CW3E Graduate Student Selected to Participate in the 9th International High Performance Computing Summer School

CW3E Graduate Student Selected to Participate in the 9th International High Performance Computing Summer School

July 17, 2018

CW3E’s Meredith Fish was one of 80 graduate students and postdoctoral scholars selected to participate in the 9th International High Performance Computing Summer School in Ostrava, Czech Republic, which was held from 8-13 July 2018 at the IT4Innovations National Supercomputing Center. The school was sponsored by the Extreme Science and Engineering Discovery Environment (XSEDE), the Partnership for Advanced Computing in Europe (PRACE), the SciNet High Performance Computing (HPC) Consortium, and the RIKEN Advanced Institute for Computational Science. There she engaged in lectures and hands-on sessions on a variety of topics, including: HPC challenges, HPC programming proficiencies, performance analysis and profiling, data-intensive computing, data visualization and algorithmic approaches. She also had the opportunity to present her research on atmospheric river families to other HPC users focusing on the technical aspects of her work.

Group photo from the International High Performance Computing Summer School in July 2018

Meredith in front of the Technical University of Ostrava, which is a part of the IT4Innovations National Supercomputing Center.

CW3E Director Honored at California Extreme Precipitation Symposium

CW3E Director Honored at California Extreme Precipitation Symposium

July 10, 2018

The annual California Extreme Precipitation Symposium, a Floodplain Management Association project, was held this year on July 9, 2018 at the University of California, Davis. This year’s theme was Paleoclimate Insights for Planning Future Natural Resources in California. Slides from all presentations are available at:

Each year since 2004, a Special Recognition Award is presented to “highlight and honor the outstanding contributions of individuals and institutions that have supported and advanced the professions of meteorology, flood hydrology, and flood risk management. These professions share the public safety goal of protecting life and property from the ravages of flooding. Together these professionals provide the tools, information, and knowledge essential for forecasting flood events before they occur, estimating potential flood magnitudes and impacts used in designing flood risk reduction projects, and responding to floods when they occur. Each honoree contributed to making the people of California safer from flood events over their many years of service.” This year, that award was given to CW3E’s director, Dr. F. Martin Ralph. More details are available on the California Extreme Precipitation Symposium website:

From left, Gary Estes (CEPSYM Founder), Marty Ralph (CW3E), and Rob Hartman (RKH Consulting Services).

CW3E Publication Notice: Atmospheric River Tracking Method Intercomparison Project (ARTMIP): Project Goals and Experimental Design

CW3E Publication Notice

Atmospheric River Tracking Method Intercomparison Project (ARTMIP): Project Goals and Experimental Design

July 9, 2018

As research has expanded on ARs, new detection algorithms have been developed, and yet no detailed intercomparison has been made. To fill this gap, a grass roots “community” effort was organized to develop an approach to perform such a comparison, which is described in the recently published paper by Shields et al (2018). The community effort is called the Atmospheric River Tracking Method Intercomparison Project “ARTMIP.” It has been organized by a small, ad-hoc, planning committee, co-chaired by Christine Shields (NCAR) and Jon Rutz (NWS and CW3E), with Mike Wehner (DOE/LBNL), Ruby Leung (DOE/PNNL) and F. Martin Ralph (UCSD/SIO/CW3E) as its members. This team organized its first meeting with interested parties in May 2017, which was hosted and sponsored by CW3E at Scripps Institution of Oceanography (SIO).

The paper was published in Geoscientific Model Development and titled Atmospheric River Tracking Method Intercomparison Project (ARTMIP): Project Goals and Experimental Design ( This paper describes ARTMIP, an international community effort to understand and quantify the uncertainties in atmospheric river (AR) science due to the differences in detection algorithms. The goal of ARTMIP is to provide the weather forecasting and climate community with a deeper understanding of AR tracking, mechanisms, and impacts, through providing a framework with which to objectively compare detection schemes that can be fundamentally different. The paper describes the experimental design and timeline, and includes preliminary results that use the key metrics of frequency, intensity, duration, and precipitation attribution (For an example of preliminary results, see figure 1).

The project is divided into two tiers with different science objectives. The first tier consists of applying all participating algorithms to a common dataset, the MERRA-2 reanalysis, from 1980-2017. The second tier will be divided into subtopics and consist of sensitivity studies to different reanalysis datasets and to climate model data. A variety of precipitation datasets will also be used to assess uncertainties in AR impacts.

The ARTMIP project has been positively received by the AR community and has the potential to shape much of how AR science and detection is conducted. The project has steadily increased participation since the paper was first presented in the open-forum GMD Discussions. Participation in ARTMIP is open to any researchers with an AR detection algorithm or with interest in evaluating the data. If you are interested in participating, please contact Christine Shields ( or Jon Rutz (

Figure 1. Composite MERRA-2 IVT (kg m-1s-1) for landfalling ARs along North American west coast for 14 different algorithms. Time instances where an AR was detected along the coastline were composited for the entire region. Composite data is plotted for February 2017. To test the ARTMIP framework, a 1-month proof-of-concept trial was designed and performed for February 2017. This month was chosen due to large number of landfalling ARs that impacted western North America during this period.

Shields, C. A., Rutz, J. J., Leung, L.-Y., Ralph, F. M., Wehner, M., Kawzenuk, B., Lora, J. M., McClenny, E., Osborne, T., Payne, A. E., Ullrich, P., Gershunov, A., Goldenson, N., Guan, B., Qian, Y., Ramos, A. M., Sarangi, C., Sellars, S., Gorodetskaya, I., Kashinath, K., Kurlin, V., Mahoney, K., Muszynski, G., Pierce, R., Subramanian, A. C., Tome, R., Waliser, D., Walton, D., Wick, G., Wilson, A., Lavers, D., Prabhat, Collow, A., Krishnan, H., Magnusdottir, G., and Nguyen, P., 2018: Atmospheric River Tracking Method Intercomparison Project (ARTMIP): Project Goals and Experimental Design, Geosci. Model Dev.,

CW3E Hosts Student Workshop on AR Forecasting

CW3E Hosts Student Workshop on AR Forecasting

July 2, 2018

On Friday, June 29th, immediately following the 2018 International Atmospheric River Conference (IARC), students from over a dozen educational institutions within and outside of the United States gathered at Scripps to learn from the experts about AR forecasting. The goals of the workshop were to bring students together with AR scientists and forecasters to gain hands-on experience with predictions focused on practical and scientific applications. Outcomes for participants included improved understanding of modern AR prediction tools and methods, and how AR forecasting support selected examples of decision making.

Students first participated in an interactive lecture on AR predictions led by science leadership from the National Weather Service (NWS), the San Diego Swift Water Rescue Team, and CW3E, learning not only about the details of forecasting impacts of an AR but also about communication of risks to local stakeholders (Picture 1). Each student was provided with a NWS forecasting presentation that had previously been used to inform local stakeholders during a real event. The students were then given the task of providing an informed plan, from the standpoint of the local stakeholders, to mitigate the dangers associated to the AR event. This portion of the workshop highlighted the intricacies and difficulties that go into making forecast-informed decisions affecting local decisionmakers and municipalities and the importance of accurate forecasting tools.

Following this interactive lecture, students had the opportunity to use CW3E’s AR forecasting tools to try their hand at planning their own AR Recon airborne and on-the-ground field campaign. This portion of the workshop equipped students with an operational perspective on the AR Recon field campaign and difficulties associated with organizing a large-scale field campaign. Day two of the workshop began with a morning radiosonde balloon launch from the Scripps Pier (Picture 3), followed by a tour of the NWS San Diego forecast office. The NWS tour presented even more information on the operational side of forecasting and highlighted the ways that modern forecasts are communicated to local stakeholders. Students left the workshop eager for the next AR season when they’ll be able to test their skills in real-time! The student forecasting workshop was a great success and is being expanded next year to a colloquium covering all aspects of AR science in greater detail.

Just before releasing a radiosonde at Scripps Pier, workshop participants pose for a photo.

CW3E Publication Notice: The Role of Atmospheric Rivers in Extratropical and Polar Hydroclimate

CW3E Publication Notice

The Role of Atmospheric Rivers in Extratropical and Polar Hydroclimate

June 28, 2018

Deanna Nash (UC Santa Barbara) and CW3E collaborators Bin Guan (UCLA), Duane Waliser (NASA/JPL), along with CW3E director Marty Ralph and Hengchun Ye (Cal State LA) recently published a paper in Journal of Geophysical Research: Atmospheres, titled The Role of Atmospheric Rivers in Extratropical and Polar Hydroclimate.

Atmospheric Rivers (ARs) are narrow, long, transient, water vapor rich corridors of the atmosphere that are responsible for over 90% of the poleward water vapor transport in and across mid-latitudes. However, the role of ARs in modulating extratropical and polar hydroclimate features (e.g. water vapor content, precipitation) has not been fully studied, even though moistening of the polar atmosphere is both a key result of, and amplifier of, arctic warming and sea ice melt, and precipitation is key to the surface mass balance of polar sea ice and ice sheets. This study uses the MERRA2 reanalysis to characterize the roles of AR water vapor transport on the column-integrated atmospheric water vapor budget in the extratropical and polar regions of both hemispheres.

Meridional water vapor transport by ARs across a given latitude (examined for 40°, 50°, 60°, and 70°) is strongly related to variations in area-average (i.e. over the “cap” poleward of the given latitude) total water vapor storage and precipitation poleward of that latitude. For the climatological annual cycle, both AR transport (i.e., non-local sources) and total evaporation (i.e., local sources) are most correlated with total precipitation, although with slightly different phases. However, for monthly anomalies, the water budget at higher latitudes is largely dominated by the relationship between AR transport and precipitation. For pentad and daily anomalies, AR transport is related to both precipitation and water vapor storage variations. These results demonstrate the important role of episodic, extreme water vapor transports by ARs in modulating extratropical and polar hydroclimate.

Figure 1 from Nash et al. 2018. a) A schematic of the atmospheric water budget for a region poleward of a given latitude (e.g. 60ºN). The red arrows indicate flux of integrated water vapor transport (IVT), the majority of which is AR-related in the mid to high latitudes. The green arrows indicate the surface evaporation (E) of water poleward of a given latitude, and the clouds and rain indicate the loss of water vapor when it condenses and falls as precipitation (P). All these terms combine into equation 1 where the change in water vapor storage (∂IWV/∂t) is equal to the evaporation minus the precipitation in the region plus the flux of IVT into that region. b) A schematic showing a top down view of IVT and AR-IVT flux at 60°N. The majority of IVT and AR-IVT enter the Arctic via the red line regions (i.e. the AR-IVT Atlantic and Pacific Pathways).

Figure 10 from Nash et al., 2018. Correlation Ellipses between IVT and each variable (solid ellipse), and AR-IVT and each variable (translucent ellipse). The color of each ellipse indicates the correlation coefficient. The width of each ellipse is 1- |r|, and the orientation (downward/upward) indicates the sign of the relationship (positive/negative). The length of each ellipse is 1 (such that a circle would indicate zero correlation).

This research was supported by the NASA Energy and Water cycle Study (NEWS) program, NASA NCA, and NASA MIRO grant. Deanna Nash’s contribution to this study was made possible by NASA Jet Propulsion Laboratory’s Year-Round Internship Program during her graduate studies at California State University, Los Angeles. Please contact Duane Waliser at with inquiries.

Nash, D., Waliser, D., Guan, B., Ye, H., & Ralph, M. (2018). The Role of Atmospheric Rivers in Extratropical and Polar Hydroclimate. Journal of Geophysical Research: Atmospheres, 123.

2nd International Atmospheric Rivers Conference, June 2-28, 2018

2nd International Atmospheric Rivers Conference, June 25-28, 2018

June 22, 2018

The Center for Western Weather and Water Extremes (CW3E), at the Scripps Institution of Oceanography (SIO), UC San Diego, is hosting the 2nd International Atmospheric Rivers Conference (IARC) from June 25-28, 2018. Ths conference is organized by an international committee, with co-chairs from NASA’s Jet Propulsion Laboratory, the US Army Corps of Engineers, CW3E, and the University of Lisbon.

The conference is located at the seaside Robert Paine Scripps Forum for Science, Society, and the Environment on SIO’s campus. Over 100 experts across multiple fields are coming together to advance the state of the science and explore needs for new information. Fifteen student scholarships were given to students coming from locations such as India, Chile, and across the U.S. There will be extensive opportunity for interaction during the conference and after. A cocktail hour and dinner, included with registration, will be provided on Tuesday, June 26.

The agenda and other information can be found on the IARC website. Traditional oral and poster sessions are combined with panel discussions and breakout sessions. Sessions will be focused on various topics including: Winter 2016-2017; Airborne observations of atmospheric rivers (ARs); Subseasonal to seasonal forecasting of ARs; Applications and communications; AR Tracking; Regional perspectives on ARs; AR dynamics; AR microphysics, aerosols, and chemistry; Weather forecasting of ARs; ARs and Hydrologic Impacts; ARs and climate variability: past, present, and future; and Emerging directions.

Immediately after the conference, CW3E is also sponsoring a student forecasting workshop to be held June 29-30, with exercises planned on decision maker communication and forecasting for airborne field campaigns. Students will also be able to tour the National Weather Service San Diego offices and participate in a demonstration radiosonde launch from the Scripps Pier.

Weather, Water and Society on the Colorado River: CW3E Explores the Yampa River Basin

Weather, Water and Society on the Colorado River: CW3E Explores the Yampa River Basin

June 11, 2018

The Yampa River is one of the wildest remaining major tributaries of the Colorado River and supports a rich ecosystem, local agriculture and ranching, and a robust recreation industry. It also provides crucial water supplies to local stakeholders and locations as far removed as Arizona and Southern California. A multitude of environmental and societal needs influence water management and conservation decisions in the Yampa River, and are pertinent to other watersheds around the American West. Similarly, regional weather and climate extremes help shape the basin’s hydrology, environment, and water resources.

This June, CW3E travelled to Steamboat Springs, Colorado, for the Yampa Basin Workshop. This was a community-oriented event organized by CW3E and partners from Colorado Mountain College, Yampa Valley Sustainability Council, Friends of the Yampa, and Wyndham Resorts. During the Workshop, participants examined the Yampa River Basin through the lens of weather, environment, and culture. The workshop included talks by local experts, discussion panels, afternoon field learning, and a community event. After building a foundation on the region’s history and environment, we explored the various demands on the Yampa’s water, and learned how these needs are met and where challenges remain. This dialogue with the local community introduced graduate students, post-doctoral scholars, researchers, staff and faculty from CW3E to the Yampa Basin. Drawing from the community’s historical knowledge and expertise on the challenges and successes of conservation and use practices on the Yampa, the Workshop has prompted new research directions for CW3E that will support weather and water decision-making processes in the Colorado River Basin and California.

CW3E group photo on the Fetcher Ranch, June 7th, 2018. (Pictured left to right, Marty Ralph, Rachel Weihs, Lindsey Jasperse, Anna Wilson, Rob Hartman, Kara Voss, Douglas Alden, Meredith Fish, Brian Kawzenuk, Leah Campbell, Mike Sierks, Will Chapman, Ali Hamidi, Aneesh Subramanian, and Tamara Shulgina). Photo credit: Rachel Weihs

CW3E’s Anna Wilson chairs a panel discussion at the Yampa River Rendezvous at the Colorado Mountain College in Steamboat Springs, CO, June 5th, 2018. Pictured: Mike Meyers (National Weather Service), Jon Rutz (CW3E/NWS Western Region), Gannet Hallar (Storm Peak Lab, U. of Utah), Becky Bolinger (Colorado State University). Photo credit: Rachel Weihs

George Stanko (forefront) talks to the CW3E team on Stanko Ranch near the Yampa River, June 5th, 2018. Photo credit: Rachel Weihs

CW3E Staff Member Attends Russian River Science Forum

CW3E Staff Member Attends Russian River Science Forum

May 03, 2018

CW3E’s Anna Wilson recently attended the Russian River Science Forum, held at the Sonoma County Water Agency on May 1. The Forum was sponsored by the California Land Stewardship Institute, Sonoma County Agricultural Preservation and Open Space District, and Sonoma County Water Agency, and was meant to gather together scientists, conservationists, and stakeholders to discuss research needs and ongoing work being conducted in the watershed. The framework for the forum was research priorities identified by the Russian River Independent Science Review Panel (ISRP). Broadly, these priorities are: aquatic communities; groundwater; streamflow; climate change; water demand and use; geomorphology; and development of a numerical model of the watershed.

Presentations included ongoing relevant weather and climate research conducted by CW3E and partners (Anna Wilson, CW3E), local research applications (Jay Jasperse, Sonoma County Water Agency; Karen Gaffney, Sonoma County Agricultural Preservation and Open Space District), monitoring the effects of the 2017 wildfires (Jonathan Perkins, US Geological Survey; Virginia Mahacek, Sonoma County Office of Recovery and Resilience), and restoration design (Neil Lassettre, Sonoma County Water Agency). There was time for discussion regarding progress on the recommendations from the ISRP, and on future collaborations between interested researchers and stakeholders. CW3E looks forward to further partnerships towards advancing science objectives in the Russian River watershed and assisting in the development of science-based, resilient, and effective watershed management strategies.

CW3E Publication Notice: Global Analysis of Climate Change Projection Effects on Atmospheric Rivers

CW3E Publication Notice

Global Analysis of Climate Change Projection Effects on Atmospheric Rivers

May 24, 2018

Vicky Espinoza (UC Merced) and CW3E collaborators Bin Guan (UCLA), Duane Waliser (NASA/JPL), along with CW3E director Marty Ralph and David Lavers European Centre for Medium‐Range Weather Forecast, recently published a paper in Geophysical Research Letters, titled Global Analysis of Climate Change Projection Effects on Atmospheric Rivers.

Atmospheric rivers (ARs) are elongated strands of horizontal water vapor transport, accounting for over 90% of the poleward water vapor transport across midlatitudes. ARs have important implications for extreme precipitation when they make landfall, particularly along the west coasts of many midlatitude continents (e.g., North America, South America, and West Europe) due to orographic lifting. ARs are important contributors to extreme weather and precipitation events, and while their presence can contribute to beneficial rainfall and snowfall, which can mitigate droughts, they can also lead to flooding and extreme winds. This study takes a uniform, global approach that is used to quantify how ARs change between Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations and future projections under the Representative Concentration Pathway (RCP) 4.5 and RCP8.5 warming scenarios globally. The projections indicate that while there will be ~10% fewer ARs in the future, the ARs will be ~25% longer, ~25% wider, and exhibit stronger integrated water vapor transports under RCP8.5 (Figure 1). These changes result in pronounced increases in the frequency (integrated water vapor transport strength) of AR conditions under RCP8.5: ~50% (25%) globally, ~50% (20%) in the northern midlatitudes, and ~60% (20%) in the southern midlatitudes (Figure 2).

Figure 2 from Espinoza et al., 2018. AR frequency (shading; percent of time steps) and IVT (vectors; kg · m−1 · s−1) for (a) ERA‐Interim reanalysis for the historical period (1979–2002) with six green boxes depicting regions analyzed in Figures S2 and S3, (b) the MMM for the 21 CMIP5 models analyzed in this study for the historical period (1979–2002), (c) RCP4.5 warming scenario (2073–2096), and (d) RCP8.5 warming scenario (2073–2096).

This research was supported by the NASA Energy and Water cycle Study (NEWS) program. Vicky Espinoza’s contribution to this study was made possible by NASA Jet Propulsion Laboratory’s Year-Round Internship Program during her graduate studies at the University of Southern California. Please contact Duane Waliser at with inquiries. More information can be found from the NASA website

Espinoza, V., Waliser, D. E., Guan, B., Lavers, D. A., & Ralph, F. M. 2018: Global Analysis of Climate Change Projection Effects on Atmospheric Rivers. Geophysical Research Letters. 45.

CW3E Participates in the UP Summit at UC San Diego

CW3E Participates in the UP Summit at UC San Diego

May 20, 2018

CW3E participated in the inaugural UP Summit on May 17, to inspire a dialogue about how UC San Diego researchers are contributing to find solutions to environmental challenges.

This research to understand and protect the planet is a cornerstone of UC San Diego’s strategic research themes identified during the university’s strategic planning process in 2014. This plan identified where UC San Diego has the best experience and most potential for positively impacting society and the environment.

The invite-only audience at the UP Summit was comprised of a group that can take this research and turn it into action—political leaders, elected officials, agency and tribal representatives, non-profit partners and philanthropic supporters.

The summit featured two panel discussions on key issues affecting Southern California. The first was moderated by Mark Merrifield (Picture 1), director of the Center for Climate Change Impacts and Adaptation at Scripps Institution of Oceanography, and addressed extreme weather and atmospheric rivers, which can bring most of California’s water supply in only a few weather events a year, and pollution transport via the oceans and atmosphere. The panelists—coastal oceanographer Sarah Giddings, atmospheric chemist Kim Prather, and project scientist Aneesh Submaranian of the Center for Western Weather and Water Extremes—spoke on how their research is interconnected, and where more research needs to be done to understand complex problems.

Anna Wilson (Picture 2) and Douglas Alden also participated, hosting a table with a weather balloon (radiosonde) and other observational equipment. They talked to attendees about the types of observations that CW3E makes to improve understanding of California’s highly variable precipitation, particularly as applied to atmospheric rivers, and impacts on water supply and flooding.

According to event organizers, the goal of this summit was not just to show off the work that was done, but to foster a dialogue between the researchers and the policy makers. The approximately 100 attendees were given opportunities to network and converse throughout the event. The hope is that by learning more about what the science is capable of and what the community needs are, more solutions can be put into action to protect the planet for future generations.

More information about the summit can be found at thisweek@ucsandiego

CW3E Graduate Student Named AGU Voices for Science Advocate

CW3E Graduate Student Named AGU Voices for Science Advocate

May 21, 2018

Tashiana Osborne, a Ph.D. student within CW3E, was recently selected to become 1 of 30 American Geophysical Union (AGU) Voices for Science Advocates across the US. According to the AGU, their new program, Voices for Science, was ‘designed to create a network of skilled and dedicated scientists who are ready to share their science with a variety of important audiences’, including lawmakers, the media, community members, children, and others.

Osborne and other Advocates were flown to Washington, D.C. in April to complete a skill-building training in science communication and policy. During this training, Advocates created action plans, committing to create, contribute to, and/or engage peers in relevant activities throughout the year. AGU will reunite Advocates in Washington, D.C. for the December 2018 AGU Fall Meeting, where Advocates will share highlights from the year and participate in additional activities.

AGU emphasizes, ‘By participating in the Voices for Science program, the Advocates are helping to build public support for Earth and space science, protect critical science funding, and advance federal support for science policy. We look forward to sharing their success stories and lessons learned, and we hope they will serve as an inspiration for other AGU members to embark on their own science advocacy journeys.’

Voices for Science feature in AGU’s Earth & Space Science News (EOS):

AGU Voices for Science Advocates (within the Communication track) after practicing techniques to communicate research with various audiences (Photo Credit: AGU)

CW3E Undergraduate Student Presents Research at Conference

CW3E Undergraduate Student Presents Research at Conference

May 8, 2018

Cody Poulsen, is a soon to be graduate student with CW3E at Scripps Institution of Oceanography, UC San Diego. During his undergraduate career at UCSD he collaborated on a research project with ex-CW3E post-doc Scott Sellars. The project began during the summer of 2016 and was focused on using a program created by the Monterey Bay Aquarium Research Institute (MBARI) named Video Annotation Reference Systems (VARS) to produce useable meteorological metadata. VARS was created by MBARI to aid researchers in cataloguing the occurrences of biological species and geological formations in the large amounts of underwater footage collected by their ROVs. The research continued as part of Cody’s senior thesis during which he created an Atmospheric River metadata set with VARS. During the process, he learned more about the system and its capabilities. The metadata set is comprised of annotations for the location of AR landfall and center of AR events during the Water Years (WYs) 2001 and 2011. In addition, annotations for ARs with an associated Lower Level Jet (LLJ) structure where produced for both WYs. In the case study of WYs 2001 and 2011, the metadata depicted an anomalously high amount of landfalling AR events in California/Oregon for December 2010 juxtaposed to zero landfalling events along the North American West Coast excluding Alaska for December 2000. 500-hPa average wind speeds, heights, & direction plots for the two months where created to discern the general first principal flow that might explain the different AR trajectories. With these plots, it was found that a high-pressure ridge at 180° and low pressure trough at 140°W funneled ARs onto the California/Oregon coast for December 2010. Where December 2000 had a slight high pressure ridge along the coast to produce an insignificant blocking action leading to the assumption that some other synoptic features must be at play to produce the zero-event period.

Cody produced a poster on the VARS research project and presented it at the Association for Environmental Health and Sciences Foundation (AEHS), 28th Annual International Conference on Soil, Water, Energy, & Air, held in San Diego, CA. His research was presented at the conference’s 14th Annual Student Competition and was selected by the competition committee to receive the second-place award. In addition, to receiving the award Cody was invited to the AEHS appreciation dinner where he met with several industry professionals and researchers to network and discuss the future of the environmental field. Overall, the conference was a great experience for Cody to gain more presentation experience. In addition, he received valuable feedback from a wide range of individuals in the environmental field all with diverse backgrounds.

The VARS program is currently being used by Cody and CW3E post-doc Rachel Weihs to further study Atmospheric Rivers and their impacts on the western coast of the United States of America.

Odds of Reaching 100% Water Year Precipitation – May Update

Odds of Reaching 100% of Normal Precipitation for Water Year 2018 (May Update)

May 2, 2018

Contribution from Dr. M.D. Dettinger, USGS

Here is how we usually tend to see the water-year precip-drought to-date or last month’s contributions represented:

Figure 1: Total precipitation anomaly (large map) and total precipitation (smaller map) during water 2018 (September 2017-April 2018). Images courtesy PRISM Climate Group.

A somewhat different viewpoint on the development of drought considers how much precipitation has fallen (or not) AND how much is likely to fall in coming months, based on climatology. April 2018 produced precipitation over much of northern California and improved odds of reaching normal in some locales, but overall did little to undo the deficits of the previous months in a majority of the state. The following are maps of this year’s drought development that explicitly takes both of these aspects into account.

Here is how the drought has evolved so far this water year in terms of the odds of reaching 100% of normal precipitation by end of water-year 2018.

Figure 2: Odds of reaching 100% of water-year normal precipitation totals throughout water-year 2018.

  • Drought conditions have continued to develop across the Southwest, as odds of reaching normal have progressively dwindled month by month. Although April was wet over parts of northern California, it was—arguably—too little too late to set us up for reaching 100% of normal this year, in all but a few locales.

Figure 3 shows the current odds of reaching various fractions (including but not limited to 100%) of water-year-total this year (top row), as well as the corresponding odds prior to April (bottom row).
This approach offers a far different view than the precipitation anomalies of figure 1, emphasizing different “hot spots” of hope & despair.

Figure 3: Odds of water-year 2018 reaching various fractions of water year normal precipitation totals based on water year precipitation through April (top row) and prior to April (bottom row).

Finally, figure 4 is the “flipped” version of the analysis, asking-at each pixel-how large a water-year total precipitation has a 50% (and other exceedances) chance of being equaled or exceeded this year, as of May 1, 2018.

Figure 4: Chance of water-year total precipitation being equaled or exceeded this year.

  • A different color bar is used here to emphasize that the shades now are illustrating something quite different from the previous maps

How the probabilities above 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 (WY1948-2017 in these figures) 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. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, etc., for these figures.

[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 (across all climate divisions in California, so far) 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.]

Contact: Michael Dettinger (USGS)

CW3E Participates in Second ARTMIP Workshop

CW3E Participates in 2nd ARTMIP Workshop

April 26, 2018

The 2nd Atmospheric River Tracking Method Intercomparison Project (ARTMIP) Workshop was recently held in Gaithersburg, Maryland. The ARTMIP, started in 2017, is an effort to quantify the uncertainty in AR climatology, precipitation, and related impacts that arise because of different AR tracking methods, and how these AR-related metrics may change in the future. It also aims to provide guidance regarding the advantages and disadvantages of these different AR tracking methods, and which of these methods are best suited to answer certain scientific questions. Several members of CW3E are actively participating in ARTMIP and attended the workshop, including, Director Marty Ralph, Brian Kawzenuk, Aneesh Subramanian, Tamara Shulgina, and Anna Wilson.

The purpose and goals of the workshop were:

  • Discuss Tier 1 catalogues in context of science questions defined in the 1st ARTMIP workshop
  • Discuss Tier 1 analysis for the science overview paper
  • Discuss metrics, and adjust if necessary, and begin to formulate guidance on algorithmic choices based on Tier 1 results
  • Discuss and organize Tier 2 catalogue details and future studies

A main outcome from the workshop included the discussion of Tier 1 analysis and two publications from Tier 1. The first, an outline on the experimental design led by Christine Shields (NCAR), is currently under review with GMD. The second, led by Jon Rutz (NOAA), will provide overviews of the results from Tier 1. Another main outcome from the workshop was the discussion and planning of three publications from Tier 2 datasets: high-resolution climate change model runs, CMIP5 climate runs, and historical reanalyses comparison to the MERRA-2. At least eight other additional publications were discussed as well, including topics such as extreme precipitation, ENSO, ARs in polar regions, measures of internal variability, data resolution sensitivity, and more. Next steps for the ARTMIP include completion of the Tier 1 overview paper and beginning of Tier 2 catalog generation and analyses.

Workshop Participants (left to right): Jon Rutz (NOAA), Roger Pierce (NOAA), Ruby Leung (PNNL), Phu Nguyen (UC Irvine), Irina Gorodetskaya (Univ. Aveiro), Helen Griffith (Univ. Reading), Christine Shields (NCAR), Brian Kawzenuk (UCSD), Alexandre Ramos (Univ. Lisbon), Marty Ralph (UCSD), Juan Lora (UCLA), Gary Geernaert (DOE), Ashley Payne (Univ. Michigan), Elizabeth McClenny (UC Davis), Travis O’Brien (LBNL), Naomi Goldenson (UCLA), Daniel Walton (UCLA), Vitaliy Kurlin (LBNL), Aneesh Subramanian (UCSD), Tamara Shulgina (UCSD), Yang Zhou (Stony Brook Univ.), Bin Guan (UCLA), Renu Joesph (DOE), Michael Wehner (LBNL), Maximilliano Viale (Univ. Chile), Paul Ullrich (UC Davis; not pictured), Swen Brands (Meteogalicia; not pictured), Anna Wilson (UCSD; not pictured).

For more information on ARTMIP, visit the ARTMIP website.