Vertical profiles of sub-3 nm particles over the boreal forest

Leino, Katri; Lampilahti, Janne; Poutanen, Pyry; Väänänen, Riikka; Manninen, Antti; Mazon, Stephany Buenrostro; Dada, Lubna; Franck, Anna; Wimmer, Daniela; Aalto, Pasi; Ahonen, Lauri; Enroth, Joonas; Kangasluoma, Juha; Keronen, Petri; Korhonen, Frans; Laakso, H.; Matilainen, Teemu; Siivola, Erkki; Manninen, Hanna E.; Lehtipalo, Katrianne; Kerminen, Veli‐Matti; Petäj̈ä, Tuukka; Kulmala, Markku

doi:10.5194/acp-2018-605

Cited by 4 publications

(6 citation statements)

References 24 publications

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“…On the other hand, if the 2-4 nm ions are present but they do not grow to form 7-25 nm particles, the time period is classified as an ion burst (IB). Moreover, if 2-4 nm ions are not present, but we observe an increase in the particles, this leads to the assumption that the NPF event did not occur at the measurement location but was carried horizontally or vertically to our site (Leino et al, 2018). The latter has been previously described as a tail event (Buenrostro Mazon et al, 2009) or a TE.…”

Section: Event Classification Decision Treementioning

confidence: 76%

“…The type TE, or transported events (also known as tail events by Buenrostro Mazon et al, 2009), are events with an undetected beginning as it does not occur at the immediate vicinity of our measurement site. Such events could have been initiated outside our measurement site and transported to Hyytiälä (Leino et al, 2018). The aforementioned hypotheses could explain the observation that TE typically occur at around midday or later in the afternoon, while REs tend to occur concurrent with sunrise.…”

Section: Event Classificationmentioning

confidence: 93%

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Refined classification and characterization of atmospheric new-particle formation events using air ions

et al. 2018

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Abstract. Atmospheric new-particle formation (NPF) is a worldwide-observed phenomenon that affects the human health and the global climate. With a growing network of global atmospheric measurement stations, efforts towards investigating NPF have increased. In this study, we present an automated method to classify days into four categories including NPF events, non-events and two classes in between, which then ensures reproducibility and minimizes the hours spent on manual classification. We applied our automated method to 10 years of data collected at the SMEAR II measurement station in Hyytiälä, southern Finland using a Neutral cluster and Air Ion Spectrometer (NAIS). In contrast to the traditionally applied classification methods, which categorize days into events and non-events and ambiguous days as undefined days, our method is able to classify the undefined days as it accesses the initial steps of NPF at sub-3 nm sizes. Our results show that, on ∼24 % of the days in Hyytiälä, a regional NPF event occurred and was characterized by nice weather and favourable conditions such as a clear sky and low condensation sink. Another class found in Hyytiälä is the transported event class, which seems to be NPF carried horizontally or vertically to our measurement location and it occurred on 17 % of the total studied days. Additionally, we found that an ion burst, wherein the ions apparently fail to grow to larger sizes, occurred on 18 % of the days in Hyytiälä. The transported events and ion bursts were characterized by less favourable ambient conditions than regional NPF events and thus experienced interrupted particle formation or growth. Non-events occurred on 41 % of the days and were characterized by complete cloud cover and high relative humidity. Moreover, for regional NPF events occurring at the measurement site, the method identifies the start time, peak time and end time, which helps us focus on variables within an exact time window to better understand NPF at a process level. Our automated method can be modified to work in other measurement locations where NPF is observed.

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Section: Event Classification Decision Treementioning

confidence: 76%

Section: Event Classificationmentioning

confidence: 93%

Refined classification and characterization of atmospheric new-particle formation events using air ions

et al. 2018

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“…The measurement setups changed slightly over the years. Detailed descriptions of the setups on board can be found in previous studies (Leino et al, 2019;Schobesberger et al, 2013;Väänänen et al, 2016).…”

Section: Airborne Measurementsmentioning

confidence: 99%

“…This might be because in the more polluted environments there are high enough concentrations of precursor vapors from anthropogenic sources that NPF can be initiated in the morning inversion and/or within the bulk of the RL. Interestingly though, observations from Hyytiälä using a small instrumented airplane have frequently found nucleation mode particle layers above the ML at a much higher altitude range of ∼ 1500-2800 m above ground and the explanation for these layers is not clear (Leino et al, 2019;Schobesberger et al, 2013;Väänänen et al, 2016). For example, Väänänen et al (2016) found that for the 2013-2014 airborne measurement campaigns 16/36 (∼ 44 %) profiles showed an elevated sub-25 nm particle layer.…”

Section: Introductionmentioning

confidence: 99%

Aerosol particle formation in the upper residual layer

et al. 2021

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Abstract. According to current estimates, atmospheric new particle formation (NPF) produces a large fraction of aerosol particles and cloud condensation nuclei in the Earth's atmosphere, which have implications for health and climate. Despite recent advances, atmospheric NPF is still insufficiently understood in the lower troposphere, especially above the mixed layer (ML). This paper presents new results from co-located airborne and ground-based measurements in a boreal forest environment, showing that many NPF events (∼42 %) appear to start in the topmost part of the residual layer (RL). The freshly formed particles may be entrained into the growing mixed layer (ML) where they continue to grow in size, similar to the aerosol particles formed within the ML. The results suggest that in the boreal forest environment, NPF in the upper RL has an important contribution to the aerosol load in the boundary layer (BL).

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“…The maximum altitude was about 3800 m above sea level. More details about the set up and measurements can be found in Schobesberger et al (2013), Leino et al (2019), Lampilahti et al (2020).…”

Section: Airborne In Situ Measurementsmentioning

confidence: 99%

Evaluation of convective boundary layer height estimates using radars operating at different frequency bands

Franck

Moisseev

Vakkari

et al. 2021

Preprint

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Abstract. Knowledge of atmospheric boundary layer state and evolution is important for understanding air pollution and low level cloud development, among other things. There are a number of instruments and methods that are currently used to estimate boundary layer height (BLH). However, no single instrument is capable of providing BLH measurements in all weather conditions. We proposed a method to derive a daytime convective BLH using radar observations and investigated the consistency of these retrievals between different radars. We utilized data from three vertically-pointing radars that are available at the measurement station in Southern Finland: the C-band (5 GHz), Ka-band (35 GHz) and W-band (94 GHz). The Ka- or W- band cloud radars are an integral part of cloud profiling stations of pan-European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Our method will be utilized at ACTRIS stations to serve as an additional estimate of the BLH during summer months. During this period, echoes from insects and Bragg scatter are often recorded by radars. To retrieve a BLH, we suggested a mechanism to separate small insects that follow air motion and independently flying insects that works for all analyzed frequency bands. At the lower frequency (the C-band) insect scattering was separated from Bragg scattering using a combination of radar reflectivity factor and linear depolarization ratio. Retrieved values of the BLH from all radars are in a good agreement when compared to the BLH obtained with the co-located lidar and reanalysis dataset. Our method showed some underestimation of the BLH after night-time heavy precipitation yet demonstrated a potential to serve as a reliable method to obtain a BLH during clear-sky days. Additionally, the entrainment zone was observed by the C-band radar above the CBL in a form of a Bragg scatter layer. Aircraft observations of vertical profiles of potential temperature and water vapor mixing ratio, collected in the vicinity of the radar, demonstrated some agreement with the Bragg scatter layer.

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Vertical profiles of sub-3 nm particles over the boreal forest

Cited by 4 publications

References 24 publications

Refined classification and characterization of atmospheric new-particle formation events using air ions

Refined classification and characterization of atmospheric new-particle formation events using air ions

Aerosol particle formation in the upper residual layer

Evaluation of convective boundary layer height estimates using radars operating at different frequency bands

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