Aug 1, 2015

An intensified seasonal transition in the Central U.S. that enhances summer drought

S.‐Y. Simon Wang, Joseph Santanello, Hailan Wang, Daniel Barandiaran, Rachel T. Pinker, Siegfried Schubert, Robert R. Gillies, Robert Oglesby, Kyle Hilburn, Ayse Kilic, Paul Houser
Journal of Geophysical Research: Atmospheres
  • States that in the long term, precipitation in the Central U.S. decreases by 25% during the seasonal transition from June to July
  • States that this precipitation decrease has intensified since 1979 and such intensification could have enhanced spring drought occurrences in the Central U.S., in which conditions quickly evolve from being abnormally dry to exceptionally dry
  • Analyzes various atmospheric and land reanalysis data sets to examine the trend in the June–July seasonal transition
  • Finds that the intensified deficit in precipitation is accompanied by increased downward shortwave radiation flux, tropospheric subsidence, enhanced evaporative fraction, and elevated planetary boundary layer height, all of which can lead to surface drying
  • Finds that the change in tropospheric circulation was characterized by an anomalous ridge over the western U.S. and a trough on either side—a pattern known to suppress rainfall in the Central U.S.
  • Concludes that this trending pattern shows similarity with the progression of the 2012 record drought