Retrieval of aerosol complex refractive index from a synergy between lidar, sunphotometer and in situ measurements during LISAIR experiment

Raut, Jean-Christophe; Chazette, Patrick

doi:10.5194/acp-7-2797-2007

Cited by 63 publications

(35 citation statements)

References 92 publications

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“…A sensitivity of the impact of non-sphericity on Lidar ratio has been done the 28 June 2011, when strongly depolarizing particle and photometer measurements were present (δ > 40 %). The Lidar ratio retrieve with the synergy of Lidar and photometer (Raut and Chazette, 2007;Cuesta et al, 2008) was 75 Sr −1 . The difference with the Lidar ratio computed with the procedure described previously is lower than 18 %.…”

Section: Uncertainties Discussionmentioning

confidence: 99%

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

et al. 2012

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Abstract. During the Eyjafjallajökull eruption (14 April to 24 May 2010), the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles) were detected in the free troposphere above the Puy de Dôme station, (PdD, France) with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polarization channels. These layers in the free troposphere (FT) were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the planetary boundary layer (PBL). Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD). In agreement with the FLEXPART simulation, up to 65 µg m −3 of particle mass and 2.2 ppb of SO 2 were measured at PdD, corresponding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number concentration of particles increased to 24 000 cm −3 , mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 µm. The resulting optical properties of the ash aerosol were characterized by a low scatteringÅngström exponent (0.98), showing the presence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physical characterization of the volcanic ash allowed the calculation of the mass-to-extinction ratio (η) with no assumptions on the aerosol density. The mass-to-extinction ratio was found to be significantly different from the background boundary layer aerosol (max: 1.57 g m −2 as opposed to 0.33 ± 0.03 g m −2 ). Using this ratio, ash mass concentration in the volcanic plume derived from LIDAR measurements was found to be 655 ± 23 µg m −3 when the plume was located in the FT (3000 m above the sea level -a.s.l.).This ratio could also be used to retrieve an aerosol mass concentration of 579 ± 60 µg m −3 on 19 April, when LIDAR observations detected the ash cloud at 3000 m a.s.l. in correspondence with model simulations (FLEXPART). On 22 April, another ash plume entered the BL, and although it was more diluted than during the May episode, the French research aircraft ATR42 that passed over Clermont-Ferrand in the PBL confirmed the presence of particles with a supermicronic mode, again with a modal diameter at 2 µm.This data set combining airborne, ground-based and remote sensing observations with dispersion model simulations shows an overall very good coherence during the volcanic eruption period, which allows a good confidence in the characteristics of the ash particles that can be derived from this unique data set.Published by Copernicus Publications on behalf of the European Geosciences Union. M. Hervo et al.: Ground-based, Lidar and airborne measurements of volcanic ashes in France

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Section: Uncertainties Discussionmentioning

confidence: 99%

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

et al. 2012

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“…Thanks to the new generation of portable lidar systems developed in the past five years, accurate vertical profiles of aerosols can now be measured (Raut and Chazette, 2007;Chazette et al, 2007). Such instruments document the mid and lower troposphere by means of aerosol optical properties.…”

Section: Y Wang Et Al: Data Assimilationmentioning

confidence: 99%

Assimilation of ground versus lidar observations for PM<sub>10</sub> forecasting

et al. 2013

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Abstract. This article investigates the potential impact of future ground-based lidar networks on analysis and short-term forecasts of particulate matter with a diameter smaller than 10 µm (PM 10 ). To do so, an Observing System Simulation Experiment (OSSE) is built for PM 10 data assimilation (DA) using optimal interpolation (OI) over Europe for one month from 15 July to 15 August 2001. First, using a lidar network with 12 stations and representing the "true" atmosphere by a simulation called "nature run", we estimate the efficiency of assimilating the lidar network measurements in improving PM 10 concentration for analysis and forecast. It is compared to the efficiency of assimilating concentration measurements from the AirBase ground network, which includes about 500 stations in western Europe. It is found that assimilating the lidar observations decreases by about 54 % the root mean square error (RMSE) of PM 10 concentrations after 12 h of assimilation and during the first forecast day, against 59 % for the assimilation of AirBase measurements. However, the assimilation of lidar observations leads to similar scores as AirBase's during the second forecast day. The RMSE of the second forecast day is improved on average over the summer month by 57 % by the lidar DA, against 56 % by the AirBase DA. Moreover, the spatial and temporal influence of the assimilation of lidar observations is larger and longer. The results show a potentially powerful impact of the future lidar networks. Secondly, since a lidar is a costly instrument, a sensitivity study on the number and location of required lidars is performed to help define an optimal lidar network for PM 10 forecasts. With 12 lidar stations, an efficient network in improving PM 10 forecast over Europe is obtained by regularly spacing the lidars. Data assimilation with a lidar network of 26 or 76 stations is compared to DA with the previously-used lidar network. During the first forecast day, the assimilation of 76 lidar stations' measurements leads to a better score (the RMSE decreased by about 65 %) than AirBase's (the RMSE decreased by about 59 %).

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“…Aging processes can again explain this increase of the fine mode radius. Particularly the hygroscopic growth is an important factor at high relative humidity for anthropogenic particles (e.g., Kotchenruther et al, 1999;Raut and Chazette, 2007;Randriamiarisoa et al, 2006;Veselovskii et al, 2009). But again we have to insist on the limitations of the methodology proposed that does not allow the separation between any processes.…”

Section: Pérez-ramírez Et Al: Columnar Aerosol Properties From Sumentioning

confidence: 99%

Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic

et al. 2012

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Abstract. This work presents the first analysis of longterm correlative day-to-night columnar aerosol optical properties. The aim is to better understand columnar aerosol dynamic from ground-based observations, which are poorly studied until now. To this end we have used a combination of sun-and-star photometry measurements acquired in the city of Granada (37.16 • N, 3.60 • W, 680 m a.s.l.; South-East of Spain) from 2007 to 2010. For the whole study period, mean aerosol optical depth (AOD) around 440 nm (±standard deviation) is 0.18 ± 0.10 and 0.19 ± 0.11 for daytime and nighttime, respectively, while the mean Angström exponent (α) is 1.0 ± 0.4 and 0.9 ± 0.4 for daytime and nighttime. The ANOVA statistical tests reveal that there are no significant differences between AOD and α obtained at daytime and those at nighttime. Additionally, the mean daytime values of AOD and α obtained during this study period are coherent with the values obtained in the surrounding AERONET stations. On the other hand, AOD around 440 nm present evident seasonal patterns characterised by large values in summer (mean value of 0.20 ± 0.10 both at daytime and nighttime) and low values in winter (mean value of 0.15 ± 0.09 at daytime and 0.17 ± 0.10 at nighttime). The Angström exponents also present seasonal patterns, but with low values in summer (mean values of 0.8 ± 0.4 and 0.9 ± 0.4 at dayand night-time) and relatively large values in winter (mean values of 1.2 ± 0.4 and 1.0 ± 0.3 at daytime and nighttime). These seasonal patterns are explained by the differences in the meteorological conditions and by the differences in the strength of the aerosol sources. To take more insight about the changes in aerosol particles between day and night, the spectral differences of the Angström exponent as function of the Angström exponent are also studied. These analyses reveal increases of the fine mode radius and of the fine mode contribution to AOD during nighttime, being more remarkable in the summer seasons. These variations are explained by the changes of the local aerosol sources and by the meteorological conditions between daytime and nighttime, as well as aerosol aging processes. Case studies during summer and winter for different aerosol loads and types are also presented to clearly illustrate these findings.

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Retrieval of aerosol complex refractive index from a synergy between lidar, sunphotometer and in situ measurements during LISAIR experiment

Cited by 63 publications

References 92 publications

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

Assimilation of ground versus lidar observations for PM<sub>10</sub> forecasting

Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic

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Retrieval of aerosol complex refractive index from a synergy between lidar, sunphotometer and in situ measurements during LISAIR experiment

Cited by 63 publications

References 92 publications

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

Assimilation of ground versus lidar observations for PM&lt;sub&gt;10&lt;/sub&gt; forecasting

Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic

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Assimilation of ground versus lidar observations for PM<sub>10</sub> forecasting