对流有效位能垂直分布作用的评价     

Blan.  DO 彭治班 《气象科技》2000,28(2):34-40

对流有效位能（ＣＡＰＥ）与评价大气对流潜力的标准的不稳定指数,例如抬升指数（ＬＩ）,只有中等程度的相关,这是由于ＬＩ仅反映单层的浮力,而ＣＡＰＥ反映了积分厚度和浮力。将ＣＡＰＥ值降以积分厚度,使其正规化,得到一个指数（ＮＣＡＰＥ）,它与厚度无关,是一种方便的求气块平均浮力的方法。正规化有效地区别了ＣＡＰＥ类似而其浮力不同,积分厚度不同的环境。而且由于ＣＡＰＥ的垂直分地对流上升气流的强度可能有很大的  相似文献   

Abiotic/Biological Interactions in Coastal Marine Communities: Insights from an Alaskan Fjord     

Arny L. Blanchard  Howard M. Feder  Max K. Hoberg  Ann L. Knowlton 《Estuaries and Coasts》2017,40(5):1398-1417

Interactions among multi-scale coastal marine ecosystem processes can be expected to play large roles in and interact with biological processes as stresses increase, potentially allowing interfering processes (including biological interactions) to become more prevalent. Retrospective analyses of intertidal (1988–1992) and subtidal (1971–2012) species compositions from a long-term ecological research program in Port Valdez, Alaska evaluated associations between benthic community structure and physical conditions to better understand interactions between regional to local processes on flora and fauna. Low salinity, habitat structure (varying from mudflats to rocky shores over a distance of <18 km), and suspended sediments contributed to intertidal community structure via elimination of predators from low-salinity prey refugia. Subtidal communities demonstrate adjustments by macrofauna to sedimentation with smaller, disturbance-tolerant fauna towards the head of the fjord as well as effects from depth-related covariates. Shared ecological processes result in comparable community trends in subtidal and intertidal habitats among subarctic and arctic fjords and similarly among coastal environments of the North Pacific. Control exerted by interactions among climatic, oceanographic, and local processes interacting with biota contributes to the direction and length of recovery from disturbance events and environmental changes. Feedbacks, mediation of recovery by additional processes, and strengths of interactions also play important roles in determining interaction outcomes. Interactions among local, regional, and global-scale processes may become critical sources of change as global ecosystem transitions through new climate states.  相似文献   

Analysis of Radionuclide Releases from the Fukushima Dai-Ichi Nuclear Power Plant Accident Part I     

G. Le Petit  G. Douysset  G. Ducros  P. Gross  P. Achim  M. Monfort  P. Raymond  Y. Pontillon  C. Jutier  X. Blanchard  T. Taffary  C. Moulin 《Pure and Applied Geophysics》2014,171(3-5):629-644

Part I of this publication deals with the analysis of fission product releases consecutive to the Fukushima Dai-ichi accident. Reactor core damages are assessed relying on radionuclide detections performed by the CTBTO radionuclide network, especially at the particulate station located at Takasaki, 210 km away from the nuclear power plant. On the basis of a comparison between the reactor core inventory at the time of reactor shutdowns and the fission product activities measured in air at Takasaki, especially ⁹⁵Nb and ¹⁰³Ru, it was possible to show that the reactor cores were exposed to high temperature for a prolonged time. This diagnosis was confirmed by the presence of ¹¹³Sn in air at Takasaki. The ¹³³Xe assessed release at the time of reactor shutdown (8 × 10¹⁸ Bq) turned out to be in the order of 80 % of the amount deduced from the reactor core inventories. This strongly suggests a broad meltdown of reactor cores.  相似文献   

Reduction of flatfish habitat as a consequence of the proliferation of an invasive mollusc     

C. Kostecki  S. Rochette  R. Girardin  M. Blanchard  N. Desroy  O. Le Pape 《Estuarine, Coastal and Shelf Science》2011

Coastal bays provide habitats for juveniles and adults of many marine species. Mont Saint-Michel Bay (MSMB, France) hosts a highly diversified fish community and constitutes one of the most important nursery grounds for many commercially exploited marine species, such as sea bass, flatfish, clupeids and rays in the English Channel. Besides, MSMB also suffers from the massive invasion of an exotic mollusc, the American slipper-limpet (Crepidula fornicata, L.). This species arrived four decades ago and now represents the main filter-feeder biomass in the bay (150 Mt), an order of magnitude larger than local farmed and natural shellfishes. Recent analyses underlined the impact of this small gastropod on the trophic structure of this bay and its negative influence on juvenile sole densities in the nursery grounds. The present study uses a geostatistical approach to explore the effect of the extension of the slipper-limpet on flatfish (common sole Solea solea, L.; plaice Pleuronectes platessa, L.; brill Scophthalmus rhombus, L. and flounder Platichthys flesus, L.) spatial distribution. Data collected during survey of the MSMB at the end of the 1970s and three decades later have been used to build interpolated maps of (1) slipper-limpet and (2) flatfish spatial distributions. Slipper-limpets were concentrated in a small area, in the western part of the MSMB, in the 1970s while today they occupy half of the bay. This rapid proliferation led to the decrease of available surface for flatfishes, which previously occupied the whole bay and are now restricted to its eastern part. The present study highlighted that the negative influence on fish habitat in MSMB is apparently more related to changes in the substratum than to trophic interactions. This invasion has possible consequences on flatfish population renewal at a large scale and may also damage other benthic or demersal species, such as rays.  相似文献   

Theoretical study of OH-defects in pure enstatite   总被引：1，自引：0，他引：1  

Etienne Balan  Marc Blanchard  Haohao Yi  Jannick Ingrin 《Physics and Chemistry of Minerals》2013,40(1):41-50

The infrared spectroscopic properties of selected defects in orthoenstatite are investigated by first-principles calculations. The considered defects include doubly protonated Mg vacancies at M1 and M2 sites, fully protonated SiA and SiB vacancies (hydrogarnet defects), and doubly protonated SiA and SiB vacancies associated with interstitial Mg²⁺ cations. The bands observed at 3,070 and 3,360 cm^?1 in the spectrum of synthetic enstatite samples are ascribed to O2A–H and O2B–H groups, respectively, associated with M2 vacancies. The theoretical models suggest that bands observed at 3,590 and 3,690 cm^?1 in the spectrum of enstatite samples synthesized under low silica-activity conditions correspond to O2H and O1H groups associated with SiB vacancies partially compensated by interstitial Mg²⁺ cations in fivefold coordination. The theoretical relation between the integrated absorption coefficient of OH-defects and vibrational frequencies is consistent with previous observations indicating that the absorption coefficients of OH-defects are comparatively stronger in enstatite than in the olivine polymorphs.  相似文献   

Cosmological Parameters: Where are we?     

Alain Blanchard 《Astrophysics and Space Science》2004,290(1-2):135-148

The present-day large increase of the amount of data relevant to cosmology, as well as their increasing accuracy, leads to the idea that the determination of cosmological parameters has been achieved with a rather good precision, may be of the order of 10%. There is a large consensus around the so-called concordance model. Indeed this model does fit an impressive set of independent data, the most impressives been: CMB C_l curve, most current matter density estimations, Hubble constant estimation from HST, apparent acceleration of the Universe, good matching of the power spectrum of matter fluctuations. However, the necessary introduction of a non zero cosmological constant is an extraordinary new mystery for physics, or more exactly the come back of one of the ghost of modern physics since its introduction by Einstein. Here, I would like to emphasize that some results are established beyond reasonable doubt, like the (nearly) flatness of the universe and the existence of a dark non-baryonic component of the Universe. But also that the evidence for a positive cosmological constant may not be as strong as needed for its existence to be considered as established beyond doubt. In this respect, I will argue that an Einstein-De Sitter universe might still be a viable option. Some observations do not fit the concordance picture. I discuss several of the claimed observational evidences supporting the concordance model and will focus more specifically on the observational properties of clusters which offer powerful constraints on various quantities of cosmological interest. They are particularly interesting in constraining the cosmological density parameter, nicely complementing the CMB result, which by its own does not request a non vanishing cosmological constant, contrary to what is sometimes claimed. Early, local, estimations based on the M/L ratio are now superseded by new tests that have been proposed during the last ten years which are globalin nature. Here, I will briefly discuss three of them: 1) the evolution of the abundance of clusters with redshift 2) the baryon fraction measured in local clusters 3) apparent evolution of the baryon fraction with redshift. I will show that these three independent tests lead to high matter density for the Universe in the range 0.6 — 1. I therefore conclude that the dominance of vacuum to the various density contributions to the Universeis presently a fascinating possibility, but it is still premature to consider it as an established scientific fact.  相似文献   

Fern species richness and abundance are indicators of climate change on high-elevation islands: evidence from an elevational gradient on Tahiti (French Polynesia)     

Robin Pouteau  Jean-Yves Meyer  Pauline Blanchard  Joel H. Nitta  Maruiti Terorotua  Ravahere Taputuarai 《Climatic change》2016,137(1-2):143-156

Coastal sector impacts from sea level rise (SLR) are a key component of the projected economic damages of climate change, a major input to decision-making and design of climate policy. Moreover, the ultimate global costs to coastal resources will depend strongly on adaptation, society’s response to cope with the local impacts. This paper presents a new open-source optimization model to assess global coastal impacts from SLR from the perspective of economic efficiency. The Coastal Impact and Adaptation Model (CIAM) determines the optimal strategy for adaptation at the local level, evaluating over 12,000 coastal segments, as described in the DIVA database (Vafeidis et al. 2006), based on their socioeconomic characteristics and the potential impacts of relative sea level rise and uncertain sea level extremes. A deterministic application of CIAM demonstrates the model’s ability to assess local impacts and direct costs, choose the least-cost adaptation, and estimate global net damages for several climate scenarios that account for both global and local components of SLR (Kopp et al. 2014). CIAM finds that there is large potential for coastal adaptation to reduce the expected impacts of SLR compared to the alternative of no adaptation, lowering global net present costs through 2100 by a factor of seven to less than $1.7 trillion, although this does not include initial transition costs to overcome an under-adapted current state. In addition to producing aggregate estimates, CIAM results can also be interpreted at the local level, where retreat (e.g., relocate inland) is often a more cost-effective adaptation strategy than protect (e.g., construct physical defenses).  相似文献   

Potential effects of temperature on the benthic infaunal community on the southeastern Bering Sea shelf: Possible impacts of climate change     

K.O. Coyle  B. Konar  A. Blanchard  R.C. Highsmith  J. Carroll  M. Carroll  S.G. Denisenko  B.I. Sirenko   《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2885

In the late 1950s, Soviet researchers collected benthic infaunal samples from the southeastern Bering Sea shelf. Approximately 17 years later, researchers at University of Alaska Fairbanks also sampled the region to assess infaunal biomass and abundance. Here, the two data sets were examined to document patterns and reveal any consistent differences in infaunal biomass among major feeding groups between the two time periods. No significant differences in the geometric mean biomass of all taxa pooled were indicated between the two study periods (1958–1959=49.1 g m⁻²; 1975–1976=60.8 g m⁻²; P=0.14); however, significant differences were observed for specific functional groups, namely carnivores, omnivores and surface detritivores. Of the 64 families identified from both data sets from all functional groups, 21 showed statistically significant (P0.05) differences in mean biomass. Of the 21 families showing significant differences, 19 (91%) of the families had higher mean biomass in the 1975–1976 data set. The above differences suggest a trend toward higher overall infaunal biomass for specific functional groups during mid 1970s compared with the late 1950s. Temperature measurements and literature data indicate that the mid-1970s was an unusually cold period relative to the period before and after, suggesting a mechanistic link between temperature changes and infaunal biomass. Food-web relationships and ecosystem dynamics in the southeastern Bering Sea indicate that during cold periods, infaunal biomass will be elevated relative to warm periods due to elevated carbon flux to the benthos and exclusion of benthic predators on infaunal invertebrates by the cold bottom water on the shelf. As long-term observations of temperature and sea-ice cover indicate a secular warming trend on the Bering Sea shelf, the potential changes in food-web relationships could markedly alter trophic structure and energy flow to apex consumers, potentially impacting the commercial, tourist and subsistence economies.  相似文献   

The Seasonal Fate of PCBs in Ambient Air and Atmospheric Deposition in Northern France     

M. Blanchard  M. J. Teil  M. Chevreuil 《Journal of Atmospheric Chemistry》2006,53(2):123-144

Polychlorinated biphenyls (PCBs) as Σ21 congeners, were investigated in atmospheric bulk deposition over one year, along a northern transect of France, including 5 sites from the Atlantic coast to the east of Paris. Evidence was obtained for an easterly rise of the PCB concentrations, from 3 to 76 ng L⁻¹. The PCB patterns were depleted in low chlorinated congeners in rural areas whereas at urban sites, the profiles were typical of local sources. The seasonal variations of concentrations were mainly controlled by the temperature. Next, at Paris, PCB distribution between the gaseous and the particulate phases was studied, considering seasonal parameters and different fate processes. Their distribution showed a prevalence of congeners in the gaseous phase (0.15–1.17 ng m⁻³) which occurrence decreased from 93 to 68% with the rise of congener chlorination level. In the particulate phase, they ranged from 0.01 to 0.27 ng m⁻³, only. Rainwater concentrations ranged from 3.1 to 13.1 ng L⁻¹. A total rain water/air washout ratio was determined and showed a negative correlation with those reported in the literature. That might be attributed to the importance of particle scavenging. The annual bulk deposition ranged from 8 to 29 μg m⁻². A decreasing trend of PCB atmospheric levels over the last fifteen years was confirmed in the studied area.  相似文献   

What Do the CBR Fluctuations Tell Us?     

A. Blanchard  J.G. Bartlett  M. Douspis  M. Ledour 《Astrophysics and Space Science》1998,261(1-4):265-274

The detection of the fluctuations in the CMB by COBE has opened a new area of modern cosmology. The angular spectrum of these fluctuations potentially carries a lot of information, allowing for the possibility of determining accurately the cosmological parameters of the universe and giving constraint on scenario of the early universe. The detections of fluctuations on angular scale of the order of one degree are now numerous and allow one to start to put some constraints. The result presented here summarize our work on the question by the end of 1997. We first show that the Doppler peak is reasonably detected. The nature of the fluctuations has been investigated and found in agreement with a Gaussian distribution. Under the assumption of a critical density universe a large baryon fraction and a low Hubble constant are favored. Open models with Ω₀>≤ 0.4 seems not adequate to describe the data. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献