Severe Drought

Drought is deficiency of precipitation over an extended period of time resulting in water shortage. Severe drought according to the Standardized Precipitation Index (SPI) is cumulative precipitation depth that maps to an SPI of -1.5 or less and is in the lowest five percent of observed SPI values.

Using Weather Attribution for Robust Representation of Present and Future Extreme Weather Events

Weather attribution estimates the current and near future likelihood for a recently observed extreme weather event, like a drought or hurricane. It uses climate models, weather prediction models, and observed weather to determine how much more likely the observed event is today relative to the recent past, like the 1990s and 2000s. In this study, a statistical weather generator (WG) creates synthetic sequences of future precipitation, temperature, and potential evapotranspiration that represent the increased likelihood for three-month severe drought. An independent weather attribution study identified that three-month severe drought is five times more likely to occur today relative to recent historical conditions. The WG-simulated conditions portray a near future where historical extreme and severe drought are significantly more likely to occur. The climate description produced by this WG is representative of the weather attribution study and is significantly hotter, with lower expected soil moisture than the future climate description obtained from global circulation, i.e., climate, model (GCM) simulation results (by themselves).