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On the seasonal variation in observed size distributions in northern Europe and their changes with decreasing anthropogenic emissions in Europe: climatology and trend analysis based on 17 years of data from Aspvreten, Sweden

In this study we explore 17 years of aerosol number size distribution data (10–390 nm) observed at Aspvreten (58.8° N, 17.4° E, 25 m a.s.l.). The station, located in northern Europe, is representative of rural background conditions. The study focused on identifying trends in aerosol number size distribution properties. The study shows that total number has decreased by 30 % and aerosol submicron mass by 50 % on average. Observed trends vary strongly with both season and particle size.

The diurnal cycle of the smoky marine boundary layer observed during August in the remote southeast Atlantic

Boundary layer (BL) semi-direct effects in the remote SE Atlantic are investigated using LASIC field measurements and satellite retrievals. Low-cloud cover and cloud liquid water path decrease with increasing smoke loadings in the BL. Daily-mean surface-based mixed layer is warmer by 0.5 K, moisture accumulates near the surface throughout the night, and the BL deepens by 200 m, with LWPs and cloud top heights increasing, in the sunlit morning hours, as part of the smoke-altered BL diurnal cycle.

Large-scale particulate air pollution and chemical fingerprint of volcanic sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Bárðarbunga volcano (Iceland)

This study, benefiting especially from recently developed mass spectrometry observations of aerosols, highlights unknown properties of volcanic sulfates in the troposphere. It shows their specific chemical fingerprint, distinct from those of freshly emitted industrial sulfates and background aerosols. We also demonstrate the large-scale persistence of the volcanic sulfate pollution over weeks. Hence, these results cast light on the impact of tropospheric eruptions on air quality and climate.

Relative impact of aerosol, soil moisture, and orography perturbations on deep convection

This study addresses the relative impact of orography, soil moisture, and aerosols on precipitation over Germany in different weather regimes. We find that the impact of these perturbations is higher for weak than for strong large-scale forcing. Furthermore, aerosols and soil moisture are both of similar importance for precipitation forecasting, which indicates that their inclusion in operational ensemble forecasting should be assessed in the future.

Assessing the formation and evolution mechanisms of severe haze pollution in the Beijing–Tianjin–Hebei region using process analysis

The formation mechanism of a severe haze episode that occurred over North China in December 2015, the aerosol radiative impacts on the haze event and the influence mechanism were examined. The PM_2.5 increase during the aerosol accumulation stage was mainly attributed to strong production by the aerosol chemistry process and weak removal by advection and vertical mixing. Restrained vertical mixing was the main reason for near-surface PM_2.5 increase when aerosol radiative feedback was considered.

Towards monitoring localized CO2 emissions from space: co-located regional CO2 and NO2 enhancements observed by the OCO-2 and S5P satellites

The quantification of anthropogenic emissions with current CO₂ satellite sensors is difficult, but NO₂ is co-emitted, making it a suitable tracer of recently emitted CO₂. We analyze enhancements of CO₂ and NO₂ observed by OCO-2 and S5P and estimate the CO₂plume cross-sectional fluxes that we compare with emission databases. Our results demonstrate the usefulness of simultaneous satellite observations of CO₂ and NO₂ as envisaged for the European Copernicus anthropogenic CO₂ monitoring mission

OCO-2 and S5P satellites">Read more

Quantification of water vapour transport from the Asian monsoon to the stratosphere

We investigate the transport pathways of water vapour from the upper troposphere in the Asian monsoon region to the stratosphere. In the employed chemistry-transport model we use a tagging method, such that the impact of different source regions on the stratospheric water vapour budget can be quantified. A key finding is that the Asian monsoon (compared to other source regions) is very efficient in transporting air masses and water vapour to the tropical and extratropical stratosphere.

Atmospheric measurements of the terrestrial O2:CO2 exchange ratio of a midlatitude forest

Predictions of global warming require predictions of how much CO₂ will be taken up by the oceans, how much by land plants, and how much will stay in the atmosphere. Measurements of atmospheric oxygen (O₂) help with these predictions if we also know the ratio of O₂ release to CO₂ uptake in land plants. We have measured this ratio in a midlatitude forest and find a lower value than the one in wide use. If truly applicable, our results call for a modest adjustment in the global carbon budget.

Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation

Effects of aerosols on clouds are important for climate studies but are among the largest uncertainties in climate projections. This study evaluates the skill of global models to simulate aerosol, cloud condensation nuclei (CCN) and cloud droplet number concentrations (CDNCs). Model results show reduced spread in CDNC compared to CCN due to the negative correlation between the sensitivities of CDNC to aerosol number concentration (air pollution) and updraft velocity (atmospheric dynamics).

Emission of trace gases and aerosols from biomass burning – an updated assessment

Biomass burning is one of the largest sources of atmospheric pollutants worldwide. This paper presents an up-to-date compilation of emission factors for over 120 trace gas and aerosol species from the different forms of open vegetation fires and domestic biofuel use, based on an analysis of over 370 published studies. Using these emission factors and current global burning activity data, the annual emissions of important species released by the various types of biomass burning are estimated.

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