Role of climatic oscillations in causing spatially and temporally compound droughts and heatwaves

Compound drought and heatwaves (CDHWs) often cause severe ecological and socioeconomic damages; however, these impacts amplify when such temporally compound events occur concurrently in distant regions. Although spatially concurrent univariate extremes (e.g., droughts) have been explored globally and usually linked to large-scale climatic oscillations, such as El-Niño Southern Oscillation (ENSO) and global warming, spatial co-occurrence of CDHWs remains understudied. Here, we present a novel methodology to identify regions that have higher-than-expected chances of experiencing CDHWs concurrently. Using daily precipitation and temperature data from Climate Prediction Centre (CPC) and ERA5, we find robust spatially concurrent CDHWs in multiple regions that are thousands of kilometres apart, revealing teleconnections in CDHWs. Composite anomalies of geopotential heights and sea surface temperatures reveal El-Niño as the major cause of teleconnections in CDHWs in tropical and sub-tropical regions. Height anomalies during extra-tropical teleconnections reveal quasi-stationary Rossby waves that often produce persistent atmospheric blockings over climacteric locations in vicinity of compound regions. The insights gained here offer new avenues in studying spatially and temporally concurrent hydrologic extremes.