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The impact of various model formulations on model climate during boreal winter is studied using ensembles of seasonal integrations
for four different versions of the ECMWF NWP model. The model versions, cycles 36, 46, 48 and 12r1, differ primarily in the
representation of physical parametrization. In addition, higher vertical resolution was used for the 12r1 integrations. In
the more recent cycles (48 and 12r1) a strong systematic overestimation of zonal flow over the northeastern Pacific has been
dramatically reduced, contributing to a more realistic representation of the Pacific block. This improved representation of
blocking, particularly in cycle 12r1, is linked to a more efficient diabatic response of the model to the warm SSTs in the
western tropical Pacific. In contrast, over the Atlantic/European region a slight deterioration of blocking frequency in cycle
12r1 is associated with the strengthening of the Atlantic jet. The improvement in the Southern Hemisphere circulation, already
evident in cycle 46, is not seen in the Northern Hemisphere, so it is argued that the impact of radiation changes introduced
between cycle 36 and cycle 46 (inclusive) is influenced by seasonal cycle. A strong cooling of the southern (summer) polar
stratosphere has been steadily reduced and in cycle 12r1 is about half of that seen in cycle 36. A reduction of errors in
zonally averaged zonal wind and eddy kinetic energy is also clearly seen. In the tropics, the Hadley circulation has become
more intense with the later cycles. This is associated with an intensification of convective rainfall within relatively narrow
tropical convergence zones. Finally, it was found that the representation of interannual variations between strong positive
and negative ENSO-index winters was most successful in cycle 12r1.
Received: 30 November 1995 / Accepted: 13 July 1996 相似文献
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Luka Č. Popović 《New Astronomy Reviews》2012,56(2-3):74-91
It is now agreed that mergers play an essential role in the evolution of galaxies and therefore that mergers of supermassive black holes (SMBHs) must have been common. We see the consequences of past supermassive binary black holes (SMBs) in the light profiles of so-called ‘core ellipticals’ and a small number of SMBs have been detected. However, the evolution of SMBs is poorly understood. Theory predicts that SMBs should spend a substantial amount of time orbiting at velocities of a few thousand kilometers per second. If the SMBs are surrounded by gas observational effects might be expected from accretion onto one or both of the SMBHs. This could result in a binary Active Galactic Nucleus (AGN) system. Like a single AGN, such a system would emit a broad band electromagnetic spectrum and broad and narrow emission lines.The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emit very broad and complex line profiles, showing two displaced peaks, one blueshifted and one redshifted from the systemic velocity defined by the narrow lines, or a single such peak. It has been proposed that such line shapes could indicate an SMB system. We discuss here how the presence of an SMB will affect the BLRs of AGNs and what the observational consequences might be.We review previous claims of SMBs based on broad line profiles and find that they may have non-SMB explanations as a consequence of a complex BLR structure. Because of these effects it is very hard to put limits on the number of SMBs from broad line profiles. It is still possible, however, that unusual broad line profiles in combination with other observational effects (line ratios, quasi-periodical oscillations, spectropolarimetry, etc.) could be used for SMBs detection.Some narrow lines (e.g., [O III]) in some AGNs show a double-peaked profile. Such profiles can be caused by streams in the Narrow Line Region (NLR), but may also indicate the presence of a kilo-parsec scale mergers. A few objects indicated as double-peaked narrow line emitters are confirmed as kpc-scale margers, but double-peaked narrow line profiles are mostly caused by the complex NLR geometry.We briefly discuss the expected line profile of broad Fe Kα that probably originated in the accretion disk(s) around SMBs. This line may also be very complex and indicate the complex disk geometry or/and an SMB presence.Finally we consider rare configurations where a SMB system might be gravitationally lensed by a foreground galaxy, and discuss the expected line profiles in these systems. 相似文献
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Sublethal and lethal effects of biocide Slimicide C-30 on the developmental stages of mussels Mytilus galloprovincialis and juvenile and adult mysid Leptomysis mediterranea were studied.Biocide at a concentration as low as 0.02 mg l?1 caused an incipient effect in the embryonic development of mussels where a decreased number of normally developed larvae from eggs was evident. Slimicide C-30 effective concentration (EC 50/96) was 0.07 mg l?1.In the mysids, the median lethal concentration (96 h LC50) was 0.11 mg l?1.Previous incubation of Slimicide C-30 at 38°C affected a small delay in mortality time (LT50) but did not cause marked change in the acute toxicity to mysids. 相似文献
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The climate and variability of seasonal ensemble integrations, made with a recent version of ECMWF model (used for ERA-40 production) at relatively high horizontal resolution (TL159), have been studied for the 10-year period, 1980–1989. The model systematic error over the Atlantic-European region has been substantially improved when compared with the earlier model versions (e.g. from the PROVOST and AMIP-2 projects). However, it has worsened over the Pacific-North American region. This systematic error reduces the amplitude of planetary waves and has a negative impact on intraseasonal variability and predictability of the PNA mode. The signal-to-noise analysis yields results similar to earlier model versions: only during relatively strong ENSO events do some parts of the extratropics exhibit potential predictability. For precipitation, there is more disagreement between observed and model climatologies over sea than over land, but interannual variations over many parts of the tropical ocean are reasonably well represented. The south Asian monsoon in the model is severely weakened when compared to observations; this is seen in both poor climatology and interannual variability. Overall, comparing the ERA-40 model with earlier versions, there seems to be a balance between model improvements and deteriorations due to systematic errors. For the seasonal time-scale predictability, it is not clear that this model cycle constitutes an advantage over the earlier versions. Therefore, since it is not always possible to achieve distinct improvements in model climate and variability, a careful and detailed strategy ought to be considered when introducing a new model version for operational seasonal forecasting. 相似文献
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Saša Simić Luka Č. Popović Michael I. Andersen Lise Christensen 《Astrophysics and Space Science》2007,309(1-4):173-177
In this paper we investigate the variability of the gamma ray burst light curve. It is generally known that this fluctuation
arise in the second phase of a GRB event, when two shock waves of different Lorentz factors collide. This is so called internal
shock scenario. We have developed a simple model which includes dynamical and radiating part, to simulate shock wave evolution
and collision. By specifying the model parameters, we show that this scenario could be used to describe variability of GRB
light curve. We then use the model to simulate peeks in several different long GRB events from the BATSE database, which show
us that some of the basic parameters have a very narrow range of values.
相似文献
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Pavel Pajdušák Jaroslava Plomerová Vladislav Babuška Reviewer Č. Tomek 《Studia Geophysica et Geodaetica》1989,33(1):11-21
Summary Directionally independent average P residuals computed for waves of teleseismic events arriving under various azimuths and
incidence angles provided the basis for estimating the lithosphere thickness beneath the Carpathians and their surroundings.
A thin lithosphere (60–80 km) was determined for the Pannonian Basin and the Transylvanian Basin, the thickest lithosphere(about 180 km) beneath the South Carpathians at the contact with the Moesian Platform. In other parts of the Carpathian belt the lithosphere
thickens beneath the outer parts towards the SW margin of the East-European and the Moldavian Platforms. The lithosphere thicknesses
derived from P residuals correlate well with the magnetotelluric determinations of a layer of increased electrical conductivity
in the upper mantle.
Резюме Осре?rt;ненные временные невязкu Р волн, незaвuсuмые оm нanрaвленuя u рaссчumaнные ?rt;ля у?rt;aленных землеmрясенuŭ uз волн, nрuхо?rt;ящuх nо?rt; рaзнымu aзuмуmaмu u у лaмu na?rt;енuя, ?rt;aюm основaнuе ?rt;ля оnре?rt;еленuя мощносmu лumосферы Кaрnam u uх окресmносmеŭ. Тонкaя лumосферa(60–80 км) оnре?rt;еленa ?rt;ля Пaннонско о u Трaнсuльвaнско о бaссеŭнов, a сaмaя мощнaя лumосферa(около 180 км) нaхо?rt;umся nо?rt; Южнымu Кaрnamaмu. В ?rt;ру uх чaсmях Кaрnamско о nоясa мощносmь лumосферы нaрaсmaеm во внешнuх зонaх в нanрaвленuu к ю о-зana?rt;ноŭ окрauне Восmочно-Евроnеŭскоŭ u Мол?rt;aвскоŭ nлamформ. Нaблю?rt;aеmся хорошaя корреляцuя мощносmu лumосферы, оnре?rt;еленноŭ нa основе невязок временu Р волн, с мa нumоmеллурuческuмu ?rt;aннымu nо лубuне слоя nовышенноŭ элекmроnрово?rt;uмосmu в верхнеŭ мaнmuu.相似文献
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The interaction of selenium with mercury was studied in the shrimp Palaemon elegans. The release of 203HgCl2 (5·0 μg Hg per gramme body weight) from shrimp pretreated with selenium (SeO2 doses of 1·97, 3·95 and 7·90 μg Se per gramme fresh weight) was significantly decreased compared with the control group to which only 5·0 μg Hg/g had been administered.In the presence of HgCl2 (5·0 μg Hg per gramme fresh weight) the release of 75Se also diminished significantly at the higher stable Se pretreated dose (7·90 μg Se/g) while, at a lower selenium concentration, the release was not statistically different. Analyses for stable Hg and Se confirmed the decrease in rate of selenium loss in the presence of mercury which had been demonstrated with radiotracers.A dose of 7·9 μg Se per gramme fresh weight injected 12 h before exposure of the shrimp to the various mercuric chloride solutions did not produce a significant difference in the 24 h LC50 compared with the group not pretreated with selenium. However, during exposure to mercury at 3·8 mg/litre, the median lethal time (LT50) for the shrimp pretreated for 4 days with sublethal selenium (6·9 and 10·5 mg Se/litre) was delayed (19·2 and 33·2 h) compared with the group which was not pretreated. The results are discussed in relation to the role of selenium in the acutely toxic effects of inorganic mercury. 相似文献
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