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- ItemTechnical Note: One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India – Seasonal characteristics of the aerosol vertical structure(München : European Geopyhsical Union, 2012) Komppula, M.; Mielonen, T.; Arola, A.; Korhonen, K.; Lihavainen, H.; Hyvärinen, A.-P.; Baars, H.; Engelmann, R.; Althausen, D.; Ansmann, A.; Müller, D.; Panwar, T.S.; Hooda, R.K.; Sharma, V.P.; Kerminen, V.-M.; Lehtinen, K.E.J.; Viisanen, Y.One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analysed. The data was split into four seasons: spring (March–May), summer (June–August), autumn (September–November) and winter (December–February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1–3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm−1 sr−1 and 142 Mm−1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared to other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.
- ItemSurface matters: Limitations of CALIPSO V3 aerosol typing in coastal regions(München : European Geopyhsical Union, 2014) Kanitz, T.; Ansmann, A.; Foth, A.; Seifert, P.; Wandinger, U.; Engelmann, R.; Baars, H.; Althausen, D.; Casiccia, C.; Zamorano, F.In the CALIPSO data analysis, surface type (land/ocean) is used to augment the aerosol characterization. However, this surface-dependent aerosol typing prohibits a correct classification of marine aerosol over land that is advected from ocean to land. This might result in a systematic overestimation of the particle extinction coefficient and of the aerosol optical thickness (AOT) of up to a factor of 3.5 over land in coastal areas. We present a long-term comparison of CALIPSO and ground-based lidar observations of the aerosol conditions in the coastal environment of southern South America (Punta Arenas, Chile, 53° S), performed in December 2009–April 2010. Punta Arenas is almost entirely influenced by marine particles throughout the year, indicated by a rather low AOT of 0.02–0.04. However, we found an unexpectedly high fraction of continental aerosol in the aerosol types inferred by means of CALIOP observations and, correspondingly, too high values of particle extinction. Similar features of the CALIOP data analysis are presented for four other coastal areas around the world. Since CALIOP data serve as important input for global climate models, the influence of this systematic error was estimated by means of simplified radiative-transfer calculations.
- ItemDepolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke(Göttingen : Copernicus GmbH, 2018) Haarig, M.; Ansmann, A.; Baars, H.; Jimenez, C.; Veselovskii, I.; Engelmann, R.; Althausen, D.We present spectrally resolved optical and microphysical properties of western Canadian wildfire smoke observed in a tropospheric layer from 5-6.5 km height and in a stratospheric layer from 15-16 km height during a recordbreaking smoke event on 22 August 2017. Three polarization/ Raman lidars were run at the European Aerosol Research Lidar Network (EARLINET) station of Leipzig, Germany, after sunset on 22 August. For the first time, the linear depolarization ratio and extinction-to-backscatter ratio (lidar ratio) of aged smoke particles were measured at all three important lidar wavelengths of 355, 532, and 1064 nm. Very different particle depolarization ratios were found in the troposphere and in the stratosphere. The obviously compact and spherical tropospheric smoke particles caused almost no depolarization of backscattered laser radiation at all three wavelengths ( < 3 %), whereas the dry irregularly shaped soot particles in the stratosphere lead to high depolarization ratios of 22% at 355 nm and 18% at 532 nm and a comparably low value of 4% at 1064 nm. The lidar ratios were 40- 45 sr (355 nm), 65-80 sr (532 nm), and 80-95 sr (1064 nm) in both the tropospheric and stratospheric smoke layers indicating similar scattering and absorption properties. The strong wavelength dependence of the stratospheric depolarization ratio was probably caused by the absence of a particle coarse mode (particle mode consisting of particles with radius > 500nm). The stratospheric smoke particles formed a pronounced accumulation mode (in terms of particle volume or mass) centered at a particle radius of 350-400 nm. The effective particle radius was 0.32 μm. The tropospheric smoke particles were much smaller (effective radius of 0.17 μm). Mass concentrations were of the order of 5.5 μgm-3 (tropospheric layer) and 40 μgm-3 (stratospheric layer) in the night of 22 August 2017. The single scattering albedo of the stratospheric particles was estimated to be 0.74, 0.8, and 0.83 at 355, 532, and 1064 nm, respectively.
- ItemRadiative effect of aerosols above the northern and southern Atlantic Ocean as determined from shipborne lidar observations(Hoboken, NJ : Wiley, 2013) Kanitz, T.; Ansmann, Albert; Seifert, P.; Engelmann, R.; Althausen, D.The direct solar radiative effect of aerosols over the Atlantic Ocean was investigated on the basis of aerosol Raman/polarization lidar observations aboard the research vessel Polarsternbetween Germany (50°N) and either South America (50°S) or South Africa (40°S) in 2009 and 2010. First, a case study of complex aerosol conditions with marine aerosol, dust, and smoke particles in the boundary layer and free troposphere is presented to demonstrate that detailed knowledge of aerosol layering (boundary layer, free troposphere) and aerosol mixing state is required for an accurate determination of the resulting radiative effects. A statistical analysis based on all lidar observations revealed the highest daily mean radiative effect (−43±59 W m−2at the surface, −14±18 W m−2at top of atmosphere) in the latitudinal belt from 0°N–15°N in the Saharan dust outflow region. Mean aerosol radiative effects of the polluted northern and clean southern midlatitudes were contrasted. In the northern midlatitudes, the averaged aerosol radiative effect of all simulations was −24±33 W m−2at the surface which is a factor of 1.6 higher than at similar southern hemispheric latitudes. The simulations based on the lidar observations are in good agreement with colocated pyranometer measurements.
- ItemContinuous monitoring of the boundary-layer top with lidar(München : European Geopyhsical Union, 2008) Baars, H.; Ansmann, A.; Engelmann, R.; Althausen, D.Continuous lidar observations of the top height of the boundary layer (BL top) have been performed at Leipzig (51.3° N, 12.4° E), Germany, since August 2005. The results of measurements taken with a compact, automated Raman lidar over a one–year period (February 2006 to January 2007) are presented. Main goals of the study are (a) to demonstrate that BL top monitoring with lidar throughout the year is possible, (b) to present the required data analysis method that permits an automated, robust retrieval of BL top at all weather situations, and (c) to use this opportunity to compare the lidar-derived BL top data with respective BL tops hourly predicted by the regional weather forecast model COSMO. Four different lidar methods for the determination of the BL top are discussed. The wavelet covariance algorithm is modified so that an automated retrieval of BL depths from lidar data is possible. Three case studies of simultaneous observations with the Raman lidar, a vertical-wind Doppler lidar, and accompanying radiosonde profiling of temperature and humidity are presented to compare the potential and the limits of the four lidar techniques. The statistical analysis of the one-year data set reveals that the seasonal mean of the daytime (about 08:00–20:00 Local Time, LT) maximum BL top is 1400 m in spring, 1800 m in summer, 1200 m in autumn, and 800 m in winter at the continental, central European site. BL top typically increases by 100–300 m per hour in the morning of convective days. The comparison between the lidar-derived BL top heights and the predictions of COSMO yields a general underestimation of the BL top by about 20% by the model.