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Sökning: WFRF:(Pemberton L.)

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  • Eriksson, L.E.B., 1970-, et al. (författare)
  • Evaluation of multi-polarization SAR data at L-, C- and X-band for sea-ice monitoring in the Baltic Sea
  • 2010
  • Ingår i: Proceedings of the ESA Living Planet Symposium 2010, 28 June - 2 July 2010, Bergen, Norway. ; ESA SP-686
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • SAR data from the satellites ALOS, Envisat, Radarsat-2 and TerraSAR-X were compared in order to evaluate their usefulness for sea ice monitoring in the Baltic Sea. Different advantages and disadvantages were identified for the SAR systems and imaging modes. It has been shown that cross-polarized data improve the discrimination between sea-ice and open water. Another observation is that it is easier to identify ice ridges in L-band data than in images from shorter wavelengths. The information content of X- and C-band images is largely equivalent, whereas L-band data provide complementary information. L-band SAR also seems to be less sensitive to wet snow cover on the ice.
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3.
  • Eriksson, L.E.B., 1970-, et al. (författare)
  • Evaluation of new spaceborne SAR sensors for sea-ice monitoring in the Baltic Sea
  • 2010
  • Ingår i: Canadian Journal of Remote Sensing. - 0703-8992. ; 36:1, s. 56-73
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, synthetic aperture radar (SAR) data from the Advanced Land Observing Satellite (ALOS) and the Envisat, RADARSAT-2, and TerraSAR-X satellites were compared to evaluate their usefulness for sea-ice monitoring in the Baltic Sea. Radar signature characteristics at different frequencies, polarizations, and spatial resolutions are presented for three examples from 2009. C-band like-polarization data, which have been used for operational sea-ice mapping since the early 1990s, serve as a reference. Advantages and disadvantages were identified for the different SAR systems and imaging modes. One conclusion is that cross-polarized data improve the discrimination between sea ice and open water. Another observation is that it is easier to identify ice ridges in L-band data than in images from shorter wavelengths. The information content of X- and C-band images is largely equivalent, whereas L-band data provide complementary information. L-band SAR also seems to be less sensitive to wet snow cover on the ice.
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  • Hansson, Bengt, et al. (författare)
  • No evidence for inbreeding avoidance in a great reed warbler population
  • 2007
  • Ingår i: Behavioral Ecology. - Oxford University Press. - 1045-2249 .- 1465-7279. ; 18:1, s. 157-164
  • Tidskriftsartikel (refereegranskat)abstract
    • Inbreeding depression may drive the evolution of inbreeding avoidance through dispersal and mate choice. In birds, many species show female-biased dispersal, which is an effective inbreeding avoidance mechanism. In contrast, there is scarce evidence in birds for kin discriminative mate choice, which may, at least partly, reflect difficulties detecting it. First, kin discrimination may be realized as dispersal, and this is difficult to distinguish from other causes of dispersal. Second, even within small, isolated populations, it is often difficult to determine the potential candidates available to a female when choosing a mate. We sought evidence for inbreeding avoidance via kin discrimination in a breeding population of great reed warblers (Acrocephalus arundinaceus) studied over 17 years. Inbreeding depression is strong in the population, suggesting that it would be adaptive to avoid relatives as mates. Detailed data on timing of settlement and mate search movements made it possible to identify candidate mates for each female, and long-term pedigrees and resolved parentage enabled us to estimate relatedness between females and their candidate mates. We found no evidence for kin discrimination: mate choice was random with respect to relatedness when all mate-choice events were considered, and, after correction for multiple tests, also in all breeding years. We suggest that dispersal is a sufficient inbreeding avoidance mechanism in most situations, although the lack of kin discriminative mate choice has negative consequences for some females, because they end up mating with closely related males that lowers their fitness.
8.
  • Jahn, A., et al. (författare)
  • Arctic Ocean freshwater : How robust are model simulations?
  • 2012
  • Ingår i: Journal of Geophysical Research. - 0148-0227. ; 117, s. C00D16
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust. Citation: Jahn, A., et al. (2012), Arctic Ocean freshwater: How robust are model simulations?, J. Geophys. Res., 117, C00D16, doi: 10.1029/2012JC007907.
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