Showing papers by "Adolfo Comerón published in 2013"

Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET

Abstract: . The eruption of the Icelandic volcano Eyjafjallajokull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajokull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org . A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org . During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL). After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajokull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on European scale reported here provides an unprecedented data set for evaluating satellite data and aerosol dispersion models for this kind of volcanic events.

Lidar with SiPM: Some capabilities and limitations in real environment

Abstract: The purpose of the work is to demonstrate real capabilities and to give examples of SiPMs application in lidar technology in both analog and photon counting modes. The experimental research within an operating lidar complex adapted to implement the analog mode and photon counting measurements with subsequent inversions of atmospheric extinction and backscattering coefficients was conducted. Theoretical evaluations of potential limitations of atmospheric lidar by use of real day-time background parameters and features of SiPM-photodetectors studied experimentally were carried out with comparison of the extent of sensitivity decreasing for different detectors used and estimations of their operation range reduction.

Wavelet Correlation Transform Method and Gradient Method to Determine Aerosol Layering from Lidar Returns: Some Comments

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 ar...

Remote Sensing of Clouds and the Atmosphere XVIII; and Optics in Atmospheric Propagation and Adaptive Systems XVI

Abstract: The demand for the rapid provision of EO products with well-defined characteristics in terms of temporal, spatial, image-specific and thematic criteria is increasing. Examples are products to support near real-time damage assessment after a natural disaster event, e.g. an earthquake. However, beyond the organizational and economic questions, there are technological and systemic barriers to enable a comfortable search, order, delivery or even combination of EO products. Most portals of space agencies and EO product providers require sophisticated satellite and product knowledge and, even worse, are all different and not interoperable. This paper gives an overview about the use cases and the architectural solutions that aim at an open and flexible EO mission infrastructure with application-oriented user interfaces and well-defined service interfaces based upon open standards. It presents corresponding international initiatives such as INSPIRE (Infrastructure for Spatial Information in the European Community), GMES (Global Monitoring for Environment and Security), GEOSS (Global Earth Observation System of Systems) and HMA (Heterogeneous Missions Accessibility) and their associated infrastructure approaches. The paper presents a corresponding analysis and design methodology and two examples how such architectures are already successfully used in early warning systems for geo-hazards and toolsets for environmentallyinduced health risks. Finally, the paper concludes with an outlook how these ideas relate to the vision of the Future Internet.

Estimation of a radiative transfer model in the longwave spectral range: sensitivity study and application to real cases

Abstract: The aerosol radiative effect in the longwave spectral range is often neglected in atmospheric aerosol forcing studies, hence very few researches are conducted in this field at local scale, and even less at regional scale. However, strong absorbing aerosols, like mineral dust, can have a small, but non-negligible heating effect in the longwave spectral range which can slightly counteract the aerosol cooling effect in the shortwave. The objective of this research is to perform a sensitivity study of an aerosol radiative transfer model as a function of dust particle properties. GAME model1, which can compute vertically resolved shortwave and longwave values of aerosol radiative forcing, is used. Before developing the sensitivity analysis, the aerosol radiative transfer model is validated by comparing its outputs with results published previously. Radiative forcing simulations in the longwave have shown an important sensitivity to the following parameters: aerosol size and refractive index, aerosol vertical distribution, humidity, surface temperature and albedo. A couple of strong mineral dust intrusion observed by means of lidar and sun-photometer are also presented in terms of shortwave and longwave radiative forcing.

Daytime aerosol extinction profiles from the combination of CALIOP profiles and AERONET products

Abstract: . The solar background illumination has a strong effect on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) measurements, leading to a decrease in the signal-to-noise ratio of the lidar signal. Because of this, CALIOP level 2 data algorithms might be limited in the retrieval of the properties of the aerosols in the atmosphere. In this work, we present a methodology that combines CALIOP level 1 data with AERONET (Aerosol RObotic NETwork) measurements to retrieve aerosol extinction profiles and lidar ratios in daytime conditions. In this way, we fulfill a two-fold objective: first, we obtain more accurate daytime aerosol information; second, we supplement column integrated measurements from AERONET sun photometers with information about the vertical distribution of aerosols. The methodology has been applied to Burjassot (39.30° N, 0.25° W) and Barcelona (41.39° N, 2.11° E) AERONET stations in the Mediterranean coast of Spain in the period from June 2006 to September 2011. We have found good agreement for the extinction profiles in several study cases of ground lidar measurements in Barcelona, coincident with CALIOP overpasses. Finally, the methodology has proved to be useful for the study of special episodes such as Saharan dust outbreaks.