Atmospheric rivers, cloud-creating aerosol particles, and california reservoirs

In the midst of the California rainy season, scientists are embarking on a field campaign designed to improve the understanding of the natural and human-caused phenomena that determine when and how the state gets its precipitation. They will do so by studying atmospheric rivers, meteorological events that include the famous rainmaker known as the Pineapple Express.

CalWater 2015 is an interagency, interdisciplinary field campaign starting January 14, 2015. CalWater 2015 will entail four research aircraft flying through major storms while a ship outfitted with additional instruments cruises below. The research team includes scientists from Scripps Institution of Oceanography at UC San Diego, the Department of Energy's Pacific Northwest National Laboratory, NOAA, and NASA and uses resources from the DOE's Atmospheric Radiation Measurement (ARM) Climate Research Facility -- a national scientific user facility.

The study 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.

"After several years in the making by an interdisciplinary science team, and through support from multiple agencies, the CalWater 2015 field campaign is set to observe the key conditions offshore and over California like has never been possible before," said Scripps climate researcher Marty Ralph, a CalWater lead investigator. "These data will ultimately help develop better climate projections for water and will help test the potential of using existing reservoirs in new ways based on atmospheric river forecasts."

Like land-based rivers, atmospheric rivers carry massive amounts of moisture long distances -- in California's case, from the tropics to the U.S. West Coast. When an atmospheric river hits the coast, it releases its moisture as precipitation. How much and whether it falls as rain or snow depends on aerosols -- tiny particles made of dust, sea salt, volatile molecules, and pollution.

The researchers will examine the strength of atmospheric rivers, which produce up to 50 percent of California's precipitation and can transport 10-20 times the flow of the Mississippi River. They will also explore how to predict when and where atmospheric rivers will hit land, as well as the role of ocean evaporation and how the ocean changes after a river passes.

"Climate and weather models have a hard time getting precipitation right," said Ralph. "In fact, the big precipitation events that are so important for water supply and can cause flooding, mostly due to atmospheric rivers, are some of the most difficult to predict with useful accuracy. The severe California drought is essentially a result of a dearth of atmospheric rivers, while, conversely, the risk of Katrina-like damages for California due to severe ARs has also been quantified in previous research."

For the next month or more, instrument teams will gather data from the NOAA research vessel Ronald H. Brown and two NOAA, one DOE, and one NASA research aircraft with a coordinated implementation strategy when weather forecasters see atmospheric rivers developing in the Pacific Ocean off the coast of California. NASA will also provide remote sensing data for the project.

"Improving our understanding of atmospheric rivers will help us produce better forecasts of where they will hit and when, and how much rain and snow they will deliver," said Allen White, NOAA research meteorologist and CalWater 2015 mission scientist. "Better forecasts will give communities the environmental intelligence needed to respond to droughts and floods."

Most research flights will originate at McClellan Airfield in Sacramento. Ground-based instruments in Bodega Bay, Calif., and scattered throughout the state will also collect data on natural and human contributions to the atmosphere such as dust and pollution. This data-gathering campaign follows the 2009-2011 CalWater1 field campaign, which yielded new insights into how precipitation processes in the Sierra Nevada can be influenced by different sources of aerosols that seed the clouds.

"This will be an extremely important study in advancing our overall understanding of aerosol impacts on clouds and precipitation," said Kimberly Prather, a CalWater lead investigator and Distinguished Chair in Atmospheric Chemistry with appointments at Scripps Oceanography and the Department of Chemistry and Biochemistry at UC San Diego. "It will build upon findings from CalWater1, adding multiple aircraft to directly probe how aerosols from different sources, local, ocean, as well as those from other continents, are influencing clouds and precipitation processes over California."

"We are collecting this data to improve computer models of rain that represent many complex processes and their interactions with the environment," said PNNL's Leung. "Atmospheric rivers contribute most of the heavy rains along the coast and mountains in the West. We want to capture those events better in our climate models used to project changes in extreme events in the future."

Prather's group showed during CalWater1 that aerosols can have competing effects, depending on their source. Intercontinental mineral dust and biological particles possibly from the ocean corresponded to events with more precipitation, while aerosols produced by local air pollution correlated with less precipitation.

The CalWater 2015 campaign is comprised of two interdependent efforts. Major investments in facilities include aircraft, ship time, and sensors by NOAA. Marty Ralph, Kim Prather, and Dan Cayan from Scripps, and Chris Fairall, Ryan Spackman, and Allen White of NOAA lead CalWater-2. The DOE-funded ARM Cloud Aerosol Precipitation Experiment (ACAPEX) is led by Ruby Leung from PNNL. NSF and NASA have also provided major support for aspects of CalWater, leveraging the NOAA and DOE investments.

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Giant atmospheric rivers add mass to Antarctica's ice sheet

Extreme weather phenomena called atmospheric rivers were behind intense snowstorms recorded in 2009 and 2011 in East Antarctica. The resulting snow accumulation partly offset recent ice loss from the Antarctic ice sheet, report researchers from KU Leuven.

Atmospheric rivers are long, narrow water vapour plumes stretching thousands of kilometres across the sky over vast ocean areas. They are capable of rapidly transporting large amounts of moisture around the globe and can cause devastating precipitation when they hit coastal areas.

Although atmospheric rivers are notorious for their flood-inducing impact in Europe and the Americas, their importance for Earth's polar climate -- and for global sea levels -- is only now coming to light.

In this study, an international team of researchers led by Irina Gorodetskaya of KU Leuven's Regional Climate Studies research group used a combination of advanced modelling techniques and data collected at Belgium's Princess Elisabeth polar research station in East Antarctica's Dronning Maud Land to produce the first ever in-depth look at how atmospheric rivers affect precipitation in Antarctica.

The researchers studied two particular instances of heavy snowfall in the East Antarctic region in detail, one in May 2009 and another in February 2011, and found that both were caused by atmospheric rivers slamming into the East Antarctic coast.

The Princess Elisabeth polar research station recorded snow accumulation equivalent to up to 5 centimetres of water for each of these weather events, good for 22 per cent of the total annual snow accumulation in those years.

The findings point to atmospheric rivers' impressive snow-producing power. "When we looked at all the extreme weather events that took place during 2009 and 2011, we found that the nine atmospheric rivers that hit East Antarctica in those years accounted for 80 per cent of the exceptional snow accumulation at Princess Elisabeth station," says Irina Gorodetskaya.

And this can have important consequences for Antarctica's diminishing ice sheet. "There is a need to understand how the flow of ice within Antarctica's ice sheet responds to warming and gain insight in atmospheric processes, cloud formation and snowfall," adds Nicole Van Lipzig, co-author of the study and professor of geography at KU Leuven.

A separate study found that the Antarctic ice sheet has lost substantial mass in the last two decades -- at an average rate of about 68 gigatons per year during the period 1992-2011.

"The unusually high snow accumulation in Dronning Maud Land in 2009 that we attributed to atmospheric rivers added around 200 gigatons of mass to Antarctica, which alone offset 15 per cent of the recent 20-year ice sheet mass loss," says Irina Gorodetskaya.

"This study represents a significant advance in our understanding of how the global water cycle is affected by atmospheric rivers. It is the first to look at the effect of atmospheric rivers on Antarctica and to explore their role in cryospheric processes of importance to the global sea level in a changing climate," says Martin Ralph, contributor to the study and Director of the Center for Western Weather and Water Extremes at the University of California, San Diego.

"Moving forward, we aim to explore the impact of atmospheric rivers on precipitation in all Antarctic coastal areas using data records covering the longest possible time period. We want to determine exactly how this phenomenon fits into climate models," says Irina Gorodetskaya.

"Our results should not be misinterpreted as evidence that the impacts of global warming will be small or reversed due to compensating effects. On the contrary, they confirm the potential of Earth's warming climate to manifest itself in anomalous regional responses. Thus, our understanding of climate change and its worldwide impact will strongly depend on climate models' ability to capture extreme weather events, such as atmospheric rivers and the resulting anomalies in precipitation and temperature," she concludes.

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North Atlantic atmospheric oscillation affects quality of cava

The standard of cava is dependent on technical factors for example fermentation, aging and bottling processes, which often remain stable for a long time. Scientists from Malaga College (The country) have found that shake within the North Atlantic -that affects European climate- also impact the characteristics of the sparkling wine. Time by which there's existence of the Azores anticyclone, there's a stop by the standard of cava.

The scientists Raimundo Real and Jos? Carlos B?ez, in the College of Malaga, have analysed the potential results of its northern border Atlantic oscillation, known in scientific literature as NAO, on the standard of The spanish language cava inside a study released within the Worldwide Journal of Biometeorology.

The NAO is really a microclimate index that reflects the atmospheric pressure distinction between the Azores and Iceland, so the existence of an anticyclone within the Azores is positive which is negative if you will find regions of low pressure for the reason that same area. This pressure difference that oscillates with time, has an effect around the climate conditions within the Iberian Peninsula.

"We discovered there is an association between your NAO and the standard of cava between 1970 and 2008. The presence of positive NAO values throughout the several weeks of March to August, once the grape is developing and ageing, reduced the capability of acquiring high quality cava," Raimundo Real told SINC.

Its Northern Border Atlantic oscillation plays a significant role in weather fluctuations within the hemisphere. The phenomenon affects the weather in Europe and also the Iberian Peninsula. It relates to temperature and rain versions in cava creating regions, which affects the physiological processes throughout the grape's duration of maturity.

"The probability of acquiring a high quality cava is greater once the average worth of the NAO is negative. This will make the typical temperature within the cava region drop and the standard enhances," the expert described.

Inter-annual versions in the standard of cava are determined based on the different aromas and the quantity of sugar within the grape. These characteristics from the plant consequently, in a single section of production, rely on climate conditions, for example cloud cover, temperature and rain fall that the guarana plant is exposed, particularly throughout the grape period (March to September).

Predicting time of top-quality cava

The weather within the Atlantic Sea, the med basin and also the surrounding continents shows considerable weather variability.

"Throughout 1 / 2 of time we analysed, the NAO values are intermediate and don't clearly affect the standard from the cava, however in another half, the tend to be more extreme and result in clearly favorable or unfavorable conditions for acquiring top-quality," states Real.

The data for 2012 pointed towards an 80% probability of acquiring a high-quality cava, although this odds are around 45% for 2013, always based on the model acquired. The model properly predicted the 80% for that clearly favorable years for acquiring top-quality cava and also the 70% probability of the clearly unfavorable years.

The NAO value between March and August could be calculated in the wine the harvest, while the standard from the cava are only able to be valued 2 yrs later. "This will be significant for having the ability to predict many years of top-quality cava production, too for going through the potential side effects and versions of global warming on the standard" he came to the conclusion.

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