CW3E Tables at the Ecologik Program Summer Science Experience

CW3E Tables at the Ecologik Program Summer Science Experience

August 13, 2018

CW3E’s Anna Wilson hosted an interactive table display at the annual Ecologik Project Summer Science Experience hosted by the National Park Service at Cabrillo National Monument in San Diego, CA on August 3rd, 2018. Overall, the Ecologik Project (a collaboration between Cabrillo National Monument and the San Diego Central Library) is designed to connect the next generation of park stewards to the natural resources and science of Cabrillo National Monument, and provide the tools and context to empower the 21st century of environmental stewards in meaningful and relevant ways. The Summer Science Experience provides the opportunity for underrepresented young girls (ages 9-16) to explore careers in the natural and technical sciences. The last main day of the Summer Science Experience featured a cross section of female scientists from many disciplines, including neuroscience, biology, ecology, meteorology, and more, presenting an interactive slice of one aspect of their work to rotating small groups of program attendees.

The CW3E table showcased the Center’s research on atmospheric rivers (ARs) and their role in water resources and hydrology, including both providing beneficial water supply, and causing hazards such as floods and droughts. Attendees learned about the term “Atmospheric River” by viewing satellite animations of the associated clouds and precipitation during an AR event and referencing the narrow river-like transport of water vapor from the tropics using SSMI visualizations. The CW3E table featured a number of state-of-the-art observing tools, such as a rain gauge, soil moisture and temperature sensors, a radiosonde, and a dropsonde. Attendees were able to directly interact with CW3E scientist, Dr. Wilson, and with various types of instrumentation, gain an understanding of ARs and their impact on daily life, and learn about what research in atmospheric science, hydrology, and environmental engineering is like.

Ecologik Summer Science Experience attendees learning about how rain gauges work to measure precipitation brought by atmospheric rivers.

CW3E Publication Notice: The Gauging and Modeling of Rivers in the Sky

CW3E Publication Notice

The Gauging and Modeling of Rivers in the Sky

August 8, 2018

The first publication using dropsonde observations from the “Atmospheric River Reconnaissance” Program has just appeared in Geophysical Research Letters (Lavers et al. 2018). For a brief description of the AR Recon Program, which is co-led by CW3E’s Director, Marty Ralph, and NCEP’s Vijay Talapragada, with partners from NRL, ECMWF, NCAR and other universities, please see This paper also represents the first product from an interagency team focused on step-by-step exploration of the impact of the dropsondes through data assimilation and modeling tests.

It is titled “The Gauging and Modeling of Rivers in the Sky.” The analysis was led by ECMWF’s David Lavers, a leader in AR research and applications from Europe, and formerly a Postdoctoral Scholar at CW3E. The other authors are Mark Rodwell, David Richardson, and Florian Pappenberger from the European Centre for Medium-Range Weather Forecasts (ECMWF), James Doyle and Carolyn Reynolds from the Naval Research Laboratory, Vijay Tallapragada of NOAA/NCEP/Environmental Modeling Center, and CW3E director Marty Ralph.

The research undertook a diagnostics study into how well the ECMWF Integrated Forecasting system represents atmospheric rivers (ARs). Using observations from 319 dropsondes released during the AR Reconnaissance 2018 (AR Recon) campaign, the structure of ARs was shown to be well captured in the model, but the short range water vapor flux errors were ~22% of the mean observed flux. These errors are most related to uncertainties in low-level winds near the top of the planetary boundary layer (Fig. 1). The study hypothesizes that improved initialization of the forecasts, and thus water vapor flux forecasts, may be possible via extra observations of low level winds and water vapor from proposed future targeted airborne dropsonde campaigns and space-based observations.

Figure 1. (Figure 4 from Lavers et al., 2018): Uncertainty in IVT forecasts. (a) Scatterplot of the IVT in the 25 Ensemble of Data Assimilations background and observed realizations at the 319 dropsondes (n=7975). The linear correlation, mean error (ME; forecast-observed), standard deviation of the background forecasts (SDBG), standard deviation of the perturbed observations (SDOB), and the root mean square error (RMSE) are given. The 1:1 line is given in black, the linear regression line is in red, and the second degree polynomial line is in blue. (b) The relative change in IVT forecast standard deviation (%) compared to the forecast when replacing the forecast specific humidity q or winds uv at 925, 850, and 700 hPa levels with the unperturbed observation or unperturbed analysis value from the ensemble forecast system.

Lavers, D.A., M.J. Rodwell, D.S. Richardson, F.M. Ralph, J.D. Doyle, C.A. Reynolds, V. Tallapragada, and F. Pappenberger, 2018: The Gauging and Modeling of Rivers in the Sky. Geophysical Research Letters. doi:10.1029/2018GL079019.

CW3E Publication Notice: A 22-Year Climatology of Cool Season Hourly Precipitation Thresholds Conducive to Shallow Landslides in California

CW3E Publication Notice

A 22-Year Climatology of Cool Season Hourly Precipitation Thresholds Conducive to Shallow Landslides in California

July 31, 2018

CW3E collaborator Nina Oakley, along with CW3E director Mary Ralph and others recently published a study in the American Meteorological Society journal, Earth Interactions. The study is titled “A 22-Year Climatology of Cool Season Hourly Precipitation Thresholds Conducive to Shallow Landslides in California” and explores hourly rainfall observations throughout the state through the lens of precipitation as a trigger for shallow landslides.

Storm-triggered shallow landslides are a common hazard in California’s complex terrain. Where they mobilize into debris flows, they can have devastating impacts on life, property, and infrastructure. Most landslide-susceptible slopes require some amount of antecedent precipitation before intense rainfalls may generate the pore pressures thought to trigger shallow landslides. Post-wildfire debris flows, like the 9 January 2018 event in Montecito that claimed 23 lives, can be triggered by a host of other processes that involve direct runoff from hillslopes. All of these types of mass movements require moderate to high intensity rainfalls whose intensities exceed local infiltration rates. Our research is thus relevant to a broad category of geologic processes (landslides, runoff, runoff-generated debris flows, etc.) that threaten California’s welfare. There are implications of this work beyond landslides; results may inform reservoir operations, floodplain management, and public safety.

Historic records of landslide occurrence in California document many events within populated areas such as the San Francisco Bay Area and Transverse Ranges of southern California. There are far fewer records from outside these regions. One hypothesis for the distribution of observed landslides is that some areas of California do not frequently experience rainfall of sufficient intensities and durations to trigger shallow landslides. We tested this hypothesis by documenting where hourly rainfall in the cool season (October-May) in California met or exceeded published values thought to trigger landslides after a seasonal antecedent precipitation threshold has been met. The thresholds examined were 5, 10, 15 and 20 mm h-1 as well as 7.5 mm h-1 for 3h, and 5 mm h-1 for 6h. We also evaluated the relationship between these events and atmospheric rivers.

We develop an hourly precipitation data set for this analysis by applying quality control to a 147 Remote Automated Weather Stations (RAWS; across California over a 22-year period. Our analysis shows that stations with exposure to southerly atmospheric flow in the Coast and Transverse Ranges experience high numbers of over-threshold events at all intervals, coincident with areas with the greatest number of observed landslides. Our results also highlight areas where over threshold events frequently occur but landslide observations are lacking; one such region is the northwestern Sierra Nevada. In the regions experiencing the highest number of over-threshold events, approximately 60-90% (depending on threshold examined) are associated with atmospheric rivers. The number of over threshold events varies greatly both within a season and inter-annually, though the greatest frequency tends to coincide with the climatological wettest month of the year. Individual storm events commonly It is feature multiple over-threshold events, especially at lower intensities or multi-hour thresholds.

Our study brings together atmospheric scientists and geologists. Co-authors include Jeremy Lancaster and Stefani Lukashov from the California Geological Survey, Ben Hatchett and Shawn Roj form the Desert Research Institute/Western Regional Climate Center, and John Stock from the US Geological Survey. This study was supported by the California Department of Water Resources, the National Oceanic and Atmospheric Administration’s Climate Program Office through the California Nevada Applications Program, and the National Aeronautics and Space Administration through the Nevada NASA Space Grant Consortium.

Landslide observations and frequency of intense precipitation. Left: Shallow landslides compiled by the California Geological Survey are shown as black dots. Geomorphic provinces are overlain on the map. The four provinces most pertinent to the study are labeled. Right: Marker size indicates the number of precipitation events exceeding 15 mm h-1 during the October-May period 1995-2015 at each RAWS station. Marker color indicates the percentage of total 15 mm h-1 events associated with atmospheric river conditions.

Oakley, N.S., J.T. Lancaster, B.J. Hatchett, J. Stock, F.M. Ralph, S. Roj, and S. Lukashov, 2018: A 22-Year Climatology of Cool Season Hourly Precipitation Thresholds Conducive to Shallow Landslides in California. Earth Interact., 22, 1–35, ,

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 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 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.

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.

CW3E Director Featured in the Water Zone Podcast on KCAA San Bernardino

CW3E Director Featured in the Water Zone Podcast on KCAA San Bernardino

April 25, 2018

The Water Zone is a KCAA (Loma Linda, CA) radio show, hosted by Paul McFadden, that explores water issues in agriculture and farming from various perspectives to advance water conservation. The April 19, 2018 episode featured two notable guests: Dr. F. Martin Ralph, CW3E Director, and Dr. Thomas Philp, a Pulitzer Prize winning journalist who is the executive strategist for the Metropolitan Water District of Southern California.

Follow the link to listen: Information related to western weather and water can be heard during minutes 11-44 of the episode.