Michael D. Dettinger

University of California, San Diego | UCSD · Scripps Institution of Oceanography (SIO)

JUNE 2015 Storage in California’s Reservoirs and Snowpack in This Time of Drought Michael D. Dettinger* and Michael L. Anderson 1 Volume 13, Issue 2 | June 2015 * Corresponding author: mddettin@usgs.gov; U.S. Geological Survey, La Jolla, CA 92093 USA and Scripps Institution of Oceanography, La Jolla, CA 92093 USA 1 Division of Flood Management, Cal...

The variability of water year precipitation and selected blue oak tree-ring chronologies in California are both dominated by heavy precipitation delivered during just a few days each year. These heavy precipitation events can spell the difference between surplus or deficit water supply and elevated flood risk. Some blue oak chronologies are highly...

Increased atmospheric evaporative demand has important implications for humans and ecosystems in water-scarce lands. While temperature plays a significant role in driving evaporative demand and its trend, other climate variables are also influential and their contributions to recent trends in evaporative demand are unknown. We address this gap with...

In this review, we provide guidance on the construction of climate scenarios for stress tests—scenarios that represent disruptive climatic events and can be used to assess the impacts of climate and weather risks at the level of detail that is necessary to identify specific adaptation actions or strategies. While there is a wealth of guidance on sc...

Climate change is causing rapid warming and altered precipitation patterns in mountain watersheds, both of which influence the timing of ice breakup in mountain lakes. To enable predictions of ice breakup in the future, we analyzed a dataset of mountain lake ice breakup dates derived from remote sensing and historical downscaled climate data. We ev...

Ensemble Forecast Operations (EFO) is a risk‐based approach of reservoir flood control operations that incorporates ensemble streamflow predictions (ESPs) made by the California‐Nevada River Forecast Center. Reservoir operations for each member of an ESP are individually modeled to forecast system conditions and calculate risk of reaching critical...

Abstract Observational networks enhance real‐time situational awareness for emergency and water resource management during extreme weather events. We present examples of how a diverse, multitiered observational network in California provided insights into hydrometeorological processes and impacts during a 3‐day atmospheric river storm centered on 1...

This chapter discusses the intensity of the precipitation ARs often bring, and their unique combinations of durations, geometries, winds, and temperatures which make ARs important and unique pieces of the climatology and landscapes that affect both natural systems and human societies. Mountains profoundly affect AR conditions and processes, for ins...

This chapter offers a brief overview of the science of atmospheric rivers (ARs), including the process that led to their formal definition, which now appears in the Glossary of Meteorology. From the 1970s through today, the emergence of the concept of the AR follows the trajectory of many scientific ideas in varied disciplines; observations of the...

This chapter reviews how AR research is being applied in real-world situations to address issues of flood planning and emergency intervention. It includes water supply management case studies. Examples comprise five distinct sections that show how AR research is being directly applied to the challenges that water managers, dam operators, crisis-man...

This volume’s four co-editors look toward the future of AR scholarship and applications, offering individual perspectives on what comes next. Gaps in current capabilities for observing and monitoring ARs (via ground-based, airborne, satellite, and reanalyses methods) are discussed for both applications and research. Emerging research directions inc...

Extraordinary precipitation events have impacted the United States (U.S.) recently, including hurricanes Harvey (2017) and Florence (2018), with 3-day precipitation totals larger than any others reported in the U.S. during the past 70 years. The R-CAT scaling method is used here to document extreme precipitation events and test for trends nationall...

This book is the standard reference based on roughly 20 years of research on atmospheric rivers, emphasizing progress made on key research and applications questions and remaining knowledge gaps. The book presents the history of atmospheric-rivers research, the current state of scientific knowledge, tools, and policy-relevant (science-informed) pro...

Water for the Seasons is a five-year collaborative research program in the Truckee-Carson River System that partnered an interdisciplinary research team with the Stakeholder Affiliate Group, which represents the diverse and competing municipal, industrial, agricultural, environmental and regulatory water management organizations from headwaters to...

Atmospheric rivers (ARs) significantly influence precipitation and hydrologic variability in many areas of the world, including the western U.S. As ARs are increasingly recognized by the research community and the public, there is a need to more precisely quantify and communicate their hydrologic impacts, which can vary from hazardous to beneficial...

The seasonal extent of the North American Monsoon (NAM) is highly variable and potentially sensitive to future climate change. Our objective was to determine how regional monsoonal patterns influence mountain precipitation near the NAM northwest boundary. Among the data we analyzed, a unique opportunity was provided by hourly observations collected...

Daily precipitation in California has been projected to become less frequent even as precipitation extremes intensify, leading to uncertainty in the overall response to climate warming. Precipitation extremes are historically associated with Atmospheric Rivers (ARs). Sixteen global climate models are evaluated for realism in modeled historical AR b...

We compare a novel dataset of San Francisco Bay Area landslides from 1871 to 2012 to corresponding atmospheric conditions commonly associated with Pacific winter storms and landfalling atmospheric rivers (ARs). Landslides in the San Francisco Bay Area occur primarily during winter months, coinciding with enhanced integrated water vapor transport (I...

We present hourly climate data to force land surface process models and assessments over the Merced and Tuolumne watersheds in the Sierra Nevada, California, for the water year 2010–2014 period. Climate data (38 stations) include temperature and humidity (23), precipitation (13), solar radiation (8), and wind speed and direction (8), spanning an el...

This fact sheet reports results from Water for the Seasons, a collaborative modeling research program that partners an interdisciplinary research team with water managers representing the diverse water-use communities in the Truckee-Carson River System in California and Nevada. The program aims to assess the climate resiliency of the river system t...

California is regularly impacted by floods and droughts, primarily as a result of too many or too few atmospheric rivers (ARs). This study analyzes a two-decade-long hourly precipitation dataset from 176 California weather stations and a 3-hourly AR chronology to report variations in rainfall events across California and their association with ARs....

Supporting Information S1

The California drought of 2012–2016 was a record-breaking event with extensive social, political, and economic repercussions. The impacts were widespread and exposed the difficulty in preparing for the effects of prolonged dry conditions. Although the lessons from this drought drove important changes to state law and policy, there is little doubt t...

Atmospheric rivers (ARs) play vital roles in the western United States and related regions globally, not only producing heavy precipitation and flooding, but also providing beneficial water supply. This paper introduces a scale for the intensity and impacts of ARs. Its utility may be greatest where ARs are the most impactful storm type and hurrican...

We present hourly climate data to force land surface process models and assessments over the Merced and Tuolumne watersheds in the Sierra Nevada, California, for the water year 2010–2014 period. Climate data (38 stations) includes temperature and humidity (23), precipitation (13), solar radiation (8), and wind speed and direction (8) spanning an el...

http://www.climateassessment.ca.gov/regions/docs/20180827-SierraNevada.pdf

Atmospheric rivers (ARs) come in all intensities, and clear communication of risks posed by individual storms in observations and forecasts can be a challenge. Modest ARs can be characterized by the percentile rank of their integrated water vapor transport (IVT) rates compared to past ARs. Stronger ARs can be categorized more clearly in terms of re...

In most Mediterranean climate (MedClim) regions around the world, global climate models (GCMs) consistently project drier futures. In California, however, projections of changes in annual precipitation are inconsistent. Analysis of daily precipitation in 30 GCMs reveals patterns in projected hydrometeorology over each of the five MedClm regions glo...

Atmospheric rivers (AR) have a significant role in generating floods across the western United States. We analyze daily streamflow for water years 1949 to 2015 from 5477 gages in relation to water vapor transport by ARs using a 6-hour chronology resolved to 2.5° latitude and longitude. The probability that an AR will generate 50 mm/day of runoff in...

Special Publication, University of Nevada Cooperative Extension (SP-17-05).

Gridded hourly precipitation observations over the conterminous U.S., from 1948 to 2002, are analyzed to determine climatological characteristics of storm precipitation totals. Despite generally lower hourly intensities, precipitation totals along the U.S. West Coast (USWC) are comparable to those in southeast U.S. (SEUS). Storm durations, more so...

https://eos.org/opinions/defining-snow-drought-and-why-it-matters

In the southwestern US, the meteorological phenomenon known as atmospheric rivers (ARs) has gained increasing attention due to its strong connections to floods, snowpacks and water supplies in the West Coast states. Relatively less is known about the ecological implications of ARs, particularly in the interior Southwest, where AR storms are less co...

In the southwestern US, the meteorological phenomenon known as atmospheric rivers (ARs) has gained increasing attention due to its strong connections to floods, snowpacks and water supplies in the West Coast states. Relatively less is known about the ecological implications of ARs, particularly in the interior Southwest, where AR storms are less co...

Water for the Seasons partners scientists with community stakeholders in the Truckee-Carson River System to explore new strategies and solutions for dealing with extreme climate events such as droughts and floods. Funded by a grant from the National Science Foundation and the U.S. Department of Agriculture, this four-year research and outreach prog...

doi: https://doi.org/10.15447/sfews.2016v14iss4art6The State of Bay–Delta Science 2008 highlighted seven emerging perspectives on science and management of the Delta. These perspectives had important effects on policy and legislation concerning management of the Delta ecosystem and water exports. From the collection of papers that make up the State...

The State of Bay-Delta Science 2008 highlighted seven emerging perspectives on science and management of the Delta. These perspectives had important effects on policy and legislation concerning management of the Delta ecosystem and water exports. From the collection of papers that make up the State of Bay-Delta Science 2016, we derive another seven...

Anthropogenic climate change amounts to a rapidly approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to cha...

Regions of complex topography and remote wilderness terrain have spatially-varying patterns of temperature and streamflow, but due to inherent difficulties of access, are often very poorly sampled. Here we present a dataset of distributed stream stage, streamflow, stream temperature, barometric pressure, and air temperature from the Tuolumne River...

First posted August 29, 2016 For additional information, contact: Director, California Water Science Center U.S. Geological Survey 6000 J Street, Placer Hall Sacramento, CA 95819 http://ca.water.usgs.gov Abstract California’s vast reservoir system, fed by annual snow-and rainfall, plays an important part in providing water to the State’s human and...

California precipitation varies more dramatically from year to year than elsewhere in the conterminous United States. This paper analyzes the extent to which contributions of the wettest days to overall precipitation dictate the state's precipitation seasonality and frequent multiyear periods of drought (as precipitation deficit) and plenty is anal...

The State of Bay-Delta Science 2016 (SBDS) is a collection of papers that summarizes the scientific understanding of the Sacramento-San Joaquin Delta, emphasizing progress made during the past decade. It builds on the first SBDS edition (Healey et al. 2008). Paper topics for this edition address the most relevant scientific issues in the Delta iden...

The western United States (the West) undergoes considerable hydrologic variability in response to regional climate fluctuations that are termed anomalous by climate scientists because they depart from long-term average conditions. Regional climate fluctuations persist for seasonal to multidecadal durations, usually in association with larger-scale...

The Western United States is vulnerable to socioeconomic disruption due to extreme winter precipitation and floods. Traditionally, forecasts of precipitation and river discharge provide the basis for preparations. Herein we show that earlier event awareness may be possible through use of horizontal water vapor transport (IVT) forecasts. Applying th...

In the Sierra Nevada mountains (USA), and geographically similar areas across the globe where human development is expanding, extreme winter storm and flood risks are expected to increase with changing climate, heightening the need for communities to assess risks and better prepare for such events. In this case study, we demonstrate a novel approac...

The western United States is a region long defined by water challenges. Climate change adds to those historical challenges, but does not, for the most part, introduce entirely new challenges; rather climate change is likely to stress water supplies and resources already in many cases stretched to, or beyond, natural limits. Projections are for cont...

The Scripps Institution of Oceanography International Atmospheric Rivers Workshop; La Jolla, California, 15–17 June 2015

Using water column temperature records collected since 1968, we analyzed the impacts of climate change on thermal properties, stability intensity, length of stratification, and deep mixing dynamics of Lake Tahoe using a modified stability index (SI). This new SI is easier to produce and is a more informative measure of deep lake stability than comm...

The variability of precipitation and water supply along the U.S. West Coast creates major challenges to the region’s economy and environment, as evidenced by the recent California drought. This variability is strongly influenced by atmospheric rivers (ARs), which deliver much of the precipitation along the U.S. West Coast and can cause flooding, an...

We review and comment upon some themes in the recent stream of critical commentary on the assertion that “stationarity is dead,” attempting to clear up some misunderstandings; to note points of agreement; to elaborate on matters in dispute; and to share further relevant thoughts. This article is protected by copyright. All rights reserved.

There is a great deal of interest in the literature on streamflow changes caused by climate change because of the potential negative effects on aquatic biota and water supplies. Most previous studies have primarily focused on perennial streams, and there have been only a few studies examining the effect of climate variability on intermittent stream...

Global warming of the Earth's atmosphere is hypothesized to lead to an intensification of the global water cycle. To determine associated hydrological changes, most previous research has used precipitation. This study, however, investigates projected changes to global atmospheric water vapor transport (integrated vapor transport (IVT)), the key lin...

Potential biogeomorphic benefits from intentional levee breaks and weir overflow on the managed floodplain-river system of California's Sacramento and San Joaquin River watershed (Central Valley) are discussed here. Prior to the nineteenth century, the system was characterized by natural levees alongside complex multichanneled rivers and tributarie...

The climatology of Colorado's historical extreme precipitation events shows a remarkable degree of seasonal and regional variability. Analysis of the largest historical daily precipitation totals at COOP stations across Colorado by season indicates that the largest recorded daily precipitation totals have ranged from less than 60 mm day-1 in some a...

Significance El Niño Southern Oscillation (ENSO) affects hydrological processes around the globe. However, little is known about its influence on the socioeconomic impacts of flooding (i.e., flood risk). We present, to our knowledge, the first global assessment of ENSO’s influence on flood risk in terms of economic damage and exposed population and...

We describe the expansion of a publicly available archive of downscaled climate and hydrology projections for the United States. Those studying or planning to adapt to future climate impacts demand downscaled climate model output for local or regional use. The archive we describe attempts to fulfill this need by providing data in several formats, s...

Background/Question/Methods Atmospheric rivers (ARs) are strongly linked to extreme winter precipitation events in the western U.S., accounting for ˜80% of extreme floods in the Sierra Nevada and surrounding lowlands. In 2010, the U.S. Geological Survey developed the ARkStorm extreme storm scenario for California to quantify risks from extreme wi...

Background/Question/Methods Downscaling is necessary to translate coarsely resolved global climate model (GCM) projections to regional and local changes. However, climatic extremes are often as important to ecosystems as long-term means, and often, means and the extremes are not tightly correlated. But downscaling efforts thus far have focused mo...

doi: http://dx.doi.org/10.15447/sfews.2014v12iss2art4 --SFEWS editors