M. Komppula

Diurnal and annual characteristics of particle mass and number concentrations in urban, rural and Arctic environments in Finland

Abstract In order to be able to detect annual and diurnal variation the nucleation, Aitken and accumulation mode aerosol number concentrations were investigated. In this study particulate matter and aerosol number concentrations based on three years (1999–2001) measurements in four different places, Helsinki, Hyytiala, Pallas and Varrio in Finland were utilized. Mean PM10 concentration was found to be in urban, urban background, disturbed rural and rural conditions 18.7, 15.3, 10.2 and 6.9 μg m −3 . PM2.5 concentrations in urban, urban background and rural conditions were 9.6, 8.2 and 5.8 μg m −3 . PM1 concentration in rural area were 4.1 μg m −3 . Total number concentrations between 10 and 500 nm in urban, rural and arctic background were 16660, 2110 and about 920 cm −3 , respectively. Annual cycle of different particle sizes was also investigated. Particle mass was found to have maximum during the spring and autumn. Nucleation mode particle concentrations had their maximum both in urban and rural conditions in spring and autumn. For Aitken mode a similar variation was found. Accumulation mode particles were found to have the highest concentrations during summer and the lowest concentrations during winter. In urban conditions local sources drive over natural variability, but a natural cycle can still be seen. Diurnal variation was found to be associated with traffic in urban conditions. In rural conditions, diurnal variation of nucleation mode particles were connected to new particle formation. It was also found, that there is no correlation between ultrafine ( nm ) and larger (>90 nm ) particles.

Aerosol size distribution measurements at four Nordic field stations : identification, analysis and trajectory analysis of new particle formation bursts

We analyzed aerosol size distributions from the Finnish measuring stations at Hyytiälä, Värriö and Pallas and the Swedish station at Aspvreten over a period of several years.We identified occurrences of new particle formation bursts and obtained characteristics for the bursts from the size distribution data. In addition, we analyzed the directions from which air masses leading to new particle formation arrived.We found that new particle formation occurs over the whole area covered by the measurement stations. The Northern Atlantic is dominating as a source for air leading to new particle formation at all of the analyzed stations. The formation occurrence had a similar annual variation at all the stations, with peaks in springtime and autumn and minima in winter and summer. The ratio of event days to non-event days had a North-South dependence, with northern stations having lower event ratios. Particle growth rates ranged from 0.5 to 15 nm/h, with the mean growth rate being slightly higher at the southern stations. Southern stations also had a stronger particle source, on average 0.5 cm-3 s-1, compared to the northern stations (0.1 cm-3 s-1). Based on our analysis, it is evident that new particle formation occurs often in whole Nordic boreal forest area when air is transported from the North Atlantic, and that the same process or processes are very probably responsible for the formation over the whole area.

Portable Raman Lidar Polly XT for Automated Profiling of Aerosol Backscatter, Extinction, and Depolarization

Two versions of the portable aerosol Raman lidar system (Polly) are presented. First, the two-channel prototype is depicted. It has been developed for the independent and simultaneous determination of particle backscatter and extinction coefficient profiles at 532 nm. Second, the 3 1 2 Raman lidar Polly XT (3 1 2: three backscatter and two extinction coefficients), the second generation of Polly, is described. The extended capabilities of Polly XT are due to the simultaneous emission of light with three wavelengths, more laser power, a larger main receiver mirror, and seven receiver channels. These systems are completely remotely controlled and all measurements are performed automatically. The collected data are transferred to a home server via the Internet and are displayed on a Web page. This paper describes the details of the optical setup, the housekeeping of the systems, and the used data retrieval routines. A measurement example taken close to Manaus, Brazil, on 15 August 2008 shows the capabilities of Polly XT .

Continuous measurements of optical properties of atmospheric aerosols in Mukteshwar, northern India

[1] Particulate pollution of mainly anthropogenic origin is a widely spread phenomenon in southern Asia, influencing climate and causing adverse health effects on humans. In this paper, we analyze continuous measurements of aerosol scattering and absorption properties that were conducted in Mukteshwar, a remote site in the Himalayan Mountains in northern India, during September 2005―September 2007. While aerosol concentrations were somewhat lower than those measured closer to urban areas in India, some optical parameters had a noticeable resemblance to those measured elsewhere in India. The average value of the measured single-scattering albedo was 0.81 at 525 nm, being indicative of a substantial amount of absorbing material. Annually, there were two periods when aerosol scattering and absorption coefficients were relatively low. These were the rainy season during July and August and the winter months December and January when particulate pollution seemed to reside partly below the altitude of the measurement station. During December and January, local cooking and warming of houses by biomass burning, normally not visible in the data, became evident yet weak sources of absorbing material.

Annual and interannual variation in boreal forest aerosol particle number and volume concentration and their connection to particle formation

We investigated size-resolved submicrometre aerosol particle number and volume concentration time series as well as aerosol dynamic parameters derived from Differential Mobility Particle Sizer (DMPS) measurements at five background stations in the Nordic boreal forest area. The stations in question were Aspvreten, Hyytiälä and Utö in southern Finland and Sweden, and Värriö and Pallas in the Finnish Lapland. The objective of our investigation was to identify and quantify annual and interannual variation observable in the time series. We found that the total number and mass concentrations were much lower at the Lapland stations than at the southern stations and that the total particle number was strongly correlated to particle formation event frequency. The annual total number concentration followed the annual distribution of particle formation events at the southern stations but much less clearly at the Lapland stations. The volume concentration was highest during summer, in line with higher condensation growth rates; this is in line with the assumption that a large part of the particle volume is produced by oxidized plant emissions. The decrease of sulphate emissions in Europe was not visible in our data set. Aerosol dynamic parameters such as condensation sink, condensation sink diameter and the power law exponent linking coagulation losses and condensation sink are presented to characterize the submicron Nordic background aerosol.

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...

Long-term measurements of cloud droplet concentrations and aerosol–cloud interactions in continental boundary layer clouds

The effects of aerosol on cloud droplet effective radius (R eff), cloud optical thickness and cloud droplet number concentration (N d) are analysed both from long-term direct ground-based in situ measurements conducted at the Puijo measurement station in Eastern Finland and from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Terra and Aqua satellites. The mean in situ N d during the period of study was 217 cm−3, while the MODIS-based N d was 171 cm−3. The absolute values, and the dependence of both N d observations on the measured aerosol number concentration in the accumulation mode (N acc), are quite similar. In both data sets N d is clearly dependent on N acc, for N acc values lower than approximately 450 cm−3. Also, the values of the aerosol–cloud-interaction parameter [ACI=(1/3)*d ln(N d)/d ln(N acc)] are quite similar for N acc<400 cm−3 with values of 0.16 and 0.14 from in situ and MODIS measurements, respectively. With higher N acc (>450 cm−3) N d increases only slowly. Similarly, the effect of aerosol on MODIS-retrieved R eff is visible only at low N acc values. In a sub set of data, the cloud and aerosol properties were measured simultaneously. For that data the comparison between MODIS-derived N d and directly measured N d, or the cloud droplet number concentration estimated from N acc values (N d,p), shows a correlation, which is greatly improved after careful screening using a ceilometer to make sure that only single cloud layers existed. This suggests that such determination of the number of cloud layers is very important when trying to match ground-based measurements to MODIS measurements.

Aerosol Chemical Composition in Cloud Events by High Resolution Time-of-Flight Aerosol Mass Spectrometry

This study presents results of direct observations of aerosol chemical composition in clouds. A high-resolution time-of-flight aerosol mass spectrometer was used to make measurements of cloud interstitial particles (INT) and mixed cloud interstitial and droplet residual particles (TOT). The differences between these two are the cloud droplet residuals (RES). Positive matrix factorization analysis of high-resolution mass spectral data sets and theoretical calculations were performed to yield distributions of chemical composition of the INT and RES particles. We observed that less oxidized hydrocarbon-like organic aerosols (HOA) were mainly distributed into the INT particles, whereas more oxidized low-volatile oxygenated OA (LVOOA) mainly in the RES particles. Nitrates existed as organic nitrate and in chemical form of NH(4)NO(3). Organic nitrates accounted for 45% of total nitrates in the INT particles, in clear contrast to 26% in the RES particles. Meanwhile, sulfates coexist in forms of acidic NH(4)HSO(4) and neutralized (NH(4))(2)SO(4). Acidic sulfate made up 64.8% of total sulfates in the INT particles, much higher than 10.7% in the RES particles. The results indicate a possible joint effect of activation ability of aerosol particles, cloud processing, and particle size effects on cloud formation.

Atmospheric new particle formation at Uto, Baltic Sea 2003-2005

Nearly 3 yr (March 2003–December 2005) of continuous particle number size distribution measurements have been conducted at the island of Utö in the Baltic Sea. The measured particle size range was from 7 to 530 nm. During the measurement period, a total of 103 regional new-particle formation events were observed. The characteristics of the nucleation events at Utö were similar to those reported in the literature in other Nordic sites, though measured condensation sinks were rather high (geometric mean of 3.8 × 10-3 s-1) during event days. Clear evidence was found that new particles nucleate regionally near Utö, rather than are transported from greater distances. However, the Baltic Sea seems to have an inhibiting effect on new-particle formation. The boreal forest areas in the continental Finland were found to have an enhancing effect on the nucleation probability in Utö, suggesting that at least some of the precursor gases for nucleation and/or condensational growth of particles originate from these forests. In addition to regional new-particle formation events, a total of 94 local events were observed in Utö. These are short-lived events with a small footprint area, and can at least partly be tracked down to the emissions of ship traffic operating at Utö.

Continuous measurements of aerosol properties at the Baltic Sea

Thirty months (March 2003–October 2005) of aerosol size distributions, trace gas and meteorological parameter measurements have been analysed at a background station in Baltic Sea. Log-normal modes have been fitted to the size distributions and a source region analysis using 120 h back trajectories has been accomplished. Seasonal and air mass influences have been studied and compared to other measurement sites. Only weak impacts of meteorological conditions have been found. New particle formation events were observed, but less frequently compared to continental sites, which is concluded being related to the lack of precursor gas sources close to the station and a higher condensation sink. The northeast Atlantic was recognized as an important source of particles in the Aitken mode. Especially in spring and summer, probably primary biogenic particles contribute largely to the particle number concentration. Source regions of the submicron aerosol are strongly dependant of the particle size and so is the contribution to the total number or mass concentration. For this reason, a consideration of the total number or mass concentration was identified not being sufficient in order to describe source areas of aerosol particles.