| 1. |
- Junninen, Heikki, et al.
(författare)
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Terpene emissions from boreal wetlands can initiate stronger atmospheric new particle formation than boreal forests
- 2022
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Ingår i: Communications Earth and Environment. - : Springer Science and Business Media LLC. - 2662-4435. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Aerosols and their interaction with clouds constitute the largest uncertainty in estimating the radiative forcing affecting the climate system. Secondary aerosol formation is responsible for a large fraction of the cloud condensation nuclei in the global atmosphere. Wetlands are important to the budgets of methane and carbon dioxide, but the potential role of wetlands in aerosol formation has not been investigated. Here we use direct atmospheric sampling at the Siikaneva wetland in Finland to investigate the emission of methane and volatile organic compounds, and subsequently formed atmospheric clusters and aerosols. We find that terpenes initiate stronger atmospheric new particle formation than is typically observed over boreal forests and that, in addition to large emissions of methane which cause a warming effect, wetlands also have a cooling effect through emissions of these terpenes. We suggest that new wetlands produced by melting permafrost need to be taken into consideration as sources of secondary aerosol particles when estimating the role of increasing wetland extent in future climate change.
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| 2. |
- Kulmala, Markku, et al.
(författare)
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On measurements of aerosol particles and greenhouse gases in Siberia and future research needs
- 2011
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Ingår i: Boreal Environment Research: An International Interdisciplinary Journal. - 1239-6095. ; 16:4, s. 337-362
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Tidskriftsartikel (refereegranskat)abstract
- The role of the world's boreal forest for our understanding of the climate system is indisputable. Due to the large area covered, the forest's biophysical (e.g. surface energy balance, albedo) and biogeochemical (e.g. bidirectional exchange of greenhouse gases or aerosol precursors) processes are known to affect today's climate, and will need to be accounted for in studies of climate feedbacks in response to anthropogenic warming. However, observations that are needed to develop and evaluate terrestrial and climate models are still relatively scarce, especially for the Siberian part of the boreal forest. Here, we present a short overview of aerosol and greenhouse gas measurements over Siberia, aiming to also survey a large fraction of the existing literature in Russian. We aim to highlight areas of least data coverage and argue that, due to the importance of Siberia in the global climate system, a coordinated research program is needed to address some of the open research questions: The Pan Siberian Experiment.
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| 3. |
- Lappalainen, Hanna K., et al.
(författare)
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Pan-Eurasian Experiment (PEEX) : towards a holistic understanding of the feedbacks and interactions in the land-atmosphere-ocean-society continuum in the northern Eurasian region
- 2016
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:22, s. 14421-14461
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Tidskriftsartikel (refereegranskat)abstract
- The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-atmosphereaquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context.
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| 4. |
- Mauritsen, Thorsten, et al.
(författare)
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A total turbulent energy closure model for neutrally and stably stratified atmospheric boundary layers
- 2007
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 64:11, s. 4113-4136
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a turbulence closure for neutral and stratified atmospheric conditions. The closure is based on the concept of the total turbulent energy. The total turbulent energy is the sum of the turbulent kinetic energy and turbulent potential energy, which is proportional to the potential temperature variance. The closure uses recent observational findings to take into account the mean flow stability. These observations indicate that turbulent transfer of heat and momentum behaves differently under very stable stratification. Whereas the turbulent heat flux tends toward zero beyond a certain stability limit, the turbulent stress stays finite. The suggested scheme avoids the problem of self-correlation. The latter is an improvement over the widely used Monin–Obukhov-based closures. Numerous large-eddy simulations, including a wide range of neutral and stably stratified cases, are used to estimate likely values of two free constants. In a benchmark case the new turbulence closure performs indistinguishably from independent large-eddy simulations.
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| 5. |
- Mohr, Matthias
(författare)
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Mesoscale Simulations of Atmospheric Flow in Complex Terrain
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The MIUU mesoscale model was further developed, in order to include information on large-scale atmospheric fields from global or regional atmospheric climate- and weather-prediction models. For this purpose, a new lateral boundary condition was developed and implemented into the model. The new lateral boundary condition is a combination of two existing conditions, namely the flow relaxation scheme and the tendency modification scheme.Tests indicated that an optimum lateral boundary configuration would be obtained with moderate to strong flow relaxation at higher levels, small flow relaxation at lower levels (within the atmospheric boundary layer), upstream advection at the outermost 4 grid points, and 6% horizontal grid stretching starting at a substantial distance from the lateral boundaries. The flow relaxation coefficients should be specified carefully, in order to minimize the reflection of all kinds of waves at the lateral boundaries.The summer thermal low in the mean-sea-level pressure field over North America is traditionally analyzed over the northern end of the Gulf of California. The position of this low is influenced by the application of the so-called plateau correction in obtaining mean-sea-level pressure values from highly elevated stations in North America. A model study indicated that the low should be located approximately 450 km to the north and somewhat to the east of the above location. A statistical comparison of model results from two mesoscale models against upper-air and surface measurements from several sites was carried out. Statistical methods, however, give only an insufficient picture of overall model performance. A comparison between predicted and measured tracer concentrations could be used to better evaluate the overall performance of different models.Sound propagation in the atmosphere was predicted in a mountain valley using a mesoscale atmospheric model together with a sound propagation model. This suggests that forecasts of sound propagation should be possible in future.
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| 6. |
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| 7. |
- Zilitinkevich, Sergej, et al.
(författare)
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An extended similarity theory for the stably stratified atmospheric surface layer
- 2000
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Ingår i: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY. - : ROYAL METEOROLOGICAL SOC. - 0035-9009. ; 126:566, s. 1913-1923
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Tidskriftsartikel (refereegranskat)abstract
- An advanced similarity-theory formulation for the wind and temperature profiles in the stably stratified atmospheric surface layer (ASL) is developed with due regard to the effect of the free-flow static stability on the ASL. In the revised log-linear pro
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| 8. |
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| 9. |
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| 10. |
- Zilitinkevich, Sergej
(författare)
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Non-local turbulence in stably stratified boundary layers
- 2000
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Ingår i: Advances in Turbulence VIII. Proceedings of the Eighth European Turbulence Conference (Eds. C. Dopazo et al.), CIMNE, Barcelona 2000, 311-314. ; , s. 311-314
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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