Antti Manninen

Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols

Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.

BAECC: A Field Campaign to Elucidate the Impact of Biogenic Aerosols on Clouds and Climate

AbstractDuring Biogenic Aerosols—Effects on Clouds and Climate (BAECC), the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program deployed the Second ARM Mobile Facility (AMF2) to Hyytiala, Finland, for an 8-month intensive measurement campaign from February to September 2014. The primary research goal is to understand the role of biogenic aerosols in cloud formation. Hyytiala is host to the Station for Measuring Ecosystem–Atmosphere Relations II (SMEAR II), one of the world’s most comprehensive surface in situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions, and an extensive suite of parameters relevant to atmosphere–biosphere interactions continuously since 1996. Combining vertical profiles from AMF2 with surface-based in situ SMEAR II observations allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. Together with the inclusion of extensi...

Fluoroalcohol—XXII. Infrared, matrix infrared and Raman spectra and normal coordinate calculations for hexafluoro-2,2-propanediol and its deuterated analogues

Abstract Infrared spectra of the geminal diol (CF3)2C(OH)2 (hexafluoroacetone hydrate) and of its deuterated analogue (CF3)2C(OD)2 were recorded for the gaseous and liquid states and for argon and nitrogen matrices. Some i.r. data were obtained also for CF3(HO)C(OD)CF3 in argon. Raman spectra were recorded for hexafluoroacetone trihydrate and trideuterate. Vibrational assignments are made, and discussed with particular reference to OH and OD groups. Normal coordinate calculations were carried out to aid in the assignments of bands. The calculations indicated that the CF stretchings and bendings are strongly coupled with the skeletal modes, and thus the group frequency approximation is not good in the case of the compounds studied. This is true especially in the case of the CO bendings. The influence of association on the vibration bands was studied in detail by the matrix isolation technique. Monomeric hexafluoroacetone hydrate occurs obviously in the form of one conformer only, which is of C2v symmetry. The frequencies of the two νOH (νOD) fundamentals seems to be approximately equal. For the alcohol dimer we propose an eight-membered cyclic structure. The liquid monohydrate seems to consist mainly of dimers.

Atmospheric Boundary Layer Classification With Doppler Lidar

We present a method using Doppler lidar data for identifying the main sources of turbulent mixing within the atmospheric boundary layer. The method identifies the presence of turbulence and then assigns a turbulent source by combining several lidar quantities: attenuated backscatter coefficient, vertical velocity skewness, dissipation rate of turbulent kinetic energy, and vector wind shear. Both buoyancy‐driven and shear‐driven situations are identified, and the method operates in both clear‐sky and cloud‐topped conditions, with some reservations in precipitation. To capture the full seasonal cycle, the classification method was applied to more than 1 year of data from two sites, Hyytiala, Finland, and Julich, Germany. Analysis showed seasonal variation in the diurnal cycle at both sites; a clear diurnal cycle was observed in spring, summer, and autumn seasons, but due to their respective latitudes, a weaker cycle in winter at Julich, and almost non‐existent at Hyytiala. Additionally, there are significant contributions from sources other than convective mixing, with cloud‐driven mixing being observed even within the first 500 m above ground. Also evident is the considerable amount of nocturnal mixing within the lowest 500 m at both sites, especially during the winter. The presence of a low‐level jet was often detected when sources of nocturnal mixing were diagnosed as wind shear. The classification scheme and the climatology extracted from the classification provide insight into the processes responsible for mixing within the atmospheric boundary layer, how variable in space and time these can be, and how they vary with location.