The Connection between Meteorological Drought and Extreme Rainfall

Meteorological drought can have devastating and widespread economic and societal effects around the globe. These effects make understanding drought variability and its underlying causal processes imperative for constraining estimates of the return periods of drought, for the prediction of drought and for understanding possible future changes to meteorological drought with anthropogenic climate change. While some climatological processes causing drought, for example SST patterns and variability, are relatively well known, the atmospheric and meteorological processes associated with drought variability and change are nuanced and remain elusive. In particular, the characteristics of daily rainfall during periods of drought globally have rarely been explored.

This study presents the relationships between meteorological drought and the characteristics of daily rainfall in the historical period. Meteorological droughts, defined as rainfall deficits occuring on time scales of 3-months, 6-months, 12-months and 24-months using the Standardized Precipitation Index (SPI), are compared to variability in the frequency and intensity of daily rainfall events to determine if there are consistent changes in these daily-scale rainfall characteristics during drought. Some past studies highlight that in some geographical regions, such as southeast Australia, prolonged meteorological drought is more closely associated with a lack of extreme rainfall rather than changes to mean intensity or the frequency of daily rainfall events. Therefore, particular focus is given to the connection between meteorological drought and characteristics of extreme daily rainfall using several extreme precipitation indices from the ETCCDI. Exploring the connection between meteorological drought and the characteristics of daily rainfall is the first step for revealing important information about the changes in meteorological processes that are associated with meteorological drought around the world.