Short diagnosis of development of a tropic surge, cut-off low and AR features

Short diagnosis of development of a tropic surge, cut-off low and AR features

December 2, 2014

Storm surge summary (slide 10; M. Ralph)

CW3E director Marty Ralph provides a short diagnosis of an interesting case with a variety of features coming together to generate very large IWV in this currently landfalling storm.

Dr. Ralph notes “This could be a useful event to diagnose more deeply given its relevance to many things we are working on, and the debates about AR, cut-off low, tropical moisture exports, etc. The IVT perspective needs to be explored as well, but the IWV features are quite telling. Jay Cordeira had shared a brief synopsis including a cross-section from GFS that showed the vapor transport over LA maximized at about 3.5 km, which may be more like a ‘tropical moisture export’ structure (Knippertz et al).”

(Please click here for powerpoint slides)

The attached ppt includes an isochrone analysis of the northern edge of the tropical water vapor reservoir (using 4 cm IWV – summary shown above and in slide 10) and its landfall (as seen in the GPS-Met network – slide 11). Also, the snow levels are well-observed with the new SLR network and shows strong north-south variation (slide 12)..

Forecasts are available from the California Nevada River Forecast Center (CNRFC): click here for precipitation forecasts..

Forecasts are also available from the weather service forecast office of the National Weather Service in San Diego: please click here.

California Drought: 2013/14 4th driest water year on record

California Drought: 4th driest water year depletes reservoirs

October 1, 2014

CW3E partners at the Sonoma County Water Agency (SCWA) are quoted in a recent article in the Santa Rosa Press Democrat marking water year 2013/14 as the 4th driest on record.


The baked lakebed of Lake Mendocino shows a carp head (photo taken 30 September 2014 by Press Democrat photographer Kent Porter)

Dwindling reservoir levels are one of the main concerns due to the drought – Lake Mendocino is only 27% full. The article mentions the research partnership between SCWA and CW3E. Understanding the key role of atmospheric rivers in the area’s water supply is a focus of the research agreement. Please find the full article (including additional photos and a video) at:

NASA NEWS program selects joint JPL+CW3E AR proposal

NASA NEWS program selects joint JPL+CW3E AR proposal

August 28, 2014


NASA recently announced it selections for its 2013 NASA Energy and Water Cycle (NEWS) solicitation. Included in the selections was a proposal led by Duane Waliser of JPL as PI, and Marty Ralph of CW3E and Bin Guan of UCLA as co-PIs. The proposal aims to study “Atmospheric Rivers: Water Extremes that Impact Global Climate, Regional Weather and Water Resources”, with objectives on observation characterization, including emphasis on atmospheric and terrestrial water budgets, and on the development of methodologies and metrics for model evaluation. The proposal is for a three year study, and funding is expected to start early in FY 2015.

Sonoma County Water Agency (SCWA) and Scripps Institution of Oceanography establish a Cooperative Agreement for Scientific and Educational Cooperation

Sonoma County Water Agency (SCWA) and Scripps Institution of Oceanography establish a Cooperative Agreement for Scientific and Educational Cooperation

July 2014

SCWA entrance; Santa Rosa, California.

Sonoma County Water Agency (SCWA) provides water for over 600,000 people from the Russian River in northern California. It also supports a vibrant economy famous for its wine and tourism, while at the same time working to restore endangered salmon species. SCWA performs this vital role in the face of a climate characterized by major swings in precipitation, ranging from major flooding to drought. These swings are largely controlled by the presence, absence and strength of atmospheric river storms, a topic for which CW3E provides deep and cutting-edge knowledge.

During meetings between CW3E and SCWA it became apparent that key capabilities at CW3E and needs for new information and tools at SCWA were well aligned. This led to the development of joint projects, including some with NOAA and/or USGS, for which it would be advantageous to formalize the relationship in a way that provides space for CW3E staff to spend productive time interacting with SCWA staff and their stakeholders. It also is seen as an opportunity for SCWA to highlight its forward looking culture of innovation geared toward improving its services and stewardship.

Specifically, the agreement sets forth to initiate cooperation to further the development of basic scientific and applied research with goals of advancing research in ocean science and meteorology, gaining a more fundamental understanding of the ocean and meteorology, and benefiting society at large. It also aims to maintain and promote channels of cooperation and communication that permit the exchange of academic and scientific knowledge, which will assist the Water Agency in carrying out water supply management more efficiently and effectively and the U.S. Army Corps of Engineers with flood control operations.

Three early projects form the initial use of this agreement: 1) study of the role of atmospheric rivers in filling Lake Mendocino and potentially offering predictability to retain water without increasing flood risk, 2) a NOAA-funded climate program office project to study the role of atmospheric rivers in ending droughts on the Russian River, including how this may be affected by a changing climate, as well as development of a drought scenario and drought readiness assessment, and 3) cooperation in developing a feasibility assessment project for the potential use of forecast-informed reservoir operations (FIRO) for Lake Mendocino in cooperation with the US Army Corps of Engineers. The FIRO effort is taking a major step forward through a workshop that is being conducted in August 2014 at Scripps. Representative of the partnership this important cooperative agreement creates, the FIRO Workshop is co-chaired by Jay Jasperse, Chief Engineer for SCWA, and F. Martin Ralph, Director of CW3E at UCSD/Scripps.

Publication Notice: Chemical properties of insoluble precipitation residue particles

CW3E Publication Notice

Chemical properties of insoluble precipitation residue particles

Jessie Creamean posing for a photo while clearing snow from the top of the NOAA trailer at Sugar Pine Dam after the storm on 2/25/11.

This article provides an in-depth analysis of resuspended residues from precipitation samples collected at a remote site in the Sierra Nevada Mountains in California during the 2009-2011 winter seasons. These residues may be used as a benchmark for classification of insoluble precipitation. Knowledge of the precipitation chemistry of insoluble residues coupled with meteorological and cloud microphysical measurements will ultimately improve our understanding of the link between aerosols, clouds, and precipitation.

This paper represents a significant milestone from the CalWater experiment, which is led by members of UCSD/Scripps’ new Centers on aerosols (CAICE) and extreme events (CW3E), as well as NOAA, DOE, NASA, USGS. It also highlights the multi-disciplinary research stimulated by CalWater, and the partnerships between key researchers across organizations. The lead author, Jessie Creamean, received her PhD in atmospheric chemistry from UCSD under Kim Prather using CalWater data, and is now bringing that expertise to a primarily meteorological group in NOAA as she pursues emerging topics in aerosol-precipitation interactions in collaboration with CW3E scientists.

A personal use copy of the article is available here.

CalWater-ACAPEX 2015 Planning Workshop

CalWater-ACAPEX 2015 Planning Workshop

Scripps Institution of Oceanography

La Jolla, California

CalWater 2 Co-Leads: Marty Ralph, Kim Prather, Dan Cayan (Scripps)

Organizing Committee: Chris Fairall (NOAA), Ruby Leung (PNNL), Andrew Martin (Scripps), Ryan Spackman (NOAA/STC)

CalWater2 – ACAPEX Observational Strategy Winter 2014-15

CalWater-2 took major steps from vision to reality on 22-24 April 2014 at Scripps Institution of Oceanography when roughly 40 key individuals (scientists, engineers, aircraft and ship managers, and students) met to plan for major field deployments in 2015. The following facilities are committed (or nearly so) to a field campaign between roughly 10 January and 10 March 2015:

  • DOE – G-1 aircraft
  • DOE AMF-2 ocean-atmosphere facility on the NOAA Research Vessel (ship) Ron Brown
  • NOAA G-IV aircraft
  • NOAA P-3 aircraft
  • ATOFMS mobile, land-based aerosol-sensor suite
  • EFREP hydrometeorological Mesonetwork in California

The DOE facilities are part of the ARM Cloud Aerosol Precipitation Experiment (ACAPEX) experiment addressing (1) aerosol impacts on clouds and precipitation and (2) atmospheric rivers. The NOAA facilities were requested also based on the CalWater vision, with an emphasis on atmospheric-river science questions.

The workshop concluded with a plan for specific start and end dates for each facility, narrowed options for where to operate them, a plan for a field operations center (and a specific possible location), strategies for developing coordinated ship and aircraft operations, and plans for the forecasting capabilities needed to guide missions. In addition, the 12-member CalWater Core Scientific Steering Group met afterword and reviewed plans for 2016-2018 and strategies to advance the longer term Calwater Vision. The Steering Group committed to organizing two special sessions and a side meeting (for last minute coordinations of the 2015 CalWater and ACAPEX activities) at the Fall Meeting of AGU in December 2014, and a journal article describing the program. The proposed AGU sessions are:

  1. CalWater Theme 1: Cloud-Aerosol-Precipitation Interactions in California (Conveners: Daniel Rosenfeld, Kimberly Prather),
  2. Atmospheric Rivers: Observations, Dynamics, Modeling, Impacts and Applications (Conveners: Marty Ralph, Duane Waliser, Jason Cordeira).

The presentations from the Workshop are available here.

Workshop Sponsored by:

  • Scripps, Center for Western Weather and Water Extremes (CW3E)
  • Scripps Center for Aerosol Impacts on Climate and the Environment (CAICE)
  • Science and Technology Corporation (STC)

Workshop Sponsored by:Workshop Participants

Photo of most workshop participants at the CalWater 2015 – ACAPEX workshop at Scripps, April 2014.

CalWater2 Workshop Participants

Who rules California’s Russian River?

Who Rules California’s Russian River?

Lake Sonoma. Credit: Water Environment Research Foundation

Who has rightful claim to California’s Russian River? Federal law may protect the river habitat in the name of endangered fish, but on land, grapevines are king. In the first of a two-part series, NOAA’s Caitlyn Kennedy describes how NOAA scientists are working with partners at other agencies and universities to help find compromise amid local tensions over water supplies.

Part 1 describes scientists’ efforts to understand and predict not just the river on land, but its counterpart in the sky—a river that delivers extreme, sometimes drought-busting storms into the heart of California’s wine country. Sometimes these storms can be a blessing. And at other times, a curse.

Part 1 is now available at:

Part 2 will explore how better forecasting of and strategies for coping with extreme events could lessen water conflicts along the Russian River.

Scripps Researchers Take Flight

Scripps and NOAA Researchers Take Flight to Observe Atmospheric River

IWV Feb 5-10, 2014

Integrated Water Vapor GFS Analysis Feb 5-10, 2014.

Researchers from Scripps Institution of Oceanography at UC San Diego, and NOAA are taking part in research flights to observe a distinctive type of storm system that has historically provided significant precipitation to California.

Scientists tracked the evolution of “atmospheric rivers,” narrow corridors of strong water vapor transport that can extend thousands of miles, as they made landfall in central California in early February. Atmospheric rivers (ARs), identified by researchers only in recent decades, can provide beneficial water supply and snowpack to the West Coast as well as create conditions for dangerous floods that affect lives and property. NOAA, Scripps, USGS, and other agency/institution researchers, working with water managers for the state, Sonoma County, and elsewhere, are studying them with the goal of providing better information for earlier and more accurate extreme weather forecasts. Scripps and USGS scientists are also looking at how atmospheric rivers may serve as “drought busters” and how climate change may affect atmospheric rivers in future decades.

Scripps researchers said that the February storms provided some relief, but would likely not reverse the dangerous drought conditions throughout California and the West that have built up over the last three years.

“Part of the reason for the drought has been the absence of atmospheric river storms hitting the region over the last year,” said Scripps climate researcher Marty Ralph. “From Feb. 7-10, a series of modest strength ARs hit Northern California, including near San Francisco and the northern Sierra where AR conditions stalled for up to 48 hours. These conditions created up to 12-15 inches of rain in three days, including in areas hit by the drought. This was more than double the precipitation in Northern California that had fallen in the first four months of the normal wet season. Nonetheless, the extreme drought has produced such a deficit in water that the soils absorbed much of the precipitation and rivers quickly receded to levels that are again well below normal, even though they reached fairly high levels during the storm.”

Ralph heads the Center for Western Water and Weather Extremes (CW3E), a new center established at Scripps Oceanography that is devoted to California’s special precipitation characteristics. At the core of the center will be a unique advanced network of monitoring stations throughout the state to help industries and 38 million California residents understand phenomena that affect the economy and everyday life in myriad ways.

The network, built over the last five years by NOAA and Scripps through support from California’s Department of Water Resources, will initially contain four atmospheric river observatories, monitoring stations located in Northern and central California that measure amounts of water vapor in the atmosphere and other climate variables.

“NOAA is very interested in improving our forecasts of extreme weather events, and atmospheric rivers rank with hurricanes as a major issue,” said Chris Fairall, chief of the Weather and Climate Physics branch of NOAA’s Earth System Research Laboratory in Boulder, Colo. “The West Coast relies on them for water, but it really is like trying to drink from the proverbial firehose. This new research collaboration on atmospheric rivers with Scripps and UC San Diego is a big step in attacking the problem.”

For this event, Ralph, Fairall, and colleagues gathered data aboard a NOAA Gulfstream IV aircraft that began flying over the Pacific Ocean off the U.S. West Coast on Feb. 7. During the flights, researchers measured several atmospheric properties at several locations along and across the atmospheric river corridor to better understand key processes, such as where the water vapor sources are and how they are sustained by storm dynamics.

Aboard the aircraft, researchers released small parachuted devices, called dropsondes, across the atmospheric river over the Pacific Ocean. As they descend, the dropsondes measure atmospheric conditions, such as pressure, temperature, humidity, wind speed and direction, and transmit the information back to the aircraft where a flight scientist uses it to guide the mission. After the dropsonde data are analyzed and processed, the information will be put into a standard format established by the World Meteorological Organization and provided to NOAA’s National Hurricane Center for inclusion in global and local-scale weather prediction models.

Mike Dettinger, a CW3E team member and research hydrologist with Scripps and the U.S. Geological Survey, noted that atmospheric rivers provide 30 to 50 percent of the precipitation in California and are behind 80 percent of the floodplain inundations along parts of the Central Valley where those inundations are a necessary part of ecosystem food webs and fish nurseries. They figure prominently in the ending of California droughts but also in taxing Northern California levees and other components of the state’s water delivery infrastructure.

“Thus, better understanding of how atmospheric rivers work and how they may change in the future is critical to better water, floods, and ecosystem management and to plans for adapting to future climate changes,” Dettinger said.

Jay Jasperse, chief engineer for the Sonoma County Water Agency, which provides water to 600,000 people and many agricultural users, said of the February storms, “although this AR may not be the strongest ever, it is certainly the most welcome.”

Results from this study will help guide atmospheric river research for the upcoming CalWater 2 experiment, which begins in 2015 and will use land-based stations and a research ship as well as multiple aircraft.

Researchers find climate link to atmospheric river storms

Climate Oscillations Linked to Atmospheric River Events

November 25, 2013

Climate Oscillations

High and low-pressure anomalies on the map (red=high, blue=low) are typical of combined negative phases of the Arctic Oscillation and Pacific/North American teleconnection.

A new research study has found a link between large-scale climate features and the occurrences of atmospheric river events. The research team was led by Bin Guan from UCLA and NASA’s Jet Propulsion Laboratory. They discovered that the occurrence of a negative phase in both the Arctic Oscillation (AO) and the Pacific/North American (PNA) teleconnection is associated with an increase of atmospheric river events over California. The paper was recently published in the journal Water Resources Research and can be accessed here.