Sam-Erik Walker

Scientist

+47 63 89 80 83

+47 997 00 159

Urban Environment and Industry

Kjeller

sew@nilu.no

Cristin

Sam-Erik Walker holds an M.Sc. in Statistics and a B.Sc. in Computer Science from the University of Oslo.

He has over 30 years of experience developing and applying air pollution dispersion models for cities and urban areas and analysing air quality data using various numerical and statistical tools and methods. These include deterministic and probabilistic methods for model evaluation and validation, data assimilation, ensemble modelling, and data fusion to combine air quality observations with model results. He is one of the principal authors of several of the present models at NILU, including the urban air pollution dispersion model EPISODE.

He is also the leading developer behind the AirGAM trend and prediction model at NILU. This model enables the estimation of meteorology-adjusted long-term trends of air pollutants such as NO2, O3, PM, and VOCs at air quality stations in Norway and Europe. It has been used to quantify the effects of lockdowns during the recent COVID-19 pandemic and for estimating long-term trends for all EEA stations in Europe.

Recently, he developed the AirRisk model, a risk assessment model to quantify the risk or probability of exceeding limit values of NO2 and PM in connection with recent assessment studies in various Norwegian cities and urban areas, including Lørenskog, Drammen, and Oslo.

He actively disseminates scientific knowledge by writing reports and papers and regularly participates in scientific conferences. His primary motivation for working at NILU is to contribute to a cleaner world.

Sam-Erik Walker has 124 publications at NILU:

Nordiske perspektiver på vedfyring – utslipp og tiltak nå og mot 2030

Grythe, Henrik; Lopez-Aparicio, Susana; Markelj, Miha; Walker, Sam-Erik

2024

Trafikk- og luftkvalitetsberegninger i forbindelse med ny tiltaksutredning for bedre luftkvalitet i Oslo og Bærum 2025-2030. Beregningsresultater for Oslo

Weydahl, Torleif; Walker, Sam-Erik; Markelj, Miha; Andersen, André

2024

Exploring the connection between COVID19, the energy crisis and PM2.5 emissions from residential heating

Lopez-Aparicio, Susana; Grythe, Henrik; Markelj, Miha; Evangeliou, Nikolaos; Walker, Sam-Erik

2024

Scientific journal publication

Decoding temporal patterns and trends of PM10 pollution over Delhi: a multi-year analysis (2015–2022)

Chetna, NN; Dhaka, Surendra K.; Walker, Sam-Erik; Rawat, Vikas; Singh, Narendra

2024

Scientific journal publication

Long-term meteorology-adjusted and unadjusted trends of PM2.5 using the AirGAM model over Delhi, 2007–2022

Chetna, NN; Dhaka, Surendra K.; Walker, Sam-Erik; Rawat, Vikas; Singh, Narendra

2024

Scientific journal publication

Screening Programme 2022. New environmental pollutants.

Gundersen, Cathrine Brecke; Reid, Malcolm; Rostkowski, Pawel; Bæk, Kine; Rundberget, Thomas; Vogelsang, Christian; Rødland, Elisabeth; Beylich, Bjørnar; Eikenes, Heidi; Bäcklund, Are; Walker, Sam-Erik; Borgen, Anders Røsrud; Nikiforov, Vladimir; Håland, Alexander; Schmidbauer, Norbert

2023

Long-term Meteorology-Adjusted and Unadjusted Trends of PM2.5 Using the AirGAM Model Over Delhi, 2007–2022

Dang, Chetna; Dhaka, S K; Walker, Sam-Erik; Longiany, Gagandeep; Rawat, Wikas

2023

VOC measurements 2021

Solberg, Sverre; Claude, Anja; Reimann, Stefan; Walker, Sam-Erik

2023

Revidert tiltaksutredning for lokal luftkvalitet i Drammen kommune

Weydahl, Torleif; Markelj, Miha; Walker, Sam-Erik; Høyem, Harald

2023

Tiltaksutredning for lokal luftkvalitet i Lørenskog kommune

Høiskar, Britt Ann Kåstad; Walker, Sam-Erik; Weydahl, Torleif; Markelj, Miha; Andersen, André; Lopez-Aparicio, Susana; Grythe, Henrik

2023

The AirGAM 2022r1 air quality trend and prediction model

Walker, Sam-Erik; Solberg, Sverre; Schneider, Philipp; Guerreiro, Cristina

2023

Scientific journal publication

VOC measurements 2020

Solberg, Sverre; Claude, Anja; Reimann, Stefan; Sauvage, Stéphane; Walker, Sam-Erik

2022

Understanding Air Quality Trends in Europe. Focus on the relative contribution of changes in emission of activity sectors, natural fraction and meteorological variability.

Colette, Augustin; Solberg, Sverre; Aas, Wenche; Walker, Sam-Erik

2021

Appropriate Assimilation Methods for Air Quality Prediction and Pollutant Emission Inversion. An Urban Data Assimilation Systems Report.

Hamer, Paul David; Walker, Sam-Erik; Schneider, Philipp

2021

Quantifying the Impact of the Covid-19 Lockdown Measures on Nitrogen Dioxide Levels throughout Europe

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp; Guerreiro, Cristina

2021

Scientific journal publication

Revidert tiltaksutredning for lokal luftkvalitet i Stavanger kommune

Weydahl, Torleif; Johnsrud, Mona; Vo, Dam Thanh; Walker, Sam-Erik; Høiskar, Britt Ann Kåstad; Ranheim, Patrick

2020

Air quality in Europe – 2020 report

Ortiz, Alberto González; Guerreiro, Cristina; Soares, Joana; Antognazza, Frederico; Gsella, Artur; Houssiau, Michel; Liberti, Luca; Lükewille, Anke; Öztürk, Evrim; Horálek, Jan; Banyuls, Lorena; Targa, Jaume; Schneider, Philipp; Solberg, Sverre; Walker, Sam-Erik; Colette, Augustin

2020

The urban dispersion model EPISODE v10.0 – Part 1: An Eulerian and sub-grid-scale air quality model and its application in Nordic winter conditions

Hamer, Paul David; Walker, Sam-Erik; Sousa Santos, Gabriela; Vogt, Matthias; Vo, Dam Thanh; Lopez-Aparicio, Susana; Schneider, Philipp; Ramacher, Martin O. P.; Karl, Matthias

2020

Scientific journal publication

A presentation of the EPISODE urban scale air quality model and its application to Nordic winter conditions

Hamer, Paul David; Walker, Sam-Erik; Sousa Santos, Gabriela; Vogt, Matthias; Vo, Dam Thanh; Lopez-Aparicio, Susana; Ramacher, Martin O. P.; Karl, Matthias

2020

Part of book/report

Hvordan har luftkvalitet i Europa endret seg under lockdown og hvorfor?

Guerreiro, Cristina; Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp

2020

Networks of air quality sensors and their use for high-resolution mapping of urban air quality

Schneider, Philipp; Castell, Nuria; Hamer, Paul David; Walker, Sam-Erik; Bartonova, Alena

2020

Statistical modelling for long-term trends of pollutants – Use of a GAM model for the assessment of measurements of O3, NO2 and PM

Solberg, Sverre; Walker, Sam-Erik; Guerreiro, Cristina; Colette, Augustin

2020

A study of the relative expanded uncertainty formula for comparing low-cost sensor and reference measurements

Walker, Sam-Erik; Schneider, Philipp

2020

Tiltaksutredning for lokal luftkvalitet i Tromsø

Weydahl, Torleif; Walker, Sam-Erik; Johnsrud, Mona; Vo, Dam Thanh; Ranheim, Patrick

2019

Trends in measured NO2 and PM. Discounting the effect of meteorology.

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp

2019

Monitoring of greenhouse gases and aerosols at Svalbard and Birkenes in 2018. Annual report.

Myhre, Cathrine Lund; Svendby, Tove Marit; Hermansen, Ove; Lunder, Chris Rene; Platt, Stephen Matthew; Fiebig, Markus; Fjæraa, Ann Mari; Hansen, Georg Heinrich; Schmidbauer, Norbert; Krognes, Terje; Walker, Sam-Erik

2019

The Eulerian urban dispersion model EPISODE – Part 2: Extensions to the source dispersion and photochemistry for EPISODE–CityChem v1.2 and its application to the city of Hamburg

Karl, Matthias; Walker, Sam-Erik; Solberg, Sverre; Ramacher, Martin O. P.

2019

Scientific journal publication

Focused model selection and inference using robust estimators.

Walker, Sam-Erik; Hjort, Nils Lid

2018

Monitoring of greenhouse gases and aerosols at Svalbard and Birkenes in 2017 – Annual report

Myhre, Cathrine Lund; Svendby, Tove Marit; Hermansen, Ove; Lunder, Chris Rene; Platt, Stephen Matthew; Fiebig, Markus; Fjæraa, Ann Mari; Hansen, Georg Heinrich; Schmidbauer, Norbert; Krognes, Terje; Walker, Sam-Erik

2018

Discounting the effect of meteorology on trends in surface ozone: Development of statistical tools

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp; Guerreiro, Cristina; Colette, Augustin

2018

Bedre byluft. Endringer i 2014 og forskningsresultater av prognoser for meteorologi og luftkvalitet i norske byer vinteren 2013-2014.

Denby, B.R.; Sundvor, I.; Süld, J.; Kristensen, A.; Vallejo, I.; Walker, S.E.

2015

Modelling atmospheric oxidation of 2-aminoethanol (MEA) emitted from post-combustion capture using WRF-Chem.

Karl, M.; Svendby, T.; Walker, S.-E.; Velken, A.S.; Castell, N.; Solberg, S.

2015

Scientific journal publication

Data assimilation and statistical post-processing for numerical air quality predictions.

Steinbakk, G. H, Thorarinsdottir, T. L.; Lahoz, W. A.; Walker, S.-E.

2014

Method and tool selection within the pilot study of air quality in Poland: Data fusion methodologies.

Karl, M.; Walker, S.-E.

2014

Ensemble based probabilistic forecasting of meteorology and air quality in Oslo, Norway.

Walker, S.E.

2014

Uncertainties in assessing the environmental impact of amine emissions from a CO2 capture plant.

Karl, M.; Castell, N.; Simpson, D.; Solberg, S.; Starrfelt, J.; Svendby, T.; Walker, S.-E.; Wright, R.F.

2014

Scientific journal publication

Using UncertWeb for improved decision making. UncertWeb Consortium Deliverable 3.5.

Heuvelink, G.; Helle, K.; Pebesma, E.; Rasouli, S.; Stasch, C.; Truong, P.; Walker, S.E.

2013

Report on integrating the traffic/individual modelling with the air quality modelling. UncertWeb Consortium Deliverable 8.3.

Gerharz, L.; Helle, K.; Pebesma, E.; Pross, B.; Stasch, C.; Rasouli, S.; Timmermans, H.; Denby, B.; Walker, S.E.

2013

Validation of UncertWeb: Air quality forecasting. UncertWeb Consortium Deliverable 6.3.

Walker, S.E.; Denby, B.; Pross, B.; Cornford, D.

2013

Time series analysis of significant wave height data for identification of trends in the ocean wave climate.

Vanem, E.; Walker, S.E.

2013

Part of book/report

Identifying trends in the ocean wave climate by time series analyses of significant wave heightdata.

Vanem, E.; Walker, S.E.

2013

Scientific journal publication

Probabilistic forecasting of air quality in Oslo. UncertWeb Consortium Deliverable 6.2.

Walker, S.E.; Cornford, D.

2012

Ensemble based probabilistic forecasting of air quality in Oslo and Rotterdam.

Walker, S.E.; Denby B.R.; Castell-Balaguer, N.

2012

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2011

Scientific journal publication

NO2 calculations for 2010 and 2025 in Oslo and Bærum. Contribution from diesel cars and possible precautions.

Sundvor, I.; Tarrasón, L.; Walker, S-E.; Tønnesen, D.

2011

Calculation of dispersion and deposition, April 2009 – April 2010. Environmental surveillance of emissions to air from Snøhvit-Hammerfest LNG.

Liu, L.; Walker, S.E.; Hak, C.; Gjerstad, K.I.

2011

Data assimilation within the Air4EU project: the Athens case.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2011

Scientific journal publication

Towards uncertainty mapping in air-quality modelling and assessment.

Denby, B.; Dudek, A.; Walker, S.E.; Costa, A.M.; Monteiro, A.; van den Elshout, S.; Fisher, B.

2011

Scientific journal publication

The NILU SURFEX-EnKF land data assimilation system.

Lahoz, W.; Svendby, T.; Walker, S.-E.; Mahfouf, J.-F.

2010

Part of book/report

Ambient air pollution exposure, residential mobility and term birth weight in Oslo, Norway.

Madsen, C.; Gehring, U.; Walker, S.E.; Brunekreef, B.; Stigum, H.; Næss, Ø.; Nafstad, P.

2010

Scientific journal publication

The NILU SURFEX-EnKF land data assimilation system.

Lahoz, W.; Walker, S.-E.; Dammann, D.

2010

Evaluation and inter-comparison of open road line source models currently in use in the Nordic countries.

Berger, J.; Walker, S.-E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Härkönen, J.; Nikmo, J.; Karppinen, A.

2010

Scientific journal publication

Ambient air pollution exposure, residential mobility and term birth weight in Oslo, Norway.

Madsen, C.; Gehring, U.; Walker, S.E.; Brunekreef, B.; Stigum, H.; Næss, Ø.; Nafstad, P.

2009

Scientific journal publication

Modelling long-term averages of local ambient air pollution in Oslo, Norway: evaluation of nitrogen dioxide, PM10 and PM2.5.

Oftedal, B.; Walker, S.E.; Gram, F.; Mc Innes, H.; Nafstad, P.

2009

Scientific journal publication

Evaluation and inter-comparison of open road line source models currently in use in the Nordic countries.

Berger, J.; Walker, S.E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Härkonen, J.; Nikmo, J.; Karppinen, A.

2008

Scientific journal publication

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2008

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2008

Scientific journal publication

Residential outdoor air pollution and lung function in schoolchildren.

Oftedal, B.; Brunekreef, B.; Nystad, W.; Madsen, C.; Walker, S.E.; Nafstad, P.

2008

Scientific journal publication

Quantification of uncertainties associated with an integrated Gaussian line source model using ensembles.

Walker, S.E.

2007

Application of data assimilation in open road line source modelling. Case study Oslo II.

Walker, S.E.; Berger, J.

2007

Data assimilation within the Air4EU project: the Athens case. Powerpoint presentation.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2007

Data assimilation within the Air4EU project: the Athens case.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2007

Part of book/report

Quantification of uncertainties associated with an integrated Gaussian line source model using ensembles.

Walker, S.E.

2007

Part of book/report

Evaluation and inter-comparison of open road line source (ORLS) models currently being used in the Nordic countries. Powerpoint presentation.

Berger, J.; Walker, S.E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Kukkonen, J.

2007

Evaluation and inter-comparison of open road line source models currently being used in the nordic countries: a NORPAC project.

Berger, J.; Berkowicz, R.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Kukkonen, J.

2007

Part of book/report

Uncertainty mapping for air quality modelling and data assimilation. Powerpoint presentation.

Denby, B.; Costa, A.M.; Monteiro, A.; Dudek, A.; Walker, S.E.; van den Elshout, S.; Fisher, B.

2007

Uncertainty mapping for air quality modelling and data assimilation.

Denby, B.; Costa, A.M.; Monteiro, A.; Dudek, A.; Walker, S.E.; van den Elshout, S.; Fisher, B.

2007

Part of book/report

Evaluation and inter-comparison of open road line source models currently being used in the nordic countries: a NORPAC project.

Berger, J.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Berkowicz, R.

2007

Calculation of weighted daily mean values of NO2, PM10 and PM2,5 during maternities in Oslo in the period 1992-2002. Methodological description.

Walker, S.-E.

2007

Application of data assimilation in open road line source modelling.

Walker, S.E.; Berger, J.

2007

Part of book/report

Evaluation and inter-comparison of open road line source models currently being used in the Nordic countries: a NORPAC project.

Berger, J.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Berkowicz, R.

2007

Part of book/report

Individual case study report: 4. Data assimilation in open road line source modelling.

Walker, S.E. (eds.)

2007

Individual case study report: 3. Model and observation uncertainty analysis towards data assimilation on the urban scale.

Walker, S.E. (eds.)

2007

Dispersion and exposure calculation of PM10, NO2 and benzene for Oslo and Trondheim for the year 2005.

Slørdal, L.H.; Mc Innes, H.; Laupsa, H.; Walker, S.E.

2006

Data assimilation. Cross-cutting issue milestone report 6.8 (M.5).

Walker, S.E.; Schaap, M.,, Slini, L.

2006

An introduction to Sequential Importance Resampling.

Walker, S.E.

2006

Part of book/report

Cross cutting issue 5: Data assimilation. Poster presentation.

Walker, S.E.; Schaap, M.; Slini, L.

2006

Case study Oslo II: Data assimilation in open road line source modelling. Poster presentation.

Walker, S.E.

2006

Updated environmental assessment of the regional impact from the oil activity in the North Sea. Regular atmospheric emissions – consequences.

Knudsen, S.; Solberg, S.; Wathne, B.M.; Høgåsen, T.; Magnusson, J.; Tollefsen, K.E.; Aarrestad, P.A.; Reitan, O.; Stebel, K.; Walker, S.E.

2006

ESA Campaign Database (CDB) User Manual.

Vik, A.F.; Krognes, T.; Walker, S.-E.; Bjørndalsæter, S.; Stoll, C.; Bårde, T.; Paltiel, R.; Gloslie, B.

2006

Interpolation and assimilation methods for European scale air quality assessment and mapping. Part 1: Review and recommendations. Final draft.

Denby, B.; Horálek, J.; Walker, S.E.; Eben, K.; Fiala, J.

2005

An introduction to sequential importance resampling. Powerpoint presentation.

Walker, S.E.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM2.5 in Oslo for 1992-2002.

Walker, S.-E.; Rosland, P.

2005

Part of book/report

Development of a simplified photochemistry scheme for urban areas.

Solberg, S.; Walker, S.-E.; Denby, B.

2005

Part of book/report

A generic database for earth observation data. The ESA campaign data service.

Vik, A.F.; Krognes, T, Bjørndalsæter, S.; Stoll, C.; Walker, S.E.; Gloslie, B.; Paltiel, R.; Bårde, T.; Våler, R.L.

2005

Part of book/report

WP3 Data Management. Powerpoint presentation. Powerpoint presentation.

Vik, A.F.; Krognes, T.; Walker, S.E.; Bårde, T.; Paltiel, R.

2005

Application of Sequential Importance Resampling (SIR) for 1D atmospheric chemical data assimilations.

Walker, S.E.; Hatlo, M.

2005

The RETRO database for observations. Poster presentation.

Vik, A.F.; Bjørndalsæter, S.; Stoll, C.; Krognes, T.; Paltiel, R.; Bårde, T.; Walker, S.-E.; Westbye, A.; Molin, P.

2005

Simulated experiments with sequential importance resampling on a 1D advection-diffusion model using pseudo observations.

Walker, S.-E.; Hatlo, M.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM 2,5 in Oslo for 1992-2002.

Walker, S.-E.; Rosland, P.

2005

Development of a simplified photochemistry scheme for urban areas.

Solberg, S.; Walker, S.-E.; Denby, B.

2005

Dispersion and exposure calculation of PM10, NO2 and benzene for Oslo, Trondheim and Bergen for 2003.

Laupsa, H.; Tønnesen, D.; Krognes, T.; Bruno, M.; Walker, S.E.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM2,5 in Oslo for 1992-2002.

Walker, S.E.; Rosland, P.

2005

Metadata guidelines for the ESA Campaign Data Base (CDB). Version 0.02.

Krognes, T.; Walker, S.E.; Vik, A.F.

2004

Calculation of NO2, PM10 and PM2,5 in Oslo for the HUBRO health study.

Walker, S-E.

2004

Bedre byluft – evaluering av prognosemodell for meteorologi og luftkvalitet vinteren 2003/2004.

Ødegaard, V.; Gjerstad, K.I.; Bjergene, N.; Jablonska, H.T.B.; Walker, S.E.

2004

Environmental studies related to changes in the main road system in Oslo East. Estimating indicators of exposure for interview-study.

Tønnesen, D.; Walker, S.E.; Haugsbakk, I.

2004

Calculations of 3-year average concentrations in administrative regions in Oslo for the period 1992-2002.

Walker, S. E.

2004

ASSET data management.

Vik, A.F.; Krognes, T.; Walker, S.E.; Paltiel, R.; Bårde, T.

2003

Further development of a modelling system able to link hemispheric-regional and local air pollution.

Wind, P.; Tarrasón, L.; Slørdal, L.H.; Solberg, S.; Denby, B.; Walker, S.-E.

2003

Development and implementation of a simplified EMEP photochemistry scheme for urban areas in EPISODE.

Walker, S.-E.; Solberg, S.; Denby, B.

2003

Air pollution as a function of the distance from a road.

Hagen, L.O.; Larssen, S.; Walker, S.-E.

2003

The urban air dispersion model EPISODE applied in AirQUIS2003. Technical description.

Slørdal, L.H.; Walker, S.-E.; Solberg, S.

2003

Bedre byluft. Evaluering av prognosemodell for meteorologi og luftkvalitet vinteren 2002/2003.

Ødegaard, V.; Walker, S.-E.; Midtbø, K. H.; Jablonska, H. T. B.; Gjerstad, K. I.; Bjergene, N.

2003

The contribution to nitrogen deposition and ozone formation in South Norway from atmospheric emissions related to the petroleum activity in the North Sea.

Solberg, S.; Lazaridis, M.; Walker, S.E.; Knudsen, S.; Semb, A.

2003

Scientific journal publication

Conversion of daily to hourly mean based forecast classes for particles in Bedre byluft.

Walker, S.-E.

2003

Development of a modeling system able to link hemispheric-regional and local air pollution.

Wind, P.; Tarrasón, L.; Berge, E.; Slørdal, L.H.; Solberg, S.; Walker, S.E.

2002

Implementation of extraction routine for ECMWF data through the Calval web-pages. Final development report.

Vik, A.F.; Krognes, T.; Walker, S.E.; Bårde, T.; Paltiel, R.; Tørnkvist, K.K.; Gloslie, B.; Larsen, R.; Thanh, T.N.

2002

Operation of an Envisat Validation Data Centre. Estec Contract No 14419/00/NL/SF. Final report.

Krognes, T.; Vik, Aa. F.; Tørnkvist, K.K.; Walker, S.E.; Paltiel, R.; Bårde, T.; Gloslie, B.; Larsen, R.; Braathen, G.O.; Thanh, T.N.

2002

Evaluation of air quality and meteorology forecast model for Norwegian cities 2001-2002.

Jablonska, H.T.B.; Walker, S.E.; Bøhler, T.; Køltzow, M.Ø.; Berge, E.; Bjergene, N.

2002

Environmental assessment of the regional impact from the oil activity in the Norwegian Sea. Regular atmospheric emissions – consequences.

Solberg, S.; Walker, S.E.; Skjelkvåle, B.L.; Høgåsen, T.; Molvær, J.; Larssen, T.; Aarrestad, P.A.; Reitan, O.

2002

Calculation of air quality around Oslo airport Gardermoen 2001.

Gram, F.; Walker, S.E.

2002

Application of model calculated background concentrations in the urban air quality model EPISODE.

Slørdal, L.H.; Solberg, S.; Walker, S.-E.

2001

A real-time operational forecast model for meteorology and air quality during peak air pollution episodes in Oslo, Norway.

Berge, E.; Walker, S.E.; Sorteberg, A.; Lenkopane, M.L.; Eastwood, S.; Jablonska, H.J.; Ødegaard,M.

2001

Part of book/report

Long-term measurements and model calculations of formaldehyde at rural European monitoring sites.

Solberg, S.; Dye, C.; Walker, S.E.; Simpson, D.

2001

Scientific journal publication

Evaluation of urban scale time-dependent dispersion model with subgrid elements, in Oslo, Norway.

Grønskei, K.E.; Gram, F.; Larssen, S.; Walker, S.E.

2000

Air pollution exposure monitoring and estimation VII. Estimation of population exposure in a central European airshed.

Grønskei, K.E.; Bartonova, A.; Brechler, J.; Walker, S.E.; Larssen, S.

2000

Scientific journal publication

Air quality modelling in assessing impacts of traffic measures in Oslo. Poster presentation.

Bartonova, A.; Clench-Aas, J.; Walker, S E.; Tønnesen, D A.; Larssen, S.

1999

Part of book/report

Development and evaluation of the urban dispersion model Episode used in evaluating traffic diversion measures in Oslo. Poster presentation.

Walker, S.E.; Slørdal, L.H.; Guerreiro, C.; Grønskei, K.E.

1999

Part of book/report

Air pollution exposure monitoring and estimating. Part VI: Ambient exposure of adults in an industrialised region.

Clench-Aas, J.; Bartonova, A.; Grønskei, K E.; Hagen, L.O.; Braathen, O.A.; Walker, S.E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part V: Traffic exposure in adults.

Bartonova, A.; Clench-Aas, J.; Gram, F.; Grønskei, K.E.; Guerreiro, C.; Larssen, S. Tønnesen, D.; Walker, S.-E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part IV: Urban exposure in children.

Clench-Aas, J.; Bartonova, A.; Grønskei, K.E.; Walker, S.E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part II: Model evaluation and population exposure.

Walker, S.E.; Slørdal, L.H.; Guerreiro, C.; Gram, F.; Grønskei, K.E.

1999

Scientific journal publication

Dispersion calculations for on-line surveillance in Grenland. Description of programs and Users Guide.

Walker, S. E.; Grønskei, K. E.

1992

Revision of air quality assessment for Drammen

NILU, in collaboration with Asplan Viak AS, has prepared a local air quality assessment for Drammen municipality. The project includes an assessment of air quality in Drammen through traffic calculations […]

Project period: 2022 – 2023

Concluded

Air quality assessment for Lørenskog municipality

The air quality assessment for Lørenskog municipality covers mapping of the air quality through traffic, emission and dispersion calculations of PM10, PM2,5 and NO2 for the present situation (2019) and […]

Project period: 2022 – 2022

Concluded

Model Advancements for high Spatial and TEmporal Resolution simulations of environmental toxics (SIS MASTER)

The main goal of the project is to modify and enhance NILUs existing atmospheric models to allow for improved simulation of traditional air pollutants (e.g., NO2, PM2.5, PM10) at very […]

Project period: 2018 – 2021

Concluded

Air quality assessment for Tromsø

NILU and Urbanet analyse have prepared a revised air quality assessment for Tromsø. The action plan, including strategies and measures, aims to reduce air pollution to a level that meets […]

Project period: 2019 – 2019

Concluded

Sam-Erik Walker holds an M.Sc. in Statistics and a B.Sc. in Computer Science from the University of Oslo.

He has over 30 years of experience developing and applying air pollution dispersion models for cities and urban areas and analysing air quality data using various numerical and statistical tools and methods. These include deterministic and probabilistic methods for model evaluation and validation, data assimilation, ensemble modelling, and data fusion to combine air quality observations with model results. He is one of the principal authors of several of the present models at NILU, including the urban air pollution dispersion model EPISODE.

He is also the leading developer behind the AirGAM trend and prediction model at NILU. This model enables the estimation of meteorology-adjusted long-term trends of air pollutants such as NO2, O3, PM, and VOCs at air quality stations in Norway and Europe. It has been used to quantify the effects of lockdowns during the recent COVID-19 pandemic and for estimating long-term trends for all EEA stations in Europe.

Recently, he developed the AirRisk model, a risk assessment model to quantify the risk or probability of exceeding limit values of NO2 and PM in connection with recent assessment studies in various Norwegian cities and urban areas, including Lørenskog, Drammen, and Oslo.

He actively disseminates scientific knowledge by writing reports and papers and regularly participates in scientific conferences. His primary motivation for working at NILU is to contribute to a cleaner world.

Sam-Erik Walker has 124 publications at NILU:

Nordiske perspektiver på vedfyring – utslipp og tiltak nå og mot 2030

Grythe, Henrik; Lopez-Aparicio, Susana; Markelj, Miha; Walker, Sam-Erik

2024

Trafikk- og luftkvalitetsberegninger i forbindelse med ny tiltaksutredning for bedre luftkvalitet i Oslo og Bærum 2025-2030. Beregningsresultater for Oslo

Weydahl, Torleif; Walker, Sam-Erik; Markelj, Miha; Andersen, André

2024

Exploring the connection between COVID19, the energy crisis and PM2.5 emissions from residential heating

Lopez-Aparicio, Susana; Grythe, Henrik; Markelj, Miha; Evangeliou, Nikolaos; Walker, Sam-Erik

2024

Scientific journal publication

Decoding temporal patterns and trends of PM10 pollution over Delhi: a multi-year analysis (2015–2022)

Chetna, NN; Dhaka, Surendra K.; Walker, Sam-Erik; Rawat, Vikas; Singh, Narendra

2024

Scientific journal publication

Long-term meteorology-adjusted and unadjusted trends of PM2.5 using the AirGAM model over Delhi, 2007–2022

Chetna, NN; Dhaka, Surendra K.; Walker, Sam-Erik; Rawat, Vikas; Singh, Narendra

2024

Scientific journal publication

Screening Programme 2022. New environmental pollutants.

Gundersen, Cathrine Brecke; Reid, Malcolm; Rostkowski, Pawel; Bæk, Kine; Rundberget, Thomas; Vogelsang, Christian; Rødland, Elisabeth; Beylich, Bjørnar; Eikenes, Heidi; Bäcklund, Are; Walker, Sam-Erik; Borgen, Anders Røsrud; Nikiforov, Vladimir; Håland, Alexander; Schmidbauer, Norbert

2023

Long-term Meteorology-Adjusted and Unadjusted Trends of PM2.5 Using the AirGAM Model Over Delhi, 2007–2022

Dang, Chetna; Dhaka, S K; Walker, Sam-Erik; Longiany, Gagandeep; Rawat, Wikas

2023

VOC measurements 2021

Solberg, Sverre; Claude, Anja; Reimann, Stefan; Walker, Sam-Erik

2023

Revidert tiltaksutredning for lokal luftkvalitet i Drammen kommune

Weydahl, Torleif; Markelj, Miha; Walker, Sam-Erik; Høyem, Harald

2023

Tiltaksutredning for lokal luftkvalitet i Lørenskog kommune

Høiskar, Britt Ann Kåstad; Walker, Sam-Erik; Weydahl, Torleif; Markelj, Miha; Andersen, André; Lopez-Aparicio, Susana; Grythe, Henrik

2023

The AirGAM 2022r1 air quality trend and prediction model

Walker, Sam-Erik; Solberg, Sverre; Schneider, Philipp; Guerreiro, Cristina

2023

Scientific journal publication

VOC measurements 2020

Solberg, Sverre; Claude, Anja; Reimann, Stefan; Sauvage, Stéphane; Walker, Sam-Erik

2022

Understanding Air Quality Trends in Europe. Focus on the relative contribution of changes in emission of activity sectors, natural fraction and meteorological variability.

Colette, Augustin; Solberg, Sverre; Aas, Wenche; Walker, Sam-Erik

2021

Appropriate Assimilation Methods for Air Quality Prediction and Pollutant Emission Inversion. An Urban Data Assimilation Systems Report.

Hamer, Paul David; Walker, Sam-Erik; Schneider, Philipp

2021

Quantifying the Impact of the Covid-19 Lockdown Measures on Nitrogen Dioxide Levels throughout Europe

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp; Guerreiro, Cristina

2021

Scientific journal publication

Revidert tiltaksutredning for lokal luftkvalitet i Stavanger kommune

Weydahl, Torleif; Johnsrud, Mona; Vo, Dam Thanh; Walker, Sam-Erik; Høiskar, Britt Ann Kåstad; Ranheim, Patrick

2020

Air quality in Europe – 2020 report

Ortiz, Alberto González; Guerreiro, Cristina; Soares, Joana; Antognazza, Frederico; Gsella, Artur; Houssiau, Michel; Liberti, Luca; Lükewille, Anke; Öztürk, Evrim; Horálek, Jan; Banyuls, Lorena; Targa, Jaume; Schneider, Philipp; Solberg, Sverre; Walker, Sam-Erik; Colette, Augustin

2020

The urban dispersion model EPISODE v10.0 – Part 1: An Eulerian and sub-grid-scale air quality model and its application in Nordic winter conditions

Hamer, Paul David; Walker, Sam-Erik; Sousa Santos, Gabriela; Vogt, Matthias; Vo, Dam Thanh; Lopez-Aparicio, Susana; Schneider, Philipp; Ramacher, Martin O. P.; Karl, Matthias

2020

Scientific journal publication

A presentation of the EPISODE urban scale air quality model and its application to Nordic winter conditions

Hamer, Paul David; Walker, Sam-Erik; Sousa Santos, Gabriela; Vogt, Matthias; Vo, Dam Thanh; Lopez-Aparicio, Susana; Ramacher, Martin O. P.; Karl, Matthias

2020

Part of book/report

Hvordan har luftkvalitet i Europa endret seg under lockdown og hvorfor?

Guerreiro, Cristina; Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp

2020

Networks of air quality sensors and their use for high-resolution mapping of urban air quality

Schneider, Philipp; Castell, Nuria; Hamer, Paul David; Walker, Sam-Erik; Bartonova, Alena

2020

Statistical modelling for long-term trends of pollutants – Use of a GAM model for the assessment of measurements of O3, NO2 and PM

Solberg, Sverre; Walker, Sam-Erik; Guerreiro, Cristina; Colette, Augustin

2020

A study of the relative expanded uncertainty formula for comparing low-cost sensor and reference measurements

Walker, Sam-Erik; Schneider, Philipp

2020

Tiltaksutredning for lokal luftkvalitet i Tromsø

Weydahl, Torleif; Walker, Sam-Erik; Johnsrud, Mona; Vo, Dam Thanh; Ranheim, Patrick

2019

Trends in measured NO2 and PM. Discounting the effect of meteorology.

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp

2019

Monitoring of greenhouse gases and aerosols at Svalbard and Birkenes in 2018. Annual report.

Myhre, Cathrine Lund; Svendby, Tove Marit; Hermansen, Ove; Lunder, Chris Rene; Platt, Stephen Matthew; Fiebig, Markus; Fjæraa, Ann Mari; Hansen, Georg Heinrich; Schmidbauer, Norbert; Krognes, Terje; Walker, Sam-Erik

2019

The Eulerian urban dispersion model EPISODE – Part 2: Extensions to the source dispersion and photochemistry for EPISODE–CityChem v1.2 and its application to the city of Hamburg

Karl, Matthias; Walker, Sam-Erik; Solberg, Sverre; Ramacher, Martin O. P.

2019

Scientific journal publication

Focused model selection and inference using robust estimators.

Walker, Sam-Erik; Hjort, Nils Lid

2018

Monitoring of greenhouse gases and aerosols at Svalbard and Birkenes in 2017 – Annual report

Myhre, Cathrine Lund; Svendby, Tove Marit; Hermansen, Ove; Lunder, Chris Rene; Platt, Stephen Matthew; Fiebig, Markus; Fjæraa, Ann Mari; Hansen, Georg Heinrich; Schmidbauer, Norbert; Krognes, Terje; Walker, Sam-Erik

2018

Discounting the effect of meteorology on trends in surface ozone: Development of statistical tools

Solberg, Sverre; Walker, Sam-Erik; Schneider, Philipp; Guerreiro, Cristina; Colette, Augustin

2018

Bedre byluft. Endringer i 2014 og forskningsresultater av prognoser for meteorologi og luftkvalitet i norske byer vinteren 2013-2014.

Denby, B.R.; Sundvor, I.; Süld, J.; Kristensen, A.; Vallejo, I.; Walker, S.E.

2015

Modelling atmospheric oxidation of 2-aminoethanol (MEA) emitted from post-combustion capture using WRF-Chem.

Karl, M.; Svendby, T.; Walker, S.-E.; Velken, A.S.; Castell, N.; Solberg, S.

2015

Scientific journal publication

Data assimilation and statistical post-processing for numerical air quality predictions.

Steinbakk, G. H, Thorarinsdottir, T. L.; Lahoz, W. A.; Walker, S.-E.

2014

Method and tool selection within the pilot study of air quality in Poland: Data fusion methodologies.

Karl, M.; Walker, S.-E.

2014

Ensemble based probabilistic forecasting of meteorology and air quality in Oslo, Norway.

Walker, S.E.

2014

Uncertainties in assessing the environmental impact of amine emissions from a CO2 capture plant.

Karl, M.; Castell, N.; Simpson, D.; Solberg, S.; Starrfelt, J.; Svendby, T.; Walker, S.-E.; Wright, R.F.

2014

Scientific journal publication

Using UncertWeb for improved decision making. UncertWeb Consortium Deliverable 3.5.

Heuvelink, G.; Helle, K.; Pebesma, E.; Rasouli, S.; Stasch, C.; Truong, P.; Walker, S.E.

2013

Report on integrating the traffic/individual modelling with the air quality modelling. UncertWeb Consortium Deliverable 8.3.

Gerharz, L.; Helle, K.; Pebesma, E.; Pross, B.; Stasch, C.; Rasouli, S.; Timmermans, H.; Denby, B.; Walker, S.E.

2013

Validation of UncertWeb: Air quality forecasting. UncertWeb Consortium Deliverable 6.3.

Walker, S.E.; Denby, B.; Pross, B.; Cornford, D.

2013

Time series analysis of significant wave height data for identification of trends in the ocean wave climate.

Vanem, E.; Walker, S.E.

2013

Part of book/report

Identifying trends in the ocean wave climate by time series analyses of significant wave heightdata.

Vanem, E.; Walker, S.E.

2013

Scientific journal publication

Probabilistic forecasting of air quality in Oslo. UncertWeb Consortium Deliverable 6.2.

Walker, S.E.; Cornford, D.

2012

Ensemble based probabilistic forecasting of air quality in Oslo and Rotterdam.

Walker, S.E.; Denby B.R.; Castell-Balaguer, N.

2012

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2011

Scientific journal publication

NO2 calculations for 2010 and 2025 in Oslo and Bærum. Contribution from diesel cars and possible precautions.

Sundvor, I.; Tarrasón, L.; Walker, S-E.; Tønnesen, D.

2011

Calculation of dispersion and deposition, April 2009 – April 2010. Environmental surveillance of emissions to air from Snøhvit-Hammerfest LNG.

Liu, L.; Walker, S.E.; Hak, C.; Gjerstad, K.I.

2011

Data assimilation within the Air4EU project: the Athens case.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2011

Scientific journal publication

Towards uncertainty mapping in air-quality modelling and assessment.

Denby, B.; Dudek, A.; Walker, S.E.; Costa, A.M.; Monteiro, A.; van den Elshout, S.; Fisher, B.

2011

Scientific journal publication

The NILU SURFEX-EnKF land data assimilation system.

Lahoz, W.; Svendby, T.; Walker, S.-E.; Mahfouf, J.-F.

2010

Part of book/report

Ambient air pollution exposure, residential mobility and term birth weight in Oslo, Norway.

Madsen, C.; Gehring, U.; Walker, S.E.; Brunekreef, B.; Stigum, H.; Næss, Ø.; Nafstad, P.

2010

Scientific journal publication

The NILU SURFEX-EnKF land data assimilation system.

Lahoz, W.; Walker, S.-E.; Dammann, D.

2010

Evaluation and inter-comparison of open road line source models currently in use in the Nordic countries.

Berger, J.; Walker, S.-E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Härkönen, J.; Nikmo, J.; Karppinen, A.

2010

Scientific journal publication

Ambient air pollution exposure, residential mobility and term birth weight in Oslo, Norway.

Madsen, C.; Gehring, U.; Walker, S.E.; Brunekreef, B.; Stigum, H.; Næss, Ø.; Nafstad, P.

2009

Scientific journal publication

Modelling long-term averages of local ambient air pollution in Oslo, Norway: evaluation of nitrogen dioxide, PM10 and PM2.5.

Oftedal, B.; Walker, S.E.; Gram, F.; Mc Innes, H.; Nafstad, P.

2009

Scientific journal publication

Evaluation and inter-comparison of open road line source models currently in use in the Nordic countries.

Berger, J.; Walker, S.E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Härkonen, J.; Nikmo, J.; Karppinen, A.

2008

Scientific journal publication

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2008

WORM – A new open road line source model for low wind speed conditions.

Walker, S.E.

2008

Scientific journal publication

Residential outdoor air pollution and lung function in schoolchildren.

Oftedal, B.; Brunekreef, B.; Nystad, W.; Madsen, C.; Walker, S.E.; Nafstad, P.

2008

Scientific journal publication

Quantification of uncertainties associated with an integrated Gaussian line source model using ensembles.

Walker, S.E.

2007

Application of data assimilation in open road line source modelling. Case study Oslo II.

Walker, S.E.; Berger, J.

2007

Data assimilation within the Air4EU project: the Athens case. Powerpoint presentation.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2007

Data assimilation within the Air4EU project: the Athens case.

Slini, T.; Walker, S.E.; Moussiopoulos, N.

2007

Part of book/report

Quantification of uncertainties associated with an integrated Gaussian line source model using ensembles.

Walker, S.E.

2007

Part of book/report

Evaluation and inter-comparison of open road line source (ORLS) models currently being used in the Nordic countries. Powerpoint presentation.

Berger, J.; Walker, S.E.; Denby, B.; Berkowicz, R.; Løfstrøm, P.; Ketzel, M.; Kukkonen, J.

2007

Evaluation and inter-comparison of open road line source models currently being used in the nordic countries: a NORPAC project.

Berger, J.; Berkowicz, R.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Kukkonen, J.

2007

Part of book/report

Uncertainty mapping for air quality modelling and data assimilation. Powerpoint presentation.

Denby, B.; Costa, A.M.; Monteiro, A.; Dudek, A.; Walker, S.E.; van den Elshout, S.; Fisher, B.

2007

Uncertainty mapping for air quality modelling and data assimilation.

Denby, B.; Costa, A.M.; Monteiro, A.; Dudek, A.; Walker, S.E.; van den Elshout, S.; Fisher, B.

2007

Part of book/report

Evaluation and inter-comparison of open road line source models currently being used in the nordic countries: a NORPAC project.

Berger, J.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Berkowicz, R.

2007

Calculation of weighted daily mean values of NO2, PM10 and PM2,5 during maternities in Oslo in the period 1992-2002. Methodological description.

Walker, S.-E.

2007

Application of data assimilation in open road line source modelling.

Walker, S.E.; Berger, J.

2007

Part of book/report

Evaluation and inter-comparison of open road line source models currently being used in the Nordic countries: a NORPAC project.

Berger, J.; Walker, S.E.; Denby, B.; Løfstrøm, P.; Ketzel, M.; Berkowicz, R.

2007

Part of book/report

Individual case study report: 4. Data assimilation in open road line source modelling.

Walker, S.E. (eds.)

2007

Individual case study report: 3. Model and observation uncertainty analysis towards data assimilation on the urban scale.

Walker, S.E. (eds.)

2007

Dispersion and exposure calculation of PM10, NO2 and benzene for Oslo and Trondheim for the year 2005.

Slørdal, L.H.; Mc Innes, H.; Laupsa, H.; Walker, S.E.

2006

Data assimilation. Cross-cutting issue milestone report 6.8 (M.5).

Walker, S.E.; Schaap, M.,, Slini, L.

2006

An introduction to Sequential Importance Resampling.

Walker, S.E.

2006

Part of book/report

Cross cutting issue 5: Data assimilation. Poster presentation.

Walker, S.E.; Schaap, M.; Slini, L.

2006

Case study Oslo II: Data assimilation in open road line source modelling. Poster presentation.

Walker, S.E.

2006

Updated environmental assessment of the regional impact from the oil activity in the North Sea. Regular atmospheric emissions – consequences.

Knudsen, S.; Solberg, S.; Wathne, B.M.; Høgåsen, T.; Magnusson, J.; Tollefsen, K.E.; Aarrestad, P.A.; Reitan, O.; Stebel, K.; Walker, S.E.

2006

ESA Campaign Database (CDB) User Manual.

Vik, A.F.; Krognes, T.; Walker, S.-E.; Bjørndalsæter, S.; Stoll, C.; Bårde, T.; Paltiel, R.; Gloslie, B.

2006

Interpolation and assimilation methods for European scale air quality assessment and mapping. Part 1: Review and recommendations. Final draft.

Denby, B.; Horálek, J.; Walker, S.E.; Eben, K.; Fiala, J.

2005

An introduction to sequential importance resampling. Powerpoint presentation.

Walker, S.E.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM2.5 in Oslo for 1992-2002.

Walker, S.-E.; Rosland, P.

2005

Part of book/report

Development of a simplified photochemistry scheme for urban areas.

Solberg, S.; Walker, S.-E.; Denby, B.

2005

Part of book/report

A generic database for earth observation data. The ESA campaign data service.

Vik, A.F.; Krognes, T, Bjørndalsæter, S.; Stoll, C.; Walker, S.E.; Gloslie, B.; Paltiel, R.; Bårde, T.; Våler, R.L.

2005

Part of book/report

WP3 Data Management. Powerpoint presentation. Powerpoint presentation.

Vik, A.F.; Krognes, T.; Walker, S.E.; Bårde, T.; Paltiel, R.

2005

Application of Sequential Importance Resampling (SIR) for 1D atmospheric chemical data assimilations.

Walker, S.E.; Hatlo, M.

2005

The RETRO database for observations. Poster presentation.

Vik, A.F.; Bjørndalsæter, S.; Stoll, C.; Krognes, T.; Paltiel, R.; Bårde, T.; Walker, S.-E.; Westbye, A.; Molin, P.

2005

Simulated experiments with sequential importance resampling on a 1D advection-diffusion model using pseudo observations.

Walker, S.-E.; Hatlo, M.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM 2,5 in Oslo for 1992-2002.

Walker, S.-E.; Rosland, P.

2005

Development of a simplified photochemistry scheme for urban areas.

Solberg, S.; Walker, S.-E.; Denby, B.

2005

Dispersion and exposure calculation of PM10, NO2 and benzene for Oslo, Trondheim and Bergen for 2003.

Laupsa, H.; Tønnesen, D.; Krognes, T.; Bruno, M.; Walker, S.E.

2005

Calculation of person-weighted average concentrations of NO2, PM10 and PM2,5 in Oslo for 1992-2002.

Walker, S.E.; Rosland, P.

2005

Metadata guidelines for the ESA Campaign Data Base (CDB). Version 0.02.

Krognes, T.; Walker, S.E.; Vik, A.F.

2004

Calculation of NO2, PM10 and PM2,5 in Oslo for the HUBRO health study.

Walker, S-E.

2004

Bedre byluft – evaluering av prognosemodell for meteorologi og luftkvalitet vinteren 2003/2004.

Ødegaard, V.; Gjerstad, K.I.; Bjergene, N.; Jablonska, H.T.B.; Walker, S.E.

2004

Environmental studies related to changes in the main road system in Oslo East. Estimating indicators of exposure for interview-study.

Tønnesen, D.; Walker, S.E.; Haugsbakk, I.

2004

Calculations of 3-year average concentrations in administrative regions in Oslo for the period 1992-2002.

Walker, S. E.

2004

ASSET data management.

Vik, A.F.; Krognes, T.; Walker, S.E.; Paltiel, R.; Bårde, T.

2003

Further development of a modelling system able to link hemispheric-regional and local air pollution.

Wind, P.; Tarrasón, L.; Slørdal, L.H.; Solberg, S.; Denby, B.; Walker, S.-E.

2003

Development and implementation of a simplified EMEP photochemistry scheme for urban areas in EPISODE.

Walker, S.-E.; Solberg, S.; Denby, B.

2003

Air pollution as a function of the distance from a road.

Hagen, L.O.; Larssen, S.; Walker, S.-E.

2003

The urban air dispersion model EPISODE applied in AirQUIS2003. Technical description.

Slørdal, L.H.; Walker, S.-E.; Solberg, S.

2003

Bedre byluft. Evaluering av prognosemodell for meteorologi og luftkvalitet vinteren 2002/2003.

Ødegaard, V.; Walker, S.-E.; Midtbø, K. H.; Jablonska, H. T. B.; Gjerstad, K. I.; Bjergene, N.

2003

The contribution to nitrogen deposition and ozone formation in South Norway from atmospheric emissions related to the petroleum activity in the North Sea.

Solberg, S.; Lazaridis, M.; Walker, S.E.; Knudsen, S.; Semb, A.

2003

Scientific journal publication

Conversion of daily to hourly mean based forecast classes for particles in Bedre byluft.

Walker, S.-E.

2003

Development of a modeling system able to link hemispheric-regional and local air pollution.

Wind, P.; Tarrasón, L.; Berge, E.; Slørdal, L.H.; Solberg, S.; Walker, S.E.

2002

Implementation of extraction routine for ECMWF data through the Calval web-pages. Final development report.

Vik, A.F.; Krognes, T.; Walker, S.E.; Bårde, T.; Paltiel, R.; Tørnkvist, K.K.; Gloslie, B.; Larsen, R.; Thanh, T.N.

2002

Operation of an Envisat Validation Data Centre. Estec Contract No 14419/00/NL/SF. Final report.

Krognes, T.; Vik, Aa. F.; Tørnkvist, K.K.; Walker, S.E.; Paltiel, R.; Bårde, T.; Gloslie, B.; Larsen, R.; Braathen, G.O.; Thanh, T.N.

2002

Evaluation of air quality and meteorology forecast model for Norwegian cities 2001-2002.

Jablonska, H.T.B.; Walker, S.E.; Bøhler, T.; Køltzow, M.Ø.; Berge, E.; Bjergene, N.

2002

Environmental assessment of the regional impact from the oil activity in the Norwegian Sea. Regular atmospheric emissions – consequences.

Solberg, S.; Walker, S.E.; Skjelkvåle, B.L.; Høgåsen, T.; Molvær, J.; Larssen, T.; Aarrestad, P.A.; Reitan, O.

2002

Calculation of air quality around Oslo airport Gardermoen 2001.

Gram, F.; Walker, S.E.

2002

Application of model calculated background concentrations in the urban air quality model EPISODE.

Slørdal, L.H.; Solberg, S.; Walker, S.-E.

2001

A real-time operational forecast model for meteorology and air quality during peak air pollution episodes in Oslo, Norway.

Berge, E.; Walker, S.E.; Sorteberg, A.; Lenkopane, M.L.; Eastwood, S.; Jablonska, H.J.; Ødegaard,M.

2001

Part of book/report

Long-term measurements and model calculations of formaldehyde at rural European monitoring sites.

Solberg, S.; Dye, C.; Walker, S.E.; Simpson, D.

2001

Scientific journal publication

Evaluation of urban scale time-dependent dispersion model with subgrid elements, in Oslo, Norway.

Grønskei, K.E.; Gram, F.; Larssen, S.; Walker, S.E.

2000

Air pollution exposure monitoring and estimation VII. Estimation of population exposure in a central European airshed.

Grønskei, K.E.; Bartonova, A.; Brechler, J.; Walker, S.E.; Larssen, S.

2000

Scientific journal publication

Air quality modelling in assessing impacts of traffic measures in Oslo. Poster presentation.

Bartonova, A.; Clench-Aas, J.; Walker, S E.; Tønnesen, D A.; Larssen, S.

1999

Part of book/report

Development and evaluation of the urban dispersion model Episode used in evaluating traffic diversion measures in Oslo. Poster presentation.

Walker, S.E.; Slørdal, L.H.; Guerreiro, C.; Grønskei, K.E.

1999

Part of book/report

Air pollution exposure monitoring and estimating. Part VI: Ambient exposure of adults in an industrialised region.

Clench-Aas, J.; Bartonova, A.; Grønskei, K E.; Hagen, L.O.; Braathen, O.A.; Walker, S.E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part V: Traffic exposure in adults.

Bartonova, A.; Clench-Aas, J.; Gram, F.; Grønskei, K.E.; Guerreiro, C.; Larssen, S. Tønnesen, D.; Walker, S.-E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part IV: Urban exposure in children.

Clench-Aas, J.; Bartonova, A.; Grønskei, K.E.; Walker, S.E.

1999

Scientific journal publication

Air pollution exposure monitoring and estimation. Part II: Model evaluation and population exposure.

Walker, S.E.; Slørdal, L.H.; Guerreiro, C.; Gram, F.; Grønskei, K.E.

1999

Scientific journal publication

Dispersion calculations for on-line surveillance in Grenland. Description of programs and Users Guide.

Walker, S. E.; Grønskei, K. E.

1992

Revision of air quality assessment for Drammen

NILU, in collaboration with Asplan Viak AS, has prepared a local air quality assessment for Drammen municipality. The project includes an assessment of air quality in Drammen through traffic calculations […]

Project period: 2022 – 2023

Concluded

Air quality assessment for Lørenskog municipality

The air quality assessment for Lørenskog municipality covers mapping of the air quality through traffic, emission and dispersion calculations of PM10, PM2,5 and NO2 for the present situation (2019) and […]

Project period: 2022 – 2022

Concluded

Model Advancements for high Spatial and TEmporal Resolution simulations of environmental toxics (SIS MASTER)

The main goal of the project is to modify and enhance NILUs existing atmospheric models to allow for improved simulation of traditional air pollutants (e.g., NO2, PM2.5, PM10) at very […]

Project period: 2018 – 2021

Concluded

Air quality assessment for Tromsø

NILU and Urbanet analyse have prepared a revised air quality assessment for Tromsø. The action plan, including strategies and measures, aims to reduce air pollution to a level that meets […]

Project period: 2019 – 2019

Concluded