Publications

Estimating stratospheric polar vortex strength using ambient ocean-generated infrasound and stochastics-based machine learning

Vorobeva, Ekaterina; Eggen, Mari Dahl; Midtfjord, Alise Danielle; Benth, Fred Espen; Hupe, Patrick; Brissaud, Quentin; Orsolini, Yvan Joseph Georges Emile G.; Näsholm, Sven Peter

There are sparse opportunities for direct measurement of upper stratospheric winds, yet improving their representation in subseasonal-to-seasonal prediction models can have significant benefits. There is solid evidence from previous research that global atmospheric infrasound waves are sensitive to stratospheric dynamics. However, there is a lack of results providing a direct mapping between infrasound recordings and polar-cap upper stratospheric winds. The global International Monitoring System (IMS), which monitors compliance with the Comprehensive Nuclear-Test-Ban Treaty, includes ground-based stations that can be used to characterize the infrasound soundscape continuously. In this study, multi-station IMS infrasound data were utilized along with a machine-learning supported stochastic model, Delay-SDE-net, to demonstrate how a near-real-time estimate of the polar-cap averaged zonal wind at 1-hPa pressure level can be found from infrasound data. The infrasound was filtered to a temporal low-frequency regime dominated by microbaroms, which are ambient-noise infrasonic waves continuously radiated into the atmosphere from nonlinear interaction between counter-propagating ocean surface waves. Delay-SDE-net was trained on 5 years (2014–2018) of infrasound data from three stations and the ERA5 reanalysis 1-hPa polar-cap averaged zonal wind. Using infrasound in 2019–2020 for validation, we demonstrate a prediction of the polar-cap averaged zonal wind, with an error standard deviation of around 12 m·s compared with ERA5. These findings highlight the potential of using infrasound data for near-real-time measurements of upper stratospheric dynamics. A long-term goal is to improve high-top atmospheric model accuracy, which can have significant implications for weather and climate prediction.

Estimating residential air pollution exposure among citizens in Oslo 1974-1998 using a geographical information system.

Gram, F.; Nafstad, P.; Håheim, L.L.

Estimating methane emissions in the Arctic nations using surface observations from 2008 to 2019

Wittig, Sophie; Berchet, Antoine; Pison, Isabelle; Saunois, Marielle; Thanwerdas, Joel; Martinez, Adrien; Paris, Jean-Daniel; Machida, Toshinobu; Sasakawa, Motoki; Worthy, Doug E.J.; Lan, Xin; Thompson, Rona Louise; Sollum, Espen; Arshinov, Mikhail

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.

Estimating High Resolution Surface PM2.5 Over Europe Using Satellite AOD Datasets, CAMS Forecast and Machine Learning

Shetty, Shobitha; Schneider, Philipp; Stebel, Kerstin; Hamer, Paul David; Kylling, Arve; Berntsen, Terje Koren

Estimating high resolution daily surface PM2.5 over Europe using CAMS PM forecast, satellite AOD, and a Machine Learning Model

Shetty, Shobitha; Schneider, Philipp; Hamer, Paul David; Stebel, Kerstin; Kylling, Arve; Berntsen, Terje Koren

Estimating emissions of per- and polyfluoroalkyl substances from imported consumer products. NILU F

Vestergren, R.; Cousins, I. T.; Herzke, D.

Estimating domestic wood burning emissions in Nordic countries using ambient air observations, receptor and dispersion modelling.

Denby, B.; Karl, M.; Laupsa, H.; Johansson, C.; Pohjola, M.; Karppinen, A.; Kukkonen, J.; Ketzel, M.; Wählin, P.

Estimating concentrations of B(a)P in Europe - population exposure and health effects.

Guerreiro, C.; Horalek, J.; de Leeuw, F.; Couvidat, F.

Estimating ambient concentrations of benzo(a)pyrene in Europe - population exposure and health effects.

Guerreiro, C.; Horálek, J.; de Leeuw, F.; Couvidat, F.

Estimates of global dew collection potential on artificial surfaces.

Vuollekoski, H.; Vogt, M.; Sinclair, V. A.; Duplissy, J.; Järvinen, H.; Kyrö, E.-M.; Makkonen, R.; Petäjä, T.; Prisle, N. L.; Räisänen, P.; Sipilä, M.; Ylhäisi, J.; Kulmala, M.

Estimates of European emissions of methyl chloroform using a Bayesian inversion method.

Maione, M.; Graziosi, F.; Arduini, J.; Furlani, F.; Giostra, U.; Blake, D. R.; Bonasoni, P.; Fang, X.; Montzka, S. A.; O'Doherty, S. J.; Reimann, S.; Stohl, A.; Vollmer, M. K.

Estimated dietary intake of PFOS due to consumption of fish from hot spot areas. NILU F

Klenow, S.; Heinemeyer, G.; Dellatte, E.; Herzke, D.