On formation, growth and concentrations of air ions

Aerosol particles have effect on climate, visibility, air quality and human health. However, the strength of which aerosol particles affect our everyday life is not well described or entirely understood. Therefore, investigations of different processes and phenomena including e.g. primary particle sources, initial steps of secondary particle formation and growth, significance of charged particles in particle formation, as well as redistribution mechanisms in the atmosphere are required. In this work sources, sinks and concentrations of air ions (charged molecules, cluster and particles) were investigated directly by measuring air molecule ionising components (i.e. radon activity concentrations and external radiation dose rates) and charged particle size distributions, as well as based on literature review. The obtained results gave comprehensive and valuable picture of the spatial and temporal variation of the air ion sources, sinks and concentrations to use as input parameters in local and global scale climate models. Newly developed air ion spectrometers (Airel Ltd.) offered a possibility to investigate atmospheric (charged) particle formation and growth at sub-3 nm sizes. Therefore, new visual classification schemes for charged particle formation events were developed, and a newly developed particle growth rate method was tested with over one year dataset. These data analysis methods have been widely utilised by other researchers since introducing them. This thesis resulted interesting characteristics of atmospheric particle formation and growth: e.g. particle growth may sometimes be suppressed before detection limit (~ 3 nm) of traditional aerosol instruments, particle formation may take place during daytime as well as in the evening, growth rates of sub-3 nm particles were quite constant throughout the year while growth rates of larger particles (3-20 nm in diameter) were higher during summer compared to winter. These observations were thought to be a consequence of availability of condensing vapours. The observations of this thesis offered new understanding of the particle formation in the atmosphere. However, the role of ions in particle formation, which is not well understood with current knowledge, requires further research in future.Aerosolihiukkaset vaikuttavat ilmastoon suorasti sirottamalla ja absorboimalla auringon valoa, sekä epäsuorasti muodostamalla pilvipisaroita ja vaikuttamalla pilvien ominaisuuksiin. Tämän hetkisen tiedon mukaan aerosolihiukkasten vaikutus ilmastoon on viilentävä. Aerosolihiukkaset vaikuttavat myös ilman laatuun ja ihmisten terveyteen. On siis tarpeen tutkia mistä ja miten näitä hiukkasia muodostuu, kasvaa ja poistuu ilmakehässä, jotta voisimme paremmin arvioida aerosolihiukkasten vaikutusta jokapäiväiseen elämäämme. Tässä työssä saimme laajan käsityksen ilman ionien (varattuja molekyylejä, klustereita ja hiukkasia) lähteiden, nielujen ja pitoisuuksien ajallisesta ja paikallisesta vaihtelusta. Tässä työssä tutkittiin myös hiukkasten muodostumista ja kasvua ilmakehässä uusilla mittalaitteilla. Näin ollen työssä kehitettiin analyysimenetelmä varattujen hiukkasten muodostumistapahtumien luokitteluun, sekä testattiin hieman aiemmin kehitettyä hiukkasten kasvunopeuden määritysmenetelmää. Havainnot hiukkasmuodostuksesta ja kasvusta olivat erittäin mielenkiintoisa: esimerkiksi hiukkasten kasvu voi joskus pysähtyä ennen kuin (~ 3 nm) ne havaittaisiin perinteisillä mittalaitteilla, hiukkasmuodostus voi tapahtua niin päivällä kuin illallakin, alle 3-nm hiukkasten kasvu oli tasaista vuoden ympäri mutta 3-20-nm hiukkasten kasvu oli nopeampaa kesällä kuin talvella. Näiden havaintojen uskottiin johtuvan tiivistyvien höyryjen saatavuudesta ilmakehässä. Työssä kehiteltyjä ja käytettyjä analyysimenetelmiä on laajamittaisesti hyödynnetty niiden julkaisemisesta lähtien. Tehdyt havainnot tarjoavat laajan tietopaketin, jota voidaan hyödyntää ilmastomalleissa. Tulevaisuudessa kuitenkin tarvitaan lisää tutkimuksia ionien roolista hiukkasmuodostuksessa, joka ei nykytiedoilla ole täysin selvä, sekä mittaushavaintoja esimerkiksi hiukkasmuodostukseen ja kasvuun osallistuvista höyryistä

Atmospheric aerosol, gases, and meteorological parameters measured during the LAPSE-RATE campaign by the Finnish Meteorological Institute and Kansas State University

Small unmanned aerial systems (sUASs) are becoming very popular as affordable and reliable observation platforms. The Lower Atmospheric Process Studies at Elevation &ndash; a Remotely-piloted Aircraft Team Experiment (LAPSE-RATE), conducted in the San Luis Valley (SLV) of Colorado (USA) between 14 and 20&nbsp;July&nbsp;2018, gathered together numerous sUASs, remote-sensing equipment, and ground-based instrumentation. Flight teams from the Finnish Meteorological Institute (FMI) and the Kansas State University (KSU) co-operated during LAPSE-RATE to measure and investigate the properties of aerosol particles and gases at the surface and in the lower atmosphere. During LAPSE-RATE the deployed instrumentation operated reliably, resulting in an observational dataset described below in detail. Our observations included aerosol particle number concentrations and size distributions, concentrations of CO2 and water vapor, and meteorological parameters. All datasets have been uploaded to the Zenodo LAPSE-RATE community archive (https://zenodo.org/communities/lapse-rate/, last access: 21&nbsp;August&nbsp;2020). The dataset DOIs for FMI airborne measurements and surface measurements are available here: https://doi.org/10.5281/zenodo.3993996, Brus et al. (2020a), and those for KSU airborne measurements and surface measurements are available here: https://doi.org/10.5281/zenodo.3736772, Brus et al. (2020b). &nbsp;</p

Measurement report: Properties of aerosol and gases in the vertical profile during the LAPSE-RATE campaign

Unmanned aerial systems&nbsp;(UASs) are increasingly being used as observation platforms for atmospheric applications. The Lower Atmospheric Process Studies at Elevation &ndash; a Remotely-piloted Aircraft Team Experiment&nbsp;(LAPSE-RATE) in Alamosa, Colorado, USA, on 14&ndash;20&nbsp;July&nbsp;2018 investigated and validated different UASs, measurement sensors and setup configurations. Flight teams from the Finnish Meteorological Institute&nbsp;(FMI) and Kansas State University&nbsp;(KSU) participated in LAPSE-RATE to measure and investigate properties of aerosol particles and gases in the lower atmosphere. During the experiment, the performance of different UAS configurations were investigated and confirmed to operate reliably, resulting in a scientifically sound observational dataset. As an example, concentration of aerosols &ndash; including two new particle formation events, CO2 and water vapor, and meteorological parameters in the atmospheric vertical profile were measured during the short experiment. Such observations characterizing atmospheric phenomena of this specific environment would have not been possible in any other way and, thus, demonstrate the power of UASs as new, promising tools in atmospheric and environmental research. &nbsp;</p