An improved understanding of the interacting factors that influence the evolution and severity of droughts in the USA in present and future climates

The increasing demands that will be placed on the water and agricultural resources of the
USA in the future as populations rise and the climate changes, make an improved understand-
ing of drought, its predictability, severity and projected future changes, more critical than
ever. The unfortunate truth is that our ability to accurately forecast individual droughts will
always be limited by the important role played by internal atmospheric variability, which is
inherently unpredictable on the timescales of relevance for seasonal to decadal drought. One
area, where we could still make substantial progress toward improving drought predictability,
is in our understanding of the role of complex and non-linear feedback processes in altering
drought severity and impacts. If we can understand all the relevant feedback processes that
play a role in drought evolution, faithfully represent them in our models, and understand
how they are projected to change in a warmer climate, this will go a long way to enhancing
our capacity to predict impacts arising from drought events.

Using a state-of-the-art Earth System Model (ESM), the community Earth System Model
(CESM), we will fully characterize the role of land-atmosphere coupling processes
in governing drought severity. Capitalizing on recent land- and atmosphere-model im-
provements, we will use a constrained circulation ensemble approach to systematically
quantify how the inclusion of a variety of land-atmosphere processes impact on
the evolution and severity of drought events and how we expect these impacts
to change in a warmer climate. These processes include plant hydraulics, dust emis-
sions, irrigation, wildfires, and dynamic vegetation. We will also compare with a variety of
observational data sets and case studies to examine the fidelity of the model’s representation
of drought events. This will lead to improved understanding of the origins and projected
changes in drought and will, for the first time, quantify in a controlled and systematic
manner, the impact of land-atmosphere coupling processes that are at the forefront of our
modeling capabilities.

Broader impacts and relevance to competition: This research will advance our funda-
mental understanding of the complex interacting feedbacks that influence drought severity
and determine their impacts, both in the present and future climate. This will improve our
capacity to predict drought in the near and long term using ESM’s and will inform model
development efforts worldwide by the identification of important interacting processes that
should be included for accurate drought simulation. This research is therefore of direct
relevance to the call and to MAPP in general. The information gained has the potential
to inform agricultural and water resource management, ultimately benefiting society as a
whole. It will provide a new dimension to drought monitoring and attribution studies, such
as those performed by the NOAA Drought Task Force, by increasing our capacity to isolate,
and understand, the role of land-atmosphere coupling processes in drought severity.

Climate Risk Area: Water Resources