Publication Notice: An Airborne Study of an Atmospheric River over the Subtropical Pacific during WISPAR: Dropsonde Budget-Box Diagnostics and Precipitation Impacts in Hawaii

CW3E Publication Notice

An Airborne Study of an Atmospheric River over the Subtropical Pacific during WISPAR: Dropsonde Budget-Box Diagnostics and Precipitation Impacts in Hawaii

Satellite image swath at 1921 UTC 3 Mar 2011 of IWV (cm; color scale at bottom) from the SSMIS. The unadjusted G-IV flight track is superimposed, along with dots marking the positions and times of the dropsonde releases late on 3 Mar (2007–2343 UTC) and early on 4 Mar (0003–0302 UTC) 2011. The operational rawinsonde locations at Lihue (LIH) and Hilo (ITO) on Hawaii are shown. Manually smoothed satellite-derived sea surface temperatures (8C; contours) from the Reynolds et al. (2007) daily 0.25830.258 resolution optimally interpolated infrared product are also shown. (From Neiman et al. 2014.).

The upcoming CalWater-2 experiment, which is organized by CW3E scientists and others from NOAA, NASA, DOE, USGS and elsewhere, will be using research aircraft to observe atmospheric rivers over the Northeastern Pacific Ocean and U.S. West Coast. This presents an opportunity to measure atmospheric river (AR) structure and embedded physical processes that control the water vapor transport budget. This paper develops some of the key diagnostic tools needed and demonstrates them using a flight pattern and dropsondes designed to calculate the vertical profile of water vapor flux divergence (and other key parameters) in an AR. These tools and associated flight strategies will be critical to future airborne field campaigns that will enable CW3E and colleagues to diagnose key AR-relevant physical processes and to then assess in detail their representation in weather and climate models.

In 2011 a short airborne campaign was conducted to demonstrate the ability of an unmanned aircraft (Global Hawk) to fly over ARs and sample them using dropsondes. As part of this successful demonstration of UAS technology – WISPAR – a special flight of the NOAA G-IV aircraft was also conducted. The paper presents a summary of this flight, including use of drospondes from a box pattern over an AR to calculate vertical profiles of divergence, water vapor flux divergence, sensible heat flux divergence and vertical air motions. The same AR studied here also produced over 10 inches of rain on the normally dry side of the Hawaiian Islands due to the anomalous water vapor transport conditions associated with the AR hitting the region.


The Winter Storms and Pacific Atmospheric Rivers (WISPAR) experiment was carried out in January–March 2011 from the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center as a demonstration for utilizing unmanned aerial systems in meteorological research and operations over data-sparse oceans. One of the campaign’s three missions was coordinated with a manned National Oceanic and Atmospheric Administration Gulfstream-IV (G-IV) flight out of Honolulu, Hawaii, on 3–4 March 2011. The G-IV, which flew through a developing atmospheric river (AR) west of Hawaii, represents the cornerstone observing platform for this study and provided the southernmost dropsonde observations of an AR published to date in the subtropical Northern Hemisphere. The AR exhibited characteristics comparable to those observed in previous studies farther north in the subtropics and midlatitudes, save for larger integrated water vapor and weaker winds in the AR core and stronger equatorward vapor fluxes in the shallow post-cold-frontal northeasterly flow. Eight dropsondes released in a ~200-km-wide box formation provided a novel kinematic assessment of tropospheric vorticity, divergence (mass, water vapor, sensible heat), and vertical velocity in the AR region, as well as sea surface fluxes. The budget-box diagnostics were physically consistent with global-gridded reanalysis datasets, while also providing useful additional kinematic and thermodynamic information on the mesoscale. Meteorological impacts of the AR were assessed on Hawaii’s island of Kauai, where the state’s heaviest rainfall was observed for this case. Rainfall on Kauai was modulated significantly by its steep orography, including on the normally dry side of the island where heavy rains fell.

A personal use copy of the article is available here.

Mike Dettinger elected AGU Fellow

CW3E congratulates Mike Dettinger – 2014 AGU Fellow<

July 30, 2014

CW3E congratulates PI Dr. Michael Dettinger’s election to AGU’s 2014 class of Fellows. This honor is a compliment to Mike’s long career and is presented with the citation “For insightful and useful research in understanding how climate and weather affect the variability of hydrologic systems”. Only one in a thousand members is elected AGU Fellow each year so this is a prestigious achievement. CW3E PI and colleague Dr. Dan Cayan notes “Mike was among the first to explain how hydrologic variability is organized across continental to global scales. Mike’s contributions also include new insights about how longer period climate variation may affect shorter period hydrologic phenomena. Mike’s recent emphasis on understanding North Pacific storms, with close ties to Marty Ralph and colleagues, has produced a sharper image of how “atmospheric rivers” produce most of the floods along the West Coast and deliver a large portion of its water supply.”

CW3E welcomes Reuben Demirdjian

CW3E welcomes Reuben Demirdjian

June 24, 2014

CW3E is pleased to welcome Reuben Demirdjian. Reuben joins CW3E to pursue his doctoral degree at Scripps Institution of Oceanography. Reuben completed his undergraduate degree at UC Santa Barbara in physics. “I met Dr. Ralph at the Scripps Open House and was impressed with the group he is building and his enthusiasm for understanding the role atmospheric rivers play in the precipittion regime of California and the western US,” Reuben said. Reuben is getting a head start this summer learning tools, especially the WRF (Weather, Research and Forecasting) model, and use of dropsonde observations from research aircraft.

CalWater 2015 Advanced Planning Workshop

CalWater 2015 Advanced Planning Workshop

June 10, 2014

CW3E is pleased to host a CalWater 2015 Advanced Planning Meeting for Forecasting at Scripps Institution of Oceanography from 24-25 June 2014. The purpose of this meeting was to begin preparing for a major deployment of 3 aircraft, a ship and ground-based observation sites this winter. Specifically the aim was to focus on the development of forecast requirements specific to the field experiment and implementation of forecasts for meteorological and chemical/aerosol dimentions of CalWater-2015. Coordinators of this meeting were Jason Cordeira (Plymouth State University), Andrew Martin (Scripps Institution of Oceanography) and Jonathan Rutz (NOAA/National Weather Service). Other participants included Ryan Spackman and Natalie Gaggani (NOAA STC/PSD) and Roger Pierce (NOAA/NWS).

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

ARs Play Role in Greenland Melt Episodes

Atmospheric Rivers Play Key Role in Rare Greenland Melt Episodes

Integrated Water Vapor (IWV) impacting Greenland on July 9, 2012 based on data from the 20th Century Reanalysis.

Researchers at NOAA’s Earth System Research Laboratory and the Center for Western Weather and Water Extremes here at Scripps have published a new article examining the processes responsible for the unusual melting episode in Greenland during the summer of 2012 when temperatures at the summit of Greenland rose above freezing for the first time since 1889. They found a number of climate factors were present in both 1889 and 2012 including strong atmospheric rivers transporting warm, moist air towards Greenland’s west coast. The research article was published in the Journal of Geophysical Research – Atmospheres.

A more in depth news story on this research can be found on the Scripps website.

A personal use copy of the article is available here.

Vision for future observations of extreme events in Western US

Vision for Future Observations of Extreme Precipitation and Flooding in the Western U.S.

A journal article entitled: A Vision for Future Observations for Western U.S. Extreme Precipitation and Flooding, by CW3E Director F. Martin Ralph and colleagues was recently published in the April 2014 issue of the Journal of Contemporary Water Research and Education

The paper describes how new technologies and paradigms using the most recent technological and scientific advances can be used to better monitor and predict extreme storms that lead to flooding in the Western U.S. The strategy is intended to add new technology to existing observational networks rather than replacement. The full journal article can be accessed here.

Schematic network of new sensors (land-based) to improve monitoring, prediction, and climate trend detection for hydrometeorological conditions that create extreme precipitation and flooding.

Atmospheric Rivers as Drought Busters

Atmospheric Rivers: Drought Busters

Drought status in California before and after two atmospheric river events in January 2010 (middle panel shows precipitation from these systems over 20 inches in some areas). recently highlighted CW3E researcher Mike Dettinger’s work looking at atmospheric rivers as drought busters (click here to see the post). Mike’s article “Atmospheric Rivers as Drought Busters on the US West Coast” was published in December 2013 in the AMS Journal of Hydrometeorology (find a link to this article on the CW3E publications page or click here). Given the dry conditions that have persisted over the last few years causing severe to extreme drought over the US West this article has received well-deserved attention. The piece highlights the impact of an atmospheric river storm from January of 2010. This image (shown above) illustrates the drought conditions before the storm (left panel), the amount of precipitation from the storm (middle panel – showing some areas had over 20 inches of precipitation!) and the drought conditions after the storm (right panel – showing the moderate and severe drought region greatly reduced).

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.

Likelihood of Drought Ending, updated

Drought Recovery by end of Water Year?

The most recent figures can be found on Mike Dettinger’s web page.

Drought Recovery Odds

Updated March 21, 2014

Researcher Mike Dettinger has updated his analysis examining the likelihood of the California drought ending by the end of the current water year on Sept 30, 2014. This new analysis utilizes the just released February precipitation totals for California’s climatic divisions as well as best guess estimates for March 2014 precipitation. Visit the CW3E Drought Info Page to see updated projections for all seven of California’s climatic divisions.

Drought Recovery Odds

February 12, 2014

CW3E researcher Mike Dettinger was interested in knowing the likelihood of California recovering from the drought by the end of the current water year on Sept 30, 2014. The method he came up with starts with the precipitation deficit from last water year (Oct 2012 – Sept 2013). Observed precipitation for Oct 2013 thru Jan 2014 was used to determine what has been added to this previous water year deficit, depicted in the above figure by the black squares. Here negative precipitation refers to the carryover deficit from the period extending back to October 2012.

Projections into the future of cumulative precipitation since Oct 2012 were computed by adding observed monthly precipitation from each year in the historical record, 1931-2013, or a total of 83 projections. For each future month (Feb-Sep 2014) the red dots in the above figure represent each of the 83 projections.

The example shown above is for the Sacramento Drainage region (CA Climate Division 2). For this region, only 2 of the 83 projections make it above the 75%-tile level by the end of Sept 2014. None of the projections show the 24-month cumulative precipitation reaching “normal” levels by the end of this water year.

Visit the CW3E Drought Info Page to see projections for all seven of California’s climatic divisions.

Dust storms: enhancing California’s precipitation

Dust Storms: enhancing California’s precipitation

Dust, as shown by orange colors, in a storm approaching California on 24 February 2014. (NASA Earth Observing System Data and Information System)

As CW3E continues to investigate rainfall over California from Atmospheric River storms, other researchers examine the same storms to evaluate the role of dust in enhancing precipitation amounts. A recent KQED story examines the work of Dr. Kim Prather (UCSD; atmospheric chemist). Dr. Prather evaluates the role of dust from storms over Africa and Asia that reach the California coast in 7-10 days. The high altitude particles have been found to increase the amount of rain and snowfall when they coincide with approaching coastal storms. See more on the story (including an audio piece) at: