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.

2016, Mamouri, Rodanthi-Elisavet, Ansmann, Albert

We investigate the potential of polarization lidar to provide vertical profiles of aerosol parameters from which cloud condensation nucleus (CCN) and ice nucleating particle (INP) number concentrations can be estimated. We show that height profiles of particle number concentrations n50, dry considering dry aerosol particles with radius  > 50 nm (reservoir of CCN in the case of marine and continental non-desert aerosols), n100, dry (particles with dry radius  >  100 nm, reservoir of desert dust CCN), and of n250, dry (particles with dry radius  >  250 nm, reservoir of favorable INP), as well as profiles of the particle surface area concentration sdry (used in INP parameterizations) can be retrieved from lidar-derived aerosol extinction coefficients σ with relative uncertainties of a factor of 1.5–2 in the case of n50, dry and n100, dry and of about 25–50 % in the case of n250, dry and sdry. Of key importance is the potential of polarization lidar to distinguish and separate the optical properties of desert aerosols from non-desert aerosol such as continental and marine particles. We investigate the relationship between σ, measured at ambient atmospheric conditions, and n50, dry for marine and continental aerosols, n100, dry for desert dust particles, and n250, dry and sdry for three aerosol types (desert, non-desert continental, marine) and for the main lidar wavelengths of 355, 532, and 1064 nm. Our study is based on multiyear Aerosol Robotic Network (AERONET) photometer observations of aerosol optical thickness and column-integrated particle size distribution at Leipzig, Germany, and Limassol, Cyprus, which cover all realistic aerosol mixtures. We further include AERONET data from field campaigns in Morocco, Cabo Verde, and Barbados, which provide pure dust and pure marine aerosol scenarios. By means of a simple CCN parameterization (with n50, dry or n100, dry as input) and available INP parameterization schemes (with n250, dry and sdry as input) we finally compute profiles of the CCN-relevant particle number concentration nCCN and the INP number concentration nINP. We apply the method to a lidar observation of a heavy dust outbreak crossing Cyprus and a case dominated by continental aerosol pollution.