Water Resources Research Act Program

Principal Investigators: Gabriel Bromley

Abstract: Understanding changes to the hydroclimatology of food producing regions is a grand challenge for climatescience as identified by the “Water for the Food Baskets of the World†initiative of the World Climate ResearchProgram. Montana’s hydroclimate is rapidly changing. The Montana Climate Assessment found thatprecipitation is increasing in the eastern half of the state but also acknowledged that more research is neededto investigate precipitation timing and form (Whitlock et al. 2017). New work has shown that positiveprecipitation trends are stronger in more recent decades and are occuring preferentially during the early warmseason (Figure 1) (Bromley et al. 2019; Gerken et al. 2018). I propose to further investigate these recentchanges in warm season precipitation with a focus on extreme precipitation events that are increasingin frequency across Montana and central North America.Precipitation is predicted to increase with rising temperatures,and this increase is likely to occur in larger, more intense events(Trenberth et al. 2003). A warmer atmosphere enables moreatmospheric moisture, specifically about 7% more moisture per 1° Cincrease in temperature, according to the Clausius-Clapeyronrelationship. Extreme precipitation intensities at sub-daily timescalesare increasing at a similar rate, while lower intensity precipitation hasbeen decreasing (Prein et al. 2017). Most warm season precipitationis associated with mesoscale convective systems (MCSs), which areprimarily responsible for the observed increases in precipitationintensity and frequency (Feng et al. 2016). The implications of thesechanges are that for the northern North American Great Plains (NNAGP), an increase in extreme precipitationis possible through the intensification of warm season MCSs, but these types of precipitation events inMontana and their changes have not been studied to date.