Forskergrupper
Forskning
Boundary layer meteorology:
- Characterization of the coherence of turbulence above the sea and in Norwegian fjords.
- Influence of the topography on the mean and turbulent flow characteristics.
- Synthetic turbulence generation in the atmospheric surface layer.
- Influence of the blocking by the surface on the spectral characteristics of turbulence.
Wind engineering:
- Turbulent wind load modelling on long-span bridges.
- Data-driven modelling for structural dynamics.
- Full-scale vibration analysis.
Lidar remote sensing of wind:
- Can scanning Doppler wind lidars measure turbulence?.
- Study of the flow around bridges with short-range and long-range wind lidar instruments.
Undervisning
Courses
- SDG310: Introduction: Interdisciplinary Approaches to Sustainable Development (2022-present)
- ENERGI322 Offshore wind energy - part 2 (2022-present)
- ENERGI321 Offshore wind energy - part 1 (2023-present)
- ENERGI210 Wind turbine aerodynamics (2022-2023)
- ENERGI230 Miljø og energi (2023-present)
- ENERGI101: Introduksjon til energikjelder og forbruk (2020)
Publikasjoner
2025
- Etienne Cheynet (2025). Introduction to turbulence modelling for wind loading on structure. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2025). Surface pressure measurement system for investigating bridge aerodynamics. (ekstern lenke)
- Shokoufeh Malekmohammadi; Etienne Cheynet; Joachim Reuder (2025). High-resolution wind lidar observation of Kelvin-Helmholtz billows above an offshore wind farm. (ekstern lenke)
- Lennart Vogt; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2025). Stable boundary layer wind profiles – A comparison of analytical models and lidar observations. (ekstern lenke)
- Shokoufeh Malekmohammadi; Etienne Cheynet; Joachim Reuder (2025). Observation of Kelvin–Helmholtz billows in the marine atmospheric boundary layer by a ship-borne Doppler wind lidar. (ekstern lenke)
- Etienne Cheynet (2025). ERA5 for wind ressource assessment: an introduction. (ekstern lenke)
- Etienne Cheynet (2025). Hva er veien videre for Norsk Havvind? Strømproduksjon fra havvind parker utenfor Vestlandet. (ekstern lenke)
- Bendik Voldseth; Etienne Cheynet; Joachim Reuder (2025). Science to Insurance: Improved Extreme Wind Estimates for Offshore Wind Assets. (ekstern lenke)
- Mauro Ghirardelli; Stephan Thomas Kral; Etienne Cheynet et al. (2025). SAMURAI-S: Sonic Anemometer on a MUlti-Rotor drone for Atmospheric turbulence Investigation in a Sling load configuration. (ekstern lenke)
- Etienne Cheynet; Jan Markus Diezel; Hilde Haakenstad et al. (2025). Tall wind profile validation of ERA5, NORA3, and NEWA datasets using lidar observations. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2025). Wind turbulence around a bridge deck in full scale. (ekstern lenke)
- Ghirardelli Mauro; Stephan Thomas Kral; Etienne Cheynet et al. (2025). SAMURAI-S: Sonic Anemometer on a MUlti-Rotor drone for Atmospheric turbulence Investigation in a Sling load configuration. (ekstern lenke)
- Huize Chen; Xiaomo Jiang; Huaiyu Hui et al. (2025). Enhancing probabilistic wind speed forecasting by integrating self-adaptive Bayesian wavelet denoising with deep Gaussian process regression under uncertainties. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2025). Field Observations of Buffeting Loads on a Suspension Bridge Girder. (ekstern lenke)
- Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson; Etienne Cheynet et al. (2025). Field observations of bridge deck aerodynamics. (ekstern lenke)
- Lennart Vogt; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2025). Stable boundary layer wind profiles – A comparison of analytical models and lidar observations. (ekstern lenke)
- Rebeca Marini; Konstantinos Vratsinis; Pieter-Jan Daems et al. (2025). An assessment of the metocean conditions in the Belgian offshore zone. (ekstern lenke)
- Yuanchen Wan; Etienne Cheynet; Yan Li et al. (2025). Wind conditions monitoring for solar collector array design: the case of Nevada Solar One. (ekstern lenke)
2021
- Etienne Cheynet; Martin Flügge; Joachim Reuder et al. (2021). The COTUR project: Remote sensing of offshore turbulence for wind energy application. (ekstern lenke)
- Etienne Cheynet; Martin Flügge; Joachim Reuder et al. (2021). Preliminary results of the COTUR project. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2021). Full-scale observations of bridge stay cable vibrations in a wet state. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2021). Observations of the turbulent near wake of a bridge deck. (ekstern lenke)
- Mohammad Nafisifard; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2021). Dual lidar wind measurements along an upstream horizontal line perpendicular to a suspension bridge. (ekstern lenke)
- Joachim Reuder; Mauro Ghirardelli; Stephan Thomas Kral et al. (2021). SUMO and SAMURAI – GFI/UiB drones for wind energy reserach. (ekstern lenke)
- Etienne Cheynet (2021). Wind-induced response of a 5 MW offshore wind turbine. (ekstern lenke)
- Etienne Cheynet (2021). Structural monitoring of a 5MW offshore wind turbine. (ekstern lenke)
- Mohammad Nafisifard; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2021). Observations of incoming turbulent flow by dual wind lidar mounted on a bridge deck. (ekstern lenke)
- Aoudou Midjiyawa Zakari; Etienne Cheynet; Joachim Reuder et al. (2021). Potential and challenges of wind measurements using met-masts in complex topography for bridge design: Part II – Spectral flow characteristics. (ekstern lenke)
- Joachim Reuder; Etienne Cheynet; Andrew Clifton et al. (2021). Recommendation on use of wind lidars. (ekstern lenke)
- Aoudou Midjiyawa Zakari; Etienne Cheynet; Heinrich Joachim Reuder et al. (2021). Potential and challenges of wind measurements using met-masts in complex topography for bridge design: Part I - Integral flow characteristics. (ekstern lenke)
- Etienne Cheynet (2021). Structural monitoring of OWTs for predictive maintenance. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjørnsson et al. (2021). Observations of bridge stay cable vibrations in dry and wet conditions: A case study. (ekstern lenke)
- Ibuki Kusano; Etienne Cheynet; Jasna Bogunovic Jakobsen et al. (2021). Aerodynamic study of a suspension bridge deck by CFD simulations, wind tunnel tests and full-scale observations. (ekstern lenke)
2017
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2017). Assessing the potential of a commercial pulsed lidar for wind characterisation at a bridge site. (ekstern lenke)
- Jungao Wang; Jonas Thor Snæbjörnsson; Jasna Bogunovic Jakobsen et al. (2017). Coupled Aerodynamic and Hydrodynamic Response of a Long Span Bridge Suspended from Floating Towers. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2017). Full-scale observation of the flow downstream of a suspension bridge deck. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2017). Measurements of Surface-Layer Turbulence in a Wide Norwegian Fjord Using Synchronized Long-Range Doppler Wind Lidars. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2017). Damping estimation of large wind-sensitive structures. (ekstern lenke)
- Jungao Wang; Etienne Cheynet; Jasna Bogunovic Jakobsen et al. (2017). Time-Domain Analysis of Wind-Induced Response of a Suspension Bridge in Comparison With the Full-Scale Measurements. (ekstern lenke)
- Jonas Thor Snæbjörnsson; Jasna Bogunovic Jakobsen; Etienne Cheynet et al. (2017). Full-scale monitoring of wind and suspension bridge response. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2017). Wind turbulence measurements above the sea in an open fjord inlet using long-range synchronized lidars. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Charlotte Obhrai (2017). Spectral characteristics of surface-layer turbulence in the North Sea. (ekstern lenke)
- Etienne Cheynet (2017). Spectral characteristics of offshore wind turbulence. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2017). Measurement of the wind coherence with synchronized long-range Doppler wind lidars. (ekstern lenke)
- Etienne Cheynet; Jonas Thor Snæbjörnsson; Jasna Bogunovic Jakobsen (2017). Temperature effects on the modal properties of a suspension bridge. (ekstern lenke)
2024
- Nicolo Daniotti; Jonas Thor Snæbjörnsson; Jasna Bogunovic Jakobsen et al. (2024). Vortex shedding in the wake of a fullscale bridge deck. (ekstern lenke)
- Eirik Finserås; Ignacio Herrera Anchustegui; Etienne Cheynet et al. (2024). Gone with the wind? Wind farm-induced wakes and regulatory gaps. (ekstern lenke)
- Hedda Wallestad; Etienne Cheynet; Astrid Nybø et al. (2024). Wind farm layout assessment in Sørlige Nordsjø II using the FLORIS framework and NORA3 dataset,. (ekstern lenke)
- Etienne Cheynet (2024). Energy variability: the case of wind energy. (ekstern lenke)
- Etienne Cheynet; Lin Li; Zhiyu Jiang (2024). Metocean conditions at two Norwegian sites for development of offshore wind farms. (ekstern lenke)
- Elias Villamil Fernandez; Etienne Cheynet; Ida Marie Solbrekke (2024). Evaluating the Offshore Wind Areas Suitability for Sustainable Energy Development in Norway: A Comparative Analysis. (ekstern lenke)
- Alexander Arvid Flem; Mauro Ghirardelli; Stephan Thomas Kral et al. (2024). Experimental Characterization of Propeller-Induced Flow (PIF) below a Multi-Rotor UAV. (ekstern lenke)
- Mali Ones; Etienne Cheynet; Joachim Reuder (2024). Extending Turbulence Measurements to 300m: Aiming to Retrieve All Wind Components from Vertical Velocity. (ekstern lenke)
- Etienne Cheynet (2024). Wind turbines and wind farms wakes. (ekstern lenke)
- Etienne Cheynet (2024). Wind Resource Assessment: Case Study. (ekstern lenke)
- Shauna Creane; Pedro Santos; Konstanze Kölle et al. (2024). IEA Wind Task 49: Reference Site Conditions for Floating Wind Arrays. (ekstern lenke)
2015
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2015). Full scale monitoring of wind and traffic induced response of a suspension bridge. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2015). Buffeting response of a bridge at the inlet of a fjord. (ekstern lenke)
- Jasna Bogunovic Jakobsen; Etienne Cheynet; Jonas Thor Snæbjörnsson et al. (2015). Assessment of wind conditions at a fjord inlet by complementary use of sonic anemometers and lidars. (ekstern lenke)
- Jasna Bogunovic Jakobsen; Etienne Cheynet; Jonas Thor Snæbjørnsson et al. (2015). Application of lidars for assessment of wind conditions on a bridge site. (ekstern lenke)
- Jasna Bogunovic Jakobsen; Etienne Cheynet; Jonas Thor Snæbjörnsson et al. (2015). Assessment of wind conditions at a fjord inlet by complementary use of sonic anemometers and lidars. (ekstern lenke)
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2015). Buffeting response of a bridge at the inlet of a fjord. (ekstern lenke)
- Jasna Bogunovic Jakobsen; Etienne Cheynet; Jonas Thor Snæbjørnsson et al. (2015). Application of lidars for assessment of wind conditions on a bridge site. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2015). Full scale monitoring of wind and traffic induced response of a suspension bridge. (ekstern lenke)
2020
- Etienne Cheynet; Martin Flügge; Joachim Reuder et al. (2020). Preliminary results of the COTUR project. (ekstern lenke)
- Etienne Cheynet; Nicolo Daniotti; Jasna Bogunovic Jakobsen et al. (2020). Improved long-span bridge modeling using data-driven identification of vehicle-induced vibrations. (ekstern lenke)
- Etienne Cheynet; Shengnan Liu; Muk Chen Ong et al. (2020). The influence of terrain on the mean wind flow characteristics in a fjord. (ekstern lenke)
- Etienne Cheynet (2020). Offshore wind potential in Norway and the North Sea. (ekstern lenke)
- Etienne Cheynet (2020). Panel discussion: “New Challenges in Wind-Structure interaction”. (ekstern lenke)
- Martin Flügge; Etienne Cheynet; Yngve Heggelund et al. (2020). The COTUR project: Remote sensing of offshore turbulence for wind energy application. (ekstern lenke)
2016
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2016). Wind-induced vibrations monitoring with satellite navigation. (ekstern lenke)
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2016). Full-scale observation of the flow downstream of a suspension bridge deck. (ekstern lenke)
- Jonas Thor Snæbjörnsson; Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen (2016). Performance evaluation of a suspension bridge excited by wind and traffic induced action. (ekstern lenke)
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2016). Buffeting response of a suspension bridge in complex terrain. (ekstern lenke)
- Etienne Cheynet; Jasna Bounovic Jakobsen (2016). Wind-induced vibrations of a suspension bridge: A case study in full-scale. (ekstern lenke)
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2016). Application of short-range dual-Doppler lidars to evaluate the coherence of turbulence. (ekstern lenke)
- Etienne Francois Cyprien Cheynet; Jasna Bogunovic Jakobsen; Benny Svardal et al. (2016). Wind Coherence Measurement by a Single Pulsed Doppler Wind Lidar. (ekstern lenke)
2019
- Joachim Reuder; Martin Flügge; Yngve Heggelund et al. (2019). The COTUR campaign - measuring offshore turbulence and coherence With lidars. (ekstern lenke)
- Etienne Cheynet (2019). Influence of the Measurement Height on the Vertical Coherence of Natural Wind. (ekstern lenke)
- Nicolo Daniotti; Etienne Cheynet; Jasna Bogunovic Jakobsen et al. (2019). Analysing wind-induced vibrations of a suspension bridge using GNSS data. (ekstern lenke)
- Etienne Cheynet; Jonas Thor Snæbjörnsson; Jasna Bogunovic Jakobsen (2019). Identifying Traffic-Induced Vibrations of a Suspension Bridge: A Modelling Approach Based on Full-Scale Data. (ekstern lenke)
- Nicolo Daniotti; Etienne Cheynet; Jasna Bogunovic Jakobsen et al. (2019). Damping Estimation from Full-Scale Traffic-Induced Vibrations of a Suspension Bridge. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2019). Flow Distortion Recorded by Sonic Anemometers on a Long-Span Bridge. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2019). Flow distortion recorded by sonic anemometers on a long-span bridge: Towards a better modelling of the dynamic wind load in full-scale. (ekstern lenke)
- Etienne Cheynet; Shengnan Liu; Muk Chen Ong et al. (2019). Influence of the local terrain on the mean flow characteristics in a fjord. (ekstern lenke)
- Martin Flügge; Yngve Heggelund; Joachim Reuder et al. (2019). COTUR - Estimating coherence and turbulence with LIDARs. (ekstern lenke)
- Joachim Reuder; Martin Flügge; Etienne Cheynet et al. (2019). The COTUR campaign - measuring offshore turbulence and coherence with lidars. (ekstern lenke)
2023
- Etienne Cheynet (2023). Wind turbines and wind farm characteristics. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2023). A study of bridge deck aerodynamics through full-scale surface pressure measurements. (ekstern lenke)
- Ignacio Herrera Anchustegui; Etienne Cheynet (2023). Gone with the wind? Wind farm-induced wakes and regulatory gaps. (ekstern lenke)
- Mauro Ghirardelli; Stephan Thomas Kral; Nicolas Carlo Müller et al. (2023). Flow Structure around a Multicopter Drone: A Computational Fluid Dynamics Analysis for Sensor Placement Considerations. (ekstern lenke)
2018
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2018). Complementary use of wind lidars and land-based met-masts for wind measurements in a wide fjord. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Joachim Reuder (2018). Velocity spectra and coherence estimates in the marine atmospheric boundary layer. (ekstern lenke)
- Jungao Wang; Etienne Cheynet; Jonas Thor Snæbjörnsson et al. (2018). Coupled aerodynamic and hydrodynamic response of a long span bridge suspended from floating towers. (ekstern lenke)
- Yngve Heggelund; Martin Flügge; Jasna Bogunovic Jacobsen et al. (2018). COTUR Measuring coherence and turbulence with lidars. (ekstern lenke)
- Etienne Cheynet; Hálfdán Ágústsson; Knut Harstveit (2018). Complementary use of wind lidars and land-based met-masts for wind characterization in a wide fjord. (ekstern lenke)
- Etienne Cheynet (2018). Hvordan kan vi se vinden i en fjord?. (ekstern lenke)
2014
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2014). Wind characteristics on a suspension bridge at the inlet of a fjord. (ekstern lenke)
- Etienne Cheynet; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson (2014). Wind-induced response of a bridge at the inlet of a fjord. (ekstern lenke)
2022
- Rieska Mawarni Putri; Etienne Cheynet; Charlotte Obhrai et al. (2022). Turbulence in a coastal environment: the case of Vindeby. (ekstern lenke)
- Etienne Cheynet (2022). Non-neutral Coherence of turbulence during the COTUR campaign. (ekstern lenke)
- Nicolo Daniotti; Jasna Bogunovic Jakobsen; Jonas Thor Snæbjörnsson et al. (2022). Full-scale measurements of wind-induced surface pressures on a bridge deck. (ekstern lenke)
- Etienne Cheynet; Ida Marie Solbrekke; Jan Markus Diezel et al. (2022). A one-year comparison of new wind atlases over the North Sea. (ekstern lenke)
- Joachim Reuder; Etienne Cheynet (2022). Offshore Wind Ressources. (ekstern lenke)
- Etienne Cheynet; Ida Marie Solbrekke; Jan Markus Diezel et al. (2022). A one-year comparison of new wind atlases over the North Sea. (ekstern lenke)
- Etienne Cheynet; Lin Li; Zhiyu Jiang (2022). Metocean Conditions at Two Norwegian Sites for Development of Offshore Wind Farms. (ekstern lenke)
- Etienne Cheynet (2022). COTUR workshop: Non-neutral Coherence of turbulence during the COTUR campaign. (ekstern lenke)
- Etienne Cheynet; Nicolo Daniotti; Jasna Bogunovic Jakobsen et al. (2022). Unfrozen skewed turbulence for wind loading on structures. (ekstern lenke)
Prosjekter
BEL-FLOAT (2023-2026): The BEL-Float project focuses on developing Belgium's expertise in floating wind technology through academic innovation. The project aims to prepare new researchers with the necessary skills for floating wind energy and to strengthen the Belgian-Norwegian partnership in offshore wind.
ImpactWind SouthWest (2022-2027): ImpactWind SouthWest is a project led by NORCE, aiming to transform offshore wind development through collaboration, an open database, a research program, and educational initiatives. It aims to make the licensing process for Norwegian offshore wind faster, contributing to sustainable energy and job creation in Norway
LOWT (2021-2025): Large Offshore Wind Turbines (LOWT):structural design accounting for non-neutral wind conditions
This project will develop new knowledge and models to improve the design basis for large floating wind turbines (LOWT)(>12MW) in freewind and wake conditions. Observations from Hywind Scotland have shown the thermal stratification of the atmosphere can substantially affect the structural response of a wind turbine to the incoming turbulent flow. The first objective is to use wind data from several offshore sites to characterise the wind field in non-neutral atmospheric conditions. The project will use high-frequency wind data combined with a brand new remote sensing dataset (COTUR). In the COTUR campaign the incoming flow over the ocean was recorded, both within and above the surface layer, thus providing new insight on the applicability surface-layer scaling to model the turbulent wind loads on LOWT. This unique dataset will be analysed for the first time to the to indicate whether the turbulence models used in the standards, which mainly relies on surface-layer scaling, are appropriate or not. The final output will be to recommend suitable wind and coherence model for in non-neutral conditions as input to free wind aeroelastic simulations and DWM models offshore. The second objective is to validate the simulated wind turbine response using full scale data from offshore wind farms (Alpha Ventus, Sheringham Shoal, and Zefyros/Hywind Demo). The validated simulation tools will then be used to quantify the effect of non-neutral atmospheric conditions on future LOWT (>12MW) to ensure safe and cost-effective design in the next generation of offshore wind farms in Norway and beyond. The final focus of the project is wake simulations of LOWT in non-neutral conditions using DWM model. High-fidelity CFD simulations will be used to include variable velocity shear in the DWM method and validate the wake meandering in non-neutral conditions. The non-neutral wind spectra and coherence from the data analysis work will be used as input for the DWM simulations.
COTUR (2018-2020): Measuring coherence and turbulence with lidars (COTUR)
The size of offshore wind turbines has increased significantly since the installation of the world’s first commercial offshore wind turbine at Vindeby in 1991. The average offshore wind turbine capacity has increased from 500 kW in the 1990s to 3 MW by the end of 2010. Today, the largest offshore wind turbines have a rated power of 9 MW and a rotor diameter of 164 meters. Large, floating wind turbines pose new challenges compared to bottom-fixed turbines. In particular, the Hywind Scotland wind farm posed new challenges with respect to turbulence and coherence. There is a need for a better understanding of the horizontal coherence over large rotors offshore, but few measurements are available for such analyses. The main objective of the project is to improve the understanding of offshore wind coherence through measurements with lidars. The measurements will form a new, unique and highly relevant dataset for future offshore wind research. The collected data and corresponding meta-data will be stored in a database for later analysis.