Atmospheric Rivers: Recent Developments and Applications in California

Atmospheric Rivers: Recent Developments and Applications in California

May 19, 2017

In Sacramento on Tuesday, May 23rd, CW3E director, F. Martin Ralph will be presenting a seminar about atmospheric rivers and their impacts to California legislative and agency staff. The seminar, Atmospheric Rivers: Recent Developments and Applications in California, will provide updates on the impacts of ARs on the current water year and the ongoing research to better understand and better forecast ARs. Dr. Ralph is looking forward to sharing all of the exciting research being done at CW3E with the group.

CW3E Outreach at Local Elementary School

CW3E Outreach at Local Elementary School

May 15, 2017

CW3E’s Brian Kawzenuk, Chad Hecht, and Anna Wilson recently visited La Costa Meadows Elementary School to discuss some of the unique observations and tools that meteorologists use to study the atmosphere. Over 1000 students from kindergarten to fifth grade joined to observe and discuss meteorological ground instrumentation and a weather balloon launch. Discussion focused on how the instrumentation works, what they measure, how the observations can be useful to understanding the atmosphere, and how this knowledge and research can be used to improve forecasting and water resource management. During the demonstration students were actively engaged, asked numerous questions, and two assisted in releasing the weather balloon.

After the balloon launch, fourth and fifth grade students were invited to a more in depth discussion and presentation on meteorology, which focused on several aspects that are related to their science curriculum. Topics covered included data gathered from radiosonde launches, radar and satellite observations, storm systems and fronts, and forecasting and atmospheric models. This discussion gave students the opportunity to discuss and ask more questions about the atmosphere and how it is studied. Overall, the event proved to be a valuable experience for both students and staff.

Left: Anna Wilson and Chad Hecht prepare a radiosonde and weather balloon at La Costa Meadows Elementary School. Right: Brian Kawzenuk describes the process of performing a weather balloon launch while Chad and Anna prepare to hand off the balloon and radiosonde to two students.

Graduate Student Tashiana Osborne Represents UCSD at the California State Capitol

Graduate Student Tashiana Osborne Represents UCSD at the California State Capitol

May 3, 2017

CW3E graduate student, Tashiana Osborne, and Communication graduate student, Jahmese Fort, were selected to represent the University of California San Diego (UCSD) at the California State Capitol for the eighth annual UC Graduate Research Advocacy Day on April 19, 2017.

During their day at the state capitol, Osborne and Fort met face-to-face with several state senators, assembly members, and their staff. UC President Janet Napolitano addressed student representatives gathered from all 10 UC campuses during the event. Students engaged with legislators representing both major parties about ways their research projects contribute to making a difference for the lives of Californians and beyond.

Osborne highlighted implications of her research with CW3E, which focuses on investigating and enhancing forecasts of the atmospheric freezing level, the elevation where the air temperature is zero degrees Celsius. Frozen precipitation typically melts to become rain about 200-300 meters below this elevation. Freezing level, therefore, is key in determining the type and amount of precipitation, and ultimately, the amount of runoff generated during and after precipitation events. Freezing level is especially critical in California’s mountainous regions, where precipitation has a unique interaction with the complex and varied topography.

Her work supports the University’s goal to demonstrate the value and impact of UC research and graduate education for California. This research emphasizes the lead role California can have in western weather prediction and monitoring, water resources management, flood safety, and drought preparedness.

Fort and Osborne were also named as the inaugural recipients of the Jane and Jiao Fan, PhD ’94 Prize for Best Advocate for Graduate Studies through the Graduate Division. This prize honors graduate student representatives who are successful in marketing and communicating their own research efforts.

UC President, Janet Napolitano, and graduate student, Tashiana Osborne, at the California State Capitol. Photo credit: Denise Serrano; UCSD Director of Public Affairs.

CW3E Welcomes Dr. Zhenhai Zhang

CW3E welcomes Dr. Zhenhai Zhang

April 21, 2017

Dr. Zhenhai Zhang joined CW3E as a Postdoctoral Scholar in January 2017. Zhenhai earned his Ph.D. in Atmospheric Science at the State University of New York at Stony Brook under the direction of Dr. Brian Colle. His dissertation focused on the future changes of U.S. East coast extratropical cyclones using the Coupled Model Intercomparison Project Phase 5 (CMIP5) models and the downscaled Weather Research and Forecasting (WRF) runs. His work quantified the increase in the number of rapidly deepening storms along the East Coast, as well as increases in the associated precipitation extremes. In addition, he also used the WRF to dynamically downscale the results from global CMIP5 models for both the current and future climate. In his new position at CW3E, Zhenhai will develop a new tool to identify and composite different kinds of extratropical cyclones over the west coast of North America, and examine the interactions between the cyclones and atmospheric rivers, as well as their impacts on precipitation. He will also evaluate the seasonal predictability of temperature over the U.S. West Coast in the hindcast experiments of two multimodel ensemble projects (NMME and S2S), and build a surface temperature forecast at subseasonal to seasonal time scale using the ensemble real-time forecast from these models based on their forecast skill. Dr. Zhang’s research involves a collaboration with the California-Nevada Applications Program (CNAP).

CW3E Launches Radiosonde with Potter Valley Elementary School Students

CW3E Launches Radiosonde with Potter Valley Elementary School Students

April 16, 2017

CW3E’s Reuben Demirdjian and Anna Wilson recently conducted a demonstration radiosonde launch at the Potter Valley Fire Department for the Potter Valley Elementary School in the Russian River Watershed. The 5th and 6th grade classes, taught by Lori Clark and Merri Emerson respectively, were very enthusiastic participants in the demonstration launch. During the event the students showed their interest while asking a seemingly endless supply of questions about how the information is collected and why it it is useful. The students wrote a message on the to be launched radiosonde’s plastic exterior (Go Bearcats!), and released the balloon. Topics covered included the research done with the collected data, how the information gained from our experiments might help their strong agricultural community, why the balloon expands as it rises, what the sensors attached to the balloon measure, and how far the balloon might go (atmospheric layers were discussed!). Reuben and Anna, along with CW3E’s Douglas Alden, were also able to interact with the same classes at the start of the 2017 field season in January, when they deployed ground instrumentation including a vertically pointing radar, optical disdrometers, rain gauges, and more instrumentation at the Potter Valley Fire Department. The instrumentation at the Potter Valley Fire Department site has collected a valuable dataset over this historic winter season and CW3E is grateful for the support and collaboration and looks forward to a strong relationship going forward.

CW3E graduate student Reuben Demirdjian gets ready to hand off the radiosonde and balloon to two capable Potter Valley Elementary School students to sample a vertical profile of the atmosphere; Potter Valley Elementary School students watch the balloon ascend.

CW3E Welcomes Dr. Minghua Zheng

CW3E welcomes Dr. Minghua Zheng

January 16 2017

Dr. Minghua Zheng started at CW3E in January 2017 as a Postdoctoral Scholar. Minghua received her Ph.D. in Atmospheric Sciences from the State University of New York at Stony Brook under the advisement of Dr. Edmund Chang. Her dissertation focused on understanding the growth of forecast errors and uncertainties in ensemble forecasting of U.S. East Coast winter storms. Specifically, her research used ensemble sensitivity analysis, a data mining method, the Ensemble Transform Kalman Filter (ETKF), and other statistical tools to investigate the predictability of winter storms and to improve forecast skill. In addition, she investigated the role of large-scale processes, such as Rossby wave packet behavior, on the predictability of winter storms. In her new position, she will work on real-time data assimilation in CW3E’s “West-WRF” model using the Data Assimilation Research Testbed (DART) and four-dimensional variational (4DVAR) system. The assimilation will be used to estimate the model biases, improve initial conditions, and identify the sources of forecast errors and uncertainties associated with Atmospheric River events.

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)

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


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;, 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 (

CW3E Welcomes Dr. Forest Cannon

CW3E welcomes Dr. Forest Cannon

October 17, 2016

Dr. Forest Cannon joined CW3E as a Postdoctoral Scholar in October 2016. Forest earned his Ph.D. in Geography at the University of California, Santa Barbara, under the direction of Dr. Leila Carvalho. His dissertation focused on understanding large-scale forcing of extreme orographic precipitation in High Mountain Asia, using in-situ and remote sensing observations as well as regional climate modeling. His interest in working on weather and climate problems that affect his home state of California motivated earlier collaboration with the National Weather Service on fire weather forecasting in Santa Barbara, and ultimately led to his desire to pursue research pertaining to California’s water resources, here at CW3E. In his new position, Forest will use advanced atmospheric profiling satellites to evaluate and improve the representation of clouds and precipitation in global and regional climate models during atmospheric river events affecting the western US, with the goal of advancing short-term predictability and long-term projectability of regional water extremes.