Global relevance of atmospheric and land surface drivers for hot temperature extremes

Abstract. Hot temperature extremes have severe impacts on society and ecosystems. Their magnitude and frequency are increasing with climate change in most regions globally. These extremes are driven by both atmospheric and land surface processes such as advection or reduced evaporative cooling. The contributions of the individual drivers to the formation and evolution of hot extremes have been analyzed in case studies for major past events, but the global relevance of drivers still remains unclear. In this study, we determine the relevance of (i) atmospheric drivers such as wind, geopotential height, geopotential height differences and surface net radiation, as well as (ii) land surface drivers such as evaporative fraction and enhanced vegetation index for hot extremes across the globe using observation-based data. Hot extremes are identified at daily and weekly time scales through the highest absolute temperature and an analogue-based approach to determine the relevance of the considered drivers. The results show that geopotential height at 500 hPa is overall the most relevant driver of hot extremes across the globe. Surface net radiation and enhanced vegetation index are the second most relevant drivers in many regions, particularly in tropical and semi-arid areas. We find that the relevance of land surface drivers is increasing within the studied period, and from daily to weekly durations. Revealing key regions and influential time scales of land surface drivers on hot extremes can inform more efficient prediction and management of the increasing threat these extremes pose.