Shifting seasonality and increasing frequency of precipitation in wet and dry seasons across the U.S.
Article first published online: 2 AUG 2013
©2013. American Geophysical Union. All Rights Reserved.
Geophysical Research Letters
Volume 40, Issue 15, pages 4030–4035, 16 August 2013
How to Cite
2013), Shifting seasonality and increasing frequency of precipitation in wet and dry seasons across the U.S., Geophys. Res. Lett., 40, 4030–4035, doi:10.1002/grl.50760., , , and (
- Issue published online: 28 AUG 2013
- Article first published online: 2 AUG 2013
- Accepted manuscript online: 19 JUL 2013 05:36AM EST
- Manuscript Accepted: 13 JUL 2013
- Manuscript Received: 25 JUN 2013
- National Science Foundation. Grant Number: AGS-0958907
- Department of Energy. Grant Number: DE-SC0006914
- wet season;
- dry season;
 Water management, agriculture, and ecological systems are sensitive to the frequency and timing of precipitation. Here we document historical trends in these characteristics for station-specific wet and dry seasons over the U.S. from 1930 to 2009. Simulations based on Markovian precipitation occurrence models are used as a null against which to test observed trends without resorting to area averaging. Most regions display increases in precipitation frequency during both wet and dry seasons accompanied by a decrease in length of dry spells. Prominent increases (decreases) occur over the Central and Great Plains during the dry season. An exception is the Atlantic Plains, which experienced a decrease in frequency and an increase in dry spell length, especially during the wet season. Regionally consistent trends in the timing of wet and dry seasons are also evident, particularly over the Ohio (Missouri) River valleys where the dry season now arrives up to 2–3 weeks earlier (later).