Geophysical Research Letters最新文献

{"title":"Resultant Force on Grains of a Real Sand Dune: How to Measure It?","authors":"R. F. Miotto,&nbsp;C. A. Alvarez,&nbsp;D. S. Borges,&nbsp;W. R. Wolf,&nbsp;E. M. Franklin","doi":"10.1029/2025GL116942","DOIUrl":"https://doi.org/10.1029/2025GL116942","url":null,"abstract":"<p>Barchan dunes usually appear under the action of one-directional fluid flows, being found on Earth, Mars, and other celestial bodies; however, although ubiquitous in nature, understanding dune dynamics at the grain scale is challenging due to the vast number of grains involved. Here, based on subaqueous experiments using a high-speed camera, discrete numerical computations solving the motion at the grain scale, and a special training of a convolutional neural network, we show that it is, in fact, possible to estimate the resultant force acting on the grains of a barchan dune by using images. This procedure opens new possibilities for measuring the resultant force not only on the grains of a dune, but also on relatively small elements that are imaged over time, such as rocks, boulders, rovers, and human-built constructions photographed by satellites on terrestrial and Martian landscapes.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL116942","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Forced Changes in the North Atlantic Storm Track Over the Last Millennium","authors":"O. Hess,&nbsp;R. Chemke","doi":"10.1029/2025GL115894","DOIUrl":"https://doi.org/10.1029/2025GL115894","url":null,"abstract":"<p>The North Atlantic storm track largely affects the regional weather and climate in Western Europe and the Eastern United States. While recent and projected changes in the storm track due to human emissions have been extensively studied, the storms' response to natural forcings in past centuries is largely unknown. Using climate model simulations of the pre-industrial millennium, we find that natural forcings acted to intensify the summer storm track over multi-centennial timescales, with minor impacts on the winter storm track. In contrast to the human-induced larger warming of high latitudes relative to low latitudes, which has weakened the summer storm track, natural agents cooled high latitudes more, enhancing the meridional temperature gradient, which intensified the storm track. This study highlights the unprecedented impacts of human emissions relative to the last millennium's natural forcing agents and the importance of including natural forcings in model projections.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL115894","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Statistical Study on L-O Mode Saturn Kilometric Radiation","authors":"Junhao Pan,&nbsp;Siyuan Wu,&nbsp;Shengyi Ye,&nbsp;Georg Fischer,&nbsp;Laurent Lamy,&nbsp;Philippe Zarka,&nbsp;Ulrich Taubenschuss","doi":"10.1029/2025GL114876","DOIUrl":"https://doi.org/10.1029/2025GL114876","url":null,"abstract":"<p>Based on the 13 years-long observation of Saturn kilometric radiation (SKR) by the Cassini/Radio and Plasma Wave Science instrument, this study derives statistics for left-hand (L-O) mode SKR emissions. These emissions span a frequency range from below 10 kHz to approximately 1,000 kHz, with spectral flux densities ranging between 10⁻²⁴ and 10⁻¹⁸ W/(m² Hz) consistent with, although fainter than, right-hand mode SKR. Predominantly observed within 20 Saturn radii, the occurrence rates of L-O mode SKR exhibit a preference below 20° in latitude, and a local time asymmetry with a higher occurrence rate on the dayside. Occurrence maps indicate that low-frequency (&lt;100 kHz) L-O mode SKR may be obstructed by the Enceladus plasma torus due to the higher electron density, while high-frequency (&gt;100 kHz) emissions can pass through unhindered. Additionally, a substantial proportion of high-latitude L-O mode emissions exhibit strong elliptical polarization, contrasting with predominantly circular polarization observed at low latitudes.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL114876","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Retrieval of Total Precipitable Water Under All-Weather Conditions From Himawari-8/AHI Observations Using the Generative Diffusion Model","authors":"Haixia Xiao,&nbsp;Feng Zhang,&nbsp;Renhe Zhang,&nbsp;Feng Lu,&nbsp;Miao Cai,&nbsp;Lingxiao Wang","doi":"10.1029/2025GL117075","DOIUrl":"https://doi.org/10.1029/2025GL117075","url":null,"abstract":"<p>Accurate, spatiotemporally continuous total precipitable water (TPW) data under all-weather conditions are crucial for understanding water and energy cycles. This study introduces TPWDiff-CB, a novel deep learning-based TPW retrieval model that employs a generative diffusion model. TPWDiff-CB effectively estimates TPW under all-weather conditions by leveraging thermal infrared observations from the Advanced Himawari Imager aboard Himawari-8. Specifically, when compared to radiosonde TPW, TPWDiff-CB yields a correlation coefficient (<i>R</i>) of 0.98 and a root mean square error of 4.51 mm under all-weather condtions. The model demonstrates exceptional performance, maintaining near-identical accuracy under both cloudy and clear-sky conditions. Its robust capability in learning the TPW distribution and performing spatiotemporal retrievals surpasses that of traditional machine learning model. These findings highlight TPWDiff-CB's high accuracy and its promising potential for applications in weather and climate research.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL117075","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of Raman Scattering on SIF Retrievals From Hyperspectral Satellite Observations","authors":"Suniti Sanghavi,&nbsp;Christian Frankenberg,&nbsp;Robert R. Nelson,&nbsp;Christopher W. O’Dell,&nbsp;Robert Rosenberg,&nbsp;Joanna Joiner","doi":"10.1029/2024GL112777","DOIUrl":"https://doi.org/10.1029/2024GL112777","url":null,"abstract":"&lt;p&gt;Solar-induced chlorophyll fluorescence (SIF) retrieved from spaceborne measurements is widely used as an indicator of vegetation activity. However, this weak emission can be confused with the inelastic scattering component of sunlight that lacks distinctive Fraunhofer lines. Through high-fidelity radiative transfer simulations of nadir-mode observations near the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{O}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; A-band, we show that this signal can cause artificially high SIF estimates–reaching up to 0.35 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;W&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mi&gt;r&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}mathrm{W}/mathrm{n}mathrm{m}/mathrm{s}mathrm{r}/mathrm{m}}^{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; over vegetation-free regions like the Sahara, Greenland, and Antarctica. Current “zero-level offset” corrections, originally intended to address instrument errors, partially remove these erroneous signals but leave significant residual biases (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;0.15 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;W&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mi&gt;r&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}mathrm{W}/mathrm{n}mathrm{m}/mathrm{s}mathrm{r}/mathrm{m}}^{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) that correlate with surface brightness, elevation, and viewing geometry. We introduce a lookup table approach based on physical simulations to directly estimate and subtract ine","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GL112777","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Holocene Human Impact on Tropical Soil Erosion in the Maritime Continent","authors":"Yanming Ruan,&nbsp;Mahyar Mohtadi,&nbsp;Lydie M. Dupont,&nbsp;Dierk Hebbeln,&nbsp;Sander van der Kaars,&nbsp;Wenwen Chen,&nbsp;Ellen C. Hopmans,&nbsp;Stefan Schouten,&nbsp;Matthias Prange,&nbsp;Jens Hefter,&nbsp;Gesine Mollenhauer,&nbsp;Enno Schefuß","doi":"10.1029/2025GL114695","DOIUrl":"https://doi.org/10.1029/2025GL114695","url":null,"abstract":"<p>Human activities have profoundly modified the fluxes in the global sediment cycle. However, the anthropogenic forcing on soil erosion beyond instrumental records or historical documentation is largely unknown. Here we analyze markers for low-intensity fires and soil erosion in East Java over the past 5,000 years. We find evidence of a substantial human impact on fire occurrence due to the onset/intensification of swidden cultivation around 3,500 years ago, in the absence of changes in regional hydroclimate or vegetation. Highest soil erosion occurred during the past 500 years, coinciding with a transition toward permanent agriculture. Human-impacted soil erosion was further amplified by intense monsoonal rainfall and strong rainfall seasonality around 2,000 and 300 years ago. With such rainfall anomalies projected to occur with higher frequency and severity in the tropics under the ongoing greenhouse warming, our results suggest an accelerating erosion rate in the future, posing risks for natural resources.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL114695","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deforestation Could Push Amazonia Close to a Tipping Point Under Future Climate Change","authors":"László Hunor Hajdu,&nbsp;Antoon G. C. A. Meesters,&nbsp;A. Johannes Dolman,&nbsp;Andrew D. Friend","doi":"10.1029/2024GL108304","DOIUrl":"https://doi.org/10.1029/2024GL108304","url":null,"abstract":"<p>We use a coupled land-surface-atmosphere single-column model to examine the effects of deforestation and changed advective moisture flux (AMF) on the Amazonian system. We find that from current conditions, a reduction to 35% forest cover, or a ∼10% decrease in AMF (∼6% less precipitation), causes the system to transition from a wet climate with rainforest to a drier climate with savanna-like vegetation. The system responds highly non-linearly to the combined influences of the AMF and deforestation. Small changes in either forest cover or moisture advection are capable of causing the system to flip abruptly between stable forest, savanna, or shrubland states. Model behavior is strongly influenced by the feedback between the land surface and the atmosphere, with natural vegetation changes playing a major role. Our results suggest that continued deforestation is likely to trigger a transition to a savanna-like state across Amazonia within this century under current climate projections.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GL108304","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ENSO-Driven Variability in Ozone Sources and Its Impact on Tropospheric Ozone Radiative Forcing","authors":"Arman Pouyaei,&nbsp;Paul Ginoux,&nbsp;Vaishali Naik,&nbsp;Jing Feng,&nbsp;Larry W. Horowitz,&nbsp;Fabien Paulot","doi":"10.1029/2025GL115898","DOIUrl":"https://doi.org/10.1029/2025GL115898","url":null,"abstract":"<p>Ozone is the third strongest anthropogenic greenhouse gas with highest radiative efficiency in the tropical upper troposphere. Variability driven by El Niño-Southern Oscillation (ENSO) modulates tropospheric column ozone instantaneous radiative forcing (TCO-IRF) through changes in atmospheric dynamics, natural emissions, and stratospheric-tropospheric exchange in the tropics. Using the Geophysical Fluid Dynamics Laboratory Atmospheric Model v4.1, which includes detailed ozone chemistry, we analyze the impacts of drivers on the ozone profile associated with El Niño and La Niña events between 2004 and 2019. Findings show that alongside ENSO-driven atmospheric circulation changes, lightning-induced nitrogen oxide over Atlantic and Pacific oceans, subtropical stratospheric intrusions, and biomass burning in equatorial Asia significantly impact TCO-IRF in the tropics. Additionally, radiative effects from tropical tropospheric ozone increase by up to 0.03 Wm⁻² during La Niña seasons and weaken by 0.02 Wm⁻² in El Niño seasons, highlighting the importance of assessing ENSO-driven TCO-IRF variability for understanding future climate.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL115898","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Increasing Trends in Soil Heat Extremes Following Flash Drought Outbreaks","authors":"Yangyang Jing,&nbsp;Shuo Wang,&nbsp;Pak Wai Chan,&nbsp;Zong-Liang Yang","doi":"10.1029/2025GL116316","DOIUrl":"https://doi.org/10.1029/2025GL116316","url":null,"abstract":"<p>Flash droughts, characterized by rapid declines in soil moisture (SM), pose significant threats to ecosystems. Understanding the response of soil temperature (ST) to the rapid SM decline during flash droughts has critical implications for the root systems of terrestrial ecosystems. In this study, we identify soil heat extreme events that follow flash drought outbreaks. Our findings reveal that global land areas experience a significant increase in soil heat after the outbreak stage of flash droughts, with affected areas expanding by an average of 4.36%–9.74% per decade. Humid regions show a significantly higher percentage of affected land areas compared to arid regions. The proportion of soil heat extremes following flash drought outbreaks increases significantly by 16.53%–23.38%, with event days occurring twice as often, particularly in humid regions. This suggests that root systems will encounter exacerbated stress as soil heat intensifies during sudden abnormal soil drying.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL116316","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probabilistic Diffusion Models Advance Extreme Flood Forecasting","authors":"Zhigang Ou,&nbsp;Congyi Nai,&nbsp;Baoxiang Pan,&nbsp;Yi Zheng,&nbsp;Chaopeng Shen,&nbsp;Peishi Jiang,&nbsp;Xingcai Liu,&nbsp;Qiuhong Tang,&nbsp;Wenqing Li,&nbsp;Ming Pan","doi":"10.1029/2025GL115705","DOIUrl":"https://doi.org/10.1029/2025GL115705","url":null,"abstract":"<p>Extreme floods pose escalating risks in a changing climate, yet forecasting remains challenging due to peak flow underestimation and high uncertainty. We introduce diffusion-based runoff model (DRUM), a probabilistic deep learning (DL) approach that advances extreme flood forecasting across representative basins in the contiguous United States. DRUM outperforms state-of-the-art benchmarks, enhancing nowcasting skill for the top 1‰ of flows in 72.3% of studied basins. Under operational scenarios, DRUM extends reliable lead times by nearly a full day for 20- and 50-year floods. When evaluated with measured precipitation, an ideal condition, recall improves by 0.3–0.4 and the early warning window extends by 2.3 days for 50-year floods. The enhancement potential varies regionally, with precipitation-driven flood zones in the eastern and northwestern US benefiting most, gaining 3–7 days in lead time. These findings highlight the transformative potential of diffusion models as a cutting-edge generative AI technique for advancing hydrology and broader Earth system sciences.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 15","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL115705","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}