Showing papers by "Matthias Wiegner published in 2018"
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TL;DR: Analysis of air mass transport shows that the enhancement of surface aerosols and NO2 concentrations mainly results from accumulation of local emissions under low wind speed conditions.
55 citations
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TL;DR: The MOPSMAP package (Modeled optical properties of ensembles of aerosol particles), which is computationally fast for optical modeling even in the case of complex aerosols, is presented.
Abstract: . The spatiotemporal distribution and characterization of
aerosol particles are usually determined by remote-sensing and optical in
situ measurements. These measurements are indirect with respect to
microphysical properties, and thus inversion techniques are required to
determine the aerosol microphysics. Scattering theory provides the link
between microphysical and optical properties; it is not only needed for such
inversions but also for radiative budget calculations and climate modeling.
However, optical modeling can be very time-consuming, in particular if
nonspherical particles or complex ensembles are involved. In this paper we present the MOPSMAP package (Modeled optical
properties of ensembles of aerosol particles), which is computationally fast for optical
modeling even in the case of complex aerosols. The package consists of a data set
of pre-calculated optical properties of single aerosol particles, a Fortran
program to calculate the properties of user-defined aerosol ensembles, and a
user-friendly web interface for online calculations. Spheres, spheroids, and
a small set of irregular particle shapes are considered over a wide range of
sizes and refractive indices. MOPSMAP provides the fundamental optical
properties assuming random particle orientation, including the scattering
matrix for the selected wavelengths. Moreover, the output includes tables of
frequently used properties such as the single-scattering albedo, the
asymmetry parameter, or the lidar ratio. To demonstrate the wide range of
possible MOPSMAP applications, a selection of examples is presented, e.g.,
dealing with hygroscopic growth, mixtures of absorbing and non-absorbing
particles, the relevance of the size equivalence in the case of nonspherical
particles, and the variability in volcanic ash microphysics. The web interface is designed to be intuitive for expert and nonexpert users.
To support users a large set of default settings is available, e.g., several
wavelength-dependent refractive indices, climatologically representative size
distributions, and a parameterization of hygroscopic growth. Calculations are
possible for single wavelengths or user-defined sets (e.g., of specific
remote-sensing application). For expert users more options for the
microphysics are available. Plots for immediate visualization of the results
are shown. The complete output can be downloaded for further applications.
All input parameters and results are stored in the user's personal folder so
that calculations can easily be reproduced. The web interface is provided at
https://mopsmap.net (last access: 9 July 2018) and
the Fortran program including the data set is freely available for offline
calculations, e.g., when large numbers of different runs for sensitivity
studies are to be made.
44 citations
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TL;DR: The presented algorithm has proven to be highly versatile as it adapts to changes in the size of the training dataset and the number of aerosol classes and classifying parameters and is extremely suitable for the implementation within the single calculus chain (SCC), the EARLINET centralized processing suite.
Abstract: . We present an automatic aerosol classification method based solely on
the European Aerosol Research Lidar Network (EARLINET) intensive optical
parameters with the aim of building a network-wide classification tool that
could provide near-real-time aerosol typing information. The presented method
depends on a supervised learning technique and makes use of the Mahalanobis
distance function that relates each unclassified measurement to a
predefined aerosol type. As a first step (training phase), a reference
dataset is set up consisting of already classified EARLINET data. Using this
dataset, we defined 8 aerosol classes: clean continental, polluted
continental, dust, mixed dust, polluted dust, mixed marine, smoke, and
volcanic ash. The effect of the number of aerosol classes has been explored,
as well as the optimal set of intensive parameters to separate different
aerosol types. Furthermore, the algorithm is trained with literature particle
linear depolarization ratio values. As a second step (testing phase), we
apply the method to an already classified EARLINET dataset and analyze the
results of the comparison to this classified dataset. The predictive accuracy
of the automatic classification varies between 59 % (minimum) and
90 % (maximum) from 8 to 4 aerosol classes, respectively, when evaluated
against pre-classified EARLINET lidar. This indicates the potential use of
the automatic classification to all network lidar data. Furthermore, the
training of the algorithm with particle linear depolarization values found in
the literature further improves the accuracy with values for all the aerosol
classes around 80 %. Additionally, the algorithm has proven to be highly
versatile as it adapts to changes in the size of the training dataset and the
number of aerosol classes and classifying parameters. Finally, the low
computational time and demand for resources make the algorithm extremely
suitable for the implementation within the single calculus chain (SCC), the
EARLINET centralized processing suite.
39 citations
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TL;DR: In this article, a comparison of model simulations of aerosol profiles with measurements of the ceilometer network operated by the GermanWeather Service (DWD) over 1 year from September 2015 to August 2016 is presented.
Abstract: . In this paper, we present a comparison of model simulations of aerosol
profiles with measurements of the ceilometer network operated by the German
Weather Service (DWD) over 1 year from September 2015 to August 2016. The
aerosol forecasts are produced by the Copernicus Atmosphere Monitoring
Service (CAMS) using the aerosol module developed within the Global and
regional Earth-system Monitoring using Satellite and in-situ data (GEMS) and
Monitoring Atmospheric Composition and Climate (MACC) projects and coupled
into the European Centre for Medium-Range Weather Forecasts Integrated
Forecasting System (ECMWF-IFS). As the model output provides mass mixing ratios
of different types of aerosol, whereas the ceilometers do not, it is necessary
to determine a common physical quantity for the comparison. We have chosen
the attenuated backscatter β∗ for this purpose. The
β∗ profiles are calculated from the mass mixing ratios of the model
output assuming the inherent aerosol microphysical properties. Comparison of
the attenuated backscatter averaged between an altitude of 0.2 km (typical
overlap range of ceilometers) and 1 km in general shows similar annual
average values. However, the standard deviation of the difference between
model and observation is larger than the average in 8 out of 12 sites. To investigate possible reasons for the differences, we have examined the
role of the hygroscopic growth of particles and the particle shape. Our
results show that using a more recent particle growth model would result in a
∼22 % reduction of particle backscatter for sea salt aerosols,
corresponding to a 10 % reduction of the total backscatter signal on
average. Accounting for nonspherical dust particles in the model would reduce
attenuated backscatter of dust particles by ∼30 %. As the
concentration of dust aerosol is in general very low in Germany, a
significant effect on the total backscatter signal is restricted to dust
episodes. In summary, consideration of both effects tends to improve the
agreement between model and observations but without leading to a perfect
consistency. In addition, a strong Saharan dust event was investigated to study the
agreement of the spatiotemporal distribution of particles. It was found that
the arrival time of the dust layer and its vertical extent very well agree
between model and ceilometer measurements for several stations. This
underlines the potential of a network of ceilometers to validate the
dispersion of aerosol layers.
25 citations
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TL;DR: In this paper, a comparison of European Centre for Medium-Range Weather Forecast Integrated Forecast System (ECMWF-IFS) model simulation of aerosol backscatter profiles with measurements of the ceilometer network operated by the German weather service (DWD) over 1 year from September 2015 to August 2016 is presented.
Abstract: . In this paper, we present a comparison of European Centre for Medium-Range Weather Forecast Integrated Forecast System (ECMWF-IFS) model simulation of aerosol backscatter profiles with measurements of the ceilometer network operated by the German weather service (DWD) over 1 year from September 2015 to August 2016. As the model output provides mass mixing ratios of different types of aerosol whereas the ceilometers don't, it is necessary to determine a common physical quantity for the comparison. We have chosen the attenuated backscatter β * for this purpose. The β *-profiles are calculated from the mass mixing ratios of the model output assuming the inherent aerosol microphysical properties. Comparison of the attenuated backscatter, averaged between an altitude from 0.2 km (typical overlap range of ceilometers) and 1 km, showed slightly larger values from the model. To investigate possible reasons for the differences, we have examined the role of the hygroscopic growth of particles and the particle shape. Our results show that using a more recent particle growth model would result in a ~ 22 % reduction of particle backscatter for sea salt aerosols, corresponding to a 10 %-reduction of the total backscatter signal on average. Accounting for non-spherical dust particles in the model would reduce attenuated backscatter of dust particles by ~ 30 %. As the concentration of dust aerosol is in general very low in Germany, a significant effect on the total backscatter signal is restricted to dust episodes. In summary, consideration of both effects tend to improve the agreement between model and observations, but without leading to a perfect consistency. In addition a case study was conducted to investigate the agreement of the spatiotemporal distribution of particles. It was found that for a dust episode in April 2016 the arrival time of the dust layer and its vertical extent very well agree between model and ceilometer measurements for several stations. However, due to the large set of parameters characterizing the aerosol distribution and the complexity of the ceilometer retrieval an automated and quantitative comparison scheme for β *-profiles is still missing. Consequently, the representativeness of the case study remains open.
4 citations
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TL;DR: In this paper, an aerosol classification method for EARLINET (European Aerosol Research Lidar Network) measurements is introduced which makes use of the Mahalanobis distance classifier.
Abstract: Aerosol typing is essential for understanding the impact of the different aerosol sources on climate, weather system and air quality. An aerosol classification method for EARLINET (European Aerosol Research Lidar Network) measurements is introduced which makes use the Mahalanobis distance classifier. The performance of the automatic classification is tested against manually classified EARLINET data. Results of the application of the method to an extensive aerosol dataset will be presented.
4 citations
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TL;DR: The presented method depends on a supervised learning technique and makes use of the Mahalanobis distance function that relates each un-classified measurement to a pre-defined aerosol type, making the algorithm extremely suitable for the implementation within the Single Calculus Chain, the EARLINET centralised processing suite.
Abstract: . We present an automatic aerosol classification method based solely on European Aerosol Research Lidar Network (EARLINET) intensive optical parameters with the aim of building a network-wide classification tool that could provide near-real-time aerosol typing information. The presented method depends on a supervised learning technique and makes use of the Mahalanobis distance function that relates each un-classified measurement to a pre-defined aerosol type. As a first step (training phase), a reference dataset is set up consisting of already classified EARLINET data. Using this dataset, we defined eight aerosol classes: clean continental, polluted continental, dust, mixed dust, polluted dust, mixed marine, smoke, and volcanic ash. The effect of the number of aerosol classes has been explored, as well as the optimal set of intensive parameters to separate different aerosol types. Furthermore, the algorithm is trained with literature particle linear depolarization ratio values. As a second step (testing phase), we apply the method to an already classified EARLINET dataset and analyse the results of the comparison to this classified dataset. The predictive accuracy of the automatic classification varies between 59 % (minimum) and 90 % (maximum) from 8 to 4 aerosol classes, respectively, when evaluated against pre-classified EARLINET lidar. This indicates the potential use of the automatic classification to all network lidar data. Furthermore, the training of the algorithm with particle linear depolarization values found in literature further improves the accuracy: the accuracy range is 69–93 % from 8 (69 %) to 4 (93 %) aerosol classes, respectively. Additionally, the algorithm has proven to be highly versatile as it adapts to changes in the size of the training dataset and the number of aerosol classes and classifying parameters. Finally, the low computational time and demand for resources make the algorithm extremely suitable for the implementation within the Single Calculus Chain (SCC), the EARLINET centralised processing suite.
3 citations