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future policy, Bales and Miller with the Sierra Nevada Research Institute wrote that the state “is likely to experience 50 percent to 150 percent more critically dry years [with] water availability … certain to be more variable.” “It is likely that a multiyear drought

will occur, as has occurred numerous times in the past; however, future droughts may be longer lasting,” Bales and Miller wrote.

Northern California, the wettest region of the state, is projected to have increased warming with early snowmelt and runoff. This will be coupled with “more intense winter storm events” at inland and coastal locations, resulting in fl oods, according to Bales and Miller, who noted that “perturbations to our water supply will stress both infrastruc- ture and decision-making capabilities.” Though Southern California

is expected to receive “intense pre- cipitation events” during the winter, it is “very likely to have an overall reduction in precipitation,” Bales and Miller wrote. The “most serious threat” because of climate change is a decrease in fresh water and an increase in in- tense wildfi res. A March 2013 report by the U.S. Forest Service said a changing climate could cause burned areas in the West to increase “by more than 50 percent by the middle of this century.” In July, the Interior Department announced the Western Watershed Enhancement Partnership, an effort with the Department of Agriculture that aims to identify and mitigate risks of wildfi re to key water supply sources and hydroelectric facilities. Flows of sediment, debris and ash into streams and rivers after wildfi res can damage water quality and often require millions of dollars to repair damage to habitat, reservoirs and facilities.

Forecasting the Future While regions seek ways to adapt, offi cials are striving to improve the knowledge about how the changing climate will affect the weather. The National Oceanic and Atmospheric Administration’s Climate Prediction Center does 30-day, 60-day and 90-day

July/August 2013

outlooks but “those products are not useful for people like water managers because they only target certain areas of the country and the skill is really low,” said Jeanine Jones, interstate resources manager with DWR. Changing conditions call for improved weather forecasting so that the brunt of extreme conditions can be better absorbed. “We do badly now and that’s why we have been pushing the science community on it because it’s actually a real problem area in the science,” Jones said. “Operational weather forecasting models are used for out to about 10 days and then research climate models are run for decadal to century scales, but there is a huge gap in between at the most practical part of the time series.”

A 2010 report by the National Research Council noted that current forecast systems “have limited ability on the timescale of a few weeks to a few years because models for such climate forecasts must take into ac- count complex interactions among the ocean, atmosphere, and land surface, as well as processes that can be diffi cult to represent realistically.” This sets specifi c research goals for improving under- standing of sources of predictability and suggests best practices to improve methods of making and disseminating forecasts.

Because the meteorology research community is different from the climate science research community and sea- sonal forecasting “falls in the gray area in between the two, there has not been a lot of research dollars and priority given to seasonal forecasting, which is one reason why we have been pushing the research community on it, to try and give it a higher priority,” Jones said. One area that shows promise is atmospheric rivers (ARs) – the narrow conveyer belts of water vapor that can cause fl ooding in certain circumstances. On the West Coast, strong atmospheric rivers bring a signifi cant amount of deep tropical moisture across the Pacifi c Ocean towards the West Coast. “We are pushing for research on the concept there may be some

With climate change, most experts predict more precipitation will fall as rain instead of snow.

Watch a NASA video about climate change


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