Formación y transporte de dióxido de nitrógeno en la cuenca aérea de Madrid en situaciones episódicas de invierno

Esta investigación aborda el estudio experimental de la dinámica físico-química del dióxido de nitrógeno (NO2) en el penacho de contaminación atmosférica asociado con el área metropolitana de Madrid, restringiendo su caracterización al periodo invernal y centrándolo en las situaciones meteorológicas propicias paras la formación de episodios de contaminación. El trabajo se ha desarrollado siguiendo una metodología basada en la medida remota desde un Laboratorio Móvil de la columna troposférica de NO2 con el espectrómetro de correlación COSPEC V mejorado, y en la utilización de un avión instrumentado preparado para realizar medidas de concentración de NO2, monóxido de nitrógeno (NO) y ozono (O3), y cuya puesta en marcha ha constituido una experiencia pionera entre los grupos de investigación españoles. Los resultados del estudio muestran la existencia de un fenómeno de transporte del penacho de NO2 de Madrid a escala regional durante la situaciones episódicas de invierno. Cuando en estas condiciones se llegan a desarrollar en la cuenca flujos de carácter local, el transporte de contaminantes urbanos se produce siguiendo ciertos patrones circulatorios característicos de la región. Se ha obtenido por primera vez información experimental sobre la distribución vertical de NO, NO2 y O3 en el penacho urbano, lo que ha permitido estudiar la evolución química de estas tres especies en la globalidad de la cuenca aérea de Madrid. Ha quedado documentado el ciclo diario de formación del penacho de NO2 en esta región, en contraste con el comportamiento acumulativo de otros contaminantes. También se ha documentado y estudiado el rendimiento global de la formación de NO2 a partir de las especies precursoras emitidas a la atmósfera desde el área metropolitana

Formación y transporte de dióxido de nitrógeno en la cuenca aérea de Madrid en situaciones episódicas de invierno

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica I, leída el 20-12-2002Esta investigación aborda el estudio experimental de la dinámica físico-química del dióxido de nitrógeno (NO2) en el penacho de contaminación atmosférica asociado con el área metropolitana de Madrid, restringiendo su caracterización al periodo invernal y centrándolo en las situaciones meteorológicas propicias paras la formación de episodios de contaminación. El trabajo se ha desarrollado siguiendo una metodología basada en la medida remota desde un Laboratorio Móvil de la columna troposférica de NO2 con el espectrómetro de correlación COSPEC V mejorado, y en la utilización de un avión instrumentado preparado para realizar medidas de concentración de NO2, monóxido de nitrógeno (NO) y ozono (O3), y cuya puesta en marcha ha constituido una experiencia pionera entre los grupos de investigación españoles. Los resultados del estudio muestran la existencia de un fenómeno de transporte del penacho de NO2 de Madrid a escala regional durante la situaciones episódicas de invierno. Cuando en estas condiciones se llegan a desarrollar en la cuenca flujos de carácter local, el transporte de contaminantes urbanos se produce siguiendo ciertos patrones circulatorios característicos de la región. Se ha obtenido por primera vez información experimental sobre la distribución vertical de NO, NO2 y O3 en el penacho urbano, lo que ha permitido estudiar la evolución química de estas tres especies en la globalidad de la cuenca aérea de Madrid. Ha quedado documentado el ciclo diario de formación del penacho de NO2 en esta región, en contraste con el comportamiento acumulativo de otros contaminantes. También se ha documentado y estudiado el rendimiento global de la formación de NO2 a partir de las especies precursoras emitidas a la atmósfera desde el área metropolitana.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu

Vertical characterization of fine and coarse dust particles during an intense Saharan dust outbreak over the Iberian Peninsula in springtime 2021

An intense and long-lasting Saharan dust outbreak crossed the Iberian Peninsula (IP) from the southwest (SW) to the northeast (NE) from 25 March until 7 April 2021. This work aims to assess the optical and mass contribution of both fine and coarse dust particles along their transport. Five Iberian lidar stations were monitoring the transport and evolution of the Saharan dust particles, i.e. El Arenosillo/Huelva, Granada, Torrejón/Madrid and Barcelona in Spain, and Évora in Portugal. The particular meteorological conditions determined the aerosol scenario along the overall dust event, differing in the first part of the event (25–31 March), in which the strongest dust incidence occurred on 29–31 March at the south and central stations and 1 April at Barcelona, from the second one (1–7 April). The use of the two-step POLIPHON algorithm showed the relevance of using polarized lidar measurements for separating the aerosol properties of dust fine and coarse particles as an added value. Both the fine dust (Df) and coarse dust (Dc) components of the total particle backscatter coefficient (total dust, DD¿=¿Dc¿+¿Df) were separately derived. The dust plume was well-mixed with height and no significant differences were found in the vertical structure of both the Dc and Df particle backscatter coefficients. From the beginning of the dust outbreak until 1 April, the vertical Df¿¿DD mass ratio was nearly constant in time at each station and also in altitude with values of ~¿10¿%. Moreover, the mean dust optical depth at 532¿nm was decreasing along that dust pathway, reporting values from SW to NE stations of 0.34 at El Arenosillo/Huelva, 0.28 at Granada, 0.20 at Évora, 0.28 at Torrejón/Madrid, and 0.14 at Barcelona, although its Df¿¿DD ratio remained almost constant (28¿%–30¿%). A similar pattern was found for the total dust mass loading and its Df¿¿DD ratio, i.e. mostly decreasing mean mass values were reported, being constant in its Df¿¿DD ratio (~¿10¿%) along the SW–NE dust pathway. In addition, the episode-mean centre-of-mass height increased with latitude overall, showing a high variability, being greater than 0.5¿km at the southern sites (El Arenosillo/Huelva, Granada, Évora) and ~¿1.0¿km at Torrejón/Madrid and Barcelona. However, despite the relatively high intensity of the dust intrusion, the expected ageing of the dust particles was hardly observed, by taking into account the minor changes found in the contribution and properties of the coarse and fine dust particles. This is on the basis that the IP is relatively close to the Saharan dust sources and then, under certain dust transport conditions, any potential ageing processes in the dust particles remained unappreciated. The following must be highlighted: the different relative contribution of the fine dust particles to the total dust found for their optical properties (~¿30¿%) associated with the radiative effect of dust, with respect to that for the mass features (~¿10¿%) linked to air quality issues, along the overall dust event by crossing the IP.This research has been supported by the Spanish Ministry of Science and Innovation (grant no. PID2019-104205GB-C21/AEI/10.13039/501100011033).Peer ReviewedPostprint (published version

EARLINET instrument intercomparison campaigns: overview on strategy and results

This paper introduces the recent European Aerosol Research Lidar Network (EARLINET) quality-assurance efforts at instrument level. Within two dedicated campaigns and five single-site intercomparison activities, 21 EARLINET systems from 18 EARLINET stations were intercompared between 2009 and 2013. A comprehensive strategy for campaign setup and data evaluation has been established. Eleven systems from nine EARLINET stations participated in the EARLINET Lidar Intercomparison 2009 (EARLI09). In this campaign, three reference systems were qualified which served as traveling standards thereafter. EARLINET systems from nine other stations have been compared against these reference systems since 2009. We present and discuss comparisons at signal and at product level from all campaigns for more than 100 individual measurement channels at the wavelengths of 355, 387, 532, and 607¿nm. It is shown that in most cases, a very good agreement of the compared systems with the respective reference is obtained. Mean signal deviations in predefined height ranges are typically below ±2¿%. Particle backscatter and extinction coefficients agree within ±2¿¿×¿¿10-4¿km-1¿sr-1 and ±¿0.01¿km-1, respectively, in most cases. For systems or channels that showed larger discrepancies, an in-depth analysis of deficiencies was performed and technical solutions and upgrades were proposed and realized. The intercomparisons have reinforced confidence in the EARLINET data quality and allowed us to draw conclusions on necessary system improvements for some instruments and to identify major challenges that need to be tackled in the future.Peer ReviewedPostprint (published version

Aerosol closure study by lidar, sun photometry, and airborne optical counters during DAMOCLES field campaign at El Arenosillo sounding station, Spain

We present a comparison of aerosol properties derived from in situ and remote sensing instruments during DAMOCLES campaign, aimed at investigating the equivalence between the instrumentation and methodologies employed by several Spanish groups to study atmospheric aerosols at a regional background site. The complete set of instruments available during this closure experiment allowed collecting a valuable high-resolution aerosol measurement data set. The data set was augmented with airborne in situ measurements carried out in order to characterize aerosol particles during the midday of 29 June 2006. This work is focused on aerosol measurements using different techniques of high-quality instruments (ground-based remote sensing and aircraft in situ) and their comparisons to characterize the aerosol vertical profiles. Our results indicate that the variability between the detected aerosol layers was negligible in terms of aerosol optical properties and size distributions. Relative differences in aerosol extinction coefficient profiles were less than 20% at 355 and 532 nm and less than 30% at 1064 nm, in the region with high aerosol concentration. Absolute differences in aerosol optical depth (AOD) were below 0.01 at 532 and 1064 nm and less than 0.02 at 355 nm, less than the uncertainties assumed in the AOD obtained from elastic lidar. Columnar values of the lidar ratio revealed some discrepancies with respect to the in situ aircraft measurements, caused fundamentally by the lack of information in the lowest part of the boundary layer.Peer ReviewedPostprint (published version

Monitoring of the Eyjafjallajokull volcanic aerosol plume over the Iberian Peninsula by means of four EARLINET lidar stations

Lidar and sun-photometer measurements were performed intensively over the Iberian Peninsula (IP) during the eruption of the Eyjafjallajokull volcano (Iceland) in April–May 2010. The volcanic plume reached all the IP stations for the first time on 5 May 2010. A thorough study of the event was conducted for the period 5–8 May. Firstly, the spatial and temporal evolution of the plume was described by means of lidar and sun-photometer measurements supported with backtrajectories. The volcanic aerosol layers observed over the IP were rather thin (<1000 m) with a top height up to 11–12 km. However, in some cases at the beginning of the period the thickness of those layers reached several kilometers in Evora and Madrid. The optical thicknesses associated to those layers were rather low (between 0.013 and 0.020 in average over the whole period), with peak values near 0.10 detected on 7 May. Secondly, the volcanic aerosols were characterized in terms of extinction and backscatter coefficients, lidar ratios, Angstrom exponents and linear particle depolarization ratio. Lidar ratios at different sites varied between 30 and 50 sr without a marked spectral dependency. Similar extinction-related Angstrom exponents varying between 0.6 and 0.8 were observed at different sites. The temporal evolution of the backscatter-related Angstrom exponents points out a possible decrease of the volcanic particle size as the plume moved from west to east. Particle depolarization ratios on the order of 0.06–0.08 confirmed the coexistence of both ash and non-ash particles. Additionally, profiles of mass concentration were obtained with a method using the opposite depolarizing effects of ash particles (strongly depolarizing), non-ash particles (very weakly depolarizing), and sun-photometer observations. In Granada the ash mass concentration was found to be approximately 1.5 times higher than that of non-ash particles, and probably did not exceed the value of 200 µgm-3 during the whole event.Peer Reviewe

EARLINET correlative measurements for CALIPSO: first intercomparison results

A strategy for European Aerosol Research Lidar Network (EARLINET) correlative measurements for Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) has been developed. These EARLINET correlative measurements started in June 2006 and are still in progress. Up to now, more than 4500 correlative files are available in the EARLINET database. Independent extinction and backscatter measurements carried out at high-performance EARLINET stations have been used for a quantitative comparison with CALIPSO level 1 data. Results demonstrate the good performance of CALIPSO and the absence of evident biases in the CALIPSO raw signals. The agreement is also good for the distribution of the differences for the attenuated backscatter at 532 nm ((CALIPSO-EARLINET)/EARLINET (%)), calculated in the 1–10 km altitude range, with a mean relative difference of 4.6%, a standard deviation of 50%, and a median value of 0.6%. A major Saharan dust outbreak lasting from 26 to 31 May 2008 has been used as a case study for showing first results in terms of comparison with CALIPSO level 2 data. A statistical analysis of dust properties, in terms of intensive optical properties (lidar ratios, Ångström exponents, and color ratios), has been performed for this observational period. We obtained typical lidar ratios of the dust event of 49 ± 10 sr and 56 ± 7 sr at 355 and 532 nm, respectively. The extinction-related and backscatter-related Ångström exponents were on the order of 0.15–0.17, which corresponds to respective color ratios of 0.91–0.95. This dust event has been used to show the methodology used for the investigation of spatial and temporal representativeness of measurements with polar-orbiting satellites.Peer ReviewedPostprint (published version

Extreme, wintertime Saharan dust outbreak in the Iberian Peninsula: lidar monitoring and evaluation of dust forecast models during the February 2017 event

An unprecedented extreme Saharan dust event was registered in winter time from 20 to 23 February 2017 over the Iberian Peninsula (IP). We report on aerosol optical properties observed under this extreme dust intrusion through passive and active remote sensing techniques. For that, AERONET (AErosol RObotic NETwork) and EARLINET (European Aerosol Research LIdar NETwork) databases are used. The sites considered are: Barcelona (41.38°N, 2.17°E), Burjassot (39.51°N, 0.42°W), Cabo da Roca (38.78°N, 9.50°W), Évora (38.57°N, 7.91°W), Granada (37.16°N, 3.61°W) and Madrid (40.45°N, 3.72°W). Large aerosol optical depths (AOD) and low Ångström exponents (AE) are observed. An AOD of 2.0 at 675¿nm is reached in several stations. A maximum peak of 2.5 is registered in Évora. During and around the peak of AOD, AEs close to 0 and even slightly negative are measured. With regard to vertically-resolved aerosol optical properties, particle backscatter coefficients as high as 15¿Mm-1¿sr-1 at 355¿nm are recorded at the lidar stations. Layer-mean lidar ratios are found in the range 40–55¿sr at 355¿nm and 34–61¿sr at 532¿nm during the event. The particle depolarization ratios are found to be constant inside the dust layer, and consistent from one site to another. Layer-mean values vary in the range 0.19–0.31. Another remarkable aspect of the event is the limited vertical distribution of the dust plume which never exceeds 5¿km. The extreme aspect of the event also presented a nice case for testing the ability of two dust forecast models, BSC-DREAM8b and NMMB/BSC-Dust, to reproduce the arrival, the vertical distribution and the intensity of the dust plume over a long-range transport region. In the particular case of the February 2017 dust event, we found a large underestimation in the forecast of the extinction coefficient provided by BSC-DREAM8b at all heights independently of the site. In contrast NMMB/BSC-Dust forecasts presented a better agreement with the observations, especially in southwestern part of the IP. With regard to the forecast skill as a function of lead time, no clear degradation of the prognostic is appreciated at 24, 48 and 72¿h for Évora and Granada stations (South). However the prognostic does degrade (bias increases and/or correlation decreases) for Barcelona (North), which is attributed to the fact that Barcelona is at a greater distance from the source region and to the singularity of the event.Peer Reviewe