Estimating forest parameters from top of atmosphere multi-angular radiance data using coupled radiative transfer models

ABSTRACT -Traditionally, the estimation of forest parameters using physically-based canopy radiative transfer models (RT

A 28-day oral dose toxicity study enhanced to detect endocrine effects of hexabromocyclododecane in wistar rats

A 28-day repeated dose study in rats (OECD407) enhanced for endocrine and immune parameters was performed with hexabromocyclododecane (HBCD). Rats were exposed by daily gavage to HBCD dissolved in corn oil in 8 dose groups with doses ranging between 0 and 200 mg/kg bw per day (mkd). Evaluation consisted of dose-response analysis with calculation of a benchmark dose at the lower 95% one-sided confidence bound (BMDL) at predefined critical effect sizes (CESs) of 10-20%. The most remarkable findings were dose-related effects on the thyroid hormone axis, that is, decreased total thyroxin (TT4, BMDL 55.5 mkd at CES--10%), increased pituitary weight (29 mkd at 10%) and increased immunostaining of TSH in the pituitary, increased thyroid weight (1.6 mkd at 10%), and thyroid follicle cell activation. These effects were restricted to females. Female rats also showed increased absolute liver weights (22.9 mkd at 20%) and induction of T4-glucuronyl transferase (4.1 mkd at 10%), suggesting that aberrant metabolization of T4 triggers feedback activation of the thyroid hormone system. These effects were accompanied by possibly secondary effects, including increased cholesterol (7.4 mkd at 10%), increased tibial bone mineral density (> 49 mkd at 10%), both in females, and decreased splenocyte counts (0.3-6.3 mkd at 20%; only evaluated in males). Overall, female rats appeared to be more sensitive to HBCD than male rats, and an overall BMDL is proposed at 1.6 mkd, based on a 10% increase of the thyroid weight, which was the most sensitive parameter in the sequence of events

PROSPECT+SAIL: 15 Years of Use for Land Surface Characterization

Presented at Geoscience and Remote Sensing Symposium, 2006. IGARSS 2006. IEEE International Conference on , vol., no., pp.1992-1995, July 31 2006-Aug. 4 2006The combined PROSPECT leaf optical properties model and SAIL canopy bidirectional reflectance model, i.e. PROSAIL, has been used for about fifteen years to increase our understanding of plant canopy spectral and bidirectional reflectance in the solar domain and to develop new methods of vegetation biophysical properties retrieval. It links the spectral variation of canopy reflectance with its directional variation. This link is the key to simultaneously estimate biophysical/structural canopy variables for applications in agriculture, plant physiology, and forestry at different scales. PROSPECT and SAIL are still evolving: they have undergone recent improvements both at the leaf and the plant levels and became one of the most popular radiative transfer tools in these domains due to their ease of use, their robustness, and because they have been validated by many lab/field/space experiments over the years. This paper is intended to review this subject, which has been extensively researched in optical remote sensingWe are grateful to the space agencies (CNES, ESA, EU, NASA, NLR) and national remote sensing programs (PNTS, CalSpace) for funding provided during the last 15 years.Peer reviewe

Estimating forest parameters from top of atmosphere multi-angular radiance data using coupled radiative transfer models

Traditionally, the estimation of forest parameters using physically-based canopy radiative transfer models (RT) requires correcting the remote sensing data to top-of-canopy (TOC) level by inverting an atmosphere RT model. By coupling the same canopy and atmosphere models, it is possible to simulate the top-of-atmosphere (TOA) radiance and to work directly with the measured TOA radiance data, thus avoiding the correction to TOC level. Many studies discussed the increased potential of multiangular data for parameter estimation, especially for forests, which have strong directional properties. These studies, however, were based on TOC data. In this study, we investigate the potential of multiangular data at TOA level, based on a case study for three Norway spruce stands in the Czech Republic, using multi-angular CHRIS data and the coupled SLC-MODTRAN model. The coupled model provided satisfactory TOA simulations of spectral and angular signatures, and the dimensionality of the parameter estimation problem increased with increasing angular sampling. Canopy cover, fraction of brown material, leaf chlorophyll and leaf dry matter content were estimated using all possible angular combinations. No combination was best for all parameters

A Bayesian object-based approach for estimating vegetation biophysical and biochemical variables from APEX at-sensor radiance data

Vegetation variables such as leaf area index (LAI) and leaf chlorophyll content (Cab) are important inputs for vegetation growth models. LAI and Cab can be estimated from remote sensing data using either empirical or physically-based approaches. The latter are more generally applicable because they can easily be adapted to different sensors, acquisition geometries, and vegetation types. They estimate vegetation variables through inversion of radiative transfer models. Such inversions are ill-posed but can be regularized by coupling models, by using a priori information, and spatial and/or temporal constraints. Striving to improve the accuracy of LAI and Cab estimates from single remote sensing images, this contribution proposes a Bayesian object-based approach to invert at-sensor radiance data, combining the strengths of regularization by model coupling, as well as using a priori data and object-level spatial constraints. The approach was applied to a study area consisting of homogeneous agricultural fields, which were used as objects for applying the spatial constraints. LAI and Cab were estimated from at-sensor radiance data of the Airborne Prism EXperiment (APEX) imaging spectrometer by inverting the coupled SLC-MODTRAN4 canopy-atmosphere model. The estimation was implemented in two steps. In the first step, up to six variables were estimated for each object using a Bayesian optimization algorithm. In the second step, a look-up-table (WT) was built for each object with only LAI and Cab as free variables, constraining the values of all other variables to the values obtained in the first step. The results indicated that the Bayesian object-based approach estimated LAI more accurately (R-2 = 0.45 and RMSE = 1.0) than a LUT with a Bayesian cost function (LUT-BCF) approach (R-2 = 022 and RMSE = 2.1), and Cab with a smaller absolute bias (-9 versus -23 mu g/cm(2)). The results of this study are an important contribution to further improve the regularization of ill-posed RT model inversions. The proposed approach allows reducing uncertainties of estimated vegetation variables, which is essential to support various environmental applications. The definition of objects and a priori data in cases where less extensive ground data are available, as well as the definition of the observation covariance matrix, are critical issues which require further research. (C) 2013 Elsevier Inc All rights reserved

Progress on the development of an integrated canopy fluorescence model

2003 - International Geoscience and Remote Sensing Symposium, IGARSS'03, pp. 601-603 Vol.1, Toulouse (France), 21-25/7/2004Typical environmental plant stress factors are excess of light, deficiencies of water and nutrients, temperature extremes, diseases, pests and pollutants. An early indicator for vegetation status and vitality by means of remote sensing would therefore serve a range of applications such as renewable resource management and precision farming. Vegetation fluorescence is a direct indicator for plant physiology, and could therefore be used as an early indicator for vegetation health status and vitality. Vegetation chlorophyll fluorescence is a function of photochemical processes and efficiency, which are directly linked to primary productivity and CO2 flux from the atmosphere, and could therefore also provide a means to assess the terrestrial carbon cycle. A study was launched in October 2002 by the European Space Agency to advance the underlying science of a possible future vegetation fluorescence space mission by addressing the need for an integrated canopy fluorescence model. The objective of this study is to review and advance existing fluorescence models at the leaf level and to integrate these into canopy models in order to simulate the combined spectral reflected radiance and passive fluorescence emission signals. This model is to be validated with new and existing field campaign measurements. This paper reports on the status of this project. The input radiometric and photosynthetic variables have been selected to define the vegetation fluorescence signal consisting of far-red and red chlorophyll fluorescence as spectral emission features, normalized to the canopy illumination levels, when linked to the leaf-level fluorescence reflectance-transmittance model defined in this study. Measurement protocols to validate fluorescence-leaf models will be definedPeer reviewe

Cladribine therapy for systemic mastocytosis

Patients with systemic mastocytosis (SM) can suffer from disabling symptoms related to mast cell mediator release or mast cell infiltration, requiring mast cell eradication. In the present absence of any curative therapy, a recent case report describing the efficacy of cladribine showed promising results. In a pilot study, the efficacy of cladribine (0.10-0.13 mg/kg in a 2-hour infusion, days 1-5; repeated at 4-8 weeks until 6 cycles) was studied. Ten patients with SM with severe symptoms were treated. Four patients were classified as having indolent or smoldering mastocytosis, 3 as having aggressive systemic mastocytosis, and 3 as having SM with an accompanying hematologic malignancy. Nine patients received 6 courses, 1 patient stopped because of toxicodermia. All responded concerning signs, symptoms, and mast cell parameters (serum tryptase and urinary histamine metabolite excretion), although none achieved a complete remission. Prolonged follow-up is required, as response is ongoing in most cases. One patient relapsed within 11 months and showed a second response. Side effects were mainly related to bone marrow suppression. Single-agent cladribine is an effective and relatively safe treatment for severe systemic mastocytosis. The optimal dose and schedule need to be explored. (C) 2003 by The American Society of Hematology

Assessing gross primary production from solar-induced chlorophyll fluorescence: field results and integration into biogeophysical models

Geophysical Research Abstracts, Vol. 10, EGU2008-A-07911, 2008 SRef-ID: 1607-7962/gra/EGU2008-A-07911 EGU General Assembly 2008Light energy absorbed by photosynthetic antenna pigments is only partly used up in photochemical processes, the remainder being dissipated through heat production or chlorophyll fluorescence. The possibility to use remote sensing methods to measure fluorescence emitted by the plants under natural solar illumination (solar-induced fluorescence, SIF) paves the way for the remote assessment of electron transport and photosynthetic processes. Although less straightforward than for near-field pulsesaturated fluorescence, the interpretation of solar-induced fluorescence is advancing, through the development of novel models of variable detail. The family of Earth Explorer missions is the result of a strategy within the Living Planet Programme of the European Space Agency where missions are designed to address critical and specific issues raised by the scientific community whilst demonstrating breakthrough technology in observing techniques. Following the selection of the first six Explorer missions, currently under development and implementation, the Agency released in March 2005 a new Call for Ideas focused on key processes that are fundamental for improving our understanding of the changing Earth System. The proposals were reviewed by scientific teams and assessed technically and programmatically, leading to the selection of six candidates in May 2006 to enter dedicated assessment studies. Amongst these missions is the FLuorescence EXplorer – FLEX – a mission dedicated to observing and monitoring SIF globally together with additional complementary information on the vegetation cover and its environmental setting allowing a correct interpretation of the observed SIF signal. In the framework of the FLEX mission assessment phase dedicated airborne campaigns and study activities were initiated in order to proof the mission concept, to consolidate the mission requirements and to develop the appropriate data processing tools and the necessary methods for assimilating the SIF signal into biogeophysical models with explicit description of vegetation dynamics. An overview of the mission is presented, together with a summary of its main preliminary results.Peer reviewe

Canopy spectral invariants for remote sensing and model applications

The concept of canopy spectral invariants expresses the observation that simple algebraic combinations of leaf and canopy spectral transmittance and reflectance become wavelength independent and determine a small set of canopy structure specific variables. This set includes the canopy interceptance, the recollision and the escape probabilities. These variables specify an accurate relationship between the spectral response of a vegetation canopy to the incident solar radiation at the leaf and the canopy scale and allow for a simple and accurate parameterization for the partitioning of the incoming radiation into canopy transmission, reflection and absorption at any wavelength in the solar spectrum. This paper presents a solid theoretical basis for spectral invariant relationships reported in literature with an emphasis on their accuracies in describing the shortwave radiative properties of the three-dimensional vegetation canopies. The analysis of data on leaf and canopy spectral transmittance and reflectance collected during the international field campaign in Flakaliden, Sweden, June 25–July 4, 2002 supports the proposed theory. The results presented here are essential to both modeling and remote sensing communities because they allow the separation of the structural an