PAN-EURASIAN EXPERIMENT (PEEX) PROGRAM: GRAND CHALLENGES IN THE ARCTIC-BOREAL CONTEXT

The role of arctic and boreal area is crucial in understanding rapidly changing global climate. The climate change itself has an enhanced effect in arctic and boreal areas. On the other hand, several feedback loops and mechanisms could either enhance or decelerate climate change. Besides these interlinks, the territory has enormous natural resources and the way they are utilised in future gives us a direction how to meet global grand challenges and regional impacts. Regionally, effective early warning systems and comprehensive monitoring will guide in reducing emissions in practise and save natural resources. Here we give insight into these issues, introduce the SMEAR (Station for Measuring Ecosystem-Atmosphere Relations) concept applicable to the PEEX network, and give a roadmap from deep understanding to practical solutions.


BACKGROUND
Earth's system is facing several environmental challenges on a global scale, called "Grand Challenges".The growing population needs more fresh water, food and energy, which will affect our climate, air quality, ocean acidification, loss of biodiversity and shortages of fresh water and food supplies.Grand Challenges are the main factors controlling human well-being and security as well as the stabilities of future societies.Since the Grand Challenges are highly connected and interlinked, they cannot be solved separately.Therefore, a framework is needed in which a multidisciplinary scientific approach has the required critical mass and is strongly connected to fast-tracked policy making.The potential solutions are typically tightly coupled with each other (e.g.[Kulmala et al., 2015a]).To meet this requirement, a deep understanding based on new scientific knowledge is needed.
In order to avoid the collapse of the Earth system, one may estimate that the mankind has approximately a 40-year window of opportunity to find a common mind-set and practical solutions to answer the Grand Challenges.This estimate is based on the observed concentrations of CO 2 .This year the maximum monhtly mean observed in May at the WMO GAW station Mauna Loa was 404 ppm (NOAA 2015 data: ftp://aftp.cmdl.noaa.gov/products/trends/co2/co2_mm_mlo.txt),corresponding the global atmospheric CO 2 concentration.If global CO 2 emissions continue increasing at the same rate as they have done, within 40 years the CO 2 concentration overpasses 500 ppm.
The atmosphere forms a major part of the environment to which life on Earth is sensitively responsive.The atmosphere closely interacts with the biosphere, hydrosphere, cryosphere, pedosphere and lithosphere as well as urban surfaces on time scales from seconds to millennia [Wanner et al., 2008].Changes in one of these components are directly or indirectly communicated to the others via intricately-linked processes and feedbacks.In recent years, a lot of research has been motivated by the importance of atmospheric aerosols on the global radiation budget, cloud formation and human health.Concentrations of reactive gases, greenhouse gases (GHGs) and atmospheric aerosol particles are tightly connected with each other via physical, chemical and biological processes occurring in the atmosphere, biosphere and at their interface [ [Kulmala et al., 2015a]].Permafrost thawing together with the Arctic sea ice changes will have multiple environmental (greenhouse gas emissions, air quality), economic (energy production, use of mineral, traffic and shipping and infrastructures) and societal (urbanization, cultural changes) consequences.Complex assessment of such consequences could be done using atlas systems.In Russia the National Atlas of Arctic is based on this conception [Kasimov et al., 2015

SMEAR CONCEPT AS APPLIED TO PEEX OBSERVATION SYSTEM
One of the first tasks of the PEEX infra pillar is to establish a process towards high-level Northern Eurasian Observation Networks.Particularly the Siberian region is currently lacking a coordinated and coherent groundbased atmosphere-ecosystem measurement network crucial for observing and predicting the effects of climate change in the Northern Pan-Eurasian region.The SMEAR concept provides a state-of-the-art foundation for establishing a PEEX observation system that integrates this system to the global GEOSS data system

SMEAR concept essentials
The SMEAR (Station for Measuring Ecosystem-Atmosphere Relations) concept has been .In order to cover the whole globe and be able to establish a Global SMEAR network, new proxies based on satellite data need to be developed as well [Bondur, 2011[Bondur, , 2014]].

Technical elements of the SMEAR concept
The SMEAR concept consists of elements like the technical description of the SMEAR station prototypes at different hierarchy levels, SMEAR data system and plan of a global SMEAR station network.These main elements of the SMEAR concept are applicable to developing the existing stations, building new stations at once or to be uprated gradually towards a flagship station.For example, in Russia we have already mapped 206 potential atmospheric or ecosystem stations that could be a part of the PEEX-Russia observation network [Alekseychik et al., 2016].Furthermore, we have already selected stations which could provide a pilot approach together with most advanced station in Russia and be integrated towards SMEAR measurement concept (Fig. 1). The

PEEX INFRASTRUCTURE FRAMEWORK
The PEEX research infrastructure development is a back bone for performing the PEEX research agenda.It is important to understand that novel infrastructure and data are not only the basis for scientific breakthroughs but have also direct impacts on several other sectors of interest.A novel RI is useful for different type of end-users, including climate and air quality policy makers at regional and global scales, regional operational services and people developing new observation techniques and innovations for global markets (Fig. 2).processes occurring in the atmosphere and at the atmosphere -biosphere -water cycle interfaces.For example, the precipitation response and thus the hydrological sensitivity differ strongly for greenhouse gas forcing and aerosol forcing.Decreasing aerosol emissions in the future can lead to an even stronger increase in precipitation as can be expected from GHG forcing alone [Westervelt et al., 2015].no/), in order to collect new information on regional GHG, trace gas and aerosol loadings, estimates on hygroscopicity (related to dose of the population from the loadings) and composition (related to toxicity of the particles) and estimates of how much of the loading is due to the long range transport.
The social benefits are optimal when timely, high-quality and long-term observational data and modeling data are available to aid air quality decision-makers at every levelfrom intergovernmental organizations to local government and then to citizens.World Health Organization (WHO) has estimated that in 2012 7 million premature deaths world-wide attributed to air pollution, which makes it the single largest cause of death in the world (WMO 2015).
Long-term information on trends is crucial for understanding the land-atmosphere interactions of urban environments and effectiveness of air quality policies.So far, the best results have been related to the verification of the feedback loops [Kulmala et al., 2004[Kulmala et al., , 2013[Kulmala et al., , 2014]], Biogeochemical cycles and atmospheric new particle formation (e.g.[Mäkelä et al., 1997, Kulmala et al., 2013]).By quantifying processes, interactions and feedbacks related to the PEEX objectives.We will be able to identify, for example, the steps that are needed to reduce air pollution levels in megacities by a factor of 3-4, to determine how pollutant emissions in China are affecting arctic and boreal areas, and to find out how these effects will be changed due to future emission reductions in Russia and China.
Novel measurement data can also be used for a cost-benefit analysis relevant to different actions to improve air quality, fresh water and food supply, environmentally and economically sustainable use of natural resources including energy, and to prevent further climate change.Such activity would be linked to continuous and comprehensive research, atmospheric and emission modelling, and the process level understanding at regional scale.For example, the factors controlling the air quality in mega-cities need to be quantified and recognized, and the solutions need to be found in collaboration with the private sector, the local government and the national government levels [Zilitinkevich et al., 2015].It is also important to investigate application of active remote sensing instruments, such as ceilometers and weather radars, to diagnose weather conditions leading to severe air pollution episodes.

PEEX RI contribution to operational services at regional scale
There will be large regional differences in warming due to the changing surface conditions and permanent changes in circulation or precipitation patterns (IPCC).
Refer to European ACTRIS-I3-RI Roadmap regional monitoring of climate change is important to documenting to what extent the predicted climate change will actually occur and to take it into account in the development of weather forecast and climate models.National weather services need wellmeasured climatic components for testing improved physical parameterizations in weather forecast models predicting hazardous weather events.Weather services also need to evaluate cloud-aerosol and other air-pollutant schemes in forecast models.Near-real-time applications are also needed for chemical weather prediction to be delivered to policy makers at all levels and to the general public.
To be able to respond to these requirements, the most climatic regions of Northern Eurasia should be represented by at least one PEEX core station for high resolution observations.Current operational weather forecast models have maximal horizontal resolution of 1km or so and cannot resolve microphysical processes; instead, these are to be parameterized in terms of bulk variables held in the mode, typically at about 1-km scale.

Fig. 1 .
Fig. 1.Locations of permanent ground-based observation stations in the PEEX domain (Lappalainen et al. 2016, manuscript in preparation).The stations in Russia could provide a PEEX network pilot approach and be integrated to the SMEAR measurement concept.

Fig. 2 .
Fig. 2. The potential impact sectors and end-user groups of the PEEX Research Infrastructure (RI).Similar type of impact and end-user approach was applied in a frame of developing ACTRIS infrastructure in Europe.
Arneth et al. 2010, Stocker et al., 2013; Kulmala et al., 2014a; Unger et al., 2014].Human and societal actions, such as emission policy, urbanization, forest management and land use change, as well as various natural feedback mechanisms involving the biosphere and atmosphere, have substantial impacts on the complicated couplings between atmospheric aerosols, trace gases, GHG, air quality and climate [Raes et al. 2010; Shindell et al. 2012; Stocker et al., 2013; Baklanov et al., 2015].
st pillar is aimed to form holistic understanding of the dominating feedbacks and triggers of the land-atmosphere-aquatic systems and human activities relevant to the arctic-boreal region.The 2 nd pillar is
[Ghan et al., 2012;Zhang et al., 2012;Schutgens and Stier, 2014]ansport between the atmosphere and surface, in order to understand processes, interactions and feedbacks.The core measurements of SMEAR stations cover meteorological parameters, such as the temperature, relative humidity, wind, precipitation and radiation, as well as atmospheric composition and biological activity (incl.aerosols,clouds,atmosphericchemistry,greenhouse gases, CO, O 3 , NO x , SO 2 , VOCs, CH 4 , NH 3 , H 2 SO 4 , HONO, HNO 3 , ions, external radiation, radon, photosynthesis, soil profiles and chemistry).These measurements include both concentrations and fluxes.In Finland, SMEAR-type measurements are currently conducted at six stations located in forests, peatlands and lakes (atmospherebiosphere interface), and in urban (urban surface) and marine/coastal environments.informationforglobalclimate models and regional air quality models[Ghan et al., 2012;Zhang et al., 2012;Schutgens and Stier, 2014].A fundamental part of the SMEAR measurement concept is to connect in situ measurements to satellite based information[Kulmala et al.,   2011]

GEOGRAPHY. ENVIRONMENT. SUSTAINABILITY. 02 (09) 2016
to be implemented into large-scale climate models, regional models and atmospheric chemistry models.At the moment the existing observation networks do not deliver information with sufficient accuracy to understand feedback loops, interactions and processes in the land-atmosphericocean continuum.As a whole, connected measurements provide a potential for scientific breakthroughs.inter-linked with the climate system.Trace gases and atmospheric aerosols are tightly connected with each other via physical, chemical, meteorological and biological Kulmala et al.)in the Northern Eurasian region.The latter addresses the urgent need for observations of critical environmental parameters worldwide, evoking a political consensus to overcome various geopolitical interests and prioritize the sustainable living conditions in different parts of the world, and providing sustainable technological solutions for the Grand Challenges aimed at efficient moderation of environmental changes.The PEEX agenda contributes to the Manifesto by providing conceptual design of the landatmosphere observation network for the Northern regions, in particular, for Russia.Furthermore, PEEX contributes to the global agenda by acting as a Future Earth Arcticboreal hub in frames of coordination of the Earth System research, and belongs to the key initiatives of GEOSS Cold Region activities.PEEX will actively seek for long-term funding in order to establish new SMEAR-concept stations and to make their continuous operation possible.Allthis should be based on national, bilateral, Nordic and all-European funding with matching funding concepts in Russia and China.Estimated building cost is approximately 15-20 million Euros per one flagship station.Such stations can be grown up from integrative blocks (1 million Euros per block).The annual operation costs are ca 10 % of the investment costs.ACKNOWLEDGEMENTS We acknowledge support from "International Working Groups, Markku Kulmala" Grant by Finnish Cultural Foundation, Academy of Finland projects ICOS 271878, ICOS-Finland No. 281255, ICOS-ERIC No. 281250, No. 259537, 218094, 255576, 286685, 280700 and 259537 funded, Tekes-project Beautiful Beijing, Nordforsk NCoE-CRAICC (no 26060) and Nordforsk CRAICC-PEEX-Amendment to contact 26060, the European Erasmus + CBHE project ECOIMPACT 561975-EPP-1-2015-1-FI-EPPKA2-CBHE-JP (2015-2018); Academy of Finland project ABBA No. 280700 (2014-2017); Russian Ministry of Education and Science Mega-grant No. 11.G34.31.0048 (2011-2015); Russian Science Foundation projects No. 15-17-20009 (2015-2018) and No. 15-17-30009 (2015-2018), geochemical foundations of PEEX were developed under support of the Russian Science Foundation project No. 14-27-00083 (2014-2016).Furthermore, we thank Russian Ministry of Education and Science Grant № 14.583.21.0003, unique identifier of the project RFMEFI58314X0003 (ISR "AEROCOSMOS", 2014-2016); Russian Ministry of Education and Science Grant № 14.586.21.0004, unique identifier of the project RFMEFI58614X0004 (ISR "AEROCOSMOS", 2014-2016).