Disentangling methane and carbon dioxide sources and transport across the Russian Arctic from aircraft measurements

A more accurate characterization of the sources and sinks of methane (CH4) and carbon dioxide (CO2) in the vulnerable Arctic environment is required to better predict climate change. A large-scale aircraft campaign took place in September 2020 focusing on the Siberian Arctic coast. CH4 and CO2 were measured in situ during the campaign and form the core of this study. Measured ozone (O3) and carbon monoxide (CO) are used here as tracers. Median CH4 mixing ratios are fairly higher than the monthly mean hemispheric reference (Mauna Loa, Hawaii, US) with 1890&ndash;1969 ppb vs 1887 ppb respectively, while CO2 mixing ratios from all flights are lower (408.09&ndash;411.50 ppm vs 411.52 ppm). We also report on three case studies. Our analysis suggests that during the campaign the European part of Russia&rsquo;s Arctic and Western Siberia were subject to long-range transport of polluted air masses, while the East was mainly under the influence of local emissions of greenhouse gases. The relative contributions of the main anthropogenic and natural sources of CH4 are simulated using the Lagrangian model FLEXPART in order to identify dominant sources in the boundary layer and in the free troposphere. In western terrestrial flights, air masses composition is influenced by emissions from wetlands and anthropogenic activities (waste management, fossil fuel industry and to a lesser extent the agricultural sector), while in the East, emissions are dominated by freshwaters, wetlands, and the oceans, with a likely contribution from anthropogenic sources related to fossil fuels. Our results highlight the importance of the contributions from freshwater and oceans emissions. Considering the large uncertainties associated to them, our study suggests that the emissions from these aquatic sources should receive more attention in Siberia.</p

The Energy Model of Urban Heat Island

Despite the fact that the presence of a heat island over a city was established quite a long time ago, now there is no versatile algorithm for the determination of the urban heat island intensity. The proposed models either take into account only one or several factors for the formation of an urban heat island or do not consider physical reasons for the difference in thermodynamic conditions between a city and countryside. In this regard, it is impossible to make a forecast and determine the optimal methods for reducing the urban heat island intensity for an arbitrarily chosen city in a wide range of its characteristics and climatic conditions. This paper studies the causes for the formation of an urban heat island in order to develop the quantitative model of this process through the determination of the difference in radiation fluxes of various nature between a city and countryside (background area). A new equation allowing the intensity of an urban heat island in different seasons and different times of day, as well as under various atmospheric conditions, to be calculated from meteorological parameters measured at a stationary observation station is proposed. The model has been tested through the comparison of the results of numerical simulation with direct measurements of the heat island in Tomsk with a mobile station. It is shown that the main contributors to the formation of the heat island in Tomsk are anthropogenic heat emissions (80&ndash;90% in winter, 40&ndash;50% in summer) and absorption of shortwave radiation by the urban underlying surface (5&ndash;15% in winter, 40&ndash;50% summer). The absorption of longwave radiation by the urban underlying surface, absorption by atmospheric water vapor and other constituents, and heat consumption for evaporation are insignificant. An increase in the turbulent heat flux is responsible for the outflow of 40&ndash;50% of absorbed energy in summer and 20&ndash;30% in winter

Towards improved quantification of Russian oil and gas extraction emissions based on analysis of YAK-AEROSIBaircraft data

International audienc

Atmospheric methane over Siberia: measurements from the 2014 YAK-AEROSIB aircraft campaign

International audienceThe YAK-AEROSIB program collects high-precision in-situ measurements of the vertical distribution of CO2, CH4, CO, O3, black carbon and ultrafine particles distribution in the Siberian troposphere, as well as other parameters including aerosol lidar profiles, on a pan-Siberian aircraft transect. Recent efforts aim at better understanding the respective role of CH4 emission processes in driving its large scale atmospheric variability over the region. The October 2014 YAK-AEROSIB/MOCA campaign from Novosibirsk to Salekhard and over the Kara sea and the Yamal peninsula sampled air masses affected by local, regional and remote pollution. We analyse the contribution of local anthropogenic sources to measured CH4 enhancements, in relation to atmospheric mixing and transport conditions. Our analysis also attempts to detect CH4 signal from sources of methane in the Siberian shelf and the Arctic ocean during low level flight legs over the Kara sea using the airborne measurements and a Lagrangian model coupled to potential CH4 hydrate and geological sources. The measured CH4 concentrations do not contradict a potential source upstream of our measurements, but the interpretation is challenging due to a very low CH4 signal. The challenging question of the methane budget and its evolution in Siberia leads to a need for new approaches. A new generation of airborne measurements, more flexible, is now needed

Tropospheric ozone over Siberia in spring 2010: remote influences and stratospheric intrusion

International audienceWe have identified and characterised different factors influencing the tropospheric ozone over Siberia during spring 2010. This was done by analysing in-situ measurements of ozone, carbon dioxide, carbon monoxide, and methane mixing ratios measured by continuous analysers during an intensive airborne measurement campaign of the YAK-AEROSIB project, carried out between 15 and 18 April 2010. The analysis and interpretation of the observations, spanning 3000 km and stretching from 800 to 6700 m above ground level, were enhanced using the Lagrangian model FLEXPART to simulate backward air mass transport. The analysis of trace gas variability and simulated origin of air masses showed that plumes coming from east and west of the west Siberian plain and from north-eastern China related to biomass burning and anthropogenic activity had enhanced ozone mixing ratios during transport. In one case, low ozone mixing ratios were observed over a large region in the upper troposphere above 5500 m. The air mass was transported from the marine boundary layer over the Norwegian Sea where O3 background concentrations are low in the spring. The transport was coherent over thousands of kilometres, with no significant mixing with mid-upper troposphere air masses rich in O3. Finally, the stratospheric source of ozone to the troposphere was observed directly in a well-defined stratospheric intrusion. Analysis of this event suggests an input of 2.56±0.29×107 kg of ozone associated with a regional downward flux of 9.75±2.9×1010 molecules cm−2 s−1, smaller than hemispheric climatology