Constantino Muñoz-Porcar

Intense dust and extremely fresh biomass burning outbreak in Barcelona, Spain: characterization of their optical properties and estimation of their direct radiative forcing

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 ~ 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.

Current Research in Lidar Technology Used for the Remote Sensing of Atmospheric Aerosols

Lidars are active optical remote sensing instruments with unique capabilities for atmospheric sounding. A manifold of atmospheric variables can be profiled using different types of lidar: concentration of species, wind speed, temperature, etc. Among them, measurement of the properties of aerosol particles, whose influence in many atmospheric processes is important but is still poorly stated, stands as one of the main fields of application of current lidar systems. This paper presents a review on fundamentals, technology, methodologies and state-of-the art of the lidar systems used to obtain aerosol information. Retrieval of structural (aerosol layers profiling), optical (backscatter and extinction coefficients) and microphysical (size, shape and type) properties requires however different levels of instrumental complexity; this general outlook is structured following a classification that attends these criteria. Thus, elastic systems (detection only of emitted frequencies), Raman systems (detection also of Raman frequency-shifted spectral lines), high spectral resolution lidars, systems with depolarization measurement capabilities and multi-wavelength instruments are described, and the fundamentals in which the retrieval of aerosol parameters is based is in each case detailed.

An Architecture Providing Depolarization Ratio Capability for a Multi-Wavelength Raman Lidar: Implementation and First Measurements

A new architecture for the measurement of depolarization produced by atmospheric aerosols with a Raman lidar is presented. The system uses two different telescopes: one for depolarization measurements and another for total-power measurements. The system architecture and principle of operation are described. The first experimental results are also presented, corresponding to a collection of atmospheric conditions over the city of Barcelona.

Contribution of EARLINET/ACTRIS to the summer 2013 Special Observing Period of the ChArMEx project: monitoring of a Saharan dust event over the western and central Mediterranean

ABSTRACT In the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr/) initiative, a field campaign took place in the western Mediterranean Basin between 10 June and 5 July 2013 within the ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) project. The scientific objectives of ADRIMED are the characterization of the most common ‘Mediterranean aerosols’ and their direct radiative forcing (column closure and regional scale). During 15–24 June a multi-intrusion dust event took place over the western and central Mediterranean Basin. Extra measurements were carried out by some EARLINET/ACTRIS (European Aerosol Research Lidar Network /Aerosols, Clouds, and Trace gases Research InfraStructure Network, http://www.actris.net/) lidar stations in Spain and Italy, in particular on 22 June in support to the flight over southern Italy of the Falcon 20 aircraft involved in the campaign. This article describes the physical and optical properties of dust observed at the different lidar stations in terms of dust plume centre of mass, optical depth, lidar ratio, and particle depolarization ratio. To link the differences found in the origin of dust plumes, the results are discussed on the basis of back-trajectories and air- and space-borne lidars. This work puts forward the collaboration between a European research infrastructure (ACTRIS) and an international project (ChArMEx) on topics of interest for both parties, and more generally for the atmospheric community.

Considerations about the determination of the depolarization calibration profile of a two-telescope lidar and its implications for volume depolarization ratio retrieval

We propose a new method for calculating the volume depolarization ratio of light backscattered by the atmosphere and a lidar system that employs an auxiliary telescope to detect the depolarized component. It takes into account the possible error in the positioning of the polarizer used in the auxiliary telescope. The theory of operation is presented and then applied to a few cases for which the actual position of the polarizer is estimated, and the improvement of the volume depolarization ratio in the molecular region is quantified. In comparison to the method used before, i.e., without correction, the agreement between the volume depolarization ratio with correction and the theoretical value in the molecular region is improved by a factor of 2–2.5.

Multi-wavelength aerosol LIDAR signal pre-processing: practical considerations

Elastic lidars provide range-resolved information about the aerosol content in the atmosphere. Nevertheless, a number of pre-processing techniques need to be used before performing the inversion of the detected signal: range-correction, time-averaging, photoncounting channel dead-time correction, overlap correction, Rayleigh-fitting and gluing of both channels.