Retrieval of vegetation clumping index using hot spot signatures measured by POLDER instrument

Lacaze, Roselyne

doi:10.1016/s0034-4257(01)00241-3

Cited by 117 publications

(51 citation statements)

References 40 publications

(39 reference statements)

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“…Analogously, the HDS index ((ρ HS − ρ DS )/ρ DS ), which was proposed by Lacaze et al [29], has been widely used in recent research.…”

Section: Ndhd Ndvi and Hdvimentioning

confidence: 99%

“…2016, 8, 6 7 of 15 ρ )/ρ ), which was proposed by Lacaze et al [29], has been widely used in recent research. For HDS, the problem of mixed pixels becomes prominent at Proba-V's 300 m resolution: Some pixels containing mixed cropland and bare land demonstrate low ρ values, resulting in abnormal HDS values.…”

Section: Simulated Reflectance In Red and Nir Bandmentioning

confidence: 99%

“…Multi-angular observations can capture the uneven scattering of sunlight by vegetation, which can be described by the bidirectional reflectance distribution function (BRDF) related to the biophysical structural information [24,[26][27][28]. The hotspot-darkspot index (HDS) calculated from multi-angular optical remote-sensing data is capable of representing the geometric structures of vegetation [29]. A high HDS index results from a strong contrast between the hotspot and darkspot reflectances, which is a manifestation of the roughness of the canopy surface [26].…”

Section: Introductionmentioning

confidence: 99%

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A Method for Estimating the Aerodynamic Roughness Length with NDVI and BRDF Signatures Using Multi-Temporal Proba-V Data

Niu

et al. 2016

Remote Sensing

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Aerodynamic roughness length is an important parameter for surface fluxes estimates. This paper developed an innovative method for estimation of aerodynamic roughness length (z 0m ) over farmland with a new vegetation index, the Hot-darkspot Vegetation Index (HDVI). To obtain this new index, the normalized-difference hot-darkspot index (NDHD) is introduced using a semi-empirical, kernel-driven bidirectional reflectance model with multi-temporal Proba-V 300-m top-of-canopy (TOC) reflectance products. A linear relationship between HDVI and z 0m was found during the crop growth period. Wind profiles data from two field automatic weather station (AWS) were used to calibrate the model: one site is in Guantao County in Hai Basin, in which double-cropping systems and crop rotations with summer maize and winter wheat are implemented; the other is in the middle reach of the Heihe River Basin from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) project, with the main crop of spring maize. The iterative algorithm based on Monin-Obukhov similarity theory is employed to calculate the field z 0m from time series. Results show that the relationship between HDVI and z 0m is more pronounced than that between NDVI and z 0m for spring maize at Yingke site, with an R 2 value that improved from 0.636 to 0.772. At Guantao site, HDVI also exhibits better performance than NDVI, with R 2 increasing from 0.630 to 0.793 for summer maize and from 0.764 to 0.790 for winter wheat. HDVI can capture the impacts of crop residue on z 0m , whereas NDVI cannot.

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“…Analogously, the HDS index ((ρ HS − ρ DS )/ρ DS ), which was proposed by Lacaze et al [29], has been widely used in recent research.…”

Section: Ndhd Ndvi and Hdvimentioning

confidence: 99%

Section: Simulated Reflectance In Red and Nir Bandmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Method for Estimating the Aerodynamic Roughness Length with NDVI and BRDF Signatures Using Multi-Temporal Proba-V Data

Niu

et al. 2016

Remote Sensing

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“…Compared with LAI inversion from remote sensing, the clumping index retrieval from remote sensing data is less studied. Previous studies mainly focus on clumping index retrieving using Hotspot and Darkspot near-infrared (NIR) reflectance acquired by the multi-angular POLDER sensor [14,18]. However, the spatial resolution (6 km) of clumping index retrieved from POLDER data is too low to meet the demands of generating global 1 km or 500 m LAI products using MODIS data.…”

mentioning

confidence: 99%

Spatial and temporal variations of forest LAI in China during 2000–2010

Liu

Chen

et al. 2012

Chin. Sci. Bull.

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Forests are crucial terrestrial ecosystems. Their leaf area index (LAI) is a key parameter determining the exchange of matter and energy between the atmosphere and the ground surface. In this study, MOD 09A1 and MCD 43A1 data were input into an inversion model based on the 4-scale geometric optical model to retrieve 8-d 500 m LAI products in China during the period 2000 to 2010. The resulting LAI product was validated using LAI measured in 6 typical areas. The spatial and temporal variations of forest LAI and its relationships with temperature and precipitation were analyzed. The results show that the accuracy of the 500 m LAI product was above 70% in the 6 typical areas, indicating the reliability of this product.

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“…Here, we assumed that the value of was 0.5, following Lacaze et al (2002), who showed that was about 0.5 for Canadian boreal coniferous forests.…”

Section: Modifications Made To Account For the Canopy-intercepted Snomentioning

confidence: 99%

Impact of land-use changes on snow in a forested region with heavy snowfall in Hokkaido, Japan

Suzuki¹,

Kodama²,

Nakai³

et al. 2011

Hydrological Sciences Journal

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We simulated snow processes in a forested region with heavy snowfall in Japan, and evaluated both the regional-scale snow distribution and the potential impact of land-use changes on the snow cover and water balances over the entire domain. SnowModel reproduced the snow processes at open and forested sites, which were confirmed by snow water equivalent (SWE) measurements at two intensive observation sites and snow depth measurements at the Automated Meteorological Data Acquisition System sites. SnowModel also reproduced the observed snow distribution (from the MODIS snow cover data) over the simulation domain during thaw. The observed SWE was less at the forested site than at the open site. The SnowModel simulations showed that this difference was caused mainly by differences in sublimation. The type of land use changed the maximum SWE, onset and duration of snowmelt, and the daily snowmelt rate due to canopy snow interception.Key words deforestation; canopy snow interception; sublimation; snowmelt rate; turbulent flux Impact de changements d'occupation du sol sur la neige dans une région forestière fortement enneigée de Hokkaido, Japon Résumé Nous avons simulé les processus neigeux dans une région forestière fortement enneigée au Japon, et évalué à la fois la répartition de la neige à l'échelle régionale et l'impact potentiel des changements d'occupation du sol sur le couvert neigeux et sur le bilan hydrologique pour l'ensemble du domaine. SnowModel reproduit les processus neigeux dans les sites ouverts et forestiers, ce qui est confirmé par des mesures d'équivalent en eau de la neige en deux sites d'observation intensive et des mesures de la profondeur de la neige sur les sites du système automatique d'acquisition de données météorologiques. SnowModel reproduit également la distribution de la neige observée (à partir de données MODIS de couvert neigeux) sur le domaine de la simulation au cours de la fonte nivale. L'équivalent en eau de la neige observé est inférieur pour le site forestier que pour le site ouvert. Les simulations avec SnowModel montrent que cette différence est principalement causée par des différences en matière de sublimation. Le type d'occupation du sol change l'équivalent en eau de la neige maximum, le début et la durée de la fonte nivale, et le taux de fonte journalier en raison de l'interception de la neige par la canopée.

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Retrieval of vegetation clumping index using hot spot signatures measured by POLDER instrument

Cited by 117 publications

References 40 publications

A Method for Estimating the Aerodynamic Roughness Length with NDVI and BRDF Signatures Using Multi-Temporal Proba-V Data

A Method for Estimating the Aerodynamic Roughness Length with NDVI and BRDF Signatures Using Multi-Temporal Proba-V Data

Spatial and temporal variations of forest LAI in China during 2000–2010

Impact of land-use changes on snow in a forested region with heavy snowfall in Hokkaido, Japan

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