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Brown carbon (BrC) in China is of great interest to the regional and global climate due to its strong absorption of sunlight. However, the contribution of BrC to total carbonaceous aerosol light absorption and its direct radiative effects (DRE) in China remains largely uncertain. To better assess its climate impact in China, we develop an explicit BrC scheme and implement it in a global climate model, which includes optical parameters of primary BrC derived from local measurements, secondary BrC absorption, and a photobleaching parameterization of BrC. By comparing with multi‐type observational data, we find that with the implementation of this scheme, the model captures the seasonal variations of BrC light absorption well in China. The model estimates that BrC contributes 19% and 12% to the total light absorption of carbonaceous aerosol in China in winter and summer, resulting in 0.110 and 0.205 W m−2 of DRE, respectively. Plain Language Summary While the existing research on the direct radiative effects (DRE) of brown carbon (BrC) predominantly focuses on biomass‐burning sources, little attention has been given to BrC originating from anthropogenic sources. Coal combustion and residential fuels used for cooking and heating release many brown carbon aerosols in China. Source of BrC in China is different from that in Europe and North America. Therefore, studying the light‐absorbing properties and climate effects of BrC in China is of great scientific significance. Here, we introduce local optical parameters of primary BrC based on observations in China, secondary BrC absorption, and chemical bleaching of BrC in a global climate model (GCM). We find that the model can simulate the strong seasonal variations of BrC absorption observed in China. With the help of the model and multi‐type measurement data, we estimate the contribution of BrC to the total carbonaceous aerosol absorption and the DRE of BrC in China in different seasons. This study is the first attempt to introduce an explicit BrC scheme in a GCM to estimate the DRE of BrC in China. Key Points An explicit brown carbon (BrC) scheme is introduced in a climate model together with observations to constrain light absorption of BrC BrC contributes 19% and 12% of total carbonaceous aerosol absorption in China in winter and summer, respectively Simulated direct radiative effects due to BrC absorption over China are 0.110 and 0.205 W m2 in the winter and summer seasons

Wildfires have long been regarded as one chief culprit in regional air pollution, and pose great impacts on climate change. Although climate forcing of wildfire smoke has been widely investigated, its influence on synoptic systems remains unclear. Based on measurement and modeling analysis, the impact of wildfire smoke on the development of a mid‐latitude cyclone was revealed for Canadian wildfires in early June of 2023. The radiative forcing induced by smoke at surface and in the atmosphere reached up to −150 and 100 W m−2, posing opposite tendencies of atmospheric stratification over the land and ocean. Such perturbations contributed to the enhancement and stagnation of the cyclone, which favored the transport of smoke from the fire‐intensive region, indicated by nearly 40% increment of PM2.5 mass flux. With escalating wildfire risk in the future, the inclusion of smoke aerosols' impacts on meteorology in weather forecast models is of great importance. Plain Language Summary Wildfires are uncontrolled fires that burn in the wildland vegetation, posing great challenges to regional air quality and global climate. Wildfire smoke has been known to exert great climate forcing via aerosol‐radiation interaction yet its impact on synoptic scales needs further investigation. Here, based on comprehensive observations and modeling analysis for the extreme Canadian wildfires in early June of 2023, smoke aerosol is revealed to induce significant radiative forcing and yield opposite modifications of temperature stratification over the land and ocean, resulting in intensified and stagnant mid‐latitude cyclone. Such perturbations favored the transport of smoke from fire‐intensive region to downwind cities in Canada and United States, and the subsequent long‐range transport dominated by the cyclone. Key Points Smoke from intensive Canadian wildfires in early June of 2023 degraded the air quality of cities in eastern Canada and United States The wildfire smoke enhanced the development of the mid‐latitude cyclone via smoke aerosol‐radiation interaction The intensification and stagnation of the cyclone facilitated the transport of smoke to downwind cities in northeastern United States

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with unusual meteorological conditions, including weaker wind speeds. Here we show, based on model simulations, that during years with decreased wind speed, large decreases in dust emissions (29%) moderate the wintertime land–sea surface air temperature difference and further decrease winds by −0.06 (±0.05) m s −1 averaged over eastern China. The dust-induced lower winds enhance stagnation of air and account for about 13% of increasing aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime aerosol concentrations, with important implications that need to be taken into account by air quality studies. Anthropogenic aerosol and calm conditions give rise to winter haze episodes in eastern China. Yang et al . show that these weak winds also decrease natural dust emissions, reducing the land–ocean temperature difference and associated winds, enhancing air stagnation and pollution in this region.

Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantially elevated lung cancer risk from PAHs. Model results indicate that the OA coating is more effective in shielding BaP in the middle/high latitudes compared with the tropics because of differences in OA properties (semisolid when cool/dry vs. liquid-like when warm/humid). Faster chemical degradation of BaP in the tropics leads to higher concentrations of BaP oxidation products over the tropics compared with higher latitudes. This study has profound implications demonstrating that OA strongly modulates the atmospheric persistence of PAHs and their cancer risks.

The Hunga Tonga‐Hunga Ha'apai (HTHH) eruption on 15 January 2022 was one of the most explosive volcanic events of the 21st century so far. According to satellite‐based measurements, 0.4 Tg of sulfur dioxide (SO2) was injected into the stratosphere during the eruption. By using observations and model simulations, here we investigate changes in the chemical compositions of the stratosphere 1 year after the HTHH eruption and examine the key physical and chemical processes that influence the ozone (O3) concentrations. Injected SO2 was oxidized into sulfate during the first 2 months, and transported from the tropics to the Antarctic by the Brewer‐Dobson circulation within 1 year. In mid‐to‐low latitudes, enhanced sulfate aerosol increased O3 concentrations in the middle stratosphere but declined in the lower stratosphere. In addition to the chemical processes, sulfate aerosols also reduced polar low‐stratospheric O3 concentrations through enhanced Antarctic upwelling anomalies. Plain Language Summary The Hunga Tonga‐Hunga Ha'apai (HTHH) eruption on 15 January 2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention. Volcanic ash and gases entering the atmosphere could affect weather and climate processes. Recent studies have largely explored the effects on global warming of HTHH eruption, and have founded that its climate impact is not very strong. However, its impacts on ozone (O3) remains unclear. We used observations and models to analyze how HTHH eruption could influence O3. It confirms that stratospheric O3 can be affected when volcano‐induced aerosols are transported. We suggest that physical and chemical processes combine together to influence stratospheric O3 after HTHH eruption. Moreover, the effect on O3 of HTHH eruption is probably one of the reasons for the recent discovery of a larger O3 hole in Antarctica. Key Points Volcano‐induced stratospheric sulfate aerosols are transported toward the South Pole and downwards by the Brewer‐Dobson circulation Catalytic nitrogen oxide ozone loss cycles and sulfate aerosols' radiative effects cause extra‐polar stratospheric ozone anomalies Volcanic aerosol‐induced heterogeneous chemistry and enhanced upward transport causes polar stratospheric ozone anomalies

Typhoons and wildfires are major global climate and environmental hazards, yet their potential interactions remain poorly understood, particularly through remote atmospheric forcing. Taking the 2023 Quebec wildfires as an example, we investigate how a tropical cyclone can influence wildfire‐favorable conditions. Observational analyses and Linear Baroclinic Model simulations reveal that western North Pacific Super Typhoon Mawar remotely intensified a North American blocking high by triggering a Rossby wave train, thereby driving dry lightning and anomalous dry air conditions that favored wildfire ignition and spread. Based on Weather Research and Forecasting model sensitivity experiments, we show that Mawar contributed 34 ± 6%, 41 ± 3%, and 55 ± 5% to the blocking's total amplification during the first three days of its rapid development, respectively. This findings highlight that western North Pacific typhoons can remotely modulate blocking highs to drive North American wildfire weather, advancing our understanding of remote typhoon‐wildfire teleconnections.

Airborne observations from ACCLIP on 2 August 2022, combined with Lagrangian particle dispersion model back trajectories, reveal that SO2 mixing ratios at 14–16 km were enhanced by a factor of 4–6 in regions influenced by tropical cyclones (TCs). These enhancements are linked to rapid lofting of marine dimethyl sulfide (DMS) into the upper troposphere (UT). GEOS‐Chem simulations indicated that on 31 July 2022, TC‐scale circulation injected DMS into the UT within hours, with a mean flux of 9.4 kg hr−1 across 0.5–12 km and 8.4% of emissions penetrating above 12 km, consistent with observations of elevated DMS at the same altitudes. Because of its low solubility and longer UT lifetime (59.2 vs. 5.7 hr at the surface), DMS sustains SO2 production that is largely resistant to wet scavenging. This TC‐driven pathway provides a significant natural SO2 source in the UT, with implications for aerosol–cloud–climate interactions.

Background With the rise of reported mental disorders and behavioral issues after the outbreak of the coronavirus disease 2019 (COVID-19) pandemic, psychiatrists and mental health care are urgently needed more than ever before. The psychiatric career carries a high emotional burden and stressful demands, which bring issues on psychiatrists’ mental health and well-being into question. To investigate the prevalence and risk factors of depression, anxiety, and work burnout among psychiatrists in Beijing during the COVID-19 pandemic. Methods This cross-sectional survey was conducted from January 6 to January 30, 2022, two years after COVID-19 was declared a global pandemic. Recruitment was performed using a convenience sample approach by sending online questionnaires to psychiatrists in Beijing. The symptoms of depression, anxiety, and burnout were evaluated using the Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and Maslach Burnout Inventory-General Survey (MBI-GS). The perceived stress and social support were measured by the Chinese Perceived Stress Scale (CPSS) and Social Support Rating Scale (SSRS), respectively. Results The data of 564 psychiatrists (median [interquartile range] age, 37 [30–43] years old) of all 1532 in Beijing were included in the statistical analysis. The prevalence of symptoms of depression, anxiety and burnout were 33.2% (95% CI, 29.3-37.1%, PHQ-9 ≥ 5), 25.4% (95% CI, 21.8-29.0%, GAD-7 ≥ 5) and 40.6% (95% CI, 36.5-44.7%, MBI-GS ≥ 3 in each of the three subdimensions), respectively. The psychiatrist with a higher score on perceived stress was more likely to suffer from depressive symptoms (adjusted odds ratios [ORs]: 4.431 [95%CI, 2.907–6.752]); the anxiety symptoms (adjusted ORs: 8.280 [95%CI, 5.255–13.049]), and the burnout conditions (adjusted ORs: 9.102 [95%CI, 5.795–14.298]). Receiving high social support was an independent protective factor against symptoms of depression (adjusted ORs: 0.176 [95%CI, [0.080–0.386]), anxiety (adjusted ORs: 0.265 [95%CI, 0.111–0.630]) and burnout (adjusted ORs: 0.319 [95%CI, 0.148–0.686]). Conclusions Our data suggest a considerable proportion of psychiatrists also suffer from depression, anxiety, and burnout. Perceived stress and social support influence depression, anxiety, and burnout. For public health, we must work together to reduce the pressure and increase social support to mitigate mental health risks in psychiatrists.

Objectives The present study aimed to investigate sleep disturbance and mental health symptoms in elite athletes during the Beijing 2022 Winter Olympics preparatory period and whether they were associated with chronotype. Method This study included 428 elite Chinese winter sports athletes from the National Training Team (the response proportion was 94.1%) in August 2021. All participants completed self-reported scales, including Insomnia Severity Index (ISI) to assess sleep disturbance, the Generalized Anxiety Disorder Seven-Item (GAD-7) and the Patient Health Questionnaire Nine-Item (PHQ-9) to assess mental health symptoms (including anxiety and depression symptoms). Multivariable logistic regression models were applied to identify factors associated with sleep and mental health symptoms. Results In this study, we found that the point prevalence was 13.1% (95% confidence interval [CI] 11.5–14.7%) of insomnia, 20.1% (95% CI 18.2–22.0%) of depression, and 15.0% (95% CI 13.3–16.7%) of anxiety symptoms. Female sex (odds ratio 2.4 [95% CI 1.3–4.6], p  = 0.008) and age of 20–24 years (4.1 [1.5–10.9], p  = 0.005) were associated factors for insomnia symptoms. Evening chronotype was a significant contributing factor for insomnia (6.7 [2.0–22.6], p  = 0.002), depression (5.7 [2.2–15.1], p  < 0.001), and anxiety (7.4 [2.3–23.2], p  < 0.001) symptoms. Conclusions Disruptions were reported in the sleep and mental health of elite athletes during the preparation phase of the Beijing 2022 Winter Olympics. Evening chronotype may be a potential independent predictor of sleep and mental health changes for Chinese winter sport elite athletes in preparatory period, and further research is needed to generalize the results. These findings suggest that strategies to manage sleep and mental health better are critical.

The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department of Energy has significant new treatments of aerosols and light‐absorbing snow impurities as well as their interactions with clouds and radiation. This study describes seven sets of new aerosol‐related treatments (involving emissions, new particle formation, aerosol transport, wet scavenging and resuspension, and snow radiative transfer) and examines how they affect global aerosols and radiative forcing in E3SMv1. Altogether, they give a reduced total aerosol radiative forcing (−1.6 W/m2) and sensitivity in cloud liquid water to aerosols, but an increased sensitivity in cloud droplet size to aerosols. A new approach for H2SO4 production and loss largely reduces a low bias in small particles concentrations and leads to substantial increases in cloud condensation nuclei concentrations and cloud radiative cooling. Emitting secondary organic aerosol precursor gases from elevated sources increases the column burden of secondary organic aerosol, contributing substantially to global clear‐sky aerosol radiative cooling (−0.15 out of −0.5 W/m2). A new treatment of aerosol resuspension from evaporating precipitation, developed to remedy two shortcomings of the original treatment, produces a modest reduction in aerosols and cloud droplets; its impact depends strongly on the model physics and is much stronger in E3SM Version 0. New treatments of the mixing state and optical properties of snow impurities and snow grains introduce a positive present‐day shortwave radiative forcing (0.26 W/m2), but changes in aerosol transport and wet removal processes also affect the concentration and radiative forcing of light‐absorbing impurities in snow/ice. Plain Language Summary Aerosol and aerosol‐cloud interactions continue to be a major uncertainty in Earth system models, impeding their ability to reproduce the observed historical warming and to project changes in global climate and water cycle. The U.S. DOE Energy Exascale Earth System Model version 1 (E3SMv1), a state‐of‐the‐science Earth system model, was developed to use exascale computing to address the grand challenge of actionable predictions of variability and change in the Earth system critical to the energy sector. It has been publicly released with new treatments in many aspects, including substantial modifications to the physical treatments of aerosols in the atmosphere and light‐absorbing impurities in snow/ice, aimed at reducing some known biases or correcting model deficiencies in representing aerosols, their life cycle, and their impacts in various components of the Earth system. Compared to its predecessors (without the new treatments) and observations, E3SMv1 shows improvements in characterizing global distributions of aerosols and their radiative effects. We conduct sensitivity experiments to understand the impact of individual changes and provide guidance for future development of E3SM and other Earth system models. Key Points A description and assessment of new aerosol treatments in the Energy Exascale Earth System Model Version 1 (E3SMv1) is provided Contributions to the total aerosol‐related radiative forcing by individual new treatments and different processes are quantified Some of the new treatments are found to depend on model physics and require further improvement for E3SM or other Earth system models