Atmospheric circulation to constrain subtropical precipitation projections
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Revealing the hidden link of the Walker circulation on heavy rainfall patterns in the Eastern Pacific
Understanding the relationship between tropical heavy rainfall and large-scale circulation provides valuable insights for improving the climate models. Here we use Gaussian Mixture Model to identify two distinct types of heavy rainfall over the tropical Pacific, “strong deep convection” and “moderately strong deep convection,” using satellite-borne precipitation radar measurements. They differ in two typical climatological deep convection-related rainfall modes between the western and eastern Pacific regions. The occurrence frequency of moderately strong deep convection is significantly different between the western and eastern Pacific, potentially linked to the Walker circulation. The enhanced Walker circulation appears to weaken the local Hadley circulation, thereby reducing strong deep convective activity in the eastern Pacific. This increases moderately heavy rainfall and decreases diabatic heating, which can affect global climate. We propose incorporating the close link between large-scale Walker circulation and mesoscale heavy convective rainfall into the current climate models.
Onshore intensification of subtropical western boundary currents in a warming climate
Subtropical western boundary currents (WBCs) refer to swift narrow oceanic currents that flow along the western edges of global subtropical ocean basins. Earlier studies indicated that the WBCs are extending poleward under a warming climate. However, owing to limited observations and coarse resolution of climate models, how greenhouse warming may affect the zonal structure of the WBCs remains unknown. Here, using seven high-resolution climate models, we find an onshore intensification of the WBCs in a warming climate. The multimodel ensemble mean of onshore acceleration ranges from 0.10 ± 0.08 to 0.51 ± 0.24 cm s−1 per decade over 1950–2050. Enhanced oceanic stratification associated with fast surface warming induces an uplift of the WBCs, leading to the projected change. The onshore intensification could induce anomalous warming that exacerbates coastal marine heatwaves, reduces ability of the coastal oceans to absorb anthropogenic carbon dioxide and destabilizes methane hydrate stored below the sea floor of shelf regions.
The 2023 Türkiye-Syria earthquake disaster was exacerbated by an atmospheric river
Strong earthquakes in mountain landscapes can trigger widespread slope failures, initiating chains of multiple hydro-geomorphic hazards. These impacts disrupting ongoing response operations may be amplified by extreme post-seismic precipitation delivered by atmospheric rivers (ARs). However, to our knowledge, cases of ARs following major earthquakes have not been previously documented. Here, we document the combined effects of seismic and precipitation extremes that perturbed the area struck by the February 6, 2023, Türkiye-Syrian earthquakes. Strong ground shaking triggered thousands of landslides, and 36 days later, an exceptionally strong AR delivered up to 183 mm of precipitation in just 20 hours. This extreme precipitation induced additional landslides, debris flows, and flooding, disrupting recovery efforts, affecting temporary settlement areas, and claiming more lives. This cascade of hazards highlights the need to integrate seismic and weather extremes into rapid hazard assessment protocols to enhance disaster preparedness and response.
Enhanced risk of hot extremes revealed by observation-constrained model projections
The increasing frequency of extreme hot events poses significant societal and scientific challenges due to their adverse impacts on human and natural systems, compounded by their unpredictable nature. Climate models are essential for investigating root causes and anticipating long-term changes, yet their accuracy is limited by inherent uncertainties and errors. While observational constraint theories offer promise in addressing model issues, they often rely on empirical region-specific relationships. Here, we show that future changes in hot extremes and their uneven spread critically depend on historical thermal distributions, with variability playing a key role. We develop a universal analytical approach that combines observations with model outcomes, aiming for more reliable projections. Results reveal that hot event probabilities may grow faster than models imply across much of the global land. In vulnerable regions, increases could exceed model predictions by nearly twofold, even at low global warming levels. These findings lay the groundwork for realistic risk assessments and emphasise the need for strengthened adaptation and mitigation efforts.
Cenozoic evolution of spring persistent rainfall in East Asia and North America driven by paleogeography
Spring persistent rainfall is a unique climate phenomenon that prevails in East Asia today, providing precious water resources to this densely populated region. However, its Cenozoic history and underlying mechanisms remain poorly understood. Here we show that the spring persistent rainfall in East Asia has emerged since the Miocene, whereas it previously flourished in North America during the Eocene, as revealed by climate models integrated with climate proxies. The contrasting evolution of spring persistent rainfall in East Asia and North America is determined by paleogeography and further influenced by CO2-induced warming. The uplift of the Tibetan Plateau and the westward drift of the Rocky Mountains have triggered a mid-latitude Rossby wave train since the Miocene, altering the position and intensity of the subtropical highs and thus rainfall patterns. Our results illuminate the Cenozoic evolution of spring persistent rainfall, with implications for the spring climate under the extreme future warming.
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