Challenge 1: identify the atmospheric, oceanic and land drivers

Challenge 1 focuses on reconstructing historic multi-year droughts events from 1950 to 2023, with additional storylines developed for these events. These storylines can link observed events to simulated analogies, identifying the frequency of multi-year droughts in the historic record and projecting future changes. This approach can, in turn, indicate the high agreement between models and observations.

The main focus will be on atmospheric and land drivers of multi-year droughts by identifying statistically significant anomalies in the different atmospheric forcing components. This analysis will be the first extensive analysis of multi-year drought drivers for the six focus regions: California, central Argentina, South Africa,Western Europe, India, and Australia. Furthermore, it will enhance understanding of the causal links between anomalies in the ocean, atmosphere, and land during multi-year droughts.

Finally, the impacts of climate change will be quantified by examining changes in mean trends and internal climate variability that cause multi-year droughts. This will be the first trend and variability analysis for future multi-year droughts. Although this analysis will not include feedback from the vegetation and groundwater, it will provide the atmospheric benchmark needed to quantify the impacts of vegetation and groundwater on multi-year drought.

Figure: Map of the number of Multi-Year Droughts (MYDs). Focus regions are denoted by a black lining. For each focus region, the monthly climatology of precipitation (PR, [mm/month], blue bars) and potential evaporation (PET, [mm/month], red line) is shown, including one standard deviation from the mean with small bars for precipitation and shading for PET. In the upper right corner of each region, the total amount of precipitation and PET per year is shown. Regions with sparse vegetation or with permanent snow and ice are masked and shown in white.