Journal of Geophysical Research: Atmospheres最新文献

This study refines methane emission estimates for southeastern Australia's Gippsland region in 2019 through high-resolution atmospheric inverse modeling. Methane observations from three in situ monitoring sites were assimilated into a Bayesian four-dimensional variational inversion framework coupled with the Community Multiscale Air Quality model, employing prior emissions from the Open Methane Database (2024). Posterior results revealed increased emissions in the eastern region, particularly near gas infrastructure and wastewater facilities, suggesting that these sources may be underrepresented in prior inventories. In contrast, a consistent decline in methane emissions was observed across all months in the central-western part of the domain, where coal mining and power generation are concentrated. This decline is likely linked to the predominance of brown coal in the region, which emits substantially less methane than black coal, a distinction not clearly captured in the study inventory, potentially leading to overestimated emissions. Additionally, the most significant reduction in the entire studied domain occurred in February 2019, with emissions decreasing by approximately 30% relative to prior estimates. Sensitivity analyses and comparisons with the Emissions Database for Global Atmospheric Research inventory support the robustness of these findings. While total emissions across data sets were broadly similar, differences in spatial distribution led to notable variations in posterior outcomes. These results highlight the importance of incorporating local knowledge into emission inventories and the need for more detailed classification of emission sources, particularly coal type, to improve methane emission estimates at regional scales.

Peripheral subsidence of Northwest Pacific typhoons can trigger extreme surface ozone episodes, yet the relative contributions of local chemistry and vertical transport remain poorly constrained. Here we measured 30-min aerodynamic gradient fluxes of NO_x, O₃, and CO at 118 and 168 m on Canton Tower (Pearl River Delta) during 2 September typhoons in 2021 and 2022. Surface O₃ climbed by >50% in both events. In September 2021, moderate subsidence created hot, stagnant conditions that accelerated local photochemical ozone production, yielding upward O₃ flux. In September 2022, stronger, long-lived subsidence instead injected ozone-rich air from aloft, causing downward O₃ flux despite favorable chemistry. This flux evidence demonstrates that subsidence intensity toggles the balance between local production and vertical transport of ozone, informing forecasts of coastal extreme-ozone risk.

In this study, we use the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (SD-WACCM-X) to investigate how the migrating solar semidiurnal tide (SW2) in the mesosphere and lower thermosphere (MLT) responds to the strength of Arctic and Antarctic Stratospheric Polar Vortices (SPVs). SW2 shows a substantial response to both SPVs, though the Antarctic influence is weaker. During boreal winter, 50% of SW2 variability is linked to Arctic SPV strength, while 34% during austral spring is associated with Antarctic SPV. Classical tidal theory Hough modes (HMs) of SW2 point to a clear relationship between the HMs and Arctic SPV with the most significant change occurring in the first antisymmetric (2,3) HM. However, only the second symmetric (2,4) HM responds significantly to the Antarctic SPV. These distinctive differences in HMs arise from dynamic changes in the stratosphere and MLT. Stratospheric ozone contributes only 6%–10% to the (2,2) HM during weak state of Arctic SPV and shows no significant influence under Antarctic SPV variability. As such, HM variabilities are primarily caused by changes in background neutral winds during weak and strong Arctic and Antarctic SPVs rather than changes in stratospheric ozone heating. In addition, the zonal momentum budget of each HM of SW2 is analyzed. The classical term (Coriolis + pressure gradient forcing) exhibits the largest variations with the strength of the Arctic and Antarctic SPVs, followed by the advection term.

Compound-specific stable carbon isotope ratios (δ¹³C) were measured for low molecular weight aliphatic (C₂–C₆) dicarboxylic acids, phthalic acid, glyoxylic acid and glyoxal in Arctic aerosols collected at Alert (82.5°N) in late winter to early summer. Between dark winter in late February/early March to completely sunlit conditions in May the δ¹³C of many organic acids increased: (a) oxalic acid (C₂) from −23‰ to −5‰, (b) malonic acid (C₃, a precursor of C₂) from −28‰ to −17‰, and (c) glyoxylic acid (ωC₂, −18‰ to −10‰), also a precursor of C₂. In contrast, glyoxal, another precursor of oxalic acid and succinic acid, showed a wide variation from dark to light and no clear seasonal trend. Concentrations of C₂, ωC₂ and C₃ declined when their δ¹³C increased in April to May. The enrichment of ¹³C occurred during the preferential breaking of ¹²C–¹²C over ¹²C–¹³C bond in oxalic and other acids as solar radiation increased during polar sunrise. Photochemically driven variations in the isotopic enrichment of ¹³C of C₂ and related compounds that are a minor fraction of aerosol total carbon (TC), nevertheless they are the main source of variation in the δ¹³C values of TC during polar sunrise in the Arctic because the weakness of ¹²C–¹²C bond compared to ¹²C–¹³C bond is more pronounced for carboxylic acids than other species contributing to TC. This study on ¹³C signature of these species allows to gain information on their poorly known atmospheric budget in spite of the fact that they are ubiquitous in the atmosphere.

This study performs global variable resolution (VR) experiments using the Model for Prediction Across Scale-Atmosphere (MPAS-A) to simulate 3 years of July over the Tibetan Plateau (TP) at grid resolutions of 60, 60–10, and 60–3 km, transitioning from convective-permitting to quasi-hydrostatic scales. The re-initialization approach is used to constrain the background fields under the same parameterizations. The features analyzed here include mean spatial distribution, diurnal cycle, and evolution of every precipitation event. At coarser resolutions, MPAS-A misrepresents precipitation duration, with excessive rainfall persistence due to overly strong instability and weak intensity. Finer resolutions (especially 3 km) markedly improve sub-daily precipitation over the TP by resolving event durations, reducing the drizzle-like overestimation of long-duration rainfall at 60 km. These gains stem from sharper capture of onset-time forcing peaks (surface heating and moisture convergence) and faster instability removal, together with a weaker, non-linear dependence on moisture convergence and an enhanced representation of cessation. Overall, ∼10 km yields robust improvements with fewer artifacts, while 3 km offers the strongest sub-daily benefits but demands additional high-resolution observations for validation.

Based on seven reanalysis data sets and three atmospheric river (AR) detection algorithms, we investigate the dominant interdecadal modes of East Asian (EA) summer atmospheric rivers (ARs) from 1940 to 2024. The first mode exhibits a monopole pattern characterized by coherent AR enhancement, associated with a low-level anomalous anticyclone and an intensified western North Pacific subtropical high (WNPSH). The anomalous anticyclone is maintained by the meridional wave train induced from the western tropical Pacific under the anomalous Indo-West Pacific Walker circulation triggered by the negative sea surface temperature anomalies (SSTAs) over the southern Indian Ocean (IO), which is closely linked to the IO Basin mode. The second mode presents a zonal dipole pattern featured by opposite AR anomalies, corresponding to a pair of low-level anomalous cyclonic and anticyclonic circulations and the northeastward WNPSH retreat. The dipole circulation is mainly sustained by the meridional wave train excited from the Maritime Continent (MC) when cold tropical eastern Pacific SSTAs and warm MC SSTAs generate an anomalous Pacific Walker circulation, accompanied by the combined effect of a wave train from the mid-latitudes. The second mode is significantly modulated by the Pacific Decadal Oscillation. Particularly, the dominant EA AR mode varied from the monopole to dipole modes around 1977/1978 due to changes in oceanic forcing from the Indian to the Pacific Ocean, leading to a shift in EA AR frequency from an increasing trend to a relatively stable state.

Sulfur and nitrogen wet deposition is governed by anthropogenic emissions and precipitation regimes. However, the impacts of precipitation characteristics on wet deposition SO₄²⁻, NO₃⁻ and NH₄⁺ and its hysteresis to precursor emission controls remain inadequately quantified. Multiyear (2010–2024) rainwater chemistry, air pollutants, and meteorological parameters were monitored in Wuhan. Random forest models were applied to weather-normalized sulfur and nitrogen wet deposition. Trend analysis using the normalized data revealed that 1-unit reduction in precursor emissions declined 0.14–0.48-unit sulfur and nitrogen wet deposition. This hysteresis was driven partly by enhanced wet scavenging associated with increased light rain frequency, as the scavenging ratios of atmospheric sulfur and nitrogen compounds increased by 1.9%–10.5% yr⁻¹ from 2016 (2019) to 2024. Light rain with a rate ≤16.5, 17.3, and 6.8 mm d⁻¹ most strongly influenced wet deposition trends of NH₄⁺, NO₃⁻, and SO₄²⁻, respectively, identified by the SHapley Additive exPlanations approach. The light rain frequency rose by 2.6%–3.7% yr⁻¹ during 2010–2024, annually adding 0.036 kg N ha⁻¹ yr⁻¹ to nitrogen deposition since 2010 and 0.003 kg S ha⁻¹ yr⁻¹ to sulfur deposition since 2014. This study demonstrates how light rain critically governs atmospheric sulfur and nitrogen source-sink dynamics amid shifting emissions and climates.

Methanesulfonic acid (MSA), an acid molecule with properties similar to that of sulfuric acid (SA), has attracted increasing attention for its role in driving atmospheric new particle formation (NPF). Currently, ethanolamine (MEA) is recognized as the most promising atmospheric organic amine for promoting the formation of MSA-based clusters. Given the complexity of multi-component aerosol nucleation mechanisms, it is essential to explore the potential of other gaseous substances participating in the MSA-MEA-driven NPF. Formic acid (FA), the most abundant organic acid in both the atmospheric gas phase and particulate phase, warrants urgent investigation regarding its potential role in aerosol nucleation. Herein, we investigate the enhancement potential of FA on MSA-MEA-driven NPF within the troposphere. The results indicate that the enhancing effect of FA emerges in the lower troposphere (T ≤ 278.15 K) when [FA] ≥ 10¹⁰ cm⁻³. The enhancement strength, R_FA, increases with decreasing temperature and increasing FA concentration, reaching a factor of up to 21.54 at 258.15 K, and is most significant in regions with high MEA emissions. At 258.15 K, when [FA] ≥ 10¹¹ cm⁻³, FA can directly promote the MSA-MEA-FA growth pathway, rather than merely acting as a catalyst for the MSA-MEA pathway. Consequently, the ternary MSA-MEA-FA nucleation mechanism may play a crucial role in the NPF processes in cities with severe Industrial pollution, forested areas, industrial zones rich in volatile compounds, cold oceans, and polar regions.

We present a method for retrieving cloud optical depth that applies 3D radiative transfer to utilize the combination of polarimetry and multi-spectral imagery that is newly available from satellite missions such as the Plankton, Aerosol, Cloud, Ocean, Ecosystem (PACE) Mission. Due to the approximate spectral invariance of scattering by clouds, this combination of measurements is sensitive to the mean number of scattering events experienced by visible radiation. Using a hierarchy of synthetic cloud fields ranging from idealized cloud geometries, stochastically generated cloud fields with idealized microphysics, and those produced by Large Eddy Simulations (LES), we demonstrate that the combination of visible reflectance and the mean number of scattering events skillfully predicts the in-cloud mean of the optical depth at both 8 and 1 km resolution, with coefficients of determination exceeding 0.92 and 0.86, respectively. Further out-of-sample testing on LES cloud fields show that a multi-linear regression trained on stochastically generated cloud fields reduces the relative root-mean-square error from 29% under the plane-parallel homogeneous assumption to less than 14% at 6 km resolution. Biases in 1 km resolution retrievals of trade cumulus are reduced from −74% to −40%. Uncertainties from instrumentation and atmospheric correction add up to 20% additional uncertainty in cloud optical depth for the LES cloud fields. With this method, the PACE mission can provide the first global estimate of cloud optical depth that accounts for cloud heterogeneity.

Over recent decades, North African dust storms have undergone marked variability, reflecting complex interactions between regional climate processes and environmental change. Using four decades (1984–2023) of visibility-based observational records, we examine regional and seasonal trends in dust storm frequency across the Sahel and the Sahara, capturing their distinct dust dynamics. Results reveal a significant decline in dust activity in both regions, most pronounced during pre-monsoon (MAM) and monsoon (JJA) seasons in the Sahel, and during post-monsoon (SON) and dry season (DJF) in the Sahara. Integrating surface observations with local meteorology (precipitation, surface wind speed, vegetation) and climate indices (AMO, NAO, MEI), we find the Atlantic Multidecadal Oscillation (AMO) as the primary driver, with region-specific effects: in the Sahel, AMO-driven warming and rainfall increase vegetation, suppressing dust; in the Sahara, AMO intensifies the Saharan Heat Low (SHL) and elevates temperatures, modulating dust through atmospheric stability and wind patterns. Local meteorology further differentiates responses, with precipitation and Leaf Area Index (LAI) dominating dust variability in the Sahel, while SHL strength and surface winds are most influential in the Sahara. By explicitly separating the Sahel and Sahara and integrating multiple drivers, this study provides a more spatially resolved understanding of dust–climate link and suggests continued declines in North African dust storm activity under future warming. These findings offer critical constraints for improving dust emission projections in climate models.