Research Group
"Optical Remote Measurements - Analysis of Atmospheric Processes with Optical Methods"

LACE 98 - LINDENBERG AEROSOL CHARACTERIZATION EXPERIMENT 1998 funded by the German Ministry of Education and Science within the Aerosol Research Focus (AFS)

Introduction

Backscattering and absorption of solar radiation by aerosol particles is an important source of uncertainty in climate predictions. Integrated research on the radiative properties of aerosol may reduce this uncertainty. The Lindenberg Aerosol Characterization Experiment 1998 (LACE 98) contributed to this aim. LACE 98 took place between July 13 and August 12, 1998, near Berlin, Germany. The Lindenberg Meteorological Observatory (52.2^o N, 14.1^o E) was chosen as the central field site because of its long record of aerosol-optical-depth data.
Measurements were performed from three aircraft, with one airborne and four ground-based lidars, and at a ground station. The meteorological situations in which intensive observations were carried out included clean and polluted air masses as characterized by low and high aerosol optical depths.

Objectives

The overall goal of integrated aerosol characterization experiments is to provide experimental data needed to properly describe aerosol particles in atmospheric models. A second focus is to test and improve parameterization schemes which are used in field experiments as well as in climate models to determine aerosol radiative effects from basic chemical and physical/optical properties of aerosol particles.
Following this line, the specifc tasks of LACE 98 were threefold:

(a)

Study of the interaction of the atmospheric aerosol system with the radiation field over a polluted central European site during the summer season,

(b)

quantifcation of the uncertainties of the optical properties of the particles and associated radiative effects, calculated from measured chemical composition and particle size distribution of the aerosol, and

(c)

quantifcation of the direct climatic effect of the observed, anthropogenic aerosol particles.

To meet these three objectives, measurements of the aerosol radiative effects (solar irradiances) with vertical resolution are needed in conjunction with profile measurements of chemical, microphysical, and optical aerosol properties.

Another goal of LACE 98 was to introduce new aerosol analysis and measurement techniques and to demonstrate their potential. As an example, for the first time, several advanced aerosol lidars were involved in a large aerosol field campaign. These lidars allow a comprehensive characterization of optical and microphysical properties.

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Observation of forest-fire aerosol from Canada (above 2 km height) and of
the diurnal cycle of the planetary boundary layer with the IfT six-wavelength lidar;
LACE 98, Lindenberg, Germany, August 9th and 10th, 1998
(See also Inversion Algorithm!)
(Click on picture to enlarge!)

Conclusions

A comprehensive aerosol data set for a continental European site is now available. On the basis of complex, complementary observations at ground, with aircraft and remote sensing, the chemical, physical, optical, and radiative properties of typical central European, summertime aerosol distributions are described. These data are a valuable contribution to the global aerosol climatology. They can be used as input parameters in atmospheric models and as ground-truth values in applications of spaceborne aerosol remote sensing over land. In this sense, LACE 98 contributed to the field of research that deals with the impact of aerosols on climate and the respective modelling approaches. A considerable number of closure studies have been done to investigate the relationships between physico-chemical particle properties and the radiation field and to quantify the radiative impact of the observed aerosol distributions as well as the uncertainties in the observations and determinations. The potential and limits of a variety of new and established aerosol observational and analysis techniques were demonstrated. Problems in the characterization of the radiative effects of aerosol at ambient conditions mainly arise from the uncertainties in the determined particle absorption properties. The fact that most in situ measurements are done under low, nonambient humidity conditions causes another source of uncertainty. Radiative closure studies demonstrated that more work is needed in order to improve the knowledge of radiative transfer in the atmosphere. Spaceborne remote sensing over land still remains a challenging task keeping in mind the large (dominant) influence of the surface albedo on the radiation field at short wavelengths.

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Nighttime observation of the Canadian forest-fire aerosol layser (IfT six-wavelength lidar);
2000 UTC on August 9th – 0300 UTC on August 10th;
at the same time in situ aerosol observations were performed onboard the research aircraft Falcon.
(Click on picture to enlarge!)

Summary

A detailed summary of LACE 98 is given in:

Journal of Geophysical Research, Volume 107, Number D21, November 2002.

Our group contributed with the following publications to LACE 98:

Ansmann, A., Wandinger, U., Wiedensohler, A. and Leiterer, U. 2002. Lindenberg Aerosol Characterization Experiment 1998 (LACE 98): Overview. J. Geophys. Res., 107, 2000JD000233.

Wandinger, U., Müller, D., Böckmann, C., Althausen, D., Matthias, V., Bösenberg, J., Weiß, V., Fiebig, M., Wendisch, M., Stohl, A. and Ansmann, A. 2002. Optical and microphysical characterization of biomass-burning and industrial-pollution aerosols from multiwavelength lidar and aircraft measurements. J. Geophys. Res., 107, 2000JD000202.

Fiebig, M., Petzold, A., Wandinger, U., Wendisch, M., Kiemle, C., Stifter, A., Ebert, M., Rother, T. and Leiterer, U. 2002. Optical closure for an aerosol column: Method, accuracy, and inferable properties applied to a biomass-burning aerosol and its radiative forcing. J. Geophys. Res., 107, 2000JD000192.

Wendisch, M., Keil, A., Müller, D., Wandinger, U., Wendling, P., Stifter, A., Petzold, A., Fiebig, M., Wiegner, M., Freudenthaler, V., Armbruster, W., von Hoyningen-Huene, W. and Leiterer, U. 2002. Aerosol-radiation interaction in the cloudless atmosphere during LACE 98, 1, Measured and calculated broadband solar and spectral surface insolations. J. Geophys. Res., 107, 2000JD000226.


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