392 research outputs found
Lidar and S-band radar profiling of the atmosphere : adaptive processing for boundary-layer monitoring, optical-parameter error estimation, and application cases
This Ph.D. thesis addresses remote sensing of the atmosphere by means of lidar and S-band clear-air weather radar, and related data signal processing. Active remote sensing by means of these instruments offers unprecedented capabilities of spatial and temporal resolutions for vertical atmospheric profiling and the retrieval of key optical and physical atmospheric products in an increasing environmental regulatory framework.
The first goal is this Ph.D. concerns the estimation of error bounds in the inversion of the profile of the atmospheric backscatter coefficient from elastic lidar signals (i.e., without wavelength shift in reception when interacting with atmospheric scatterers) by means of the two-component inversion algorithm (the so-called Klett-Fernald-Sasano¿s algorithm). This objective departs from previous works at the Remote Sensing Lab. (RSLab) of the Universitat Politècnica de Catalunya (UPC) and derives first-order error-propagated bounds (approximate) and total-increment bounds (exact). As distinctive feature in the state of the art, the error bounds merge into a single body both systematic (i.e., user-calibration inputs) and random error sources (finite signal-to-noise ratio, SNR) yielding an explicit mathematical form.
The second goal, central to this Ph.D., tackles retrieval of the Atmospheric Boundary Layer Height (ABLH) from elastic lidar and S-band Frequency-Modulated Continuous-Wave (FMCW) radar observations by using adaptive techniques based on the Extended Kalman Filter (EKF). The filter is based on morphological modelling of the Mixing-Layer-to-Free-Troposphere transition and continuous estimation of the noise covariance information. In the lidar-EKF realization the proposed technique is shown to outperform classic ABLH estimators such as those based on derivative techniques, thresholded decision, or the variance centroid method. The EKF formulation is applied to both ceilometer and UPC lidar records in high- and low-SNR scenes. The lidar-EKF approach is re-formulated and successfully extended to S-band radar scenes (Bragg¿s scattering) in presence of interferent noise sources (Rayleigh scattering from e.g., insects and birds). In this context, the FMCW feature enables the range-resolved capability. EKF-lidar and EKF-radar ABLH estimates are cross-examined from field campaign results.
Finally, the third goal deals with exploitation of the existing UPC lidar station: In a first introductory part, a modified algorithm for enhancing the dynamic range of elastic lidar channels by ¿gluing¿ analog and photon-counting data records is formulated. In a second part, two case examples (including application of the gluing algorithm) are presented to illustrate the capabilities of the UPC lidar in networked atmospheric observation of two recent volcano eruption events as part of the EARLINET (European Aerosol Research Lidar Network). The latter is part of GALION (Global Atmospheric Watch Atmospheric Lidar Observation Network)-GEOSS (Global Earth Observation System of Systems) framework.La tesis doctoral aborda la teledetecció atmosfèrica amb tècniques lidar i radar (banda S) i llur tractament del senyal. La teledetecció activa amb aquests instruments ofereix resolucions espacials i temporals sense precedents en la perfilometria vertical de l'atmosfera i recuperació de productes de dades òptics i físics atmosfèrics en un marc de creixent regulació mediambiental. El primer objectiu d'aquesta tesi concerneix l'estimació de cotes d'error en la inversió del perfil del coeficient de retrodispersió atmosfèrica a partir de senyals lidar de tipus elàstic (és a dir, sense desplaçament de la longitud d'ona en recepció al interactuar amb els dispersors atmosfèrics) mitjançant l'algorisme d'inversió de dues components de Klett-Fernald-Sasano. Aquest objectiu parteix de treballs previs en el Remote Sensing Lab. (RSLab) de la Universitat Politècnica de Catalunya (UPC) i permet obtenir cotes de primer ordre (aproximades) basades en propagació d'errors i cotes (exactes) basades en el increment total de l'error. Característica diferencial en front l'estat de l'art és l'assimilació d'errors sistemàtics (per exemple, entrades de cal.libració d'usuari) i aleatoris (relació senyal-soroll, SNR, finita) en forma matemàtica explícita. El segon objectiu, central de la tesis, aborda l'estimació de l'altura de la capa límit atmosfèrica (ABLH) a partir de senyal lidar elàstics i d'observacions radar en banda S (ona continua amb modulació en freqüència, FMCW) utilitzant tècniques adaptatives basades en filtrat estès de Kalman (EKF). El filtre es basa en modelat morfològic de la transició atmosfèrica entre la capa de mescla i la troposfera lliure i en l'estimació continua de la informació de covariança del soroll. En el prototipus lidar-EKF la tècnica proposada millora clarament les tècniques clàssiques d'estimació de la ABLH como són les basades en mètodes derivatius, decisió de llindar, o el mètode de la variança-centroide. La formulació EKF s'aplica tant a mesures procedents de ceilòmetres lidar como de la pròpia estació lidar UPC en escenes d'alta i baixa SNR. Addicionalment, l'enfoc lidar-EKF es reformula i s'estén amb èxit a escenes radar en banda S (dispersió Bragg) en presència de fonts de soroll interferent (dispersió Rayleigh de, per exemple, insectes i ocells). En aquest context, la característica FMCW permet la capacitat de resolució en distància. L'estimació de la ABLH amb els prototipus lidar-EKF i radar-EKF s'intercompara en campanyes de mesura. Finalment, el tercer objectiu atén a l'explotació de l'estació lidar UPC existent: En una primera part introductòria, es formula un algorisme modificat de "gluing" per a la millora del marge dinàmic de canals lidar elàstics mitjançant combinació (o "enganxat") de senyals lidar adquirits analògicament i amb foto-comptatge. En una segona part, es presenten dos exemples (incloent l'aplicació de l'algorisme de "gluing") que il.lustren les capacitats del lidar de la UPC en l'observació atmosfèrica de dos recents erupcions volcàniques des de la xarxa d'observació EARLINET (European Aerosol Research Lidar Network). Aquesta última és part de GALION (Global Atmospheric Watch Atmospheric Lidar Observation Network)-GEOSS (Global Earth Observation System of Systems)
Fabricación de estructuras para cristales fotónicos basados en silicio macroporoso
Este proyecto tiene como objetivo fabricar estructuras de níquel utilizando
silicio macroporoso como molde. La aplicación inicial de estas estructuras es el diseño
y fabricación de cristales fotónicos de níquel.
Para cumplir con el objetivo, se han caracterizado los procesos de fabricación
de silicio macroporoso 2D, silicio macroporoso modulado en profundidad y silicio
macroporoso 3D.
También se ha realizado la caracterización del crecimiento de níquel en medios
porosos, utilizando alúmina porosa. El proceso elegido para crecer níquel es el
electrodepósito.
En el tratamiento de las estructuras, se han utilizado tecnologías de fabricación
de microsistemas, tales como micromecanizado de superficie (evaporación, oxidación,
RIE), micromecanizado de volumen (ataque isotrópico, HF y anisotrópico, KOH).
Luego se ha rellenado las estructuras de silicio macroporoso con níquel y se ha
demostrado que es posible fabricar estructuras positivas y negativas de níquel en 2D,
moduladas en profundidad y 3D. Para las estructuras positivas se ha utilizado
polydimetilsiloxano (PDMS) como material sacrificial. También se han fabricado
estructuras negativas de polydimetilsiloxano.
Las estructuras de silicio macroporoso se han fabricado utilizando la tecnología
desarrollada en el Grupo de Micro y Nano Tecnologías del Departamento de Ingeniería
Electrónica de la UPC.
Para determinar su comportamiento como cristales fotónicos, se han realizado
medidas de reflexión en las estructuras fabricadas
Actividades españolas en el marco del proyecto CHARMEX desde 2009: un resumen
El proyecto ChArMEx (Chemistry-Aerosol Mediterranean Experiment) es
una iniciativa francesa cuyo objetivo es desarrollar y coordinar las acciones de investigación regionales para una evaluación científica de la situación actual y el futuro del medio ambiente atmosférico en la cuenca mediterránea. Los grupos españoles que participan en ChArMEx llevan a cabo investigaciones en varios campos. Entre ellos cabe señalar: un estudio in-situ de 3 años (2010-2012) en un
entorno regional de fondo en Mallorca; la instalación en Mallorca y Granada de dos nuevos colectores de deposición autónomos que colectan la deposición de polvo semanalmente; mediciones intensivas in situ y de teledetección en Barcelona en el verano 2012 durante la pre-campaña ChArMEx; y mediciones de teledetección intensivos en Barcelona y Granada en el verano de 2013 durante la campaña ChArMEx / ADRIMED. Este manuscrito da un resumen de todas las actividades conducidas por investigadores españoles hasta ahora en el marco de ChArMEx. Se presentan resultados preliminares del estudio in-situ de 3 años en Mallorca y parte de las campañas de verano de 2012 y 2013.Peer ReviewedPostprint (published version
Study on aerosol properties over Madrid (Spain) by multiple instrumentation during SPALI10 lidar campaign
Understanding the effect of aerosols upon radiative forcing requ
ires information about vertical profiles. Lidar techniques
represent a powerful tool for studies of the vertical structure
of the aerosol field. During the SPAin Lidar Intercomparison 20
10 (SPALI10) campaign, several multiwavelen
gth Raman lidar systems measured simultaneously in order to assess their performances. Multiwavelength lidars can pr
ovide relevant vertically-resolved information on aerosol optical
properties because the wavelength dependence of the backscatter and extinction coefficients allows for a more detailed discrimination of aerosol types. Several lidar stations belonging to SPALINET, the Spanish and Portuguese Lidar NETwork and also EARLINET, the European Aerosol Research Lidar NETwork, intercompared during a campaign that took place in Madrid from 18 October to 5 November 2010. The products provided by the lidar systems were compared with ancillary data.
At ground level, aerosol size distribution was continuously monitored. Additionally, the column-integrated characterization of the atmospheric aerosol was performed by means of a sun photometer. The extensive dataset obtained during SPALI10 field campaign enables to compare ground-level in-situ measurements with remote sensing techniques to determine vertically-resolved optical and microphysical properties of aerosols. Several relevant features shown in the comparison of the results obtained by the different instruments
are discussed in this work.Peer ReviewedPostprint (published version
Common Genetic Polymorphisms Influence Blood Biomarker Measurements in COPD
Implementing precision medicine for complex diseases such as chronic obstructive lung disease (COPD) will require extensive use of biomarkers and an in-depth understanding of how genetic, epigenetic, and environmental variations contribute to phenotypic diversity and disease progression. A meta-analysis from two large cohorts of current and former smokers with and without COPD [SPIROMICS (N = 750); COPDGene (N = 590)] was used to identify single nucleotide polymorphisms (SNPs) associated with measurement of 88 blood proteins (protein quantitative trait loci; pQTLs). PQTLs consistently replicated between the two cohorts. Features of pQTLs were compared to previously reported expression QTLs (eQTLs). Inference of causal relations of pQTL genotypes, biomarker measurements, and four clinical COPD phenotypes (airflow obstruction, emphysema, exacerbation history, and chronic bronchitis) were explored using conditional independence tests. We identified 527 highly significant (p 10% of measured variation in 13 protein biomarkers, with a single SNP (rs7041; p = 10−392) explaining 71%-75% of the measured variation in vitamin D binding protein (gene = GC). Some of these pQTLs [e.g., pQTLs for VDBP, sRAGE (gene = AGER), surfactant protein D (gene = SFTPD), and TNFRSF10C] have been previously associated with COPD phenotypes. Most pQTLs were local (cis), but distant (trans) pQTL SNPs in the ABO blood group locus were the top pQTL SNPs for five proteins. The inclusion of pQTL SNPs improved the clinical predictive value for the established association of sRAGE and emphysema, and the explanation of variance (R2) for emphysema improved from 0.3 to 0.4 when the pQTL SNP was included in the model along with clinical covariates. Causal modeling provided insight into specific pQTL-disease relationships for airflow obstruction and emphysema. In conclusion, given the frequency of highly significant local pQTLs, the large amount of variance potentially explained by pQTL, and the differences observed between pQTLs and eQTLs SNPs, we recommend that protein biomarker-disease association studies take into account the potential effect of common local SNPs and that pQTLs be integrated along with eQTLs to uncover disease mechanisms. Large-scale blood biomarker studies would also benefit from close attention to the ABO blood group
Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon
The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe
Many Labs 2: Investigating Variation in Replicability Across Samples and Settings
We conducted preregistered replications of 28 classic and contemporary published findings, with protocols that were peer reviewed in advance, to examine variation in effect magnitudes across samples and settings. Each protocol was administered to approximately half of 125 samples that comprised 15,305 participants from 36 countries and territories. Using the conventional criterion of statistical significance (p < .05), we found that 15 (54%) of the replications provided evidence of a statistically significant effect in the same direction as the original finding. With a strict significance criterion (p < .0001), 14 (50%) of the replications still provided such evidence, a reflection of the extremely highpowered design. Seven (25%) of the replications yielded effect sizes larger than the original ones, and 21 (75%) yielded effect sizes smaller than the original ones. The median comparable Cohen’s ds were 0.60 for the original findings and 0.15 for the replications. The effect sizes were small (< 0.20) in 16 of the replications (57%), and 9 effects (32%) were in the direction opposite the direction of the original effect. Across settings, the Q statistic indicated significant heterogeneity in 11 (39%) of the replication effects, and most of those were among the findings with the largest overall effect sizes; only 1 effect that was near zero in the aggregate showed significant heterogeneity according to this measure. Only 1 effect had a tau value greater than .20, an indication of moderate heterogeneity. Eight others had tau values near or slightly above .10, an indication of slight heterogeneity. Moderation tests indicated that very little heterogeneity was attributable to the order in which the tasks were performed or whether the tasks were administered in lab versus online. Exploratory comparisons revealed little heterogeneity between Western, educated, industrialized, rich, and democratic (WEIRD) cultures and less WEIRD cultures (i.e., cultures with relatively high and low WEIRDness scores, respectively). Cumulatively, variability in the observed effect sizes was attributable more to the effect being studied than to the sample or setting in which it was studied.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Instituto de Investigaciones Psicológicas (IIP
Fabricación de estructuras para cristales fotónicos basados en silicio macroporoso
Este proyecto tiene como objetivo fabricar estructuras de níquel utilizando
silicio macroporoso como molde. La aplicación inicial de estas estructuras es el diseño
y fabricación de cristales fotónicos de níquel.
Para cumplir con el objetivo, se han caracterizado los procesos de fabricación
de silicio macroporoso 2D, silicio macroporoso modulado en profundidad y silicio
macroporoso 3D.
También se ha realizado la caracterización del crecimiento de níquel en medios
porosos, utilizando alúmina porosa. El proceso elegido para crecer níquel es el
electrodepósito.
En el tratamiento de las estructuras, se han utilizado tecnologías de fabricación
de microsistemas, tales como micromecanizado de superficie (evaporación, oxidación,
RIE), micromecanizado de volumen (ataque isotrópico, HF y anisotrópico, KOH).
Luego se ha rellenado las estructuras de silicio macroporoso con níquel y se ha
demostrado que es posible fabricar estructuras positivas y negativas de níquel en 2D,
moduladas en profundidad y 3D. Para las estructuras positivas se ha utilizado
polydimetilsiloxano (PDMS) como material sacrificial. También se han fabricado
estructuras negativas de polydimetilsiloxano.
Las estructuras de silicio macroporoso se han fabricado utilizando la tecnología
desarrollada en el Grupo de Micro y Nano Tecnologías del Departamento de Ingeniería
Electrónica de la UPC.
Para determinar su comportamiento como cristales fotónicos, se han realizado
medidas de reflexión en las estructuras fabricadas
On the Mechanisms Driving Latent Heat Flux Variations in the Northwest Tropical Atlantic
International audienceAbstract The Northwest Tropical Atlantic (NWTA) is a region of complex surface ocean circulation. The most prominent feature is the North Brazil Current (NBC) and its retroflection at 8°N, which leads to the formation of numerous mesoscale eddies known as NBC rings. The NWTA also receives the outflow of the Amazon River, generating freshwater plumes that can extend up to 100,000 km 2 . We show that these two processes influence the spatial variability of the region's surface latent heat flux (LHF). On the one hand, the presence of surface freshwater modifies the vertical stratification of the ocean, the mixed layer heat budget, and thus the air‐sea heat exchanges. On the other hand, NBC rings create a highly heterogeneous mesoscale sea surface temperature (SST) field that directly influences the near‐surface atmospheric circulation. These effects are illustrated by observations from the ElUcidating the RolE of Cloud‐Circulation Coupling in ClimAte ‐ Ocean Atmosphere (EUREC 4 A‐OA) and Atlantic Tradewind Ocean‐Atmosphere Interaction Campaign (ATOMIC) experiments, satellite and reanalysis data. We decompose the LHF budget into several terms controlled by different atmospheric and oceanic processes to identify the mechanisms leading to LHF changes. We find LHF variations of up to 160 W m 2 , of which 100 W m 2 are associated with wind speed changes and 40 W m 2 with SST variations. Surface currents or heat release associated with stratification changes remain as second‐order contributions with LHF variations of less than 10 W m 2 each. This study highlights the importance of considering these three components to properly characterize LHF variability at different spatial scales, although it is limited by the scarcity of collocated observations
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