| 1031. |
- Zhou, Chunlue, et al.
(författare)
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HomogWS-se: a century-long homogenized dataset of near-surface wind speed observations since 1925 rescued in Sweden
- 2022
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 14:5, s. 2167-2177
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Tidskriftsartikel (refereegranskat)abstract
- Creating a century-long homogenized near-surface wind speed observation dataset is essential to improve our current knowledge about the uncertainty and causes of wind speed stilling and recovery. Here, we rescued paper-based records of wind speed measurements dating back to the 1920s at 13 stations in Sweden and established a four-step homogenization procedure to generate the first 10-member centennial homogenized wind speed dataset (HomogWS-se) for community use. Results show that about 38 % of the detected change points were confirmed by the known metadata events, and the average segment length split by the change points is similar to 11.3 years. Compared with the raw wind speed series, the homogenized series is more continuous and lacks significant non-climatic jumps. The homogenized series presents an initial wind speed stilling and subsequent recovery until the 1990s, whereas the raw series fluctuates with no clear trend before the 1970s. The homogenized series shows a 25 % reduction in the wind speed stilling during 1990-2005 than the raw series, and this reduction is significant when considering the homogenization uncertainty. The homogenized wind speed series exhibits a significantly stronger correlation with the North Atlantic oscillation index than that of the raw series (0.54 vs. 0.29). These results highlight the importance of the century-long homogenized series in increasing our ability to detect and attribute multidecadal variability and changes in wind speed. The proposed homogenization procedure enables other countries or regions to rescue their early climate data and jointly build global long-term high-quality datasets. HomogWS-se is publicly available from the Zenodo repository at (Zhou et al., 2022).
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| 1032. |
- Zhou, Q. M., et al.
(författare)
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Decompositions of Taylor diagram and DISO performance criteria
- 2021
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 41:12, s. 5726-5732
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Tidskriftsartikel (refereegranskat)abstract
- Taylor diagram has been frequently used to evaluate climate or hydrology models or data. A Taylor diagram summarizes three frequently used metrics including correlation coefficient (CC), standard deviation (STD), and centred root mean square error (RMSEc). Although these three metrics are relevant metrics for some applications, in some cases, additional indicators are needed, which calls for a new method. This study firstly addressed the short comments about the distance between indices of simulation and observation (DISO) described in a previous study. Secondly, the number of statistical metrics of DISO is extended from 3 to more than 3. The statistical metrics of the expanded DISO are more flexible than the Taylor diagram which uses the three fixed metrics. Thirdly, the current work compares the Taylor diagram with the expanded DISO in terms of their theoretical bases, revealing the advantage of DISO in terms of its flexibility in the selection of different types of metrics, and its suitability as an effective single metric to express a model's or dataset's overall quality. The power and flexibility of the expanded DISO are discussed.
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| 1033. |
- Zinke, Julika, 1995-
(författare)
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Factors influencing emission fluxes and bacterial enrichment in sea spray aerosols : Insights from laboratory and field studies
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sea spray aerosol (SSA) is one of the major natural aerosol sources and is produced when wave breaking entrains air into ocean surface water, which subsequently breaks up into bubbles. These bubbles rise to the surface and can scavenge biogenic material. Once they reach the surface, they burst and produce both a large number of relatively small film drops that result from the disintegration of the bubble film cap and a smaller number of jet drops that result from the collapse of the bubble cavity and are typically larger in size than the film drops. The production of SSA is influenced by several factors, including wind speed, sea state, seawater temperature, salinity, and the physicochemical and biological condition of the ocean. SSA can significantly impact Earth's radiation budget by scattering incoming solar radiation directly and by acting as cloud condensation nuclei. To improve our understanding of the impact of sea spray aerosols on the Earth’s climate, it is critical to understand the physical mechanisms which determine the size-resolved SSA production flux. Furthermore, SSA can be a vector for the emission of primary biological airborne particles (PBAP) from the oceans to the atmosphere. PBAP encompass bacteria, viruses, pollen and spores and can be present in the atmosphere in form of agglomerates, single particles or cell fractions. Although, the abundance of PBAP typically only make up < 0.1% of the number of aerosols, this does not imply their insignificance. On the contrary, PBAP are known to be very efficient cloud- and ice condensation nuclei and thus can influence cloud properties such as cloud phase, albedo and lifetime, thereby affecting the Earth’s climate as well as biogeochemical cycles. As the Earth is 70% covered by oceans, of which most could be characterized as remote, quantifying the PBAP emissions over these waters are important for the enhancement of climate models.The goal of this thesis was to study the factors impacting SSA emissions and the emission of primary biological particles with SSA with particular focus on bacteria emissions. This was done both through laboratory and field experiments in the Baltic Sea and in the Azores archipelago using a plunging jet sea spray simulation chamber and various techniques to characterize aerosol emissions. More specifically, a parameterization for the SSA production flux as a function of salinity and temperature was derived from laboratory experiments and a wind speed and sea state dependent parameterization were derived from ambient eddy covariance (EC) flux measurements in the Baltic Sea. The combination of EC flux measurements and laboratory generated SSA allowed to derive a chamber specific scaling factor that could be applied to derive bacteria emission fluxes ranging between 16-63 cells m−2 s−1 from the Baltic Sea. Bacteria were found to be 13-488 and 9-148 times enriched in SSA compared to the underlying seawater from mesocosm experiments in the Baltic Sea and Azores, respectively. A comparison of single cell abundance estimates from fluorescence microscopy and real-time measurements of PBAP with diameters > 0.8 µm using a bioaerosol sensor revealed that the latter yielded consistently lower concentrations. The discrepancy was explained by differences in the sampling approach and size cut-offs (i.e. single cells versus agglomerates or particle-attached cells). As such, both methods are applicable to different research questions and should be considered complementary.An analysis of the microbial community composition in the aerosols and underlying seawater showed selective aerosolization of certain bacteria taxa. Furthermore, selective growth and a decrease in alpha diversity in the seawater was observed when the mesocosm experiments were operated in a closed mode (meaning that the seawater was not exchanged over the duration of each experiment), which can however be circumvented by continuously replacing the water in the mesocosm.Ambient measurements of PBAP revealed diurnal variations with a peak during the early morning hours that was correlated to changes wind speed, wave height, air temperature, relative humidity, latent and sensitive heat flux.
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| 1034. |
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| 1035. |
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| 1036. |
- Åström, Stefan, 1977, et al.
(författare)
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Investment perspectives on costs for air pollution control affect the optimal use of emission control measures
- 2019
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Ingår i: Clean Technologies and Environmental Policy. - : Springer Science and Business Media LLC. - 1618-954X .- 1618-9558. ; 21:3, s. 695-705
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Tidskriftsartikel (refereegranskat)abstract
- Cost-effective air pollution emission control has been in focus for decades in international air pollution regulations. Despite large observed emission reductions for many air pollutants, environmental and human health problems persist and more efforts are needed. However, some stakeholders are concerned that the costs for remaining emission control measures are prohibitively high. There are several reasons for concern, and one can be the difference in investment perspectives—i.e. costs of borrowing and time constraints—held by stakeholders. By using the integrated assessment model GAINS, we study whether differences in investment perspectives of Nordic stakeholders influence measures selected for cost-effective emission control and can motivate concerns for high costs of emission control. We distinguish the control cost calculations between a social planner perspective and a corporate perspective and apply these to the GAINS model database on emission control measures. A cost-minimized selection of measures in 2030 is then calculated for increasing environmental and health ambitions for both perspectives. The results show an irregular pattern, but for a range of ambition levels the corporate perspective affects the selection of measures and implies surplus costs for the Nordic social planner of up to 120 million € per year. This is 36% more expensive than the costs of the social planners’ selection. Conversely, from a corporate perspective the social planners’ selection can imply cost increases of up to 180 million €. We therefore suggest that control of investment perspective effects should be standard in analysis of cost-effective air pollution measures.
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| 1037. |
- Aldenhoff, Wiebke, 1985
(författare)
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Sea Ice Concentration Estimation and Ice Type Classification from Dual-Frequency Satellite Synthetic Aperture Radar
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The sea ice cover in the Arctic has undergone dramatic changes in recent years. The perennial sea ice extent is decreasing by 12.2 % per decade while annual mean sea ice thickness has decreased by more than 2 m for the central Arctic Basin from 1975 to 2012. High resolution information of the ice cover is necessary for a better understanding of the involved processes. Furthermore increased economic, scientific and touristic activities in the Arctic demand ice information for safer navigation in ice infested waters.Satellite synthetic aperture radar facilitates year round monitoring of the sea ice cover with high spatial and temporal coverage. High resolution is a requirement to capture small scale sea ice features like leads and the dynamics of the ice cover driven by the atmosphere and ocean.This thesis presents investigations on sea ice characterization from multi-spectral SAR imagery. Dual-polarization C- and L-band images from Sentinel-1 and ALOS PALSAR-2 have been used to derive sea ice concentration, for creation of ice-water maps and ice type classification. The developed algorithms for sea ice concentration estimation and ice/water classification use spatial autocorrelation as a texture feature to improve the discrimination of ice and water. The mapping between image features and the output variable is realized with a neural network. The proposed algorithms show good performance when evaluated against manually derived ice charts and radiometer data. We demonstrate that C- and L-band contain complementary data and a combination of these frequencies could achieve more robust classification results.Furthermore the separability and signatures of ice types in different ice regimes, i.e. marginal ice zone, pack ice and areas containing fast ice, have been investigated. Classification only based on backscatter intensities has been carried out by means of a support vector machine on selected examples of the same C- and L-band dataset. The results indicate that also for ice type classification a combination of frequencies can improve the classification accuracy.
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| 1038. |
- Andersson, Sven-Ingvar, 1943, et al.
(författare)
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Catalyst evaluation using an ARCO pilot unit on north sea atmospheric residue
- 2010
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Ingår i: Advances in Fluid Catalytic Cracking: Testing, Characterization, and Environmental Regulations. - : CRC Press. - 9781420062557 ; , s. 37-62
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- At the end of the 1970s Statoil cracked a North Sea atmospheric residue for the first time in M. W. Kellogg’s circulating pilot unit in Texas [1]. This pilot unit was quite large, with a capacity of one barrel a day. The test in this pilot unit was very successful and showed that North Sea atmospheric residues were very suitable feedstocks for a residue fluid catalytic cracker, and that North Sea atmospheric residues gave very promising product yields.
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| 1039. |
- Brandefelt, Jenny, et al.
(författare)
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A coupled climate model simulation of Marine Isotope Stage 3 stadial climate
- 2011
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 7:2, s. 649-670
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Tidskriftsartikel (refereegranskat)abstract
- We present a coupled global climate model (CGCM) simulation, integrated for 1500 yr to quasi-equilibrium, of a stadial (cold period) within Marine Isotope Stage 3 (MIS 3). The simulated Greenland stadial 12 (GS12; similar to 44 ka BP) annual global mean surface temperature (T-s) is 5.5 degrees C lower than in the simulated recent past (RP) climate and 1.3 degrees C higher than in the simulated Last Glacial Maximum (LGM; 21 ka BP) climate. The simulated GS12 is evaluated against proxy data and previous modelling studies of MIS3 stadial climate. We show that the simulated MIS 3 climate, and hence conclusions drawn regarding the dynamics of this climate, is highly model-dependent. The main findings are: (i) Proxy sea surface temperatures (SSTs) are higher than simulated SSTs in the central North Atlantic, in contrast to earlier simulations of MIS 3 stadial climate in which proxy SSTs were found to be lower than simulated SST. (ii) The Atlantic Meridional Overturning Circulation (AMOC) slows down by 50% in the GS12 climate as compared to the RP climate. This slowdown is attained without freshwater forcing in the North Atlantic region, a method used in other studies to force an AMOC shutdown. (iii) El-Nino-Southern Oscillation (ENSO) teleconnections in mean sea level pressure (MSLP) are significantly modified by GS12 and LGM forcing and boundary conditions. (iv) Both the mean state and variability of the simulated GS12 is dependent on the equilibration. The annual global mean T-s only changes by 0.10 degrees C from model years 500-599 to the last century of the simulation, indicating that the climate system may be close to equilibrium already after 500 yr of integration. However, significant regional differences between the last century of the simulation and model years 500-599 exist. Further, the difference between simulated and proxy SST is reduced from model years 500-599 to the last century of the simulation. The results of the ENSO variability analysis is also shown to depend on the equilibration.
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| 1040. |
- Dammann, Dyre Oliver, 1985, et al.
(författare)
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Instantaneous sea ice drift speed from TanDEM-X interferometry
- 2019
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Ingår i: Cryosphere. - : Copernicus GmbH. - 1994-0424 .- 1994-0416. ; 13:4, s. 1395-1408
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Tidskriftsartikel (refereegranskat)abstract
- The drift of sea ice is an important geophysical process with widespread implications for the ocean energy budget and ecosystems. Drifting sea ice can also threaten marine operations and present a hazard for ocean vessels and installations. Here, we evaluate single-pass along-track synthetic aperture radar (SAR) interferometry (S-ATI) as a tool to assess ice drift while discussing possible applications and inherent limitations. Initial validation shows that TanDEM-X phase-derived drift speed corresponds well with drift products from a ground-based radar at Utqiagvik, Alaska. Joint analysis of TanDEM-X and Sentinel-1 data covering the Fram Strait demonstrates that S-ATI can help quantify the opening/closing rate of leads with possible applications for navigation. S-ATI enables an instantaneous assessment of ice drift and dynamic processes that are otherwise difficult to observe. For instance, by evaluating sea ice drift through the Vilkitsky Strait, Russia, we identified short-lived transient convergence patterns. We conclude that S-ATI enables the identification and analysis of potentially important dynamic processes (e.g., drift, rafting, and ridging). However, current limitations of S-ATI are significant (e.g., data availability and they presently only provide the cross-track vector component of the ice drift field) but may be significantly reduced with future SAR systems.
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