CW3E Welcomes Brian Kawzenuk

CW3E welcomes Brian Kawzenuk

March 30, 2015

CW3E is pleased to welcome Brian Kawzenuk as a staff research associate. Brian joins us from completing his master’s work with Dr. Jason Cordeira at Plymouth State University in New Hampshire. At Plymouth Brian investigated the impacts of land-falling atmospheric rivers (ARs) on the west coast during February 2014. The structure and dynamics of AR events as well as their influence on extreme precipitation over the west coast were explored. Brian looks forward to continuing his study of AR events and using his extensive analytic and programming skills to help the CW3E team develop stakeholder tools. Brian grew up in central New York State and has always had a passion for meteorology. We’re delighted to welcome him to the team and hope he enjoys the milder climate of the La Jolla region.

Sonoma County Water Agency video posted about Atmospheric Rivers

Sonoma County Water Agency (SWCA) Video posted about Atmospheric Rivers (ARs)

March 4, 2015

CW3E is pleased to be part of a recent video produced by our partners at the Sonoma County Water Agency (SCWA) and hosted by SCWA Director Shirlee Zane. This video focuses on the importance of Atmospheric Rivers (ARs) to California’s precipitation. Extremes of both drought and flood are examined for their link to ARs and impact on the Sonoma region. Emphasis is placed on the importance of understanding ARs and applying that knowledge to create better forecast information to help SCWA prepare for drought and potential flood conditions. Shirlee points out a key goal of our collaboration: “retain water without increasing flood risk”.

DWR Video posted about CalWater and ARs

DWR Video posted about CalWater and ARs

February 27, 2015

CW3E is pleased to be part of a recent video produced by Elissa Lynn, program manager at California’s Department of Water Resources (a CW3E partner). This video focuses on the recent CalWater 2015 – ACAPEX Field Campaign and the importance of Atmospheric Rivers (ARs) to California’s precipitation. This video provides excellent background information about ARs and how unique CalWater 2015 was with the availability of 4 different aircrafts and a NOAA research vessel examining ARs simultaneously. The importance of atmospheric aerosols from humans and their potential link to precipitation quantity is also described in this video.

California Precipitation: summary handout

California Precipitation: summary handout

February 8, 2015

Coefficient of variation (the standard deviation divided by the average) of total precipitation based on water year data from 1951-2008.

Please click here for the summary handout

CW3E and partners from the California Department of Water Resources, CNAP and the Southwest Climate Science Center have released a summary handout describing California precipitation. The seasonality and variability of precipitation for the state are examined in this summary. Special emphasis is on the link between large storms (AR storms) and the total precipitation for a season. The figure above (Dettinger et al., 2011) illustrates that how much variability there is from year to year in precipitation. The green and blue circles over California indicate the largest year-to-year variability is over this state at an order of about half the annual average precipitation.

LA Times: Focus on ARs and CW2-ACAPEX

LA Times: Focus on ARs and CW2-ACAPEX

January 19, 2015

Photo by Allen J. Schaben / Los Angeles Times: Sunset through clouds over Los Angeles

A recent LA Times article “California drought could end with storms known as atmospheric rivers” highlighted the importance of ARs to California’s water status and the start of the CalWater2 – ACAPEX field campaign (article by Tony Barboza). This article provides an excellent summary of the role of ARs in California’s water supply – from drought to flood. It emphasizes that ARs are known to have a strong link to ending droughts (article by CW3E researcher Mike Dettinger, Journal of Hydrometeorology). As well as highlighting the importance of ARs the article mentions the effort to better understand ARs with the massive data collection effort undergoing now by university and government scientists in CalWater2 – ACAPEX. Find more information about CW2-ACAPEX here.

CalWater-2/ARM Cloud Aerosol Precipitation Experiment (ACAPEX)

CalWater-2/ARM Cloud Aerosol Precipitation Experiment (ACAPEX): AGU session

January 2, 2015

The influence of Atmospheric Rivers (ARs) on wet extremes since 1950 are shown by the fraction of AR landfall days (green portion of pie chart). Note, for example, 87% of flood days for the Russian River are AR landfall days.

The Fall 2014 AGU meeting in San Francisco hosted a workshop/press conference describing the upcoming 2015 field campaign: CalWater2 / ARM Cloud Aerosol Precipitation Experiment (ACAPEX). Scientists from Scripps Institution of Oceanography at UC San Diego, the Department of Energy’s Pacific Northwest National Laboratory (PNNL), and NOAA discussed the impetus behind the field campaign to begin in early 2015. The panel described how ground-based, multiple-aircraft, and ship-based measurements will help provide a better understanding of how California gets its rain and snow, how human activities are influencing precipitation, and how the new science provides potential to inform water management decisions relating to drought and flood. One of the related presentations was given by CW3E PI Mike Dettinger. Dr. Dettinger, AGU 2014 Fellow, described historical and future impacts of land-falling ARs. The image above, from his presentation, depicts the influence of AR land-falling days on extreme wet events in California (Russian River floods, flood plain inundations and levee breaks).

Click here for the UCSD/SIO press release about the workshop / press conference.

Click here for the related UCSD/SIO news story about “Refilling California’s Reservoirs—The Roles of Aerosols and Atmospheric Rivers”.

Click here to follow the CalWater-2 / ACAPEX field project forecasts.

First International Atmospheric Rivers Conference

First International Atmospheric Rivers Conference

Note: the full conference has been postponed to 2016

Atmospheric rivers (ARs) play a key role in the water cycle as the primary mechanism conveying water vapor through mid-latitude regions. The precipitation that ARs deliver in many parts of the world, especially through orographic precipitation proceses, is important for water resources; but it also regularly is a hazard, with floods resulting. The aims of the First International Atmospheric Rivers Conference are

  • to discuss and identify differing regional perspectives and conditions from around the world,
  • to evaluate the current state and applications of the science of the mid-latitude atmospheric water cycle, with particular emphasis on atmospheric rivers and associated or parallel processes (e.g., tropical moisture exports),
  • to assess current forecasting capabilities and developing applications, and
  • to plan for future scientific and practical challenges.

The conference aims to bring together experts from academia and applications to form a real community of interests. Questions on the table include: What meteorological conditions constitute ARs and what do not? How can ARs (and related processes) best be identified and categorized? What are the most promising new research directions for putting AR science into its proper meteorological/climatological context and improving its applicability?

Additional contributions are now invited from the scientific community

If you have an interest in ARs (or related topics) and an interest in participating please contact the chairs Marty Ralph or Mike Dettinger.

Please click here for more details.

Antarctic Atmospheric Rivers

CW3E Publication Notice

The role of atmospheric rivers in anomalous snow accumulation in East Antarctica

December 4, 2014

Gorodetskaya, I.V., M. Tsukernik, K. Claes, F.M. Ralph, W.D. Neff and N.P.M. Van Lipzig, 2014: The role of atmospheric rivers in anomalous snow accumulation in East Antarctica. Geophysical Research Letters, 41, 6199-6206.

(Please click here for a personal use copy of the article)

Integrated water vapor (colors) at 00Z on 15 February 2011. Red arrows indicated vertically integrated total moisture transport within the atmospheric river as identified using the definition adapted for Antarctica. Black contours are 500 hPa geopotential heights, where L shows a closed trough at 500 hPa influencing Dronning Maud Land and H shows the blocking high-pressure ridge downstream of the low. White square shows Princess Elisabeth station location. Based on the ERA-Interimm reanalysis.

Understanding changes in the Antarctic ice sheet mass are important for predicting global sea level rise. Recently, East Antarctica gained substantial mass, counterbalancing the increasing ice discharge from West Antarctica in these years. Occasional large snowfall events explained this increased mass load, which has been especially high in 2009 and 2011. Ground-based measurements at the Belgian Antarctic station Princess Elisabeth, established at the ascent to the East Antarctic plateau, have well captured these occasional intense snowfalls and associated snow accumulation responsible for 2009 and 2011 mass anomalies. The question is what has been causing this high accumulation?

Most of the water vapor transforming into the Antarctic snowfall arrives from lower latitudes. We have established that atmospheric rivers explain all extremely high snow accumulation events leading to the mass anomaly at Princess Elisabeth station in 2009 and 2011. These narrow bands of high moisture content have been more known in mid latitudes for their, sometimes catastrophic, impacts, such as heavy precipitation resulting in floods. The atmospheric rivers reaching the Antarctic ice sheet bring a lot of moisture from as far as subtropics and result in intense snowfall when reaching the steep ascent to the Antarctic plateau.
In addition, the work represents a significant advance in the understanding of how the global water cycle is affected by atmospheric rivers by

  • diagnosing their role in recent Antarctica extreme snowfall events,
  • developing an AR-detection methodology to track ARs into Polar Regions and
  • exploring their role in cryospheric processes of importance to global sea level in a changing climate.


Recent, heavy snow accumulation events over Dronning Maud Land (DML), East Antarctica, contributed significantly to the Antarctic ice sheet surface mass balance (SMB). Here we combine in situ accumulation measurements and radar-derived snowfall rates from Princess Elisabeth station (PE), located in the DML escarpment zone, along with the European Centre for Medium-range Weather Forecasts Interim reanalysis to investigate moisture transport patterns responsible for these events. In particular, two high-accumulation events in May 2009 and February 2011 showed an atmospheric river (AR) signature with enhanced integrated water vapor (IWV), concentrated in narrow long bands stretching from subtropical latitudes to the East Antarctic coast. Adapting IWV-based AR threshold criteria for Antarctica (by accounting for the much colder and drier environment), we find that it was four and five ARs reaching the coastal DML that contributed 74–80% of the outstanding SMB during 2009 and 2011 at PE. Therefore, accounting for ARs is crucial for understanding East Antarctic SMB.