Ren Wang

Evapotranspiration (ET) and precipitation (P) jointly shape terrestrial water availability, defined here as P − ET and regulate land‐atmosphere water and energy exchanges. However, their long‐term coupled changes remain insufficiently understood. We examined global land patterns of trends in ET and P − ET during the period of 1982–2020 using GLEAM v3.8a and ERA5‐Land ET together with MSWEP v2.8 precipitation. For the annually selected driest and wettest months, random‐forest models were trained on 1982–2010 samples and evaluated using a temporal holdout for 2011–2020, separately for four combinations of ET and P − ET trend directions. Both ET products showed widespread ET increases, whereas P − ET trends were spatially heterogeneous and frequently differed in sign from ET trends. Joint consideration of mean P − ET, (P − ET)/ET and their long‐term trends showed that some regions with positive mean water availability experienced a diminishing precipitation surplus relative to actual ET. Moreover, both RF and SHapley Additive exPlanations (SHAP) analyses showed that predictive contributions varied among precipitation conditions and trend scenarios. Temperature‐related information was prominent for ET in selected scenarios; antecedent vegetation state was more informative under the driest‐month condition where ET and P − ET trends differed in sign and contemporaneous precipitation dominated wettest‐month P − ET predictions. These results identify regional variability in water availability and show that the associated predictive relationships are condition‐ and scenario‐dependent rather than governed by a single universal factor.

Western North Pacific (WNP) tropical cyclone (TC) activity has experienced substantial structural reorganization during 1980–2024. Using CMA best-track data, HadISST, ERA5 reanalysis, and the Niño3.4 index, this study examines long-term changes in TC frequency, intensity composition, track-density redistribution, lifecycle-stage displacement, and associated SST–circulation linkages. Results show that annual TC frequency decreased significantly, whereas the proportion of super typhoons increased. Meanwhile, TC track density decreased over the tropical western Pacific but increased over parts of the subtropical WNP, leading to a significant poleward shift of the annual track centroid. Lifecycle decomposition further reveals strong intensity dependence. Severe tropical storms exhibit the most robust poleward signal, with significant northward shifts in lifetime maximum intensity and dissipation latitude, as well as enhanced genesis-to-dissipation displacement. Environmental analyses indicate that the poleward redistribution is associated with a La Niña-like Pacific SST pattern, western Pacific warming, northwestward displacement of the WNP subtropical high, and steering-flow anomalies favorable for poleward TC motion. These findings suggest that WNP TC risk and regional hazard exposure are being reshaped not only by changes in frequency and intensity composition, but also by spatial redistribution and lifecycle evolution.

Western North Pacific (WNP) tropical cyclone (TC) activity has experienced substantial structural reorganization during 1980–2024. Using CMA best-track data, HadISST, ERA5 reanalysis, and the Niño3.4 index, this study examines long-term changes in TC frequency, intensity composition, track-density redistribution, lifecycle-stage displacement, and associated SST–circulation linkages. Results show that annual TC frequency decreased significantly, whereas the proportion of super typhoons increased. Meanwhile, TC track density decreased over the tropical western Pacific but increased over parts of the subtropical WNP, leading to a significant poleward shift of the annual track centroid. Lifecycle decomposition further reveals strong intensity dependence. Severe tropical storms exhibit the most robust poleward signal, with significant northward shifts in lifetime maximum intensity and dissipation latitude, as well as enhanced genesis-to-dissipation displacement. Environmental analyses indicate that the poleward redistribution is associated with a La Niña-like Pacific SST pattern, western Pacific warming, northwestward displacement of the WNP subtropical high, and steering-flow anomalies favorable for poleward TC motion. These findings suggest that WNP TC risk and regional hazard exposure are being reshaped not only by changes in frequency and intensity composition, but also by spatial redistribution and lifecycle evolution.

Drought stress has significant impacts on the structure and carbon cycling processes of forest ecosystems. Forest height (H), as a key vegetation structural parameter, plays a crucial yet poorly understood role linking vegetation responses to drought stress. This study, utilizing multi-source remote sensing datasets and forest dynamic monitoring across China, combined with the Standardized Precipitation Evapotranspiration Index (SPEI), systematically investigated the structure–function relationships and drought responses in forest ecosystems. Spatial analysis revealed that averaged forest height exceeded 39 m in southeastern China, while the leaf area index (LAI) displayed a decreasing gradient from southeast to northwest. Gross primary productivity (GPP) exhibited spatial coupling with structural metrics, as quantified by the fitted equation (GPP = − 1.54H + 12.94LAI + 92.8, R ² = 0.71), confirming the synergistic regulation of photosynthetic efficiency by forest structure. A multi-temporal analysis of SPEI (1-, 3-, 6-, 12-month scales) identified cumulative drought intensification in northern arid zones, with drought-affected areas (SPEI < 0) covering 48% at the 12-month scale. Specifically, we found that drought duration mediated GPP responses through phase-dependent mechanisms: short-term drought (1–3 months) caused persistent GPP suppression, medium-term drought (6 months) permitted partial recovery, while tall forests suffered exacerbated GPP declines under long-term prolonged drought (12 months). By quantifying the relationship between drought stress, LAI, and GPP, this study demonstrated that forest height modulates drought adaptation through coordinated adjustments in LAI and GPP. These satellite-derived findings provide a mechanistic basis for regionally differentiated ecological restoration strategies. Critically, our results reveal that forest height plays a dual role: it can buffer the impact of short-term drought but may exacerbate ecosystem vulnerability under prolonged arid conditions.

Despite the increased frequency and intensity of meteorological droughts, Eurasian vegetation has demonstrated resilience during droughts or dry spells, possibly due to soil moisture retention from seasonal snowmelt. In this study, we present the first continental-scale investigation of quantifying this critical relationship through a comprehensive analysis of drought indices, snowmelt patterns, and soil moisture retention dynamics from 1960 to 2024. The results show that drought severity varies spatially, with southwestern Eurasia experiencing extreme short-term droughts [standardized precipitation index (SPI) < −2.5] and broader regions facing prolonged drought (SPI −1.5 to −1.0). Spring snowmelt exceeds 45 mm in eastern China, central/southern Russia, and northern Europe, while other regions receive less. This directly influences summer soil moisture, with high-snowmelt areas retaining more than 50 mm, compared to deficits of less than −25 mm in low-snowmelt zones such as southwestern Eurasia. Notably, summer precipitation shows weak correlations ( r < −0.25) with soil moisture retention in drought-prone areas, highlighting snowmelt’s disproportionate importance. Furthermore, the empirical orthogonal function (EOF) analysis confirms a strong snowmelt–soil moisture coupling in northern Eurasia (48.1% variance), but concerning trends emerge: snowmelt declines in Siberia and Scandinavia correspond with drying in central Asia and southern Europe. While central Russia shows increasing snowmelt, overall trends indicate reduced snowpack persistence and earlier melt timing. These changes threaten the historical balance between water availability and ecological needs. Our findings emphasize the need for adaptive water management strategies to offset the loss of spring snowmelt buffers, which serve as a natural drought defense in the mid- and high latitudes of Eurasia. Significance Statement: This study explores the interplay between spring snowmelt and soil moisture retention during meteorological droughts from 1960 to 2024, specifically in the mid- and high latitudes of Eurasia. Our findings offer new insights into the hydrological processes that govern soil moisture dynamics in these regions, particularly under drought conditions. By utilizing a combination of statistical analyses, we highlight the critical role of snowmelt in influencing soil moisture behavior under the drought intensification conditions, providing implications for both climate research and drought mitigation strategies.

Understanding and predicting changes in land evapotranspiration (ET) during droughts is crucial for elucidating land-atmosphere interactions. While previous studies have primarily focused on overall ET or individual components, they often overlook the mutual influences among different ET components. To address this gap, this study presents the first global analysis of concurrent changes in multiple ET components during meteorological droughts. Utilizing advanced satellite-based and reanalysis-based datasets, including the Global Land Evaporation Amsterdam Model (GLEAM) and the ECMWF reanalysis v5 (ERA5-Land) for the period 2000–2020, we find that the average probability of drought-driven increases in ET (P(ET+)) was approximately 0.5 during drought events. In contrast, the probabilities of an increase for the primary components—bare soil evaporation (Eb), canopy interception evaporation (Ei), and transpiration (Et)—were below 0.4, while the probability of drought-driven increases in snow sublimation (Es) exceeded 0.6. Globally, ET decreased by an average of 20.5 mm/month during a given drought period, though it increased in humid regions and snow-covered areas. Mild droughts resulted in an overall ET reduction, with increases in Eb and Es partially offsetting decreases in Et and Ei. However, as drought intensity increased, ET shifted toward an increase, which was constrained under extreme droughts. These findings highlight the asymmetric and interdependent responses of ET components to drought, underscoring the critical need to understand these interactions for accurately predicting ET dynamics under drought stress.

The frequency and severity of meteorological drought across Eastern Asia (EA) are observed and projected to increase with ongoing global climate change. However, the temporal and spatial responses of land surface elements including soil moisture and runoff to meteorological drought remain insufficiently understood and characterised, especially in terms of quantifying the differentiated lag time of soil moisture and hydrological drought responses. In this study, we investigate the spatiotemporal response of soil moisture and hydrological droughts to meteorological drought across EA, using the Standardised Precipitation Index (SPI; a measure of precipitation deficit), Standardised Soil Moisture Drought Index (SSMDI; quantifying soil moisture anomalies) and Standardised Streamflow Index (SSI; assessing streamflow deviations) at short‐ (1–3), medium‐ (6–9) and long‐scales (12–24 months). The results show that in northern EA, soil moisture droughts indicate weak negative correlations with meteorological droughts at 1–6 month time scales, while in southern regions, stronger positive correlations are observed at 9–24 month time scales. Hydrological droughts exhibit consistently strong positive correlations with meteorological droughts across all time scales, especially in the southern regions of EA. Northern regions exhibit longer lag times of up to 8 months of soil moisture droughts in response to meteorological drought, whereas southern regions exhibit rapid responses (1 month). In all time scales, hydrological droughts in northern regions of EA have a delayed lag times extending up to 10 months. As climate change and land use changes may amplify drought impacts, long‐term forecasting and adaptive management are essential to mitigate water shortages and ecological stress across the EA region.

Understanding the pattern of changes in extreme heat is crucial to developing climate change adaptation strategies. Existing studies mostly focus on changes in air temperature and tend to overlook soil temperature; however, changes in extreme heat in air and soil can be inconsistent under global change and water–carbon cycling may be more sensitive to soil condition. In this study, we examine the global pattern of long-term trends in the difference between air temperature and soil temperature (T _soil − T _2m) for the hottest month of the year during the period of 1961–2022. The results show that in certain hotspots, such as the middle and high latitudes of Eurasia, the Mediterranean, and the Western United States, the increasing trend in soil temperature has exceeded the increasing trend in 2 m air temperature during the warm season, implying that the land surface can contribute to the increase in air temperature extreme by releasing more heat than before. Our study suggest that the effect of soil temperature to air temperature is strongly related to the partitioning of surface latent heat, sensible heat (H) and soil heat flux (G). In the hot spots, T _soil − T _2m was significantly positively correlated with H and G while a significant negative correlation was found with evaporative fraction (EF) (p< 0.05), and the significant correlations with G and EF exhibit greater spatial heterogeneity. Moreover, the higher the degree of vegetation cover and soil moisture the smaller the difference between soil and air high temperatures. Therefore, changes in vegetation cover and land use management may play an important role in regulating the range of soil and air temperature differences as well as land-atmosphere coupling effects on heat extreme.

Retrieval of atmospheric aerosol optical depth (AOD) has been a challenge for Earth satellite observations, mainly due to the difficulty of estimating surface reflectance with the combined influence of land–atmosphere coupling. Current major satellite AOD retrieval products have low spatial resolution under complex surface processes. In this study, we further improved the surface reflectance by modeling the error correction based on the previous AOD retrieval and obtained more accurate AOD retrieval results. A lookup table was constructed using the Second Simulation of Satellite Signal in the Solar Spectrum (6S) to enable high-precision AOD retrieval. The accuracy of the algorithm's retrieval was verified by observations of the Aerosol Robotic Network (AERONET). From the validation results, we find that among the nine Multi-angle Imaging SpectroRadiometer (MISR) angles, the retrieved AOD has the best retrieved results with the AOD observed at the An angle (Taihu: R = 0.81, relative mean bias (RMB) = 0.68; Xuzhou-CUMT: R = 0.73, RMB = 0.78). This study will help to further improve the retrieval accuracy of multi-angle AOD at large spatial scales and long time series. The retrieved AOD based on the improved method has the advantages of fewer missing pixels and finer spatial resolution compared to the MODIS AOD products and our previous estimates.