Journal of Geophysical Research: Atmospheres最新文献

{"title":"Direct Observation of Quasi-Monochromatic Gravity Wave Packets Associated With the Polar Night Jet Using a Doppler-Rayleigh Lidar","authors":"Robin Wing,&nbsp;Irina Strelnikova,&nbsp;Andreas Dörnbrack,&nbsp;Michael Gerding,&nbsp;Eframir Franco-Diaz,&nbsp;Laura Holt,&nbsp;Mohamed Mossad,&nbsp;Gerd Baumgarten","doi":"10.1029/2025JD043707","DOIUrl":"https://doi.org/10.1029/2025JD043707","url":null,"abstract":"<p>An advanced hodograph technique was applied to extract quasi-monochromatic, linear gravity wave (GW) packets from simultaneous wind and temperature measurements made using a ground-based Doppler-Rayleigh-Mie-Raman lidar located in Kühlungsborn (54°N, 12°E). During the night of 11–12 February 2022, the stratospheric polar vortex was slightly elongated toward Central Europe. The polar night jet's (PNJ) core was located nearly above the lidar. This unique meteorological situation allowed the measurement of horizontal wind and temperature in a stratospheric high-wind speed regime. GW propagation in the strong vertical gradient of the horizontal winds associated with the PNJ was observed. In addition, the subsequent reduction in the number of upward and downward propagating GWs in the strong winds of the PNJ was demonstrated. A pair of upward and downward propagating GWs at the top and bottom edge of the PNJ's core could be the result of shear excitation in the PNJ. A statistical analysis of intrinsic GW parameters is provided for all resolved linear GWs. Approximately 35% of the resolved GWs propagate downward, and there is stronger filtering of the downward waves compared to the upward waves in the PNJ core. ECMWF-IFS horizontal winds and temperatures had a lower variability than the lidar measurement and a poorer overall agreement above 50 km. Stratospheric temperatures in ECMWF show a cool bias of greater than 2 K.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043707","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144663816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"A Closed Bay-Breeze Circulation and Its Lifecycle From TRACER With a New Orienteering Tape Recorder Diagram","authors":"Min Deng,&nbsp;Michael P. Jensen,&nbsp;Scott E. Giangrande,&nbsp;Karen Johnson,&nbsp;Dié Wang,&nbsp;Yufei Chu,&nbsp;Tamanna Subba,&nbsp;Jean Carlos Peña,&nbsp;Paul Walter,&nbsp;James Flynn,&nbsp;Travis Griggs","doi":"10.1029/2024JD043187","DOIUrl":"https://doi.org/10.1029/2024JD043187","url":null,"abstract":"<p>A closed bay-breeze circulation (BBC) followed by a gulf-breeze front (GBF) was observed on 10 September 2022 during the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) TRACER campaign. Using high-resolution X-band Scanning Cloud Radar (XSACR) and a newly developed orienteering tape recorder diagram, the study analyzed radar reflectivity and Doppler velocity to identify anomalies and track the evolution of these circulations. The BBC, a mesoscale system approximately 30-km long, 30-km wide, and 2-km deep, formed from enhanced horizontal convective rolls along the Galveston Bay coast, progressing northwestward under a 6 m s⁻¹ onshore flow anomaly and reaching 1.5 km depth with return flow aloft. The inland penetration speed was 2 m s⁻¹, driven by an observed 6–9 K land-water temperature contrast. The GBF, coupled to the BBC, intensified with additional southerly flow, penetrating further inland after the BBC collapsed. Passing over the TRACER field site, both fronts significantly impacted boundary layer thermodynamics, dynamics, and aerosol concentration. The BBC event exhibited four lifecycle stages—formation, development, maturation, and dissipation—driven by solar heating, wind field rotation, and interactions with convective eddies and the GBF. This study provides insights into the inland evolution of coastal breeze circulations and their interactions with environmental processes.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD043187","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144663814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Strengthening Atmospheric Greenhouse Effect at the Arctic North Slope of Alaska Site Evidenced by Long-Term Records of the Downwelling Longwave Radiance Spectrum","authors":"B. Riot-Bretêcher,&nbsp;Y. Huang,&nbsp;L. Liu,&nbsp;J. Gero","doi":"10.1029/2025JD043680","DOIUrl":"https://doi.org/10.1029/2025JD043680","url":null,"abstract":"<p>Arctic amplification, the accelerated warming of the Arctic compared to lower latitude, remains poorly understood, particularly regarding the role of clouds. In this study, we analyze 26 years of downwelling longwave radiation (DLR) measurements from an Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) at the US Department of Energy's North Slope of Alaska site. Our analysis reveals a pan-spectral increase in DLR under all sky conditions, primarily driven by an enhanced greenhouse effect from thick/low clouds and greenhouse gases. We find that the observed DLR trends are primarily driven by radiance changes within individual sky conditions, rather than changes in cloud fraction, suggesting fundamental shifts in atmospheric emissivity and/or temperature. Comparative analysis between the Southern Great Plains (mid-latitude) and North Slope of Alaska (high-latitude) sites demonstrates that clouds impact the longwave surface energy balance differently between the two locations. In the Arctic, the pan-spectral increase in DLR trend dampens out the radiative cooling of the warming surface, contributing significantly to Arctic amplification. Consistent positive trends are found in the far-infrared, a spectral region sensitive to even small changes of the dry and cold Arctic's atmosphere and of significant interest in the current warming context. Additionally, we observe a relatively weaker DLR trend in the ozone absorption band under every sky condition, indicating a tropospheric ozone radiative forcing in the Arctic climate.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043680","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144663815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"A European Hail and Lightning Climatology From an 11-Year Kilometer-Scale Regional Climate Simulation","authors":"R. Cui,&nbsp;I. Thurnherr,&nbsp;P. Velasquez,&nbsp;K. P. Brennan,&nbsp;M. Leclair,&nbsp;A. Mazzoleni,&nbsp;T. Schmid,&nbsp;H. Wernli,&nbsp;C. Schär","doi":"10.1029/2024JD042828","DOIUrl":"https://doi.org/10.1029/2024JD042828","url":null,"abstract":"<p>Hail and lightning, associated with severe convective storms, can cause extensive damage to infrastructure, agriculture, and ecosystems. Because of the small scale of these storms and the complexity of the involved processes, observing and modeling convective storms is challenging. The potential of online diagnostics in convection-permitting models to simulate hail and lightning, especially over climatic time scales and extended regions, has not yet been fully exploited. To address this gap, we present a European-wide hail and lightning climatology (2011–2021) using the Consortium for Small Scale Modeling (COSMO) regional climate model with a horizontal grid spacing of 2.2 km, coupled with a hail growth model (HAILCAST) and the lightning potential index (LPI) diagnostics. We further developed a new European-wide hail product based on the Operational Program for the Exchange of Weather Radar Information (OPERA) composite. Model validation against observations demonstrates an overall good performance in simulating hail and lightning on spatial, seasonal, and diurnal scales. The highest hail frequencies occur during summer along the slopes of high mountain ridges, such as the Alps, Pyrenees, and the Carpathians, aligning with observed lightning hotspots in Europe. In autumn, hail and lightning occur predominantly over the Mediterranean and along the Adriatic coast. Severe hail events with a maximum hail diameter larger than 20 mm mainly occur in the Po Valley, western Spain, and Eastern Europe. This 11-year simulation provides a European-wide data set of severe convective storms and their properties, serving as a basis for further studies of convective events and their impacts.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD042828","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Decadal Variation of the South Asian High: Roles of the Interdecadal Pacific Oscillation and Anthropogenic Aerosols","authors":"Dapeng Zhang,&nbsp;Ni Huang,&nbsp;Peilin Li,&nbsp;Wenxin Xie,&nbsp;Botao Zhou,&nbsp;Peilong Yu,&nbsp;Huijun Wang","doi":"10.1029/2024JD042927","DOIUrl":"https://doi.org/10.1029/2024JD042927","url":null,"abstract":"<p>The South Asian high (SAH) has experienced notable decadal variation over past decades that has exerted substantial influence on the summer climate of the Northern Hemisphere. However, the mechanisms that influence the decadal change of the SAH remain unclear. Results based on reanalysis data and climate model experiments indicate that with increased emission of anthropogenic aerosols (AAs), the contribution of external forcing to the SAH strengthened in the late 1960s and exceeded its internal variability. The transition of the Interdecadal Pacific oscillation (IPO) from the cold to the warm phase and increased AAs jointly promoted decadal decline in the SAH in the late 1970s through air-sea processes and radiation effects, respectively. Notably, the transition of the IPO from the positive to the negative phase around 2000 tended to enhance the SAH. However, this was offset by the larger contribution from high emission of AAs, which promoted a continuously weak SAH. The contribution of AAs might still dominate the SAH changes at the beginning of this century. However, as the emission of AAs declines in the future, the influence of AAs on the SAH might weaken. The IPO is expected to play the dominant role in the decadal variation of the SAH from the 2040s under the low-emission Shared Socioeconomic Pathway (SSP1-2.6).</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impacts of Aerosol Scattering and Absorption on FY-4B Geostationary Interferometric Infrared Sounder (GIIRS) Observations","authors":"Weiyi Peng,&nbsp;Fuzhong Weng","doi":"10.1029/2024JD042657","DOIUrl":"https://doi.org/10.1029/2024JD042657","url":null,"abstract":"<p>In the past, impacts of aerosol scattering and absorption were often neglected in simulating the hyperspectral infrared sounder (HIS) measurements and can lead to larger observation-minus-background (OMB) errors in satellite data assimilation. To quantify the aerosol effects on OMB, we utilized the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) data to calculate the mass densities of different aerosol types (dust, organics, sulfates, and carbonates). These parameters are then incorporated into the advanced radiative transfer modeling system (ARMS) to simulate the brightness temperatures (BT) and Jacobians for the longwave channels of the FengYun-4B (FY-4B)/GIIRS. For a sandstorm event on 9 April 2023, simulation results indicate a positive correlation between OMB and aerosol optical parameters (e.g., aerosol mass density, particle size, and aerosol optical depth). The inclusion of aerosols generally results in smaller OMBs. In particular, the bias in GIIRS is reduced by 1.11 K when the dust aerosols are included. In general, both <i>JT</i> and <i>JQ</i> are sensitive to the changes in dust aerosol. Simulated BT sensitivity is most responsive to the temperature of aerosol and particulate layers. Moreover, accounting for the effects of dust aerosols in the one-dimensional variational retrieval (1D-VAR) system significantly enhanced the accuracy of temperature profile retrievals in dust-affected regions. Compared to retrievals that did not consider aerosol effects and the GIIRS Level-2 product, the temperature retrieval results were improved, especially in aerosol peak layers. The root mean square error (RMSE) improved by about 0.01 K, and the mean bias improved by about 0.7 K.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of Microphysical Parameterizations on Satellite All-Sky Infrared Data Assimilation and Practical Predictability of Hurricane Harvey (2017)","authors":"J. Rendon,&nbsp;Y. Zhang","doi":"10.1029/2024JD042697","DOIUrl":"https://doi.org/10.1029/2024JD042697","url":null,"abstract":"<p>Satellites provide the majority of observations of tropical cyclones (TCs) when they are over the open ocean. These observations are under-utilized in operational global and regional forecasting models as most of the cloudy and precipitation-affected observations are discarded. Recent works have shown that assimilating all-sky infrared (IR) radiances from geostationary satellites improves TC track, intensity, and rainfall forecasts. This study examines how two different cloud microphysical parametrization schemes impact all-sky IR radiance assimilation and subsequent forecasts of Hurricane Harvey. Because model hydrometeor fields that are used to simulate IR radiances are strongly constrained by the model microphysics scheme, Harvey's dynamic and thermodynamic structure become very different when changing the microphysics schemes, which also leads to changes in subsequent intensity forecasts. Sensitivity forecasts suggest that intensity forecast errors in this study are primarily controlled by uncertainties in initial conditions, which are influenced by microphysics schemes as they simulate model priors differently when assimilating all-sky IR radiance. On the other hand, the microphysics schemes used during the free forecasts generally have a smaller impact on Harvey's intensity forecast errors.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD042697","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Atmospheric Response to Antarctic Coastal Polynyas","authors":"M. Noel,&nbsp;S. Masson,&nbsp;C. Rousset","doi":"10.1029/2025JD043319","DOIUrl":"https://doi.org/10.1029/2025JD043319","url":null,"abstract":"<p>The lack of sea ice in Antarctic coastal polynyas enables strong ocean-to-atmosphere heat fluxes and intense sea-ice production. Although these features are primarily driven by intense offshore winds, their impact on local atmospheric conditions remains poorly understood. This study employs a high-resolution polar Weather Research and Forecasting model configuration over the Prydz Bay region, East Antarctica, home to two major coastal polynyas: Cape Darnley and Mackenzie Bay polynyas. Sensitivity experiments over three winters (2014–2016) comparing simulations with and without polynyas reveal a marked and spatially confined atmospheric response. Polynya openings induce substantial surface heat release (up to 700 W m⁻²), warming near-surface air by over 5 K and triggering convection and clouds. This results in a thickening of the atmospheric boundary layer and the development of stronger surface winds (up to 4 m s⁻¹) that converge toward a low-pressure anomaly. A particular emphasis is placed on the mechanisms controlling wind anomalies, using a dedicated wind tendency analysis. This diagnosis highlights that the processes involved depend on location and altitude within the polynya region and involve a balance between vertical mixing, horizontal advection, and pressure gradient forces—vertical mixing acting as the initiating factor. This study provides a novel modeling framework used to isolate the atmospheric response to coastal polynyas, overcoming limitations of previous studies and coarse-resolution models. It offers new insights into the role of polynyas in modulating regional climate and improving understanding of the processes driving their dynamics.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043319","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Turbulence of Tropical Cyclones: From Peristrophic to Zonostrophic","authors":"Boris Galperin,&nbsp;Alexander K. Nickerson,&nbsp;Gregory P. King,&nbsp;Jun A. Zhang","doi":"10.1029/2024JD042733","DOIUrl":"https://doi.org/10.1029/2024JD042733","url":null,"abstract":"&lt;p&gt;Cyclostrophic rotation in the core region of tropical cyclones (TCs) imprints a distinct signature upon their turbulence structure. Its intensity is characterized by the radius of maximum wind, &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;R&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;w&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${R}_{mw}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and the azimuthal wind velocity at that radius, &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;U&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mi&gt;x&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${U}_{max}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. The corresponding cyclostrophic Coriolis parameter, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mover&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;mo&gt;ˆ&lt;/mo&gt;\u0000 &lt;/mover&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;U&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mi&gt;x&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $widehat{f}=2{U}_{max}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;/&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;R&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;w&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${R}_{mw}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, far exceeds its planetary counterpart, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $f$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, for all storms; its impact increases with storm intensity. The vortex can be thought of as a system undergoing a superposition of planetary and cyclostrophic rotations represented by the effective Coriolis parameter, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mover&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mover&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mrow&gt;\u0000 ","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD042733","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Making Sense of Bifurcation Diagrams: A New Framework to Understand the Roles of Clouds and Bare Sea Ice for Waterbelt States","authors":"Johannes Hörner,&nbsp;Aiko Voigt","doi":"10.1029/2025JD043568","DOIUrl":"https://doi.org/10.1029/2025JD043568","url":null,"abstract":"<p>Earth has experienced several pan-glaciations in its history, often interpreted as hard Snowball Earth periods with global ice cover. Alternatively, waterbelt states with a narrow equatorial strip of ice-free ocean provide a compelling explanation for the survival of life during these extreme glaciations. In this study, we establish a framework to quantify three atmospheric factors that influence waterbelt states: the spatial extent of bare dark sea ice set by the pattern of surface precipitation and evaporation, cloud masking of the ice-albedo feedback, and cloud shortwave feedback. We first explore these factors in the Budyko-Sellers energy balance model, and then investigate them in simulations with three versions of the ICON global climate model. This allows us to relate differences in the waterbelt states between ICON versions to the three factors. A broader Hadley circulation shifts the boundary between snow-covered and bare sea ice poleward, leading to waterbelt states whose ice lines are at higher latitudes. Cloud masking always works in favor of stable waterbelt states by weakening the ice-albedo feedback. The role of the cloud shortwave feedback, in contrast, depends on the ICON version: in one version, increasing cloud condensate over the low-latitude open ocean destabilizes waterbelt states and creates an additional small hysteresis. In the other two versions, the cloud shortwave feedback is stabilizing. While our study does not answer which of the model versions is most realistic, it provides a quantitative framework for understanding the atmospheric mechanisms that govern the existence and hysteresis of waterbelt states.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 14","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043568","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144647685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}