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[en] Connections between wildfires and modes of variability in climate are sought as a means for predicting fire activity on interannual to multi-decadal timescales. Several fire drivers, such as temperature and local drought index, have been shown to vary on these timescales, and analysis of tree-ring data suggests covariance between fires and climate oscillation indices in some regions. However, the shortness of the satellite record of global fire events limits investigations on larger spatial scales. Here we explore the interplay between climate variability and wildfire emissions with the preindustrial long control numerical experiments and historical ensembles of CESM1 and the NOAA/GFDL ESM2Mb. We find that interannual variability in fires is underpredicted in both Earth System models (ESMs) compared to present day fire emission inventories. Modeled fire emissions respond to the El Niño/southern oscillation (ENSO) and Pacific decadal oscillation (PDO) with increases in southeast Asia and boreal North America emissions, and decreases in southern North America and Sahel emissions, during the ENSO warm phase in both ESMs, and the PDO warm phase in CESM1. Additionally, CESM1 produces decreases in boreal northern hemisphere fire emissions for the warm phase of the Atlantic Meridional Oscillation. Through analysis of the long control simulations, we show that the 20th century trends in both ESMs are statistically significant, meaning that the signal of anthropogenic activity on fire emissions over this time period is detectable above the annual to decadal timescale noise. However, the trends simulated by the two ESMs are of opposite sign (CESM1 decreasing, ESM2Mb increasing), highlighting the need for improved understanding, proxy observations, and modeling to resolve this discrepancy. (letter)
[en] The mosaic of the existing vegetation cover of Yakutia in the Late Pleistocene is due to a combination of arid climate, as well as because of permafrost spreading and frequent fires. The combination of these factors creates necessary conditions for the formation of ecotone natural systems represented by dissipative plant communities. Sparse plant communities are characterized by the absence or weak expression of phytocenotic bonds. Their formation occurs stochastically under the absolute influence of external factors and is genetically entirely dependent on the surrounding vegetation, which acts as a donor of patient and ruderal species. Such processes were characteristic of the Late Pleistocene ecosystems of the Northern Hemisphere. A low productivity of such biotopes did not allow them to act as the main pastures for the representatives of the mammoth megafauna, apart from the saiga and bighorn sheep, but contributed to the increase in the biodiversity of the late Pleistocene ecosystems. (paper)
[en] This study investigates the global response of the midlatitude atmospheric circulation to 1.5 and 2.0°C of warming using the HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) ensemble, with a focus on the winter season. Characterising and understanding this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to 1.5°C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks, and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5°C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equatorward intensification of the South Pacific jet. Signals that emerge under an additional 0.5°C of warming include a poleward shift of the North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, in western Europe, and on the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2°C warmer world, with exceptionally dry decades becoming 5 times more likely.
[en] About 2500 deg2 of sky south of declination -250 and/or near the Galactic Plane were surveyed for bright outer solar system objects. This survey is one of the first large-scale southern sky and Galactic Plane surveys to detect dwarf planets and other bright Kuiper Belt Objects in the trans-Neptunian region. The survey was able to obtain a limiting R-band magnitude of 21.6. In all, 18 outer solar system objects were detected, including Pluto which was detected near the Galactic center using optimal image subtraction techniques to remove the high stellar density background. Fourteen of the detections were previously unknown trans-Neptunian objects, demonstrating that the southern sky had not been well searched to date for bright outer solar system objects. Assuming moderate albedos, several of the new discoveries from this survey could be in hydrostatic equilibrium and thus could be considered dwarf planets. Combining this survey with previous surveys from the northern hemisphere suggests that the Kuiper Belt is nearly complete to around 21st magnitude in the R band. All the main dynamical classes in the Kuiper Belt are occupied by at least one dwarf-planet-sized object. The 3:2 Neptune resonance, which is the innermost well-populated Neptune resonance, has several large objects while the main outer Neptune resonances such as the 5:3, 7:4, 2:1, and 5:2 do not appear to have any large objects. This indicates that the outer resonances are either significantly depleted in objects relative to the 3:2 resonance or have a significantly different assortment of objects than the 3:2 resonance. For the largest objects (H < 4.5 mag), the scattered disk population appears to have a few times more objects than the main Kuiper Belt (MKB) population, while the Sedna population could be several times more than that of the MKB.
[en] Complete text of publication follows. The 25 year TOMS ozone data series (1978 - 2005) in the Northern Hemisphere is investigated with respect to longitudinal and latitudinal dependant trends. Sinusoidal structures in the longitudinal trend behaviour are interpreted in terms of planetary wave activity. This is in agreement with an observed trend in the amplitudes of the planetary waves with zonal wave number 1 and 2. These trends are found to clearly vary with month and latitude. This effect is used to separate chemically and dynamically induced ozone trends. It is discussed how the background ozone concentration in midlatitudes might be influenced by streamer events caused by breaking planetary waves.
[en] Complete text of publication follows. Kozyrev postulated absolute difference of past and future, right and left rotation and grounded causal or asymmetrical mechanics, according to which in a rotating system appears an additional asymmetrical force Fasym. Laboratory measurements with rotated bodies proved that asymmetric force carry energy and angular moment, but no momentum. It means, that in rapidly rotated parts of a body asymmetrical force directed along axes of rotation, in slowly rotating parts (near the axes) - in opposite directions to yield null result after summation. Applying the result to rotated planets, one can expect that at some latitude asymmetrical force pass through zero changing the sign. Direct Kozyrev's measurements at northern latitudes φ from 45 deg to 84 deg proved that causal force is directed along Earth rotation axis: to the North for φ<73 deg and to South for φ>73 deg, The change of the direction occur at the distance 1860 km from the Earth's axes. The magnitude of causal force has order (1-5)x10-5 of gravity force. Liquid core has radius 3490 km, then at the distances from the Earth's axes more than 1860 km asymmetrical force is directed to the North, in the nearer parts to the Earth's axes, - to the South. As result, asymmetrical forces form a system of vortexes in meridian plains which in the near to axes region deflected by the internal solid core with radius 1220 km. Flow of matter in liquid core has radial (in cylindrical system) component directed to or from axes. The first (to axes) is transformed by Carioles force into the counter-clockwise (seeing to the Earth from North) circular currents, the second - into clockwise currents: two in Northern and two in Southern hemispheres. These currents (flow of matter) should be important for geomagnetic field generation, especially during epoch of small geomagnetic field and its reversal.
[en] Complete text of publication follows. The crustal magnetic field recorded on Mars during the Mars Global Surveyor mission reveals an hemispherical magnetic field pattern, with a maximum value of magnetic field intensity much larger in the Southern hemisphere than in the Northern hemisphere. Previously explored possible causes for this pattern include the influence of a hemispherical mantle convection pattern. In this presentation, we perform a systematic study of numerical models of rotating convection and dynamo action in fluid spheres (without an inner core). Our models have homogeneous buoyancy driving, yet they exhibit a transition to a strongly equator-asymmetric convection regime where one hemisphere becomes colder than the other, which we relate to the linear instability of equator-antisymmetric convection modes. We study the impact of this transition on the properties of heat transfer in rapidly rotating convection, and on the pattern of magnetic field as it would be seen on the planet's surface. We discuss the possible implications of our result on planetary dynamos.
[en] Correction to: Astrophys Space Sci https://doi.org/10.1007/s10509-019-3522-3 We would like to add the following sentence into the acknowledgement:Students of Horten Upper Secondary School (Horten Videregående Skole) B. Berg, Å. Hansli, V.H. Hatlo, M.B. Hjelmervik, C.T. Lavre, V. Moskvil, and V. Skui are acknowledged for taking part in observing eclipsing binary candidate TYC 2764-1997-1 star on the Nordic Optical Telescope.
[en] Global temperatures have undergone periods of enhanced warming and pauses over the last century, with greater variations at local scales due to internal variability of the climate system. Here we investigate the role of the North Atlantic Oscillation (NAO) in decadal temperature trends in the Northern Hemisphere for periods with large decadal NAO trends. Using a regression based technique we find a best estimate that trends in the NAO more than halved (reduced by 57%, 5%-95%: 47%-63%) the winter warming over the Northern Hemisphere extratropics (NH; 30N-90N) from 1920-1971 and account for 45% (± 14%) of the warming there from 1963-1995, with larger impacts on regional scales. Over the period leading into the so-called warming hiatus, 1989-2013, the NAO reduced NH winter warming to around one quarter (24%; 19%-31%) of what it would have been, and caused large negative regional trends, for example, in Northern Eurasia. Warming is more spatially uniform across the Northern Hemisphere after removing the NAO influence in winter, and agreement with multi-model mean simulated trends improves. The impact of the summer NAO is much weaker, but still discernible over Europe, North America and Greenland, with the downward trend in the summer NAO from 1988-2012 reducing warming by about a third in Northern Europe and a half in North America. A composite analysis using CMIP5 control runs suggests that the ocean response to prolonged NAO trends may increase the influence of decadal NAO trends compared to estimates based on interannual regressions, particularly in the Arctic. Results imply that the long-term NAO trends over the 20. century alternately masked or enhanced anthropogenic warming, and will continue to temporarily offset or enhance its effects in the future. (authors)
[en] Integration of markers of oxidative stress, from the subcellular to the leaf and needle level, proved to be a useful tool for the differential diagnosis and validation of ozone injury. - Ozone injury to natural vegetation is being increasingly surveyed throughout the northern hemisphere. There exists a growing list of species showing visible 'ozone-like' symptoms which needs to be validated. This study presents the results from a test survey of ozone injury to forest vegetation in the light exposed sites of five Swiss level II plots, for the new ICP-Forests protocol. With AOT40 from 14 to 28 ppm·h in 2000, ten out of 49 woody plant species displayed typical symptoms, and four showed untypical symptoms. Symptom origin was investigated in nine and validated in seven species, using morphological, histological and cellular markers of oxidative stress and ozone-induced plant response. Independent of taxonomic position, ozone effects were characterized by the induction of oxidative stress in the mesophyll resulting in discrete and light-dependent hypersensitive-like responses and in accelerated cell senescence. The presented combination of cellular and morphological markers allows differential diagnosis of visible ozone injury