Emission Monitoring Mobile Experiment (EMME): an overview and first results of the St. Petersburg megacity campaign 2019

Abstract

Abstract. Global climate change is one of the most important scientific, societal and economic contemporary challenges. Fundamental understanding of the major processes driving climate change is the key problem which is to be solved not only on a global but also on a regional scale. The accuracy of regional climate modelling depends on a number of factors. One of these factors is the adequate and comprehensive information on the anthropogenic impact which is highest in industrial regions and areas with dense population – modern megacities. Megacities are not only “heat islands”, but also significant sources of emissions of various substances into the atmosphere, including greenhouse and reactive gases. In 2019, the mobile experiment EMME (Emission Monitoring Mobile Experiment) was conducted within the St. Petersburg agglomeration (Russia) aiming to estimate the emission intensity of greenhouse (CO2, CH4) and reactive (CO, NOx) gases for St. Petersburg, which is the largest northern megacity. St. Petersburg State University (Russia), Karlsruhe Institute of Technology (Germany) and the University of Bremen (Germany) jointly ran this experiment. The core instruments of the campaign were two portable Bruker EM27/SUN Fourier transform infrared (FTIR) spectrometers which were used for ground-based remote sensing measurements of the total column amount of CO2, CH4 and CO at upwind and downwind locations on opposite sides of the city. The NO2 tropospheric column amount was observed along a circular highway around the city by continuous mobile measurements of scattered solar visible radiation with an OceanOptics HR4000 spectrometer using the differential optical absorption spectroscopy (DOAS) technique. Simultaneously, air samples were collected in air bags for subsequent laboratory analysis. The air samples were taken at the locations of FTIR observations at the ground level and also at altitudes of about 100 m when air bags were lifted by a kite (in case of suitable landscape and favourable wind conditions). The entire campaign consisted of 11 mostly cloudless days of measurements in March–April 2019. Planning of measurements for each day included the determination of optimal location for FTIR spectrometers based on weather forecasts, combined with the numerical modelling of the pollution transport in the megacity area. The real-time corrections of the FTIR operation sites were performed depending on the actual evolution of the megacity NOx plume as detected by the mobile DOAS observations. The estimates of the St. Petersburg emission intensities for the considered greenhouse and reactive gases were obtained by coupling a box model and the results of the EMME observational campaign using the mass balance approach. The CO2 emission flux for St. Petersburg as an area source was estimated to be 89 ± 28 ktkm-2yr-1, which is 2 times higher than the corresponding value in the EDGAR database. The experiment revealed the CH4 emission flux of 135 ± 68 tkm-2yr-1, which is about 1 order of magnitude greater than the value reported by the official inventories of St. Petersburg emissions (∼ 25 tkm-2yr-1 for 2017). At the same time, for the urban territory of St. Petersburg, both the EMME experiment and the official inventories for 2017 give similar results for the CO anthropogenic flux (251 ± 104 tkm-2yr-1 vs. 410 tkm-2yr-1) and for the NOx anthropogenic flux (66 ± 28 tkm-2yr-1 vs. 69 tkm-2yr-1).

Investigation of space-borne trace gas products over St. Petersburg and Yekaterinburg, Russia by using COCCON observations

“…It started to decrease from May to end of July, during which the growing season and the photosynthetic activities increase. Similar behaviour in 2019 was also observed by Timofeyev et al (2021) and in previous years by Timofeyev et al (2019) and Nikitenko et al (2020). The amount of XCO2 stays around 403 ppm between end of July and middle of September and starts to increase afterwards.…”

The CO<sub>2</sub> integral emission by the megacity of St Petersburg as quantified from ground-based FTIR measurements combined with dispersion modelling

“…Official inventory (bottom-up) estimates of the CO 2 emissions for St Petersburg may have significant uncertainties both in the estimates of integral emissions and in the data on the spatial and temporal distribution of the CO 2 fluxes. This suggestion is confirmed, in particular, by the significantly different values of the CO-to-CO 2 emission ratio (ER) for St Petersburg obtained by Makarova et al (2021) from the field measurements (ER CO/CO 2 ≈ 6 ppbv ppmv −1 , where ppbv is parts per billion by volume) and calculated using the official emission inventory data reported by Serebritsky (2018; ER CO/CO 2 ≈ 21 ppbv ppmv −1 ). The ER CO/CO 2 ratio is one of the most important characteristics of the source of air pollution, since its value can indicate the nature of the emission.…”

“…In 2019, the mobile experiment EMME (Emission Monitoring Mobile Experiment) was carried out on the territory of the St Petersburg agglomeration with the aim of estimating the emission intensity of greenhouse (CO 2 and CH 4 ) and reactive (CO and NO x ) gases for St Petersburg (Makarova et al, 2021). St Petersburg State University (Russia), the Karlsruhe Institute of Technology (Germany) and the University of Bremen (Germany) jointly prepared and conducted this city campaign.…”

Long-term column-averaged greenhouse gas observations using a COCCON spectrometer at the high-surface-albedo site in Gobabeb, Namibia

“…The CAMS model has been described previously in great detail, e.g., Agustí-Panareda et al (2014), Massart et al (2016) and Inness et al (2019). Here, we utilize the CAMS global inversion-optimized column-averaged DMFs for CO 2 and CH 4 .…”