Outi Meinander - Academia.edu (original) (raw)

Papers by Outi Meinander

The manuscript is divided into two parts. First it presents the bipolar UV albedo monitoring stat... more The manuscript is divided into two parts. First it presents the bipolar UV albedo monitoring station at Sodankylä and Marambio. It explains in full details the setup and the challenges operating these polar stations. The second part tries to give an extensive overview over albedo measurements, analysis and modeling of these kinds of data. The later chapters are defined as literature review by the authors.

Optical Engineering, 2003

The occurrence of spikes in Brewer UV spectra is studied. Use is made of continuous measurement d... more The occurrence of spikes in Brewer UV spectra is studied. Use is made of continuous measurement data over several years, comprising more than 90,000 spectra, from one single-monochromator and two double-monochromator Brewers. It is shown that the double monochromators, especially, may suffer from more than 200 spikes per ϳ5000 annual spectra. The spikes are not always randomly distributed over the wavelength range. The single monochromator is found to have an annual average of only 36 spikes above 300 nm, but it is noted that there were a significant number of spikes at shorter wavelengths, indicating possible bias in the stray light correction unless taken into consideration. The error caused by noncorrected spikes varies greatly from case to case. In an intensive study of 150 spectra measured during one summer week, the effect of one moderate-size spike was found to be more than 5% on a DNA action dose rate and close to 1% on a DNA action daily dose. When high accuracy of in situ UV measurements is required, our results suggest a need to remove spikes from the spectra. A simple statistical approach is employed. The method is applicable to any singleor double-monochromator Brewer spectroradiometer. However, under rapidly changing cloudiness it can be difficult to distinguish between noise spikes and the variation in irradiance due to changes in the state of the sky. Our data show that ancillary radiation measurements may be necessary to interpret the data correctly.

EGU General Assembly Conference Abstracts, Apr 1, 2018

<p>The Sahara Desert is the largest source of dust worldwide. Finland, north of 60 ... more <p>The Sahara Desert is the largest source of dust worldwide. Finland, north of 60 <sup>o</sup>N, is annually affected by long-range transported Saharan dust, which is most often observed as red sunrises and sunsets. Observations on dust deposition on ground are rare. On 23 February 2021, Saharan dust was transported and deposited in the southern part of Finland, reaching up a long way inland. At the time, the ground was covered with snow, and therefore the dust deposition was more easily detectable. The deposition was accompanied by freezing rain in the most southern part of the country, and snowfall further north.</p><p>Samples of dust in snow were collected by citizens and forwarded to the Finnish Meteorological Institute (FMI) following our researchers’ guidelines advertised in social media. Most samples were a solid residue from 2 dl of superficial snow, that had been either melted and filtered using coffee filters, evaporated on an aluminum foil, or decanted with the help of containers. In addition, fresh samples were collected for reference and were stored in a freezer for further analysis. Samples were received from over 500 locations and each of these contained one or more filtered, evaporated, or decanted dust samples. Dust was observed as far north as Vaasa and Kuopio (~63 <sup>o</sup>N).</p><p>The event was forecasted by the operational SILAM global atmospheric-composition suite of FMI (http://silam.fmi.fi) five days in advance. The suite is driven by the meteorology from the Integrated Forecasting System (IFS) model of the European Centre for Medium-Range Weather Forecast (ECMWF). According to the model results, the near-surface concentrations of desert dust in Finland on 23.02.2021 were negligible, while the total column reached 100-200 µg/m<sup>2</sup>, and optical column thickness in some places was up to 0.2, which is enough to be visible. The scavenging of dust from aloft layers resulted in substantial contamination of snow. Light microscopy results indicate the presence of quartz particles in the range 5-15 µm compatible with desert dust. Processed samples from the Askola region (~60 °N), about 20 km north from the southern coastline, show depositions of ~1100 mg/m<sup>2</sup>. Dust deposition amounts may vary greatly depending on the location and precipitation amounts. Our work also includes ice nucleation experiments, determination of particle size distributions, investigations on organic compounds, microplastics and microorganisms. The citizen science nature of the project will be used to promote and disseminate FMI’s research on aerosols through a specific outreach programme. Our study aims at producing information on latitudinal Saharan dust transport, as well as on deposition particle shapes, size distributions and ice nucleation ability of the particles detected in Finland, through the analysis of the collected samples.</p><p> </p><p> </p>

GUV radiometer data from Marambio station for the period March 2017 - May 2019. UV-B and UV-A dai... more GUV radiometer data from Marambio station for the period March 2017 - May 2019. UV-B and UV-A daily maximum irradiances and dailydoses. Daily noon UV index and total column ozone. Daily maximum irradiances at 555 nm (VIS) and daily maximum of photosynthetically active radiation. If you use the data, please contact Kaisa Lakkala, Finnish Meteorological Institute.

Boreal Environment Research, 2016

Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the ass... more Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow with higher soot content, and it was observed immediately following soot deposition. Compared with a previous laboratory study the effects of soot on the snow were not as prominent in outdoor conditions. During snowmelt, about 50% of the originally deposited soot particles were observed to remain at the snow surface. More detailed experiments are however needed to better explain soot’s effect on snow and to better quantify this effect. Our albedo versus soot parameterization agreed relatively well with previously published relationships. (Less)

Atmosphere, 2020

Black carbon (BC), organic carbon (OC), and total carbon (TC) in snow are important for their cli... more Black carbon (BC), organic carbon (OC), and total carbon (TC) in snow are important for their climatic and cryospheric effects. They are also part of the global carbon cycle. Atmospheric black and organic carbon (including brown carbon) may deposit and darken snow surfaces. Currently, there are no standardized methods for sampling, filtering, and analysis protocols to detect carbon in snow. Here, we describe our current methods and protocols to detect carbon in seasonal snow using the OCEC thermal optical method, a European standard for atmospheric elemental carbon (EC). We analyzed snow collected within and around the urban background SMEARIII (Station for Measuring Ecosystem-Atmosphere Relations) at Kumpula (60° N) and the Arctic GAW (Global Atmospheric Watch) station at Sodankylä (67° N). The median BC, OC, and TC in snow samples (ntot = 30) in Kumpula were 1118, 5279, and 6396 ppb, and in Sodankylä, they were 19, 1751, and 629 ppb. Laboratory experiments showed that error due to...

<p&amp... more <p>Seemingly small amounts of black carbon (BC) in snow, of the order of 10–100 parts per billion by mass (ppb), have been shown to decrease its albedo by 1–5 %. Due to the albedo-feedback mechanism, surface darkening accelerates snow and ice melt and contributes to Arctic warming.</p><p>Here we present the most recent procedures we use for sampling, filtering and analysis of Arctic snow, ice and water samples, to determine their black carbon (BC), organic carbon (OC) and total carbon (TC) contents. For the purpose, we apply the OCEC analyzer of the Finnish Meteorological Institute’s aerosol laboratory, Helsinki, Finland (60°12 N). Particles are collected on a quarz-fiber filter and subjected to different temperature ramps following the protocols (NIOSH-870, EUSAAR2, or IMPROVE). Pyrolysis correction is by laser transmittance. Light transmittance through the filter is monitored during the collection phase to quantify BC. The OCEC thermal-optical method is the current European standard method for determination of atmospheric BC.  </p><p>Our Arctic samples include surface snow and snow profile samples collected north of the Arctic Circle at the Finnish Meteorological Institute Arctic Space Center in Sodankylä, Finland (67◦37 N, 26◦63 E), which is also a World Meteorological Institute’s Global Atmospheric Watch station (WMO GAW). In addition, samples from H2020 EU-Interact stations of Faroes FINI, Iceland Sudurnes and UK Cairngorms, and elsewhere from Iceland and Finland, including Helsinki Kumpula SMEAR-III station (60°12 N, 24°57 E, Station for Measuring Ecosystem-Atmosphere Relations, https://www.atm.helsinki.fi/SMEAR/index.php/smear-iii) and the most northern research catchment area of Pallas (68°N, about 130 km north from the Arctic Circle, https://blogs.egu.eu/divisions/hs/2019/06/19/featured-catchment-series-pallas/), have been sampled and analyzed. The BC concentrations have been detected to vary according to the origin of the air masses and as a result of the seasonal snow melt process.</p><p><em>Acknowledgements. We gratefully acknowledge support from the EU-Interact-BLACK-project Black Carbon in snow and water (H2020 Grant Agreement No. 730938); the Academy of Finland NABCEA-project of Novel Assessment of Black Carbon in the Eurasian Arctic (No. 296302), Ministry for Foreign Affairs of Finland IBA-project Black Carbon in the Arctic and significance compared to dust sources (No. PC0TQ4BT-25); the Academy of Finland Center of Excellence program The Centre of Excellence in Atmospheric Science - From Molecular and Biological processes to The Global Climate (No. 272041), and The Nordic Center of Excellence CRAICC Cryosphere–Atmosphere Interactions in a Changing Arctic…

Frontiers in Earth Science, 2019

Editorial on the Research Topic Atmosphere-Cryosphere Interaction in the Arctic, at High Latitude... more Editorial on the Research Topic Atmosphere-Cryosphere Interaction in the Arctic, at High Latitudes and Mountains With Focus on Transport, Deposition, and Effects of Dust, Black Carbon, and Other Aerosols Atmosphere and cryosphere are closely linked and therefore need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in recent decades, while such areas have been more fragile and less adaptable to global climate change (Boy et al., 2019). Atmospheric air pollutants, in particular black carbon (BC) and dust, are deposited on clean snow, land ice or sea ice surfaces, and decrease their albedo. Due to albedo-feedback, snow and ice are melting faster and seasonal snow cover earlier. Impacts of ice loss include reduction in the Earth's albedo and, as a positive feedback, this leads to further warming (Flanner et al., 2007), as for example in the Arctic region. Albedo is wavelength dependent and typically very high for clean snow, and decreases as a function of snow age, snow grain size, and impurity content (e.g., Warren and Wiscombe, 1980; Aoki et al., 2000; Gardner and Sharp, 2010). It is estimated that Arctic snow albedo is reduced primarily due to BC, but other impurities can also contribute to absorption, such as organic or brown carbon (Doherty et al., 2010). Surface albedo feedback has been found as the second main contributor to Arctic amplification (Pithan and Mauritsen, 2014), and BC deposition to snow and ice can strongly contribute to the darkening via black-carbon-on-snow forcing (Bond et al., 2013). The role of BC in snow and ice has been widely investigated, and detailed scientific assessments have been presented in Bond et al. (2013), Intergovernmental Panel on Climate Change (IPCC) (2013), and AMAP (2015). Seemingly small amounts of BC in snow, of the order of 10-100 parts per billion by mass (ppb), have shown to decrease its albedo by 1-5% (Hadley and Kirchstetter, 2012). A reduction in snow-surface density due to light absorbing impurities has been documented (Meinander et al., 2014; Skiles and Painter, 2017), and BC has also been suggested as disturbing the water holding capacity of snow (Meinander et al., 2014). Dust has been identified as reducing snow albedo in many parts of the world, for example the Chilean Andes,

A ground-based ultraviolet (GUV) multi-filter radiometer was set up at Marambio, 64 • S, 56 • W, ... more A ground-based ultraviolet (GUV) multi-filter radiometer was set up at Marambio, 64 • S, 56 • W, Antarctica, in 2017. The instrument continuously measures ultraviolet (UV) radiation, visible (VIS) radiation and photosynthetically active radiation (PAR). The measurements are designed for providing high-quality longterm time series that can be used to assess the impact of global climate change in the Antarctic region. The quality assurance includes regular absolute calibrations and solar comparisons performed at Marambio and at Sodankylä, Finland. The measurements continue observations at Marambio that were performed with (Norwegian Institute for Air Research UV Radiometer (NILU-UV) radiometers between 2000 and 2010 as part of the Antarctic NILU-UV network. These measurements are ideally suited for assessing the effects of the ongoing stratospheric ozone recovery on the ecosystem, as the data products include information on radiation at various wavelengths ranging from UV to VIS so that changes on biologically effective radiation due to ozone can be separated from those due to other factors. Data products include total ozone, photosynthetically active radiation (PAR), visible (VIS) radiation at 555 nm, UV index, UV irradiance at 5 channels, UVB and UVA dose rate and daily dose, and biologically weighted UV dose rate and daily dose, calculated with 10 different action spectra. The data from the last 5 d and the daily maximum UV index time series are plotted and updated daily on the following web

Atmospheric Chemistry and Physics Discussions, 2018

The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic C... more The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, was the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic Region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual Centre with the objectives to identify and quantify the major processes controlling Arctic warming and related feedback mechanisms, to outline strategies to mitigate Arctic warming and to develop Nordic Earth System modelling with a focus on the short-lived climate forcers (SLCF), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special-issue of the journal Atmospheric Chemistry and Physics. This manuscript presents an overview on the main scientific topics investigated in the Centre and provides the reader a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Facing the vast amount of outcomes we are not claiming to cover all results from CRAICC in this manuscript but concentrate here on the main results which are related to the feedback loops in the climate change-cryosphere interaction scheme affecting the Arctic amplification. 1 Introduction Near-surface climate warming in the Arctic has proceeded at approximately twice the global average rate since 1980. This extraordinary rate of warming has been recognized since the late 1990s (Serreze et al., 2000) and has accelerated even since then (Bekryaev et al., 2010), leading to extreme events in 2016 when October-December temperatures in large parts of the Arctic were more than 5˚C above normal and daily anomalies exceeded 16˚C in many locations

AIP Conference Proceedings, 2017

At Sodankylä (67 • N), spectra of solar ultraviolet radiation (UVR) have been measured with a Bre... more At Sodankylä (67 • N), spectra of solar ultraviolet radiation (UVR) have been measured with a Brewer spectroradiometer since 1990. The time series is one of the longest in the European Arctic region. In this work, the time series 1990-2014 was homogenized, and the data were corrected with respect to known error sources using laboratory characterizations and theoretical approaches. Methods for cosine correction, temperature correction and determination of long-term changes in spectral responsivity were applied. Bad measurements were identified by using various quality assurance tools including comparisons with reconstructed UV dose rates, synchronous broadband UV dose rates, global radiation and clear sky model calculations. We calculated daily maximum UV indices from the spectral time series. The daily maxima reached on average a value of 5 in midsummer, whereas the maximum UV index value of 6 was measured only twice: in 2011 and in 2013. We calculated the relative spectral changes in measured UV irradiances. An anti-correlation with total ozone was found in April and June, but no statistically significant longterm changes were found. The effect of snow, enhancing the measured UVR due to high albedo, was important during late spring. Short-term variations were mostly due to changes in cloudiness, which was the dominant factor during summertime.

Arabian Journal of Geosciences, 2016

In the Arctic region, Iceland is an important source of dust due to ash production from volcanic ... more In the Arctic region, Iceland is an important source of dust due to ash production from volcanic eruptions. In addition, dust is resuspended from the surface into the atmosphere as several dust storms occur each year. During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments. These experiments were made during the snow melt period using two different ash grain sizes (1 ϕ and 3.5 ϕ) from the Eyjafjallajökull 2010 eruption, collected on the glacier. Different amounts of ash were deposited on snow or ice, after which the snow properties and melt were measured. The results show that a thin ash layer increases the snow and ice melt but an ash layer exceeding a certain critical thickness caused insulation. Ash with 1 ϕ in grain size insulated the ice below at a thickness of 9-15 mm. For the 3.5 ϕ grain size, the insulation thickness is 13 mm. The maximum melt occurred at a thickness of 1 mm for the 1 ϕ and only 1-2 mm for 3.5 ϕ ash. A map of dust concentrations on Vatnajökull that represents the dust deposition during the summer of 2013 is presented with concentrations ranging from 0.2 up to 16.6 g m −2 .

Total ozone and UV measurements have been performed with the NILU-UV radiometer at the station of... more Total ozone and UV measurements have been performed with the NILU-UV radiometer at the station of Ushuaia (54

The manuscript is divided into two parts. First it presents the bipolar UV albedo monitoring stat... more The manuscript is divided into two parts. First it presents the bipolar UV albedo monitoring station at Sodankylä and Marambio. It explains in full details the setup and the challenges operating these polar stations. The second part tries to give an extensive overview over albedo measurements, analysis and modeling of these kinds of data. The later chapters are defined as literature review by the authors.

Optical Engineering, 2003

The occurrence of spikes in Brewer UV spectra is studied. Use is made of continuous measurement d... more The occurrence of spikes in Brewer UV spectra is studied. Use is made of continuous measurement data over several years, comprising more than 90,000 spectra, from one single-monochromator and two double-monochromator Brewers. It is shown that the double monochromators, especially, may suffer from more than 200 spikes per ϳ5000 annual spectra. The spikes are not always randomly distributed over the wavelength range. The single monochromator is found to have an annual average of only 36 spikes above 300 nm, but it is noted that there were a significant number of spikes at shorter wavelengths, indicating possible bias in the stray light correction unless taken into consideration. The error caused by noncorrected spikes varies greatly from case to case. In an intensive study of 150 spectra measured during one summer week, the effect of one moderate-size spike was found to be more than 5% on a DNA action dose rate and close to 1% on a DNA action daily dose. When high accuracy of in situ UV measurements is required, our results suggest a need to remove spikes from the spectra. A simple statistical approach is employed. The method is applicable to any singleor double-monochromator Brewer spectroradiometer. However, under rapidly changing cloudiness it can be difficult to distinguish between noise spikes and the variation in irradiance due to changes in the state of the sky. Our data show that ancillary radiation measurements may be necessary to interpret the data correctly.

EGU General Assembly Conference Abstracts, Apr 1, 2018

<p>The Sahara Desert is the largest source of dust worldwide. Finland, north of 60 ... more <p>The Sahara Desert is the largest source of dust worldwide. Finland, north of 60 <sup>o</sup>N, is annually affected by long-range transported Saharan dust, which is most often observed as red sunrises and sunsets. Observations on dust deposition on ground are rare. On 23 February 2021, Saharan dust was transported and deposited in the southern part of Finland, reaching up a long way inland. At the time, the ground was covered with snow, and therefore the dust deposition was more easily detectable. The deposition was accompanied by freezing rain in the most southern part of the country, and snowfall further north.</p><p>Samples of dust in snow were collected by citizens and forwarded to the Finnish Meteorological Institute (FMI) following our researchers’ guidelines advertised in social media. Most samples were a solid residue from 2 dl of superficial snow, that had been either melted and filtered using coffee filters, evaporated on an aluminum foil, or decanted with the help of containers. In addition, fresh samples were collected for reference and were stored in a freezer for further analysis. Samples were received from over 500 locations and each of these contained one or more filtered, evaporated, or decanted dust samples. Dust was observed as far north as Vaasa and Kuopio (~63 <sup>o</sup>N).</p><p>The event was forecasted by the operational SILAM global atmospheric-composition suite of FMI (http://silam.fmi.fi) five days in advance. The suite is driven by the meteorology from the Integrated Forecasting System (IFS) model of the European Centre for Medium-Range Weather Forecast (ECMWF). According to the model results, the near-surface concentrations of desert dust in Finland on 23.02.2021 were negligible, while the total column reached 100-200 µg/m<sup>2</sup>, and optical column thickness in some places was up to 0.2, which is enough to be visible. The scavenging of dust from aloft layers resulted in substantial contamination of snow. Light microscopy results indicate the presence of quartz particles in the range 5-15 µm compatible with desert dust. Processed samples from the Askola region (~60 °N), about 20 km north from the southern coastline, show depositions of ~1100 mg/m<sup>2</sup>. Dust deposition amounts may vary greatly depending on the location and precipitation amounts. Our work also includes ice nucleation experiments, determination of particle size distributions, investigations on organic compounds, microplastics and microorganisms. The citizen science nature of the project will be used to promote and disseminate FMI’s research on aerosols through a specific outreach programme. Our study aims at producing information on latitudinal Saharan dust transport, as well as on deposition particle shapes, size distributions and ice nucleation ability of the particles detected in Finland, through the analysis of the collected samples.</p><p> </p><p> </p>

GUV radiometer data from Marambio station for the period March 2017 - May 2019. UV-B and UV-A dai... more GUV radiometer data from Marambio station for the period March 2017 - May 2019. UV-B and UV-A daily maximum irradiances and dailydoses. Daily noon UV index and total column ozone. Daily maximum irradiances at 555 nm (VIS) and daily maximum of photosynthetically active radiation. If you use the data, please contact Kaisa Lakkala, Finnish Meteorological Institute.

Boreal Environment Research, 2016

Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the ass... more Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow with higher soot content, and it was observed immediately following soot deposition. Compared with a previous laboratory study the effects of soot on the snow were not as prominent in outdoor conditions. During snowmelt, about 50% of the originally deposited soot particles were observed to remain at the snow surface. More detailed experiments are however needed to better explain soot’s effect on snow and to better quantify this effect. Our albedo versus soot parameterization agreed relatively well with previously published relationships. (Less)

Atmosphere, 2020

Black carbon (BC), organic carbon (OC), and total carbon (TC) in snow are important for their cli... more Black carbon (BC), organic carbon (OC), and total carbon (TC) in snow are important for their climatic and cryospheric effects. They are also part of the global carbon cycle. Atmospheric black and organic carbon (including brown carbon) may deposit and darken snow surfaces. Currently, there are no standardized methods for sampling, filtering, and analysis protocols to detect carbon in snow. Here, we describe our current methods and protocols to detect carbon in seasonal snow using the OCEC thermal optical method, a European standard for atmospheric elemental carbon (EC). We analyzed snow collected within and around the urban background SMEARIII (Station for Measuring Ecosystem-Atmosphere Relations) at Kumpula (60° N) and the Arctic GAW (Global Atmospheric Watch) station at Sodankylä (67° N). The median BC, OC, and TC in snow samples (ntot = 30) in Kumpula were 1118, 5279, and 6396 ppb, and in Sodankylä, they were 19, 1751, and 629 ppb. Laboratory experiments showed that error due to...

<p&amp... more <p>Seemingly small amounts of black carbon (BC) in snow, of the order of 10–100 parts per billion by mass (ppb), have been shown to decrease its albedo by 1–5 %. Due to the albedo-feedback mechanism, surface darkening accelerates snow and ice melt and contributes to Arctic warming.</p><p>Here we present the most recent procedures we use for sampling, filtering and analysis of Arctic snow, ice and water samples, to determine their black carbon (BC), organic carbon (OC) and total carbon (TC) contents. For the purpose, we apply the OCEC analyzer of the Finnish Meteorological Institute’s aerosol laboratory, Helsinki, Finland (60°12 N). Particles are collected on a quarz-fiber filter and subjected to different temperature ramps following the protocols (NIOSH-870, EUSAAR2, or IMPROVE). Pyrolysis correction is by laser transmittance. Light transmittance through the filter is monitored during the collection phase to quantify BC. The OCEC thermal-optical method is the current European standard method for determination of atmospheric BC.  </p><p>Our Arctic samples include surface snow and snow profile samples collected north of the Arctic Circle at the Finnish Meteorological Institute Arctic Space Center in Sodankylä, Finland (67◦37 N, 26◦63 E), which is also a World Meteorological Institute’s Global Atmospheric Watch station (WMO GAW). In addition, samples from H2020 EU-Interact stations of Faroes FINI, Iceland Sudurnes and UK Cairngorms, and elsewhere from Iceland and Finland, including Helsinki Kumpula SMEAR-III station (60°12 N, 24°57 E, Station for Measuring Ecosystem-Atmosphere Relations, https://www.atm.helsinki.fi/SMEAR/index.php/smear-iii) and the most northern research catchment area of Pallas (68°N, about 130 km north from the Arctic Circle, https://blogs.egu.eu/divisions/hs/2019/06/19/featured-catchment-series-pallas/), have been sampled and analyzed. The BC concentrations have been detected to vary according to the origin of the air masses and as a result of the seasonal snow melt process.</p><p><em>Acknowledgements. We gratefully acknowledge support from the EU-Interact-BLACK-project Black Carbon in snow and water (H2020 Grant Agreement No. 730938); the Academy of Finland NABCEA-project of Novel Assessment of Black Carbon in the Eurasian Arctic (No. 296302), Ministry for Foreign Affairs of Finland IBA-project Black Carbon in the Arctic and significance compared to dust sources (No. PC0TQ4BT-25); the Academy of Finland Center of Excellence program The Centre of Excellence in Atmospheric Science - From Molecular and Biological processes to The Global Climate (No. 272041), and The Nordic Center of Excellence CRAICC Cryosphere–Atmosphere Interactions in a Changing Arctic…

Frontiers in Earth Science, 2019

Editorial on the Research Topic Atmosphere-Cryosphere Interaction in the Arctic, at High Latitude... more Editorial on the Research Topic Atmosphere-Cryosphere Interaction in the Arctic, at High Latitudes and Mountains With Focus on Transport, Deposition, and Effects of Dust, Black Carbon, and Other Aerosols Atmosphere and cryosphere are closely linked and therefore need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in recent decades, while such areas have been more fragile and less adaptable to global climate change (Boy et al., 2019). Atmospheric air pollutants, in particular black carbon (BC) and dust, are deposited on clean snow, land ice or sea ice surfaces, and decrease their albedo. Due to albedo-feedback, snow and ice are melting faster and seasonal snow cover earlier. Impacts of ice loss include reduction in the Earth's albedo and, as a positive feedback, this leads to further warming (Flanner et al., 2007), as for example in the Arctic region. Albedo is wavelength dependent and typically very high for clean snow, and decreases as a function of snow age, snow grain size, and impurity content (e.g., Warren and Wiscombe, 1980; Aoki et al., 2000; Gardner and Sharp, 2010). It is estimated that Arctic snow albedo is reduced primarily due to BC, but other impurities can also contribute to absorption, such as organic or brown carbon (Doherty et al., 2010). Surface albedo feedback has been found as the second main contributor to Arctic amplification (Pithan and Mauritsen, 2014), and BC deposition to snow and ice can strongly contribute to the darkening via black-carbon-on-snow forcing (Bond et al., 2013). The role of BC in snow and ice has been widely investigated, and detailed scientific assessments have been presented in Bond et al. (2013), Intergovernmental Panel on Climate Change (IPCC) (2013), and AMAP (2015). Seemingly small amounts of BC in snow, of the order of 10-100 parts per billion by mass (ppb), have shown to decrease its albedo by 1-5% (Hadley and Kirchstetter, 2012). A reduction in snow-surface density due to light absorbing impurities has been documented (Meinander et al., 2014; Skiles and Painter, 2017), and BC has also been suggested as disturbing the water holding capacity of snow (Meinander et al., 2014). Dust has been identified as reducing snow albedo in many parts of the world, for example the Chilean Andes,

A ground-based ultraviolet (GUV) multi-filter radiometer was set up at Marambio, 64 • S, 56 • W, ... more A ground-based ultraviolet (GUV) multi-filter radiometer was set up at Marambio, 64 • S, 56 • W, Antarctica, in 2017. The instrument continuously measures ultraviolet (UV) radiation, visible (VIS) radiation and photosynthetically active radiation (PAR). The measurements are designed for providing high-quality longterm time series that can be used to assess the impact of global climate change in the Antarctic region. The quality assurance includes regular absolute calibrations and solar comparisons performed at Marambio and at Sodankylä, Finland. The measurements continue observations at Marambio that were performed with (Norwegian Institute for Air Research UV Radiometer (NILU-UV) radiometers between 2000 and 2010 as part of the Antarctic NILU-UV network. These measurements are ideally suited for assessing the effects of the ongoing stratospheric ozone recovery on the ecosystem, as the data products include information on radiation at various wavelengths ranging from UV to VIS so that changes on biologically effective radiation due to ozone can be separated from those due to other factors. Data products include total ozone, photosynthetically active radiation (PAR), visible (VIS) radiation at 555 nm, UV index, UV irradiance at 5 channels, UVB and UVA dose rate and daily dose, and biologically weighted UV dose rate and daily dose, calculated with 10 different action spectra. The data from the last 5 d and the daily maximum UV index time series are plotted and updated daily on the following web

Atmospheric Chemistry and Physics Discussions, 2018

The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic C... more The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, was the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic Region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual Centre with the objectives to identify and quantify the major processes controlling Arctic warming and related feedback mechanisms, to outline strategies to mitigate Arctic warming and to develop Nordic Earth System modelling with a focus on the short-lived climate forcers (SLCF), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special-issue of the journal Atmospheric Chemistry and Physics. This manuscript presents an overview on the main scientific topics investigated in the Centre and provides the reader a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Facing the vast amount of outcomes we are not claiming to cover all results from CRAICC in this manuscript but concentrate here on the main results which are related to the feedback loops in the climate change-cryosphere interaction scheme affecting the Arctic amplification. 1 Introduction Near-surface climate warming in the Arctic has proceeded at approximately twice the global average rate since 1980. This extraordinary rate of warming has been recognized since the late 1990s (Serreze et al., 2000) and has accelerated even since then (Bekryaev et al., 2010), leading to extreme events in 2016 when October-December temperatures in large parts of the Arctic were more than 5˚C above normal and daily anomalies exceeded 16˚C in many locations

AIP Conference Proceedings, 2017

At Sodankylä (67 • N), spectra of solar ultraviolet radiation (UVR) have been measured with a Bre... more At Sodankylä (67 • N), spectra of solar ultraviolet radiation (UVR) have been measured with a Brewer spectroradiometer since 1990. The time series is one of the longest in the European Arctic region. In this work, the time series 1990-2014 was homogenized, and the data were corrected with respect to known error sources using laboratory characterizations and theoretical approaches. Methods for cosine correction, temperature correction and determination of long-term changes in spectral responsivity were applied. Bad measurements were identified by using various quality assurance tools including comparisons with reconstructed UV dose rates, synchronous broadband UV dose rates, global radiation and clear sky model calculations. We calculated daily maximum UV indices from the spectral time series. The daily maxima reached on average a value of 5 in midsummer, whereas the maximum UV index value of 6 was measured only twice: in 2011 and in 2013. We calculated the relative spectral changes in measured UV irradiances. An anti-correlation with total ozone was found in April and June, but no statistically significant longterm changes were found. The effect of snow, enhancing the measured UVR due to high albedo, was important during late spring. Short-term variations were mostly due to changes in cloudiness, which was the dominant factor during summertime.

Arabian Journal of Geosciences, 2016

In the Arctic region, Iceland is an important source of dust due to ash production from volcanic ... more In the Arctic region, Iceland is an important source of dust due to ash production from volcanic eruptions. In addition, dust is resuspended from the surface into the atmosphere as several dust storms occur each year. During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments. These experiments were made during the snow melt period using two different ash grain sizes (1 ϕ and 3.5 ϕ) from the Eyjafjallajökull 2010 eruption, collected on the glacier. Different amounts of ash were deposited on snow or ice, after which the snow properties and melt were measured. The results show that a thin ash layer increases the snow and ice melt but an ash layer exceeding a certain critical thickness caused insulation. Ash with 1 ϕ in grain size insulated the ice below at a thickness of 9-15 mm. For the 3.5 ϕ grain size, the insulation thickness is 13 mm. The maximum melt occurred at a thickness of 1 mm for the 1 ϕ and only 1-2 mm for 3.5 ϕ ash. A map of dust concentrations on Vatnajökull that represents the dust deposition during the summer of 2013 is presented with concentrations ranging from 0.2 up to 16.6 g m −2 .

Total ozone and UV measurements have been performed with the NILU-UV radiometer at the station of... more Total ozone and UV measurements have been performed with the NILU-UV radiometer at the station of Ushuaia (54