Arid and semi-arid regions constitute 42% of global land area and house nearly half the world's population. Recent decades have witnessed their expansion, with semi-arid areas accounting for over half of this growth. Their inherently low soil fertility makes them highly vulnerable to warming and human activity, driving widespread desertification. Analyzing the Global Desertification Vulnerability Index (GDVI) reveals divergent regional trends. While GDVI is rising in areas like western North America, it shows a significant and sustained decline in China's Yellow River Basin since 1999. This contrast highlights the positive impact of active ecological restoration. Policies like China's "Grain for Green" program, by building ecological barriers, have effectively reduced desertification risk in the basin. This case demonstrates that targeted ecological restoration is a viable strategy to combat desertification, offering a model for addressing water scarcity and ecosystem fragility in semi-arid regions globally.

How to cite: Guan, X., Huang, J., and Qiu, P.: Ecological Barriers Against Desertification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2186, https://doi.org/10.5194/egusphere-egu26-2186, 2026.

Precipitation in the Yellow River Basin (YRB) shows contrasting decadal changes from 1961 to 2022, with the northern part becoming drier and the southern part becoming wetter. Based on ensemble empirical mode decomposition (EEMD) method, this study finds that the Pacific Decadal Oscillation (PDO) is a key moderator of the decadal variability of precipitation across the YRB. Specifically, precipitation decreases significantly over most parts of the YRB during positive PDO phase, while it increases during negative phase. Further studies revealed that this distribution is closely related to water vapor transport and atmospheric circulation. During the positive PDO phase, the core of the westerly jet (20°N-60°N, 80°E-160°E) is located over the northwest of the YRB, generating a cyclonic circulation at its southeastern periphery. Meanwhile, the water vapor is dominated by divergence, resulting in insufficient water vapor conditions. This configuration inhibits upward movement and suppresses precipitation in the basin. In contrast, during the negative phase of the PDO, the westerly jet receded to the west and weakened, resulting in increased transport of warm moist air from the ocean to the YRB. Multi-model simulation results from the Coupled Model Intercomparison Project Phase 6 (CMIP6) show that the decadal trends of precipitation in the YRB show opposite patterns during the positive and negative phases of the PDO. The YRB precipitation phase reverses under the SSP585 scenario with respect to the historical period, the SSP126, and SSP245 scenarios, which has a profound impact on the future socio-economic development of the YRB. This study provides new insights into the physical drivers of decadal precipitation variability over the YRB, offering a valuable reference for improving future climate projections and regional water resource management.

How to cite: Ma, T. and Guan, X.: Influence of pacific decadal oscillation on decadal precipitation variation over the Yellow River Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1933, https://doi.org/10.5194/egusphere-egu26-1933, 2026.

Decadal-scale droughts, known as megadroughts, occurred repeatedly in the North and South American Southwest (NASW and SASW) over the past millennium, including simultaneous events. Similarly, these regions experienced prolonged wet periods, megapluvials, including well-documented episodes over the 20th century. Using a paleoclimate data assimilation product, we identify 18 megapluvials in each region (12 overlapping), 13 NASW and 15 SASW megadroughts (9 overlapping). Both phenomena show similar duration and severity, with 122 years of simultaneous megapluvial conditions and 113 years of simultaneous megadroughts. We find that megapluvials in both regions are driven by a reduction in drying La Niña-like states and not solely by an increase in wetting El Niño-like states; while both changes are statistically significant, the decrease in La Niña-like conditions is greater than the increase in El Niño-like conditions. Megadroughts exhibit an analogous asymmetric mechanism: they are characterized by increased La Niña-like states accompanied by a stronger reduction in wetting El Niño-like states. We also find volcanic forcing influences these events through the El Niño-Southern Oscillation (ENSO): large eruptions reduce the frequency of La Niña-like states, causing overall wetting. This mechanism is most clearly seen in the SASW where ENSO teleconnections are stronger in the paleoclimate reconstruction. These findings demonstrate that megapluvials exhibit interhemispheric synchronization that is similar to megadroughts and are similarly influenced by Pacific variability on decadal timescales. Our results highlight the need for better understanding and representation of ENSO's response to external forcing, including anthropogenic climate change, to improve projections of decadal hydroclimate variability in the NASW and SASW.

How to cite: Berger, E., Steiger, N. J., Smerdon, J. E., and Cook, B. I.: Simultaneous Megapluvials in Southwestern North and South America During the Last Millennium, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2444, https://doi.org/10.5194/egusphere-egu26-2444, 2026.

The persistent increase in heatwaves has caused substantial economic and ecological damage. However, the contribution of decadal oceanic variability to the recent surge in heatwaves remains unclear. Here, using observations and simulations, we demonstrate that oceanic modulation drives decadal heatwave swings and trends. We quantify that the decadal component of heatwave cumulative intensity (HWCI) accounts for 57% of the observed increase in HWCI across the Northern Hemisphere from 2013–2021, with 44% attributed to increases in the smoothed component (HWCI_S) and 13% to enhancements in the anomaly component (HWCI_A). Notably, decadal oceanic variability contributed to 63% of the HWCI increase in the Northern Hemisphere during 2013–2021 and to 26% over 1985–2021. Regionally, oceanic modulation amplified HWCI by 58% in Europe, and contributed more than 20% in North Africa, southern North America, eastern China, and northern Central Asia during 2013–2021. The positive-to-negative phase transitions of the Atlantic Multidecadal Oscillation (AMO) and Interdecadal Pacific Oscillation (IPO) were identified as key drivers of this recent intensification. Model simulations incorporating AMO and IPO forcings closely align with observed HWCI decadal oscillations since 1940, further supporting these findings. Our results highlight that oceanic modulation can significantly amplify or dampen human-induced long-term heatwave trends, suggesting a potential slowdown in heatwave intensification in the coming decades as oceanic variability transitions to a new phase.

How to cite: Lei, N., Guan, X., and Xie, Y.: Decadal Oceanic Variability Amplified Recent Heatwave in the Northern Hemisphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3501, https://doi.org/10.5194/egusphere-egu26-3501, 2026.

Extreme wildfires have devastating impacts on multiple fronts, and associated carbon greatly heat earth climate. The important meteorological conditions for the wildfires include high temperatures and drought. The climate state in the semi-arid regions further provide a favorable background condition. The southern part of the West Siberia is a crucial semi-arid area, yet the research on the climate driving mechanisms of wildfires in this region is still limited. West Siberia faces severe wildfire risks and carbon emissions in the future. Therefore, how to effectively predict wildfires in this region also become a critical problem.

In this study, we find that the preceding-winter “warm Arctic-cold Eurasia” (WACE) pattern significantly enlarges the spring burned area in West Siberia. The winter WACE and accompanying snow reduction result in a dry and exposed-vegetation West Siberia in spring. The January stratospheric variability over mid-high latitude Eurasia also can modulate the tropospheric atmospheric circulation anomalies through downward propagation of signals, causing the reduced winter snow and increasing the spring wildfire risk. Apart from the influence of the Arctic, the tropical sea-air interaction is also of great significance. The March Maritime Continent SST anomaly can cause an earlier retreat of the spring snowline through a Rossby wave, and leads to vegetation exposure and surface drying, which favors wildfire occurrence.

These three factors provide the prediction information for the spring wildfire burned area in West Siberia. A multiple linear regression model is constructed to successfully predict the spring burned area in West Siberia (R=0.90), evaluating by “leave-one-out” cross validation. The same predictors also well predict the corresponding fire carbon emissions (R=0.73). Findings of this study provide a possibility for guarding human against extreme wildfires and foreknowing sharp rises in carbon emissions.

How to cite: Zhang, Y. and Yin, Z.: Impacts of Arctic and tropical climate variability on spring wildfires in West Siberia and the predictive role, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3743, https://doi.org/10.5194/egusphere-egu26-3743, 2026.

Despite weakening mid-latitude winds under global warming suggesting a decline, East Asian dust activity has unexpectedly rebounded since 2000. We demonstrate this resurgence is driven by the synergy between the Atlantic Multidecadal Oscillation (AMO) positive phase and La Niña, explaining 78% of dust variance. Integrating observations and simulations, we reveal that the dominant driver of recent dust enhancement has shifted from dynamical factors (wind) to hydrothermal anomalies. The cross-basin synergy of the AMO positive phase and La Niña creates a hydrothermal background in the East Asian interior characterized by a "cold winter, warm spring" pattern accompanied by persistent drought. This pattern intensifies the soil freeze-thaw cycle and surface drying, significantly enhancing surface erodibility, thereby becoming the dominant factor for extreme dust outbreaks. Through a closed-loop evidence chain (phenomenon identification, mechanism attribution, and model verification), we clarify how cross-basin climate synergy affects regional dust. These findings provide a robust foundation for seasonal-to-decadal prediction of East Asian dust activity.

How to cite: Zhao, R., Feng, X., Li, C., Yang, Y., and Stringer, L.: Positive AMO–La Niña synergy enhances recent East Asian dust activity via hydrothermal anomalies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3783, https://doi.org/10.5194/egusphere-egu26-3783, 2026.

The Yellow River Basin (YRB) serves as a vital ecological barrier and a primary grain-producing region in China. Characterized predominantly by an arid and semi-arid climate, the basin’s water resources are highly sensitive to human activities. In recent years, rapid urbanization has significantly altered the regional water resource distribution, making it essential to clarify the resulting changes in the hydrological cycle for informed policy-making. This study analyzes the spatial-temporal characteristics of groundwater changes throughout the urbanization process across the basin. The results show that urbanization levels in the YRB exhibit significant spatial heterogeneity, with a marked intensification of urban expansion and population growth in the lower reaches. While groundwater levels across the entire basin show a declining trend, with the most severe depletion occurring downstream, a comparative analysis of different urban transition types reveals nuanced impacts. Specifically, the decline in groundwater is least pronounced in areas of urban contraction, while newly urbanized areas show a smaller reduction in groundwater compared to long-standing, stable urban zones. These findings suggest that while urbanization inherently exerts pressure on groundwater in this water-scarce region, the relatively moderated decline in newly developed areas reflects the effectiveness of recent groundwater protection policies integrated into the urbanization process.

How to cite: Shen, X. and Guan, X.: Analysis of the Impact of Urbanization on Groundwater in the Arid and Semi-Arid Yellow River Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3904, https://doi.org/10.5194/egusphere-egu26-3904, 2026.

In the 21st century, two record-breaking years of extreme drought coverage swept across the globe. These resulted in billions of agriculture losses and led to hunger and poverty in those developing countries. Recent decadal increasing extreme droughts are closely associated with the decadal modulated oscillation (DMO) signal, majorly in charge by the Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). Meanwhile, the DMO significantly influences global wet-dry variations through phase changes, leading to an increase in the probability of extreme droughts in the positive phase. Composite analysis shows that high probability of extreme drought corresponds to positive anomalies of 500 hPa geopotential height and low-level anticyclonic conditions. Under future climate scenarios, DMO is expected to intensify in most regions, leading to an increased risk of extreme droughts, especially in Australia. As anthropogenic warming intensifies, the coming spatial coverage of extreme droughts will continue creating new records.

How to cite: Xu, Y., Guan, X., and Huang, J.: Enhanced global extreme droughts driven by the Indian Ocean and Pacific Ocean on decadal timescales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5232, https://doi.org/10.5194/egusphere-egu26-5232, 2026.

The anomalous hydrothermal conditions during growing seasons, i.e. less precipitation and high temperature, could induce an unstable water resource supply and pose great threats to regional agro-pastoral production, particularly in water-scarce drylands. Owing to the biases in the simulations of global climate models, quantifying the anthropogenic influences on such high-impact hot–dry extremes and future risks in the arid and semi-arid areas remains challenging. Based on CN05.1 observations and statistically downscaled simulations from the Coupled Model Intercomparison Project Phase 6, we conducted a comprehensive attribution and projection on the 2022- and 2023-like growing-season hot–dry extremes in Northwest China (NWC). Observations reveal that NWC experienced a fourfold increase in the occurrence of anomalously hot–dry growing seasons during 1991–2023 relative to that in 1961–1990. Attribution indicates that anthropogenic forcings have doubled/tripled the likelihood of 2022/2023-like hot–dry growing seasons in NWC largely due to human-induced warming. NWC is expected to experience increasingly hot growing seasons but with slight precipitation changes in the 21st century under the intermediate greenhouse gas emission (SSP2-4.5) scenario. The likelihood of 2022/2023-like hot–dry growing seasons in NWC will be more than 1–5 times that in the present-day (1991–2020), which is still dominated by rising temperature. To alleviate the stress of hot–dry growing seasons on agro-pastoral systems, we underscore the urgency of developing effective adaptation and mitigation strategies for water resource management in water-limited drylands.

How to cite: Yu, X. and Dong, S.: Escalating risks of anomalously hot–dry growing seasons in arid Northwest China under human influence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8387, https://doi.org/10.5194/egusphere-egu26-8387, 2026.

Precipitation variability across North America (NA) substantially impacts regional water security, agricultural productivity, ecosystem stability, and the frequency of extreme climatic events. Variations in annual precipitation play a critical role in drought occurrence and dryland expansion. The southwestern NA, a typical semi-arid region, has experienced rising agricultural and industrial water demands in recent decades, increasing its vulnerability to droughts. Since 1980, this region has grown drier, intensifying risks of moisture deficits and wildfires. Previous studies have identified both anthropogenic forcing and internal variability as key factors driving NA precipitation changes. External forcing from greenhouse gas and aerosol emissions has influenced regional precipitation patterns, while internal variability associated with large-scale teleconnection patterns plays a crucial role in modulating these changes, particularly on interannual to decadal timescales. However, most studies have focused on either external forcing or internal variability in specific NA regions, neglecting their combined effects across the entire continent.

Here, we combine long-term observational data and CMIP6 simulations to find the distinct roles of anthropogenic forcing and low-frequency internal variability. Our results identify a long-term wetting trend primarily driven by greenhouse gas forcing, though state-of-the-art climate models tend to underestimate the influence of external forcing on NA precipitation. Decadal precipitation oscillations are modulated by internal variability, especially the Interdecadal Pacific Oscillation (IPO), whose sea surface temperature anomalies trigger large-scale Rossby waves. The wave train originating from the Pacific propagates downstream, influencing atmospheric circulation and moisture transport, ultimately shaping the tripolar precipitation pattern observed in NA. Climate model simulations confirm that the impact of the Atlantic Multidecadal Oscillation (AMO) on NA precipitation is significantly weaker than that of the IPO. This tripolar precipitation pattern dominates NA precipitation variability at decadal scales, surpassing anthropogenic influences. From 2021 to 2050, the tripolar pattern is projected to persist, contingent on IPO phase. By 2100, constrained projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest a further intensification of precipitation increases. This study shows how NA rainfall responds differently to human influence and natural oscillations over decades, with implications for improving our ability to predict and attribute regional climate changes.

How to cite: Fan, X. and Huang, J.: External and internal controls on decadal precipitation variability over North America, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8996, https://doi.org/10.5194/egusphere-egu26-8996, 2026.

The inland advection of the well-formed marine stratocumulus cloud deck in the tropical Southeast Pacific produces semi-permanent fog banks in the hyperarid coastal mountains of the Atacama Desert. These fog banks represent the sole water input to highly adapted xeric ecosystems and can serve as a potentially tappable water resource for human consumption. Whether to sustain ecosystems or domestic water consumption, our understanding of long-term fog-harvesting variability is very limited, as observations are short-term and intermittent. This observational gap makes it difficult to understand what is driving fog-harvesting variability at interannual (relation with ENSO), seasonal, and sub-diurnal scales. Therefore, hindering our ability to assess the feasibility of exploiting this natural resource at the long term. In this work, we propose using the Advective fog Model for Arid and semi-arid Regions Under climate change (AMARU; Lobos-Roco et al., 2025) to study the long-term variability of harvesting potential resulting from the interaction of stratocumulus clouds with coastal topography. The model inputs are ERA5 reanalysis time series between 1950 to 2023, which have been downscaled to meteorological observations using artificial neural networks. Model outputs are compared with historical fog water harvesting observations from 1997 to 2023 in Alto Patache fog oases (20.8°S; -70.1°W), showing R²~0.8 and a regression slope~1. Our modelling results show that the coastal Atacama Desert is a promising site for fog harvesting, with water volumes ranging from 2.9 L m^-2 per day to 9.5 L m^-2 per day over seven decades, and a subtle trend toward an increase of 3.46 L m^-2 pear year. At the interannual scale, fog harvesting is modulated by the (in)harmonization between the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) phases. For example, during warm PDO, ENSO correlates positively with fog harvesting, while during cool PDO, ENSO correlates negatively with fog harvesting. The modulation of ENSO-PDO in fog harvesting has decreased over the decades, probably due to climate change. From 1950 to 2023, fog-harvesting seasonality has been narrowing, with the fog-harvesting season starting later and ending earlier, but with higher water volumes during the fog season. Finally, at the diurnal scale, our model results demonstrate that fog harvesting is more controlled by air-liquid water content (cloud density) at night and by wind speed (cloud density transport) in the afternoon. Our study contributes to disentangle fog-harvesting variability across multiple temporal scales, thereby enhancing our capacity to assess ongoing and future multipurpose and large-scale fog-harvesting projects in coastal deserts.

How to cite: Lobos-Roco, F., Keim-Vera, K., and Boada, J.: Modeling the multi-scale temporal variability of fog harvesting potential in the coastal Atacama region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10245, https://doi.org/10.5194/egusphere-egu26-10245, 2026.

A continuing warming trend has been revealed at most regions around the world during the last 60 years. In order to assess the impact of the climate change on crop production, it is necessary to study the impact of observed climate change on crop development. In this study, we compared the impacts of climate warming on growth and yields of spring wheat at different elevation in northwest arid region by using observation data obtained in Zhangye (representative low-elevation) and Minle (representative high-elevation) agricultural meteorological station from 1981 to 2020. We analyzed temperature and precipitation data to determine climate trends, also analyzed surface observation data and potential evapotranspiration(PET) from agricultural meteorological stations to determine phenology and yields of spring wheat. The relationshipsbetween spring wheat growth, yields and the temperature, PET were also examined by SPSS24.0. The results showed that the climate change patterns and their impacts in these two stations were diverse during the study period. Warmer climate trends were observed both in low-elevation and high-elevation region, but the magnitude of warming at high-elevation was greater than that of low-elevation. The response of phenology of spring wheat to climate warming took the form that the sowing date had advanced in high-elevation and the growth duration had shortened in these two stations. The growth duration would shorten by 7.2d at high-elevation and by 4.0d at low-elevation for each 1^oC rising in daily mean temperature during spring wheat growth, and the sowing date would advance by 0.04d for each 100m rising in elevation. However, the response of the yields of spring wheat were different in these two stations. The yields showed a trend of increasing first and then decreasing, at high-elevation, but the yields had decreased at low-elevation. Such response was related to the critical temperature—30.1 ^oC at high elevation, and which was related to PET at low elevation. In case the maximum temperature during the spring wheat growth was less than 30.1 ^oC, a rising in temperature would increase yields. When the maximum temperature was beyond 30.1 ^oC, then a rising in temperature would decrease yields at high elevation, the response of PET is similar in low elevation. The continuous increase in temperature in future may result in the maximum temperature of spring wheat growth period to exceed the critical temperature, thus leading to declining of spring wheat yields. So we expect that with the climate further warming, it will continuately impact spring wheat growth and yields in arid region, especially the negative influence at low-elevation region.

How to cite: Wang, X., Zhang, Q., Zhao, H., and Cai, D.: Elevation-dependent wheat yields variations under climate changes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21717, https://doi.org/10.5194/egusphere-egu26-21717, 2026.

Tianshan Mountains are the headwater regions for the central Asia rivers, providing water resources for ecological protection and economic development in semiarid regions. Due to scarce observations, the hydroclimatic characteristics of the Tianshan Mountains Precipitation (TMP) measured over highland (>1,500m) regions remain to be revealed. Here, we show the TMP belongs to a monsoon-like climate regime, with a distinct annual range and a high ratio of summer-to-yearly rainfall, and exhibits six abrupt changes, dividing the annual cycle into six precipitation sub-seasons. Over the past 60 years, the yearly TMP has significantly increased by 17.3%, with a dramatic increase in winter (135.7%). The TMP displays a significant 40-day climatological intra-seasonal oscillation (CISO) in summer. The TMP CISO’s wet phase results from the confrontation of the eastward propagating mid-tropospheric Balkhash Lake Low and the southward migrating Mongolian High. The sudden changes in the two climatological circulation systems trigger TMP’s changes, shaping the 40-day CISO. Emerging scientific issues are also discussed.

How to cite: Jin, C.: How much we know about precipitation climatology over Tianshan Mountains––the Central Asian water tower, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11720, https://doi.org/10.5194/egusphere-egu26-11720, 2026.