Atmospheric Chemistry and Physics最新文献

{"title":"Gravity waves as a mechanism of troposphere–stratosphere–mesosphere coupling during sudden stratospheric warming","authors":"Gordana Jovanovic","doi":"10.5194/egusphere-2024-1856","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1856","url":null,"abstract":"<strong>Abstract.</strong> The propagation of gravity waves (GW) and their role in the coupling of the troposphere–stratosphere–mesosphere atmospheric layers during sudden stratospheric warming (SSW) are studied. A standard set of hydrodynamic equations (HD) is used to derive the analytical dispersion equations and the GWs reflection coefficient. These equations are applied to the troposphere–stratosphere and stratosphere–mesosphere boundaries to analyze which part of the GWs spectra has the greatest chance of crossing them and affecting the dynamics of the upper atmosphere. We found that the GWreflection coefficient at the troposphere–stratosphere boundary increases significantly during SSW. This is not the case for the reflection coefficient at the stratosphere–mesosphere boundary when the reflection coefficient decreases compared to its value in the no–SSW case. The generation of GWs in the stratosphere during the SSW is responsible for the reduction of the reflection coefficient. However, these additional GW fluxes are not sufficient to compensate for the reduction of GW fluxes coming from the troposphere to the mesosphere. As a result, there is mesospheric cooling accompanied by SSW events.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"73 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475178","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}

{"title":"The role of naphthalene and its derivatives in the formation of secondary organic aerosol in the Yangtze River Delta region, China","authors":"Fei Ye, Jingyi Li, Yaqin Gao, Hongli Wang, Jingyu An, Cheng Huang, Song Guo, Keding Lu, Kangjia Gong, Haowen Zhang, Momei Qin, Jianlin Hu","doi":"10.5194/acp-24-7467-2024","DOIUrl":"https://doi.org/10.5194/acp-24-7467-2024","url":null,"abstract":"Abstract. Naphthalene (Nap) and its derivatives, including 1-methylnaphthalene (1-MN) and 2-methylnaphthalene (2-MN), serve as prominent intermediate volatile organic compounds (IVOCs) and contribute to the formation of secondary organic aerosol (SOA). In this study, the Community Multiscale Air Quality (CMAQ) model coupled with detailed emissions and reactions of these compounds was utilized to examine their roles in the formation of SOA and other secondary pollutants in the Yangtze River Delta (YRD) region during summer. Significant underestimations of Nap and MN concentrations (by 79 % and 85 %) were observed at the Taizhou site based on the model results using the default emissions. Constrained by the observations, anthropogenic emissions of Nap and MN in the entire region were multiplied by 5 and 7, respectively, to better capture the evolution of pollutants. The average concentration of Nap reached 25 ppt (parts per trillion) in the YRD, with Nap contributing 4.1 % and 8.1 % (up to 12.6 %) of total aromatic emissions and aromatic-derived secondary organic carbon (SOC), respectively. The concentrations of 1-MN and 2-MN were relatively low, averaging 2 and 5 ppt, respectively. Together, they accounted for only 2.4 % of the aromatic-derived SOC. The impacts of Nap and MN oxidation on ozone and radicals were insignificant at regional scales but were not negligible when considering daily fluctuations in locations with high emissions of Nap and MN. This study highlights the significant roles of Nap and MN in the formation of SOA, which may pose environmental risks and result in adverse health effects.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"18 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475199","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}

{"title":"Observations of high time-resolution and size-resolved aerosol chemical composition and microphyscis in the central Arctic: implications for climate-relevant particle properties","authors":"Benjamin Heutte, Nora Bergner, Hélène Angot, Jakob B. Pernov, Lubna Dada, Jessica A. Mirrielees, Ivo Beck, Andrea Baccarini, Matthew Boyer, Jessie M. Creamean, Kaspar R. Daellenbach, Imad El Haddad, Markus M. Frey, Silvia Henning, Tiaa Laurila, Vaios Moschos, Tuukka Petäjä, Kerri A. Pratt, Lauriane L. J. Quéléver, Matthew D. Shupe, Paul Zieger, Tuija Jokinen, Julia Schmale","doi":"10.5194/egusphere-2024-1912","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1912","url":null,"abstract":"<strong>Abstract.</strong> Aerosols play a critical role in the Arctic’s radiative balance, influencing solar radiation and cloud formation based on their physicochemical properties (e.g., size, abundance, and chemical composition). Limited observations in the central Arctic leave gaps in understanding aerosol dynamics year-round, affecting model predictions of climate-relevant properties. Here, we present the first annual high-time resolution observations of submicron aerosol chemical composition in the central Arctic during the Arctic Ocean 2018 (AO2018) and the 2019–2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expeditions. Seasonal variations in aerosol mass concentrations and chemical composition were found to be driven by typical Arctic seasonal regimes. Organic aerosols dominated the pristine summer, while anthropogenic sulfate prevailed in autumn and spring under Arctic haze conditions. Ammonium, which impacts aerosol acidity, was consistently less abundant, relative to sulfate, in the central Arctic compared to lower latitudes of the Arctic. Cyclonic (storm) activity was found to have a significant influence on aerosol variability by enhancing both emission from local sources and transport of remote aerosol, with locally wind-generated particles contributing up to 80 % (20 %) of the cloud condensation nuclei population in autumn (spring). While the analysis presented herein provides the current central Arctic aerosol baseline, which will serve to improve climate model predictions in the region, it also underscores the importance of integrating short-timescale processes, such as seasonal wind-driven aerosol sources from blowing snow and open leads/ocean in model simulations, especially in light of the declining mid-latitude anthropogenic emissions influence and the increasing local anthropogenic emissions.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"24 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141475247","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}

{"title":"Measurement report: Aerosol vertical profiling over the Southern Great Barrier Reef using lidar and MAX-DOAS measurements","authors":"Robert G. Ryan, Lilani Toms-Hardman, Alexander Smirnov, Daniel Harrison, Robyn Schofield","doi":"10.5194/egusphere-2024-1111","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1111","url":null,"abstract":"<strong>Abstract.</strong> <span>Aerosol vertical profile measurements were made using multi-axis differential optical absorption spectroscopy (MAX-DOAS) and mini-Micropulse LiDAR (MPL) at One Tree Island in the Southern Great Barrier Reef from February to April 2023. </span><span>This is an understudied location in terms of atmospheric aerosols and chemistry but is growing in importance as multiple research streams examine the influence of aerosols on radiation over the </span><span>Great Barrier Reef</span><span>. Solar radiation management proposals require regional-scale aerosol modelling, which is evaluated against aerosol extinction and optical depth measurements, necessitating a thorough understanding of measurements of these quantities. </span><span>MPL aerosol retrieval showed extinction-to-backscatter ratios (</span><span>0.031 on average) </span><span>and depolarization ratios (0.015 on average) consistent with clean, unpolluted Southern hemispheric marine aerosol. The maximum </span><span>depolarization ratio tended to be above the layer of maximum MPL backscatter, which is attributed to dried sea-salt layers above the boundary layer. MAX-DOAS and MPL extinction profiles show aerosol layers extending beyond 2 km altitude in the middle of the day, but predominantly below 1 km at other times. We also compared aerosol optical depth measurements from integrating the MAX-DOAS and MPL extinction profiles, with observations from a hand-held Microtops sun photometer. Mean aerosol optical depth (AOD) values across the campaign compare well, being 0.083 ± 0.002 for the Microtops, 0.090 ± 0.032 for the MAX-DOAS and 0.104 ± 0.028 for the MPL. However, AOD observations at a given time, and the AOD diurnal cycle, often varied between instruments. This likely indicates strong horizontal inhomogeneity in aerosol in this environment, a factor which makes it challenging to accurately compare AOD estimates from different viewing geometries, but which is important for future aerosol modelling studies in this region to consider.</span><span></span>","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"336 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462557","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}

{"title":"Age of air from in situ trace gas measurements: Insights from a new technique","authors":"Eric A. Ray, Fred L. Moore, Hella Garny, Eric J. Hintsa, Bradley D. Hall, Geoff S. Dutton, David Nance, James W. Elkins, Steven C. Wofsy, Jasna Pittman, Bruce Daube, Bianca C. Baier, Jianghanyang Li, Colm Sweeney","doi":"10.5194/egusphere-2024-1887","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1887","url":null,"abstract":"<strong>Abstract.</strong> The age of air is an important transport diagnostic that can be derived from trace gas measurements and compared to global chemistry climate model output. We describe a new technique to calculate the age of air, measuring transport times from the Earth’s surface to any location in the atmosphere based on simultaneous <em>in situ</em> measurements of multiple key long-lived trace gases. The primary benefits of this new technique include (1) optimized ages of air consistent with simultaneously measured SF₆ and CO₂, (2) age of air from the upper troposphere through the stratosphere, (3) estimates of the second moment of age spectra that have not been well constrained from measurements and (4) flexibility to be used with measurements across multiple instruments, platforms and decades. We demonstrate the technique on aircraft and balloon measurements from the 1990s, the last period of extensive stratospheric <em>in situ</em> sampling, and several recent missions from the 2020s, and compare the results with previously published and modeled values.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"59 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462548","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}

{"title":"Variability and long-term changes in tropical cold-point temperature and water vapor","authors":"Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski","doi":"10.5194/acp-24-7405-2024","DOIUrl":"https://doi.org/10.5194/acp-24-7405-2024","url":null,"abstract":"Abstract. The tropical tropopause layer (TTL) is the main gateway for air transiting from the troposphere to the stratosphere and therefore impacts the chemical composition of the stratosphere. In particular, the cold-point tropopause, where air parcels encounter their final dehydration, effectively controls the water vapor content of the lower stratosphere. Given the important role of stratospheric water vapor for the global energy budget, it is crucial to understand the long-term changes in cold-point temperature and their impact on water vapor trends. Our study uses Global Navigation Satellite System – Radio Occultation (GNSS-RO) data to show that there has been no overall cooling trend of the TTL over the past 2 decades, in contrast to observations prior to 2000. Instead, the cold point is warming, with the strongest trends of up to 0.7 K per decade during boreal winter and spring. The cold-point warming shows longitudinal asymmetries, with the smallest warming over the central Pacific and the largest warming over the Atlantic. These asymmetries are anticorrelated with patterns of tropospheric temperature trends, and regions of strongest cold-point warming are found to show slight cooling trends in the upper troposphere. Overall, the here-identified warming of the cold point is consistent with model predictions under global climate change, which attribute the warming trends to radiative effects. The seasonal signals and zonal asymmetries of the cold-point temperature and height trends might be related to dynamical responses to enhanced upper-tropospheric heating, changing convection, or trends in the stratospheric circulation. Water vapor observations in the TTL show mostly positive trends consistent with cold-point warming for 2004–2021. We find a decrease in the amplitude of the cold-point temperature seasonal cycle by ∼ 7 % driving a reduction in the seasonal cycle in 100 hPa water vapor by 5 %–6 %. Our analysis shows that this reduction in the seasonal cycle is transported upwards together with the seasonal anomalies and has reduced the amplitude of the well-known tape recorder over the last 2 decades.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"45 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462570","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}

{"title":"Modeling impacts of dust mineralogy on fast climate response","authors":"Qianqian Song, Paul Ginoux, María Gonçalves Ageitos, Ron L. Miller, Vincenzo Obiso, Carlos Pérez García-Pando","doi":"10.5194/acp-24-7421-2024","DOIUrl":"https://doi.org/10.5194/acp-24-7421-2024","url":null,"abstract":"Abstract. Mineralogical composition drives dust impacts on Earth's climate systems. However, most climate models still use homogeneous dust, without accounting for the temporal and spatial variation in mineralogy. To quantify the radiative impact of resolving dust mineralogy on Earth's climate, we implement and simulate the distribution of dust minerals (i.e., illite, kaolinite, smectite, hematite, calcite, feldspar, quartz, and gypsum) from Claquin et al. (1999) (C1999) and activate their interaction with radiation in the GFDL AM4.0 model. Resolving mineralogy reduces dust absorption compared to the homogeneous dust used in the standard GFDL AM4.0 model that assumes a globally uniform hematite volume content of 2.7 % (HD27). The reduction in dust absorption results in improved agreement with observation-based single-scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth's Radiant Energy System), and land surface temperature from the CRU (Climatic Research Unit) compared to the baseline HD27 model version. It also results in distinct radiative impacts on Earth's climate over North Africa. Over the 19-year (from 2001 to 2019) modeled period during JJA (June–July–August), the reduction in dust absorption in AM4.0 leads to a reduction of over 50 % in net downward radiation across the Sahara and approximately 20 % over the Sahel at the top of the atmosphere (TOA) compared to the baseline HD27 model version. The reduced dust absorption weakens the atmospheric warming effect of dust aerosols and leads to an alteration in land surface temperature, resulting in a decrease of 0.66 K over the Sahara and an increase of 0.7 K over the Sahel. The less warming in the atmosphere suppresses ascent and weakens the monsoon inflow from the Gulf of Guinea. This brings less moisture to the Sahel, which combined with decreased ascent induces a reduction of precipitation. To isolate the effect of reduced absorption compared to resolving spatial and temporal mineralogy, we carry out a simulation where the hematite volume content of homogeneous dust is reduced from 2.7 % to 0.9 % (HD09). The dust absorption (e.g., single-scattering albedo) of HD09 is comparable to that of the mineralogically speciated model on a global mean scale, albeit with a lower spatial variation that arises solely from particle size. Comparison of the two models indicates that the spatial inhomogeneity in dust absorption resulting from resolving mineralogy does not have significant impacts on Earth's radiation and climate, provided there is a similar level of dust absorption on a global mean scale before and after resolving dust mineralogy. However, uncertainties related to emission and distribution of minerals may blur the advantages of resolving minerals to study their impact on radiation, cloud properties, ocean biogeochemistry, air quality, and photochemistry. On the other hand, lumping together clay minerals (i.e., illite, kaolinite, and smectite), but excluding externa","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"32 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141462503","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}

{"title":"Characterisation of low-base and mid-base clouds and their thermodynamic phase over the Southern Ocean and Arctic marine regions","authors":"Barbara Dietel, Odran Sourdeval, Corinna Hoose","doi":"10.5194/acp-24-7359-2024","DOIUrl":"https://doi.org/10.5194/acp-24-7359-2024","url":null,"abstract":"Abstract. The thermodynamic phase of clouds in low and middle levels over the Southern Ocean and the Arctic marine regions is poorly known, leading to uncertainties in the radiation budget in weather and climate models. To improve the knowledge of the cloud phase, we analyse 2 years of the raDAR-liDAR (DARDAR) dataset based on active satellite instruments. We classify clouds according to their base and top height and focus on low-, mid-, and mid- to low-level clouds as they are the most frequent in the mixed-phase temperature regime. Low-level single-layer clouds occur in 8 %–15 % of all profiles, but single-layer clouds spanning the mid-level also amount to approx. 15 %. Liquid clouds show mainly a smaller vertical extent but a horizontally larger extent compared to ice clouds. The results show the highest liquid fractions for low-level and mid-level clouds. Two local minima in the liquid fraction are observed around cloud top temperatures of −15 and −5 °C. Mid-level and mid- to low-level clouds over the Southern Ocean and low-level clouds in both polar regions show higher liquid fractions if they occur over sea ice compared to the open ocean. Low-level clouds and mid- to low-level clouds with high sea salt concentrations, used as a proxy for sea spray, show reduced liquid fractions. In mid-level clouds, dust shows the largest correlations with liquid fraction, with a lower liquid fraction for a higher dust aerosol concentration. Low-level clouds clearly show the largest contribution to the shortwave cloud radiative effect in both polar regions, followed by mid- to low-level clouds.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"66 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141461923","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}

{"title":"Global carbon emission accounting: national-level assessment of wildfire CO2 emission – a case study of China","authors":"Xuehong Gong, Zeyu Liu, Jie Tian, Qiyuan Wang, Guohui Li, Zhisheng An, Yongming Han","doi":"10.5194/egusphere-2024-1684","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1684","url":null,"abstract":"<strong>Abstract.</strong> Wildfires release large amounts of greenhouse gases into the atmosphere, exacerbating climate change and causing severe impacts on air quality and human health. Including carbon dioxide (CO₂) emissions from wildfires in international assessments and national emission reduction responsibilities is crucial for global carbon reduction and environmental governance. In this study, based on a bottom-up approach and using satellite data, combined with emission factor and aboveground biomass data for different vegetation cover types (forest, shrub, grassland, cropland), the dynamic changes in CO₂ emissions from wildfires in China from 2001 to 2022 were analyzed. The results showed that between 2001 and 2022, the total CO₂ emissions from wildfires in China were 693.7 Tg (1 Tg = 10¹² g), with an annual average of 31.5 Tg. The CO₂ emissions from cropland and forest fires were relatively high, accounting for 46 % and 32 %, respectively. The yearly variation in CO₂ emissions from forest and shrub fires showed a significant downward trend, while emissions from grassland fires remained relatively stable. In contrast, the CO₂ emissions from cropland fires showed a clear upward trend. High CO₂ emissions from wildfires were mainly concentrated in the eastern regions of Heilongjiang and Inner Mongolia Provinces in China, accounting for 44 % of the total annual emissions. Various factors such as daily cumulative sunshine hours (Spearman’s correlation coefficient, forest: -0.41, shrub:0.25; p &lt; 0.001) and the normalized difference vegetation index (NDVI; Spearman’s correlation coefficient, forest: -0.35, shrub: 0.37; p &lt; 0.001), influenced CO₂ emissions from forest and shrub fires. Moreover, temperature (Spearman’s correlation coefficient, -0.45, p &lt; 0.001) primarily affected CO₂ emissions from grassland fires. The CO₂ emissions from cropland fires negatively correlated with the gross domestic product (GDP) (Spearman’s correlation coefficient, -0.52, p &lt; 0.001) and population density (Spearman’s correlation coefficient, -0.51, p &lt; 0.001). China's policy management has been crucial in reducing CO₂ emissions from wildfires. By accurately assessing CO₂ emissions from wildfires, governments worldwide can better set CO₂ reduction targets, take corresponding measures, and contribute to the global response to climate change.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"22 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141461806","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}

{"title":"General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path","authors":"Johannes Mülmenstädt, Edward Gryspeerdt, Sudhakar Dipu, Johannes Quaas, Andrew S. Ackerman, Ann M. Fridlind, Florian Tornow, Susanne E. Bauer, Andrew Gettelman, Yi Ming, Youtong Zheng, Po-Lun Ma, Hailong Wang, Kai Zhang, Matthew W. Christensen, Adam C. Varble, L. Ruby Leung, Xiaohong Liu, David Neubauer, Daniel G. Partridge, Philip Stier, Toshihiko Takemura","doi":"10.5194/acp-24-7331-2024","DOIUrl":"https://doi.org/10.5194/acp-24-7331-2024","url":null,"abstract":"Abstract. General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought to stem in part from GCMs' inability to represent the turbulence–microphysics interactions in cloud-top entrainment, a mechanism that leads to a reduction in liquid water in response to an anthropogenic increase in aerosols. In the real atmosphere, enhanced cloud-top entrainment is thought to be the dominant adjustment mechanism for liquid water path, weakening the overall ERFaci. We show that the latest generation of GCMs includes models that produce a negative correlation between the present-day cloud droplet number and liquid water path, a key piece of observational evidence supporting liquid water path reduction by anthropogenic aerosols and one that earlier-generation GCMs could not reproduce. However, even in GCMs with this negative correlation, the increase in anthropogenic aerosols from preindustrial to present-day values still leads to an increase in the simulated liquid water path due to the parameterized precipitation suppression mechanism. This adds to the evidence that correlations in the present-day climate are not necessarily causal. We investigate sources of confounding to explain the noncausal correlation between liquid water path and droplet number. These results are a reminder that assessments of climate parameters based on multiple lines of evidence must carefully consider the complementary strengths of different lines when the lines disagree.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"27 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141461993","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}