Characterization of increased persistence and intensity of precipitation in the Northeastern United States.

We present evidence of increasing persistence in daily precipitation in the Northeastern United States that suggests global circulation changes are affecting regional precipitation patterns. Meteorological data from 222 stations in 10 Northeastern states are analyzed using Markov Chain parameter estimates to demonstrate that a significant mode of precipitation variability is the persistence of precipitation events. We find that the largest region-wide trend in wet persistence (i.e., the probability of precipitation one day, given precipitation the preceding day) occurs in June (+0.9 percent probability per decade over all stations). We also find that the study region is experiencing an increase in the magnitude of high intensity precipitation events. The largest increases in the 95th percentile of daily precipitation occurred in April with a trend of +0.7 mm per day per decade. We discuss the implications of the observed precipitation signals for watershed hydrology and flood risk.

Supporting Material (Map; station numbers, names, locations and heights)

Plain English Discussion

Analysis of climate stations with more than fifty years of data shows that high rainfall events are increasing in the Northeastern US (largest increase in April); and rain events are lasting longer (largest increase in June. So the risk of rivers flooding is growing.

Related Topics

• Climate,
• Hydrology