Rainfall Intensity Changes in the Southeastern U.S. - Observations, Projections, and Adaptations.

The distribution of rainfall has major impacts on crop production, affecting soil, water balance, and plant health in agricultural systems.  In this study we examined if there have been changes in rainfall intensity and seasonal rainfall variability in recent decades in the Southeastern U.S.  Daily rainfall records from the Global Historical Climatology Network were used to analyze changes in rain intensity and also to calculate seasonal rainfall totals to examine changes in rainfall variability.  Stations having continuous records during the past 60 years, 1954-2013 were used.  During the last 30 years, there has been an increase in the number extreme rain events (> 152.4 mm/day) and decreases in the number of moderate intensity (12.7 – 25.4 mm/day) and heavy (25.4 – 76.2 mm/day) rain events in the Southeast U.S., when compared to the previous 30-year period.  There have also been significant decreases in the return period of months in which greater than half of monthly total rain occurred in a single day.  The variability in spring and summer rainfall increased during the last 30 years, but winter and fall had less variability in seasonal totals in the last 30 years.  In agricultural systems, rainfall is one of the leading factors affecting yield variability; so it can be expected that more variable rainfall and more intense rain events could bring new challenges to agricultural production.  However, these changes can also present opportunities for producers who are taking measures to adjust management choices to make their systems more resilient to increased rain intensity and variability.  We discuss residue and tillage management as some ways that producers have been changing management to make their systems more resilient in a changing world.