Search results for "SMAP"
showing 10 items of 37 documents
Estimation of Vegetation Structure Parameters From SMAP Radar Intensity Observations
2021
In this article, we present a multipolarimetric estimation approach for two model-based vegetation structure parameters (shape A and orientation distribution ψ of the main canopy elements). The approach is based on a reduced observation set of three incoherent (no phase information) polarimetric backscatter intensities (|S HH | 2 , |S HV | 2 , and |S VV | 2 ) combined with a two-parameter (A P and ψ) discrete scatterer model of vegetation. The objective is to understand whether this confined set of observations contains enough information to estimate the two vegetation structure parameters from the L-band radar signals. In order to disentangle soil and vegetation scattering influences on th…
Remote sensing of vegetation dynamics in agro-ecosystems using smap vegetation optical depth and optical vegetation indices
2017
The ESA's SMOS and the NASA's SMAP missions, launched in 2009 and 2015, respectively, are the first two missions having on-board L-band microwave sensors, which are very sensitive to the water content in soils and vegetation. Focusing on the vegetation signal at L-band, we have implemented an inversion approach for SMAP that allows deriving vegetation optical depth (VOD, a microwave parameter related to biomass and plant water content) alongside soil moisture, without reliance on ancillary optical information on vegetation. This work aims at using this new observational data to monitor the phenology of crops in major global agro-ecosystems and enhance present agricultural monitoring and pre…
Multi-Frequency Estimation of Canopy Penetration Depths from SMAP/AMSR2 Radiometer and IceSAT Lidar Data
2018
In this study, the $\tau-\omega$ model framework is used to derive extinction coefficient and canopy penetration depths from multi-frequency SMAP and AMSR2 retrievals of vegetation optical depth together with ICESat LiDAR vegetation heights. The vegetation extinction coefficient serves as an indicator of how strong absorption and scattering processes within the canopy attenuate microwaves at $\mathrm{L}$ and C-band. Through inversion of the extinction coefficient, the penetration depth into the canopy can be obtained, which is analyzed on local (Sahel, Illinois) and continental scale (Africa, parts of North America) as well as for a one year time series (04/2015-04/2016). First analyses of …
L-band vegetation optical depth seasonal metrics for crop yield assessment
2018
Attenuation of surface microwave emission due to the overlying vegetation is proportional to the density of the canopy and to its water content. The vegetation optical depth (VOD) parameter measures this attenuation. VOD could be a valuable source of information on agroecosystems, especially at lower frequencies for which greater portion of the vegetation canopy contributes to the observed brightness temperature. In the past, visible-infrared indices have been used to provide yield estimates based on measuring the photosynthetic activity from the surface canopy layer. These indices are affected by clouds and apply only in the presence of solar illumination. In this study we instead use the …
Estimation of vegetation loss coefficients and canopy penetration depths from SMAP radiometer and IceSAT lidar data
2017
In this study the framework of the τ — ω model is used to derive vegetation loss coefficients and canopy penetration depths from SMAP multi-temporal retrievals of vegetation optical depth, single scattering albedo and ICESat lidar vegetation heights. The vegetation loss coefficients serve as a global indicator of how strong absorption and scattering processes attenuate L-band microwave radiation. By inverting the vegetation loss coefficients, penetration depths into the canopy can be obtained, which are displayed for the global forest reservoirs. A simple penetration index is formed combining vegetation heights and penetration depth estimates. The distribution and level of this index reveal…
Evaluation of Clotting Factor Concentrates for Treatment of Thrombotic Thrombocytopenic Purpura.
2010
Abstract Abstract 3678 Introduction: Thrombotic thrombocytopenic purpura (TTP) is characterized by microthrombi, hemolytic anemia as well as thrombocytopenia. These symptoms are caused by a decreased activity of the protease ADAMTS13 which cleaves the von Willebrand Factor (VWF), due to mutation of the ADAMTS13-gene or autoantibodies. At the moment, the only available immediate therapy is plasmapheresis with Fresh Frozen Plasma (FFP) which may induce side effects. Therefore an alternative therapy might be the treatment with clotting factor concentrates. Methods: 40 plasma samples were tested, consisting of FFP and solvent/detergent treated plasma, four batches of each blood group; VWF/VIII …
L-Band vegetation optical depth for crop phenology monitoring and crop yield assessment
2018
Vegetation Optical Depth (VOD) at L-band is highly sensitive to the water content and above-ground biomass of vegetation. Hence, it has great potential for monitoring crop phenology and for providing crop yield forecasts. Recently, the Multi-Temporal Dual Channel Algorithm (MT -DCA) has been proposed to retrieve L-band VOD from Soil Moisture Active Passive (SMAP) measurements. In previous research, SMAP VOD has been compared to crop phenology and has been used to derive crop yield estimates. Here, we review and expand these initial research studies. In particular, we quantify the capability of VOD to detect different crop stages, and test different VOD metrics (i.e., maximum, range and inte…
Immunosuppressant therapy of thyroid eye disease.
1988
Thyroid eye disease is attributed to an autoimmune process where both cellular and humoral immunity play a role. In this report, after a short introduction dealing with immunopathogenesis of the disease, immunosuppressant therapy is discussed. Treatment with glucocorticoids (as the standard substance), nonsteroid immunosuppressants (azathioprine, cyclophosphamide, lately cyclosporin) and with the immunomodulatory substance ciamexone is reviewed. Retroorbital irradiation as a "local" immunosuppressive method and plasmapheresis are also discussed. While systemic glucocorticoids and to a lesser extent orbital radiotherapy are routinely administered for severe Graves' ophthalmopathy, nonsteroid…
An assessment of the differences between spatial resolution and grid size for the SMAP enhanced soil moisture product over homogeneous sites
2018
Abstract Satellite-based passive microwave remote sensing typically involves a scanning antenna that makes measurements at irregularly spaced locations. These locations can change on a day to day basis. Soil moisture products derived from satellite-based passive microwave remote sensing are usually resampled to a fixed Earth grid that facilitates their use in applications. In many cases the grid size is finer than the actual spatial resolution of the observation, and often this difference is not well understood by the user. Here, this issue was examined for the Soil Moisture Active Passive (SMAP) enhanced version of the passive-based soil moisture product, which has a grid size of 9-km and …
The Spectrum of Ocular Manifestations in Patients with Waldenström's Macroglobulinemia.
2021
Purpose: To investigate the ocular manifestations in 91 Waldenstrom's macroglobulinemia (WM) patients.Methods: Retrospective, cross-sectional, observational analysis.Results: Ocular impairments, detected in 19 patients, included flame-shaped hemorrhages, venous sausaging, papilledema, macular detachments, or central retinal vein occlusion in 16 patients; paraproteinemic keratopathy in 2; and a CANOMAD syndrome in 1. Best-corrected visual acuity was ≥0.5 logMAR units in 11 of 38 eyes. Intraocular pressure was increased in seven eyes. Genetic analysis in seven patients showed a mutation in the MYD88 gene in six patients and a nonsense mutation in the CXCR4 gene in five patients. Plasmapheresi…