Journal of Geophysical Research: Atmospheres最新文献

{"title":"Marine Volatile Organic Compounds Promote the Chloride Depletion in Sea Salt Aerosols","authors":"Aijing Song,&nbsp;Kun Li,&nbsp;Zhaomin Yang,&nbsp;Narcisse Tsona Tchinda,&nbsp;Lin Du","doi":"10.1029/2025JD043495","DOIUrl":"https://doi.org/10.1029/2025JD043495","url":null,"abstract":"<p>Despite chloride depletion of sea salt aerosols (SSA) is one of the most important phenomena in the coastal atmosphere with significant impacts on air quality and human health, the factors influencing this depletion remain unclear. We analyzed the mole ratio of Cl⁻/Na⁺ to evaluate the effects of coastal atmospheric enriched SO₂ and some marine volatile organic compounds (namely isoprene and dimethyl sulfide (DMS)) on chloride depletion by laboratory experiments. Using ultrahigh performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometer (UPLC/ESI-HR-Q-TOF-MS), the formation of organic chlorinated compounds during chloride depletion of SSA was identified and analyzed to verify marine sources of Cl radicals. Our results show that chloride depletion increased (1.1%–33.7%) with increasing SO₂ concentration (0–400 ppb) due to the production of inorganic acids. This chloride depletion was also enhanced with the addition of isoprene and DMS, with DMS having the greatest effect. In the presence of DMS, the mole ratio of Cl⁻/Na⁺ was 0.721 at an SO₂ concentration of 200 ppb, causing greater chloride depletion than isoprene (0.820). Many organic chlorinated compounds were identified, with CHClSO compounds being identified in experiments in the presence of SO₂. The mass spectrometry results confirm that the activation of chloride ions, another important factor affecting chloride depletion, is essential for the formation of organic chlorinated compounds. These results have implications for model predictions of chloride depletion in polluted coastal areas.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144336055","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":"The First Firn Core From the Cordillera Darwin Icefield: Implications for Future Ice Core Research","authors":"Dieter R. Tetzner,&nbsp;Elizabeth R. Thomas,&nbsp;Claire S. Allen,&nbsp;Robert D. McCulloch,&nbsp;Bianca B. Perren,&nbsp;Amy McGuire,&nbsp;Delia Segato,&nbsp;Franziska Temme,&nbsp;Johannes J. Fürst,&nbsp;Dorothea Moser,&nbsp;Francisco Fernandoy,&nbsp;Camilo Rada,&nbsp;Jack Humby,&nbsp;Shaun Miller","doi":"10.1029/2024JD043124","DOIUrl":"https://doi.org/10.1029/2024JD043124","url":null,"abstract":"<p>The Southern Hemisphere westerly winds (SHWWs) (45–65°S) are important regulators of the Southern Hemisphere climate. The scarcity of observational records at the core of the wind belt hinders our understanding of the environmental impact and long-term variability of the westerly winds. The Cordillera Darwin Icefield (CDI) (54–55°S) is favorably located to capture environmental changes at the current core of the SHWW belt. Here, we present chemical and microparticle records from the first firn core from the CDI. We evaluate regional climate reanalysis data using in situ automatic weather station observations and apply a downscaling approach to study regional-to-local environmental conditions at the firn core site. We use these records to assess the preservation of local-to-regional environmental information in the firn. Our CDI firn core records present minor post-depositional disruptions, preserving the original seasonality of locally sourced impurities. Local surface air temperature and melt estimations suggest the icefield has been progressively exposed to surface melt conditions, but not enough to produce significant melt at the firn core site. Air mass trajectories demonstrate air parcels are directly transported from local marine and terrestrial environments, establishing a route for the transport and deposition of chemical compounds and aerosols to the firn core site. These results highlight the potential of high elevation sites (&gt;2,000 m a.s.l) in the CDI to hold valuable paleoenvironmental records directly from the core of the SHWW belt, records which are currently threatened by increasing surface air temperatures.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD043124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144336105","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 Excitation of Length of Day Inferred From 21st Century Climate Projections","authors":"Sigrid Böhm,&nbsp;David Salstein","doi":"10.1029/2025JD043646","DOIUrl":"https://doi.org/10.1029/2025JD043646","url":null,"abstract":"<p>On seasonal timescales, atmospheric angular momentum, mainly constituted by wind but also pressure effects, is known as the most important driver of Earth rotation variations reflected in those of the length of day. However, in connection with long-term climatic changes, we additionally anticipate secular trends resulting from shifts or changes in the intensity of atmospheric circulation. We investigate potential atmospheric transitions and their consequences for length of day using historical and 21st century simulations of a CMIP6 multimodel ensemble. The future projections used rely on five scenarios of differing greenhouse gas emission strengths and societal development. In each scenario, the resulting mean in the atmospheric angular momentum ensemble trajectory aligns with that of the projected surface temperature. The two pathways characterized by sustainability do not indicate significant centennial trends in atmospheric angular momentum and the respective length of day excitation. The scenarios with medium, high, and very high-emission intensity project gradual increases in atmospheric angular momentum, dominated by strengthening subtropical westerly jet streams. For the most intense scenario, this would correspond to an atmosphere-induced slowdown of the Earth's rotation, with a 0.43 ms cy⁻¹ increase in length of day, which amounts to about one-fifth of the slowdown due to the effect of tidal friction. In contrast, we identify no clear trend regarding the long-term change in the amplitude of the annual oscillation. Our results emphasize that climate change can affect Earth's rotation rate or, equivalently, the length of day through secular variations in atmospheric angular momentum.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043646","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323453","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":"Dual-Polarization Radar Data Assimilation Based on Hydrometeor Classification and Its Impact on Severe Weather Prediction","authors":"Haiqin Chen,&nbsp;Tao Sun,&nbsp;Kun Zhao,&nbsp;Yaodeng Chen,&nbsp;Ang Zhou,&nbsp;Chong-Chi Tong","doi":"10.1029/2024JD042797","DOIUrl":"https://doi.org/10.1029/2024JD042797","url":null,"abstract":"<p>The indirect radar reflectivity assimilation method, which assimilates retrieved hydrometeors from radar reflectivity data, is simple and efficient in severe weather forecasting applications. However, it suffers from retrieval errors due to the uncertainties in discerning multiple hydrometeor types based solely on reflectivity observations. To mitigate these inaccuracies, dual-polarization radar data are incorporated into the background-dependent indirect reflectivity assimilation method in this study. First, the contribution of multiple hydrometeor species to the whole reflectivity is estimated using the observed reflectivity and background microphysical information; then, the hydrometeor classification algorithm (HCA) product from dual-polarization radar observations is introduced to correct the dominant hydrometeor type if in error; and finally, the contribution factors are adjusted and used to retrieve multiple hydrometeor species from reflectivity data. Through a single squall line case, it is demonstrated that the incorporation of the HCA product from dual-polarization radar data leads to more reasonable hydrometeor identification, with more supercooled rainwater above the melting layer and more graupel at low levels, thereby refining the hydrometeor analysis. With the 15-min rapid update cycling configuration, the changes in the analysis field enable more cold rain processes, resulting in more intense latent heat release at higher levels and stronger cooling near the surface in the forecast. This in turn strengthens updraft motion and cold pools in the convective regions, thereby improving the reflectivity and precipitation forecasts. Four cases' quantitative evaluations of the 0–3-hr reflectivity and precipitation forecasts further validate the effectiveness of incorporating dual-polarization radar data in the assimilation process.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323552","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":"Precipitation of Weak Tropical Cyclone Mulan (2022): Sensitivity to Cumulus and Microphysics Parameterization Schemes","authors":"Jingyao Wang,&nbsp;Entao Yu,&nbsp;Jiehua Ma,&nbsp;Jun Wang,&nbsp;Dong Chen,&nbsp;Huijun Wang","doi":"10.1029/2024JD043011","DOIUrl":"https://doi.org/10.1029/2024JD043011","url":null,"abstract":"<p>Previous studies on precipitation caused by tropical cyclones (TCs) have largely focused on strong TCs while systematic research on weak systems remains limited. This study utilized the high-resolution (3 km) weather research and forecasting (WRF) model to investigate the sensitivity of heavy precipitation generated by weak TC Mulan (2022) over the South China Sea to cumulus and microphysics parameterization schemes. Six cumulus parameterizations and five microphysics schemes were configured with simulations validated against gauge observations. Results indicated that cumulus parameterizations had a significant influence on precipitation simulation while the microphysics schemes exhibited a relatively minor impact in this case. The combination of the New Tiedtke cumulus scheme and the WRF Single-Moment 6-class (WSM6) microphysics scheme yielded the best simulation of precipitation compared with the observations. Further investigation revealed that cumulus parameterizations modulated simulated large-scale circulation, moisture transportation, and vertical velocities. The New Tiedtke scheme reproduced a more northward TC track and an intensified southeast jet along the coast of Southeast China, aligning with the observed heavy precipitation zones and providing favorable dynamic and thermodynamic conditions for precipitation. In contrast, the Betts-Miller-Janjić (BMJ) scheme resolved cloud-environment interactions inadequately, resulting in excessive convection and latent heating, which amplified cumulus precipitation compared to the New Tiedtke scheme. Among the cumulus parameterization schemes, the Kain-Fritsch (KF) and BMJ schemes underperformed due to their overestimation of deep convection while the New Tiedtke and Multi-scale KF (MSKF) schemes showed better performance. This study provides a valuable reference for further precipitation prediction research in the study region and adjacent areas.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323455","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":"On the Potential Role of Lubrication Oil Particles in Contrail Formation for Kerosene and Hydrogen Combustion","authors":"Josef Zink,&nbsp;Simon Unterstrasser,&nbsp;Tina Jurkat-Witschas","doi":"10.1029/2025JD043487","DOIUrl":"https://doi.org/10.1029/2025JD043487","url":null,"abstract":"<p>The radiative forcing caused by contrail cirrus is nonlinearly influenced by the number of ice crystals formed in the exhaust plume behind an aircraft engine. This ice crystal number strongly depends on the properties (number, size, and solubility) of condensation nuclei in the plume available for droplet activation with subsequent freezing. In this ice crystal formation process, the relative importance of plume particles originating from lubrication oil is unclear. Therefore, we have extended the particle-based Lagrangian Cloud Module in the box model approach to simulate the formation of ice crystals on such oil particles. With this extended box model, we performed simulations for many different scenarios of emitted oil particle numbers and sizes. We examine the activation of these oil particles and investigate their competition with soot for kerosene combustion and with ambient aerosols for hydrogen combustion. Furthermore, we study the relative importance among weakly soluble/insoluble oil particles and well-soluble volatile particles from the combustion process. For present-day soot emissions, the number of ice crystals formed on oil particles may be masked by those formed on soot. However, these oil particles may be abundant enough to dominate ice crystal formation in soot-poor or hydrogen combustion scenarios. This may occur when a small amount of lubrication oil (on the order of a few milliliters per hour) evaporates in the hot exhaust plume and nucleates new particles with a size of a few nanometers during the subsequent plume cooling.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043487","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323551","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":"Enhancing Wildfire and Smoke Forecasting by Integrating Fire Observations: A Comparative Analysis of Methods for Integrating Infrared and Satellite Data Into a Coupled Fire-Atmosphere Model","authors":"Kathleen Clough,&nbsp;Angel Farguell,&nbsp;Jan Mandel,&nbsp;Kyle Hilburn,&nbsp;Adam Kochanski","doi":"10.1029/2024JD042561","DOIUrl":"https://doi.org/10.1029/2024JD042561","url":null,"abstract":"<p>Accurate forecasts of fire spread and smoke impacts using coupled fire-atmosphere models require advanced methods for fire initialization. This paper proposes and tests three different methods for integrating fire observations. The methods reconstruct the initial fire evolution needed for the atmosphere spin-up at the beginning of the simulation and identify actively burning fire regions. One method is based solely on IR perimeters, while the other two leverage IR perimeters and satellite detections. One uses only the most recent satellite data, while the other contextualized method uses two consecutive satellite detections to identify which sections of the fire perimeter experienced significant growth and which were inactive. This integration method addresses the problem of inaccurate identification of actively burning regions, thus correcting the previously seen overestimated growth in real-time forecasts. This problem is fundamental when forecasting multiday fire incidents, which benefit from updating the state of the fire at the beginning of each forecast. The methods were tested within the WRFx fire forecasting system. The entire real-time forecast for the 2021 Caldor Fire was rerun using the three methods and compared against observations. The analysis of the fire growth, as well as surface PM_2.5 concentrations and smoke heights, indicate that the contextual method utilizing both IR perimeters and satellite detections offers significant improvements when compared to the other methods for all variables analyzed, with the most considerable improvement in forecast skill seen in forecasts with 24–48 hr lead time.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331831","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":"Springtime UTLS Ozone Variability in East Asia: Insights From 16 Years of IASI Observations (2008–2023)","authors":"Chiyoung Kim,&nbsp;Joowan Kim,&nbsp;Jae-Heung Park,&nbsp;Ja-Ho Koo,&nbsp;Kyung-Hwan Kwak,&nbsp;Anne Boynard,&nbsp;Laura L. Pan,&nbsp;Cathy Clerbaux,&nbsp;Daniel Hurtmans,&nbsp;Pierre-François Coheur,&nbsp;Sang Seo Park","doi":"10.1029/2024JD043183","DOIUrl":"https://doi.org/10.1029/2024JD043183","url":null,"abstract":"<p>We investigated the springtime variability of ozone in the upper troposphere and lower stratosphere (UTLS) over East Asia using data from the Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop satellite series (Metop-A, Metop-B, and Metop-C), complemented with ozonesonde observations and MERRA-2 reanalysis data. The accuracy of the IASI ozone profiles was confirmed through validation against ozonesonde measurements, demonstrating their reliability for monitoring UTLS ozone dynamics. An empirical orthogonal function analysis revealed that the first principal component explained more than half of the variance in UTLS ozone during springtime, with strong positive correlations in regions influenced by the East Asian jet stream (EAJS). The analysis showed that the strengthening of the jet stream was associated with increased ozone concentrations, likely driven by enhanced baroclinic wave activity and stratospheric intrusion. Moreover, the intensification of the EAJS was associated with strengthening of the local Hadley Cells and the meridional temperature gradient over the upstream region even during springtime.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD043183","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144323454","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":"Multiscale Dynamical Processes Shaping a Mixing Line","authors":"Andreas Dörnbrack,&nbsp;Hans-Christoph Lachnitt,&nbsp;Peter Hoor,&nbsp;Paola Rodriguez Imazio","doi":"10.1029/2025JD043527","DOIUrl":"https://doi.org/10.1029/2025JD043527","url":null,"abstract":"<p>The paper discusses multiscale dynamical processes shaping a mixing line in the upper troposphere/lower stratosphere (UTLS). It focuses on aircraft observations above southern Scandinavia during a mountain wave event and how they can be analyzed based on dynamic variables and the trace gases <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>N</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{N}}_{2}$</annotation>\u0000 </semantics></math>O and CO. This study aims to identify the irreversible component of the stratosphere-troposphere exchange. It was shown that the overall shape of the mixing line is determined by the large-scale and mesoscale atmospheric conditions in the UTLS. Especially, the wide range of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Θ</mi>\u0000 </mrow>\u0000 <annotation> ${Theta }$</annotation>\u0000 </semantics></math> values along the flight tracks causes a compact, almost linear tracer-tracer relation between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>N</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{N}}_{2}$</annotation>\u0000 </semantics></math>O and CO. Only motion components with scales less than 4 km lead to the observed scatter around the mixing line. The anisotropic and patchy nature of the observed turbulence is responsible for this scatter in <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>N</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{N}}_{2}$</annotation>\u0000 </semantics></math>O and CO. The turbulence analysis reveals different scaling laws for the power spectra upstream, over the ridge and downstream of the mountains that lead to energy dissipation and irreversible mixing. The study suggests that turbulence dynamics may follow a cycle starting with 3D homogeneous isotropic turbulence upstream, transitioning to anisotropic turbulence over the ridge and further downstream. This transition is attributed to an interplay between turbulent eddies and internal gravity waves.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043527","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331977","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":"Instantaneous Radiative Effect of Surface Longwave Spectral Emissivity in a Snowball Earth Simulation","authors":"Daniel S. Zetterberg,&nbsp;Xianglei Huang,&nbsp;Johannes Hörner,&nbsp;Aiko Voigt,&nbsp;Xiuhong Chen","doi":"10.1029/2025JD043596","DOIUrl":"https://doi.org/10.1029/2025JD043596","url":null,"abstract":"<p>Spectrally dependent emission by the surface (i.e., surface spectral emissivity) is commonly ignored by current climate models. Surface spectral emissivity matters more in cold and dry environments than in hot and humid environments. Recent modeling studies confirmed that, for current climate simulations, this process affects the polar climate more than the extra-polar climate. As for the Snowball Earth, a period characterized by global polar-like conditions of extreme cold and low humidity, including surface spectral emissivity could alter the simulated global radiation budget. This, in turn, could affect the simulated climate of the Snowball Earth. Here, we use an aqua-planet slab-ocean simulation of Snowball Earth by the ICON model to perform offline radiative transfer calculations to quantify such impact on the outgoing longwave radiation (OLR). The offline radiative transfer model is used to compute the clear-sky OLR for two surfaces that would be present in the extremely cold simulation: ice and snow. Compared to the results with assumed blackbody surface, the global mean OLR decreases by 2.9 and 1.0 W m⁻² for ice and snow surfaces, respectively. The impact of surface spectral emissivity on the OLR is strongest at the equator and weakens toward the poles, presenting a noticeable meridional gradient. Effects of surface emissivity are also larger during the summer than the winter. The radiative effects of this often-neglected process would be small for a snow-covered globe but could be important for climate states with exposed ice, particularly Jormungand states, as well as simulations of other cold and dry climates.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 12","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043596","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144314950","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}