Klos, P. Z., Link, T., Abatzoglou, J. (2014). Extent of the rain-snow transition zone in the western U.S. under historic and projected climate. Geophysical Research Letters
This study investigates the extent of the rain-snow transition zone across the complex terrain of the western United States for both late 20th century climate and projected changes in climate by the mid-21st century. Observed and projected temperature and precipitation data at 4 km resolution were used with an empirical probabilistic precipitation phase model to estimate and map the likelihood of snow versus rain occurrence. This approach identifies areas most likely to undergo precipitation phase change over the next half century. At broad scales, these projections indicate an average 30% decrease in areal extent of winter wet-day temperatures conducive to snowfall over the western United States. At higher resolution scales, this approach identifies existing and potential experimental sites best suited for research investigating the mechanisms linking precipitation phase change to a broad array of processes, such as shifts in rain-on-snow flood risk, timing of water resource availability, and ecosystem dynamics.
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Klos, P. Z., Link, T., Abatzoglou, J., Kavanagh, K. (). Changes in the climatic water balance and precipitation phase under a warming climate: Implications for terrestrial ecosystems in the Columbia River basin. Submission planned for Hydrology and Earth Systems Science, Spring Semester 2015
Understanding the sensitivity of seasonal water availability dynamics to temperature changes is crucial to assess the potential vulnerability of ecosystems in a warming climate. The seasonal cycle of precipitation and evaporative water demand generally occurs asynchronously across much of the Columbia River Basin, thereby resulting in ecosystems that are dependent on a combination of snowpack and subsurface storage to retain water accumulated during the wet season for use in supporting evaporative demand during the dry season. To understand how the spatial extent of ecosystems may potentially shift due to changes in evaporative demand and water availability under warmer temperatures, we mapped and identified the overlapping effects of: 1) changes in potential evapotranspiration and the climatic water balance, 2) the shift in the rain-snow transition zone, and 3) a new climatic index for identifying the importance of combined snowpack and subsurface storage to sustain vegetation through the extended dry season. We based assessments on historical conditions and mid-21st century projections using an ensemble average of 12 global climate model outputs downscaled to 800 m. The results suggest that terrestrial ecosystems in the mid-elevation regions of eastern Washington, eastern Oregon, and Idaho may be particularly sensitive to multiple overlapping warming-induced changes, including a shift from snow- to rain-dominated precipitation, greater reduction in the climatic water balance relative to other higher elevation locations in the region, and a high index of precipitation and evapotranspiration asynchroneity.
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