A student walks with an umbrella on Northwestern University's Evanston campus. Credit: Northwestern University
Key Points:
- A new study compares rainfall intensity data across two time periods and 17 different U.S. climate regions
- Researchers found increased intensity for all but one region in the eastern U.S.
- The researchers did not detect changes in rainfall intensity along the Pacific Coast or Rocky Mountains.
Northwestern University researchers have discovered that rainfall intensity has increased over the past 70 years for all but one region in the eastern U.S.
In a new study published in Geophysical Research Letters, researchers Daniel Horton and Ryan Harp compared two climatologically distinct time periods: 1951-1980 and 1991-2020. For each time period, they used historical precipitation data from the Global Historical Climatology Network, a publicly available database maintained by the NOAA.
Then, the researchers analyzed the observations within 17 distinct climate regions in the United States. These regions reflect differences in temperature, precipitation, vegetation and ecosystem dynamics.
According to the study findings, precipitation intensity (including rain and snow) increased across much of the United States, particularly in the East, South and Midwest. Changes in the western United States were not detected.
“Not only do we see increasing precipitation intensity for regions east of the Rockies, but the intensities are becoming more variable as well, making water resource management even more challenging,” said Harp.
Indeed, the findings of the study show that when it has rained in recent decades, it’s rained more. In most regions, the intensity of the rainfall shifted from lighter to more moderate and often heavy deluges.
In this study, Harp and Horton narrowed their focus to examine how much precipitation falls during each rain or snowfall event. For their next study, they plan to investigate if annual precipitation is becoming more variable and if precipitation events are becoming more or less frequent.
Increased precipitation intensities affect many sectors, including agriculture and infrastructure, as well as lead to increased risks of landslides and flooding. Horton hopes the study findings can be used by resource managers, policy makers and urban planners to design infrastructure that is more resilient to changing weather patterns.
Information provided by Northwestern University.