In this work, we identified 65 auroral arcs that stretched out from the equatorward boundary of auroral oval with azimuthal extensions, and investigated their upstream triggering, by utilizing conjunctions between the THEMIS probes and the all-sky imagers at AGO P1 and South Pole stations. The results show that the magnetopause motions induced by pressure enhancements associated with IMF discontinuities or foreshock cavities likely generate upward FACs in the closed field lines near the magnetopause. The inward and azimuthal motions of magnetopause caused equatorward-moving auroral arcs, which extended westward or eastward, centered in the prenoon (12–13 MLT) or postnoon (9–10 MLT) sectors, respectively. The dawn-dusk asymmetry in this distribution may be due to the contribution from foreshock activities. Furthermore, stronger compression can push the magnetopause further inward, causing FACs and the corresponding discrete auroras to be distributed over a wider region extending further in both latitude and local time.
{"title":"Field-Aligned Currents Induced by Magnetopause Motions Under Pressure Perturbations","authors":"Boyi Wang, Xinyu Xu, Yukitoshi Nishimura, Yen-Jung Wu, Zhonghua Xu, Primož Kajdic, De-Sheng Han, Yi Wang, Xueshang Feng","doi":"10.1029/2024gl111958","DOIUrl":"https://doi.org/10.1029/2024gl111958","url":null,"abstract":"In this work, we identified 65 auroral arcs that stretched out from the equatorward boundary of auroral oval with azimuthal extensions, and investigated their upstream triggering, by utilizing conjunctions between the THEMIS probes and the all-sky imagers at AGO P1 and South Pole stations. The results show that the magnetopause motions induced by pressure enhancements associated with IMF discontinuities or foreshock cavities likely generate upward FACs in the closed field lines near the magnetopause. The inward and azimuthal motions of magnetopause caused equatorward-moving auroral arcs, which extended westward or eastward, centered in the prenoon (12–13 MLT) or postnoon (9–10 MLT) sectors, respectively. The dawn-dusk asymmetry in this distribution may be due to the contribution from foreshock activities. Furthermore, stronger compression can push the magnetopause further inward, causing FACs and the corresponding discrete auroras to be distributed over a wider region extending further in both latitude and local time.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"83 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Guilherme W. S. de Melo, Ingo Grevemeyer, Dietrich Lange, Dirk Metz, Heidrun Kopp
The rupture behavior of large oceanic strike-slip earthquakes remains largely unresolved using seismic signals recorded thousands of kilometers away from the source area. Large submarine earthquakes, however, generate hydroacoustic T-waves propagating through the ocean over long distances. Here, we show that these T-waves recorded at regional distances on the Ascension hydrophone array of the International Monitoring System can provide critical information on the earthquake location and rupture behavior. We use recordings from 47 events in oceanic transform faults, ranging in magnitude from 5.6 ≤ Mw ≤ 7.1, to investigate the rupture processes. We find that most strike-slip earthquakes show unilateral rupture behavior, while a few larger events were more complex. Furthermore, earthquakes in oceanic transforms have longer ruptures than events of the same magnitude in continental faults. We argue that differences in the scaling relation of oceanic and continental strike-slip earthquakes support a lower rigidity in the oceanic lithosphere caused by hydration.
{"title":"Relationship Between Rupture Length and Magnitude of Oceanic Transform Fault Earthquakes","authors":"Guilherme W. S. de Melo, Ingo Grevemeyer, Dietrich Lange, Dirk Metz, Heidrun Kopp","doi":"10.1029/2024gl112891","DOIUrl":"https://doi.org/10.1029/2024gl112891","url":null,"abstract":"The rupture behavior of large oceanic strike-slip earthquakes remains largely unresolved using seismic signals recorded thousands of kilometers away from the source area. Large submarine earthquakes, however, generate hydroacoustic T-waves propagating through the ocean over long distances. Here, we show that these T-waves recorded at regional distances on the Ascension hydrophone array of the International Monitoring System can provide critical information on the earthquake location and rupture behavior. We use recordings from 47 events in oceanic transform faults, ranging in magnitude from 5.6 ≤ <i>M</i><sub><i>w</i></sub> ≤ 7.1, to investigate the rupture processes. We find that most strike-slip earthquakes show unilateral rupture behavior, while a few larger events were more complex. Furthermore, earthquakes in oceanic transforms have longer ruptures than events of the same magnitude in continental faults. We argue that differences in the scaling relation of oceanic and continental strike-slip earthquakes support a lower rigidity in the oceanic lithosphere caused by hydration.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"3 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Borgnino, F. Desbiolles, A. N. Meroni, C. Pasquero
Ocean and atmosphere exchange energy and mass at their interface at a rate that depends on the dynamical and thermodynamical disequilibrium between water and air. In this work, using an atmospheric model forced by observed high resolution sea surface temperature (SST) fields, we show that the air-sea disequilibrium is also maintained by atmospheric processes driven by fine scale SST patterns. The analysis focuses on north-western tropical Atlantic and indicates that fine scale SST anomalies modulate the air column stability and the entrainment of dry air at boundary layer top. The main effect is a modification in near surface temperature and moisture content, which produces a negative response of relative humidity to local SST variability, resulting in a larger sensitivity of latent than sensible heat fluxes to local SST anomalies. Such sensitivities are quantified as 95% and 70% of fluxes upper bound, estimated with local atmospheric properties uncorrelated with SST anomalies.
{"title":"Lower Tropospheric Response to Local Sea Surface Temperature Anomalies: A Numerical Study in the EUREC4A Region","authors":"M. Borgnino, F. Desbiolles, A. N. Meroni, C. Pasquero","doi":"10.1029/2024gl112294","DOIUrl":"https://doi.org/10.1029/2024gl112294","url":null,"abstract":"Ocean and atmosphere exchange energy and mass at their interface at a rate that depends on the dynamical and thermodynamical disequilibrium between water and air. In this work, using an atmospheric model forced by observed high resolution sea surface temperature (SST) fields, we show that the air-sea disequilibrium is also maintained by atmospheric processes driven by fine scale SST patterns. The analysis focuses on north-western tropical Atlantic and indicates that fine scale SST anomalies modulate the air column stability and the entrainment of dry air at boundary layer top. The main effect is a modification in near surface temperature and moisture content, which produces a negative response of relative humidity to local SST variability, resulting in a larger sensitivity of latent than sensible heat fluxes to local SST anomalies. Such sensitivities are quantified as 95% and 70% of fluxes upper bound, estimated with local atmospheric properties uncorrelated with SST anomalies.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"30 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The distribution of volcanic thermal emission on Io might reflect the location and magnitude of tidal heating, so it is important to accurately identify Io’s volcanoes to enable robust interior modeling. Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) “Io Hot Spot Distribution Detected by Juno/JIRAM,” Geophysical Research Letters, 50, e2022GL100597 (2023) report the positions of hot spots on Io at high latitudes that are apparently spurious. This appears to be due to mis-registration of JIRAM images to a frame of reference, leading to the same hot spot being located in different positions on Io’s surface. Other hot spots are not identified. The outcome of these additional and missing detections is a skewing of volcanic activity toward high latitudes, suggesting more polar activity than that seen at lower latitudes. This distribution of thermal sources would support a preponderance of deep mantle tidal heating, a conclusion not supported by other analyses of the same data.
木卫一上火山热发射的分布可能反映潮汐加热的位置和大小，因此准确识别木卫一上的火山对于实现鲁棒的内部建模至关重要。Zambon et al. （2023, https://doi.org/10.1029/2022gl100597）“Juno/JIRAM探测到的木卫一热点分布”，地球物理研究快报，50,e2022GL100597（2023）报道了木卫一高纬度地区的热点位置，这些热点显然是假的。这似乎是由于JIRAM图像与参考框架的错误配准，导致相同的热点位于木卫一表面的不同位置。其他热点尚未确定。这些额外的和缺失的探测结果是火山活动向高纬度倾斜，这表明极地活动比低纬度地区更多。热源的这种分布将支持深层地幔潮汐加热的优势，这一结论没有得到对相同数据的其他分析的支持。
{"title":"Comment on “Io Hot Spot Distribution Detected by Juno/JIRAM” by Zambon et al.","authors":"Ashley Gerard Davies","doi":"10.1029/2024gl110698","DOIUrl":"https://doi.org/10.1029/2024gl110698","url":null,"abstract":"The distribution of volcanic thermal emission on Io might reflect the location and magnitude of tidal heating, so it is important to accurately identify Io’s volcanoes to enable robust interior modeling. Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) “Io Hot Spot Distribution Detected by <i>Juno</i>/JIRAM,” Geophysical Research Letters, 50, e2022GL100597 (2023) report the positions of hot spots on Io at high latitudes that are apparently spurious. This appears to be due to mis-registration of JIRAM images to a frame of reference, leading to the same hot spot being located in different positions on Io’s surface. Other hot spots are not identified. The outcome of these additional and missing detections is a skewing of volcanic activity toward high latitudes, suggesting more polar activity than that seen at lower latitudes. This distribution of thermal sources would support a preponderance of deep mantle tidal heating, a conclusion not supported by other analyses of the same data.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"23 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interannual variability of the Indonesian Throughflow (ITF) in the Makassar Strait in 2015–2017 is analyzed using observations and ORAS5 reanalysis data. Strong northward and ensuing strong southward current anomalies in the sub-thermocline Makassar Strait are identified during and after the 2015/2016 El Niño, respectively. However, the upper layer current anomalies are weakly southward in September–October 2015 and strongly northward in April 2016 through April 2017. These anomalies of the Makassar Strait throughflow in the upper layer are found to be induced mainly by Indian Ocean Kelvin waves forcing sea surface height anomalies off the south Java coasts. The sub-thermocline current anomalies are found to be generated by the westward and downward propagation of interannual Rossby waves from the central equatorial Pacific during and after the 2015/2016 El Niño. The results underline the importance of the planetary wave propagation into the Indonesian seas in forcing the ITF anomalies.
{"title":"Interannual Variability of the Indonesian Throughflow in the Makassar Strait Associated With the 2015/2016 Super El Niño","authors":"Wending Xu, Dongliang Yuan, Mingting Li","doi":"10.1029/2024gl111709","DOIUrl":"https://doi.org/10.1029/2024gl111709","url":null,"abstract":"The interannual variability of the Indonesian Throughflow (ITF) in the Makassar Strait in 2015–2017 is analyzed using observations and ORAS5 reanalysis data. Strong northward and ensuing strong southward current anomalies in the sub-thermocline Makassar Strait are identified during and after the 2015/2016 El Niño, respectively. However, the upper layer current anomalies are weakly southward in September–October 2015 and strongly northward in April 2016 through April 2017. These anomalies of the Makassar Strait throughflow in the upper layer are found to be induced mainly by Indian Ocean Kelvin waves forcing sea surface height anomalies off the south Java coasts. The sub-thermocline current anomalies are found to be generated by the westward and downward propagation of interannual Rossby waves from the central equatorial Pacific during and after the 2015/2016 El Niño. The results underline the importance of the planetary wave propagation into the Indonesian seas in forcing the ITF anomalies.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"35 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Enze Dong, Fengfei Song, Lixin Wu, Lu Dong, Shengpeng Wang, Fukai Liu, Hong Wang
The double-Intertropical Convergence Zone (ITCZ) bias is a common model bias, which has puzzled the climate model community for several decades. Here, by comparing a high- and low-resolution state-of-the-art model CESM1, it is found that the double-ITCZ bias is largely reduced in the high-resolution CESM1. The key reason is the realistic colder sea surface temperature (SST) over the southeast Pacific (SEP) in the high-resolution model. This realistic SEP SST is mainly due to a spuriously deeper mixed layer with a more realistic wind, as the sensitivity of mixed layer depth to wind is overestimated in both versions of CESM1. The better representation of terrain, such as Andes Mountains, elevates warm advection from inland to the coastal region, which maintains the inversion structure favorable for low cloud. The resultant increased coastal cloud in the high-resolution CESM1 causes the colder coastal SST, thus improving the wind and deepening the mixed layer.
{"title":"The Process-Oriented Understanding on the Reduced Double-ITCZ Bias in the High-Resolution CESM1","authors":"Enze Dong, Fengfei Song, Lixin Wu, Lu Dong, Shengpeng Wang, Fukai Liu, Hong Wang","doi":"10.1029/2024gl112087","DOIUrl":"https://doi.org/10.1029/2024gl112087","url":null,"abstract":"The double-Intertropical Convergence Zone (ITCZ) bias is a common model bias, which has puzzled the climate model community for several decades. Here, by comparing a high- and low-resolution state-of-the-art model CESM1, it is found that the double-ITCZ bias is largely reduced in the high-resolution CESM1. The key reason is the realistic colder sea surface temperature (SST) over the southeast Pacific (SEP) in the high-resolution model. This realistic SEP SST is mainly due to a spuriously deeper mixed layer with a more realistic wind, as the sensitivity of mixed layer depth to wind is overestimated in both versions of CESM1. The better representation of terrain, such as Andes Mountains, elevates warm advection from inland to the coastal region, which maintains the inversion structure favorable for low cloud. The resultant increased coastal cloud in the high-resolution CESM1 causes the colder coastal SST, thus improving the wind and deepening the mixed layer.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"28 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ryan M. Bright, Luca Caporaso, Gregory Duveiller, Matteo Piccardo, Alessandro Cescatti
Large-scale re-/afforestation projects afford sizable atmospheric CO2 removals yet questions loom surrounding their potentially offsetting biogeophysical radiative forcings. Forest area change alters not only the surface albedo but also heat, moisture, and momentum fluxes, which in turn modify the atmosphere's radiative, thermodynamical, and dynamical properties. These so-called radiative forcing “adjustments” have been little examined in re-/afforestation contexts, and many questions remain surrounding their relevance in relation to the instantaneous forcing from the surface albedo change—and whether they can affect Earth's radiative energy balance in regions remote from where the re-/afforestation occurs. Here, we quantified biogeophysical radiative forcings and adjustments from realistically scaled re-/afforestation in Europe at high spatial resolution and found that adjustments with high signal-to-noise were largely confined to only a few months and to the region of re-/afforestation. Adjustments were dominated by perturbed low-level clouds and rarely exceeded ±25% of the annual albedo change forcing.
{"title":"Biogeophysical Radiative Forcings of Large-Scale Afforestation in Europe Are Highly Localized and Dominated by Surface Albedo Change","authors":"Ryan M. Bright, Luca Caporaso, Gregory Duveiller, Matteo Piccardo, Alessandro Cescatti","doi":"10.1029/2024gl112739","DOIUrl":"https://doi.org/10.1029/2024gl112739","url":null,"abstract":"Large-scale re-/afforestation projects afford sizable atmospheric CO<sub>2</sub> removals yet questions loom surrounding their potentially offsetting biogeophysical radiative forcings. Forest area change alters not only the surface albedo but also heat, moisture, and momentum fluxes, which in turn modify the atmosphere's radiative, thermodynamical, and dynamical properties. These so-called radiative forcing “adjustments” have been little examined in re-/afforestation contexts, and many questions remain surrounding their relevance in relation to the instantaneous forcing from the surface albedo change—and whether they can affect Earth's radiative energy balance in regions remote from where the re-/afforestation occurs. Here, we quantified biogeophysical radiative forcings and adjustments from realistically scaled re-/afforestation in Europe at high spatial resolution and found that adjustments with high signal-to-noise were largely confined to only a few months and to the region of re-/afforestation. Adjustments were dominated by perturbed low-level clouds and rarely exceeded ±25% of the annual albedo change forcing.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"20 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142929738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiangling Ding, Zhaoguo He, Zhiyong Wu, Jiang Yu, Kun Li, Yuguang Ye, Qiugang Zong
Exohiss serves as a typical imprint of the outward energy release from plasmaspheric hiss. The distribution of exohiss under the effect of Landau damping has not been thoroughly evaluate. On the basis of observations from the Van Allen Probes on 17 February 2014, we performed two-dimensional ray tracing simulations to model the evolution of hiss waves propagating from the geomagnetic equator in plasmasphere. The results show that the hiss wave power decreases rapidly as the waves enter the plasmatrough under the enhanced Landau damping effect of hot electrons. Furthermore, we perform a statistical analysis of the simulation results from multiple rays and obtain the radial, latitudinal, and frequency distributions of the exohiss wave power. The modeled distribution characteristics of exohiss align well with observations, suggesting that Landau damping is crucial in shaping the morphology of exohiss in the inner magnetosphere.
{"title":"Radial and Latitudinal Distributions of the Exohiss Under the Effect of Landau Damping","authors":"Xiangling Ding, Zhaoguo He, Zhiyong Wu, Jiang Yu, Kun Li, Yuguang Ye, Qiugang Zong","doi":"10.1029/2024gl112567","DOIUrl":"https://doi.org/10.1029/2024gl112567","url":null,"abstract":"Exohiss serves as a typical imprint of the outward energy release from plasmaspheric hiss. The distribution of exohiss under the effect of Landau damping has not been thoroughly evaluate. On the basis of observations from the Van Allen Probes on 17 February 2014, we performed two-dimensional ray tracing simulations to model the evolution of hiss waves propagating from the geomagnetic equator in plasmasphere. The results show that the hiss wave power decreases rapidly as the waves enter the plasmatrough under the enhanced Landau damping effect of hot electrons. Furthermore, we perform a statistical analysis of the simulation results from multiple rays and obtain the radial, latitudinal, and frequency distributions of the exohiss wave power. The modeled distribution characteristics of exohiss align well with observations, suggesting that Landau damping is crucial in shaping the morphology of exohiss in the inner magnetosphere.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"7 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142929737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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