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Sensitivity of the Northern Hemisphere circulation to North Atlantic SSTs in the ARPÈGE Climate AGCM
In order to determine the response of the atmosphere to winter sea surface temperature (SST) anomalies in the North Atlantic
area, we carried out ensemble runs of 20 years, forced with constant, perturbed, SST patterns using the climate version of
the ARPèGE AGCM, at T42 resolution. A Monte Carlo technique was applied, in such a way that the control experiment, forced
with observed climatological temperatures, and the four scenario experiments, forced with perturbed SSTs are equivalent to
a length of 20 independent winters. Four anomalous winter North Atlantic sea surface temperature (SST) fields have been constructed
by considering the observed SST variability in the main basins, namely the Labrador Sea and the Greenland Sea. Two patterns
are of the `seesaw' type, while the two others have same the polarity in both basins. The patterns have been reinforced by
a factor of 5–6 compared to presently observed multi-annual anomalies, in order to get SST anomalies which may have occurred
during periods of the Little Ice Age. The differences between each of the four winter simulations with perturbed SSTs and
the control run are analyzed in terms of tropospheric thickness, mean-sea-level pressure and storm activity. The `seesaw'
type patterns give a weaker response in the tropospheric thickness fields than the two others. This is expected from simple
considerations. In the mean circulation and synoptic activity, it appears that the Labrador Sea SST is important in determining
the atmospheric response. This is probably due to enhanced temperature gradients east of New Foundland which enhances the
storm activity.
Received: 23 September 1998 / Accepted: 17 November 1999 相似文献
2.
Characteristics of Danish estuaries 总被引：2，自引：0，他引：2
Daniel J. Conley Hanne Kaas Flemming Møhlenberg Bjarke Rasmussen Jørgen Windolf 《Estuaries and Coasts》2000,23(6):820-837
We review various aspects of the structure and functioning of Danish estuaries from data collected by the National Monitoring Program and from information in published sources. We present data on the physical, chemical, and biological characteristics of estuaries in Denmark, we evaluate the functioning of these systems as filters and transformers of nutrients and we evaluate the outlook for Danish estuaries in the future. Danish estuarine systems are for the most part shallow (<3 m deep), have short residence times, and tend to be heavily loaded with nutrients primarily from agricultural sources. Total average loads from land per unit watershed area are 112 kg P km?2 yr?1 and 2,400 kg N km?2 yr?1 during the period 1989–1995. The total phosphorus (TP) load in estuaries has been significantly reduced over the last decade, following implementation of the 1987 Action Plan for the Aquatic Environment (Vandmiljøplan in Danish) that prescribed that nitrogen loads to the total aquatic environment should be reduced by 50% and phosphorus loads by 80%. Reductions in the total nitrogen (TN) load have been more modest. Nutrient loading is one of the primary determinants of estuarine nutrient concentration with 70% of the annual variation in TN concentration and 55% of the annual variation in TP concentration explained by variation in the load. Many Danish estuaries have rich communities of macrophytes and benthic filter feeders, such asMytlis edulis andCiona intestinalis, that can control water column chlorophyll concentrations by their filter feeding activities. Many of the estuaries experience hypoxia and anoxia, especially during warm and calm summer months. Further reductions in nutrient loading are expected following implementation of the Action Plan for the Aquatic Environment II, with predicted improvements in oxygen concentrations and in the functioning of these shallow, dynamic estuarine systems. 相似文献
3.
Dag Eigil Ormaasen 《Lithos》1977,10(4):291-310
The Hopen massif, intrusive age 1900 m.y., exposed area 15 km2, in the Lofoten-Vesterålen granulite facies province has the mineral assemblages: (1) mesoperthite+plagioclase (An7–20)+quartz+clinopyroxene (Di20–25)+orthopyroxene En15–25+opaques±minor amphibole±minor biotite; (2) mesoperthite+plagioclase (An <2)+quartz+clinopyroxene (Di <10)+olivine Fe lt;5)+opaques. By using mineral and whole rock analyses, the crystallization conditions were estimated to be 1000°C, 12 kb load pressure and an oxygen fugacity approximately corresponding to the WM buffer. Rocks with the assemblage of type (2) contain secondary orthoferrosilite (Fe0.90–0.95Mn0.04–0.07Mg0.01Ca0.01)2Si2O6, generated by reactions involving fayalite, magnetite and quartz at 800°C, 10kb load pressure and at oxygen fugacities approaching QFM buffer conditions. Subsequent to a crustal thickening, the mangeritic rocks in Lofoten-Vesterålen were emplaced in a tensional environment comparable with modern continental rifts. A ‘gabbro pillow’ magma chamber at the crustal base is proposed as parental magma for the mangeritic rocks, of which the Hopen massif represents a late differentiation. 相似文献
4.
Northeast Atlantic winter storminess is analysed for the period 1875–1995 using a new dataset consisting of multi-daily mean
sea level pressure observations from a selected set of stations in the northeast Atlantic. An analysis of storminess is presented,
based on the high-pass filtered signal from these observations, from which selected percentiles are calculated for each winter.
This method avoids potential inhomogeneity problems (artificial trends or jumps). Our finding is an increase, however not
a dramatic one, during the past 2–3 decades in the northeasternmost part of the storm track, but the dominant features are
inter-annual and decadal variations. Furthermore, the variations in storminess are found to be statistically linked to low-frequency
circulation variations represented by the winter average of the MSL pressure field over the North Atlantic. It is argued that
the existence of this link could have dynamical consequences for the response of the atmosphere to external forcing.
Received: 20 May 1997 / Accepted: 13 January 1998 相似文献
5.
We review literature on high voltage transmission lines and their effect on wild reindeer ( Rangifer tarandus ) migration patterns and area use. We conclude that reliable knowledge is lacking on the effects of transmission lines on reindeer ecology. This condition relates to the lack of long-term monitoring of reindeer migration patterns in relation to existing lines. It is also related to the fact that nothing is known about hearing in reindeer (or any other deer species in Norway) in relation to transmission line noise, which is considered an obstacle for migrating reindeer.
We then outline a research programme that includes a laboratory study to determine the audiogram in reindeer and two field studies to examine the proximate effects of transmission lines - independently as well as combined with ambient environmental variables - on reindeer behaviour. The audiogram in two yearling male reindeer has been determined; this part of the study will be completed this year with the determination of a corresponding audiogram in two female yearlings. The behaviour study of domestic reindeer under high voltage transmission lines was completed in September 1999. The behaviour study of wild reindeer in the area crossed by a 420 kV power line will continue this year and its completion is anticipated in 2001. 相似文献
We then outline a research programme that includes a laboratory study to determine the audiogram in reindeer and two field studies to examine the proximate effects of transmission lines - independently as well as combined with ambient environmental variables - on reindeer behaviour. The audiogram in two yearling male reindeer has been determined; this part of the study will be completed this year with the determination of a corresponding audiogram in two female yearlings. The behaviour study of domestic reindeer under high voltage transmission lines was completed in September 1999. The behaviour study of wild reindeer in the area crossed by a 420 kV power line will continue this year and its completion is anticipated in 2001. 相似文献
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7.
Tropical cyclones in enhanced resolution CMIP5 experiments 总被引：1，自引：0，他引：1
This study investigates the possible effects of global warming on tropical cyclone (TC) activity. The study is conducted using the coupled ocean–atmosphere global climate model EC-Earth configured at a relatively high resolution (T159 with 62 vertical levels), which is integrated following the CMIP5 protocol. By considering the late twentieth century (1979–2009) in the historical simulation and the twenty-first century end (2070–2100) in the RCP4.5 and RCP8.5 scenarios, significant future annual mean frequency decreases are found globally and in both hemispheres, accompanied by significant mean lifetime decreases and significant intensity increases, the latter being found through several different measures (but with caveats). In addition, the relatively novel aspect of simulating TCs of the past (1900–1930) is studied to further assess the robustness of the climate change results. These results suggest that TCs in the early twentieth century were more frequent in the southern hemisphere and dissipated more energy in the southern hemisphere and the South Indian Ocean. Although some model biases are present and the coarse model resolution prevents intense TCs in being simulated, reasonable TC simulation skill for other metrics (e.g., TC genesis, frequency of occurrence) is found when validated against present day observations. Thus the model displays an acceptable ability to connect TC climatology with the larger scale circulation. 相似文献
8.
Oliver Krueger Frauke Feser Lars Bärring Eigil Kaas Torben Schmith Heikki Tuomenvirta Hans von Storch 《Climate Dynamics》2014,42(3-4):1127-1128
The main subject of this article is to comment on the issue of storminess trends derived from the twentieth century reanalysis (20CR) and from observations in the North Atlantic region written about in Wang et al. (Clim Dyn 40(11–12):2775–2800, 2012). The statement that the 20CR estimates would be consistent with storminess derived from pressure-based proxies does not hold for the time prior to 1950. 相似文献
9.
Ringgaard Ida Margrethe Yang Shuting Kaas Eigil Christensen Jens Hesselbjerg 《Climate Dynamics》2020,54(7):3323-3338
Climate Dynamics - The potential link between decreasing Barents-Kara sea ice and cold winters in Europe is investigated using the enhanced resolution (horizontal atmospheric resolution of $$\sim... 相似文献
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