Drivers of drought and its propagation in the Southern Peruvian Andes

The southern Peruvian Andes is vulnerable to droughts, with impacts on agriculture and hydropower production, and wildfire frequency. Previous research has focussed on the processes controlling precipitation variability in the region, while the drivers of drought propagation, from meteorological drought to soil moisture, vegetation and hydrological drought, remain unconstrained. We analyse large-scale climate variability and daily atmospheric circulation patterns to gain new insights into the spatial-temporal variation of the processes that enhance or inhibit the development of drought and its propagation during the period 1985-2020. Across all seasons, meteorological drought is broadly driven by an upper tropospheric westerly wind anomaly and weaker convection in the western Amazon. However, the climatic processes that cause these anomalies vary in time and space. During the onset of the wet season drought is driven by La Niña, while during the termination of the wet season drought typically occurs under El Niño. Droughts are more likely when the Pacific Decadal Oscillation is in phase with the El Niño-Southern Oscillation, while the influence of tropical Atlantic sea surface temperature is variable and often weak. The propagation to soil moisture drought occurs on short timescales, typically less than a month, and is enhanced by favourable climatic conditions, while hydrological drought is buffered by catchment-scale processes. The modulation of drought propagation by vegetation cover and local hydrological processes in the southern Peruvian Andes suggests that the region may see notable benefits from a localised impact-focussed drought forecasting system.