Atmospheric rivers impact California's coastal water quality via extreme precipitation

Science of the Total Environment (Elsevier) | June 25th, 2019

Precipitation in California is projected to become more volatile: less frequent but more extreme as global warming pushes midlatitude frontal cyclones further poleward wh

Precipitation in California is projected to become more volatile: less frequent but more extreme as global warming pushes midlatitude frontal cyclones further poleward while bolstering the atmospheric rivers (ARs), which tend to produce the region's extreme rainfall. Pollutant accumulation and delivery to coastal waters can be expected to increase, as lengthening dry spells will be increasingly punctuated by more extreme precipitation events. Coastal pollution exposes human populations to high levels of fecal bacteria and associated pathogens, which can cause a variety of health impacts. Consequently, studying the impact of atmospheric rivers as the mechanism generating pulses of water pollution in coastal areas is relevant for public health and in the context of climate change. We aimed to quantify the links between precipitation events and water quality in order to explore meteorological causes as first steps toward effective early warning systems for the benefit of population health in California and beyond. We used historical gridded daily precipitation and weekly multiple fecal bacteria indicators at ~500 monitoring locations in California's coastal waters to identify weekly associations between precipitation and water quality during 2003–09 using canonical correlation analysis to account for the nested/clustered nature of longitudinal data. We then quantified, using a recently published catalog of atmospheric rivers, the proportion of coastal pollution events attributable to ARs. Association between precipitation and fecal bacteria was strongest in Southern California. Over two-thirds of coastal water pollution spikes exceeding one standard deviation were associated with ARs. This work highlights the importance of skillful AR landfall predictions in reducing vulnerability to extreme weather improving resilience of human populations in a varying and changing climate. Quantifying the impacts of ARs on waterborne diseases is important for planning effective preventive strategies for public health.

Atmospheric rivers impacting western North America in a world with climate intervention

Nature Portfolio (Springer Nature) | May 18th, 2022

Atmospheric rivers (ARs) impacting western North America are analyzed under climate intervention applying stratospheric aerosol injections (SAI) using simulations produce

Atmospheric rivers (ARs) impacting western North America are analyzed under climate intervention applying stratospheric aerosol injections (SAI) using simulations produced by the Whole Atmosphere Community Climate Model. Sulfur dioxide injections are strategically placed to maintain present-day global, interhemispheric, and equator-to-pole surface temperatures between 2020 and 2100 using a high forcing climate scenario. Three science questions are addressed: (1) How will western North American ARs change by the end of the century with SAI applied, (2) How is this different from 2020 conditions, and (3) How will the results differ with no future climate intervention. Under SAI, ARs are projected to increase by the end of the 21st century for southern California and decrease in the Pacific Northwest and coastal British Columbia, following changes to the low-level wind. Compared to 2020 conditions, the increase in ARs is not significant. The character of AR precipitation changes under geoengineering results in fewer extreme rainfall events and more moderate ones.

Atmospheric rivers in 20 year weather and climate simulations: A multi-model, global evaluation

American Geophysical Union (AGU) | June 1st, 2017

Atmospheric rivers (ARs) are narrow, elongated, synoptic jets of water vapor that play importantroles in the global water cycle and meteorological/hydrological extremes.

Atmospheric rivers (ARs) are narrow, elongated, synoptic jets of water vapor that play importantroles in the global water cycle and meteorological/hydrological extremes. Increasing evidence shows that ARs have signatures and impacts in many regions across different continents. However, global-scalecharacterizations of AR representations in weather and climate models have been very limited. Using a recently developed AR detection algorithm oriented for global applications, the representation of AR activities in multi-decade weather/climate simulations is evaluated. The algorithm is applied to 6-hourly(daily) integrated water vapor transport (IVT) from 22 (2) global weather/climate models that participated inthe Global Energy and Water Cycle Experiment Atmospheric System Study–Year of Tropical Convection Multimodel Experiment, including four models with ocean-atmosphere coupling and two models with super parameterization. Multiple reanalysis products are used as references to help quantify model errors inthe context of reanalysis uncertainty. Model performance is examined for key aspects of ARs (frequency,intensity, geometry, and seasonality), with the focus on identifying and understanding systematic errors insimulated ARs. The results highlight the range of model performances relative to reanalysis uncertainty inrepresenting the most basic features of ARs. Among the 17 metrics considered, AR frequency, zonal IVT, fractional zonal circumference, fractional total meridional IVT, and three seasonality metrics have consistently large errors across all models. Possible connections between AR simulation qualities and aspects of model configurations are discussed. Despite the lack of a monotonic relationship, the importance of model horizontal resolution to the overall quality of AR simulation is suggested by the evaluation results.

Attributing Extreme Events to Climate Change: A New Frontier in a Warming World

Cell Press | June 19th, 2020

The emerging field of extreme event attribution (EEA) seeks to answer the question: ‘‘Has climate change influenced the frequency, likelihood, and/or severity

The emerging field of extreme event attribution (EEA) seeks to answer the question: ‘‘Has climate change influenced the frequency, likelihood, and/or severity of individual extreme events?’’ Methodological advances over the past 15 years have transformed what was once an unanswerable hypothetical into a tractable scientific question—and for certain types of extreme events, the influence of anthropogenic climate change has emerged beyond a reasonable doubt. Several challenges remain, particularly those stemming from structural limitations in process-based climate models and the temporal and geographic limitations of historical observations. However, the growing use of large climate-model ensembles that capture natural climate variability, fine-scale simulations that better represent underlying physical processes, and the lengthening observational record could obviate some of these concerns in the near future. EEA efforts have important implications for risk perception, public policy, infrastructure design, legal liability, and climate adaptation in a warming world.

Attribution of declining western U.S. snowpack to human effects

American Meteorological Society (AMS) | December 1st, 2008

Observations show snowpack has declined across much of the western United States over the period 1950–99. This reduction has important social and economic impli

Observations show snowpack has declined across much of the western United States over the period 1950–99. This reduction has important social and economic implications, as water retained in the snowpack from winter storms forms an important part of the hydrological cycle and water supply in the region. A formal model-based detection and attribution (D–A) study of these reductions is performed. The detection variable is the ratio of 1 April snow water equivalent (SWE) to water-year-to-date precipitation (P), chosen to reduce the effect of P variability on the results. Estimates of natural internal climate variability are obtained from 1600 years of two control simulations performed with fully coupled ocean–atmosphere climate models. Estimates of the SWE/P response to anthropogenic greenhouse gases, ozone, and some aerosols are taken from multiple-member ensembles of perturbation experiments run with two models. The D–A shows the observations and anthropogenically forced models have greater SWE/P reductions than can be explained by natural internal climate variability alone. Model-estimated effects of changes in solar and volcanic forcing likewise do not explain the SWE/P reductions. The mean model estimate is that about half of the SWE/P reductions observed in the west from 1950 to 1999 are the result of climate changes forced by anthropogenic greenhouse gases, ozone, and aerosols.

Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in southern California

International Journal of Wildland Fire (CSIRO Publishing) | October 25th, 2022

California’s South Coast has experienced peak burned area in autumn. Following typically dry, warm summers, precipitation events and Santa Ana winds (SAWs) each occur w

California’s South Coast has experienced peak burned area in autumn. Following typically dry, warm summers, precipitation events and Santa Ana winds (SAWs) each occur with increasing frequency from autumn to winter and may affect fire outcomes. Aims. We investigate historical records to understand how these counteracting influences have affected fires. Methods. We defined autumn precipitation onset as the first 3 days when precipitation ≥8.5 mm, and assessed how onset timing and SAWs were associated with frequency of ≥100 ha fires and area burned during 1948–2018. Key results. Timing of autumn precipitation onset had negligible trend but varied considerably from year to year. A total of 90% of area burned in autumn through winter occurred from fires started before onset. Early onset autumns experienced considerably fewer fires and area burned than late onset autumns. SAWs were involved in many of the large fires before onset and nearly all of the lesser number after onset. Conclusions. Risk of large fires is reduced after autumn precipitation onset, but may resurge during SAWs, which provide high risk weather required to generate a large fire. Implications. During autumn before onset, and particularly during late onset autumns, high levels of preparation and vigilance are needed to avoid great fire impacts.

Benefit Accounting of Nature-Based Solutions for Watersheds Guide - Version 2

Pacific Institute | August 23rd, 2023

This guide helps users account for and measure the stacked water,1 carbon, biodiversity and socio-economic benefits of a Nature-Based Solution NBS project. Accounting for

This guide helps users account for and measure the stacked water,1 carbon, biodiversity and socio-economic benefits of a Nature-Based Solution NBS project. Accounting for these benefits will improve a company’s impact reporting and help build the business case for green solutions, thereby supporting widespread investment, implementation and upscaling of NBS. This work will increase awareness of the value of NBS, not only for ecosystem health and community development, but also for companies directly.

Benefit Accounting of Nature-Based Solutions for Watersheds Landscape Assessment

United Nations (UN) | August 3rd, 2020

This landscape assessment is the outcome of Phase 1 of a tri-phased project and was designed to inform the path forward for engaging the private sector to invest in natu

This landscape assessment is the outcome of Phase 1 of a tri-phased project and was designed to inform the path forward for engaging the private sector to invest in nature-based solutions (NBS). A literature review was undertaken to understand the contemporary thinking around NBS and identify key opportunities and challenges faced by decision makers, practitioners and researchers. Interviews conducted with representatives of businesses, civil society and academia who have already implemented NBS projects or are looking to do so yielded qualitative responses to complement or contrast with the findings from the literature review.

Big Ag, Big Oil, and the California Water Crisis

Food and Water Watch (FWW) | February 1st, 2023

Climate change is wreaking havoc on California’s water stability. The state is mired in long- term drought, punctuated by relatively brief periods of extreme precipitat

Climate change is wreaking havoc on California’s water stability. The state is mired in long- term drought, punctuated by relatively brief periods of extreme precipitation and catastroph- ic flooding. But the impacts of climate change on state water supplies only tell part of the story. Most of California’s water goes not for individual use, but instead to corporate agricul- tural and fossil fuel interests (Big Ag and Big Oil). These users reap tremendous profits, while more than 1 million Californians lack access to clean water.

Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem

Wiley | July 28th, 2022