Search results for "Spectroradiometer"

Detecting crop water status in mature olive orchards using vegetation spectral measurements.

2014

Full spectral measurements (350–2500 nm) at tree canopy and leaf levels and the corresponding leaf water potentials (LWP) were acquired in an olive grove of Sicily, at different hours of the day, during summer season 2011. The main objective of the work was to assess, on the basis of the experimental data-set, two different approaches to detect crop water status in terms of LWP. Specifically, using existing families of Vegetation Indices (VIs) and applying Partial Least Squares Regression (PLSR) were optimised and tested. The results indicated that a satisfactory estimation of LWP at tree canopy and leaf levels can be obtained using vegetation indices based on the near infrared–shortwave in…

Preliminary assessment of an integrated SMOS and MODIS application for global agricultural drought monitoring

2020

An application of the Soil Moisture Agricultural Drought Index (SMADI) for global agricultural drought monitoring is presented. The index integrates surface soil moisture from the Soil Moisture and Ocean Salinity (SMOS) mission with the Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) and Normalized Difference Vegetation Index (NDVI) and allows for global drought monitoring at medium spatial scales (0.05°). Biweekly maps of SMADI were obtained from year 2010 to 2015 over all agricultural areas on Earth. The SMADI time-series were compared with state-of-the-art drought indices over the Iberian Peninsula. Results show a good agreement between SMADI and the …

Analysis of spectral irradiance distribution for PV applications at high latitude

2020

The spectral distribution of global tilted irradiance measured in Grimstad, Norway, is analyzed in terms of the average photon energy ( $APE$ ) blue fraction ( $BF$ ) and useful fraction ( $UF$ ). The results based on eight months of recorded data show a general shift of the $APE,\ BF$ , and $UF$ values to higher values than reference AM1.5G spectrum, with 1.63 eV, 0.45, and 0.88 being the average indices, respectively. The statistical coefficient of variation ( $CV$ ) is used to determine the variation of indices. The $CV$ for $APE,\ BF$ , and $UF$ are calculated to be 20.1%, 26.1%, and 25.7%, respectively confirming the earlier findings on $APE$ being a more accurate index for the quantif…

Modeling Fire Danger in Galicia and Asturias (Spain) from MODIS images

2014

Forest fires are one of the most dangerous natural hazards, especially when they are recurrent. In areas such as Galicia (Spain), forest fires are frequent and devastating. The development of fire risk models becomes a very important prevention task for these regions. Vegetation and moisture indices can be used to monitor vegetation status; however, the different indices may perform differently depending on the vegetation species. Eight different spectral indices were selected to determine the most appropriate index in Galicia. This study was extended to the adjacent region of Asturias. Six years of MODIS (Moderate Resolution Imaging Spectroradiometer) images, together with ground fire data…

MODIS-Based Monthly LST Products over Amazonia under Different Cloud Mask Schemes

2016

One of the major problems in the monitoring of tropical rainforests using satellite imagery is their persistent cloud coverage. The use of daily observations derived from high temporal resolution sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), could potentially help to mitigate this issue, increasing the number of clear-sky observations. However, the cloud contamination effect should be removed from these results in order to provide a reliable description of these forests. In this study the available MODIS Land Surface Temperature (LST) products have been reprocessed over the Amazon Basin (10 N–20 S, 80 W–45 W) by introducing different cloud masking schemes. The mont…

Light transmission and ultraviolet protection of contact lenses under artificial illumination

2016

Purpose: To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)). Methods: The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer. Results: Five of the nine soft CLs analysed state that they incorporate UV filters…

2019

Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with othe…

First evaluation of the simultaneous SMOS and ELBARA-II observations in the Mediterranean region

2012

Abstract The SMOS (Soil Moisture and Ocean Salinity) mission was launched on November 2, 2009. Over the land surfaces, simultaneous retrievals of surface soil moisture (SM) and vegetation characteristics made from the multi-angular and dual polarization SMOS observations are now available from Level-2 (L2) products delivered by the European Space Agency (ESA). Therefore, first analyses evaluating the SMOS observations in terms of Brightness Temperatures (TB) and L2 products (SM and vegetation optical depth TAU) can be carried out over several calibration/validation (cal/val) sites selected by ESA over all continents. This study is based on SMOS observations and in situ measurements carried …

Fire danger estimation from MODIS Enhanced Vegetation Index data: application to Galicia region (north-west Spain)

2011

Galicia, in north-west Spain, is a region especially affected by devastating forest fires. The development of a fire danger prediction model adapted to this particular region is required. In this paper, we focus on changes in the condition of vegetation as an indicator of fire danger. The potential of the Enhanced Vegetation Index (EVI) together with period-of-year to monitor vegetation changes in Galicia is shown. The Moderate Resolution Imaging Spectroradiometer (MODIS), onboard the Terra satellite, was chosen for this study. A 6-year dataset of EVI images, from the product MOD13Q1 (16-day composites), together with fire data in a 10 × 10-km grid basis, were used. Logistic regression was…

Performance of a FieldSpec spectroradiometer for aerosol optical depth retrieval: method and preliminary results

2009

The performance of a FieldSpec spectroradiometer for retrieving aerosol optical depth (AOD) has been assessed after modifying its basic configuration in order to measure direct solar irradiance at ground level. The FieldSpec measurements were obtained during four summertime days in the years 2004 and 2005, over a Spanish agricultural site in Barrax, Albacete (30 degrees 3(') N, 2 degrees 6(') W, 700 m a.s.l.), in the framework of two European Space Agency mission remote sensing field campaigns. From the whole FieldSpec spectral domain (350-2500 nm) the AOD was extracted for channels within atmospheric windows. The instrument was calibrated by means of the standard Langley plot method, perfo…