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Climate change impacts the characteristics of the vegetation carbon-uptake process in the northern Eurasian terrestrial ecosystem. However, the currently available direct CO2 flux measurement datasets, particularly for central Siberia, are insufficient for understanding the current condition in the northern Eurasian carbon cycle. Here, we report daily and seasonal interannual variations in CO2 fluxes and associated abiotic factors measured using eddy covariance in a coniferous forest and a bog near Zotino, Krasnoyarsk Krai, Russia, for April to early June, 2013–2017. Despite the snow not being completely melted, both ecosystems became weak net CO2 sinks if the air temperature was warm enough for photosynthesis. The forest became a net CO2 sink 7–16 days earlier than the bog. After the surface soil temperature exceeded ~1 �C, the ecosystems became persistent net CO2 sinks. To change into the full spring photosynthesis recovery, the forest is likely to need a minimum accumulated air temperature of ~80 to 137 �C, and the bog requires 141 to 211 �C. During these periods, soil temperature in the forest still remained nearly 0 �C, suggesting that it is likely that forests appear more sensitive to the rise of air temperature than bogs. Net ecosystem productivity was highest in 2015 for both ecosystems because of the anomalously high air temperature in May compared with other years. Our findings demonstrate that long-term monitoring of flux measurements at the site level, particularly during winter and its transition to spring, is essential for understanding the responses of the northern Eurasian ecosystem to spring warming.
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.
The interannual variations in the characteristics of the seasonal cycle (annual and seasonal amplitudes, winter emission, dates of annual minimum and maximum, and phase) and in the growth rate of atmospheric carbon dioxide concentration over Central Siberia are analyzed for the period from May 2009 to January 2016. The results are based on the continuous monitoring of CO2 concentration at the Zotino Tall Tower Observatory (ZOTTO, www.zottoproject.org). It is found that the seasonal amplitude of CO2 concentration in the atmo spheric surface layer over Western Siberia is 26.4 ± 0.8 μmol/mol (no long-term trend toward its increase was revealed), the annual mean growth rate of CO2 is 2.34 μmol/mol per year, its variations range from 1 to 4 μmol/mol per year.
The Zotino Tall Tower Observatory in Central Siberia (ZOTTO, 60°48' N, 89°21' E) is an excellent location to monitor the continental carbon cycle. Since April 2009, a fully automated low maintenance measurement system based on a cavity ring-down spectroscopy (CRDS) analyzer is installed at the site to measure continuously carbon dioxide (CO2) and methane (CH4) from six heights up to 301 m a.g.l. Buffer volumes in each air line remove short term CO2 and CH4 mixing ratio fluctuations associated with turbulence, and allow continuous, near-concurrent measurements from all six tower levels. Instead of drying the air sample, the simultaneously measured water vapor is used to correct the dilution and pressure-broadening effects for the accurate determination of dry air CO2 and CH4 mixing ratios. The stability of the water vapor correction was demonstrated by repeated laboratory and field tests. The effect of molecular adsorption in the wet air lines was shown to be negligible. The low consumption of four calibration tanks that need recalibration only on decadal timescale further reduces maintenance. The measurement precision (accuracy) of 0.04 ppm (0.09 ppm) for CO2 and 0.3 ppb (1.5 ppb) for CH4 is compliant with the WMO recommendations. The data collected during the 2009 vegetation period reveals a seasonal cycle amplitude of 26.4 ppm at the 301 m level.
Aerosols produced by wildfires are a common phenomenon in boreal regions. For the Siberian taiga, it is still an open question if the effects of aerosols on atmospheric conditions increase net CO2 uptake or photosynthesis. We investigated the factors controlling forest net ecosystem productivity (NEP) and explored how clouds and smoke modulate radiation as a major factor controlling NEP during fire events in the years 2012 and 2013. To characterize the underlying mechanisms of the NEP response to environmental drivers, Artificial Neural Networks (ANNs) were trained by eddy covariance flux measurements nearby the Zotino Tall Tower Observatory (ZOTTO). Total photosynthetically active radiation, vapour pressure deficit, and diffuse fraction explain at about 54-58% of NEP variability. NEP shows a strong negative sensitivity to VPD, and a small positive to fdif. A strong diffuse radiation fertilization effect does not exist at ZOTTO forest due to the combined effects of low light intensity, sparse canopy and low leaf area index. Results suggests that light intensity and canopy structure are important factors of the overall diffuse radiation fertilization effect.
We present long-term (5-year) measurements of particulate matter with an upper diameter limit of ∼ 10 µm (PM10), elemental carbon (EC), organic carbon (OC), and water-soluble organic carbon (WSOC) in aerosol filter samples collected at the Zotino Tall Tower Observatory in the middle-taiga subzone (Siberia). The data are complemented with carbon monoxide (CO) measurements. Air mass back trajectory analysis and satellite image analysis were used to characterise potential source regions and the transport pathway of haze plumes. Polluted and background periods were selected using a non-parametric statistical approach and analysed separately. In addition, near-pristine air masses were selected based on their EC concentrations being below the detection limit of our thermal–optical instrument. Over the entire sampling campaign, 75 and 48 % of air masses in winter and in summer, respectively, and 42 % in spring and fall are classified as polluted. The observed background concentrations of CO and EC showed a sine-like behaviour with a period of 365 ± 4 days, mostly due to different degrees of dilution and the removal of polluted air masses arriving at the Zotino Tall Tower Observatory (ZOTTO) from remote sources. Our analysis of the near-pristine conditions shows that the longest periods with clean air masses were observed in summer, with a frequency of 17 %, while in wintertime only 1 % can be classified as a clean. Against a background of low concentrations of CO, EC, and OC in the near-pristine summertime, it was possible to identify pollution plumes that most likely came from crude-oil production sites located in the oil-rich regions of Western Siberia. Overall, our analysis indicates that most of the time the Siberian region is impacted by atmospheric pollution arising from biomass burning and anthropogenic emissions. A relatively clean atmosphere can be observed mainly in summer, when polluted species are removed by precipitation and the aerosol burden returns to near-pristine conditions.
Boreal wildfires are large sources of reactive trace gases and aerosols to the atmosphere, accounting for 20% of carbon emissions from global biomass burning. Siberian wildfires are a major extratropical source of carbon monoxide (CO), as well as a significant source of black carbon, smoke aerosols, and other climate-relevant atmospheric gas/particle species. Smoke particles released by Siberian wildfires could be tracked thousands of kilometers downwind in the entire Northern Hemisphere, perturbing regional to global radiation budgets by influencing light scattering and cloud microphysical processes. The boreal regions of the Northern Hemisphere are expected to experience the largest temperature increases, which will likely increase the severity and frequency of fires. Consequently, long-term continuous trace gas and aerosol measurements in central Siberia are vital for assessing the atmospheric impact of Siberian boreal fires on regional to global air quality and climate. Since 2006, the Zotino Tall Tower Facility (ZOTTO; www.zottoproject.org), a unique international research platform for large-scale climatic observations, is operational about 20 km west of the Yenisei river (60.8°N; 89.35°E). A 300 m-tall tower allows regular probing of the mixed part of the boundary layer, which is only moderately influenced by diurnal variations of local surface fluxes and thus, in comparison with surface layer, representative for a larger region. Our investigation of the wildfires' impact on surface air composition in Central Siberia is based on four years of CO/CO2/CH4 and aerosol particle mass data measured at 300 m a.g.l.. Episodes of atmospheric transport from wildfires upwind of the measurements site are identified based on ensembles of HYSPLIT backward trajectories and MODIS active fire products. The emission factors are calculated using the Carbon Mass Balance method. In an effort to simplify combustion to its most fundamental principles, the combustion efficiency (CE) is used to represent the completeness of combustion. The following general notion is applied: if the CE exceeds 90 %, a fire is typically in the flaming phase, whereas if CE is less than 85 % combustion is in the smoldering phase. Most fires can be considered as being in a "mixed" phase. Ideally, the emission ratios can be obtained by dividing the excess concentrations of trace gas species measured in a fire plume (e.g. CO, CO2) by the excess concentration of a measured reference gas from the data set. Ground-based CO and CO2 measurements in plumes from relatively distant fires can usually not be used to extract CO/CO2 emission ratios due to the uncertain contributions of biogenic CO2 from respiration to the plume air. We present our attempt to extract CO/CO2 relationships related to sources from statistical analysis of our data set. The burnt biomass load is taken from the Global Land Cover 2000 project and validated by our in situ data set. Finally, episodes of emissions from the wildfires identified at the given location and time are calculated with a simple bottom-up approach using the equation of Seiler and Crutzen.
The paper presents the result of a retrieval of tropospheric carbon monoxide (CO) from infrared hyperspectral observations of AIRS/AMSU on board AQUA. The retrieval method is based on a modified double differential approach derived from AIRS/AMSU observations of the Far Easten territory of Russia in the fire-dangerous period. The main advantages and practical suitability of the modified double differential approach are discussed. Comparisons with NASA carbon monoxide data and ground-based measurements are well correlated. Mathematical expectation of deviation is 7.8% and standard deviation is 10% for NASA carbon monoxide data. Mathematical expectation of deviation is 8.9% and standard deviation is 4.7% for ground-based measurements. The ground-based measurements were made in Central Siberia by Forest Institute of the Siberian Branch of the Russian Academy of Sciences. The modified double differential approach opens the way for new theoretical research using national satellite instruments of infrared spectroscopy. In future, we plan to use this retrieval method for other atmospheric gases observed by infrared Fourier spectrometers on Meteor-M satellites board.
Contributions of climatically significant natural and anthropogenic emission sources in northern Eurasia to seasonal carbon monoxide (CO) variations observed at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia in 2007–2011 have quantitatively been estimated using the GEOS-Chem chemical transport model. It is shown that the formation of a stable continental pollution plume from sources in Western Europe, European Russia and southern Siberia during winter plays an important role in the regional balance of surface CO and allows one to explain 55–80% of the amplitude of the CO annual cycle observed at the ZOTTO station (~70–90 ppbv). During the warm period, the effect of the anthropogenic factor is weakly pronounced, and the background concentration of CO is regulated, first and foremost, by the oxidation of biogenic volatile organic compounds and fire activity in the region.
We adapt general statistical methods to estimate the optimal error covariance matrices in a regional inversion system inferring methane surface emissions from atmospheric concentrations. Using a minimal set of physical hypotheses on the patterns of errors, we compute a guess of the error statistics that is optimal in regard to objective statistical criteria for the specific inversion system. With this very general approach applied to a real-data case, we recover sources of errors in the observations and in the prior state of the system that are consistent with expert knowledge while inferred from objective criteria and with affordable computation costs. By not assuming any specific error patterns, our results depict the variability and the inter-dependency of errors induced by complex factors such as the misrepresentation of the observations in the transport model or the inability of the model to reproduce well the situations of steep gradients of concentrations. Situations with probable significant biases (e.g., during the night when vertical mixing is ill-represented by the transport model) can also be diagnosed by our methods in order to point at necessary improvement in a model. By additionally analysing the sensitivity of the inversion to each observation, guidelines to enhance data selection in regional inversions are also proposed. We applied our method to a recent significant accidental methane release from an offshore platform in the North Sea and found methane fluxes of the same magnitude than what was officially declared.
Distinguishing between the various natural and anthropogenic sources contributing to methane surface fluxes is a prerequisite for closing the methane budget in Eurasian Boreal environments. Regional atmospheric inversions at a high resolution provide a mean for improving the inventories of methane emissions and the process-based models for land surface exchanges. Though promissing, the atmospheric approach relies on performant chemistry-transport models and a network of precise in-situ observation sites. The inversion then suffer from all the uncertainties within the model and the observations. In the Bayesian inversion framework, an advanced and objective understanding of the statistics of the errors in the inversion system (such as the transport, representation, aggregation or observation errors) is required. Acquiring such an understanding rises many theoretical and practical difficulties. In most previous inversion studies, the statistics of the errors are built relying on expert knowledge on the behaviour of the models and the inversion systems. In this work, optimal matrices of error covariances are computed using general statistical methods. The error statistics are optimally estimated with a minimal set of physical hypotheses on the patterns of errors. Complex patterns and correlations of errors are then entirely retrieved. The reliability of our method was first tested on a well-documented European domain with numerous observations and precise inventories. We assimilated the data from 13 observation sites with quasi-continuous measurements to infer the European anthropogenic fluxes during a period of two weeks in March-April 2012. Errors caused by mis-representations in the transport model or by its inability to reproduce the situations of steep gradients in the air mass composition were retrieved. An analysis of the sensitivity of the inversion to each individual observation suggested guidelines for the selection of data in regional inversions. With this simple but efficient and optimal inversion system applied to a domain covering most of Siberia and Scandinavia, we inquire into the possibility of retrieving improved knowledge on the Eurasian Boreal methane fluxes.
There is a considerable shortage of direct observations of atmospheric trace gases in low-populated regions of Siberia. Since March, 2007 till now continuous measurements of O3, NOx, NO and NO2 concentrations have been performed at ZOTTO station in the middle of Krasnoyarsky Krai (60 N, 90 E) with 10 sec timing. Observations are completely automated and are part of scientific program on atmospheric chemistry measurements of ZOTTO Consortium headed by Max Planck Institute for Biogeochemistry, Jena. Variations of ozone concentration reveal vivid seasonal and daily features which have been analyzed and compared to other mid-latitude background stations as well as to data of TROICA train-based observations. These variations are likely to be typical for the Northern Eurasia boreal zone. Seasonal spring maximum (40-50 ppbv) is caused by stratospheric ozone intrusions that are only considerable ozone source. Smaller variations can be induced both by local factors and long-range transport of ozone precursors from pollution sources. The largest ozone formation rate has been observed in summer time from 9 a.m. till 3 p.m. of local time and made up 1-2 ppbv/hour. Such value points out on quite low photochemical activity and ambient air oxidizing ability. NOx concentration does not exceed 1 ppb that is typical for background areas but may vary by order and some more in few hours. Higher surface NOx(=NO+NO2) concentrations during day time generally correspond to higher ozone when NO/NO2 ratio indicates on clean or slightly polluted conditions. Analysis on base of Lagrangian model for evaluation of air parcel trajectories basing on NCEP final analysis meteorological fields and Russian Federation Hydrometeocenter reanalysis fields and residence time statistics has shown that most probable sources of man-made emissions influencing the Central Siberia air are located on south of Siberia (Kemerovo, Novokuznetsk, Krasnoyarsk, Tomsk, Novosibirsk). These results have been verified by CO data provided Max Planck Institute for Chemistry, Mainz, and agreement was very good. Data of TROICA-11, 12, 13 campaigns which occurred correspondingly in summer of 2007, 2008 and 2009 have been used to analyze pollution sources located along the Trans-Siberian Railroad. Measurements of volatile organic compounds by proton mass-spectrometry (PTR-MS) in 2008 and 2009 have been also considered to assess concentrations of biogenic VOCs (isoprene and monoterpenes) for dark-coniferous forests zone. Some of man-made VOCs (aromatic hydrocarbons and formaldehyde) were measured at ZOTTO in 2008 and in 2009 and are also presented in this study. The work was supported by Russian Foundation for Basic Research (Project # 08-05-13589).
We present inverse modelling (top-down) estimates of European methane (CH4) emissions for 2006–2012 based on a new quality-controlled and harmonized in-situ data set from 18 European atmospheric monitoring stations. We applied an ensemble of seven inverse models and performed four inversion experiments, investigating the impact of different sets of stations and the use of a priori information on emissions. The inverse models infer total CH4 emissions of 26.7 (20.2–29.7) Tg CH4 yr−1 (mean, 10th and 90th percentiles from all inversions) for the EU-28 for 2006–2012 from the four inversion experiments. For comparison, total anthropogenic CH4 emissions reported to UNFCCC (bottom-up, based on statistical data and emissions factors) amount to only 21.3 Tg CH4 yr−1 (2006) to 18.8 Tg CH4 yr−1 (2012). A potential explanation for the higher range of top-down estimates compared to bottom-up inventories could be the contribution from natural sources, such as peatlands, wetlands, and wet soils. Based on seven different wetland inventories from the Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) total wetland emissions of 4.3 (2.3–8.2) CH4 yr−1 from EU-28 are estimated. The hypothesis of significant natural emissions is supported by the finding that several inverse models yield significant seasonal cycles of derived CH4 emissions with maxima in summer, while anthropogenic CH4 emissions are assumed to have much lower seasonal variability. Furthermore, we investigate potential biases in the inverse models by comparison with regular aircraft profiles at four European sites and with vertical profiles obtained during the Infrastructure for Measurement of the European Carbon Cycle (IMECC) aircraft campaign. We present a novel approach to estimate the biases in the derived emissions, based on the comparison of simulated and measured enhancements of CH4 compared to the background, integrated over the entire boundary layer and over the lower troposphere. This analysis identifies regional biases for several models at the aircraft profile sites in France, Hungary and Poland.
Der Band behandelt die deutsch-russische Zusammenarbeit bei der wissenschaftlichen Erforschung Nordostsibiriens und des angrenzenden arktischen Meeres. Die wissenschaftlichen Beziehungen in dieser Forschungsregion besitzen eine lange Tradition, die in einem ausführlichen historischen Essay von Jörn Thiede dargestellt wird. Die kurzen Forschungsbeiträge stammen überwiegend von jungen Wissenschaftlern und sind in Gemeinschaftsarbeit von russischen und deutschen Forschern entstanden. Sie umfassen grundlegende Fragen der Geographie und Geologie des nordöstlichen Sibiriens. (2014, 198 Seiten, 73 Abbildungen, 7 Tabellen, 23.95 Euro, ISBN: 978-3-8047-3242-1, ISSN: 0369-5034)
The gradient measurements of the concentration of atmospheric carbon dioxide and methane in the middle taiga subzone of the Yenisei region of Siberia based on five years monitoring (2009–2014) at the ZOTTO Observatory are presented. The features of changing of the content of carbon dioxide and methane in the profile heights up to 301 meters is explained by both daily and seasonal specificity of functioning of terrestrial ecosystems and atmospheric processes. It is shown that in the cold season CO2 and CH4 concentrations in the surface atmosphere change synchronously and are determined by their sources and weather conditions. The results of measurements of methane concentration are compared with those obtained in other areas of Siberia on similar latitude and with measurements on background stations of Russia.
The results of measurements of ground CO2 concentration in the middle taiga subzone of the Yenisei region of Siberia (the ZOTTO observatory) in 2009 to 2012 are presented. Specific features of CO2 variability over the altitude profile up to 301 m are accounted for by specific diurnal and seasonal features in the functioning of terrestrial ecosystems as well as by atmospheric processes. It has been shown that the significance of regional and global components increases with elevation, while the contribution of the underlying surface in the region of the observatory decreases. The observed gradient differences between CO2 concentrations recorded at the onset and at the end of the cold period are explained by seasonal changes in the height of the atmospheric boundary layer. Comparison of data obtained at the ZOTTO observatory and at monitoring stations in Canada and the North Atlantic has shown that general trends in the seasonal variability of CO2 are similar and that specific features of the processes under study are dependent on biogeographic characteristics of the study regions.
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 international Pan-Eurasian Experiment (PEEX) program addresses the full spectrum of problems related to climate change in Eurasian Northern latitudes. All PEEX activities rely on the bulk of high-quality observational data provided by the ground and marine stations, remote sensing and satellite tools. So far, no coordinated station network has ever existed in Eurasia, moreover, the current scope of relevant research remains largely unknown as no prior assessment has been done to date. This paper makes the first attempt to overview the existing ground station pool in the Arctic-Boreal region with the focus on Russia. The geographical, climatic and ecosystem representativeness of the current stations is discussed, the gaps are identified and tentative station network developments are proposed.
The boreal and arctic zones of Siberia housing the large amounts of carbon stored in the living biomass of forests and wetlands, as well as in soils and specifically permafrost, play a crucial role in earth's global carbon cycle. The long-term studies of greenhouse gases (GHG) concentrations are important instruments to analyze the response of these systems to climate warming. In parallel to GHG observations, the measurements of their stable isotopic composition can provide useful information for distinguishing contribution of individual GHG source to their atmospheric variations, since each source has its own isotopic signature. In this study we report first results of laboratory analyses of the CO 2 and CH 4 concentrations, the stable isotope ratio of δ 13 C-CO 2 , δ 18 O-CO 2 , δ 13 C-CH 4 , δD-CH 4 measured in one-liter glass flasks which were obtained from 301 height of ZOTTO (Zotino Tall Tower Observatory, near 60˚N, 90˚E, about 20 km west of the Yenisei River) during 2008 – 2013 and 2010 – 2013 for stable isotope composition of CO2 and CH4 .