Science Source

How spatially coherent and statistically robust are temporal changes in extreme precipitation in the contiguous USA?

States that century-long precipitation records from stations in the contiguous USA indicate an increased frequency of rainy days over the past century and some evolution in the probability distributions of precipitation amount
Finds there is substantial variability in terms of the magnitude, significance and sign of the linear trends with specific metrics, and they are sensitive to recording bias of light precipitation events in the early part of the 20th century
Finds that the majority of stations that exhibit significant linear trends show evidence of increases in the intensity of events above the 95th percentile
Finds that the largest trends towards increased annual total precipitation, number of rainy days and intense precipitation (e.g. fraction of precipitation derived from events in excess of the 90th percentile value) are focussed on the Central Plains/northwestern Midwest