Analysis of Long-Term Precipitation Sequencing Pattern Changes in North America

Abstract:

This study evaluates changes in long-term precipitation patterns in North America, focusing specifically on precipitation sequencing. Previous precipitation studies have explored changes in extreme precipitation events, intensity, and distribution, but sequencing changes and their effects are still largely not understood. Precipitation sequencing, or the overall temporal pattern of precipitation events, is a vital yet often overlooked part of developing long-term climate predictions; the assumption of long-term stationarity in climate variability, which suggests that past observed temporal patterns are likely to continue and can therefore be projected, weakens the robustness of climate models. Additionally, changes in sequencing could be a driver for fluctuations in the highly interconnected hydrologic cycle, meaning that tipping points and critical changes in the cycle could be better anticipated given a more complete picture of long-term temporal patterns.

Analysis was based on precipitation data collected by the National Climatic Data Center for approximately 9000 stations in North America. Temporal patterns recorded at each station – the sequence of consecutive days with or without rain and the lengths of those increments – were reviewed and compared on a decadal and seasonal scale. Comparisons to date indicate that long-term precipitation patterns are non-stationary and therefore cannot be relied upon for long-term climate projections. It remains to be seen how exactly regional temporal patterns have fluctuated over time in North America, and results could provide interesting insight into observed hydrologic changes or serve to reinforce existing theories regarding regional hydrologic studies.