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Wednesday, April 11 • 2:15pm - 2:30pm
MODELLING CLIMATE AS PROCESS DRIVERS: Evaluating Drought Projections with the Cumulative Drought Severity Index

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AUTHORS: Matthew Peters, Louis Iverson – USDA Forest Service Northern Research Station

ABSTRACT: Downscaled climate projections from general circulation models (GCM) are widely used to evaluate potential scenarios of climate change. However, many evaluations focus on changes in precipitation and temperature, but rarely examine the potential interactions of the two. We calculated monthly self-calibrated Palmer drought severity index (PDSI) values for the period 1980 – 2099 using interpolated climate and downscaled GCM data under the representative concentration pathways (RCP) 4.5 and 8.5 for the conterminous United States. A snowmelt function was used to account for precipitation occurring during the winter, and soil moisture to a depth of 150 cm allows us to better examine drought and moisture conditions for trees, which have deep root systems that can access water well below the surface. The time-series PDSI were evaluated among three future periods (2010 – 2039, 2040 – 2069, 2070 – 2099) against the calibration period (1981 – 2010) to formulate a cumulative drought severity index (CDSI) and a cumulative moisture severity index (CMSI). The CDSI and CMSI weight the intensity of conditions by the frequency for a period (e.g., 30 years), resulting in a single value. Results from the GCMs evaluated indicate that for much of the U.S., more intense or frequent drought conditions are expected as compared to the calibration period, though differences are apparent among the two RCPs by the end of the century.

Wednesday April 11, 2018 2:15pm - 2:30pm CDT
LaSalle 1 (7th Floor)