Event Scale Variations in Water Isotopes: What Do They Tell Us?

Spatial and temporal stable isotope variability in precipitation is attributed to a number of factors including water vapor source, temperature of condensation, and the amount of water removal during transport. Most precipitation data, ∂D and ∂¹⁸O, is collected at weekly or daily timescales and measurements of event scale variations in ∂D and ∂¹⁸O are less common, but could yield insight into cloud processes and dynamics. We collected precipitation on minute to hourly timescales in the Midwestern US during the summer of 2018. The individual storms varied in type and included tropical storm Alberto, a well-developed tropical cyclone, frontal systems that were intense but of short duration, and prolonged rains of several days. Each storm type exhibited distinctive isotopic patterns that were related to condensation heights, water recycling, and water removal rates. For example, precipitation from Alberto had significantly lower ∂D and ∂¹⁸O values relative to that in typical summer precipitation in the Midwest, and had large difference within the cyclonic structure. The data suggests rapid sampling of precipitation and analysis of its stable isotopes can give insights into the cloud physics that induce precipitation.