Sonoma County Water Agency and CW3E — Monitoring sites expected to improve forecast capability<
South end of Lake Mendocino; September 2013 (photo by Kent Porter / Press Democrat)
The Santa Rosa Press Democrat (Sean Scully) published an article: “Weather forecasting a key concern for Sonoma County Water Agency”. CW3E is working with the Sonoma County Water Agency and the Hydrometeorology Testbed (HMT) data to improve forecasts in the region. The data being gathered from HMT will lead to improved forecasting of Atmospheric River (AR) events. These events are significant rain producers in the region and strongly impact how water is managed. Better management would lead to storage that could help prevent extremely low lake levels (as shown at Lake Mendocino above). Please find the full Press Democrat article here.
Resilience in a Changing Climate: Sonoma County Adaptation Forum
April 15, 2015
CW3E director Marty Ralph and scientist Julie Kalansky presented at the Sonoma County Adaptation Forum on April 8th. The forum was modeled after state forums, but was the first regional adaptation forum in California. The forum focused on information and approaches to help mitigate the impacts of climate change in Sonoma County and surrounding areas. The audience of over 200 people included city and county leaders, utility managers, environmental groups and the public.
Both Marty and Julie presented in the first session of the morning entitled “Extreme Weather Science; Drought and Deluge in Sonoma County.” Jay Jasperse, Chief Engineer and Director of Groundwater Management at Sonoma County Water Agency, moderated the session. The other panelists included Tim Doherty, from NOAA’s Office for Coastal Management, who discussed the impacts of sea level rise on the region, and Dr. Lisa Micheli, Executive Director of Pepperwood Preserve, who presented on the importance of downscaling climate models to understand the regional response to climate change. Marty Ralph discussed the importance of atmospheric rivers (ARs) to the water supply as well as the potential flooding risk associated with ARs. This led into an explanation of the FIRO, forecast informed reservoir operations, project for improving the water supply resilience of Lake Mendocino. At the end of his presentation he introduced the first part of an ongoing NOAA-NIDIS and Sonoma County Water Agency funded project to examine how the frequency and intensity of ARs may change in future. The link below is to an interview with Marty Ralph about atmospheric rivers and the forum that was broadcasted on North Bay Public Radio.
After Marty’s presentation, Julie presented on the second part of the study including the development of a “mega-drought” stress test for the region and working with the community to understand the all the different dimensions of drought. During Julie’s presentation, she was able to involve the audience and received feedback on the vulnerabilities to drought and the difficult decisions that surround drought. The day was a great success in bringing together scientists, decisions makers and the public to discuss how to make the community more resilient to climate change.
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”.
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.
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.
“And it never failed that during the dry years the people forgot about the rich years and during the wet years they lost all memory of the dry years. It was always that way.” —John Steinbeck, East of Eden, 1962
Heavy rains are predicted for California this week, and after the extreme drought of the past few years, California welcomes the moisture. But can there be too much of a good thing?
While drought is a significant natural hazard Californians must contend with, the natural hazards of severe weather and flooding are equally significant in the feast or famine cycle of storms in California.
NOAA’s National Weather Service has issued several watches, warnings, and advisories for across California. Flash floods and high winds are expected in many areas.
Drought is a familiar occurrence in California. Indeed, at a year-to-year or shorter time scale, California has a remarkably variable hydroclimate, experiencing larger year-to-year variations in precipitation than anywhere else in the U.S.
In large part, this extreme variability arises from the small number of storms that provide most of the state’s precipitation each year. If a few large storms happen to bypass California in a given winter, precipitation totals are proportionally much reduced and we risk drought. But the wet, drought-busting months are typically reflections of one or two extremely large storms, with almost half of the large drought-busting storms resulting from landfalling atmospheric rivers or “pineapple expresses.”
Atmospheric Rivers (ARs) are constantly moving and evolving pathways of water vapor transport that are thousands of kilometers long but only about 500 km wide and that contain large quantities of water vapor and strong winds They are naturally occurring parts of the global water cycle, responsible for more than 90 percent of all atmospheric vapor transport at latitudes of the conterminous United States. When an AR reaches and encounters mountains in the West Coast states, the fast moving, moisture-laden air contained in ARs generally flows up and over the coastal and Sierra Nevada ranges, leading to almost ideal conditions for producing intense and sustained precipitation. Because of the intensity and persistence of their rains, ARs are the cause of many of the most extreme storms along the West Coast and a large majority of the floods in that region.
Atmospheric rivers have, in recent years, been recognized as the cause of the large majority of major floods in rivers all along the U.S. West Coast and as the source of 30 – 50 percent of all precipitation in the same region. In terms of droughts in California, about 33 – 40 percent of all persistent drought endings have been brought about by landfalling AR storms, with more localized low-pressure systems responsible for most of the remaining drought breaks.
In 2010, the USGS Science Applications for Risk Reduction (SAFRR) program created an interdisciplinary scenario about large atmospheric river storms in California called ARkStorm. The ArkStorm scenario brought together experts in climate, weather, economics, geography, and other disciplines to create a hypothetical, but scientifically plausible scenario of a future large storm that is providing emergency responders, resource managers, and the public with a realistic example that they can use to determine the possible consequences of a really large AR storm might be.
A new Center at UC San Diego’s Scripps Institution of Oceanography has established a regional effort on atmospheric rivers and other types of extreme weather and water events in the Western U.S. The Center for Western Weather and Water Extremes (CW3E) is developing an “AR Portal” with partners across the nation, including NOAA, California Department of Water Resources, Plymouth State University, and the USGS. The portal brings together advances in AR science, monitoring and prediction, and builds heavily on data from the new AR monitoring network installed across California, and takes unique advantage of existing USGS, NOAA and other monitoring and prediction systems by developing tools tailored to the AR phenomenon.
Pacific Northwest Flooding (slide 3; M. Ralph and L. Schick)
CW3E director Marty Ralph and US Army Corps of Engineers researcher Larry Schick provide a summary of recent flooding in the Pacific Northwest. The heavy precipitation (ending November 28) resulted in an R-CAT 2 event (an event which produces 12-16 inches of precipitation in a 3-day period).
During this event one can see an orographic enhancement of precipitation amounts with a rain “shadow” (low amounts of precipitation) in the Seattle region (slide 2). The heavy precipitation resulted in several streamflow sites exceeding flood stage (shown above; slide 3). The Northwest River Forecast Center had an excellent forecast of peak flow on the Skagit River (slide 4).
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).”
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: 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: http://www.pressdemocrat.com/news/2909680-181/north-coast-water-woes-reflected
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.