Wednesday, May 24, 2017

Dartmouth-Led Study Finds Heavier Precipitation in the Northeast Began in 1996

The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and end points of the trends for 1958 to 2012. (Figure source: updated from Karl et al. 2009) Click to Enlarge.
Over the past century, the Northeast has experienced an increase in the number of storms with extreme precipitation.  A Dartmouth-led study finds that the increase in extreme Northeast storms occurred as an abrupt shift in 1996, particularly in the spring and fall, rather than as a steady change over several decades. The findings were published in an early online release of the American Meteorological Society's Journal of Hydrometeorology.

With climate change, a warmer atmosphere is able to hold more moisture, which is likely to affect the frequency, intensity and location of extreme precipitation.  Understanding historical changes in extreme storms, including in the Northeast, can improve our understanding of future precipitation projections with continued climate change.

"Looking at where the increases in extreme precipitation are occurring across the Northeast, interestingly we find that it's not just one part of the Northeast, say the coast, that is experiencing more heavy rainfall events, it's relatively uniform across the region," says Jonathan M. Winter , assistant professor of geography at Dartmouth, who served as one of the co-authors of the study.

For the study, the Northeast is defined as Maine, New Hampshire, Vermont, Mass., Conn., R.I., N.J., N.Y., Pa., Md., DC, Del., and W.Va., and draws on weather station data from the Global Historical Climatology Network, which is compiled by the National Oceanic and Atmospheric Association National Climatic Data Center.  The threshold for extreme precipitation events depends on the station but regionally averaged is about 2 inches or more of rain in a day.

Read more at Dartmouth-Led Study Finds Heavier Precipitation in the Northeast Began in 1996

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