Francesc Rocadenbosch

Polytechnic University of Catalonia, Barcino, Catalonia, Spain

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Publications (86)87.48 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: An adaptive solution based on an extended Kalman filter (EKF) is proposed to estimate the atmospheric boundarylayer height (ABLH) from frequency-modulated continuous-wave S-band weather-radar returns. The EKF estimator departs from previous works, in which the transition interface between the mixing layer (ML) and the free troposphere (FT) is modeled by means of an erf-like parametric function. In contrast to lidar remote sensing, where aerosols give strong backscatter returns over the whole ML, clear-air radar reflectivity returns (Bragg scattering from refractive turbulence) shows strongest returns from the ML-FT interface. In addition, they are corrupted by “insect” noise (impulsive noise associated with Rayleigh scattering from insects and birds), all of which requires a specific treatment of the problem and the measurement noise for the clear-air radar case. The proposed radar-ABLH estimation method uses: 1) a first preprocessing of the reflectivity returns based on median filtering and threshold-limited decision to obtain “clean” reflectivity signal; 2) a modified EKF with adaptive range intervals as time tracking estimator; and 3) ad hoc modeling of the observation noise covariance. The method has successfully been implemented in clear-air, single-layer, and convective boundary-layer conditions. ABLH estimates from the proposed radar-EKF method have been cross examined with those from a collocated lidar ceilometer yielding a correlation coefficient as high as ρ = 0.93 (mean signal-to-noise ratio, SNR = 18 (linear units), at the ABLH) and in relation to the classic THM.
    IEEE Transactions on Geoscience and Remote Sensing 06/2015; 53(6):3338-3349. DOI:10.1109/TGRS.2014.2374233 · 2.93 Impact Factor
  • Sergio Tomás, Francesc Rocadenbosch
    Journal of Geophysical Research Atmospheres 04/2015; DOI:10.1002/2014JD022858 · 3.44 Impact Factor
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    ABSTRACT: Spray drift is one of the main sources of pesticide contamination. For this reason, an accurate understanding of this phenomenon is necessary in order to limit its effects. Nowadays, spray drift is usually studied by using in situ collectors which only allow time-integrated sampling of specific points of the pesticide clouds. Previous research has demonstrated that the light detection and ranging (lidar) technique can be an alternative for spray drift monitoring. This technique enables remote measurement of pesticide clouds with high temporal and distance resolution. Despite these advantages, the fact that no lidar instrument suitable for such an application is presently available has appreciably limited its practical use. This work presents the first eye-safe lidar system specifically designed for the monitoring of pesticide clouds. Parameter design of this system is carried out via signal-to-noise ratio simulations. The instrument is based on a 3-mJ pulse-energy erbium-doped glass laser, an 80-mm diameter telescope, an APD optoelectronic receiver and optomechanically adjustable components. In first test measurements, the lidar system has been able to measure a topographic target located over 2 km away. The instrument has also been used in spray drift studies, demonstrating its capability to monitor the temporal and distance evolution of several pesticide clouds emitted by air-assisted sprayers at distances between 50 and 100 m.
    Sensors 02/2015; 15(2):3650-3670. DOI:10.3390/s150203650 · 2.05 Impact Factor
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    ABSTRACT: This contribution evaluates an approach using an extended Kalman filter (EKF) to estimate the planetary boundary layer height (PBLH) from lidar measurements obtained in the framework of the European Aerosol Research LIdar NETwork (EARLINET) at 12 UTC ± 30-min for a 7-year period (2007-2013) under different synoptic flows over the complex geographical area of Barcelona, Spain. PBLH diagnosed with the EKF technique are compared with classic lidar methods and radiosounding estimates. Seven unique synoptic flows are identified using cluster analysis of 5756 HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) three-day backtrajectories for a 16-year period (1998-2013) arriving at 0.5 km, 1.5 km, and 3 km, to represent the lower PBL, upper PBL, and low free troposphere, respectively. Regional recirculations are dominant with 54% of the annual total at 0.5 km and 57% of the total lidar days at 1.5 km, with a clear preference for summertime (0.5 km: 36% and 1.5 km: 29%). PBLH retrievals using the EKF method range from 0.79 - 1.6 km asl. The highest PBLHs are observed in southwest flows (15.2% of total) and regional recirculations from the east (34.8% of total), mainly caused by the stagnant synoptic pattern in summertime over the Iberian Peninsula. The lowest PBLHs are associated with north (19.6% of total) and northeast (4.3% of total) synoptic flows, when fresh air masses tend to lower PBLH. The adaptive nature of the EKF technique allows retrieval of reliable PBLH without the need for long time averaging or range smoothing, as typical with classic methods.
    Proceedings of SPIE - The International Society for Optical Engineering 10/2014; 9242(92420F). DOI:10.1117/12.2072049 · 0.20 Impact Factor
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    ABSTRACT: An improvement of the estimation of mineral dust longwave, direct radiative forcing is presented. It is based on recent developments that combine sun-photometer and multi-wavelength lidar data to retrieve range-resolved coarse- and fine-mode extinction coefficients. The forcings are calculated separately for each mode and their sum is compared to the classical approach in which only the total extinction is considered. The results of four cases of mineral dust intrusion in Barcelona, Spain, show that when the coarse mode predominates the longwave forcings calculated with the classical approach are underestimated up to 20 % near the surface. In all cases the strong coarse mode predominance near the surface has also an effect on the forcing in the upper layers.
    10/2014; 41(19). DOI:10.1002/2014GL060946
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    2nd ITaRS Summer School on "Clouds and Precipitation: Observation and Processes", Jülich, Germany; 09/2014
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    Robert F Banks, José M Baldasano, Francesc Rocadenbosch
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    ABSTRACT: The planetary boundary-layer (PBL) is defined as the height of the inversion level separating the free troposphere from the boundary-layer [Stull, 1988]. PBL height is an important parameter in applications ranging from climate studies to air quality modeling. Lidars with high spatial (< 30 m) and temporal (< 5 min) resolutions can be employed to monitor the PBL height using aerosols as tracers. This study evaluates an approach using an Extended Kalman Filter (EKF) to estimate the PBL height in different atmospheric situations over Barcelona, Spain. PBL heights estimated by the EKF method are compared with classic methods (gradient, Haar wavelet, radiosondes, etc.) under 7 atmospheric conditions. Atmospheric situations are selected using a cluster analysis of 2-day backtrajectories from the NOAA HYSPLIT model.
    ITaRS Midterm Review Meeting, Potsdam, Germany; 02/2014
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    ABSTRACT: Pesticide spray drift entails a series of risks and costs in terms of human, animal and environmental well-being. A proper understanding of this phenomenon is essential to minimise these risks. However, most conventional methods used in drift measurement are based on point collectors which are unable to obtain information concerning the temporal or spatial evolution of the pesticide cloud. Such methods are also costly, labour-intensive, and require a considerable amount of time. The aim of this paper is to propose a method to measure the spray drift based on lidar (LIght Detection And Ranging) and to prove that it can be an alternative to passive collectors. An analytical model is proposed to relate the measurements obtained through passive collectors and those obtained with lidar systems considering several spray application and meteorological parameters. The model was tested through an experimental campaign involving multiple ground spray tests. A lidar system and two types of passive collectors (nylon strings and water-sensitive paper) were used simultaneously to measure the drift. The results showed for each test a high coefficient of determination (R2 ≈ 0.90) between the lidar signal and the tracer mass captured by the nylon strings. This coefficient decreased (R2 = 0.77) when all tests were considered together. Lidar measurements were also used to study the evolution of the pesticide cloud with high range (1.5 m) and temporal resolution (1 s) and to estimate its velocity. Furthermore, a very satisfactory adjustment (R2 = 0.89) was observed between the tracer mass collected by the nylon lines and the coverage on water-sensitive paper sheets. These results are in accordance with the proposed analytical model and allow the conclusion that the application and meteorological parameters can be considered spatially invariant for a given test but are not invariant for different tests.
    Atmospheric Environment 01/2014; 82:83–93. DOI:10.1016/j.atmosenv.2013.09.028 · 3.06 Impact Factor
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    ABSTRACT: The depth of the planetary boundary-layer (PBL) is defined as the height of the inversion level separating the free troposphere (FT) from the boundary-layer (Stull, 1988). Reliable representation of PBL height is important in applications ranging from climate studies to air quality modeling. Convective turbulent mixing processes are dominant in the mixing layer of the PBL and have a major influence on the growth and transport of atmospheric pollutants. In recent years, lidar (laser radar) has proven to be a useful operational tool for nearly continuous monitoring of the lowest levels of the atmosphere with high spatial (~ 3.75 m) and temporal (< 5 min) resolutions. Four Raman-elastic multi-wavelength lidar stations from EARLINET (European Aerosol Research Lidar Network) conducted a 72-hr campaign of continuous observations over Spain (Barcelona, Granada, Madrid) and Portugal (Evora) in early July 2012. This study systematically exploits 1-min averaged, range-squared-corrected lidar signals (RSCS) from the 532 nm analog reception channel of the instruments. Several methods that have been applied in previous literature to derive PBL height from vertical aerosol backscatter profiles are compared. Most widely used are derivative techniques such as the gradient method (GM), inflection point method (IPM), and logarithm gradient method (LGM) and covariance techniques such as the wavelet covariance transform (WCT) method using a Haar wavelet. The methods function by detecting steep gradients in the aerosol backscatter profile, a proxy for the transition zone between the PBL and FT. It is found that all the methods provide comparable results. However, it is determined that WCT is an optimal method as it is more computationally efficient than the derivative techniques. In summer, PBL heights over the Iberian Peninsula are typically between 1-3 km. In addition, spatial patterns and diurnal variation of the PBL height and an analysis of the meteorological situation over the study area are also conducted. Backward trajectories from the NOAA HYSPLIT model indicate aerosols arrived from tropical maritime origins over the eastern Atlantic Ocean in the previous 24-48 hours of the campaign. Overall, it is shown that lidar can be an effective means of obtaining accurate PBL heights on a nearly continuous basis.
    2013 Fall Meeting of the American Geophysical Union, San Francisco, CA, USA; 12/2013
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    ABSTRACT: A solution based on a Kalman filter to trace the evolution of the atmospheric boundary layer (ABL) sensed by a ground-based elastic-backscatter tropospheric lidar is presented. An erf-like profile is used to model the mixing-layer top and the entrainment-zone thickness. The extended Kalman filter (EKF) enables to retrieve and track the ABL parameters based on simplified statistics of the ABL dynamics and of the observation noise present in the lidar signal. This adaptive feature permits to analyze atmospheric scenes with low signal-to-noise ratios (SNRs) without the need to resort to long-time averages or range-smoothing techniques, as well as to pave the way for future automated detection solutions. First, EKF results based on oversimplified synthetic and experimental lidar profiles are presented and compared with classic ABL estimation quantifiers for a case study with different SNR scenarios.
    IEEE Transactions on Geoscience and Remote Sensing 09/2013; PP(99):1-12. DOI:10.1109/TGRS.2013.2284110 · 2.93 Impact Factor
  • 12th Workshop on Spray application techniques in fruit growin (Suprofrui 2013); 06/2013
  • Adolfo Comerón, Michaël Sicard, Francesc Rocadenbosch
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    ABSTRACT: Identification of aerosol layers on lidar measurements is of interest to determine ranges where aerosol properties are likely to be homogeneous and to infer transport phenomena and atmosphere dynamics. For instance, the range-corrected backscattered signal from aerosol measured with lidars has long been used as a proxy to determine the depth of the planetary boundary layer. The method relies on the assumption that in a well-mixed atmosphere, a rather homogenous aerosol distribution will exist within the boundary layer; hence, a sudden drop in the lidar range-corrected signal profile will mark the end of the layer. The most usual methods to detect that drop are the gradient method, which detects a negative maximum in the derivative with respect to range of the lidar range-corrected signal, or of its logarithm, and the wavelet correlation transform method, which detects a maximum in the correlation function of the lidar range-corrected signal and a wavelet, usually the Haar wavelet. These methods are not restricted to determining the boundary layer height but can also be used to locate the edges of lofted aerosol layers. Using fundamentals of linear system theory, this study shows the deep link existing between the gradient method and the wavelet correlation transform method using the Haar wavelet, the latter being equivalent to the gradient method applied to a range-corrected signal profile smoothed by a low-pass spatial filtering, which seems not to have been explicitly noted in the literature so far. Consequences are readily drawn for the wavelet correlation transform method using other wavelets.
    Journal of Atmospheric and Oceanic Technology 06/2013; 30(6):1189-1193. DOI:10.1175/JTECH-D-12-00233.1 · 1.82 Impact Factor
  • SPIENewsroom 03/2013; DOI:10.1117/2.1201303.004693
  • Dhiraj Kumar, Francesc Rocadenbosch
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    ABSTRACT: The problem of overlap factor (OVF) computation and its near-range sensitivity for medium-size aperture (f/10, f/11) bi-axial tropospheric lidar systems using ray-tracing simulation software is presented. The method revisits both detector and fiber optics coupling alternatives at the telescope focal-plane along with the insertion of a field lens. A sensitivity analysis is carried out as a function of laser divergence, field lens, and detector/fiber positions, detector size, and the fiber's core diameter and numerical aperture. The ray-tracing approach presented here is straightforward and a comparatively much simpler solution than analytical-based methods. Parametric simulations are carried out to show that both approaches are coincident. Insertion of a field lens proves to be an elegant and low sensitivity solution for OVF enhancement, particularly, in the near-range of the lidar.
    Journal of Applied Remote Sensing 01/2013; DOI:10.1117/1.JRS.7.073591 · 0.89 Impact Factor
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    ABSTRACT: Total backscatter-coefficient inversion error bounds for the two-component lidar inversion algorithm (so-called Fernald's or Klett-Fernald-Sasano's method) are derived in analytical form in response to the following three error sources: 1) the measurement noise; 2) the user uncertainty in the backscatter-coefficient calibration; and 3) the aerosol extinction-to-backscatter ratio. The following two different types of error bounds are presented: 1) approximate error bounds using first-order error propagation and 2) exact error bounds using a total-increment method. Both error bounds are formulated in explicit analytical form, which is of advantage for practical physical sensitivity analysis and computational implementation. A Monte Carlo approach is used to validate the error bounds at 355-, 532-, and 1064-nm wavelengths.
    IEEE Transactions on Geoscience and Remote Sensing 11/2012; 50(11):4791-4803. DOI:10.1109/TGRS.2012.2194501 · 2.93 Impact Factor
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    ABSTRACT: An extremely fresh smoke plume (<5 h) was transported over Barcelona on 23 July 2009, just 5 h after an intense Saharan dust event finalized. Both events were observed by sun-photometer, lidar and satellite systems. Results indicate surprisingly large absorption of mixed dust particles (SSA similar to 0.83 +/- 0.04) with lower SSA than that observed for smoke (0.86 +/- 0.04) particles at 440 nm. Our investigation shows that dust particles may have mixed during their transport with anthropogenic and smoke particles. Dust and smoke layers are observed between 1-6 and 1-4 km, with associated lidar ratios at 532 nm of 51 and 36 sr, respectively. Due to low SSAs and moderate surface albedos, shortwave (SW) radiative forcing calculations reveal that a large part of the solar energy losses at the surface is gained by the atmosphere for each aerosol. Here, dust particles produced a positive instantaneous forcing at TOA (+8 W m(-2) at 12 UT), while the smoke produced a negative forcing of -13 W m(-2) at 17 UT. The associated SW heating rate is calculated to be around 2-3 K day(-1) for both dust and smoke aerosols.
    Environmental Research Letters 09/2012; 7(3). DOI:10.1088/1748-9326/7/3/034016 · 4.09 Impact Factor
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    ABSTRACT: This paper presents parameter design methodology and related optomechanical engineering of a 905-nm diode-laser biaxial, eye-safe lidar ceilometer prototype for cloud-height monitoring. Starting with a brief review of the state-of-the-art ceilometer technology, acceptable parameter ranges are identified for the key system parts. Parameter tuning is achieved by imposing goal criteria on the simulated signal-to-noise ratio and laser-telescope overlap factor. The system is based on a low-cost pulsed semiconductor laser, low-cost Fresnel-lens telescope, a low-noise-equivalent power avalanche-photodiode optoelectronic receiver, and collimating/focusing adjustable parts. Finally, preliminary test measurements are presented.
    Journal of Applied Remote Sensing 05/2012; 6:063546. DOI:10.1117/1.JRS.6.063546 · 0.89 Impact Factor
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    ABSTRACT: Although routinely monitored by ground based air quality networks, the particulate matter distribution could be eventually better described with remote sensing techniques. However, valid relationships between ground level and columnar ground based quantities should be known beforehand. In this study we have performed a comparison between particulate matter measurements at ground level at different cut sizes (10, 2.5 and 1.0 mm), and the aerosol optical depth obtained by means of a ground based sunphotometer during a multiinstrumental field campaign held in El Arenosillo (Huelva, Spain) from 28 June to 4 July 2006. All the PM fractions were very well correlated with AOD with correlation coefficients that ranged from 0.71 to 0.81 for PM10, PM2.5 and PM1. Furthermore, the influence of the mixing layer height in the correlations was explored. The improvement in the correlation when the vertical distribution is taken into account was significant for days with a homogeneous mixing layer. Moreover, the chemical analysis of the individual size fractions allowed us to study the origin of the particulate matter. Secondary components were the most abundant and also well correlated in the three size fractions; but for PM10 fraction, chemical species related to marine origin were best correlated. Finally, we obtained a relationship between MODIS L3 AOD from collection 5.1 and the three PM cut sizes. In spite of being a relatively clean environment, all the techniques were able to capture similar day to day variations during this field campaign.
    Journal of Geophysical Research Atmospheres 02/2012; 117(D04201). DOI:10.1029/2011JD016356 · 3.44 Impact Factor
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    ABSTRACT: The need of a multi-spectral lidar has widely been experienced in last few years with a view to invert the optical and microphysical properties of aerosols and their impact on the climate change. As a part of the EARLINET-GALION objectives, a joint effort has already been made by the European Aerosol Research Lidar Network (EARLINET). The EARLINET advanced standard of 3+2-channel configuration for lidar instruments (3+2 standing for 3 elastic channels and 2 respective Raman channels) enables retrieval of aerosol microphysical properties. An overview of the new RSLAB 3+2+1 multispectral lidar system, therefore, is presented in terms of power budget estimation for all the reception channels and overall system performance, that is, signal-to-noise ratio (SNR) and maximum sounding range achieved.
    Geoscience and Remote Sensing Symposium (IGARSS), 2012 IEEE International; 01/2012

Publication Stats

723 Citations
87.48 Total Impact Points

Institutions

  • 1998–2015
    • Polytechnic University of Catalonia
      • Department of Signal Theory and Communications (TSC)
      Barcino, Catalonia, Spain
  • 2012
    • University of Barcelona
      Barcino, Catalonia, Spain
  • 2011
    • IEEC Institute of Space Studies of Catalonia
      Barcino, Catalonia, Spain
  • 2006
    • Institut Marqués, Spain, Barcelona
      Barcino, Catalonia, Spain