The social losses associated with extreme humid-heat events (EHHE) increased sharply in recent decades. This study has explored the changing relationship between EHHE in eastern China and tropical sea surface temperature (SST) anomalies. Results show that the monopolar mode of EHHE is significantly associated with spring SST anomalies in Northwest Pacific (NWP) before the mid-1990s, which can impact humid-heat conditions in eastern China through an atmospheric meridional overturning circulation extending from NWP to eastern China. Then, the associated eastward shift of convection center after the mid-1990s weakens connection between NWP SST anomalies and the monopolar mode. Further analysis reveals that the weakened Kelvin waves, induced by persistent SST anomalies from spring in tropical Indian Ocean after the mid-1990s, cause the westward-shifted anomalous convection in western Pacific, and then reinforce formation of the dipolar mode via exciting zonal wave trains. Numerical simulations via linear baroclinic model further validate atmospheric response to displacement of diabatic forcings.
{"title":"Shift in the Relationship Between Summer Extreme Humid-Heat Events in Eastern China and Tropical Sea Surface Temperature in the Mid-1990s","authors":"Wenyue He, Huopo Chen","doi":"10.1029/2024gl112715","DOIUrl":"https://doi.org/10.1029/2024gl112715","url":null,"abstract":"The social losses associated with extreme humid-heat events (EHHE) increased sharply in recent decades. This study has explored the changing relationship between EHHE in eastern China and tropical sea surface temperature (SST) anomalies. Results show that the monopolar mode of EHHE is significantly associated with spring SST anomalies in Northwest Pacific (NWP) before the mid-1990s, which can impact humid-heat conditions in eastern China through an atmospheric meridional overturning circulation extending from NWP to eastern China. Then, the associated eastward shift of convection center after the mid-1990s weakens connection between NWP SST anomalies and the monopolar mode. Further analysis reveals that the weakened Kelvin waves, induced by persistent SST anomalies from spring in tropical Indian Ocean after the mid-1990s, cause the westward-shifted anomalous convection in western Pacific, and then reinforce formation of the dipolar mode via exciting zonal wave trains. Numerical simulations via linear baroclinic model further validate atmospheric response to displacement of diabatic forcings.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"11 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142962777","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}
Jui-Chun Freya Chen, Sunyoung Park, Douglas R. MacAyeal
We construct a linear model of microseism power as a function of sea-ice concentration and ocean-wave activity with a seismic station located on northern Ellesmere Island. The influence of wind-ice-ocean interactions on microseism has been taken into account. We find the increase in microseism power over the last 32 years reflects the long-term loss of sea ice and increasing ocean-wave activity in the Arctic Ocean likely associated with climate change. We further assess model performance to determine a representative region over which sea-ice concentration and ocean-wave activity most directly influence the microseism power. The seismological methods developed here suggest that there is the potential to augment or refine observations of sea-ice conditions obtained from satellites and from in-situ observations. Seismological methods may thus help determine properties such as sea-ice thickness, which are less amenable to conventional observations, under a changing climate, particularly in remote areas like the High Arctic.
{"title":"Tracking Multiyear Sea-Ice Variation in the Arctic Ocean Over Decades With Microseism","authors":"Jui-Chun Freya Chen, Sunyoung Park, Douglas R. MacAyeal","doi":"10.1029/2024gl111159","DOIUrl":"https://doi.org/10.1029/2024gl111159","url":null,"abstract":"We construct a linear model of microseism power as a function of sea-ice concentration and ocean-wave activity with a seismic station located on northern Ellesmere Island. The influence of wind-ice-ocean interactions on microseism has been taken into account. We find the increase in microseism power over the last 32 years reflects the long-term loss of sea ice and increasing ocean-wave activity in the Arctic Ocean likely associated with climate change. We further assess model performance to determine a representative region over which sea-ice concentration and ocean-wave activity most directly influence the microseism power. The seismological methods developed here suggest that there is the potential to augment or refine observations of sea-ice conditions obtained from satellites and from <i>in-situ</i> observations. Seismological methods may thus help determine properties such as sea-ice thickness, which are less amenable to conventional observations, under a changing climate, particularly in remote areas like the High Arctic.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"49 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142962718","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}
Magnetic nulls are traditionally suggested as main points where energy dissipation occurs during reconnection. Such nulls have been widely observed in the diffusion region of standard reconnection following a two-fluid picture, but have never been investigated in the thin current sheet of electron-only reconnection. Recently, an electron-only reconnection event was observed by the Magnetospheric Multiscale (MMS) mission in Earth's magnetosheath. The small separation of MMS spacecraft (∼7 km) provides a good opportunity to examine whether magnetic nulls exist in electron-only reconnection. By utilizing the First-Order Taylor Expansion method, we find a radial null in this event. Moreover, such nulls degenerate into X-type nulls inside a reconnecting current sheet, suggesting that it's quasi 2D structure. By reconstructing the topology of this null, we can also estimate the reconnection rate of this electron-only reconnection event and find it's time-varying, suggesting it's an unsteady process. Our results are useful to further understand the process of electron-only reconnection.
{"title":"Evidence of a Magnetic Null in Electron-Only Reconnection","authors":"A. H. Tian, Z. Wang, H. S. Fu, Z. Z. Guo","doi":"10.1029/2024gl113104","DOIUrl":"https://doi.org/10.1029/2024gl113104","url":null,"abstract":"Magnetic nulls are traditionally suggested as main points where energy dissipation occurs during reconnection. Such nulls have been widely observed in the diffusion region of standard reconnection following a two-fluid picture, but have never been investigated in the thin current sheet of electron-only reconnection. Recently, an electron-only reconnection event was observed by the Magnetospheric Multiscale (MMS) mission in Earth's magnetosheath. The small separation of MMS spacecraft (∼7 km) provides a good opportunity to examine whether magnetic nulls exist in electron-only reconnection. By utilizing the First-Order Taylor Expansion method, we find a radial null in this event. Moreover, such nulls degenerate into X-type nulls inside a reconnecting current sheet, suggesting that it's quasi 2D structure. By reconstructing the topology of this null, we can also estimate the reconnection rate of this electron-only reconnection event and find it's time-varying, suggesting it's an unsteady process. Our results are useful to further understand the process of electron-only reconnection.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"6 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142962768","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}
Zachary McGraw, Lorenzo M. Polvani, Blaž Gasparini, Emily K. Van de Koot, Aiko Voigt
Precipitation is expected to increase in a warmer global climate, yet how sensitive precipitation is to warming depends on poorly constrained cloud radiative processes. Clouds respond to surface warming in ways that alter the atmosphere's ability to radiatively cool and hence form precipitation. Here we examine the links between cloud responses to warming, atmospheric radiative fluxes, and hydrological sensitivity in AMIP6 simulations. The clearest impacts come from high clouds, which reduce atmospheric radiative cooling as they rise in altitude in response to surface warming. Using cloud locking, we demonstrate that high cloud radiative changes weaken Earth's hydrological sensitivity to surface warming. The total impact of cloud radiative effects on hydrological sensitivity is halved by interactions between cloud and clear-sky radiative effects, yet is sufficiently large to be a major source of uncertainty in hydrological sensitivity.
{"title":"The Cloud Radiative Response to Surface Warming Weakens Hydrological Sensitivity","authors":"Zachary McGraw, Lorenzo M. Polvani, Blaž Gasparini, Emily K. Van de Koot, Aiko Voigt","doi":"10.1029/2024gl112368","DOIUrl":"https://doi.org/10.1029/2024gl112368","url":null,"abstract":"Precipitation is expected to increase in a warmer global climate, yet how sensitive precipitation is to warming depends on poorly constrained cloud radiative processes. Clouds respond to surface warming in ways that alter the atmosphere's ability to radiatively cool and hence form precipitation. Here we examine the links between cloud responses to warming, atmospheric radiative fluxes, and hydrological sensitivity in AMIP6 simulations. The clearest impacts come from high clouds, which reduce atmospheric radiative cooling as they rise in altitude in response to surface warming. Using cloud locking, we demonstrate that high cloud radiative changes weaken Earth's hydrological sensitivity to surface warming. The total impact of cloud radiative effects on hydrological sensitivity is halved by interactions between cloud and clear-sky radiative effects, yet is sufficiently large to be a major source of uncertainty in hydrological sensitivity.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"8 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142962730","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}
K. Jiang, S. Y. Huang, Q. M. Lu, Z. G. Yuan, Q. Y. Xiong
The electromagnetic electron Kelvin-Helmholtz instability (EM EKHI) and its impact on the dynamics inside a flux rope (FR) is investigated through observations from the Magnetospheric Multiscale mission. The convection term dominated electric field drives E × B drift in the FR, which supports a strong electron shear flow. The electron shear flow is unstable to the EM EKHI, which results in an electron velocity vortex and many current filaments in the FR. In one of the current filaments, ion and electron demagnetization and strong energy conversion are observed. The continuous radial nulls and obvious reconstructed X-line topology indicate that magnetic reconnection may occur in this current filament.
{"title":"Observations of the Electromagnetic Electron Kelvin-Helmholtz Instability and Its Impact on the Dynamics Inside a Flux Rope","authors":"K. Jiang, S. Y. Huang, Q. M. Lu, Z. G. Yuan, Q. Y. Xiong","doi":"10.1029/2024gl111450","DOIUrl":"https://doi.org/10.1029/2024gl111450","url":null,"abstract":"The electromagnetic electron Kelvin-Helmholtz instability (EM EKHI) and its impact on the dynamics inside a flux rope (FR) is investigated through observations from the Magnetospheric Multiscale mission. The convection term dominated electric field drives <b><i>E</i></b> × <b><i>B</i></b> drift in the FR, which supports a strong electron shear flow. The electron shear flow is unstable to the EM EKHI, which results in an electron velocity vortex and many current filaments in the FR. In one of the current filaments, ion and electron demagnetization and strong energy conversion are observed. The continuous radial nulls and obvious reconstructed X-line topology indicate that magnetic reconnection may occur in this current filament.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"5 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937790","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}
Yueya Wang, Haobo Li, Xiaoming Shi, Jimmy C. H. Fung
Improving typhoon precipitation forecast with convection-permitting models remains challenging. This study investigates the influence of cumulus parameterizations and turbulence models, including the Reconstruction and Nonlinear Anisotropy (RNA) turbulence scheme, on precipitation prediction in multiple typhoon cases. Incorporating the cumulus and RNA schemes increases domain-averaged precipitation, improves recall scores, and lowers relative error across various precipitation thresholds, which is substantial in three out of four studied typhoon cases. Applying appropriate cumulus parameterization schemes alone also contributes to enhancing heavy precipitation forecasts. In Typhoon Hato, the RNA and Grell-3 schemes demonstrated a doubled recall rate for extreme rainfall compared to simulations without any cumulus scheme. The improved forecasting ability is attributed to the RNA's capacity to model dissipation and backscatter. The RNA scheme can dynamically reinforce typhoon circulation with upgradient momentum transport in the lower troposphere and enhance the buoyancy by favorable heat flux distribution, which is conducive to developing heavy precipitation.
{"title":"Assessing the Impact of Cumulus Convection and Turbulence Parameterizations on Typhoon Precipitation Forecast","authors":"Yueya Wang, Haobo Li, Xiaoming Shi, Jimmy C. H. Fung","doi":"10.1029/2024gl112075","DOIUrl":"https://doi.org/10.1029/2024gl112075","url":null,"abstract":"Improving typhoon precipitation forecast with convection-permitting models remains challenging. This study investigates the influence of cumulus parameterizations and turbulence models, including the Reconstruction and Nonlinear Anisotropy (RNA) turbulence scheme, on precipitation prediction in multiple typhoon cases. Incorporating the cumulus and RNA schemes increases domain-averaged precipitation, improves recall scores, and lowers relative error across various precipitation thresholds, which is substantial in three out of four studied typhoon cases. Applying appropriate cumulus parameterization schemes alone also contributes to enhancing heavy precipitation forecasts. In Typhoon Hato, the RNA and Grell-3 schemes demonstrated a doubled recall rate for extreme rainfall compared to simulations without any cumulus scheme. The improved forecasting ability is attributed to the RNA's capacity to model dissipation and backscatter. The RNA scheme can dynamically reinforce typhoon circulation with upgradient momentum transport in the lower troposphere and enhance the buoyancy by favorable heat flux distribution, which is conducive to developing heavy precipitation.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"3 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937792","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}
S. Teng, Dedong Wang, Alexander Y. Drozdov, Yuri Y. Shprits, Zeyin Wu, Y. X. Hao, Z. Yao, J. Zhang
Investigations into quasiperiodic (QP) whistler mode emissions within Saturn's magnetosphere have uncovered distinctive characteristics of these emissions, which display a nearly periodic rising tone structure in the wave spectrogram, characterized by modulation periods of several minutes. These QP emissions are predominantly observed at low L-shells around 5 and near the magnetic equator. Utilizing a quasi-linear analysis framework, we evaluate the effects of these waves on the dynamics of energetic electrons. Our analysis suggests that these QP emissions can efficiently cause the loss of electrons within the energy range from 10 to 60 keV over a timescale of tens of minutes. By incorporating these findings into Fokker-Planck simulations, we find minimal acceleration effects. This study is the first to examine QP emissions and their implications for energetic electron dynamics in Saturn's magnetosphere, highlighting their potentially significant contribution to the magnetospheric processes and dynamics.
{"title":"Quasi-Periodic Emissions in Saturn's Magnetosphere and Their Effects on Electrons","authors":"S. Teng, Dedong Wang, Alexander Y. Drozdov, Yuri Y. Shprits, Zeyin Wu, Y. X. Hao, Z. Yao, J. Zhang","doi":"10.1029/2024gl112061","DOIUrl":"https://doi.org/10.1029/2024gl112061","url":null,"abstract":"Investigations into quasiperiodic (QP) whistler mode emissions within Saturn's magnetosphere have uncovered distinctive characteristics of these emissions, which display a nearly periodic rising tone structure in the wave spectrogram, characterized by modulation periods of several minutes. These QP emissions are predominantly observed at low L-shells around 5 and near the magnetic equator. Utilizing a quasi-linear analysis framework, we evaluate the effects of these waves on the dynamics of energetic electrons. Our analysis suggests that these QP emissions can efficiently cause the loss of electrons within the energy range from 10 to 60 keV over a timescale of tens of minutes. By incorporating these findings into Fokker-Planck simulations, we find minimal acceleration effects. This study is the first to examine QP emissions and their implications for energetic electron dynamics in Saturn's magnetosphere, highlighting their potentially significant contribution to the magnetospheric processes and dynamics.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"19 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937787","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}
Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) presented a catalog of Io hot spots based on JIRAM M-band images acquired in Juno orbits 10 to 33. They identified 242 hot spots, including 23 not previously reported in other catalogs, observing a higher hot spot number density in the northern polar region. Davies (2024) disputes location and counting of part of these hot spots, attributing the differences between the Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) results and those obtained by Davies et al. (2024, https://doi.org/10.1038/s41550-023-02123-5) to a misregistration of the JIRAM images. Here we reply to Davies (2024) showing that discrepancies in the results are due to the different methodologies, assumptions, and goals considered in the two works.
{"title":"Reply to Comment by A. G. Davies on “Io Hot Spot Distribution Detected by Juno/JIRAM”","authors":"F. Zambon, A. Mura, F. Tosi","doi":"10.1029/2024gl112921","DOIUrl":"https://doi.org/10.1029/2024gl112921","url":null,"abstract":"Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) presented a catalog of Io hot spots based on JIRAM M-band images acquired in Juno orbits 10 to 33. They identified 242 hot spots, including 23 not previously reported in other catalogs, observing a higher hot spot number density in the northern polar region. Davies (2024) disputes location and counting of part of these hot spots, attributing the differences between the Zambon et al. (2023, https://doi.org/10.1029/2022gl100597) results and those obtained by Davies et al. (2024, https://doi.org/10.1038/s41550-023-02123-5) to a misregistration of the JIRAM images. Here we reply to Davies (2024) showing that discrepancies in the results are due to the different methodologies, assumptions, and goals considered in the two works.","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"35 1","pages":""},"PeriodicalIF":5.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937788","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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