107 research outputs found
Using hyperspectral remote sensing to map grape quality in 'Tempranillo' vineyards affected by iron deficiency chlorosis
The objectives of this work wereto investigate the relationships between chlorophyll a+b concentration in leaves (Cab) and grape composition parameters in vineyards affected by iron chlorosis, andstudy whether the assessment of Cab from hyperspectral remote sensing imagery could be useful to map different potential quality zones in these vineyards.A field trial was conducted in a vineyard with the chlorosis susceptible cultivar. 'Tempranillo', over '110 Richter', located in Northern Spain. Three experimental treatments were applied: 0, 2, and 4 foliar sprayings with a ligninsulphonate derived product (10 % water soluble Fe) in a randomized design with 3 replications. The yield and grape composition parameters at harvest were measured for each base-plot (10x10 m in size), and related with chlorophyll concentration in leaves. On the other hand, a total of 24 'Tempranillo' commercial vineyards were identified for field and airborne data collection with CASI hyperspectral sensor, comprising 103 study areas of 10x10 m in size. A total of 1467 leaves were collected for determining pigment concentration and optical properties. Several narrow-band vegetation indices were calculated from leaf reflectance spectra. Results of trial showed that the lack of pigmentation in leaves was a major factor limiting grape ripening. Significant linear regressions between Cab and total soluble solids concentration and colour density of the must were detected. Estimation of Cab using the image-calculated TCARI/OSAVI through the PROSPECT-rowMCRM model simulation for all study zones, including the specific ligninsulphonate experiment, demonstrated the potential of hyperspectral imagery for mapping Cab in vineyards for chlorosis detection using remote sensing methods. Given the described relationship between Cab and quality parameters in vineyards affected by iron chlorosis, high-spatial resolution imagery with narrow bands might enable the segmentation in areas of potential quality in the framework of precision viticulture.
A 10-year characterization of the Saharan Air Layer lidar ratio in the subtropical North Atlantic
Particle extinction-to-backscatter
ratio (lidar ratio) is a key parameter for a correct interpretation of
elastic lidar measurements. Of particular importance is the determination of
the lidar ratio of the Saharan Air Layer mineral dust transported into the
free troposphere over the North Atlantic region. The location of the two sun
photometer stations managed by the Izaña Atmospheric Research Centre
(IARC) on the island of Tenerife and a decade of available micropulse lidar
(MPL) data allow us to determine the lidar ratio under almost pure-dust
conditions. This result can be considered representative of the Saharan dust
transported westward over the North Atlantic in the subtropical belt.
Three different methods have been used to calculate the lidar ratio in this
work: (1) using the inversion of sky radiance measurements from a sun–sky
photometer installed at the Izaña Observatory (2373 m a.s.l.) under
free-troposphere conditions; (2)Â the one-layer method, a joint determination using
a micropulse lidar sited at the Santa Cruz de Tenerife sea-level station and
photometric information considering one layer of aerosol characterized by a
single lidar ratio; and (3)Â the two-layer method, a joint determination using the
micropulse lidar and photometric information considering two layers of
aerosol with two different lidar ratios. The one-layer method only uses data from
a co-located photometer at Santa Cruz de Tenerife, while the two-layer
conceptual approach incorporates photometric information at two heights from
the observatories of Izaña and Santa Cruz de Tenerife. The almost pure-dust
lidar ratio retrieval from the sun–sky photometer and from the two-layer
method give similar results, with lidar ratios at 523 nm of 49 ± 6 and
50 ± 11 sr. These values obtained from a decade of data
records are coincident with other studies in the literature reporting
campaigns in the subtropical North Atlantic region. This result shows that
the two-layer method is an improved conceptual approach compared to the
single-layer approach, which matches the real lower-troposphere
structure well. The two-layer method is able to retrieve reliable lidar ratios and
therefore aerosol extinction profiles despite the inherent limitations of
the elastic lidar technique.
We found a lack of correlation between lidar ratio and Ångström
exponent (α), which indicates that the dust lidar ratio can be
considered independent of dust size distribution in this region. This finding
suggests that dust is, under most atmospheric conditions, the predominant
aerosol in the North Atlantic free troposphere, which is in agreement with
previous studies conducted at the Izaña Observatory.</p
Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 2: Analysis of site aerosol influence
Several validation studies have shown a notable overestimation of the clear
sky ultraviolet (UV) irradiance at the Earth's surface derived from
satellite sensors such as the Total Ozone Mapping Spectrometer (TOMS) and
the Ozone Monitoring Instrument (OMI) with respect to ground-based UV data
at many locations. Most of this positive bias is attributed to boundary
layer aerosol absorption that is not accounted for in the TOMS/OMI
operational UV algorithm. Therefore, the main objective of this study is to
analyse the aerosol effect on the bias between OMI erythemal UV irradiance
(UVER) and spectral UV (305 nm, 310 nm and 324 nm) surface irradiances and
ground-based Brewer spectroradiometer measurements from October 2004 to
December 2008 at El Arenosillo station (37.1° N, 6.7° W,
20 m a.s.l.), with meteorological conditions representative of the South-West of
Spain.
<br><br>
The effects of other factors as clouds, ozone and the solar elevation over
this intercomparison were analysed in detail in a companion paper (Antón
et al., 2010). In that paper the aerosol effects were studied making only a
rough evaluation based on aerosol optical depth (AOD) information at 440 nm
wavelength (visible range) without applying any correction. We have used the
precise information given by single scattering albedo (SSA) from AERONET for
the determination of absorbing aerosols which has allowed the correction of
the OMI UV data.
<br><br>
An aerosol correction expression was applied to the OMI operational UV data
using two approaches to estimate the UV absorption aerosol optical depth,
AAOD. The first approach was based on an assumption of constant SSA value of
0.91. This approach reduces the OMI UVER bias against the reference Brewer
data from 13.4% to 8.4%. Second approach uses daily AERONET SSA values
reducing the bias only to 11.6%. Therefore we have obtained a 37% and
12% of improvement respectively. For the spectral irradiance at 324 nm,
the OMI bias is reduced from 10.5% to 6.98% for constant SSA and to
9.03% for variable SSA. Similar results were obtained for spectral
irradiances at 305 nm, and 310 nm.
<br><br>
Contrary to what was expected, the constant SSA approach has a greater bias
reduction than variable SSA, but this is a reasonable result according to
the discussion about the reliability of SSA values. Our results reflect the
level of accuracy that may be reached at the present time in this type of
comparison, which may be considered as satisfactory taking into account the
remaining dependence on other factors. Nevertheless, improvements must be
accomplished to determine reliable absorbing aerosol properties, which
appear as a limiting factor for improving OMI retrievals
A new method for nocturnal aerosol measurements with a lunar photometer prototype
This paper presents the preliminary results of nocturnal Aerosol Optical Depth (τa) and Angström Exponent (α) obtained from a new lunar photometer prototype, trade name Cimel CE-318U. Due to the variation of the moon's illumination inherent to the lunar cycle, the typical Langley-plot Method used in solar photometry to calibrate these instruments cannot be applied. In this paper, we propose three different methods to carry out the lunar-photometer calibration. In order to validate the results, we have selected three events which encompass seven nights and ten days under different atmospheric conditions, including several saharan dust intrusions episodes. Method#1 is introduced in this work as a modification of the usual Langley Method. This technique, called Lunar-Langley Method, requires the extraterrestrial irradiances from a lunar irradiance model, providing similar accuracies on τa to those of AERONET (±0.01-0.02). It makes comparable daytime and nighttime measurements. Method#2 consists of transferring the current calibration from a master used by sunphotometers. Its results are again within the limit of accuracy expected for the instrument. Method#3 uses an integrating sphere and the methodology proposed by Li et al. (2008) to determine sky calibration coefficients (Cj) and the instrument's solid angle field-of-view (Ω), respectively. We observe significant τa differences between Method#1 and #3 (up to 0.07), which might be attributed to the errors propagation in Method#3. The good results obtained from the comparison against a second CE-318U prototype, and against daytime data from a Precision Filter Radiometer (PFR), constitute a valuable assessment of CE-318U performance. Results of α and its spectral variation (δα) show good agreement between daytime and nighttime, being able to identify the aerosol properties associated with each event. © Author(s) 2013
Remote sensing detection of nutrient uptake in vineyards using narrow-band hyperspectral imagery
This manuscript delves further into the assessment of narrow-band vegetation indices derived from hyperspectral imagery acquired at 1 m spatial resolution with the Compact Airborne Spectrographic Imager (CASI). Narrow-band indices proposed in this study were assessed as indicators of biochemical and structural parameters in Vitis vinifera L., observing their relationships with foliar variables such as N, P, K, Ca, Fe, Mg and chlorophyll a+b concentration (Ca+b). Hyperspectral indices were assessed to study their capability for vegetation condition monitoring as a function of fertilization treatments applied (basically extracts of Ascophyllum nodosum seaweed and chelates), showing associations with field variables. Narrow-band vegetation indices displayed sensitivity to vineyard growth and condition as a function of seaweed fertilization and other supplementary mineral correctors, such as chelates. This work shows the interest of using new narrow-band hyperspectral remote sensing indices for vineyard monitoring due to their potential to indicate physiological condition.
The AERONET-Europe calibration facility: access within the ACTRIS project
Comunicación presentada en: 2012 European Aerosol Conference (EAC-2012), B-WG01S2P30, celebrada del 2 al 7 de septiembre de 2012 en Granada.This work has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement N. 262254. Financial support from the Spanish Ministry of Science (MICINN) under projects with ref. CGL2009-09740, CGL2011-23413, CGL2010-09480-E and CGL2011-13085-E as well as from Junta de
Castilla y León are gratefully acknowledged
Trends in socioeconomic inequalities in mortality in small areas of 33 Spanish cities
Background: In Spain, several ecological studies have analyzed trends in socioeconomic inequalities in mortality from all causes in urban areas over time. However, the results of these studies are quite heterogeneous finding, in general, that inequalities decreased, or remained stable. Therefore, the objectives of this study are: (1) to identify trends in geographical inequalities in all-cause mortality in the census tracts of 33 Spanish cities between the two periods 1996–1998 and 2005–2007; (2) to analyse trends in the relationship between these geographical inequalities and socioeconomic deprivation; and (3) to obtain an overall measure which summarises the relationship found in each one of the cities and to analyse its variation over time.Methods: Ecological study of trends with 2 cross-sectional cuts, corresponding to two periods of analysis: 1996–1998 and 2005–2007. Units of analysis were census tracts of the 33 Spanish cities. A deprivation index calculated for each census tracts in all cities was included as a covariate. A Bayesian hierarchical model was used to estimate smoothed Standardized Mortality Ratios (sSMR) by each census tract and period. The geographical distribution of these sSMR was represented using maps of septiles. In addition, two different Bayesian hierarchical models were used to measure the association between all-cause mortality and the deprivation index in each city and period, and by sex: (1) including the association as a fixed effect for each city; (2) including the association as random effects. In both models the data spatial structure can be controlled within each city. The association in each city was measured using relative risks (RR) and their 95 % credible intervals (95 % CI).Results: For most cities and in both sexes, mortality rates decline over time. For women, the mortality and deprivation patterns are similar in the first period, while in the second they are different for most cities. For men, RRs remain stable over time in 29 cities, in 3 diminish and in 1 increase. For women, in 30 cities, a non-significant change over time in RR is observed. However, in 4 cities RR diminishes. In overall terms, inequalities decrease (with a probability of 0.9) in both men (RR¿=¿1.13, 95 % CI¿=¿1.12–1.15 in the 1st period; RR¿=¿1.11, 95 % CI¿=¿1.09–1.13 in the 2nd period) and women (RR¿=¿1.07, 95 % CI¿=¿1.05–1.08 in the 1st period; RR¿=¿1.04, 95 % CI¿=¿1.02–1.06 in the 2nd period).Conclusions: In the future, it is important to conduct further trend studies, allowing to monitoring trends in socioeconomic inequalities in mortality and to identify (among other things) temporal factors that may influence these inequalities
Internal consistency of the Regional Brewer Calibration Centre for Europe triad during the period 2005–2016
Total ozone column measurements can be made using Brewer spectrophotometers,
which are calibrated periodically in intercomparison campaigns with respect
to a reference instrument. In 2003, the Regional Brewer Calibration Centre
for Europe (RBCC-E) was established at the Izaña Atmospheric Research
Center (Canary Islands, Spain), and since 2011 the RBCC-E has transferred its
calibration based on the Langley method using travelling standard(s) that are
wholly and independently calibrated at Izaña. This work is focused on
reporting the consistency of the measurements of the RBCC-E triad (Brewer
instruments #157, #183 and #185) made at the Izaña Atmospheric
Observatory during the period 2005–2016. In order to study the long-term
precision of the RBCC-E triad, it must be taken into account that each Brewer
takes a large number of measurements every day and, hence, it becomes
necessary to calculate a representative value of all of them. This value was
calculated from two different methods previously used to study the long-term
behaviour of the world reference triad (Toronto triad) and Arosa triad.
Applying their procedures to the data from the RBCC-E triad allows the
comparison of the three instruments. In daily averages, applying the
procedure used for the world reference triad, the RBCC-E triad presents a
relative standard deviation equal to σ  =  0.41 %, which is
calculated as the mean of the individual values for each Brewer
(σ157  =  0.362 %, σ183  =  0.453 % and
σ185  =  0.428 %). Alternatively, using the procedure used
to analyse the Arosa triad, the RBCC-E presents a relative standard deviation
of about σ  =  0.5 %. In monthly averages, the method used for
the data from the world reference triad gives a relative standard deviation
mean equal to σ  =  0.3 % (σ157  =  0.33 %,
σ183  =  0.34 % and σ185  =  0.23 %).
However, the procedure of the Arosa triad gives monthly values of
σ  =  0.5 %. In this work, two ozone data sets are analysed:
the first includes all the ozone measurements available, while the second
only includes the simultaneous measurements of all three instruments.
Furthermore, this paper also describes the Langley method used to determine
the extraterrestrial constant (ETC) for the RBCC-E triad, the necessary first
step toward accurate ozone calculation. Finally, the short-term or intraday
consistency is also studied to identify the effect of the solar zenith angle
on the precision of the RBCC-E triad.</p
Automatic quantification of cardiomyocyte dimensions and connexin 43 lateralization in fluorescence images
Cardiomyocytes’ geometry and connexin 43 (CX43) amount and distribution are structural features that play a pivotal role in electrical conduction. Their quantitative assessment is of high interest in the study of arrhythmias, but it is usually hampered by the lack of automatic tools. In this work, we propose a software algorithm (Myocyte Automatic Retrieval and Tissue Analyzer, MARTA) to automatically detect myocytes from fluorescent microscopy images of cardiac tissue, measure their morphological features and evaluate the expression of CX43 and its degree of lateralization. The proposed software is based on the generation of cell masks, contouring of individual cells, enclosing of cells in minimum area rectangles and splitting of these rectangles into end-to-end and middle compartments to estimate CX43 lateral-to-total ratio. Application to human ventricular tissue images shows that mean differences between automatic and manual methods in terms of cardiomyocyte length and width are below 4 µm. The percentage of lateral CX43 also agrees between automatic and manual evaluation, with the interquartile range approximately covering from 3% to 30% in both cases. MARTA is not limited by fiber orientation and has an optimized speed by using contour filtering, which makes it run hundreds of times faster than a trained expert. Developed for CX43 studies in the left ventricle, MARTA is a flexible tool applicable to morphometric and lateralization studies of other markers in any heart chamber or even skeletal muscle. This open-access software is available online
Trends in socioeconomic inequalities in mortality in small areas of 33 Spanish cities
Background: In Spain, several ecological studies have analyzed trends in socioeconomic inequalities in mortality from all causes in urban areas over time. However, the results of these studies are quite heterogeneous finding, in general, that inequalities decreased, or remained stable. Therefore, the objectives of this study are: (1) to identify trends in geographical inequalities in all-cause mortality in the census tracts of 33 Spanish cities between the two periods 1996–1998 and 2005–2007; (2) to analyse trends in the relationship between these geographical inequalities and socioeconomic deprivation; and (3) to obtain an overall measure which summarises the relationship found in each one of the cities and to analyse its variation over time. Methods: Ecological study of trends with 2 cross-sectional cuts, corresponding to two periods of analysis: 1996–1998 and 2005–2007. Units of analysis were census tracts of the 33 Spanish cities. A deprivation index calculated for each census tracts in all cities was included as a covariate. A Bayesian hierarchical model was used to estimate smoothed Standardized Mortality Ratios (sSMR) by each census tract and period. The geographical distribution of these sSMR was represented using maps of septiles. In addition, two different Bayesian hierarchical models were used to measure the association between all-cause mortality and the deprivation index in each city and period, and by sex: (1) including the association as a fixed effect for each city; (2) including the association as random effects. In both models the data spatial structure can be controlled within each city. The association in each city was measured using relative risks (RR) and their 95 % credible intervals (95 % CI). Results: For most cities and in both sexes, mortality rates decline over time. For women, the mortality and deprivation patterns are similar in the first period, while in the second they are different for most cities. For men, RRs remain stable over time in 29 cities, in 3 diminish and in 1 increase. For women, in 30 cities, a non-significant change over time in RR is observed. However, in 4 cities RR diminishes. In overall terms, inequalities decrease (with a probability of 0.9) in both men (RR = 1.13, 95 % CI = 1.12–1.15 in the 1st period; RR = 1.11, 95 % CI = 1.09–1.13 in the 2nd period) and women (RR = 1.07, 95 % CI = 1.05–1.08 in the 1st period; RR = 1.04, 95 % CI = 1.02–1.06 in the 2nd period). Conclusions: In the future, it is important to conduct further trend studies, allowing to monitoring trends in socioeconomic inequalities in mortality and to identify (among other things) temporal factors that may influence these inequalities.This article was partially funded by Plan Nacional de I + D + I 2008–2011 and Instituto de Salud Carlos III (ISCIII) –Subdirección General de Evaluación y Fomento de la Investigación- (Award numbers: PI081488, PI081978, PI080367, PI08/1017, PI080330, P08/0142, PI081785, PI080662, PI081713, PI081058, PI081340, PI080803, PI126/08), Fundación Canaria de Investigación Sanitaria FUNCIS 84/07 and by CIBER EpidemiologÃa y Salud Pública (CIBERESP)
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