Tuesday, August 01, 2017

Successful Prediction of Multi-Year US Droughts and Wildfire Risk

Longer-term forecasts will benefit agriculture and natural resource management.

{Frequency distributions of simulated (a) precipitation (defined as precipitation anomaly divided by climatological mean), (b) total soil water, and (c) fire season length anomalies averaged over southwestern North America (28°N–44°N, 125°W–100°W) for the natural (i.e., unforced) variability during 1960–2015 (black) and the external (blue) and the ocean + external components during the period 2010–2014 (red). The frequency distribution of natural variability (NAT) is determined by calculating the water year deviations of individual ensemble members from the ensemble mean in UR (uninitialized forced run) for 1960–2015 (i.e., ensemble spread in the uninitialized run). The frequency distributions of external and ocean + external components are estimated from the water year anomalies of individual ensemble members during 2010–2014 in UR and AR (ocean data assimilation run), respectively (i.e., 50 samples in each). A Kernel smoothing function is applied to these distributions. Plots were generated using the NCAR Command Language (Version 6.3.0) [Software]. (2016). Boulder, Colorado: UCAR/NCAR/CISL/TDD} Click to Enlarge.
The next mega-droughts and subsequent active wildfire seasons for the western U.S. might be predictable a full year in advance, extending well beyond the current seasonal forecast and helping segments of the economy related to agriculture, water management and forestry.

The new model, developed by an international team of scientists from the U.S., South Korea and U.K., and led by Utah State University climate scientist Yoshimitsu Chikamoto, was reported in the July 26 edition of Scientific Reports.

The source of this improved predictability is based on a combination of factors, including tropical climate variability, global climate change and the natural filtering effects of soils.  To mitigate drought-induced socioeconomic risks, water resource managers require detailed drought forecasts as far in advance as possible.  Climate prediction centers generate and routinely disseminate seasonal drought outlooks.  However, predicting multi-year droughts that reach well beyond seasonal timescales is challenging for climate scientists.

Over the past 15 years, parts of the western U.S. have experienced severe drought conditions and an increasing number of wildfires that take a toll on people and ecosystems.  The team's research shows that in addition to contributions from natural forcings and global warming, temperature differences between the Atlantic and Pacific oceans play a role in causing drought and increasing wildfire risks.  The new findings show that a warm Atlantic and a relatively cold Pacific enhance the risk for drought and wildfire in the southwestern U.S.

Read more at Successful Prediction of Multi-Year US Droughts and Wildfire Risk

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