CW3E Participates in Water in the West: A Science Policy Roundtable

CW3E Participates in Water in the West: A Science Policy Roundtable

December 10, 2016

CW3E was represented in a December 8, 2016 panel discussion hosted by UCSD’s School of Global Policy and Strategy (GPS)’s Science Policy Fellows Program and SIO’s Science Policy Discussion Group, titled “Water in the West: A Science Policy Roundtable”. The purpose of the event was to bring together our different communities and explore the sources of California’s water supply, how water supply can change, how it is used throughout the state and best practices for optimal regulation of its use.

CW3E director Dr. F. Martin Ralph acted as moderator. Other panel members were Dr. Jennifer Burney of GPS, Sandra Kerl of the San Diego County Water Authority, and Dr. Dan Cayan of SIO and a CW3E collaborator. Dr. Scott Sellars, the leader of the Science Policy Discussion Group, was involved in organizing the event. Other CW3E postdocs and graduate students assisted with logistics. The attendance was just over 100 people, with a very engaged audience. Questions were asked on topics ranging from specific projects run by the SD County Water Authority, to potential changes to academic funding sources with the incoming federal administration, to questions on groundwater and atmospheric rivers science. The event was recorded and can be viewed here.

More details are available in the GPS news story.

At podium: Marty Ralph (Scripps/CW3E); Left to right at table: Sandra Kerl (San Diego County Water Authority), Dan Cayan (Scripps/CW3E and USGS), Jennifer Burney (GPS)

Odds of Reaching 100% Water Year Precipitation – Dec Update

Odds of Reaching 100% of Normal Precipitation for Water Year 2017 (December Update)

December 9, 2016

Contribution from Dr. M.D. Dettinger, USGS

The odds shown here are the odds of precipitation in the rest of the water year (after November 2016) totaling a large enough amount to bring the water-year total to equal or exceed the percentage of normal listed. “All Yrs” odds based on monthly divisional precipitation totals from water year 1896-2015. Numbers in parenthesis are the corresponding odds if precipitation through October had been precisely normal (1981-2010 baseline).

Click here for a pdf file of this information.
 

 

 

How these probabilities were estimated:

At the end of a given month, if we know how much precipitation has fallen to date (in the water year), the amount of precipitation that will be required to close out the water year (on Sept 30) with a water-year total equal to the long-term normal is just that normal amount minus the amount received to date. Thus the odds of reaching normal by the end of the water year are just the odds of precipitation during the remaining of the year equaling or exceeding that remaining amount.

To arrive at the probabilities shown, the precipitation totals for the remaining months of the water year were tabulated in the long-term historical record and the number of years in which that precipitation total equaled or exceeded the amount still needed to reach normal were counted. The fraction of years that at least reached that threshold is the probability estimate. This simple calculation was performed for a full range of possible starting months (from November thru September) and for a wide range of initial (year-to-date) precipitation conditions. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, and 150%, to ensure that the resulting tables of probabilities cover almost the full range of situations that will come up in the future.

[One key simplifying assumption goes into estimating the probabilities this way: The assumption that the amount of precipitation that will fall in the remainder of a water year does not depend on the amount that has already fallen in that water year to date. This assumption was tested for each month of the year by correlating historical year-to-date amounts with the remainder-of-the-year amounts, and the resulting correlations were never statistically significantly different from zero, except possibly when the beginning month is March, for which there is a small positive correlation between Oct-Mar and Apr-Sept precipitation historically.]

Contact: Michael Dettinger (USGS)

CW3E partners with California Department of Water Resources, California Geological Survey, US Geological Survey, and the Western Regional Climate Center to assess post-fire debris flow hazards in northern California

CW3E partners with California Department of Water Resources, California Geological Survey, US Geological Survey, and the Western Regional Climate Center to assess post-fire debris flow hazards in northern California

December 2, 2016

Highlights

Atmospheric River knowledge and tools support post-fire debris flow hazard mitigation and fast-response studies of debris flow-meteorology linkages

An important consequence of the recent record drought in parts of California is the occurrence of major wildfires. The Butte, Valley and Soberanes fires occurred in the last 18 months and have been some of the largest in California history. These tragic burns caused many adverse impacts at the time, and continue to create natural hazards due to the increased risk of damaging debris flows that can occur after the rains return.

California’s burned steeplands are prone to hazardous debris flows during winter storms. Wildfires remove vegetation and alter soil properties, increasing the likelihood of debris flows, even for relatively low intensity storms. When rainfall of sufficient intensity and duration impacts recently burned steeplands, landslides and surface runoff can mobilize ash, rocks, and other material into debris flows that devastate life and property.

California’s Department of Water Resources (DWR) is sponsoring work to examine the role of Atmospheric Rivers on flooding and landslide occurrence and magnitude. The project is led by the Center for Western Weather and Water Extremes (CW3E) at Scripps Institution of Oceanography and includes a team of experts from Scripps, California Geological Survey (CGS) and the U.S. Geological Survey (USGS) Landslide Hazards Team.

Within these burn areas, the geology team, led by Jeremy Lancaster of CGS, is deploying sensors and making measurements in the burn areas when conditions warrant. Doing so requires making decisions on whether to make observations at a study site following a storm event. In support of this, CW3E Graduate Student researchers Nina Oakley and Meredith Fish are using new knowledge of weather systems capable of producing intense precipitation, especially Atmospheric Rivers, to evaluate the potential for high-intensity precipitation over the Soberanes Fire, Butte Fire, and Valley Fire burn areas to advise Lancaster. Key to these preparations and day-to-day decisions are the new Atmospheric River forecasting tools at CW3E. Additionally, post-storm, CW3E scientists will compile meteorological data relevant to the storm event such as maximum precipitation intensity, storm total precipitation, radar imagery, an evaluation of Atmospheric River variables, and any information unique to that storm. For events that produce a debris flow response, a more in-depth case study will be conducted combining both geologic and atmospheric information.

Figure 1: Map of three burn areas that we propose to assess: Soberanes, Valley, and Butte wildfires.

Synthesis of the information collected through these storm and debris flow response logs will provide insight to post-fire debris flow triggering rainfall thresholds across northern California and the meteorological conditions that produce such rainfall. This integrated approach of meteorologists and geologists working together to address the post-fire debris flow issue will help advance our knowledge of these potentially hazardous events. This knowledge will be incorporated into landslide/debris flow hazard outlooks that factor in both landscape conditions (e.g., fire) and meteorology (e.g., extreme precipitation from Atmospheric Rivers)

Figure 2: Debris flow deposits stopped by cement barriers outside the Big Sur Lodge in California. This event was triggered by rain falling on burned steeplands in 2009, near an area now burned again by the Soberanes wildfire. (credit: David Longstreth, CGS).


Figure 3: During Fall 2016, USGS and CGS researchers install a rain near Pfeiffer Falls in the Soberanes Fire burn area to measure the rainfall intensities that trigger post-fire debris flows.

Contacts: Jeremy Lancaster (CGS), Nina Oakley (DRI and CW3E), John Stock (USGS), F.M. Ralph (CW3E)

Congressional Briefing on “A New Frontier in Water Operations: Atmospheric Rivers, Subseasonal-to-Seasonal Predictions and Weather Forecasting Technology”

Congressional Briefing on “A New Frontier in Water Operations: Atmospheric Rivers, Subseasonal-to-Seasonal Predictions and Weather Forecasting Technology”

July 27, 2016

An interagency, cross-disciplinary team of experts recently convened in Washington to provide Congressional staff with a briefing on atmospheric rivers, subseasonal-to-seasonal precipitation prediction needs, and the benefits of enhanced predictive forecasting technology to the future of water management.

Attendees heard from a diverse panel of experts representing a broad spectrum of perspectives, including government engagement by the National Weather Service and the U.S. Army Corps of Engineers, scientific findings presented by the Scripps Institution of Oceanography, and regional impacts to stakeholders represented by the Western States Water Council.

This briefing highlighted CW3E’s major effforts on atmospheric river science, monitoring and predictions, and their application to possible new water management strategies, such as Forecast-Informed Reservoir Operations (FIRO; http://cw3e.ucsd.edu/FIRO/), which is co-led by CW3E’s Director, F. Martin Ralph. Roughly 40 people attended, including representatives of congressional offices, committees, ACWA, federal agencies and other groups.

Click here for a summary.

Contact: F. Martin Ralph (mralph@ucsd.edu)

Publication Notice: CalWater Field Studies Designed to Quantify the Roles of Atmospheric Rivers and Aerosols in Modulating U.S. West Coast Precipitation in a Changing Climate

CW3E Publication Notice

CalWater Field Studies Designed to Quantify the Roles of Atmospheric Rivers and Aerosols in Modulating U.S. West Coast Precipitation in a Changing Climate

November 28, 2016

Ralph F.M., K. A. Prather, D. Cayan, J.R. Spackman, P. DeMott, M. Dettinger, C. Fairall, R. Leung, D. Rosenfeld, S. Rutledge, D. Waliser, A. B. White, J. Cordeira, A. Martin, J. Helly, and J. Intrieri, 2016: CalWater Field Studies Designed to Quantify the Roles of Atmospheric Rivers and Aerosols in Modulating U.S. West Coast Precipitation in a Changing Climate. Bull. Amer. Meteor. Soc. 97, yyy-zzz. doi: 10.1175/BAMS-D-14-00043.1.

This paper summarizes the 8-year-long CalWater program of field studies, from planning to field operations and analysis efforts. It also summarizes the major motivations for the program as well as science gaps addressed, and serves as the standard reference for future CalWater analysis papers.

Contact: F. Martin Ralph (mralph@ucsd.edu)

Abstract

Quantifying the roles of atmospheric rivers and aerosols in modulating U.S. West Coast precipitation, water supply, flood risks and drought in a changing climate.

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 (AR), which deliver much of the precipitation along the U.S. West Coast and can cause flooding, and by aerosols (from local sources and transported from remote continents and oceans) that modulate clouds and precipitation. A better understanding of these processes is needed to reduce uncertainties in weather predictions and climate projections of droughts and floods, both now and under changing climate conditions.

To address these gaps a group of meteorologists, hydrologists, climate scientists, atmospheric chemists, and oceanographers have created an interdisciplinary research effort, with support from multiple agencies. From 2009-2011 a series of field campaigns (CalWater 1) collected atmospheric chemistry, cloud microphysics and meteorological measurements in California and associated modeling and diagnostic studies were carried out. Based on remaining gaps, a vision was developed to extend these studies offshore over the Eastern North Pacific and to enhance land-based measurements from 2014-2018 (CalWater 2). The data set and selected results from CalWater 1 are summarized here. The goals of CalWater-2, and measurements to date, are then described.

CalWater is producing new findings and exploring new technologies to evaluate and improve global climate models and their regional performance and to develop tools supporting water and hydropower management. These advances also have potential to enhance hazard mitigation by improving near-term weather prediction and subseasonal and seasonal outlooks.

Publication Notice: Forecasting Atmospheric Rivers during CalWater 2015

CW3E Publication Notice

Forecasting Atmospheric Rivers during CalWater 2015

November 22, 2016

Cordeira, J., F. Ralph, A. Martin, N. Gaggini, R. Spackman, P. Neiman, J. Rutz, and R. Pierce, 0: Forecasting Atmospheric Rivers during CalWater 2015. Bull. Amer. Meteor. Soc., 0, doi: 10.1175/BAMS-D-15-00245.1.

As part of CW3E’s mission and goals a new set of atmospheric river (AR)-focused diagnostic and prediction tools have been created, in close partnership with Plymouth State University’s Prof. Jason Cordeira, and building upon work done earlier at NOAA under the HMT Program (see Ralph et al. 2013 BAMS, Wick et al. 2013 Wea. Forecasting). These developments were accelerated and focused by the needs for specialized AR forecast displays to support the CalWater field campaigns in 2014 and 2015 (see Ralph et al. 2016, BAMS). CalWater used research aircraft to observe atmospheric rivers and carried out aerosol science. These developments are summarized in a paper on the forecasting tools that were used in the CalWater field campaign by CW3E researchers and collaborators (Cordeira et al.) that was recently published in Bulletin of the American Meteorological Society (BAMS). The paper details some of the new AR forecasting tools developed using NCEP Global Forecast System and Global Ensemble Forecast System. A novel AR landfall detection forecast tool illustrates the probability of AR conditions at different locations along the western coast of the US. Another new forecast tool that used the various ensemble members illustrates the possible range of integrated water vapor transport (IVT) at a specific location using each of the ensemble members. In addition, the high quality plots of forecasted IVT and observed integrated water vapor supported the CalWater field campaign. Beyond supporting the CalWater Field Campaign, these new forecasting tools will likely improve AR forecasting throughout the West Coast. All these and more of the new forecasting tools can be found on the CW3E website under “Atmospheric River Resources.”

84-h NCEP GFS gridded forecast of IVT magnitude (kg m-1s-1 and direction; initialized at 1200 UTC on 3 February 2015; (b) as in (a), except for the verifying analysis of IVT magnitude and direction at 0000 UTC 7 February 2015 with overlaid draft flight track of the NOAA G-IV aircraft (c) GPS-derived IWV (mm) at 0015 UTC 7 February 2015.


Abstract

Atmospheric Rivers (ARs) are long and narrow corridors of enhanced vertically integrated water vapor (IWV) and IWV transport (IVT) within the warm sector of extratropical cyclones that can produce heavy precipitation and flooding in regions of complex terrain, especially along the U.S. West Coast. Several field campaigns have investigated ARs under the “CalWater” program of field studies. The first field phase of CalWater during 2009–2011 increased the number of observations of precipitation and aerosols, among other parameters, across California and sampled ARs in the coastal and near-coastal environment, whereas the second field phase of CalWater during 2014–2015 observed the structure and intensity of ARs and aerosols in the coastal and offshore environment over the Northeast Pacific. This manuscript highlights the forecasts that were prepared for the CalWater field campaign in 2015 and the development and use of an “AR portal” that was used to inform these forecasts. The AR portal contains archived and real-time deterministic and probabilistic gridded forecast tools related to ARs that emphasize water vapor concentrations and water vapor flux distributions over the eastern North Pacific, among other parameters, in a variety of formats derived from the NCEP Global Forecast System and Global Ensemble Forecast System. The tools created for the CalWater 2015 field campaign provided valuable guidance for flight planning and field activity purposes, and may prove useful in forecasting ARs and better anticipating hydrometeorological extremes along the U.S. West Coast.

Click here for personal use PDF file

Points of contact: Jason Cordeira, F. Martin Ralph, Brian Kawzenuk

CW3E Hosts Winter Outlook Workshop with California DWR

CW3E Hosts Winter Outlook Workshop with California DWR

November 18, 2016

The California Department of Water Resources (CDWR) and CW3E led a working meeting with researchers at the Scripps Institution of Oceanography in La Jolla, November 16-18, 2016. The workshop focused on efforts to improve sub-seasonal to seasonal prediction of precipitation, which could help agencies better manage water resources.

“We’d all like to know if 2017 will be wet or dry, but determining that is scientifically difficult. We’re trying to emphasize the need for prioritizing this research in the science community,” said Jeanine Jones, Interstate Resources Manager at CDWR.

Participants from the following agencies were in attendance: CW3E/Scripps, CDWR, Sonoma County Water Agency (SCWA), National Center for Atmospheric Research (NCAR), Natonal Weather Service (NWS), Western States Federal Agency Support Team (WestFAST), National Oceanic and Atmospheric Administration (NOAA), Plymouth State University (PSU), Oregon State University (OSU), University of California, Los Angeles (UCLA), Salt River Project (SRP), Climate Assessment for the Southwest (CLIMAS), Desert Research Institute (DRI), and Metropolitan Water District of Southern California (MWD).

Images courtesy DWR Photography – Florence Low

Water Year 2016 Summary

Water Year 2016 Summary

October 15, 2016

CW3E provides a summary of the top ten precipitation events based on the Northern Sierra 8-Station index during Water Year 2016 (Oct. 1 2015 – Sep. 30 2016). The top ten events occurred over a total of 27 days, and resulted in 30.09 inches of precipiation representing 51.89% of total water year precipitaiton and 60.2% of normal water year precipitation. All events were associated with an Atmospheric River (AR), with 6 considered strong ARs (IVT >750 kg m-1) s-1. For event specific reports refer to the CW3E News Page. For up to date AR forecasts and analysis visit the CW3E AR Portal.

Click here for a pdf file of this information.


 

 

 

 

 

Summary provided by B. Kawzenuk, and F.M. Ralph

IARC 2016

The First International Conference on Atmospheric Rivers (IARC) is Being Hosted by the Center for Wester Weather and Water Extremes (CW3E) at the Scripps Seaside Forum from 8-11 August 2016

August 8, 2016

IARC is part of a multi-year effort led by CW3E’s Director F. Martin Ralph, Mike Dettinger of USGS and David Lavers of ECMWF to foster collaboration and exchange of ideas on atmospheric rivers (AR).

  • The first event was held in June 2015 and brought together about 30 key individuals in a workshop, with a special emphasis on identifying the relationships between ARs, warm conveyor belts, and tropical moisture exports, all phenomena involving horizontal water vapor transport. A brief workshop synopsis is available in EOS (Dettinger et al. 2015) and here. Two main directions emerged:
    • 1) agreement that it was time to develop a comprehensive monograph on ARs, and
    • 2) an atmospheric river focused conference should be organized.
  • The second event in this 3-year effort is the 2016 IARC conference held from 8-11 August (described below; agenda).
  • The third event is a summer colloquium intended for summer 2017 at Scripps. It is intended to bring together at Scripps authors of the AR Monograph Book Chapters and graduate students from around the world for roughly 3 weeks of lectures and mentored mini-research efforts.

Woven through this series of events over 3 years is the development of the AR Monograph, which has been funded by a grant, including publication by University of California Press. IARC brings together most of the Chapter authors, at a point in the writing where new ideas garnered during the conference can be incorporated into the Monograph. The goal is then to have the Monograph finalized and in print for the AR Summer Colloquium. A technical editor, Lauren Muscatine (and her experienced team from UC Davis), is supporting preparation of the Monograph.

IARC received 75 abstracts from people around the world studying ARs, their impacts and applications of AR information to decision making. Submissions represent work on 6 continents plus Greenland. It has been planned by an international steering committee of experts on the subject. 90 people have registered for the conference, which will include several invited presentations, oral sessions, a poster session, panels on “applications to decision making,” “converging on a definition of atmospheric rivers” and on “future directions.” Breakout sessions will be held on “AR Forecasting,” “AR Book Chapters” and on “ARs in future climates and subseasonal to seasonal prediction.”

Sessions are organized around the following themes, which represent sections in the AR Monograph:

  • AR Applications
  • Global and Regional Perspectives
  • Observing and detecting ARs
  • Impacts of ARs
  • Theory, Structure and Processes
  • Modeling methodologies

Contact: F. Martin Ralph (mralph@ucsd.edu)

Publication Notice: Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet

CW3E Publication Notice

Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet

July 18, 2016

Ralph, F.M., J.M. Cordeira, P.J. Neiman and M. Hughes, 2016: Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet. J. Hydrometeor., 17, 1904-1915.

The top 0.3% most extreme daily precipitation events in the key Sacramento River watershed all involved both a landfalling atmospheric river and a Sierra Barrier Jet. Thus, forecasts of extreme precipitation are related to the skill of forecasts of each of these key phenomena, and can be enhanced by evaluation of, and enhancement of, skill in predicting each of these key processes. This study was led by the CW3E Director, was supported by the California Department of Water Resources, used data from NOAA’s Hydrometeorology Testbed collected over a decade, and epitomizes the focus of the “Center for Western Weather and Water Extremes,” and its partnership with NOAA Research’s Physical Sciences Division and Plymouth State University.

Contact: F. Martin Ralph (mralph@ucsd.edu)

Abstract

The upper Sacramento River watershed is vital to California’s water supply and is susceptible to major floods. Orographic precipitation in this complex terrain involves both atmospheric rivers (ARs) and the Sierra barrier jet (SBJ). The south-southeasterly SBJ induces orographic precipitation along south-facing slopes in the Mt. Shasta–Trinity Alps, whereas landfalling ARs ascend up and over the statically stable SBJ and induce orographic precipitation along west-facing slopes in the northern Sierra Nevada. This paper explores the occurrence of extreme daily precipitation (EDP) in this region in association with landfalling ARs and the SBJ. The 50 wettest days (i.e., days with EDP) for water years (WYs) 2002–11 based on the average of daily precipitation from eight rain gauges known as the Northern Sierra 8-Station Index (NS8I) are compared to dates from an SSM/I satellite-based landfalling AR-detection method and dates with SBJ events identified from nearby wind profiler data. These 50 days with EDP accounted for 20% of all precipitation during the 10-WY period, or 5 days with EDP per year on average account for one-fifth of WY precipitation. In summary, 46 of 50 (92%) days with EDP are associated with landfalling ARs on either the day before or the day of precipitation, whereas 45 of 50 (90%) days with EDP are associated with SBJ conditions on the day of EDP. Forty-one of 50 (82%) days with EDP are associated with both a landfalling AR and an SBJ. The top 10 days with EDP were all associated with both a landfalling AR and an SBJ.