Sander Mirme

An Instrumental Comparison of Mobility and Mass Measurements of Atmospheric Small Ions

Ambient, naturally charged small ions (<2000 Da) were measured in Hyytiälä, Finland, with a mass spectrometer (atmospheric pressure interface time-of-flight, APi-TOF) and two mobility spectrometers (air ion spectrometer, AIS, and balanced scanning mobility analyzer, BSMA). To compare these different instrument types, a mass/mobility conversion and instrumental transfer functions are required to convert high-resolution mass spectra measured by the APi-TOF into low-resolution mobility spectra measured by the AIS and BSMA. A modified version of the Stokes-Millikan equation was used to convert between mass and mobility. Comparison of APi-TOF and BSMA results showed good agreement, especially for sizes above 200 Da (Pearsons R = 0.7–0.9). Below this size, agreement was fair, and broadening BSMA transfer functions improved the correlation. To achieve equally good agreement between APi-TOF and AIS, AIS results needed to be shifted by 1–1.5 mobility channels. The most likely cause was incorrect sizing in the AIS. In summary, the mass and mobility spectrometers complement each other, with the APi-TOF giving superior chemical information, limited to relatively small ions (<2.5 nm diameter), whereas the mobility spectrometers are better suited for quantitative concentration measurements up to 40 nm. The BSMA and AIS were used to infer a transmission function for the APi-TOF, making it possible to give quantitative estimates of the concentrations of detected chemical ions.

SMEAR Estonia: Perspectives of a large-scale forest ecosystem – atmosphere research infrastructure

Abstract Establishment of the SMEAR Estonia at a hemiboreal mixed deciduous broad-leaved-evergreen needle-leaved forest at Järvselja, South-Eastern Estonia, has strongly enhanced the possibilities for national and international cooperation in the fields of forest ecosystem – atmosphere research and impacts of climatic changes on forest ecosystems, atmospheric trace gases, aerosols and air ions. The station provides a multitude of comprehensive continuously measured data covering key climatic and atmospheric characteristics (state and dynamics of solar radiation, trace gases, aerosols and air ions, meteorological parameters) and forest ecosystem traits (net primary productivity, individual tree growth, gas-exchange characteristics, soil variables). The station follows a multidisciplinary and multiscale approach covering processes in spatial dimensions ranging from nanometres to several hundred square kilometres, being thus able to significantly contribute to worldwide measurement networks and the SMEAR network. Here we present an overview of the station, its data produced and we envision future developments towards sustainable research and development of the large-scale scientific infrastructure SMEAR Estonia.

Does the onset of new particle formation occur in the planetary boundary layer

The planetary boundary layer (PBL) is chemically and physically the most active and complex part of the atmosphere as it has high loading of both aerosols and gaseous precursors. To detect directly the first steps of new particle formation in the atmosphere, we are measuring chemical and physical processes within the PBL (altitudes up to 1 km). Our study consists of both airborne Zeppelin measurements and ground based in-situ measurements. Using Zeppelin, we measured vertical profiles of aerosol particles and chemical compounds during the growth of the PBL from sunrise until noon. These measurements are part of the PEGASOS project. It aims to quantify the magnitude of regional to global feedbacks between the atmospheric chemistry and physics, and quantify the changing climate. The Zeppelin flights are observing radicals, tarce gases, and aerosols inside the atmospheric layers up to 1 km height over Europe. The main nucleation campaigns are performed in Po Valley, Northern Italy (summer 2012), and Hyytiala...

Reversible Work of the Heterogeneous Formation of an Embryo of a New Phase on a Spherical Charged Conductor Within a Uniform Multicomponent Macroscopic Mother Phase

A thermodynamically consistent formalism is applied to calculate the reversible work needed to form an embryo of a new phase on a charged insoluble conducting sphere within a uniform macroscopic mother phase. An approximate procedure for the calculation of formation free energy of a spherical cap like embryo is described.

Atmospheric electricity and aerosol-cloud interactions in earth’s atmosphere

Firstly, atmospheric ions play an important role in the fair weather electricity in Earth’s atmosphere. Small ions, or charged molecular clusters, carry electric currents in the atmosphere. These small ions are continuously present, and their lifetime in lower atmosphere is about one minute. It’s essential to find out a connection between the production rate of cluster ions, ion-ion recombination, and ion-aerosol attachment, and their ambient concentrations, in order to understand electrical properties of air. Secondly, atmospheric ions are important for Earth’s climate, due to their potential role in secondary aerosol formation, which can lead to increased number of cloud condensation nuclei (CCN), which in turn can change the cloud properties. Our aim is to quantify the connections between these two important roles of air ions based on field observations.