This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Since the 1950s, the Tibetan Plateau has experienced pronounced warming and wetting. However, an overall shift toward wetter conditions does not necessarily mean that drought risk has diminished.
On the contrary, against the backdrop of continued warming, compound hot-dry events—characterized by the simultaneous occurrence of high temperatures and drought—have become an increasingly important climate risk across the plateau. Such extremes can directly affect ecosystems and water resources, accelerate glacier retreat and permafrost degradation, destabilize glaciers and high-mountain geomorphic systems, and potentially increase the risk of secondary hazards such as ice avalanches and landslides. Yet the processes governing the year-to-year variability of these compound hot-dry events remain poorly understood.
A recent study, published in Journal of Geophysical Research: Atmospheres and led by Professor Tianjun Zhou's research team at the Institute of Atmospheric Physics, Chinese Academy of Sciences, has helped fill this knowledge gap. "We found that the year-to-year swings in these compound hot-dry events are not random—they are largely steered by two major climate modes: ENSO and the Summer North Atlantic Oscillation," says lead author Rongyun Pan, a doctoral candidate at the institute. The study shows that these large-scale patterns modulate atmospheric circulation and surface energy balance across the plateau, driving alternating hot-dry and cool-wet summers.
The researchers used the High-Resolution Near‐Surface Meteorological Forcing Data set for the Third Pole region (TPMFD), together with the CN05.1 observational data set and ERA5 reanalysis, to investigate the spatiotemporal characteristics of summertime compound hot-dry events over the Tibetan Plateau since 1979. The results show that ENSO conditions during the preceding winter exert a pronounced influence on compound hot-dry events over the southwestern Tibetan Plateau in the following summer. During El Niño years, the regional mean number of compound hot-dry days increases by approximately 1.85 days, whereas during La Niña years, it decreases by about 1.13 days.
In general, stronger ENSO events tend to produce a more pronounced modulation. The researchers further distinguished between eastern Pacific (EP) and central Pacific (CP) types of ENSO. During EP El Niño years, the number of hot days can increase by more than 7 days in parts of the southwestern plateau, while the regional mean number of drought days increases by 11.4 days.
This enhancement is associated with changes in cloud radiative effects and clear-sky shortwave radiation, which together increase the amount of energy received by the land surface. In contrast, CP La Niña exerts the strongest suppressing effect on compound hot-dry events. Changes in cloud radiative effects and surface albedo reduce the energy input to the land surface, favoring the persistence of cooler and wetter conditions.
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