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21.
22.
Regional climate change patterns identified by cluster analysis 总被引:1,自引:0,他引:1
Climate change caused by anthropogenic greenhouse emissions leads to impacts on a global and a regional scale. A quantitative
picture of the projected changes on a regional scale can help to decide on appropriate mitigation and adaptation measures.
In the past, regional climate change results have often been presented on rectangular areas. But climate is not bound to a
rectangular shape and each climate variable shows a distinct pattern of change. Therefore, the regions over which the simulated
climate change results are aggregated should be based on the variable(s) of interest, on current mean climate as well as on
the projected future changes. A cluster analysis algorithm is used here to define regions encompassing a similar mean climate
and similar projected changes. The number and the size of the regions depend on the variable(s) of interest, the local climate
pattern and on the uncertainty introduced by model disagreement. The new regions defined by the cluster analysis algorithm
include information about regional climatic features which can be of a rather small scale. Comparing the regions used so far
for large scale regional climate change studies and the new regions it can be shown that the spacial uncertainty of the projected
changes of different climate variables is reduced significantly, i.e. both the mean climate and the expected changes are more
consistent within one region and therefore more representative for local impacts. 相似文献
23.
Gerhard Krinner Annette Rinke Klaus Dethloff Irina V. Gorodetskaya 《Climate Dynamics》2010,35(4):619-633
This paper describes atmospheric general circulation model climate change experiments in which the Arctic sea-ice thickness
is either fixed to 3 m or somewhat more realistically parameterized in order to take into account essentially the spatial
variability of Arctic sea-ice thickness, which is, to a first approximation, a function of ice type (perennial or seasonal).
It is shown that, both at present and at the end of the twenty-first century (under the SRES-A1B greenhouse gas scenario),
the impact of a variable sea-ice thickness compared to a uniform value is essentially limited to the cold seasons and the
lower troposphere. However, because first-year ice is scarce in the Central Arctic today, but not under SRES-A1B conditions
at the end of the twenty-first century, and because the impact of a sea-ice thickness reduction can be masked by changes of
the open water fraction, the spatial and temporal patterns of the effect of sea-ice thinning on the atmosphere differ between
the two periods considered. As a consequence, not only the climate simulated at a given period, but also the simulated Arctic
climate change over the twenty-first century is affected by the way sea-ice thickness is prescribed. 相似文献
24.
25.
Victor G. Kornilov Vladimir M. Lipunov Evgeny S. Gorbovskoy Aleksander A. Belinski Dmitry A. Kuvshinov Natalia V. Tyurina Nikolai I. Shatsky Anatoly V. Sankovich Aleksander V. Krylov Pavel V. Balanutsa Vadim V. Chazov Artem S. Kuznetsov Dmitry S. Zimnuhov Victor A. Senik Andrey G. Tlatov Aleksander V. Parkhomenko Denis V. Dormidontov Vadim V. Krushinsky Ivan S. Zalozhnyh Aleksander A. Popov Sergey A. Yazev Nikolai M. Budnev Kirill I. Ivanov Evgeny N. Konstantinov Oleg A. Gress Oleg V. Chvalaev Vladimir V. Yurkov Yury P. Sergienko Irina P. Kudelina 《Experimental Astronomy》2012,33(1):173-196
Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER?II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6?h. A further expansion of the network is considered. 相似文献
26.
Sophie GODIN-BEEKMANN Irina PETROPAVLOSKIKH Stefan REIS Paul NEWMAN Wolfgang STEINBRECHT Markus REX Michelle L. SANTEE Richard S. ECKMAN Xiangdong ZHENG Matthew B. TULLY David S. STEVENSON Paul YOUNG John PYLE Mark WEBER Johanna TAMMINEN Gina MILLS Alkis F. BAIS Clare HEAVISIDE Christos ZEREFOS 《大气科学进展》2017,34(3):283-288
<正>1.Overview The 2016 Quadrennial Ozone Symposium(QOS-2016)was held on 4–9 September 2016 in Edinburgh,UK.The Symposium was organized by the International Ozone Commission(IO3C),the NERC Centre for EcologyHydrology and the University of Edinburgh,and was co-sponsored by the International Union of Geodesy and Geophysics,the International Association of Meteorology and Atmospheric 相似文献
27.
Wolfram Kloppmann Haim Chikurel Géraldine Picot Joseph Guttman Marie Pettenati Avi Aharoni Catherine Guerrot Romain Millot Irina Gaus Thomas Wintgens 《Applied Geochemistry》2009
Boron and Li isotopes have been tested as environmental tracers of treated sewage injected into a sandy aquifer (Shafdan reclamation project, Israel). During a 38 days injection test in a newly dug injection well, a conservative artificial tracer (Br−) was monitored together with δ11B and δ7Li in the injectate, in the unsaturated soil zone (porous cup) and an observation well in the aquifer. In spite of B and Li concentrations in the injectate close to background values, significant shifts of the isotope signatures could be observed over the duration of the injection test. Boron isotope ratios show a breakthrough curve delayed with respect to Br− breakthrough due to some reversible sorption on the aquifer material. No isotope fractionation was observed in the unsaturated or the saturated zone so that B isotopes can be considered as conservative in the investigated part of the aquifer system. Lithium isotopes are strongly fractionated, probably due to sorption processes. Lithium concentrations point to a Li sink in the system, δ7Li values vary strongly with a tendency of 7Li depletion in the liquid phase over the duration of the experiment. This is opposite to the expected preferential sorption of 6Li onto clay minerals. Boron isotopes reveals a valuable tracer of artificial recharge of freshwaters derived from treated sewage, both for short term tracer tests and for long-term monitoring of artificial recharge, even if in aquifers with higher clay contents, sorption-linked isotope fractionation cannot be excluded. More data are needed on Li isotope fractionation in natural groundwater systems to assess the potential of this tracer as monitoring tool. 相似文献
28.
Irina G. Kudintseva Alexander P. Nickolaenko Masashi Hayakawa 《Surveys in Geophysics》2010,31(4):427-448
We describe the space–time distribution of the pulsed electric field in the middle atmosphere above a positive Γ-shaped lightning
stroke. The channel of such a discharge contains a vertical and a horizontal section. The current wave moves initially vertically
and then turns horizontally so that radiation appears from the vertical electric dipole followed by that from the horizontal
dipole. Combined with reflection from the perfectly conducting ground, the source provides three subsequent pulses in the
atmosphere, with the lag being determined by the finite velocity of the current wave in the Γ-shaped stroke. The pulses are
reproduced by reflections from the air-ground and the air-ionosphere interfaces and the waveform resembles the M-component,
which is often noted in the negative strokes (e.g. Yashunin et al., J Geophys Res 112:D10109, 2007). The non-stationary fine structure appears in the spatial distribution of electric field, which persists for 2 ms or even
more and exceeds the runaway electron threshold. Estimates support the idea of free electron bunching in the mesosphere by
the pulsed electric field. Focusing may occur about 10 km away from the point of electron- field interaction; it is delayed
by a few ms from the moment of interaction. The data presented might be helpful in realistic modeling of the red sprite formation. 相似文献
29.
The relative abundance of the different picoplankton components (eukaryotic picophytoplankton (Peuk), picocyanobacteria (Pcy) and bacterioplankton), and their relationships with the lake conditions were studied in three types of shallow lakes from the Pampa Plain (Argentina) that differ in their optical properties: clear-vegetated, phytoplankton-turbid and inorganic-turbid. All the selected lakes, but one, are characterized by their different alternative steady state (clear-vegetated and phytoplankton-turbid water phases) following the model proposed by Scheffer et al. (1993).Autotrophic and heterotrophic picoplankton abundances were analyzed seasonally in relation to environmental variables. All the lakes presented high concentrations of total nitrogen (TN) (>229 μg L−1), total phosphorus (TP) (>46 μg L−1) and dissolved organic carbon (DOC) (>13.7 mg L−1). Clear-vegetated lakes were characterized by vertical diffuse PAR (photosynthetic active radiation) attenuation coefficient (kdPAR) lower than 11 m−1, whereas inorganic-turbid lake always showed values higher than 21.1 m−1. The euphotic zone depth (Z1%) was wider in clear-vegetated lakes (40–140 cm) and thinner in the inorganic-turbid (10–20 cm). The phytoplankton-turbid lakes presented a wide range in the values of these variables (kdPAR: 5.2–35.8 m−1; Z1%: 10–90 cm). Phytoplankton chlorophyll-a (Chl-a) strongly differed, ranging from 1.6 to 334.6 μg L−1. Picophytoplankton was mainly represented by phycocianine-rich (PC-rich) Pcy in all cases, dominating over Peuk algae. The total and relative abundances of eukaryotic picophytoplankton, Pcy and bacterioplankton, as well as the size structure of the phytoplankton community differed among the water bodies. In general, clear-vegetated water bodies exhibited similar abiotic characteristics, picophytoplankton/bacterioplankton ratios, and phytoplankton size structure. Contrarily, no clear trend was identified for the group of turbid lakes. The contrasting results obtained for the importance of the picoplankton components in phytoplankton-turbid shallow lakes evidence that the availability of the energetical and nutrient resources cannot be solely considered to predict their relative importance in this type of shallow lake. 相似文献
30.
Irina Gaus 《Hydrogeology Journal》2000,8(2):218-229
Pesticides are a potential threat to the quality of extracted groundwater when the water-supply area is used for agricultural
activities. This problem is discussed for the water-supply area of Sint-Jansteen, The Netherlands, where measured pesticide
concentrations in the extracted water regularly exceed EU limits (0.1 μg/L). Groundwater samples taken from the aquifer within
the water-supply area show low contamination, but samples taken from the extracted water occasionally contain pesticides,
making the water inadequate for drinking-water purposes. The more intense contamination of the extracted water is caused by
the change in the natural groundwater flow pattern near the extraction wells. In this area, pesticide use cannot be avoided
easily, and an approach is given to differentiate pesticide use in the area according to expected travel time toward the wells
and the chemical characteristics of the pesticides. A groundwater flow model for the area is developed and the effects of
groundwater extraction on the natural flow pattern are evaluated. Using particle tracking, the travel-time zones are determined.
Combining these results and the degradation behavior of certain pesticides led to an optimal scheme to integrate agricultural
activities and groundwater extraction in the area. This is illustrated for five different types of pesticides (atrazine, simazine,
bentazone, MCPA, and mecoprop).
Received, October 1998/Revised, July 1999, September 1999/Accepted, November 1999 相似文献