Jana Preißler

PollyNET: a network of multiwavelength polarization Raman lidars

PollyNET 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. PollyNET 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 PollyNET 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 PollyNET. Main features of the Polly systems will be presented as well as recent instrumental developments. Some measurement highlights achieved within PollyNET are depicted.

Forest Fire Smoke Layers Observed in the Free Troposphere over Portugal with a Multiwavelength Raman Lidar: Optical and Microphysical Properties

Vertically resolved optical and microphysical properties of biomass burning aerosols, measured in 2011 with a multiwavelength Raman lidar, are presented. The transportation time, within 1-2 days (or less), pointed towards the presence of relatively fresh smoke particles over the site. Some strong layers aloft were observed with particle backscatter and extinction coefficients (at 355 nm) greater than 5 Mm−1 sr−1 and close to 300 Mm−1, respectively. The particle intensive optical properties showed features different from the ones reported for aged smoke, but rather consistent with fresh smoke. The Ångström exponents were generally high, mainly above 1.4, indicating a dominating accumulation mode. Weak depolarization values, as shown by the small depolarization ratio of 5% or lower, were measured. Furthermore, the lidar ratio presented no clear wavelength dependency. The inversion of the lidar signals provided a set of microphysical properties including particle effective radius below 0.2 μm, which is less than values previously observed for aged smoke particles. Real and imaginary parts of refractive index of about 1.5-1.6 and 0.02i, respectively, were derived. The single scattering albedo was in the range between 0.85 and 0.93; these last two quantities indicate the nonnegligible absorbing characteristics of the observed particles.

Optical porperties of free tropospheric aerosol from multi-wavelength raman lidars over the southern Iberian Peninsula

Lidars are ideally placed to investigate the effects of aerosol and cloud on the climate system due to their unprecedented vertical and temporal resolution. Dozens of techniques have been developed in recent decades to retrieve the extinction and backscatter of atmospheric particulates in a variety of conditions. These methods, though often very successful, are fairly ad hoc in their construction, utilising a wide variety of approximations and assumptions that makes comparing the resulting data products with independent measurements difficult and their implementation in climate modelling virtually impossible. As with its application to satellite retrievals, the methods of non-linear regression can improve this situation by providing a mathematical framework in which the various approximations, estimates of experimental error, and any additional knowledge of the atmosphere can be clearly defined and included in a mathematically ‘optimal’ retrieval method, providing rigorously derived error estimates. In addition to making it easier for scientists outside of the lidar field to understand and utilise lidar data, it also simplifies the process of moving beyond extinction and backscatter coefficients and retrieving microphysical properties of aerosols and cloud particles. Such methods have been applied to a prototype Raman lidar system. A technique to estimate the lidar’s overlap function using an analytic model of the optical system and a simple extinction profile has been developed. This is used to calibrate the system such that a retrieval of the profile extinction and backscatter coefficients can be performed using the elastic and nitrogen Raman backscatter signals.

Vertically resolved optical and microphysical properties of Portuguese forest fire smoke observed in February 2012

For the first time fresh biomass burning aerosol from wild fires in the north of Portugal was studied in detail by analysing profiles of optical and microphysical particle properties obtained from multiwavelength Raman lidar measurements. During the driest February since 1931, in 2012, an unusual high number of forest fires occurred in the north of the country. Despite the strong fires and back-trajectories directly crossing the burning areas, the optical and microphysical properties indicate a mixture of the biomass burning smoke with dust from the dried out soil of the Iberian peninsula or with other aerosol types. The layer means of the particle effective radius, the real part of the complex refractive index (CRI), and the imaginary part of the CRI ranged, respectively, from 0.20 μm to 0.30 μm, from 1.52 to 1.64, and from 0.009 to 0.017. The large single scattering albedo between 0.92 and 0.96, 0.92 and 0.96, and 0.88 and 0.94 at 355, 532 and 1064 nm, respectively, indicate weak absorption.