This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought.
Summer drought is often, but not always, accompanied by periods of extreme daily maximum temperatures or "heat waves", the physical link being that changes in the surface energy balance favor increased sensible heating during drought. While climate model projections agree that 21st century surface air temperatures are likely to increase over most land areas (favoring heat waves), considerable uncertainty surrounds the projected changes of precipitation (and therefore of drought), particularly on regional scales. This project is a first look at the joint occurrence of heat waves and drought in newly available climate change projections. The deleterious consequences of the simultaneous occurrence of these extremes make the topic of great practical, as well as scientific, interest.
The research will focus on the highly vulnerable, drought-prone region of southern Africa. The investigators will make initial efforts to address the following open questions: How well do coupled models reproduce the observed statistics of joint drought/heat waves over the last half-century? How does this joint occurrence change in 21st century climate projections? To what extent can any such changes be related to changes in surface fluxes? Various meteorological drought indicators based on precipitation, as well as precipitation minus surface evaporation, will be considered. A warmer climate generally increases the probability of extreme daily temperatures and is expected to intensify surface drying in summer. With precipitation projections less clear, the study may provide insight into changes in the relative roles of temperature and precipitation on the joint occurrence of heat waves and drought in climate change projections.
Broader impacts of these studies stem from the impacts on food production of drought when it is coupled with severe heat, which increases water losses from crops and stresses livestock. Improved knowledge of the risk of combined droughts and heat waves, as well as the changes in this risk in the 21st century, will be valuable to decision makers in the agricultural and food distribution sectors.
