Weather observations on Whistler Mountain during five storms   总被引：1，自引：0，他引：1  

Julie M. Thériault  Kristen L. Rasmussen  Teresa Fisico  Ronald E. Stewart  Paul Joe  Ismail Gultepe  Marilys Clément  George A. Isaac 《Pure and Applied Geophysics》2014,171(1-2):129-155

A greater understanding of precipitation formation processes over complex terrain near the west coast of British Colombia will contribute to many relevant applications, such as climate studies, local hydrology, transportation, and winter sport competition. The phase of precipitation is difficult to determine because of the warm and moist weather conditions experienced during the wintertime in coastal mountain ranges. The goal of this study is to investigate the wide range of meteorological conditions that generated precipitation on Whistler Mountain from 4–12 March 2010 during the SNOW-V10 field campaign. During this time period, five different storms were documented in detail and were associated with noticeably different meteorological conditions in the vicinity of Whistler Mountain. New measurement techniques, along with the SNOW-V10 instrumentation, were used to obtain in situ observations during precipitation events along the Whistler mountainside. The results demonstrate a high variability of weather conditions ranging from the synoptic-scale to the macro-scale. These weather events were associated with a variation of precipitation along the mountainside, such as events associated with snow, snow pellets, and rain. Only two events associated with a rain–snow transition along the mountainside were observed, even though above-freezing temperatures along the mountainside were recorded 90 % of the time. On a smaller scale, these events were also associated with a high variability of snowflake types that were observed simultaneously near the top of Whistler Mountain. Overall, these detailed observations demonstrate the importance of understanding small-scale processes to improve observational techniques, short-term weather prediction, and longer-term climate projections over mountainous regions.  相似文献   

Initialisation of Land Surface Variables for Numerical Weather Prediction     

Patricia de Rosnay  Gianpaolo Balsamo  Clément Albergel  Joaquín Muñoz-Sabater  Lars Isaksen 《Surveys in Geophysics》2014,35(3):607-621

Land surface processes and their initialisation are of crucial importance for Numerical Weather Prediction (NWP). Current land data assimilation systems used to initialise NWP models include snow depth analysis, soil moisture analysis, soil temperature and snow temperature analysis. This paper gives a review of different approaches used in NWP to initialise land surface variables. It discusses the observation availability and quality, and it addresses the combined use of conventional observations and satellite data. Based on results from the European Centre for Medium-Range Weather Forecasts (ECMWF), results from different soil moisture and snow depth data assimilation schemes are shown. Both surface fields and low-level atmospheric variables are highly sensitive to the soil moisture and snow initialisation methods. Recent developments of ECMWF in soil moisture and snow data assimilation improved surface and atmospheric forecast performance.  相似文献   

Intraseasonal atmospheric variability and its interannual modulation in Central Africa     

Alain Tchakoutio Sandjon  Armand Nzeukou  Clément Tchawoua 《Meteorology and Atmospheric Physics》2012,117(3-4):167-179

The spatial and temporal structures of the intraseasonal atmospheric variability over central Africa is investigated using 2.5°?×?2.5° daily outgoing longwave radiation (OLR) and National Centers for Environmental Prediction (NCEP) Reanalysis zonal winds for the period 1980–2010. The study begins with an overview of the Central African rainfall regime, noting in particular the contrast amongst Western and Eastern parts, with different topography and surface conditions features. The annual mean rainfall and OLR over the region revealed a zone of intense convective activity centered on the equator near 30°E, which extends southward and covers almost all the Congo forest. The annual cycle of rainfall reflects the classical bi-annual shift of Inter-Tropical Convergence Zone across the equatorial belt, between 10°S and 10°N. The result of the empirical orthogonal functions (EOFs) analysis has shown that the three leading EOF modes explain about 45?% of total intraseasonal variability. The power spectra of all the three corresponding principal components (PCs) peak around 45–50?days, indicating a Madden–Julian Oscillation (MJO) signal. The first mode exhibits high positive loadings over Northern Congo, the second over Southern Ethiopia and the third over Southwestern Tanzania. The PCs time series revealed less interannual modulation of intraseasonal oscillations for the Congo mode, while Ethiopian and Tanzanian modes exhibit strong interannual variations. H?vmoller plots of OLR, 200 and 850?hPa NCEP zonal winds found the eastward propagating features to be the dominant pattern in all the three times series, but this propagation is less pronounced in the OLR than in the 850 and 200?hpa zonal wind anomalies. An index of MJO strength was built by averaging the 30–50?day power for each day. A plot of MJO indices and El Ni?o Southern Oscillation (ENSO) cycle confirm a strong interannual modulation of MJO over Eastern central Africa partially linked with the ENSO events (El Ni?o and La Ni?a). Strong MJO activity is observed during La Ni?a years or during ENSO-neutral years, while weak or absent MJO activity is typically associated with strong El Ni?o episodes.  相似文献   

Radioactivité artificielle de l'air     

Philippot  J. Cl. 《Pure and Applied Geophysics》1961,50(1):216-221

Summary The author summarizes the various results concerning the total -radioactivity of the samples taken either at the level of the earth or at different altitudes. Furthermore, in the first paragraph, the difficulties encountered during these measurements as well as the observations made after the French explosions, are indicated. The results, in the second paragraph are discussed either under the form of radioactivity curves dependant on the altitude, or through employing the notion of the speed of the fall out.  相似文献   

Nouvelles Hébrides     

Cl. Blot  M. Chaigneau  H. Tazieff 《Bulletin of Volcanology》1960,23(1):207-209

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Verbreitung einiger B-Vitamine in Kleingewässern aus der Umgebung von Bern und Untersuchungen über die Abgabe von B-Vitaminen durch Algen     

H. Clémençon 《Aquatic Sciences - Research Across Boundaries》1963,25(2):157-165

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Kolmogorov entropy as a measure of disorder in some non-integrable Hamiltonian systems     

R. Gonczi  Ch. Froeschlé  Cl. Froeschlé 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):117-124

This paper is devoted to study the stochastic behaviour of some Hamiltonian systems with closed velocity curves. We investigate Hamiltonians already studied by Ali and Somorjai (1). These authors, by discussing Poincaré's surfaces of section for several energy values, gave a qualitative evaluation of the stochasticity of the systems.Here we present a quantitative study of this stochastic behaviour. For each energy we compute the Lyapunov characteristic exponents of fifty orbits chosen at random, in order to calculate the Kolmogorov entropy by Pesin's formula. Our results are in agreement with those of Ali and Somorjai: the disorder does not increase monotonically with increasing energy. However, we find that the largest entropy does not necessarily correspond to the maximum of the stochastic volume. The Kolmogorov entropy thus appears to be a good measure of the degree of disorder of dynamical systems.  相似文献   

Thrust sheet motion and earthquake mechanisms     

J.Cl. De Bremaecker 《Earth and Planetary Science Letters》1987,83(1-4)

The mechanism of thrust sheet motion and that of earthquake generation are two aspects of the same phenomenon. Studies of earthquake mechanisms show that only a part of the thrust fault, generally less than 10km in length, is in motion at any given instant; this part sweeps the length of the fault, moving at approximately 3 km/s. Since shear fracture propagation is inherently a dynamic phenomenon, it cannot be understood on the basis of the equations of static equilibrium. The previously proposed mechanisms all rest on such an equilibrium, which necessarily implies that the motion of a thrust sheet occurs simultaneously over its whole length; since the latter may exceed 100 km, the motion becomes a mechanical “enigma”. This enigma vanishes once the dynamic nature of the problem is recognized. The proposed mechanism also suggests that solution features on the fault result from the dissolution of barriers, thus explaining the motion of only part of a thrust sheet.  相似文献   

The lead isotope geochemistry and geochronology of late-kinematic intrusives from the Abitibi greenstone belt,and the implications for late Archaean crustal evolution     

Clément Gariépy  Claude J Allègre 《Geochimica et cosmochimica acta》1985,49(11):2371-2383

Pb isotope abundances are reported for six late-kinematic granitoid intrusives from the Quebec sector of the Abitibi greenstone belt. Leaching experiments on K-feldspar separates reveal the presence of radiogenic Pb, attributed to in situ decay of U and Th. Pb-Pb mineral isochrons were constructed with the K-feldspar data plus results obtained on the total-rock, sphene, apatite and other mineral phases; five localities show no evidence of post-emplacement disturbance and yield ages ranging from 2616 ± 19 to 2718 ± 12 Ma. These ages, which are corroborated by U-Pb dating of small populations of sphene, imply that the orogenic events in the Abitibi belt were terminated 2700–2710 Ma ago, and followed by a period of granitization which lasted for 80 to 100 Ma.The initial Pb isotope composition of the magmas shows that their source regions were isotopically heterogeneous; the time integrated ${}^{238}\text{U}{}^{204}\text{Pb}$ values for the source regions vary from 7.62 to 7.92 and the K-feldspar data indicate that similar heterogeneities were present at the scale of a single intrusion. The range of isotopic composition spans the compositional domain of the mantle, defined by sulfides associated with komatiites and some galenas, and that of the continental crust, defined by sulfides associated with Abitibi iron-formations. Consequently, the granitoid magmas are interpreted as partial melts of a continental crust comprising juvenile, mantle-derived rocks and non-negligible amounts of earlier formed sialic material. The Pb isotope data for the latter are consistent with the presence in the area of 3.0 to 3.4 Ga old sialic crust. The episode of crustal anatexis occurred as a consequence to the orogenic events which resulted in burial of altered supracrustal rocks rich in water and heat-producing elements.  相似文献   

The First International Workshop on Warning Criteria for Active Slides: technical issues,problems and solutions for managing early warning systems   总被引：1，自引：0，他引：1  

Catherine Cloutier  Federico Agliardi  Giovanni Battista Crosta  Paolo Frattini  Corey Froese  Michel Jaboyedoff  Jacques Locat  Clément Michoud  Hideaki Marui 《Landslides》2015,12(1):205-212

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