Determining On-site Variability of CO2 and H2O Fluxes Using Footprint and LiDAR Data
Lead Research Organisation:
Swansea University
Department Name: School of the Environment and Society
Abstract
Understanding the exchange of energy and gases between the earth's surface and the lower atmosphere is essential for answering many questions related to, e.g., the global carbon budget, ecosystem functioning, air pollution mitigation, greenhouse gas emissions, weather forecasting, and projections of climate change. However, uncertainties in carbon dioxide (CO2) and water vapour (H2O) budgets limit our ability to reproduce and project these exchange processes. Exchange processes are usually analysed based on micrometeorological measurements from tall flux towers, thought to be representative of large area averages. A limitation of this approach is that the actual source areas of these fluxes are not always known and that the impact of land-surface heterogeneity (at small or large scale) on the fluxes is not yet completely understood. The micrometeorological measurements of the major carbon flux networks around the world, such as Ameriflux, Canadian Carbon Program, CarboEurope (in which the UK plays a prominent role) and Oz-Net, are essential to validate global estimates of CO2 sources and sinks, to develop and validate land surface models and to understand the sensitivity of CO2 fluxes under changing climate conditions. Unfortunately, flux tower measurements currently suffer from substantial uncertainty, which is primarily due to the indeterminate relationship of fluxes and their source areas; at present our current understanding can explain 60-80% of the variance of the fluxes. The overall goal of this project is to incorporate information on topography and structure of vegetation (tree height, canopy depth, and foliage density) in footprint estimates and thereby substantially reducing the potential errors in the calculation of the CO2 and H2O budgets. The selected forested sites consist of the very few long-term flux stations within the boreal forest biomes and represent the three dominant species of the boreal forest (jack pine, black spruce, aspen). The combination of these three forest stands will provide data that is sufficiently representative to allow for upscaling to the boreal forest biome scale. The boreal forest constitutes the world's second largest forested biome (after the tropical forest) and plays an important role in regulating the climate of the northern hemisphere and in the global carbon cycle. The footprint model developed by the PI and widely used by the international community will be applied on long-term data sets to estimate the size and location of the area containing the sources or sinks (footprint) of CO2 and H2O fluxes measured at the three sites. The footprints will account for, and depend on, atmospheric conditions, such as wind speed and boundary layer stability, and surface characteristics, e.g. roughness. This footprint model is one of very few models that are valid over a huge range of stratifications and receptor heights. The major improvement of the footprint model will incorporate three-dimensional information on the structure of the forest, derived from airborne scanning LiDAR measurements, leading to exceptionally detailed high temporal resolution source information. Unlike data from passive sensors, the unique LiDAR data set provides information from within the tree canopy. The results will be used to analyse impacts of structure of vegetation and small changes in elevation on the net CO2 and H2O fluxes. The new understanding will assist future studies of upscaling from flux towers to the spatially heterogeneous boreal forest landscape and will reduce the uncertainty in the modelling of carbon budgets at local, regional and continental scale. It will lead to a greater understanding of local structural effects on carbon sources and sinks and thus the dynamics of carbon cycling and to major improvements of the description of these exchange processes in land surface models. Hence, the new insights will help reducing uncertainty in projections of climate change.
People |
ORCID iD |
Natascha Kljun (Principal Investigator) |
Publications
Markkanen T
(2010)
A numerical case study on footprint model performance under inhomogeneous flow conditions A numerical case study on footprint model performance under inhomogeneous flow conditions
in Meteorologische Zeitschrift
Kljun N
(2015)
A simple two-dimensional parameterisation for Flux Footprint Prediction (FFP)
in Geoscientific Model Development
Haszpra, Laszlo
(2010)
Atmospheric Greenhouse Gases: The Hungarian Perspective
Chasmer L
(2011)
Characterizing vegetation structural and topographic characteristics sampled by eddy covariance within two mature aspen stands using lidar and a flux footprint model: Scaling to MODIS
in Journal of Geophysical Research
Gelybó G
(2013)
Effect of spatial heterogeneity on the validation of remote sensing based GPP estimations
in Agricultural and Forest Meteorology
Bye I
(2017)
Estimating forest canopy parameters from satellite waveform LiDAR by inversion of the FLIGHT three-dimensional radiative transfer model
in Remote Sensing of Environment
Vesala T
(2008)
Flux and concentration footprint modelling: state of the art.
in Environmental pollution (Barking, Essex : 1987)
Chasmer L
(2008)
Influences of vegetation structure and elevation on CO 2 uptake in a mature jack pine forest in Saskatchewan, Canada
in Canadian Journal of Forest Research
Hopkinson C
(2013)
Integrating terrestrial and airborne lidar to calibrate a 3D canopy model of effective leaf area index
in Remote Sensing of Environment
Hiller R
(2010)
Interpreting CO2 Fluxes Over a Suburban Lawn: The Influence of Traffic Emissions
in Boundary-Layer Meteorology
Shendryk I
(2014)
Low-Density LiDAR and Optical Imagery for Biomass Estimation over Boreal Forest in Sweden
in Forests
Hall F
(2011)
PHOTOSYNSAT, photosynthesis from space: Theoretical foundations of a satellite concept and validation from tower and spaceborne data
in Remote Sensing of Environment
Van Gorsel E
(2013)
Primary and secondary effects of climate variability on net ecosystem carbon exchange in an evergreen Eucalyptus forest
in Agricultural and Forest Meteorology
Van Beijma S
(2014)
Random forest classification of salt marsh vegetation habitats using quad-polarimetric airborne SAR, elevation and optical RS data
in Remote Sensing of Environment
Hilker T
(2010)
Remote sensing of photosynthetic light-use efficiency across two forested biomes: Spatial scaling
in Remote Sensing of Environment
Mahoney C
(2014)
Slope Estimation from ICESat/GLAS
in Remote Sensing
Barcza Z
(2009)
Spatial representativeness of tall tower eddy covariance measurements using remote sensing and footprint analysis
in Agricultural and Forest Meteorology
Los S
(2012)
Vegetation height and cover fraction between 60° S and 60° N from ICESat GLAS data
in Geoscientific Model Development
Description | ARSF direct support |
Amount | £213,055 (GBP) |
Funding ID | EU10-01 |
Organisation | Natural Environment Research Council |
Department | Airborne Research and Survey Facility (ARSF) |
Sector | Academic/University |
Country | United Kingdom |
Start |
Description | International Exchanges |
Amount | € 800 (EUR) |
Organisation | University of Innsbruck |
Department | International Relations Office |
Sector | Academic/University |
Country | Austria |
Start |
Description | International Exchanges |
Amount | £3,000 (GBP) |
Funding ID | IE110132 |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start |
Description | International communication |
Amount | € 500 (EUR) |
Funding ID | 06-12718 |
Organisation | Austrian Research Community |
Sector | Private |
Country | Austria |
Start |
Description | NCEO EO Mission Support |
Amount | £31,090 (GBP) |
Funding ID | NCEO EO Mission Support 2009 |
Organisation | National Centre for Earth Observation |
Sector | Academic/University |
Country | United Kingdom |
Start |
Description | NCEO PhD Studentship |
Amount | £60,437 (GBP) |
Organisation | National Centre for Earth Observation |
Sector | Academic/University |
Country | United Kingdom |
Start | 09/2009 |
End | 10/2012 |
Description | OCE Distinguished Visiting Scientist |
Amount | $12,500 (AUD) |
Organisation | Commonwealth Scientific and Industrial Research Organisation |
Sector | Public |
Country | Australia |
Start |
Description | Percy Sladen Memorial Fund |
Amount | £300 (GBP) |
Funding ID | Kljun-30-03-2011 |
Organisation | Linnean Society of London |
Department | Percy Sladen Memorial Fund |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start |
Description | Lund University, Sweden |
Organisation | Lund University |
Country | Sweden |
Sector | Academic/University |
PI Contribution | Field work at Norunda research station, analysis of data, footprint modelling, writing proposals and publications |
Collaborator Contribution | Field work at Norunda research station, analysis of data, writing proposals and publications |
Impact | See publications. |
Start Year | 2013 |
Description | University of Lethbridge, Canada |
Organisation | University of Lethbridge |
Country | Canada |
Sector | Academic/University |
PI Contribution | Planning of data collection, analysis of data, writing peer-reviewed articles |
Collaborator Contribution | Data collection, field work planning, pre-processing of raw-data |
Impact | See publications |
Start Year | 2008 |