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Eight surface observation sites providing quasi-continuous measurements of atmospheric methane mixing ratios have been operated since the mid-2000's in Siberia. For the first time in a single work, we assimilate 1 year of these in situ observations in an atmospheric inversion. Our objective is to quantify methane surface fluxes from anthropogenic and wetland sources at the mesoscale in the Siberian lowlands for the year 2010. To do so, we first inquire about the way the inversion uses the observations and the way the fluxes are constrained by the observation sites. As atmospheric inversions at the mesoscale suffer from mis-quantified sources of uncertainties, we follow recent innovations in inversion techniques and use a new inversion approach which quantifies the uncertainties more objectively than the previous inversion systems. We find that, due to errors in the representation of the atmospheric transport and redundant pieces of information, only one observation every few days is found valuable by the inversion. The remaining high-resolution quasi-continuous signal is representative of very local emission patterns difficult to analyse with a mesoscale system. An analysis of the use of information by the inversion also reveals that the observation sites constrain methane emissions within a radius of 500 km. More observation sites than the ones currently in operation are then necessary to constrain the whole Siberian lowlands. Still, the fluxes within the constrained areas are quantified with objectified uncertainties. Finally, the tolerance intervals for posterior methane fluxes are of roughly 20 % (resp. 50 %) of the fluxes for anthropogenic (resp. wetland) sources. About 50–70 % of Siberian lowlands emissions are constrained by the inversion on average on an annual basis. Extrapolating the figures on the constrained areas to the whole Siberian lowlands, we find a regional methane budget of 5–28 TgCH4 for the year 2010, i.e. 1–5 % of the global methane emissions. As very few in situ observations are available in the region of interest, observations of methane total columns from the Greenhouse Gas Observing SATellite (GOSAT) are tentatively used for the evaluation of the inversion results, but they exhibit only a marginal signal from the fluxes within the region of interest.

The primary objective of this complex aerosol experiment was the measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the experiment during 2013: in spring, when the aerosol generation is maximal; in summer (July), when atmospheric boundary layer altitude and, hence, mixing layer altitude are maximal; and in late summer/early autumn, during the period of nucleation of secondary particles. Thus, independently obtained data on the optical, meteorological, and microphysical parameters of the atmosphere allow intercalibration and inter-complement of the data and thereby provide for qualitatively new information which explains the physical nature of the processes that form the vertical structure of the aerosol field.

Atmospheric precipitation introduces significant changes in the gamma background, making it difficult to analyze data from radiation monitoring systems. A criterion for identifying changes in the gamma background caused by atmospheric precipitation is proposed. Measurements of changes in the gamma background and the level of precipitation were performed at two independent observation sites. The time spectra of the gamma background were analyzed. The characteristic elements caused in the spectra by atmospheric precipitation are identified and classified. It is shown that the changes brought about in the gamma background by atmospheric precipitation can be identified according to the exponent of an exponential function describing the gamma background reduction following after the maximum is reached. If several consecutive peaks are present in the spectrum, identification is possible according to the gamma background reduction after the final peak.

This paper presents results of a comprehensive analysis of the formation of gases and aerosol composition during the anomalously hot April 2020 in Western Siberia. The analysis of the observed change in atmospheric composition and a modeling study with the WRF-Chem is carried out for suburban (TOR-station) and background (FON-station) areas. Two episodes of increased gases and aerosols were detected:13-15 April with a peak on 14 (in most part for the TOR station: increased NO, NO2, CO, CO2, aerosols) and 17-24 April with a peak on 23 (for both stations O3, aerosol, in most part for the FON station: NO2, SO2, CO, and CO2). Atmospheric circulation in the first episode was characterized by mesoscale differences between the two studied locations (surface temperature delta, although both stations are in the same region of large-scale transfers). For the second episode, a large scale atmospheric ridge was observed, which caused a transboundary transfer from Northern Kazakhstan and early wildfires. The simulation with WRF has demonstrated in most cases only the role of wildfires and, in general, has not demonstrated any observed differences between the two episodes. It shows that there is a need to search for more sensitive methods of discovering sources of pollution.

We have revised a calculation method of mole fractions and uncertainties for in situ CO2 and CH4 measurements with a working standard-gas-saving system. It uses on-site compressed air to track the baseline drift of sensors. The Japan–Russia Siberian Tall Tower Inland Observation Network (JR-STATION) is made up of this system, which was installed across nine different sites in Siberia. The system acquires semi-continuous data by alternating between sampling air from multiple altitudes through switched flow paths and recording several minutes of averaged data for each altitude. We estimated the sensor repeatability (ur) based on the measurement of on-site compressed air. The ur for CO2 and CH4 was mostly around 0.05 ppm and below 5 ppb, respectively. The combined standard uncertainties (uc(x)) of time-averaged ambient air measurements were sometimes higher than the ur for each period because the data included atmospheric variability during the measurement period of several minutes. Data users should consider the difference between the ur and uc(x) to select optimal data, depending on their focusing spatial scale. The CO2 and CH4 data measured with a non-dispersive infrared (NDIR) analyzer and a tin dioxide sensor (TOS) exhibited good agreement with those measured by cavity ring-down spectroscopy (CRDS).

The effect of aerosol loading on solar radiation and the subsequent effect on photosynthesis is a relevant question for estimating climate feedback mechanisms. This effect is quantified in the present study using ground-based measurements from five remote sites in boreal and hemiboreal (coniferous and mixed) forests of Eurasia. The diffuse fraction of global radiation associated with the direct effect of aerosols, i.e. excluding the effect of clouds, increases with an increase in the aerosol loading. The increase in the diffuse fraction of global radiation from approximately 0.11 on days characterized by low aerosol loading to 0.2–0.27 on days with relatively high aerosol loading leads to an increase in gross primary production (GPP) between 6 % and 14 % at all sites. The largest increase in GPP (relative to days with low aerosol loading) is observed for two types of ecosystems: a coniferous forest at high latitudes and a mixed forest at the middle latitudes. For the former ecosystem the change in GPP due to the relatively large increase in the diffuse radiation is compensated for by the moderate increase in the light use efficiency. For the latter ecosystem, the increase in the diffuse radiation is smaller for the same aerosol loading, but the smaller change in GPP due to this relationship between radiation and aerosol loading is compensated for by the higher increase in the light use efficiency. The dependence of GPP on the diffuse fraction of solar radiation has a weakly pronounced maximum related to clouds.

We use a regional chemistry transport model (Weather Research and Forecasting model coupled with chemistry, WRF-Chem) in conjunction with surface observations of tropospheric ozone and Ozone Monitoring Instrument (OMI) satellite retrievals of tropospheric column NO2 to evaluate processes controlling the regional distribution of tropospheric ozone over western Siberia for late spring and summer in 2011. This region hosts a range of anthropogenic and natural ozone precursor sources, and it serves as a gateway for near-surface transport of Eurasian pollution to the Arctic. However, there is a severe lack of in situ observations to constrain tropospheric ozone sources and sinks in the region. We show widespread negative bias in WRF-Chem tropospheric column NO2 when compared to OMI satellite observations from May–August, which is reduced when using ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) v5a emissions (fractional mean bias (FMB) = -0.82 to -0.73) compared with the EDGAR (Emissions Database for Global Atmospheric Research)-HTAP (Hemispheric Transport of Air Pollution) v2.2 emissions data (FMB = -0.80 to -0.70). Despite the large negative bias, the spatial correlations between model and observed NO2 columns suggest that the spatial pattern of NOx sources in the region is well represented. Scaling transport and energy emissions in the ECLIPSE v5a inventory by a factor of 2 reduces column NO2 bias (FMB = -0.66 to -0.35), but with overestimates in some urban regions and little change to a persistent underestimate in background regions. Based on the scaled ECLIPSE v5a emissions, we assess the influence of the two dominant anthropogenic emission sectors (transport and energy) and vegetation fires on surface NOx and ozone over Siberia and the Russian Arctic. Our results suggest regional ozone is more sensitive to anthropogenic emissions, particularly from the transport sector, and the contribution from fire emissions maximises in June and is largely confined to latitudes south of 60∘ N. Ozone dry deposition fluxes from the model simulations show that the dominant ozone dry deposition sink in the region is to forest vegetation, averaging 8.0 Tg of ozone per month, peaking at 10.3 Tg of ozone deposition during June. The impact of fires on ozone dry deposition within the domain is small compared to anthropogenic emissions and is negligible north of 60∘ N. Overall, our results suggest that surface ozone in the region is controlled by an interplay between seasonality in atmospheric transport patterns, vegetation dry deposition, and a dominance of transport and energy sector emissions.

The Arctic is a critical region in terms of global warming. Environmental changes are already progressing steadily in high northern latitudes, whereby, among other effects, a high potential for enhanced methane (CH4) emissions is induced. With CH4 being a potent greenhouse gas, additional emissions from Arctic regions may intensify global warming in the future through positive feedback. Various natural and anthropogenic sources are currently contributing to the Arctic's CH4 budget; however, the quantification of those emissions remains challenging. Assessing the amount of CH4 emissions in the Arctic and their contribution to the global budget still remains challenging. On the one hand, this is due to the difficulties in carrying out accurate measurements in such remote areas. Besides, large variations in the spatial distribution of methane sources and a poor understanding of the effects of ongoing changes in carbon decomposition, vegetation and hydrology also complicate the assessment. Therefore, the aim of this work is to reduce uncertainties in current bottom-up estimates of CH4 emissions as well as soil oxidation by implementing an inverse modelling approach in order to better quantify CH4 sources and sinks for the most recent years (2008 to 2019). More precisely, the objective is to detect occurring trends in the CH4 emissions and potential changes in seasonal emission patterns. The implementation of the inversion included footprint simulations obtained with the atmospheric transport model FLEXPART (FLEXible PARTicle dispersion model), various emission estimates from inventories and land surface models, and data on atmospheric CH4 concentrations from 41 surface observation sites in the Arctic nations. The results of the inversion showed that the majority of the CH4 sources currently present in high northern latitudes are poorly constrained by the existing observation network. Therefore, conclusions on trends and changes in the seasonal cycle could not be obtained for the corresponding CH4 sectors. Only CH4 fluxes from wetlands are adequately constrained, predominantly in North America. Within the period under study, wetland emissions show a slight negative trend in North America and a slight positive trend in East Eurasia. Overall, the estimated CH4 emissions are lower compared to the bottom-up estimates but higher than similar results from global inversions.

Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10–25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March–May (on about 30% of the days) and least frequently in December–February (about 10% of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01–10 cm􀀀3 s􀀀1) and the growth rate by about an order of magnitude (1–10 nm h􀀀1). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans

The vertical profiles of the O 3 , CO, CO 2 and CH 4 concentrations measured onboard the Optik Tu-134 aircraft laboratory and retrieved from data obtained with an IASI Fourier transform spectrometer operating aboard a MetOp satellite (European Space Agency) have been compared. This comparison shows that absolute differences between aircraft satellite ozone concentrations may vary from 55 to 15 ppb at the land surface and within the lower boundary layer and from 30 to −15 ppb at a height of 7000 m. Their relative differences range within 60 to 30% at a height of 500 m and 30 to −35% at a height of 7000 m. Absolute differences between aircraft and satellite carbon-monoxide concentrations may vary from 80 to 2300 ppb, while their relative differences range within −140 to 98%. For methane, the mean difference is maximal within the atmospheric boundary layer (90 ppb). According to the data on all profiles, the maximum and minimum differences reach 220 and 8 ppb, respectively, within the atmospheric boundary layer. Minimum differences range from zero at the land surface to −100 ppb in the upper troposphere. For carbon dioxide, the mean difference between the results of aircraft and satellite measurements ranges from −2 to −9 ppm. In the free troposphere, at a height of more than 3000 m, this difference is almost constant and amounts to −6 ppm. Over all flights, the maximum and minimum differences between aircraft and satellite CO 2 concentrations range from 14 to −4 ppm and from −7 to −16 ppm, respectively, within the atmospheric boundary layer. In this case, the maximum and minimum relative deviations over all flights amount to 3.4 and −4.2%, respectively, within the atmospheric boundary layer. These differences are significantly larger than those found earlier for the background conditions. It is necessary to improve the vertical gas distribution models used in the algorithms of satellite-data processing.