Influence of aerosol particles in the cloud formation and microphysical properties, commonly known as aerosolcloud interaction (ACI), has emerged as a research field of special interest since the low-level knowledge on this topic causes the largest uncertainties in climate projections. Active remote sensing already provided promising results combining backscatter lidars and cloud radars to characterize atmospheric aerosol and cloud droplets. The retrieval of aerosol microphysical properties is of high interest for ACI studies. However, complex inversion techniques are usually required. Mamouri and Ansmann (2016) proposed to derive the so-called extinctionto- number-concentration factors to retrieve aerosol number concentration from aerosol extinction in a more straightforward way. These factors can be easily obtained from the relationship between the aerosol number concentration and the aerosol optical depth from AERONET measurements. However, experimental data are not always available. This study demonstrates that it is also possible to obtain the extinction-to-number-concentration factors using pre-calculated optical properties. To do so, MOPSMAP, open-source software based on a data set of pre-calculated single-particle optical properties, is used. Using a study case (9 July 2021), it is shown that number concentration of aerosol-particle with radius larger than 250 μm (n250) derived with MOPSMAP is within the uncertainty range of the one derived with AERONET.
The lidar confederative network for monitoring optical properties of aerosol on Latin America, LALINET, faces an important challenger to cover a large area of Latin America with so few lidar systems. Currently in Brazil there are only three operative lidar systems, two operating on Southeastern region and other on North region of Brazil. Taking into accounting the large dimension of Brazilian territory there is a lack of lidar system monitoring in several regions. In 2014 Laser Environmental Application Laboratory (LEAL) at Nuclear and Energy Research Institute (IPEN) together with Federal University of Rio Grande do Norte (UFRN), have started the first efforts to install a depolarization lidar system at the city of Natal-RN (5°50'29'' S ,35°11'57'' W, 0 m asl), in the Northeast region of Brazil. This new lidar station intends to be in the future integrated to the LALINET network, and has as a first aim to detect and to identify aerosol layers from Saharan dust and biomass burning type arriving from African continent. To examine these transports it is paramount to have a temporally and spatially well resolved observational platforms, which will be able to describe with accuracy the transport patterns followed by these aerosol layers over the Atlantic. To yield a good coverage based on the previously mentioned requirements satellite-based platforms are very well suited, but unless a geostationary system is provided a reasonable temporal representativeness may not be achieved. Our current study is devoted to the first results aiming to detect and identify aerosol layers arriving over the Northeastern region of the South American continent, with a lidar and a sun-photometer recently installed in the city of Natal. Here we present the first aerosol observation results with the lidar system and the sunphotometer carried out from January through May 2016 with the indication of potential dust and other-type aerosol layers through some backscatter profiles.
This work focuses on the statistical analysis of day and night hourly pattern of columnar aerosol properties. To that end, we use the large database of star-photometry measurements at the University of Granada station (37.16°N, 3.60°W, 680 m a.s.l; South-East of Spain) for nighttime characterization, and co-located AERONET measurements for the daytime. The aerosol properties studied are the aerosol optical depth (AOD), Angstrom parameter (α(440-870)), aerosol optical depths of fine (AODfine) and coarse mode (AODcoarse) through the Spectral Deconvolution Algorithm (SDA). Microphysical properties are calculated by inverting AOD spectra and include the effective radius (reff) and volume concentration (V) of the total size distribution, and also the effective radius of the fine mode (rfine). The initial analysis for the different air masses that reach the study area reveals that generally day and night values of AOD and α(440-870) are not different statistically. Nighttime values of AODfine, reff and rfine do however, present larger values. The influence of North African air masses is remarkable both during the day and night, with high particle loads and low values of the Angstrom parameters and also with large contribution of coarse particles as AODcoarse and reff values are almost the double than for other air masses. The analyses of day-to-night hourly values reveal an increase in AOD, AODfine and AODcoarse during the day and a decrease during the night. Such a pattern could be explained by the different emission rates, accumulation, aging and deposition of particles. Changes in particle radius are also observed as part of the day-tonight particle evolution process, being rfine variations important mainly at daytime while for reff variations are more important at nighttime. Results of day-to-night evolution were found to be independent of air mass origin, and seem to be mainly associated with local processes.
Suspended atmospheric particles i.e. aerosol particles go through many chemical and physical processes and those interactions and transformations may cause particle change in size, structure and composition regulated by mechanisms, which are also present in clouds. These interactions play a great role in the radiation transfer in the atmosphere and are not completely understood as competing effects might occur which are known as indirect aerosol effects. Performing measurements and experiments in remote sensing to improve the knowledge of these processes are also a challenge. In face of that we propose a multi-platform approach based lidar, sun photometry and satellite observations which should be characterized under a scenario perspective in which given the cloud height, geometric and optical geometries in a diurnal/nocturnal basis will make possible to apply different analytical tools in each a set of product that specify the aerosol present in the vicinity of clouds, their optical and physical properties. These scenarios are meant to aid in tagging the expected products and help in creating a robust database to systematically study the aerosol-cloud interaction.In total we will present 6 scenarios: 3 under daylight conditions, 3 under at nighttime. Each scenario and their counterpart should be able to provide the cloud base/top height, aerosol backscattering profile and cloud optical/geometric thickness. In each instance we should count on a 5 wavelength Raman lidar system measurement, a collocated sun photometer and CALIPSO/MODIS observation from AQUA/TERRA platforms. To further improve the aerosol cloud interaction the Raman lidar system should have a water vapor channel or moreover a liquid water channel. In our study we will present a two-day case study to show the methodology feasibility and its potential application.
In the framework of the project ChArMEx (the Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/), the variability of aerosol optical, microphysical and radiative properties is examined in three regional background sites on a southwest – northeast (SW–NE) straight line in the middle of the western Mediterranean Basin (WMB). The three sites are on the northward transport pathway of African dust: Ersa, Corsica Island, France (43.00ºN, 9.36ºW, 80 m a.s.l), Palma de Mallorca, Mallorca Island, Spain (39.55ºN, 2.62ºE, 10 m a.s.l) and Alborán, Alboran Island, Spain (35.94ºN, 3.04ºW, 15 m a.s.l). AERONET (AErosol RObotic NETwork) sun-photometer products are mainly used. A preliminary analysis shows that at Ersa and Palma sites the annual aerosol optical depth (AOD) has a similar trend with a peak around 0.2 in July. The winter/spring AOD is lower in Palma than in Ersa, while it is reverse in summer/autumn. The aerosol particle size distribution (and the coarse mode fraction) shows clearly the SW–NE gradient with a decreasing coarse mode peak (and a decreasing coarse mode fraction from 0.5 - 0.35 - 0.2 in July) along the axis Alborán - Palma de Mallorca - Ersa. In addition to the seasonal and annual variability analysis, the analysis of AERONET products is completed with a large variety of ground-based and sounding balloons remote sensing and in situ instruments during the Special Observation Period (SOP) of the ADRIMED campaign in June 2013. The second part of the presentation will focus on the comparison of the observations at Palma de Mallorca and Ersa of the same long-range transported airmasses. The observations include lidar vertical profiles, balloon borne OPC (Optical Particle Counter) and MSG/SEVIRI AOD, among others.
EARLINET, the European Aerosol Research Lidar NETwork, established in 2000, is the first coordinated lidar network
for tropospheric aerosol study on the continental scale. The network activity is based on scheduled measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a standardised data
exchange format. At present, the network includes 27 lidar stations distributed over Europe.
EARLINET performed almost continuous measurements since 15 April 2010 in order to follow the evolution of the
volcanic plume generated from the eruption of the Eyjafjallajökull volcano, providing the 4-dimensional distribution of
the volcanic ash plume over Europe. During the 15-30 April period, volcanic particles were detected over Central Europe
over a wide range of altitudes, from 10 km down to the local planetary boundary layer (PBL). Until 19 April, the
volcanic plume transport toward South Europe was nearly completely blocked by the Alps. After 19 April volcanic
particles were transported to the south and the southeast of Europe. Descending aerosol layers were typically observed
all over Europe and intrusion of particles into the PBL was observed at almost each lidar site that was affected by the
volcanic plume. A second event was observed over Portugal and Spain (6 May) and then over Italy on 9 May 2010. The
volcanic plume was then observed again over Southern Germany on 11 May 2010.
Coordinated lidar observations of Saharan dust over Europe are performed in the frame of the EARLINET-ASOS
(2006-2011) project, which comprises 25 stations: 16 Raman lidar stations, including 8 multi-wavelength
(3+2 station) Raman lidar stations, are used to retrieve the aerosol microphysical properties. Since
the launch of CALIOP, the two-wavelength lidar on board the CALIPSO satellite (June 2006) our lidar
network has been performing correlative aerosol measurements during CALIPSO overpasses over the
individual stations. In our presentation, we report on the correlative measurements obtained during Saharan
dust intrusions in the period from June 2006 to June 2008. We found that the number of dust events is
generally greatest in late spring, summer and early autumn periods, mainly in southern and south-eastern
Europe. A measurement example is presented that was analyzed to show the potential of a ground based lidar
network to follow a dust event over a specific study area, in correlation with the CALIOP measurements. The
dust transport over the studied area was simulated by the DREAM forecast model. Cross-section analyses of
CALIOP over the study area were used to assess the model performance for describing and forecasting the
vertical and horizontal distribution of the dust field over the Mediterranean. Our preliminary results can be
used to reveal the importance of the synergy between the CALIOP measurement and the dust model, assisted
by ground-based lidars, for clarifying the overall transport of dust over the European continent.
Lidar techniques represent the most suitable tool to obtain information on the aerosol vertical distribution and therefore
to close this kind of observational gap. Lidar networks are fundamental to study aerosol on large spatial scale and to
investigate transport and modification phenomena. These are the motivations why EARLINET, the European Aerosol
Research Lidar Network, was established in 2000. At present, EARLINET consists of 25 lidar stations: 7 single
backscatter lidar stations, 9 Raman lidar stations with the UV Raman channel for independent measurements of aerosol
extinction and backscatter, and 9 multiwavelength Raman lidar stations (elastic channel at 1064 nm, 532 nm, 355 nm,
Raman channels at 532 nm and 355 nm, plus depolarization channel at 532 nm) for the retrieval of aerosol microphysical
properties.
EARLINET data can significantly contribute to the quantification of aerosol concentrations, radiative properties, long-range
transport and budget, and prediction of future trends on European and global scale. It can also contribute to
improve model treatment on a wide range of scales and to a better exploitation of present and future satellite data.
EARLINET is playing an important role in the validation and in the full exploitation of the CALIPSO mission.
EARLINET started correlative measurements for CALIPSO since June 2006. A strategy for correlative measurements
has been defined on the base of the analysis of the high resolution ground track data provided by NASA. Results in terms
of comparisons between EARLINET and available CALIPSO products, both level 1 and level 2 data, are presented.
A VAISALA Ceilometer CL31 is operating continuously in the Observatory of the Évora Geophysics Centre (CGE)
since May 2006. The CL31 ceilometer provides measurements of the cloud base height up to three simultaneous layers
and of the profile of the backscatter coefficient, which in the absence of clouds gives a good approximation of the
qualitative aerosol boundary layer profile. The ceilometer backscatter measurements are used here to study special
aerosol events that reach Évora (38°34'N, 7°54'W, 300m a.m.s.l.) such as forest fires, desert dust transports originating
from the Sahara desert, which often occur in the south of Portugal and European pollution. The aerosol backscatter
coefficient corresponding to the lowest layers of the atmosphere is also correlated with mass concentration
measurements obtained from a TEOM (Tapered Element Oscillating Microbalance) installed in the same place (CGE
observatory). The TEOM measures the in situ mass concentration of aerosols near the ground, with aerodynamic
diameter lower than 10μm (PM-10), with temporal sampling of 10min. Furthermore, ceilometer measurements and
derived mixing height are also compared with measurements taken with a Lidar during an intensive campaign that took
place at the CGE observatory in Évora, during the first half of June 2006.
The present knowledge of the aerosol distribution is not sufficient to estimate the aerosol influence on global and
regional environmental conditions and climate. This observational gap can be closed by using advanced laser remote
sensing. EARLINET (European Aerosol Research Lidar Network) is the first aerosol lidar network, established in 2000,
with the main goal to provide a comprehensive, quantitative, and statistically significant database for the aerosol
distribution on a continental scale. EARLINET is a coordinated network of European stations (25 at present) using advanced lidar methods for the vertical profiling of aerosols. The network activity is based on simultaneous scheduled
measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a
standardised data exchange format. Further observations are performed to monitor special events.
EARLINET-ASOS (Advanced Sustainable Observation System) is a five year EC Project started in 2006, based on the
EARLINET infrastructure. The main objectives are: to make EARLINET a world-leading instrument for the observation
of the 4-D aerosol distribution on continental scale; to foster aerosol-related process studies, validation of satellite
sensors, model development and validation, assimilation of aerosol data into operational models; and to build a
comprehensive climatology of the aerosol distribution.
The European Aerosol Research Lidar Network (EARLINET) was established in 2000 to derive a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on the European scale.
At present, EARLINET consists of 25 stations: 16 Raman lidar stations, including 8 multi-wavelength Raman lidar stations which are used to retrieve aerosol microphysical properties.
EARLINET performs a rigorous quality assurance program for instruments and evaluation algorithms. All stations measure simultaneously on a predefined schedule at three dates per week to obtain unbiased data for climatological studies.
Since June 2006 the first backscatter lidar is operational aboard the CALIPSO satellite. EARLINET represents an excellent tool to validate CALIPSO lidar data on a continental scale. Aerosol extinction and lidar ratio measurements provided by the network will be particularly important for that validation.
The measurement strategy of EARLINET is as follows: Measurements are performed at all stations within 80 km from the overpasses and additionally at the lidar station which is closest to the actually overpassed site. If a multi-wavelength Raman lidar station is overpassed then also the next closest 3+2 station performs a measurement.
Altogether we performed more than 1000 correlative observations for CALIPSO between June 2006 and June 2007.
Direct intercomparisons between CALIPSO profiles and attenuated backscatter profiles obtained by EARLINET lidars look very promising.
Two measurement examples are used to discuss the potential of multi-wavelength Raman lidar observations for the validation and optimization of the CALIOP Scene Classification Algorithm.
Correlative observations with multi-wavelength Raman lidars provide also the data base for a harmonization of the CALIPSO aerosol data and the data collected in future ESA lidar-in-space missions.
During the summer 2006 an extended observational campaign of atmospheric aerosol has been developed in the area of Granada, South-eastern Spain. From July to the end of September two Cimel CE-318 radiometers have been operated continuously, one at Andalusian Centre for Environmental Studies (CEAMA), located in the urban area of Granada, a non-industrialized medium size city (37.16ºN, 3.61ºW and 680 m a.m.s.l.), and the second one at the Astronomical Observatory of Sierra Nevada (37.06ºN, 3.38ºW and 2896 m a.m.s.l.), with a short horizontal separation between stations that allows us to consider both instrument located in approximately the same vertical column. The Cimel CE-318 measurements have been used to retrieve the aerosol columnar properties, including the columnar volume size distribution, volume scattering phase function, asymmetry factor and single scattering albedo, by means of appropriate inversion procedures. Additionally, at the CEAMA a Raman Lidar system based on a Nd:YAG laser source operating at 1064, 532 and 355 nm and including elastic, polarized and Raman shifted detection has been used to derive profiles of several atmospheric aerosol properties. In this paper we present analyses of the changes and temporal evolution detected in atmospheric aerosol vertical profile. Several long range transport episodes have been detected and back-trajectories analyses and synoptic information have been used in the discussion of results.
EARLINET-ASOS (European Aerosol Research Lidar Network - Advanced Sustainable Observation System) is a 5-year EC Project started in 2006. Based on the EARLINET infrastructure, it will provide appropriate tools to improve the quality and availability of the continuous observations. The EARLINET multi-year continental scale data set is an excellent instrument to assess the impact of aerosols on the European and global environment and to support future satellite missions. The project is addressed in optimizing instruments and algorithms existing within EARLINET-ASOS, exchanging expertise, with the main goal to build a database with high quality aerosol data. In particular, the optimization of the algorithms for the retrieval of the aerosol optical and microphysical properties is a crucial activity. The main objective is to provide all partners with the possibility to use a common processing chain for the evaluation of their data, from raw signals to final products. Raw signals may come from different types of systems, and final products are profiles of optical properties, like backscatter and extinction, and, if the instrument properties permit, of microphysical properties. This will have a strong impact on the scientific community because data with homogeneous well characterized quality will be made available in nearly real time.
EARLINET, the European Aerosol Research Lidar Network, is the first aerosol lidar network, established in 2000, with the main goal to provide a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on a continental scale. At present, 23 stations distributed over Europe are part of the network. The EARLINET-ASOS (Advanced Sustainable Observation System) EC Project, starting on the EARLINET infrastructure, will contribute to the improvement of continuing observations and methodological developments that are urgently needed to provide the multi-year continental scale data set necessary to assess the impact of aerosols on the European and global environment and to support future satellite missions. The main objective of EARLINET-ASOS 5-year project, started on 1 March 2006, is to improve the EARLINET infrastructure resulting in a better spatial and temporal coverage of the observations, continuous quality control for the complete observation system, and fast availability of standardized data products. This will be reached by defining and using common standards for instruments, operation procedures, observation schemes, data processing including advanced retrieval algorithms, and dissemination of data. The expected outcome is the most comprehensive data source for the 4-D spatio-temporal distribution of aerosols on a continental scale.
Francisco Molero, Lucas Alados-Arboledas, Manuel Pujadas, Antonio Alcantara, Victoria Cachorro, Victor Estellés, Francisco Olmo, José Martinez-Lozano, Jerónimo Lorente, Juan Diaz, Antonio Labajo, Benito De La Morena, Helmut Horvath, Ana Silva
Ground-based sunphotometry measurements can be used to investigate atmospheric aerosol optical properties, such as the volume size distribution, an important parameter in the study of the effect of aerosol on atmospheric processes. Most inversion algorithms assume constant aerosol optical characteristics over the whole air column. In this work we present observational evidence of the limitations of this simplifying assumption in cases where the aerosol vertical
structure is highly inhomogeneous. During the field campaign VELETA 2002, carried out in Granada (Spain), a quite complete characterization of the atmospheric aerosol was obtained by simultaneously measuring the columnar aerosol characteristics, by means of CIMEL C318 sun-tracking photometers, the size-segregated near-surface aerosol mass concentration by a GRIMM 1108 dust monitor and the aerosol vertical profiles by a lidar system. During the last days of the campaign, a dust-rich air mass from the Sahara reached the site, producing a multilayered structure on the aerosol vertical profile. The ground level size distributions can be compared with the columnar ones using retrieved scale height values from a lidar extinction coefficient profiles, corresponding to the altitude where the integrated extinction is equal to 1-e-1 of the AOD. Comparisons of the column-integrated and the modified ground-level aerosol size distributions show a good agreement in the days previous to the arrival of the Saharan intrusion, when the aerosols are homogeneously distributed in a well-mixed boundary layer. But, when the vertical homogeneity is reduced due to elevated layers containing desert dust, the column properties clearly deviates from the surface properties. This indicates the importance of verifying the vertical distribution of aerosol in order to correctly relate column and ground-level optical properties.
Francisco Molero, Manuel Pujadas, Jose Fernandez, Maria Utrillas, Jose Martinez-Lozano, Roberto Pedros, Lucas Alados-Arboledas, Jeronimo Lorente, Victoria Cachorro, Ana Diaz Rodriguez, Antonio Labajo, Benito De la Morena, Jose Antonio Rodrigues, Ana Maria Silva, Helmuth Horvath
KEYWORDS: LIDAR, Aerosols, Mass attenuation coefficient, Signal attenuation, Atmospheric particles, Meteorology, Signal to noise ratio, Atmospheric sensing, Backscatter, Signal processing
We present measurements of the vertical structure of the aerosol extinction coefficient in the lower troposphere, up to five kilometers. Lidar profiles were collected at Armilla (680 m asl) and Pitres (1252 m asl) during the VELETA-2002 campaign, organized to analyze the effect of altitude and aerosols on ground-level UV spectral irradiance. Single-wavelength lidar signals are inverted to derive vertically resolved aerosol extinction coefficient and integrated to provide aerosol optical depth (AOD) at 532 nm. These results are compared with measurements of the aerosol optical depth at the same wavelength provided by Licor LI-1800 spectroradiometers located at several altitudes. Lidar traces show that most of the aerosol loading is present in the first 2.5 km layer before a high-dust Saharan air mass overflew the site. On the 17th of July evening, an elevated aerosol layer was detected between 2.5 and 3.5 km and during the following three days the aerosol vertical profile of the lower atmosphere showed Sahara dust layers, producing relatively high values for the optical depth.
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