Halogens play important roles in atmospheric chemistry and climate change. However, emission data for particulate halogens from industrial sources remain incomplete, which hinders advances in atmospheric chemistry modeling. In this study, we analyzed the atmospheric emissions of halogens in fine particulate matter samples collected from 112 full-scale industrial plants across 13 sectors. The results show that municipal solid-waste incineration exhibited the highest concentrations of total particulate halogen and particulate chlorine (pCl). Iron-ore sintering showed the highest concentrations of particulate fluorine (pF) and particulate bromine (pBr). Using the emission factor method, we identified cement kilns co-processing solid waste and iron-ore sintering as the most significant emission sources, with annual emissions of p(F + Cl + Br) reaching 32,785 and 6,155 t, respectively. Eastern China had significantly higher emissions of p(F + Cl + Br) than other regions. Furthermore, emissions across provinces were generally higher during the cold season than in warmer seasons. This pattern underscores the need for enhanced emission reduction and control measures targeting these major sources and critical periods.
Regional air-sea coupling critically influences East Asian summer climate, yet its representation in current modeling systems remains challenging. This study enhances mechanistic understanding of this coupling by comparing two long-term simulations (1991–2014) using the new Regional Integrated Earth Model System (RIEMS) with air-sea coupling and its standalone atmospheric model (WRF). Results show both RIEMS and WRF demonstrate advantages and added values in reproducing summer air temperature (T2mean and T2max) and precipitation compared to the ensemble mean of global climate models (ENS). Meanwhile, RIEMS better reproduces T2mean and T2max compared to WRF, particularly over East China. RIEMS reduces the T2max warm bias in WRF by 0.7°C on average over land. Additionally, RIEMS offers more accurate simulations of surface sensible and latent heat fluxes while WRF overestimates sensible heat flux by nearly 7.0 W m−2 over land. Mechanistic analyses indicate that WRF reproduces less cloud cover and increased incoming shortwave radiation, resulting in higher sensible heat flux and warmer air temperature. The climatological decrease in cloud cover in WRF can be attributed to its warmer air temperature. Meanwhile, WRF simulated less outgoing shortwave radiation and trapped more longwave radiation, leading to warmer surface air temperature. Furthermore, without air-sea coupling, WRF strengthened water and energy transportation from ocean to land through a stronger southwesterly airflow, which is more conducive to simulating higher surface air temperatures in WRF over a large area. These findings provide mechanistic evidence that regional air-sea coupling is essential for credible climate simulations and projections over East Asia.
The cross-equatorial northerly surges (CENSs) often induce severe rainfalls in the Java region; however, the role of CENSs in the formation and moisture supply of these rainfalls remains unclear. To evaluate this, we analyzed the CENS-related heavy rainfalls over the western Java region in mid-February 2021 based on observations, ERA5 reanalysis, and a set of numerical experiments using atmosphere-ocean coupled and atmosphere-only models. Results show that convection over the western Java region was enhanced due to the southward moisture transport by CENSs and related moisture convergence, except for the most severe event on 18 February. By focusing on this event, we found that the joint efforts of CENS and an anomalous southerly wind played the key role, while the latter also helped the merging of the convection south of Java and the diurnal convection over Java Island that eventually induced the long-lasting heavy rains. To quantitatively evaluate the role of CENS, we performed a backward trajectory experiment and found that about 40% of the accumulated moisture over the Java region was contributed by CENSs, with a dominant proportion from the surface evaporation over the oceans nearby, instead of remote regions. Moreover, based on our experiments, we demonstrated that the air-sea interactions enhanced the surface evaporation and helped in reproducing more realistic moisture supplies and convective activities during CENSs. In addition, our results also indicated that ERA5 underestimated the severe events, which was likely due to the poorly represented land-sea breezes and reanalysis-related unrealistic moisture variations.
The diurnal cycle is one of the predominant components of rainfall variability, yet accurately representing its timing and intensity remains challenging for general circulation models (GCMs). The accurate representation of diurnal convective-scale processes in GCMs is particularly important over the Maritime Continent (MC), where complex terrain and oceans produce unique diurnal cycles. A process that has been identified to be important to the diurnal cycle is cloud-radiative interactions. Idealized numerical modeling studies have shown that cloud-radiative interactions influence the strength and behavior of diurnal convection, but gaps remain in understanding its potential role over coastal and complex topographical regions. Using the Weather Research and Forecasting model in a convection-permitting framework, a 10-day control simulation is conducted over the MC alongside a daily-ensemble of sensitivity simulations where cloud-radiative interactions are turned off. Diurnal rain rate is higher, and rainfall initiates earlier over land when cloud-radiative interactions are absent, while no significant change is measured in diurnal rainfall offshore. The changes in diurnal cycle characteristics over land are primarily driven by the earlier and stronger diurnal increase in surface solar radiative flux, which increases surface sensible and latent heat flux relative to the control. The stronger surface fluxes increase daytime surface slope flow and convective triggering, with the greatest impact in regions of elevated terrain where high-albedo low-level clouds are abundant. These results imply that the accurate numerical representation of both clouds and their radiative interactions is vital to accurately predicting diurnal rainfall over complex topography, which remains a challenge in GCMs.
Biomass burning aerosols influence atmospheric temperatures by absorbing solar radiation, thereby altering the contrast between day and night temperatures. This study investigates the correlation between these aerosols and day-night (D-N) temperature changes over India by applying principal component analysis (PCA) in long-term (2003–2021) satellite observations (MODIS AOD, AIRS D-N temperature at 850 hPa, MOPITT CO) and MERRA-2 reanalysis data. Mode analysis for the premonsoon period identifies biomass burning in northeast India as the dominant source of the second mode of AOD, BC AOD, and CO, with strong covariations between BC AOD and AOD (R = 0.90) and between CO and AOD (R > 0.79). PCA of satellite observations shows that long-term variation of AOD and D-N temperature at 850 hPa in the second mode is strongly correlated (R = 0.83), highlighting the sensitivity of diurnal temperature variations to light-absorbing aerosols. This strong relationship is further confirmed with MERRA-2 reanalysis data. Moreover, high correlations (R > 0.85) between BC AOD and D-N temperature in the second mode validate the role of biomass burning in driving long-term diurnal temperature contrast. Reconstruction analysis over northeast India indicates that the BC AOD fraction accounts for approximately 42% of the D-N temperature variability during the 19-year study period. These findings not only quantify the critical role of biomass burning aerosols in modulating diurnal temperature variations across the Indian region but also provide satellite observation-based insights that have the potential to constrain the aerosol radiative effects on the atmospheric temperature profile in climate models.
Nitrogen-containing organic compounds (NOCs), encompassing a complex suite of oxidized and reduced organic nitrogen species, exert significant impacts on atmospheric light absorption, oxidation capacity, and global nitrogen cycling. Despite the growing recognition of NOCs as key components of atmospheric organic matter, their formation through aqueous-phase processes and potential environmental impacts have long been underestimated. This review begins by summarizing the major classes of NOC molecules, then synthesizes observational evidence on their formation in the aqueous-phase, particularly highlighting its critical role in generating nitroaromatic and N-heterocyclic compounds. Built on the observational evidence, we further discuss the related evaluation of the multi-faceted environmental impacts arising from the aqueous-phase NOC formation. The evidence demonstrates that aqueous-phase NOC chemistry exerts significant influence on atmospheric compositions, contributes up to 90% of brown carbon's radiative effects, enhances oxidative capacity and secondary organic aerosol production, and influences nitrogen speciation in wet deposition. However, most current model assessments exhibit considerable limitations in quantifying these effects, stemming primarily from oversimplified parameterizations of aqueous-phase chemistry that fail to adequately represent the full complexity of atmospheric multiphase systems. Furthermore, existing observational data sets remain insufficient, severely constraining efforts to optimize model parameters and validate simulation outputs. To address these critical knowledge gaps, we propose an integrated research framework that combines long-term monitoring of key NOC and various precursors and advanced simulations of aqueous-phase chemistry at the micrometer-scale reaction environments, which would constrain the parameterization of future models for the aqueous-phase chemistry and impacts of NOCs.
A high-resolution U-Th dated speleothem record from Bylliat cave, Meghalaya, spanning ∼722 to 1250 CE, provides new insights into dynamics of the Indian Summer Monsoon (ISM) through the Medieval Climate Anomaly (MCA). The δ18O values, supported by petrographic analyses, indicate extreme events in the ISM behavior. Our data report a distinctly wet phase between ∼722 and 775 CE, followed by a marked decline in precipitation from ∼775 to 850 CE. Subsequently, a prolonged drought-like condition prevailed between ∼850 and 890 CE. From ∼890 to 980 CE, the northeastern Himalaya witnessed return of wetter conditions, whereas from ∼1140 to 1250 CE the monsoon was relatively stable, analogous to modern ISM patterns in a non-El Niño scenario. Multidecadal ISM variability in the MCA appears to have been primarily modulated by solar activity, and consequent latitudinal migration of the Intertropical Convergence Zone. In contrast, subdecadal ISM variability was closely linked to changes in the El Niño-Southern Oscillation. The pronounced wet conditions from the eighth to thirteenth centuries are believed to have promoted agricultural expansion and crop diversification across India. However, these climatic conditions may also have influenced patterns of cultural and political change, particularly in the eastern regions of the subcontinent.
Atmospheric rivers (ARs) are narrow corridors of intense water vapor transport that have significant impacts on the Antarctic surface mass balance (SMB) through both snow accumulation and surface melt due to rain and heat. To estimate their impacts on future SMB, we study Antarctic ARs in an ensemble of 21st-century simulations of the IPSL-CM6 model. Although the number of detected ARs continuously increases when using a constant detection threshold based on recent moisture fluxes, it remains stable with an adaptive threshold evolving with the rising background moisture. In addition, ARs penetrate further into Antarctica following a wave-number 3 pattern. The severity of Antarctic ARs, measured by moisture fluxes, is projected to increase following the moisture content given by the Clausius-Clapeyron relation. The corresponding SMB impacts all become larger with both increasing snowfall and coastal surface melt and rainfall. However, their overall influence on the SMB is dominated by the increased snow accumulation related to ARs, which is rising by 17% at the scale of the continent. This is much larger than the overall increase in snow accumulation from all events combined, which is 9%, and is more closely related to the rise in total humidity in relation with temperature—that is, linked to the Clausius-Clapeyron relation.
This study utilizes 45 yrs of WACCM-X simulations with Specified Dynamics and 22 years of Aura Microwave Limb Sounder (MLS) observations to explicitly differentiate the behaviors of interhemispheric coupling (IHC) in early, mid-, and late winter subseasons attributed to northern hemisphere (NH) major sudden stratospheric warmings (SSWs). The typical IHC teleconnection pattern is identified in all cases and reasonable data-model agreement is shown. The simulated residual mean circulation, parameterized gravity wave (GW) forcing, and resolved planetary and tidal forcing represent intra-seasonal changes during NH major SSWs, which result in the different behaviors of IHCs. In particular, an anomalous cooling below the high-latitude summer mesopause is identified in addition to the typical IHC patterns in later subseasons and attributed to the consequences of changes in residual mean circulation and GW forcing due to upwelling effects.
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