Kevan B. Moffett, Yasuyo Makido, Vivek Shandas

Urban Studies and Planning Faculty Publications and Presentations

The urban heat island (UHI) concept describes heat trapping that elevates urban temperatures relative to rural temperatures, at least in temperate/humid regions. In drylands, urban irrigation can instead produce an urban cool island (UCI) effect. However, the UHI/UCI characterization suffers from uncertainty in choosing representative urban/rural endmembers, an artificial dichotomy between UHIs and UCIs, and lack of consistent terminology for other patterns of thermal variation at nested scales. We use the case of a historically well-enforced urban growth boundary (UGB) around Portland (Oregon, USA): to explore the representativeness of the surface temperature UHI (SUHI) as derived from Moderate Resolution Imaging …

Connecting Local-Scale Heavy Precipitation To Large-Scale Meteorological Patterns Over Portland, Oregon Using Observations And Climate Models, Christina Marie Aragon

Dissertations and Theses

Precipitation timing and magnitude is essential to human, ecological, and economic systems. Climate change may be altering the character of precipitation locally to globally, thus it is vital that resource managers, practitioners, and decision makers understand the nature of this change. This thesis was conducted in partnership with the City of Portland Bureau of Environmental Services (BES), and the Portland Water Bureau (PWB) in order to support resiliency planning around precipitation and precipitation extremes.

This work has two primary phases, which are discussed in chapter 2 and 3 of this thesis. The first phase of this research entails characterization of …

Monitoring Lesser Known Harmful Algal Blooms On The Oregon Coast, Taylor Dodrill, Tawnya D. Peterson, Matthew Hunter, Micah Rogers

OHSU-PSU School of Public Health Annual Conference

Ocean warming has expanded the niche of harmful algal blooms (HABs), including HABs previously believed to pose little risk of shellfish contamination in the Pacific Northwest. Monitoring efforts in Washington and California have demonstrated that Dinophysis spp. is a HAB of emerging concern and has been linked to diarrhetic shellfish poisoning events. However, quantitative monitoring for Dinophysis spp. on the Oregon Coast has been limited. This analysis provides a preliminary characterization of risk that Dinophysis spp. poses to shellfish consumers in Oregon. Furthermore, we assess the predator-prey interaction between Dinophysis spp. and its prey, Mesodinium rubrum, to determine whether …

Contrasting Local And Long-Range-Transported Warm Ice-Nucleating Particles During An Atmospheric River In Coastal California, Usa, Andrew C. Martin, Gavin Cornwell, Charlotte M. Beall, Forest Cannon, Sean Reilly, Bas Schapp, Dolan Lucero, Jessie Creamean, F. Martin Ralph, Hari T. Mix, Kimberly Prather

Geography Faculty Publications and Presentations

Ice-nucleating particles (INPs) have been found to influence the amount, phase and efficiency of precipitation from winter storms, including atmospheric rivers. Warm INPs, those that initiate freezing at temperatures warmer than −10ºC, are thought to be particularly impactful because they can create primary ice in mixed-phase clouds, enhancing precipitation efficiency. The dominant sources of warm INPs during atmospheric rivers, the role of meteorology in modulating transport and injection of warm INPs into atmospheric river clouds, and the impact of warm INPs on mixed-phase cloud properties are not well-understood. In this case study, time-resolved precipitation samples were collected during an atmospheric …

Mountain Lakes: Eyes On Global Environmental Change, Katrina A. Moser, Jill S. Baron, Janice Brahney, Isabella A. Olesky, Jasmine E. Saros, Elizabeth J. Hundey, Steven A. Sadro, Jiri Kopácek, Ruben Sommaruga, Martin J. Kainz, Angela L. Strecker, Sudeep Chandra, David M. Walters, Daniel L. Preston, Neal Michelutti, Fabio Lepori, Sarah A. Spaulding, Kyle R. Christianson, John M. Melack, J. P. Smol

Environmental Science and Management Faculty Publications and Presentations

Mountain lakes are often situated in protected natural areas, a feature that leads to their role as sentinels of global environmental change. Despite variations in latitude, mountain lakes share many features, including their location in catchments with steep topographic gradients, cold temperatures, high incident solar and ultraviolet radiation (UVR), and prolonged ice and snow cover. These characteristics, in turn, affect mountain lake ecosystem structure, diversity, and productivity. The lakes themselves are mostly small and shallow, and up until recently, have been characterized as oligotrophic. This paper provides a review and update of the growing body of research that shows that …

A Recent Systematic Increase In Vapor Pressure Deficit Over Tropical South America, Armineh Barkhordarian, Bahareh Saatchi, Ali Behrangi, Paul C. Loikith, Carlos R. Mechoso

Geography Faculty Publications and Presentations

We show a recent increasing trend in Vapor Pressure Deficit (VPD) over tropical South America in dry months with values well beyond the range of trends due to natural variability of the climate system defined in both the undisturbed Preindustrial climate and the climate over 850–1850 perturbed with natural external forcing. This trend is systematic in the southeast Amazon but driven by episodic droughts (2005, 2010, 2015) in the northwest, with the highest recoded VPD since 1979 for the 2015 drought. The univariant detection analysis shows that the observed increase in VPD cannot be explained by greenhouse-gas-induced (GHG) radiative warming …

Predictability Of Non-Phase-Locked Baroclinic Tides In The Caribbean Sea, Edward D. Zaron

Civil and Environmental Engineering Faculty Publications and Presentations

Abstract.

The predictability of the sea surface height expression of baroclinic tides is examined with 96h forecasts produced by the AMSEAS operational forecast model during 2013–2014. The phase-locked tide, both barotropic and baroclinic, is identified by harmonic analysis of the 2-year record and found to agree well with observations from tide gauges and satellite altimetry within the Caribbean Sea. The non-phase-locked baroclinic tide, which is created by timevariablemesoscalestratificationandcurrents,maybeidentified from residual sea level anomalies (SLAs) near the tidal frequencies. The predictability of the non-phase-locked tide is assessed by measuring the difference between a forecast – centeredat T+36, T+60,or T+84h–andthemodel’slater verifying analysis …

Classification Of Aerosol Population Type And Cloud Condensation Nuclei Properties In A Coastal California Littoral Environment Using An Unsupervised Cluster Model, Samuel A. Atwood, Sonia M. Kreidenweis, Paul J. Demott, Markus D. Petters, Gavin Cornwell, Andrew C. Martin, Kathryn A. Moore

Geography Faculty Publications and Presentations

Aerosol particle and cloud condensation nuclei (CCN) measurements from a littoral location on the northern coast of California at Bodega Bay Marine Laboratory (BML) are presented for approximately six weeks of observations during the boreal winter–spring as part of the CalWater-2015 field campaign. The nature and variability of surface (marine boundary layer, MBL) aerosol populations were evaluated by classifying observations into periods of similar aerosol and meteorological characteristics using an unsupervised cluster model to derive distinct littoral aerosol population types and link them to source regions. Such classifications support efforts to understand the impact of changing aerosol properties on precipitation …

Characterizing Temperature Variability States Across Southern South America And Associated Synoptic-Scale Meteorological Patterns, Judah Adam Detzer

Dissertations and Theses

The aim of this thesis is to understand spatiotemporal temperature variability in southern South America by identifying overarching temperature variability states and their associated synoptic-scale meteorological patterns. Further, the temporal frequency of occurrence of those temperature variability states is investigated as is the role of recurrent low-frequency modes of climate variability (El Niño Southern Oscillation and the Southern Annular Mode) on temperature variability. K-means cluster analysis is used to group all months during the period 1980-2015 into four primary categories for summer and winter separately. Monthly maps of temperature anomalies are provided as input to the k-means algorithm and the …

Aliased Tidal Variability In Mesoscale Sea Level Anomaly Maps, Edward Zaron, Richard D. Ray

Civil and Environmental Engineering Faculty Publications and Presentations

Sea level anomaly (SLA) maps are routinely produced by objective analysis of data from the constellation of satellite altimeter missions in operation since 1992. Beginning in 2014, changes in the Data Unification and Altimeter Combination System (DUACS) used to create the SLA maps resulted in improved spatial resolution of mesoscale variability, but it also increased the levels of aliased tidal variability compared to the methodology employed prior to 2014. The present work investigates the magnitude and spatial distribution of these tidal signals, which are typically smaller than 1 cmin the open ocean but can reach tens of centimeters in the …

Dynamics Of Prochlorococcus Diversity And Photoacclimation During Short-Term Shifts In Water Column Stratification At Station Aloha, Anne W. Thompson, Ger Van Den Engh, Nathan A. Ahlgren, Kathleen Kouba, Samantha Ward, Samuel T. Wilson, David M. Karl

Biology Faculty Publications and Presentations

The cyanobacterium Prochlorococcus is the dominant phototroph in surface waters of the vast oligotrophic oceans, the foundation of marine food webs, and an important component of global biogeochemical cycles. The prominence of Prochlorococcus across the environmental gradients of the open ocean is attributed to its extensive genetic diversity and flexible chlorophyll physiology, enabling light capture over a wide range of intensities. What remains unknown is the balance between temporal dynamics of genetic diversity and chlorophyll physiology in the ability of Prochlorococcus to respond to a variety of short (approximately 1 day) and longer (months to year) changes in the environment. …

Controls On Deuterium Excess Across Asia, John Bershaw

Geology Faculty Publications and Presentations

Deuterium excess (d-excess) is a second-order stable isotope parameter measured in meteoric water to understand both the source of precipitation and the evolution of moisture during transport. However, the interpretation of d-excess patterns in precipitation is often ambiguous, as changes in moisture source and processes during vapor transport both affect d-excess in non-unique ways. This is particularly true in Asia where continental moisture travels a long distance across diverse environments from unique moisture sources before falling as precipitation. Here, I analyzed published d-excess records from meteoric water throughout Asia to better characterize what influences d-excess values. I conclude that, (1) …

Assessment Of Observational Uncertainty In Extreme Precipitation Over The Continental United States, Emily Anne Slinskey

Dissertations and Theses

An extreme precipitation categorization scheme, developed to temporally and spatially visualize and track the multi-scale variability of extreme precipitation climatology, is introduced over the continental United States and used as the basis for an observational dataset intercomparison. The categorization scheme groups three-day precipitation totals exceeding 100 mm into five precipitation categories, or "P-Cats". To assess observational uncertainty across a range of precipitation measurement approaches, we compare in situ station data from the Global Historical Climatology Network-Daily (GHCN-D), satellite derived data from the Tropical Rainfall Measuring Mission (TRMM), gridded station data from the Parameter-elevation Regression on Independent Slopes Model (PRISM), global …

Baroclinic Tidal Sea Level From Exact-Repeat Mission Altimetry, Edward Zaron

Portland Institute for Computational Science Publications

A near-global model for the sea-surface expression of the baroclinic tide has been developed using exact-repeat mission altimetry. The methodology used differs in detail from other altimetry-based estimates of the open ocean baroclinic tide, but it leads to estimates which are broadly similar to previous results. It may be used for prediction of the baroclinic sea level anomaly at the frequencies of the main diurnal and semidiurnal tides, K₁, O₁, M₂, S₂, as well as the annual modulates of M₂, denoted MA₂ and MB₂. Based on a …

High-Resolution Observations In The Western Mediterranean Sea: The Rep14-Med Experiment, Reiner Onken, Heinz-Volker Fiekas, Laurent Beguery, Ines Borrione, Andreas Funk, Michael Hemming, Jaime Hernandez-Lasheras, Karen J. Heywood, Jan Kaiser, Michaela Knoll, Baptiste Mourre, Paolo Oddo, Pierre-Marie Poulain, Bastien Y. Queste, Aniello Russo, Kiminori Shitashima, Martin Siderius, Elizabeth Thorp Küsel

Electrical and Computer Engineering Faculty Publications and Presentations

The observational part of the REP14-MED experiment was conducted in June 2014 in the Sardo-Balearic Basin west of Sardinia (western Mediterranean Sea). Two research vessels collected high-resolution oceanographic data by means of hydrographic casts, towed systems, and underway measurements. In addition, a vast amount of data was provided by a fleet of 11 ocean gliders, time series were available from moored instruments, and information on Lagrangian flow patterns was obtained from surface drifters and one profiling float. The spatial resolution of the observations encompasses a spectrum over 4 orders of magnitude from O(10¹ m) to O(10⁵ m), and …

Interlaboratory Comparison Of Δ13c And Δd Measurements Of Atmospheric Ch4 For Combined Use Of Data Sets From Different Laboratories, Taku Umezawa, Carl Brenninkmeijer, Thomas Röckmann, Carina Van Der Veen, Stanley C. Tyler, Ryo Fujita, Shinji Morimoto, Shuji Aoki, Todd Sowers, Jochen Schmitt, Michael Bock, Jonas Beck, Hubertus Fischer, Sylvia E. Michel, Bruce H. Vaughn, John B. Miller, James W.C. White, Gordon Brailsford, Hinrich Schaefer, Peter Sperlich, Willi A. Brand, Michael Rothe, Thomas Blunier, David Lowry, Rebecca E. Fisher, Euan G. Nisbet, Andrew L. Rice, Peter Bergamaschi, Cordelia Veidt, Ingeborg Levin

Physics Faculty Publications and Presentations

We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH₄ (δ¹³C-CH₄ and δD-CH₄). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of δ¹³C-CH₄ and δD- CH₄ measurements among data sets reported from different laboratories; the differences among laboratories …

Social Position Influencing The Water Perception Gap Between Local Leaders And Constituents In A Socio-Hydrological System, Melissa Haeffner, Douglas Jackson-Smith, Courtney G. Flint

Environmental Science and Management Faculty Publications and Presentations

How well city leaders represent their constituents and meet their needs are key concerns in transitioning to local sustainable water governance. To date, however, there is little research documenting the influence of social position between elected leaders who make policy, career staff water managers who design and operate systems and implement policies, and the members of the public whose individual water use behaviors are important drivers of water sustainability outcomes. In this study, we ask: ‘‘How does social position explain variation in water perceptions and concerns between different actors in a sociohydrological system?’’ Using a mixed method approach with survey …

A Multi-Year Data Set On Aerosol-Cloud-Precipitation-Meteorology Interactions For Marine Stratocumulus Clouds, Armin Sorooshian, Alexander B. Macdonald, Hossein Dadashazar, Kelvin H. Bates, Matthew M. Coggon, Jill S. Craven, Ewan Crosbie, Scott P. Hersey, Natasha Hodas, Jack J. Lin, Arnaldo Negrón Marty, Lindsay C. Maudlin, Andrew R. Metcalf, Shane M. Murphy, Luz T. Padró, Gouri Prabhakar, Tracey A. Rissman, Taylor Shingler, Varuntida Varutbangkul, Zhen Wang, Roy K. Woods, Patrick Y. Chuang, Athanasios Nenes, Haflidi H. Jonsson, Richard C. Flagan, John H. Seinfeld

Environmental Science and Management Faculty Publications and Presentations

Airborne measurements of meteorological, aerosol, and stratocumulus cloud properties have been harmonized from six field campaigns during July-August months between 2005 and 2016 off the California coast. A consistent set of core instruments was deployed on the Center for Interdisciplinary Remotely- Piloted Aircraft Studies Twin Otter for 113 flight days, amounting to 514 flight hours. A unique aspect of the compiled data set is detailed measurements of aerosol microphysical properties (size distribution, composition, bioaerosol detection, hygroscopicity, optical), cloud water composition, and different sampling inlets to distinguish between clear air aerosol, interstitial in-cloud aerosol, and droplet residual particles in cloud. Measurements …

Influence Of Recreational Activity On Water Quality Perceptions And Concerns In Utah: A Replicated Analysis, Matthew J. Barnett, Douglas Jackson-Smith, Melissa Haeffner

Environmental Science and Management Faculty Publications and Presentations

Both social structural factors and direct sensory experiences can contribute to the development of environmental perceptions and concerns. We use two separate surveys of Utah adults to explore the association between sociodemographic characteristics and participation in recreational activities on water quality perceptions and concerns. We find that engaging in outdoor recreation is systematically associated with more positive water quality perceptions and higher levels of concern about impaired water quality. However, water quality perceptions appear to be shaped more by social characteristics (age, education, gender, race, religion, and income) and by generic measures of overall recreation behavior than by indicators of …

Mapping Water Availability, Cost And Projected Consumptive Use In The Eastern United States With Comparisons To The West, Vincent C. Tidwell, Barbie D. Moreland, Calvin R. Shaneyfelt, Peter Kobos

Environmental Science and Management Faculty Publications and Presentations

The availability of freshwater supplies to meet future demand is a growing concern. Water availability metrics are needed to inform future water development decisions. Furthermore, with the help of water managers, water availability was mapped for over 1300 watersheds throughout the 31-contiguous states in the eastern U.S. complimenting a prior study of the west. The compiled set of water availability data is unique in that it considers multiple sources of water (fresh surface and groundwater, wastewater and brackish groundwater); accommodates institutional controls placed on water use; is accompanied by cost estimates to access, treat and convey each unique source of …

Oregon Lake Watch Program: Training Manual, Rich Miller, Crysta Gantz, Vanessa Morgan, Angela L. Strecker, Mark D. Sytsma

Center for Lakes and Reservoirs Publications and Presentations

Oregon is fortunate to have a wide variety of beautiful and enjoyable lakes and reservoirs. The Oregon Lake Watch Program (OLWP), a citizen science volunteer based program, was created to help protect these natural resources. Specifically, the goal of the OLWP is to help protect Oregon’s lakes and reservoir through having citizen volunteers survey for invasive species and gather water quality data, and then disseminating this information to the public and resource managers.

This OLWP training manual provides protocols for collecting important water quality data, surveying for invasive plants and animals, photo documentation and preservation of invasive species, and recording …

Multi-Dimensional Drought Risk Assessment Based On Socio-Economic Vulnerabilities And Hydro-Climatological Factors, Ali Ahmadalipour

Dissertations and Theses

Drought is among the costliest natural hazards developing slowly and affecting large areas, which imposes severe consequences on society and economy. Anthropogenic climate change is expected to exacerbate drought in various regions of the globe, making its associated socioeconomic impacts more severe. Such impacts are of higher concern in Africa, which is mainly characterized by arid climate and lacking infrastructure as well as social development. Furthermore, the continent is expected to experience vast population growth, which will make it more vulnerable to the adverse effects of drought. This study provides the first comprehensive multi-dimensional assessment of drought risk across the …

Assessing The Impact Of Land Use And Travel On Carbon Dioxide Emissions In Portland, Oregon, Zakari Mumuni

Dissertations and Theses

The negative consequences of sprawling metropolitan regions have attracted attention in both academia and in practice regarding how to better design settlements and alter travel behavior in a quest to curtail vehicle emissions. Studies that have attempted to understand the nexus between land use, travel and vehicle emissions have not been able to address the issue of self-selection in a satisfactory manner. Self-selection occurs when households choose their residential location based, in part, on expected travel behavior. This non-random experience makes the use of traditional regression frameworks that strongly rely on random sampling, unsuitable. This replication study's purpose was to …

A Comparative Assessment Of Projected Meteorological And Hydrological Droughts: Elucidating The Role Of Temperature, Ali Ahmadalipour, Hamid Moradkhani, Mehmet C. Demirel

Civil and Environmental Engineering Faculty Publications and Presentations

The changing climate and the associated future increases in temperature are expected to have impacts on drought characteristics and hydrologic cycle. This paper investigates the projected changes in spatiotemporal characteristics of droughts and their future attributes over the Willamette River Basin (WRB) in the Pacific Northwest U.S. The analysis is performed using two subsets of downscaled CMIP5 global climate models (GCMs) each consisting of 10 models from two future scenarios (RCP4.5 and RCP8.5) for 30 years of historical period (1970–1999) and 90 years of future projections (2010–2099). Hydrologic modeling is conducted using the Precipitation Runoff Modeling System (PRMS) as a …

The Influence Of Recurrent Modes Of Climate Variability On The Occurrence Of Monthly Temperature Extremes Over South America, Paul C. Loikith, Judah Detzer, Carlos R. Mechoso, Huikyo Lee, Armineh Barkhordarian

Geography Faculty Publications and Presentations

The associations between extreme temperature months and four prominent modes of recurrent climate variability are examined over South America. Associations are computed as the percent of extreme temperature months concurrent with the upper and lower quartiles of the El Niño–Southern Oscillation (ENSO), the Atlantic Niño, the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM) index distributions, stratified by season. The relationship is strongest for ENSO, with nearly every extreme temperature month concurrent with the upper or lower quartiles of its distribution in portions of northwestern South America during some seasons. The likelihood of extreme warm temperatures is enhanced …