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- Bonaldi, Carlotta, et al.
(author)
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Recurrence, fidelity and proximity to previously visited sites throughout the annual cycle in a trans-Saharan migrant, the common cuckoo
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In: Journal of Avian Biology. - 0908-8857.
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Journal article (peer-reviewed)abstract
- Most migratory birds return every year to the same breeding sites and some species show a similarly high fidelity to wintering grounds as well. Fidelity to stopover sites during migration has been much less studied and is usually found to be lower. Here, we investigate site fidelity and distance to previously visited sites throughout the annual cycle in the common cuckoo, a nocturnal trans-Saharan migrant, based on satellite-tracking data from repeated annual migrations of thirteen adult males. All birds (100%) returned to the same breeding grounds, with a median shortest distance of only 1 km from the locations in previous year. This was in strong contrast to a much lower and much less precise site fidelity at non-breeding sites during the annual cycle: In only 18% of the possible cases in all non-breeding regions combined, did the cuckoos return to within 50 km of a previously visited non-breeding site, with no significant differences among the main staging regions (Europe in autumn, Sahel in autumn, wintering in Central Africa, West Africa in spring, Europe in spring). The shortest distance to a previously visited non-breeding site differed among the staging regions with median shortest distances for the longest stopovers of 131 km [2;1223] (median [min;max]) in Europe, 207 km [1;2222] in Sahel in autumn and 110 km [0;628] in Central Africa. The distance to a previously visited staging site decreased with the time spent at the stopover in a previous year. Understanding the drivers of recurrence and site selection in migratory birds are important for guiding conservation efforts in this group but further studies are needed to establish whether the patterns observed in cuckoos are general among terrestrial migrants with continuous distribution of habitat.
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- Buchwitz, M., et al.
(author)
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The GHG-CCI project of ESA's climate change initiative : Data products and application
- 2016
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In: Proceedings of Living Planet Symposium 2016. - 9789292213053 ; SP-740
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Conference paper (peer-reviewed)abstract
- The goal of the GHG-CCI project (http://www.esa-ghg-cci.org/) of ESA's Climate Change Initiative (CCI) is to generate global atmospheric satellite-derived carbon dioxide (CO2) and methane (CH4) data sets as needed to improve our understanding of the regional sources and sinks of these important greenhouse gases (GHG). Here we present an overview about the latest data set called Climate Research Data Package No. 3 (CRDP3). We focus on the GHG-CCI project core data products, which are near-surface-sensitive column-averaged dry air mole fractions of CO2 and CH4, denoted XCO2 (in ppm) and XCH4 (in ppb) retrieved from SCIAMACHY/ENVISAT (2002-2012) and TANSO-FTS/GOSAT (2009-today) nadir mode radiance observations in the near-infrared/shortwave-infrared spectral region. The GHG-CCI products are primarily individual sensor Level 2 products. However, we also generate merged Level 2 products ("EMMA products"). Here we also present a first GHG-CCI Level 3 product, namely XCO2 and XCH4 in Obs4MIPs format (monthly, 5°×5°).
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- Buchwitz, M., et al.
(author)
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The greenhouse gas project of Esa's climate change initiative (GHG-CCI) : Overview, achievements and future plans
- 2015. - 7W3
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In: 2015 36th International Symposium on Remote Sensing of Environment. - 1682-1750. ; 40, s. 165-172
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Conference paper (peer-reviewed)abstract
- The GHG-CCI project (http://www.esa-ghg-cci.org/) is one of several projects of the European Space Agency's (ESA) Climate Change Initiative (CCI). The goal of the CCI is to generate and deliver data sets of various satellite-derived Essential Climate Variables (ECVs) in line with GCOS (Global Climate Observing System) requirements. The "ECV Greenhouse Gases" (ECV GHG) is the global distribution of important climate relevant gases-namely atmospheric CO2 and CH4-with a quality sufficient to obtain information on regional CO2 and CH4 sources and sinks. The main goal of GHG-CCI is to generate long-term highly accurate and precise time series of global near-surface-sensitive satellite observations of CO2 and CH4, i.e., XCO2 and XCH4, starting with the launch of ESA's ENVISAT satellite. These products are currently retrieved from SCIAMACHY/ENVISAT (2002-2012) and TANSO-FTS/GOSAT (2009-today) nadir mode observations in the near-infrared/shortwave-infrared spectral region. In addition, other sensors (e.g., IASI and MIPAS) and viewing modes (e.g., SCIAMACHY solar occultation) are also considered and in the future also data from other satellites. The GHG-CCI data products and related documentation are freely available via the GHG-CCI website and yearly updates are foreseen. Here we present an overview about the latest data set (Climate Research Data Package No. 2 (CRDP#2)) and summarize key findings from using satellite CO2 and CH4 retrievals to improve our understanding of the natural and anthropogenic sources and sinks of these important atmospheric greenhouse gases. We also shortly mention ongoing activities related to validation and initial user assessment of CRDP#2 and future plans.
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- de Boer, G. N., et al.
(author)
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Multiscale Modelling of Elastohydrodynamic Tilted-Pad Bearings : a Metamodel Approach
- 2018
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Conference paper (peer-reviewed)abstract
- Elastohydrodynamic Lubrication (EHL) refers to the contact of two surfaces in relative motion under fully flooded conditions, pressure generated in the lubricant generates deformation of the bodies and this is coupled to determine a total load carrying capacity. In such contacts the size of surface topography and film thickness are of a similar order of magnitude and this therefore has a role in describing the phenomena. However the length scales associated with surface topography and the contact region are disparate and in order to model such effects authors have developed homogenisation based methods. Recently the Heterogeneous Multiscale Methods (HMM) have been employed to study the problem. This has allowed the effects of micro-EHL to be explored and coupled into the macro-scale EHL problem. Fundamental to this is the separation of scales and periodicity applied at to simulations describing surface topography. de Boer [1] outlines a method for coupling the scales of the problem using Moving Least Squares metamodels to calculate flow factors. This was further used to optimise surface topographical features to produce the minimum possible coefficient of friction in an EHL contact [2]. This research focuses on the metamodelling approach of [1, 2] to explore more complex 3D titled-pad bearing geometries than have previously been investigated. The means by which the scales of the problem are coupled is complicated by an increase in the number of design variables. Additionally the choice of Design of Experiments and how this evolves with the solution procedure is vital to the accuracy of the approach.
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- Åkesson, Susanne, et al.
(author)
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Evolution of chain migration in an aerial insectivorous bird, the common swift Apus apus
- 2020
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 74:10, s. 2377-2391
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Journal article (peer-reviewed)abstract
- Spectacular long-distance migration has evolved repeatedly in animals enabling exploration of resources separated in time and space. In birds, these patterns are largely driven by seasonality, cost of migration, and asymmetries in competition leading most often to leapfrog migration, where northern breeding populations winter furthest to the south. Here, we show that the highly aerial common swift Apus apus, spending the nonbreeding period on the wing, instead exhibits a rarely found chain migration pattern, where the most southern breeding populations in Europe migrate to wintering areas furthest to the south in Africa, whereas the northern populations winter to the north. The swifts concentrated in three major areas in sub-Saharan Africa during the nonbreeding period, with substantial overlap of nearby breeding populations. We found that the southern breeding swifts were larger, raised more young, and arrived to the wintering areas with higher seasonal variation in greenness (Normalized Difference Vegetation Index) earlier than the northern breeding swifts. This unusual chain migration pattern in common swifts is largely driven by differential annual timing and we suggest it evolves by prior occupancy and dominance by size in the breeding quarters and by prior occupancy combined with diffuse competition in the winter.
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