Influence of biogenic emissions from boreal forests on aerosol-cloud interactions

Boreal forest acts as a carbon sink and contributes to the formation of secondary organic aerosols via emission of aerosol precursor compounds. However, these influences on the climate system are poorly quantified. Here we show direct observational evidence that aerosol emissions from the boreal forest biosphere influence warm cloud microphysics and cloud-aerosol interactions in a scale-dependent and highly dynamic manner. Analyses of in situ and ground-based remote-sensing observations from the SMEAR II station in Finland, conducted over eight months in 2014, reveal substantial increases in aerosol load over the forest one to three days after aerosol-poor marine air enters the forest environment. We find that these changes are consistent with secondary organic aerosol formation and, together with water-vapour emissions from evapotranspiration, are associated with changes in the radiative properties of warm, low-level clouds. The feedbacks between boreal forest emissions and aerosol-cloud interactions and the highly dynamic nature of these interactions in air transported over the forest over timescales of several days suggest boreal forests have the potential to mitigate climate change on a continental scale. Our findings suggest that even small changes in aerosol precursor emissions, whether due to changing climatic or anthropogenic factors, may substantially modify the radiative properties of clouds in moderately polluted environments. Emissions from the boreal forest biosphere can substantially increase aerosol load above the forest and influence the radiative properties of clouds, according to analysis of observations from a monitoring station in Finland.Peer reviewe

Overview : Integrative and Comprehensive Understanding on Polar Environments (iCUPE) - concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project "iCUPE - integrative and Comprehensive Understanding on Polar Environments" to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.Peer reviewe

Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context

Inadvertent Localized Intensification of Precipitation by Aircraft

Abstract: Eleven years of dual-polarization weather radar data, complemented by satellite and lidar observations, were used to investigate the origin of areas of localized intensification of precipitation spotted in the vicinity of Helsinki-Vantaa airport. It was observed that existing precipitation is enhanced locally on spatial scales from a few kilometers to several tens of kilometers. The precipitation intensity in these localized areas was 6-14 times higher than the background large-scale precipitation rate. Surface observations and dual-polarization radar data indicate that snowflakes within the ice portion of the falling precipitation in the intensification regions are larger and more isotropic than in the surrounding precipitation. There appears to be an increase in the ice particle number concentration within the intensification region. The observed events were linked to arriving or departing air traffic. We advocate that the mechanism responsible for intensification is aircraft-produced ice particles boosting the aggregation growth of snowflakes. Plain Language Summary: By analyzing 11 years of dual-polarization weather radar observations in the Helsinki region, we have discovered that airplanes landing in or departing from the Helsinki-Vantaa airport could locally increase precipitation rate by as much as 14 times. The observed phenomenon is related to the hole-punch clouds, which are also forming with the help of airplanes. The reported observations allow us to have a better understanding of precipitation formation processes that take place in ice and mixed phase clouds. They show that falling ice crystals from upper clouds could seed lower clouds and therefore increase rain or snowfall intensity through the process called snowflake aggregation. During snowflake aggregation bigger faster falling particles are formed by ice particles colliding and sticking together.Peer reviewe

Combining airborne in situ and ground-based lidar measurements for attribution of aerosol layers

Understanding the distribution of aerosol layers is important for determining long-range transport and aerosol radiative forcing. In this study we combine airborne in situ measurements of aerosol with data obtained by a ground-based high spectral resolution lidar (HSRL) and radiosonde profiles to investigate the temporal and vertical variability of aerosol properties in the lower troposphere. The HSRL was deployed in Hyytiala, southern Finland, from January to September 2014 as a part of the U.S. DOE ARM (Atmospheric Radiation Measurement) mobile facility during the BAECC (Biogenic Aerosols - Effects on Cloud and Climate) Campaign. Two flight campaigns took place in April and August 2014 with instruments measuring the aerosol size distribution from 10 nm to 5 mu m at altitudes up to 3800 m. Two case studies with several aerosol layers present were selected from the flight campaigns for further investigation: one clear-sky and one partly cloudy case. During the clear-sky case, turbulent mixing ensured small temporal and spatial variability in the measured aerosol size distribution in the boundary layer, whereas mixing was not as homogeneous in the boundary layer during the partly cloudy case. The elevated layers exhibited larger temporal and spatial variability in aerosol size distribution, indicating a lack of mixing. New particle formation was observed in the boundary layer during the clear-sky case, and nucleation mode particles were also seen in the elevated layers that were not mixing with the boundary layer. Interpreting local measurements of elevated layers in terms of long-range transport can be achieved using back trajectories from Lagrangian models, but care should be taken in selecting appropriate arrival heights, since the modelled and observed layer heights did not always coincide. We conclude that higher confidence in attributing elevated aerosol layers to their air mass origin is attained when back trajectories are combined with lidar and radiosonde profiles.Peer reviewe

Research agenda for the Russian Far East and utilization of multi-platform comprehensive environmental observations

The Russian Far East is a region between China and the Russian Arctic with a diverse climatological, geophysical, oceanic, and economical characteristic. The southern region is located in the Far East monsoon sector, while the northern parts are affected by the Arctic Ocean and cold air masses penetrating far to the south. Growing economic activities and traffic connected to the China Belt and Road Initiative together with climate change are placing an increased pressure upon the Russian Far East environment. There is an urgent need to improve the capacity to measure the atmospheric and environmental pollution and analyze their sources and to quantify the relative roles of local and transported pollution emissions in the region. In the paper, we characterize the current environmental and socio-economical landscape of the Russian Far East and summarize the future climate scenarios and identify the key regional research questions. We discuss the research infrastructure concept, which is needed to answer the identified research questions. The integrated observations, filling in the critical observational gap at the Northern Eurasian context, are required to provide state-of-the-art observations and enable follow-up procedures that support local, regional, and global decision making in the environmental context.Peer reviewe

Arctic observations and sustainable development goals – Contributions and examples from ERA-PLANET iCUPE data

International audienceIntegrative and Comprehensive Understanding on Polar Environments (iCUPE) project developed 24 novel datasets utilizing in-situ observational capacities within the Arctic or remote sensing observations from ground or from space. The datasets covered atmospheric, cryospheric, marine, and terrestrial domains. This paper connects the iCUPE datasets to United Nations’ Sustainable Development Goals and showcases the use of selected datasets as knowledge provision services for policy- and decision-making actions. Inclusion of indigenous and societal knowledge into the data processing pipelines enables a feedback mechanism that facilitates data driven public services

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

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.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.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.Peer reviewe

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, is 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 of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), 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 paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change–cryosphere interactions that affect Arctic amplification

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, is 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 of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), 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 paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change–cryosphere interactions that affect Arctic amplification.The CRAICC team acknowledges the following institutions for financial support: the Finnish Cultural Foundation grant, Markku Kulmala “International Working Groups”; Russian mega-grant no. 11.G34.31.0048 (University of Nizhny Novgorod); Academy of Finland contracts 259537, 257411, and 254195; Beautiful Beijing (Finland–China collaboration project) funded by TEKES; Nordforsk CRAICC-PEEX (amendment to contract 26060); CRAICC-CRUCIAL (project no. 81257); Icelandic Research Fund (Rannis) grant no. 152248- 051; Danish Environmental Protection Agency with means from the Dancea fund for environmental support to the Arctic region (M 112 002700); the Villum Foundation; the Carlsberg Foundation (project 009_1_0515); COST1303 (TOPROF); COST ES1404 (HarmoSnow); and the Pan-Eurasian Experiment (PEEX). The development and use of NorESM1 was supported by the Norwegian Research Council through the projects Earth-Clim (207711/E10), EVA (grant no. 229771), NOTUR (nn2345k), and NorStore (ns2345k) and through the Nordic Centre of Excellence eSTICC (57001) and the EU H2020 project CRESCENDO (grant no. 641816). The CRAICC team also thanks Rogier Floors for providing Fig. 8 and Christoph Münkel for Fig. 9. The authors and entire CRAICC community would like to thank and acknowledge the work and inspiration of Jon Egill Kristjansson, whose life was cut short during these collaborations. Jon Egill Kristjansson is deeply missed, but his scientific legacy continues.Peer Reviewe