Polly<sup>NET</sup> is a growing global network of automatized multiwavelength polarization Raman lidars of type Polly (Althausen et al., 2009). The goal of this network is to conduct advanced remote measurements of aerosol profiles and clouds by the same type of instrument. Since 2006 this network assists the controlling and adjustment activities of Polly systems. A central facility receives the data from the Polly measurements. The observational data are displayed in terms of quicklooks at http://polly:tropos.de in near real time. In this way, the network serves as a central information platform for inquisitive scientists. Polly<sup>NET</sup> comprises permanent stations at Leipzig (Germany), Kuopio (Finland), Evora (Portugal), Baengnyeong Island (South Korea), Stockholm (Sweden), and Warsaw (Poland). Non-permanent stations have been used during several field experiments under both urban and very remote conditions - like the Amazon rainforest. These non-permanent stations were lasting from several weeks up to one year and have been located in Brazil, India, China, South Africa, Chile, and also aboard the German research vessels Polarstern and Meteor across the Atlantic. Within Polly<sup>NET</sup> the interaction and knowledge exchange is encouraged between the Polly operators. This includes maintenance support in system calibration procedures and distribution of latest hardware and software improvements. This presentation introduces the Polly<sup>NET</sup>. Main features of the Polly systems will be presented as well as recent instrumental developments. Some measurement highlights achieved within Polly<sup>NET</sup> are depicted.
The study of interactions between aerosol particles, atmospheric dynamics and clouds and their resulting corresponding
indirect effects on precipitation and radiative transfer demand new measurement strategies combining the strength of
lidar, radar, and in-situ instrumentation. To match this challenge the <i>Leipzig Aerosol and Cloud Remote Observations
System</i> (LACROS) has been set up at TROPOS, combining the strengths of a unique set of active and passive remote
sensing and in-situ measurement systems.
Multiwavelength Raman lidar observations have matured into a powerful tool for the vertical resolved characterization of optical and microphysical properties of atmospheric aerosol particles. Raman lidars that operate with laser pulses at three wavelengths are the minimum requirement for a comprehensive particle characterization. Parameters that are derived with such systems are particle backscatter and extinction coefficients, and particle extinction-to-backscatter (lidar) ratios. Effective radius and complex refractive index can be derived with inversion algorithms. In the past ten years we carried out regular observations over Leipzig, Germany, with multiwavelength Raman lidar. We could
establish a time series of important aerosol properties. For instance, we find that pollution layers are present in the free troposphere in more than 30% of our observations in each year. These layers result from long-range transport of, e.g., forest-fire smoke from North America and Siberia, anthropogenic pollution from North America, Arctic haze from North polar areas, and mineral dust from the Sahara. Observations were also carried out with our mobile six-wavelength Raman lidar during several international field campaigns since 1997. Those data allow us to establish a first comprehensive overview on the vertical distribution of optical and microphysical particle properties in different areas of the world.
The transportable scanning six-wavelength eleven-channel aerosol lidar of the Insitute for Tropospheric Research represents the most powerful tool for a comprehensive characterization of atmospheric particles with lidar. Particle backscatter coefficients are determined at 6 wavelengths between 355 and 1064 nm. Particle extinction coefficients are determined at 355 and 532 nm. The instrument makes use of the elastic backscatter, Raman lidar, and scanning lidar technique. The physical particle parameters including the single-scattering albedo are retrieved from the optical data with an inversion scheme based on Tikhonov's inversion with regularization. The optical and physical parameter allow to perform radiative impact studies on the basis of lidar observations. The system was successfully operated in the Aerosol Characterization Experiment 2 (ACE 2) and the Indian Ocean Experiment (INDOEX). A measurement example taken from the Lindenberg Aerosol Characterization Experiment 98 (LACE 98) exemplifies the potential of this instrument.
This lecture describes the development of lidar techniques to measure the atmospheric temperature profile. Particular attention is given in the lecture to the technique that uses pure rotational Raman scattering of light by molecular nitrogen and oxygen. At present, this approach to temperature profiling in the atmosphere with lidars has received a new impulse because of recent advances in laser and optoelectronics technologies. The instrumentation aspects that determine the feasibility of one or another lidar technique to measure temperature profiles based on the pure rotational Raman spectrum (PRRS) of N<SUB>2</SUB> and O<SUB>2</SUB> molecules are considered. The primary instrumental problem is isolation of extremely weak Raman-lidar returns within the PRRS of N<SUB>2</SUB> and O<SUB>2</SUB> against the background from the much stronger line of unshifted scattering. Mie + Rayleigh, that simultaneously contributes to lidar returns. Besides, the daytime sky background is the factor that severely hampers daytime lidar measurements especially in the case with Raman lidars. So it is an important task of Raman-lidar technologists to find proper ways to overcome this difficulty that would made it possible the temperature profiling in the atmosphere to be performed whole day round. The approach to achieving this task by use of a Fabry-Perot interferometer (FPI) is discussed in the lecture.
A transportable scanning multiwavelength lidar has been installed for the independent and simultaneous determination of the particle backscatter coefficient at 6 wavelengths between 355 and 1064 nm and of the particle extinction coefficient at 355 and 532 nm. The physical particle parameters including the complex refractive index are retrieved from the optical data by an inversion scheme based on the Tikhonov's regularization technique. The optical and physical parameter sets serve as input in radiative transfer calculations to estimate the radiative forcing of the particles at the top of the atmosphere and at the surface. Quite different particle properties could be observed during the Aerosol Characterization Experiment (Portugal, 1997), the Lindenberger Aerosol Experiment (Germany, 1998) and the Indian Ocean Experiment (Maldives, 1999-2000). We present measurement examples which demonstrates this approach of comprehensive aerosol characterization.