New insights into predicting future droughts in California: Natural cycles, sea surface temperatures found to be main drivers in ongoing event

According to a new NOAA-sponsored study, natural oceanic and atmospheric patterns are the primary drivers behind California's ongoing drought. A high pressure ridge off the West Coast (typical of historic droughts) prevailed for three winters, blocking important wet season storms, with ocean surface temperature patterns making such a ridge much more likely. Typically, the winter season in California provides the state with a majority of its annual snow and rainfall that replenish water supplies for communities and ecosystems.

Further studies on these oceanic conditions and their effect on California's climate may lead to advances in drought early warning that can help water managers and major industries better prepare for lengthy dry spells in the future.

"It's important to note that California's drought, while extreme, is not an uncommon occurrence for the state. In fact, multi-year droughts appear regularly in the state's climate record, and it's a safe bet that a similar event will happen again. Thus, preparedness is key," said Richard Seager, report lead author and professor with Columbia University's Lamont Doherty Earth Observatory.

This report builds on earlier studies, published in September in the Bulletin of the American Meteorological Society, which found no conclusive evidence linking human-caused climate change and the California drought. The current study notes that the atmospheric ridge over the North Pacific, which has resulted in decreased rain and snowfall since 2011, is almost opposite to what models project to result from human-induced climate change. The report illustrates that mid-winter precipitation is actually projected to increase due to human-induced climate change over most of the state, though warming temperatures may sap much of those benefits for water resources overall, while only spring precipitation is projected to decrease.

The report makes clear that to provide improved drought forecasts for California, scientists will need to fully understand the links between sea surface temperature variations and winter precipitation over the state, discover how these ocean variations are generated, and better characterize their predictability.

This report contributes to a growing field of science-climate attribution-where teams of scientists aim to identify the sources of observed climate and weather patterns.

"There is immense value in examining the causes of this drought from multiple scientific viewpoints," said Marty Hoerling, report co-author and researcher with NOAA's Earth System Research Laboratory. "It's paramount that we use our collective ability to provide communities and businesses with the environmental intelligence they need to make decisions concerning water resources, which are becoming increasingly strained."

To view the report, visit:?http://cpo.noaa.gov/MAPP/californiadroughtreport.

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Predicting climate: Scientists test periodic-to-decadal conjecture

In new research released in Tellus A, Francois Counillon and co-authors in the Bjerknes Center are testing periodic-to-decadal conjecture.

In the Bjerknes Center, scientists are exploring the opportunity of periodic to decadal climate conjecture. This can be a area still in the infancy, along with a first attempt is made public for that latest Intergovernmental Panel on Global Warming (IPCC) report.

Aside from a couple of isolated regions, conjecture skill was moderate, departing room for improvement. In new research released in Tellus A, periodic-to-decadal conjecture is examined by having an advanced initialisation way in which has shown effective in weather predicting and operational oceanography.

"Regular" climate forecasts are made to represent the persistent change caused by exterior forcings. Such "forecasts" begin with initial problems that are distant from present day climate and therefore neglect to "predict" the entire year-to-year variability and the majority of the decadal variability -- like the pause within the global temperature increase (hiatus) or even the spate of harsh winter within the northern hemisphere. In comparison, weather forecasts depend positioned on the precision of the initial condition because the influence from the exterior forcing is nearly imperceptible.

For periodic-to-decadal time scales both initial condition and also the exterior forcing influence the conjecture. Beginning an environment conjecture from a preliminary condition nearer to the actual weather conditions are therefore essential to yield better conjecture than accounting just for exterior forcing. Within our region of great interest, decadal skill might be accomplished by enhancing the representation from the warmth content transiting in to the Nordic Ocean and as a result is going to influence the precipitation and temperature over Scandinavia.

The technique used to initialise/ correct a dynamical product is known to as data assimilation. It estimations the first condition of the model knowing some sparse findings (a smaller amount than 1% from the sea variables are observed). Rapport between your findings and also the non-observed variables should be found to broaden the corrections.

In addition, the corrections must fulfill the model dynamics to prevent abrupt changes throughout the forecast. The Ensemble Kalman Filter uses statistics from an ensemble of forecasts to estimate the connection between your findings and all sorts of variables for his or her correction. This process is computationally intensive because it requires parallel integrations from the model however it guarantees the relationship evolve using the system, which the corrections fulfill the dynamics from the model.

The Norwegian climate conjecture model (NorCPM) combines the Norwegian Earth System model using the Ensemble Kalman Filter. Over time, we plan to perform retrospective decadal forecasts (hindcasts) during the last century, to check the ability of our bodies on disparate phases from the climate and reveal the relative need for internal and exterior influences on natural climate variability, including the value of feedback systems. Ocean surface temps (SST) would be the only findings readily available for this type of lengthy time period and will also be employed for initialisation.

Our study looks into the possibility abilities of putting together SST only, utilizing an idealised framework, i.e. in which the synthetic option would be obtained from exactly the same model at different occasions. This framework enables a comprehensive validation since the full option would be known and our bodies could be examined from the upper predictive skill (the situation where findings could be available absolutely everywhere). NorCPM shown decadal of a routine for that Atlantic meridional knocking over and warmth content within the Nordic Seas which are near to the model's limit of of a routine. Although these answers are encouraging, the idealised framework assumes the model is ideal minimizing skill is anticipated inside a real framework. This verification is presently ongoing.

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Motion of the ocean: Predicting the big swells

New research will help you every morning with the surf report. Research led by the Vice-Chancellor will allow oceanographers and meteorologists to better predict the rate at which ocean swells decay, or deteriorate, as they travel across the globe.

"Ocean cargo shipping, offshore oil and gas production, and even recreational activities such as surfing, are all dependent on wave action," says Professor Young.

"It is therefore critical that we are able to predict swell."

It is estimated that 75 per cent of waves across the world are not actually generated by local winds. Instead, they are driven by distant storms which propagate as swell.

"Imagine you drop a rock in a pond. Waves radiate out from the rock. You don't need anything to push the waves. Once generated, they propagate by themselves.

"So, for most of the Indian, Pacific and South Atlantic oceans, it is actually the weather in the Southern Ocean thousands of kilometres away that dominates the wave conditions," explains Professor Young.

"The Southern Ocean is dominated by big low pressure systems that move across it year round. These systems generate waves that then grow and can travel tens of thousands of kilometres from where they were actually formed, to crash on a beach in Australia."

Professor Young, who is affiliated with the Research School of Earth Sciences, used orbiting satellites to track swell generated in the Southern Ocean and measure the rate of decay as it travelled north towards Australia.

The results showed that the decay of the swell depends on how steep the wave actually is.

"Steep waves decay very quickly. However, typical swell is not very steep and can travel across oceanic basins with only a relatively small loss of energy."

Over 200 individual cases were tracked, making this study the first to provide such comprehensive data of this decay.

"What we were able to do is track the swell from the satellite as it moved from the south to the north, some 1400 kilometres. We only chose cases where there was no wind so that we could be confident that all we were measuring was the swell decay.

"We can take these results and put them into a mathematical formula that can be put straight into computer models used by national weather bureaus.

"This will increase our ability to better predict wave action. As 70 per cent of the world's oceans are dominated by swell, it's extremely important to be able to predict them accurately."

Journal Reference:

I. R. Young, A. V. Babanin, S. Zieger. The Decay Rate of Ocean Swell Observed by Altimeter. Journal of Physical Oceanography, 2013; 43 (11): 2322 DOI: 10.1175/JPO-D-13-083.1

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Scientists a step closer to predicting tornadoes

For decades, meteorologists have been able to forecast the severity of hurricane seasons several months ahead of time. Yet forecasting the likelihood of a bad tornado season has proved a far greater challenge.

By Charlie Riedel, AP

Brenna Burzinski looks through the rubble in her devastated apartment in Joplin, Mo., on May 25.

By Charlie Riedel, AP

Brenna Burzinski looks through the rubble in her devastated apartment in Joplin, Mo., on May 25.

Now, research from scientists at Columbia University's International Research Institute for Climate and Society could eventually lead to the first seasonal tornado outlooks.

"Understanding how climate shapes tornado activity makes forecasts and projections possible, and allows us to look into the past and understand what happened," said Michael Tippett, lead author of a study in February's journal of Geophysical Research Letters.

The need for such data is reinforced by the still-fresh memory of 550 Americans killed by tornadoes last year — coupled with an unusually violent January for twisters.

In the study, Tippett and his team looked at 30 years of past climate data. They used computer models to determine that the two weather factors most tied to active tornado months and seasons were heavy rain from thunderstorms and extreme wind shear (wind blowing from different directions at different layers of the atmosphere).

"If, in March, we can predict average thunderstorm rainfall and wind shear for April, then we can infer April tornado activity," Tippett says.

The method worked for each month except for September and October, and it worked best in June.

This is the first time a forecast of up to a month in advance has been demonstrated, he says.

"A connection between La Niña and spring tornado activity is often mentioned," Tippett says, "but such a connection really has not been demonstrated in the historical data and hasn't been shown to provide a basis for a skillful tornado activity forecast.

"Our work bridges the gap between what the current technology is capable of forecasting (large-scale monthly averages of rainfall and winds) and tornado activity, which the current technology cannot capture," he says.

The research isn't ready for prime time yet, however, so no official forecast will be made for the upcoming season using these methods.

"This is a useful first step," says Harold Brooks of the National Oceanic and Atmospheric Administration, who was not involved in the study. He says it will be helpful to know, for example, that sometime in the last week of April, conditions will be favorable for lots of tornadoes in the eastern USA.

With greater lead time, a state emergency planner "could be better prepared with generators and supplies," Brooks says.

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