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. PollyXT Raman polarization lidar observations wereperformed at the Remote Sensing Laboratory (RS-Lab) in Warsaw(52.2109 ∘  N, 20.9826 ∘  E), Poland, in the framework ofthe European Aerosol Research Lidar Network (EARLINET) and the Aerosol,Clouds, and Trace gases Research Infrastructure (ACTRIS) projects. Data collected inJuly, August, and September of 2013, 2015, and 2016 were analysed using theclassical Raman approach. In total, 246 sets of intact profiles, each setcomprising particle extinction ( α ) and backscatter coefficients( β ) as well as linear particle depolarization ratios ( δ ) at 355 nmand 532 nm, were derived for statistical investigations and stored in theEARLINET/ACTRIS database. The main analysis was focused on intensiveoptical properties obtained within the atmospheric boundary layer (ABL). Theirinterrelations were discussed for different periods: the entire day; nighttime, with respect to the nocturnal boundary layer (NL) and the residual boundary layer (RL); at sunrise, with respect to the morning transition boundary layer (MTL); and from late afternoon until sunset, with respect to the well-mixed boundary layer (WML). Within the boundary layer, the lidar-derived opticalproperties (entire day, 246 sets) revealed a mean aerosol optical depth(AOD ABL ) of 0.20±0.10 at 355 nm and 0.11±0.06 at 532 nm;a mean Angstrom exponent (AE ABL ) of 1.54±0.37 ; amean lidar ratio (LR ABL ) of 48±17  sr at 355 nm and 41±15  sr at532 nm; a mean linear particle depolarization ratio ( δABL ) of 0.02±0.01 at 355 nm and 0.05±0.01 at 532 nm; anda mean water vapour mixing ratio (WV ABL ) of 8.28±2.46  g kg −1 . Inaddition, the lidar-derived daytime boundary layer optical properties (for theMTL and WML) were compared with the corresponding daytime columnar aerosolproperties derived from the multi-filter rotating shadowband radiometer (MFR-7) measuring within theNational Aerosol Research Network (PolandAOD-NET) and the CE318 sun photometer of the Aerosol Robotic NETwork (AERONET). A high linear correlation of thecolumnar aerosol optical depth values from the two latter instruments was obtained inWarsaw (a correlation coefficient of 0.98 with a standard deviationof 0.02). The contribution of the aerosol load in the summer and early-autumnfree troposphere can result in an AOD CL value that is twice as high as the AOD ABL over Warsaw. The occurrence of a turbulence-driven aerosol burst from theboundary layer into the free troposphere can further increase thisdifference. Aerosol within the ABL and in the free troposphere was interpretedbased on comparisons of the properties derived at different altitudes withvalues reported in the literature, which were characteristic for differentaerosol types, in combination with backward trajectory calculations,satellite data, and model outputs. Within the boundary layer, the aerosol consisted ofeither urban anthropogenic pollution ( ∼  61 %) or mixtures of anthropogenic aerosol with biomass-burning aerosol (  14 %), local pollen(  7 %), or Arctic marine particles (  5 %). Nosignificant contribution of mineral dust was found in the boundary layer.The lidar-derived atmospheric boundary layer height (ABLH) and the AOD ABL exhibited a positive correlation ( R of 0.76), associated with the localanthropogenic pollution (most pronounced for the RL and WML). Apositive correlation of the AOD ABL and LR ABL and a negativecorrelation of the AE ABL and LR ABL , as well as the expectednegative trends for the WV ABL (and surface relative humidity, RH) and δABL , were observed. Relations of the lidar-derived aerosolproperties within the ABL and the surface in situ measurements of particulatematter with an aerodynamic diameter less than 10  µ m (PM 10 ) and less than 2.5  µ m (PM 2.5 ) measured by the Warsaw Regional Inspectoratefor Environmental Protection (WIOS) network, and the fine-to-coarse massratio (FCMR) were investigated. The FCMR and surface RH showed a positivecorrelation even at nighttime ( R of 0.71 for the MTL, 0.63 for the WML, and 0.6 for the NL), which generally lacked statisticallysignificant relations. A weak negative correlation of the FCMR and δABL (more pronounced at 532 nm at nighttime) and no casual relationbetween the FCMR and AE ABL were found. Most interestingly, distinctdifferences were observed for the morning transition layer (MTL) and thewell-mixed layer (WML). The MTL ranged up to 0.6–1 km, and wascharacterized by a lower AOD ABL( ), wetter conditions(RH 50–80 %), smaller particles (AE ABL of 1–2.2; FCMR from 0.5 to3), and a low LR ABL of between 20 and 40 sr. The WML ranged up to 1–2.5 kmand exhibited a higher AOD ABL (reaching up to 0.45), drier conditions(RH 25–60  %), larger particles (AE ABL of 0.8–1.7; FCMR of0.2–1.5), and a higher LR ABL of up to 90 sr.

atmospheric chemistry and physics

Interrelations between surface, boundary layer, and columnar aerosol properties derived in summer and early autumn over a continental urban site in Warsaw, Poland