Dry–hot compound events exert strong and nonlinear impacts on terrestrial ecosystems, with consequences that extend through land–atmosphere feedbacks across scales. This presentation provides an overview of biophysical vegetation–atmosphere feedbacks during dry–hot compound events, highlighting recent research that shows how processes from ecosystem to circulation scales shape the evolution and predictability of these events.
At the ecosystem level, concurrent drought and heat rapidly impair vegetation functioning. Satellite-based indicators of plant physiology show that functional responses to dry–hot stress occur within days, well before structural degradation becomes detectable. This rapid response marks the loss of ecosystem evaporative regulation and sets the conditions for local land–atmosphere feedbacks to emerge. Stomatal closure triggered by rainfall scarcity and high vapour pressure deficit shifts the partitioning of available energy toward sensible heating, while subsequent changes in vegetation structure modify surface albedo and aerodynamic roughness. Together, these processes alter near-surface temperature and humidity, enhance boundary-layer growth, and affect atmospheric stability and cloud formation. These feedbacks operate on diurnal time scales and lead to the self-intensification of dry–hot compound conditions, particularly in regions where vegetation strongly controls surface energy and water fluxes.
As dry–hot conditions persist, these biophysical feedbacks can propagate beyond the local boundary layer and influence atmospheric processes at larger spatial scales. Vegetation-mediated anomalies in sensible and latent heat fluxes modify boundary-layer depth, entrainment, and thermodynamic structure, affecting mesoscale circulation and the advection of heat and moisture. Reduced evaporation lowers atmospheric humidity and precipitation efficiency downwind, allowing dry–hot anomalies to extend beyond their region of origin. These processes favour the spatial organization, persistence, and propagation of dry–hot extremes, especially in transitional and semi-arid regions where land–atmosphere coupling is strong and soil moisture constraints are pronounced. When widespread, coherent surface anomalies can also influence synoptic circulation by modifying diabatic heating patterns and land–sea thermal contrasts, affecting the positioning and persistence of high-pressure systems. Through these cross-scale interactions, ecosystem stress aggravates dry–hot regimes and reinforces coupling between ecosystem dynamics and atmospheric circulation.
Despite growing evidence that vegetation actively modulates dry–hot extremes, major challenges remain. These include disentangling bidirectional causality between ecosystems and the atmosphere, constraining ecosystem influences on atmospheric circulation, and understanding how ecosystem heterogeneity and biodiversity modulate feedback strength. Addressing these challenges is essential to improve vegetation–atmosphere coupling in current forecasting systems and to enhance the predictability of dry–hot compound extremes under ongoing climate change.
How to cite: Miralles, D. G.: From ecosystem stress to circulation response: biophysical feedbacks during dry–hot compound extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4422, https://doi.org/10.5194/egusphere-egu26-4422, 2026.
Europe has been identified as a Heatwave hotspot in two important ways. Firstly, temperatures warm faster than over most regions globally (Rousi et al. 2022, Vautard et al. 2023), secondly the hottest temperatures increase significantly faster compared to more moderate temperatures (Kornhuber et al. 2024, Patterson 2023). Large scale atmosphere dynamical patterns have been suggested to be associated with these trends, such as an increase in double jet patterns (Rousi et al. 2022), trends in circumglobal Rossby waves (Teng et al. 2022) and local high pressure systems (Vautard et al. 2023).
In this talk we reflect on the fact that climate models underestimate these trends. We show that during persistent circulation regimes, typically present during quasi-stationary Rossby waves (Kornhuber et al. 2023, Luo et al 2021) or double jets (Liu et al., in prep.), models underestimate the heatwave response. We link this to model biases in a three-way feedback process between temperature, high-pressure and soil moisture, which becomes active after a threshold in soil moisture and temperature is crossed (Tian et al. in prep.). We provide evidence that models substantially underestimate this process which is particularly important in driving changes in most extreme heat events over humid to semi-arid regions globally.
How to cite: Kornhuber, K., Tian, Y., and Liu, S.: Atmosphere Dynamical Processes and Soil moisture Feedbacks associated with accelerating heatwave trends , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7687, https://doi.org/10.5194/egusphere-egu26-7687, 2026.
Global warming exacerbates atmospheric dryness, yet the role of soil moisture (SM)-atmosphere feedbacks in regulating its spatiotemporal dynamics remains poorly understood. This study employs Earth system model experiments to quantify how SM dynamics influence local atmospheric dryness and its spatial propagation. Reduced SM drives the self-intensification of extreme atmospheric dryness in three key hotspots: Europe, North America, and South America. SM-atmosphere feedbacks amplify the spread of atmospheric dryness from these hotspots to surrounding areas, yielding extreme dryness events that are more persistent, intense, and spatially extensive. Mechanistically, SM deficit alters surface energy fluxes, deepens the planetary boundary layer, and strengthens mid-tropospheric high-pressure ridges. These processes promote downward advection of dry air and accelerate spatial expansion of atmospheric dryness. These findings confirm that SM-atmosphere feedbacks enhance both the local intensification and spatial propagation of atmospheric dryness, underscoring critical implications for developing ecosystem and societal adaptation strategies to mitigate large-scale extreme dryness under future climate change.
How to cite: Zhou, S. and Liang, J.: Soil moisture-atmosphere feedbacks amplify atmospheric dryness and its spatial propagation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4402, https://doi.org/10.5194/egusphere-egu26-4402, 2026.
Compound drought and heat extremes (CDHE) are expected to intensify and become more frequent as the climate warms, yet their consequences for forest growth and ecosystem stability remain incompletely understood. Here, we combine long-term tree-ring observations with satellite remote sensing to quantify how CDHE influence tree growth and ecosystem resilience across contrasting climate regimes. We find that increasing CDHE frequency leads to widespread growth reductions across most regions, with the exception of cold and humid ecosystems. Growth declines are particularly pronounced in warm–dry, warm–humid, and cold–dry regions. Notably, tree growth in humid ecosystems exhibits increasing sensitivity to CDHE, indicating that these systems may experience disproportionately large growth losses under compound extremes. In parallel, ecosystem resilience declines with rising drought frequency, with the strongest reductions observed in dryland regions. Together, these results suggest that the intensification of compound drought and heat extremes poses growing risks to forest productivity and stability under continued climate warming.
How to cite: Zhang, Y., Jiang, Y., and Qiu, R.: Impact of compound drought and heat extremes on terrestrial ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5665, https://doi.org/10.5194/egusphere-egu26-5665, 2026.
Anthropogenic climate change has intensified soil moisture droughts worldwide, but how this intensification manifests in the spatiotemporal evolution of soil droughts’ vertical structure remains insufficiently understood. We develop a Lagrangian four-dimensional (longitude, latitude, depth, and time) tracking framework to identify contiguous drought events in both space (horizontally and vertically) and time. We reveal a distinct drought type, i.e., deep droughts. These events exhibit bottom-heavy, iceberg-like morphologies, with moisture deficits that are more extensive in deeper layers than in surface soils. Deep droughts account for approximately one-quarter of all events, yet they are largely overlooked by surface-focused soil moisture monitoring. Reanalyses and climate models consistently indicate that the duration and intensity of deep droughts have increased markedly over the past four decades, and that these increases are attributable to anthropogenic climate change. Future projections further indicate that deep droughts will become more persistent and severe globally, with the stronger amplification in deeper soil layers under higher-emission scenarios. Hidden below the surface, deep droughts challenge satellite-based agricultural drought monitoring, potentially leading to an underestimation of drought impacts on ecosystems.
How to cite: Gu, X., Guan, Y., and Wang, L.: Human-induced intensification of subsurface soil moisture drought, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4773, https://doi.org/10.5194/egusphere-egu26-4773, 2026.
The boreal summer circumglobal teleconnection (CGT) provides primary predictability sources for mid-latitude Northern Hemisphere climate anomalies and extreme events. Here, we show that the CGT’s circulation structure has displaced westward by a half-wavelength since the late 1970s, more severely impacting heatwaves and droughts over East Europe, East Asia, and southwestern North America. We present convergent empirical and modelling evidence to reveal the essential role of El Niño-Southern Oscillation (ENSO) in shaping this change. Before the late 1970s, ENSO indirectly promoted CGT by modulating the Indian summer monsoon rainfall (ISMR). Recently, the ENSO–ISMR linkage was weakened, but the westward-displaced ENSO forcing was able to directly trigger a Rossby wave response at the exit of the East Asian westerly jet due to the easterly vertical shear of the zonal basic flow over the tropical western North Pacific, thus shifting the previous CGT’s North Pacific and downstream centers westward along the subtropical jet waveguide. Moreover, the state-of-the-art models with prescribed anthropogenic forcing cannot simulate such changes, indicating their origin from natural variability. The knowledge gained from this work highlights the importance of studying the impacts of changing ENSO to improve seasonal prediction of mid-latitude extreme events.
How to cite: Qiao, S.: Recent changes in ENSO’s impacts on the summertime circumglobal teleconnection and mid-latitude extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10712, https://doi.org/10.5194/egusphere-egu26-10712, 2026.
Greenhouse gases (GHGs) drive global land warming with varying regional impacts, but the role of land-atmosphere interactions in amplifying future warming hotspots remains underexplored. Our study shows that, under uncontrolled GHG emissions, North America and Europe are projected to experience the highest warming by the late 21st century (3.7°±0.7°C and 3.8°±0.5°C, respectively), exceeding the global average of 2.7°±0.4°C in other regions. Approximately one-quarter of this warming in North America and Europe is linked to land-air coupling and associated hot-dry feedback mechanisms, where warming accelerates soil drying, further intensifying surface heating. This feedback could transform nearly 30% of land in these regions into arid or extremely arid zones, significantly impacting ecosystems and agriculture. These results underscore the vulnerability of North America and Europe to amplified climate risks driven by GHG emissions and strengthened land-atmosphere feedbacks.
How to cite: Qiao, L., Zuo, Z., Zhang, R., Mei, W., Chen, D., Chang, M., and Zhang, K.: Extreme Dry-Hot in North America and Europe: The Amplified Role of Warming-Enhanced Land-Air Coupling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20, https://doi.org/10.5194/egusphere-egu26-20, 2026.
In recent decades, unprecedented summer heatwave events have frequently erupted in humid regions. Our analysis of the period 1980–2022 demonstrates that the surging heat extremes are closely linked to both a progressive drying of mean soil moisture and a concurrent intensification of its intra-seasonal variability. While the drying trend contributes to two-week extreme hot days, amplified intra-seasonal variability multiplies these extremes to four weeks by further enhancing shortwave radiation and high-pressure anomalies. Climate projections indicate that a future characterized by drier and more variable soil moisture shifts summer climates towards an intensified ‘mega hot’ stage, where over two-thirds of summer days in humid regions will experience extreme heat by the end of the 21st century under high-emission scenario. Our findings highlight that amplified soil moisture variability—a marker of intensifying soil moisture-air coupling under global warming—is nonlinearly accelerating the occurrence of extreme dry-hot events, pushing humid climates into a new and unprecedented normal.
How to cite: Chang, M., Zuo, Z., Dai, A., Chen, D., Zhang, R., Zhang, K., and Qiao, L.: Amplified soil moisture variability multiplies summer heat extremes in humid regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3303, https://doi.org/10.5194/egusphere-egu26-3303, 2026.
Compound hot-dry and cold-wet extreme events can pose severe threats to human health, social economy, and agricultural production, with their synergistic impacts far exceeding the linear integral of individual events. Land-atmosphere coupling is a key physical process impacting these extremes. However, limitations persist in current studies for quantifying its strength, and the different roles and sensitivities in hot-dry and cold-wet events remain poorly understood. To address these gaps, this work innovatively employs a data-driven Dynamical Systems Method to establish a novel framework for the objective and instantaneous quantification of land-atmosphere coupling globally. Utilizing this framework, this research aims to evaluate the sensitivity of global summer compound hot-dry and cold-wet extremes to land-atmosphere coupling and reveal the spatial patterns of their asymmetric responses. Furthermore, the key local physical processes and large-scale atmospheric circulation modulating mechanisms underlying the observed asymmetries are analyzed through multi-perspective attribution. The results of this project can significantly contribute to the understanding of the relationship between land-atmosphere coupling and compound extremes, providing crucial support for decision-makers to enhance resilience against these complex extremes and to formulate targeted prevention and mitigation strategies.
How to cite: Guo, Y., Fu, Z., Bevacqua, E., Zscheischler, J., and Huang, Y.: A novel index to quantify land-atmosphere coupling: asymmetric response of hot-dry and cold-wet compound extremes., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3647, https://doi.org/10.5194/egusphere-egu26-3647, 2026.
Pronounced spatial disparity in heatwave trends is closely linked to changes in atmospheric circulation and land-atmosphere coupling. By using a complex-network method, we quantify the close relationships between heatwaves and atmospheric teleconnection in the Northern Hemisphere. We find that changes in atmospheric teleconnections (AT) explain about half of the interannual variability in heatwaves and correctly capture nearly 80% of the signs of zonally asymmetric heatwave trends in the mid-latitudes. Moreover, the probability of extremely hot summers has increased sharply by a factor of 4.5 since 2000 over the regions with enhanced AT, but remained almost unchanged over the areas with attenuated AT. By the end of the century, the intensification of heat-dome-like circulation is projected to promote summertime hotspots over western Asia and western North America. Enhanced soil-moisture–temperature coupling may further exacerbate heatwave intensity, particularly over western Asia. Overall, our study provides scientific support for developing impact-based mitigation strategies and more effectively managing future heatwave risks.
References:
Cai, F. et al. Sketching the spatial disparities in heatwave trends by changing atmospheric teleconnections in the Northern Hemisphere. Nat. Commun. 15, 8012 (2024). https://doi.org/10.1038/s41467-024-52254-0
Cai, F. et al. Pronounced spatial disparity of projected heatwave changes linked to heat domes and land-atmosphere coupling. npj Clim. Atmos. Sci. 7, 225 (2024). https://doi.org/10.1038/s41612-024-00779-y
How to cite: Cai, F., Liu, C., Gerten, D., Yang, S., Zhang, T., Li, K., Lin, S., and Kurths, J.: Heatwave trends linked to atmospheric circulation and land–atmosphere coupling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12039, https://doi.org/10.5194/egusphere-egu26-12039, 2026.
The ecological impact of compound climate extremes often exceeds that of individual events; however, the cumulative responses of vegetation to the dynamics of these extremes remains unexplored. In this study, we utilized the Normalized Difference Vegetation Index (NDVI) as a proxy for vegetation to investigate the cumulative responses of global vegetation greenness to the duration, frequency, and magnitude of three types of events: compound hot-dry extremes (CHDE), extreme heat (EHE), and extreme drought (EDE) from 1982 to 2020. Our results reveal a pronounced increasing trend in CHDE across transitional climate zones, where more persistent and stronger events occur in densely vegetated regions. This was characterized by a strong positive correlation between CHDE and vegetation dynamics in these zones, likely driven by intensified land–atmosphere feedbacks, with vegetation response maximized at a 4-month timescale, identified from cross-correlation analysis. Meanwhile, the Amazon and Congo basins emerge as hotspots for heat-related extremes, where EDE and CHDE exhibit greater persistence. At high latitudes of the Northern Hemisphere, vegetation exhibits a robust sensitivity to temperature-driven events, particularly under EHE dominance, where the response shows no temporal lag, indicating an immediate physiological reaction to thermal relief or stress. Furthermore, we observe a global divergence in climate risk and response: while arid regions are experiencing a significant warming trend, humid regions are increasingly threatened by desiccation (drying). Notably, vegetation productivity in humid ecosystems shows a predominant temporal response to EDE, suggesting a higher initial resistance but eventual vulnerability to prolonged water deficits. Finally, we employed machine learning to identify the primary drivers behind these temporal vegetation responses and elucidate how their interactions shape ecosystem sensitivity. These findings underscore the critical role of compound extremes in modulating vegetation dynamics and provide insights for enhancing ecosystem resilience under future climate scenarios.
How to cite: Liu, M., Hagan, D., and Miralles, D. G.: Contrasting Ecosystem Responses to the Dynamics of Compound Climate Extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3530, https://doi.org/10.5194/egusphere-egu26-3530, 2026.
As climate warms, the compound hot–dry events (CHDEs) have become more frequent across most regions of the globe, bringing serious threats to both the human population and the natural environment in affected areas. In the study, a copula-based probability index (PI) is used to explore variations in risk indicators associated with global and regional CHDEs by considering both the annual PI mean and variability. Across most of the world, the risk associated with CHDEs has increased significantly over the past century during 1901–2020, with approximately 89% of land grid cells experiencing increasing trends in high-risk CHDEs. In contrast, the low-risk CHDEs has declined evidently. Detection and attribution analysis indicates that anthropogenic greenhouse gas dominates the high-risk CHDEs and follows similar trends to the observed increase at subregional to continental scales, especially in North America, Europe, Asia, and Oceania. These results emphasize the importance of reducing anthropogenic greenhouse gas emissions to restrict the expansion of high-risk CHDE areas in the globe.
How to cite: Dong, Z., Yang, R., Cao, J., and Wang, L.: Anthropogenic exacerbation of global high-risk compound hot–dry events over the past century, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4156, https://doi.org/10.5194/egusphere-egu26-4156, 2026.
Previous studies have established how regional climate variability regulates local terrestrial gross primary productivity (GPP), yet the hemispheric-scale spatial organization of GPP, coordinated by coherent large-scale atmospheric circulation, has received far less attention. By integrating multi-source observations with numerical simulations, we demonstrate that anthropogenically driven shifts in the Northern Hemisphere westerlies fundamentally reorganize the spatial pattern of terrestrial GPP. Around the year 2000, the curvature of the westerlies reversed, transitioning from a southward to a northward bend over eastern Europe, Northeast Asia, and western North America, while exhibiting opposite changes over central Asia and central North America. The observed spatial pattern of GPP trends closely mirrors the GPP response to variations in westerly curvature. Sensitivity analyses using CESM1 large-ensemble simulations and single-forcing experiments identify greenhouse gas forcing as the dominant driver of these circulation changes, thereby reshaping GPP distributions. Under the RCP8.5 scenario, further intensification of westerly curvature shifts is projected to enhance GPP growth across northern Europe, Northeast Asia, and western North America, while suppressing productivity in southern Europe and central North America. Together, these results reveal a previously underappreciated pathway through which anthropogenic forcing influences terrestrial carbon uptake via large-scale atmospheric circulation, with important implications for projecting future carbon–climate feedback.
How to cite: Yang, X., Dai, A., Messori, G., He, B., Li, Z., Zhong, Z., Yuan, X., Ho, C.-H., Coumou, D., Zhou, B., and Chen, D.: Human-Induced Westerly Jet Shifts Coordinate Terrestrial Productivity at the Hemispheric Scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4284, https://doi.org/10.5194/egusphere-egu26-4284, 2026.
In June 2024, the Eastern Mediterranean experienced an unprecedented heatwave, with regional mean temperature exceeding the climatological average by more than 3 °C, the highest since 1960. However, the relative contributions of anthropogenic forcing and natural variability, as well as the respective roles of atmospheric circulation and soil moisture to this event, have remained unclear. Based on ERA5 reanalysis and HadGEM3-A-N216 attribution simulations, we estimate that anthropogenic forcing accounted for roughly half of the observed temperature anomalies. Human activities not only directly increased surface warming through greenhouse gas emissions but also reduced soil moisture, which in turn amplified temperature anomalies via land-atmosphere coupling. Using the flow analogue and circulation projection methods, we find that another half of warming anomalies attributable to natural variability is dominated by atmospheric circulation change, which features an anomalous anticyclone driven by an upstream wave train and sustained by warm North Atlantic SST anomalies. Additionally, in the component of natural variability, we found a thermodynamic cooling contribution from the wetting soil moisture anomalies, which is likely associated with above-normal preceding precipitation, indicating that wetting soil related land-atmosphere coupling slightly offset the circulation-induced warming in this heatwave. The results highlight contrasting roles of soil moisture in anthropogenic forcing and natural variability in the climate change hotspot, providing new physical insights into future extreme heatwave events.
How to cite: Ma, K. and Yu, H.: Attribution of the record-breaking June 2024 Eastern Mediterranean heatwave: Contrasting roles of soil moisture in anthropogenic forcing and natural variability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4705, https://doi.org/10.5194/egusphere-egu26-4705, 2026.
Summertime compound dry and hot events pose severe threats to human health and agriculture, particularly when events are persistent. Based on the joint evolution of such hazards in space and time, we identified spatiotemporal compound long-duration dry and hot (SLDDH) events across China (1961-2022) using a process-oriented method. These events are consistently associated with anomalous high-pressure systems, which induce sinking air motions, increase solar radiation at the surface, and reduce moisture convergence. The primary driver of precipitation deficits is the dynamical suppression of vertical moisture transport by this subsidence, not atmospheric moisture content changes. For the accompanying high temperatures, anomalous subsidence and the resulting adiabatic warming are the dominant cause across most of China, with surface heating (diabatic processes) playing a minor or even cooling role. However, in northern regions like North China and Xinjiang, extreme heat results from a combination of diabatic heating and adiabatic warming. These findings suggest that the anomalous sinking motion associated with the high pressure systems is partially responsible for the occurrence of these compound extremes over different regions of China.
How to cite: Yang, Y. and Tang, J.: Process-oriented compound long-duration dry and hot events in China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4721, https://doi.org/10.5194/egusphere-egu26-4721, 2026.
Exceptionally strong summertime warming occurred over the Mongolian Plateau between 1986 and 2004, at a rate that was three times the average terrestrial warming in the Northern Hemisphere. The physical processes responsible for this extreme warming remain unclear. Here we show that the synchronous phase shift of the Interdecadal Pacific Oscillation and the Atlantic Multidecadal Oscillation contributed to this extreme Mongolian Plateau warming, which cannot be fully explained by the increasing anthropogenic CO2 alone. Pacemaker model experiments show that the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation excited an atmospheric wave train, resulting in an upper-level anticyclonic circulation over the Mongolian Plateau. This anticyclonic circulation increased surface warming by enhancing downward solar radiation, and the surface warming was further boosted by positive land–atmosphere feedbacks. Our results highlight the important role of internal climate variability in driving rapid regional climate change over the Mongolian Plateau.
How to cite: Cai, Q.: Recent pronounced warming on the Mongolian Plateau boosted by internal climate variability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4759, https://doi.org/10.5194/egusphere-egu26-4759, 2026.
Northeastern China (NEC), known as the granary of China, is significantly affected by compound heat-drought events (CHDEs), which have detrimental impacts on maize production. This study aims to investigate the physical mechanisms underlying the occurrences of CHDEs on maize production in NEC. Our findings indicate that CHDEs are associated with anomalous positive geopotential height at 500 hPa, the presence of anticyclone at 850 hPa and a uniform downward motion in NEC, all of which are adverse to maize production. Using a year-to-year increment method, we reveal that several key factors collectively influence CHDEs and maize production in NEC, including sea ice concentration in the Barents Sea in May, sea surface temperature (SST) in the equatorial East Pacific in February and March, soil water over northwestern Siberia in April, and the North Atlantic Oscillation (NAO) in February. To differentiate the diverse influences of these key factors on CHDEs and maize production, we developed two distinct prediction models (Prediction Model #1 and #2). Both Prediction Model #1 (r=0.90, p<0.01) and #2 (r=0.91, p<0.01) demonstrate high correlation coefficients between predicted and observed values, as validated through leave-one-out cross-validation (Prediction Model #1: r=0.90, p<0.01; Prediction Model #2: r=0.90, p<0.01) and independent hindcasts (Prediction Model #1: r=0.72, p<0.01; Prediction Model #2: r=0.79, p<0.01). This study provides precise predictions of maize production in eastern China, offering significant safeguards for national food security.
How to cite: Zhou, Y., Li, H., Sun, B., Wang, H., Ju, H., Yuan, Y., and Zeng, J.: Predicting Maize Production in Northeastern China: Unraveling the Influence of Summer Compound Heat-Drought Events through Physical Mechanisms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7165, https://doi.org/10.5194/egusphere-egu26-7165, 2026.
Compound heatwave and drought events (CHDEs) in South China (SC) have intensified in early autumn, yet their driving factor remains unclear. Based on reanalysis data and numerical experiments, this study investigates the potential influence of the summer northeastern Arctic Sea ice concentration (NEASIC) on the interannual variation of September CHDEs in the SC. Results demonstrate that positive NEASIC anomalies during summer trigger a quasi-barotropic Rossby wave train, originating over the Greenland Sea, arching across the North Atlantic and the Mediterranean–Caspian region, and extending into East Asia. This wave dynamically drives a northward-shifted and intensified East Asian subtropical jet and anomalous anticyclonic circulation over SC. The resulting subsidence induces moisture flux divergence, suppresses cloud cover, and enhances surface radiative forcing, explaining about 28.4% of the CHDEs variability per interquartile NEASIC increase. This mechanism enhances predictive frameworks for subtropical compound extremes, emphasizing the role of NEASIC in regional climate resilience strategies.
How to cite: Zeng, J., Li, H., Wang, H., Yuan, Y., and Duan, M.: Influences of Summer Northeastern Arctic Sea Ice on September Compound Heatwave and Drought Events in the South China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7338, https://doi.org/10.5194/egusphere-egu26-7338, 2026.
Southwest China experienced a severe drought during winter 2022–spring 2023. This drought mainly struck Yunnan Province and surrounding regions (21°–30°N, 97°–106°E), with precipitation deficit lasting for about 8 months from Oct 2022 to May 2023. The area-mean precipitation and surface soil moisture in the study region during the drought were both the lowest recorded for the same period since 1950. The Standardized Precipitation Evapotranspiration Index (SPEI) also reached its lowest level since 1950 at −2.76. Quantitative analysis shows that precipitation deficit and potential evapotranspiration (PET) increase contributed 71.36%, and 28.64% to the SPEI, respectively. Of the raw contribution of PET, 7.05% can in turn be attributed to the changes in precipitation. Using data from the CMIP6 Detection and Attribution Model Intercomparison Project (DAMIP), we found that anthropogenic forcing increased the likelihood of a PET anomaly such as the one during the drought by about 133 times, with a fraction of attributable risk (FAR) of 0.99 [0.98, 1.00]. For the precipitation anomaly, we obtained a FAR of 0.26 [−1.12, 0.70], suggesting that anthropogenic forcings may have little impact. The extreme drought also increased the risk of fires, with the Fire Weather Index reaching its second-highest value since 1950 and abnormally high burned areas observed by satellites.
How to cite: Ma, T., Chen, W., Cai, Q., Dong, Z., Wang, L., Hu, P., Gao, L., and Garfinkel, C. I.: Attribution analysis of the persistent and extreme drought in southwest China during 2022–2023, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9025, https://doi.org/10.5194/egusphere-egu26-9025, 2026.
Under global climate change, intensified land-atmosphere coupling has amplified the synergy between droughts and heatwaves, triggering a nonlinear escalation of compound hot-dry events (CHDEs) that threatens Earth systems. However, current research often lacks rigorous process-based classification at the atmosphere-soil interface, and understanding of energy partitioning and hydro-thermal feedback mechanisms remains limited, impeding systematic comprehension of these extremes. Using daily ERA5 and GLDAS data from 1965–2024, this study develops a mutually exclusive event identification framework based on four variables—vapor pressure deficit (VPD), air temperature (Tair), soil moisture (SM), and soil temperature (Tsoil)—classifying events into Single-Atmosphere (SA), Single-Soil (SS), and Compound Atmosphere-Soil (CAS) types. We systematically analyze event characteristics, identify high-risk regions, and conduct nonlinear trend analysis using Ensemble Empirical Mode Decomposition (EEMD). A progressive framework integrating event evolution analysis, Copula-based dependence modeling, and Structural Equation Modeling (SEM) is employed to elucidate the underlying physical mechanisms. Key findings are as follows: (1) Spatial patterns reveal mechanistic divergence. SA events display a "tropical zonal clustering" pattern with the highest frequency (8.12 events/decade) but shortest duration (5.09 days) and moderate intensity. SS events show a scattered distribution along land-sea margins with intermediate frequency (3.82 events/decade), longest duration (6.37 days), and lowest intensity. In contrast, CAS events expand extensively across mid-latitudes with the largest frequency increase (251%) and highest intensity (6.60 standardized units), marking a global shift from tropical single-process dominance toward mid-latitude land-atmosphere coupling dominance. (2) Evolution trends exhibit nonlinear acceleration. EEMD outperforms traditional linear regression in trend significance and fitting accuracy, demonstrating superior capability in capturing the nonlinear dynamics of extreme events. SA events intensify persistently in tropical regions but decelerate in later periods; SS events exhibit regional heterogeneity with abrupt shifts in arid zones; CAS events show synchronized global acceleration, with late-period growth rates exceeding early-period rates by 119%–232%. (3) Physical mechanisms differ fundamentally. Analysis reveals that SA events represent rapid boundary-layer responses to radiative forcing (energy-limited) with passive soil moisture depletion. SS events are driven by cumulative hydrological deficits (memory-dominated) with significant recovery lags. CAS events involve synergistic positive feedback: once SM drops below critical thresholds, a self-reinforcing loop (SM↓→LH↓/SH↑→Tair↑→VPD↑→SM↓↓) is triggered, fundamentally altering surface energy partitioning and hydro-thermal coupling regimes. Copula and SEM analyses confirm that SA events exhibit linear synchronous dependence under atmospheric forcing; SS events show lower-tail threshold effects dominated by soil memory; CAS events demonstrate significant cumulative atmospheric driving effects (with soil response lagged by 10–15 days) and enhanced tail dependence under extreme conditions, reflecting strong coupling between atmospheric triggers and soil feedbacks. Furthermore, large-scale climate modes such as ENSO modulate these processes by regulating regional background wet-dry states. This study establishes a comprehensive framework from event identification and characterization to mechanistic interpretation, elucidating the transformation of global hot-dry risks from "tropical single-process dominance" to "mid-latitude land-atmosphere coupling dominance," providing a robust scientific basis for monitoring, early warning, and risk management of compound extreme events.
How to cite: Yang, R., Zhao, L., and Li, X.: Distinct Energy and Hydro-Thermal Coupling Regimes at the Land-Atmosphere Interface Shape Global Compound Hot-Dry Extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12468, https://doi.org/10.5194/egusphere-egu26-12468, 2026.
Abrupt transitions in the Earth system can arise from bifurcation-induced tipping, rapid forcing rates, or noise-driven excursions, making early warning inherently probabilistic. Using the Atlantic Meridional Overturning Circulation (AMOC) as a case study, we run large ensemble simulations of a calibrated AMOC model under time-varying freshwater forcing and stochastic perturbations. Even under identical forcing scenarios, only a subset of ensemble members undergoes a tipping transition, highlighting an intrinsically stochastic regime. In this setting, conventional early-warning signals based on critical slowing down (CSD, e.g., increasing lag-1 autocorrelation and variance) show limited prediction ability and are easily confounded by non-stationary forcing and noise. We develop a deep-learning (DL) indicator trained on labeled ensemble trajectories to distinguish transitioning from non-transitioning dynamics using sliding windows of time series, thereby capturing high-order temporal statistics beyond traditional early-warning indicators. In application, the model outputs trajectory-specific probabilities of tipping in real time, enabling probabilistic warnings ahead of tipping. Across a range of freshwater forcing pathways and noise amplitudes, the DL indicator provides earlier and more robust probabilistic forecasts than CSD indicators and supports a probabilistic interpretation of safe operating boundaries. The framework is transferable to other Earth system components where tipping risk must be assessed under uncertainty from stochastics and forcing.
How to cite: Zhang, W., Huang, Y., Bathiany, S., Shin, Y., Zhou, S., and Boers, N.: Probabilistic prediction of tipping points in Earth system with deep learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6719, https://doi.org/10.5194/egusphere-egu26-6719, 2026.
Since the 1980s, both incoming shortwave radiation (SW) and atmospheric vapor pressure deficit (VPD) have increased significantly across Europe and are projected to continue rising in the coming decades, potentially altering forest photosynthesis, carbon uptake, and carbon storage. However, the joint impacts of SW and VPD on forest carbon sequestration remain poorly understood. Here, using half-hourly flux tower observations combined with remotely sensed vegetation indices, we show that SW and VPD are the dominant energy- and water-related drivers of forest net ecosystem exchange (NEE; negative values indicate net carbon uptake) at the half-hourly scale in Europe. We identify a distinct threshold in the VPD–NEE relationship at approximately 7 hPa, beyond which influence of VPD shifts to positive values and strengthens sharply. The influence of VPD on NEE is strongly mediated by SW, increasing gradually under low SW conditions but intensifying sharply under high SW conditions. This pattern arises because strong solar radiation amplifies VPD-induced stomatal closure, thereby suppressing photosynthesis and altering ecosystem carbon exchange. Together, these findings suggest that future increases in atmospheric dryness—potentially reinforced by continued brightening—may substantially constrain forest productivity and carbon sequestration. Our results underscore the importance of accounting for SW–VPD interactions in climate impact assessments and forest management strategies.
How to cite: Zhong, Z.: Elevated shortwave radiation enhances the limitation of atmospheric dryness on forest carbon sequestration , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12397, https://doi.org/10.5194/egusphere-egu26-12397, 2026.
The upper reaches of the Yangtze River observed record-breaking droughts, heatwaves, and forest fires in rapid sequence during the 2022 summer, challenging the established mechanistic understanding. We here explained the compound event through a trans-seasonal vegetation-land-atmosphere interacting perspective. The wetter spring and sunnier summer pattern resulted in record high loads of vegetation and enhanced transpiration. This led to progressive depletion of soil moisture to a critical threshold that shifted the originally weak response of air temperature into hypersensitive mode. The resulting rapid rise of air temperature amplified atmospheric evaporative demand to an unprecedentedly high level, which in turn exacerbated the drying-out of soil and vegetation. These favorable weather and fuel factors combined to cause unseasonal forest fires of unprecedented burning intensity. Our results remind of preparedness against drought-heat-fire compounding hazards even in humid regions under opportune configurations between ecological and meteorological conditions.
How to cite: An, N. and Chen, Y.: Trans-Seasonal Vegetation-Land-Atmosphere Interactions Explained Record-Breaking Cascading Extremes in the Upper Reaches of the Yangtze River, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2917, https://doi.org/10.5194/egusphere-egu26-2917, 2026.
Compound drought and hot extremes (CDHEs) exert disproportionately larger impacts on natural systems and agriculture than individual climate extremes. Existing research indicates that CDHEs are increasing in frequency and intensity, posing significant risks of severe agricultural drought and soil moisture exhaustion. However, the variations of CDHEs have been primarily studied at single timescales, leaving their multi-timescale characteristics and the resulting impacts on agricultural drought development poorly understood. We investigates the spatiotemporal evolution of CDHEs across different timescales using ERA5 reanalysis data and CMIP6 simulations. We then quantify the impacts of CDHEs on soil moisture, demonstrating that CDHEs significantly amplify the probability and severity of deficits in both surface and root-zone layers compared to independent droughts. Furthermore, the variability of the sensitivity of soil moisture deficits to CDHEs over recent decades has been explored. These findings provide a comprehensive perspective on how compound extremes drive agricultural water stress across timescales, offering critical scientific support for developing robust early-warning systems and water management strategies in a warming climate.
How to cite: Yitong, Z. and Zengchao, H.: Changes in compound droughts-hot extremes across different timescales and their impact on soil moisture deficits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3941, https://doi.org/10.5194/egusphere-egu26-3941, 2026.
Accurate seasonal drought prediction is crucial for mitigating socio-economic and ecological losses, yet dynamical models are often evaluated on drought indices rather than integrated events, and their skill variation linked to drought mechanisms remains unclear. This study assesses SEAS51, CFSv2, and CPS3 for five extreme droughts (2018-2022) over China using a 3D event-oriented framework based on the SPAI and DBSCAN clustering. The deterministic and probabilistic prediction skills are assessed using the threat score, and the models’ ability to capture critical precursors and circulation patterns is examined. Our results indicate that deterministic drought predictions generally skillful within lead times of 45 days. Probabilistic predictions extend the skillful lead time, in some cases beyond 120 days. Model performance varies substantially across events, closely linked to their capacity to simulate key drought-driving processes, such as the weakened Walker Circulation during the 2018 South China drought and Rossby wave dynamics associated with the 2022 Yangtze River Basin drought. Moreover, we identify the limitation of predicting persistent and large-scale precipitation deficits in dynamical models, which leads to an optimal probability threshold of 25% for ensemble-based drought prediction. These findings highlight the operational value of probabilistic ensemble predictions for drought early warning and provide a mechanistic basis for understanding model skill differences, supporting the development of drought prediction systems.
How to cite: Yin, H.: Assessment of Prediction Skills for Seasonal Drought Events Using Dynamical Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2061, https://doi.org/10.5194/egusphere-egu26-2061, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 5
EGU26-2053 | ECS | Posters virtual | VPS2
Global-scale compound Droughts and heatwaves: inland/coastal type grouping, diversity of temperature extremes, and dynamically-based Interpretable reconstructionMon, 04 May, 14:42–14:45 (CEST) vPoster spot 5
How to cite: Liu, Z.: Global-scale compound Droughts and heatwaves: inland/coastal type grouping, diversity of temperature extremes, and dynamically-based Interpretable reconstruction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2053, https://doi.org/10.5194/egusphere-egu26-2053, 2026.
EGU26-2384 | ECS | Posters virtual | VPS2
Committed and Irreversible Humid Heat Stress Risk in China Despite Carbon Dioxide RemovalMon, 04 May, 14:48–14:51 (CEST) vPoster spot 5
Carbon dioxide removal (CDR) is critical to net-zero pathways achieving the Paris Agreement 1.5°C target, yet its effectiveness in reducing humid heat stress risks remain uncertain. Here we examine the hysteresis and reversibility of humid heat stress in China under CDR scenarios. Humid heat responds asymmetrically during warming and CO2 removal especially in eastern and southern China, producing a hysteretic and partially reversible trajectory. This results from unequal adjustments of temperature and relative humidity, which constrain heat-stress recovery even as global temperatures decline. Moist static energy analysis indicates suppressed vertical energy export over eastern China and enhanced transport of warm moisture from tropical oceans, sustaining humid heat during CO2 removal. Consequently, severe humid heat stress persists, with over 6.4 billion people affected, more than 66% of which is due to hysteresis. These findings highlight enduring heat-related risks and the urgent need for adaptation alongside mitigation.
How to cite: Ma, Q.: Committed and Irreversible Humid Heat Stress Risk in China Despite Carbon Dioxide Removal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2384, https://doi.org/10.5194/egusphere-egu26-2384, 2026.
EGU26-557 | ECS | Posters virtual | VPS2
Temperature-driven shift intensifies 21st-century Amazon droughtsMon, 04 May, 15:03–15:06 (CEST) vPoster spot 5
The Amazon Basin (AB) is experiencing an intensification of hydroclimatic extremes, with droughts becoming more frequent, widespread, longer, and severe in the 21st-century. While precipitation deficits have historically been the primary driver of these events, the role of rising air temperatures and the consequent increase of atmospheric evaporative demand (AED) remains poorly quantified. Understanding the relative contributions of these factors is crucial for assessing AB resilience and potential tipping points under ongoing global warming. Here, we analyzed drought evolution across the AB over 45 years (1980–2024) using the Standardized Precipitation-Evapotranspiration Index (SPEI) derived from ERA5-Land reanalysis data. To isolate the contribution of atmospheric evaporative demand (CAED) to drought severity, we compared the standard SPEI with a modified SPEI version based on constant climatological AED.
Furthermore, we applied a rarity index to systematically rank drought events by intensity and spatial extent, enabling a standardized comparison of the exceptional 2023/24 event with historical benchmarks. Our analysis reveals that the 2023/24 drought (AD-23/24) was the most extreme event on record, affecting over 88% of the basin’s area and having a magnitude four times that of the average of the previous top-5 droughts. Notably, the recurrence of high-ranking drought years since 2020 underscores a persistence of extreme conditions in the 2020s. Crucially, the CAED analysis uncovers a distinct temporal regime shift occurring after 2005. While earlier droughts were primarily precipitation-driven, the post-2005 era is characterized by a predominantly evapotranspiration-driven regime, in which climate change-induced warming significantly amplifies drought intensity through increased AED. This intensification is further linked to sea surface temperature anomalies in the Tropical Indian, Tropical Pacific, and North Atlantic oceans. These findings demonstrate that the AB has entered a new hydroclimatic phase in which temperature-driven AED is overtaking precipitation deficits as the primary driver of exceptional drought events. This shift suggests that warming is likely exacerbating drought severity, posing unprecedented challenges for ecosystem stability and water security in the region.
How to cite: Albuquerque, R., M. dos Santos, D., F. V. V. Miranda, V., F. Peres, L., M. Trigo, R., M. B. Nunes, A., L. R. Liberato, M., M. Gouveia, C., and Libonati, R.: Temperature-driven shift intensifies 21st-century Amazon droughts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-557, https://doi.org/10.5194/egusphere-egu26-557, 2026.
