Extreme weather events like heatwaves have captured global attention in recent years due to their devastating effects on human health, agriculture, and the environment. One of the most notorious examples is the 2003 European summer heatwave, which caused widespread fatalities, economic damage, and long-term ecological impacts. While such heatwaves are often attributed to local atmospheric conditions, our research uncovers the surprising interannual predictability of this event and its attribution to the Tibetan Plateau (TP).
Known as the "Third Pole", the TP plays a significant role in shaping global weather patterns through its unique geographic and atmospheric characteristics. Acting as a massive heat source, the TP influences the large-scale circulation patterns in the atmosphere, particularly during boreal summer. The plateau’s ability to generate Rossby waves—large atmospheric waves that propagate across continents—connects the TP with distant regions, including Europe. Our study uncovers how TP land conditions, especially its snow cover, contributed to the interannual predictability of the 2003 European heatwave.
Using a newly developed weakly coupled land data assimilation system, we incorporated land observations only over the TP into the coupled climate model. Remarkably, our model simulations show substantial skill in predicting the 2003 European heatwave two years in advance, reproducing the large-scale temperature anomalies and high-pressure systems over Europe during that summer (Figure 1). This underscores the TP’s significant influence on the atmospheric circulation patterns that drove the heatwave and demonstrates how local land data from the TP can enhance the predictability of such extreme events.
In our analysis, we found that the key mechanism linking the TP to the 2003 European heatwave lies in the snow cover anomalies over the TP (Figure 2). A reduction in spring snow cover over the TP in 2003 led to increased surface heating, which initiated a distinct Rossby wave train. This wave train propagated across Eurasia, ultimately generating high-pressure anomalies over Europe during the summer. The high-pressure system reduced cloud cover and increased net surface radiation, contributing to the extreme temperatures experienced during the heatwave. This physical process demonstrates the far-reaching impact of the TP’s land conditions on European climate, creating a favorable environment for extreme weather events.
Beyond its influence on atmospheric circulation, the TP also played a significant role in modulating ocean conditions during this period. The TP's land states affected sea surface temperatures (SST) in both the Atlantic and Pacific Oceans, further enhancing the predictability of extreme events like the 2003 European heatwave. Figure 3 shows improved initial SST anomalies in January 2001 due to the TP's remote influence. By incorporating TP land data into our climate model, we were able to better simulate the cooling over the tropical Atlantic and tropical eastern Pacific, demonstrating the TP’s broader influence on oceanic and atmospheric systems.
Our findings not only enable a better understanding of the past—they have important implications for the future of climate prediction. By incorporating data from the TP into climate models, we can potentially improve predictions of extreme weather events, not only in Europe but in other regions connected to the TP through atmospheric teleconnections. This research paves the way for improving subseasonal-to-decadal climate forecast foundational to developing better early warning systems that can give communities more time to prepare for extreme heat events, potentially saving lives and reducing economic losses.
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