Leaf area index (LAI) is a dimensionless quantity that characterizes plant canopies. It is defined as the one-sided green leaf area per unit ground surface area (LAI = leaf area / ground area, m 2 / m 2) in broadleaf canopies. In conifers, three definitions for LAI have been used. In case you don't use a build tool such as Maven or Gradle, we also offer a complete distribution package containing binaries, source, javadoc and dependencies in the form of a convenient.zip file, which you can download from our bintray binary repository. Sources Thymeleaf's source code is available on GitHub. Here are the main repositories.
The LAI 300m Version 1 product has been validated following the guidelines proposed by the CEOS Land Product Validation (LPV) group. It consists in an inter-comparison with existing global products (LAI 1km V1 and V2 and MODIS C6) using the LANDVAL network of sites to perform the statistical analysis and a direct comparison with ground–based reference maps (e.g. From R&D project).
Details are given in the.The main added value of the 300m LAI products is their finer spatial resolution while keeping a good consistency with the 1km LAI. LAI 300m provides a NRT estimate, which could display some instability, and three consolidated modes calculated after one, two and five dekads. Users are then advised to use the first prediction cautiously and to preferably wait for the first consolidated value after 10 days. Algorithm adaptation is in progress to improve the estimate of NRT values.Global map of PROBA-V LAI 300m for the first dekad of July 2017Sub-continental maps over North America in June 2017 and South America in January 2017.The accuracy of the300m LAI products is assessed over the period 2014-2017 using ground-based reference maps generated according to CEOS LPV guidelines.
The LAI 1km version 1 and version 2 and the MODIS C6 LAI products are also compared for benchmarking.PROBA-V LAI V1 300m compared with ground-based maps at full resolution (vertical and horizontal bars correspond to the standard deviation over each in-situ site) and 3kmx3km. Dashed lines correspond to the 1:1 line and GCOS optimal uncertainty level; red line corresponds to the linear fit using Major Axis Regression.Similar comparison to 3kmx3km for PROBA-V LAI 1km Version 1, PROBA-V LAI 1km Version 2 and MODIS LAI C6.This accuracy assessment is updated every year using the most recent ground reference data available. The results obtained on the 2018 LAI products are presented in the. In addition, every year, it is checked that the Collection 300m LAI products capture well the impact of some environmental events on vegetation, like hail storm or large fires in the figures below.Maps of LAI 300m before (June 20) and after (July 10) a hail storm in South Dakota, USA. The scar, with LAI values close to zero, is clearly visible.Temporal profiles of LAI products over sites damaged by fires in 2017 in Chile and Portugal.According to the results of these quality assessment exercses, the 300m LAI version 1 products are in “demonstration”. A wide range of models used in agriculture, ecology, carbon cycling, climate and other studies use the LAI to quantify the amount of leaf material present in a given environment to correctly represent radiation, heat, water, and various gas exchanges with the overlying atmosphere or the underlying soil.
The main uses of LAI are in Soil-Vegetation-Atmosphere-Transfer schemes, biogeochemical cycles models, agro-meteorology fro crop assessment, which often require long time series at various temporal and spatial scales. The LAI 1km Version 1 and Version 2 products have been validated following the guidelines proposed by the CEOS Land Product Validation (LPV) group. It consists in an inter-comparison with existing global products at global and regional scales using the BELMANIP-2 network of sites to perform the statistical analysis and a direct comparison with ground –based reference maps. This procedure was applied on both SPOT/VGT and PROBA-V products.
The analysis and results are presented in.The main improvement of Version 2 compared to Version 1 is the absence of missing data. Further, Version 2 provides a near real time estimate while Version 1 values are representative of 12 days in the past comparing to the latest day of the synthesis period due to the time compositing method applied.PROBA-V LAI 1km Version 2 (left) and Version 1 for the first dekad of May 2014.The accuracy of LAI products is assessed over the year 2014 using ground-based reference maps generated according to CEOS LPV guidelines in the (filled symbols in the graphs below). Due to the limited number of concomitant ground measurements, data collected during different years over stable forest and grassland sites of are added to the comparison (unfilled symbols in the graphs below).PROBA-V LAI V2, V1 and MODIS LAI C5 compared with ground-based maps. Dashed lines correspond to the 1:1 line and GCOS uncertainty levels, and continuous yellow line to the linear fit using Major Axis Regression.This accuracy assessment is updated every year using the most recent ground reference data available.
The results obtained on the 2018 LAI products are presented in the. In addition, every year, it is checked that the LAI products capture well the impact of some environmental events on vegetation, like hail storm or large fires.Maps of LAI 1km V2 (left) and V1 (right) before and after a hail storm in South Dakota, USA, end of June 2018. The scar, with LAI values close to zero, is clearly visible.Temporal profiles of LAI products over sites damaged by fires in Chile and Portugal.According to the CEOS/LPV validation hierarchy the LAI Version 1 is validated Stage 2 “ product accuracy assessed over widely distributed set of location and time periods via several ground truth and validation efforts.
Spatial and temporal consistency of the product and with similar products has been evaluated over globally representative locations and time periods. Results are published in peer-reviewed literature”. Version 2 will reach Stage 2 as soon as validation results are published in peer-reviewed literature.According to the results of these assessments, the LAI 1km version 1 products are in “operational”, while version 2 products are in 'operational' stage. A wide range of models used in agriculture, ecology, carbon cycling, climate and other studies use the LAI to quantify the amount of leaf material present in a given environment to correctly represent radiation, heat, water, and various gas exchanges with the overlying atmosphere or the underlying soil.
The main uses of LAI are in Soil-Vegetation-Atmosphere-Transfer schemes, biogeochemical cycles models, agro-meteorology fro crop assessment, which often require long time series at various temporal and spatial scales.
Comments are closed.
|
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
March 2023
Categories |