The standardized precipitation evapotranspiration index (SPEI) was summarized for the Upper Green River Basin to quantify climate variability over the last century. The SPEI incorporates both precipitation and temperature data, therefore the index has the capacity to include the effects of temperature variability on drought. The SPEI considers the difference between precipitation and potential evapotranspiration to calculate a climatic water balance at a given time scale (Vicente-Serrano et al. 2010). The number of standard deviations the climatic water balance deviates from the long-term mean for a given time period represents the SPEI for the time period. Here, I calculated the SPEI for each water year (Oct-Sept) between 1896 and 2017. The SPEI score is shown on the y-axis and time on the x-axis. Years in red indicate a lower SPEI than the long-term mean, whereas years in blue indicate a higher SPEI than the long-term mean. Data (4km2 SPEI data) was obtained from the Western Regional Climate Center (http://www.wrcc.dri.edu; accessed 14 January 2017) and calculated the water year mean (12-month data) for the Upper Green River Basin. Literature Cited Vicente-Serrano, S. M., S. Begueria, and J. I. Lopez-Moreno. 2010. A multiscalar drought index sensitive to global warming: The standardized precipitation evapotranspiration index. Journal of Climate 23:1696-1718.
