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  • 1990-1994  (35)
  • 1965-1969
  • 1994  (35)
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  • 1990-1994  (35)
  • 1965-1969
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  • 1
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary This paper presents the results of the Florida State University atmospheric general circulation model that addresses the impact of sea surface temperature anomalies on an El Niño year. Northern Hemisphere winter season simulation. Specifically, our interest is in the simulation of seasonal winter monsoonal rainfall, the planetary scale divergent motions and the westerly wind anomalies of an El Niño year. The El Niño episode of 1982–1983 was interesting due to its higher than average amplitude and its overall evolution. By late 1982 the anomalous circulations associated with the sea surface temperature forcing had begun to take shape even though the anomalies did not attain their peak amplitude until February 1983. The atmosphere-ocean teleconnections set up a strong pattern of geopotential height anomalies during the Northern Hemisphere winter that coincides with El Niño conditions in the tropical Pacific Ocean. Wallace and Gutzler (1981) defined a Pacific North American (PNA) teleconnection pattern index based on data from within this region. The El Niño episode of 1982–1983 has been shown to be strong via the PNA Index and illustrates an importance for climate models to correctly simulate these teleconnections. The importance of the forced anomalies can be seen in the long-range forecasting of conditions over North America as well as the winter monsoon intensity and location. In this study, we utilize a general circulation model with a resolution of triangular truncation at 42 waves to investigate the effects of prescribed sea surface temperature anomalies. We are able to simulate the majority of the large-scale atmospheric response although on regional climatic scales some phase shifts seem apparent.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 53 (1994), S. 95-109 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The atmospheric boundary layer in an ana-cold front and in a kata-cold front is investigated using measurements at a 200 m high tower near Karlsruhe, Germany. In the ana-cold front the wind speed decreased, whereas the passage of the kata-cold front was accompanied by strong gusts. The frontogenesis function of potential temperature was only weak. Turbulence increased at the fronts as expressed by the turbulent kinetic energy. However, the turbulent vertical momentum flux was relatively inefficient at the passage of the fronts. Also it is attempted to calculated flux profiles and friction in the cold air.
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  • 3
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The maximum entropy production (MEP) principle used in Part J has been extended to separate the two-dimensional required energy transports determined from Nimbus 7 satellite net radiation measurements into atmospheric and oceanic components. In terms of the meridional component of the ocean transport vectors, results show northward ocean transports throughout the entire Atlantic ocean from southern hemisphere high latitudes to northern hemisphere polar regions, southward transports throughout the entire Indian Ocean, and poleward transports separated at approximately 10°S in the Pacific Ocean. The ocean transport patterns are consistent with well-known features concerning heat transport within the three ocean basins. However, uncertainty remains in the magnitudes of the transports. Because of the large remaining discrepancies between published estimates based on direct measurements and indirect estimates derived from energy budget methods, assessing the accuracy of the magnitudes is difficult, although there is evidence that the limited model resolution leads to synergistic biases in the North Atlantic and North Pacific. In terms of the crossmeridional energy transport component, results suggest that most of the net energy transfer in the tropics takes place within the ocean. In the southern hemisphere high latitudes, the Pacific and Indian Oceans export heat cross-meridionally to the Atlantic Ocean through the passages below Cape Horn and the Cape of Good Hope, although the magnitudes of these inter-ocean heat exchanges are small. Another important aspect of the southern hemisphere results is that poleward transports are dominated by the atmospheric component with strong zonal asymmetry. By contrast, in the northern hemisphere, atmospheric transports over the ocean are generally weaker than the corresponding southern hemisphere terms, indicating that the northern hemisphere oceans are relatively more effective in transferring heat poleward. Finally, poleward atmospheric transports over the continental areas exceed those over the ocean at equivalent latitudes as a result of the generally greater energy deficits over the land areas.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 53 (1994), S. 121-121 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
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  • 5
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary A study has been made of the development of a collision efficiency calculation model for the interaction of charged drops in an external electric field over an extended range of Reynolds numbers. The method of superposition of flow fields obtained from the numerical solutions of the Navier-Stokes equations in case of liquid drop was used for the calculations. The available Reynolds numbers range is 0 to 45. The model was developed as a program for IBM-PC compatible computers and has been tested with recently published data.
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  • 6
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary As characteristic of a quasi-hydrostatic and isentropic shallowfluid atmosphere, a criterion of conservation along trajectories is derived for an integral solenoid term, or, by incorporating the mass continuity equation, a corresponding differential quantity. In the latter case, the individual invariant consists of the product of a static stability parameter (−δθ/δp) and the vertical component of the solenoidal vector ∇θ x(w∇θ z). By this coupling one is led to the dynamical importance this in variance principle attains through its direct interdependency with ERTEL's potential vorticity theorem. In combination the two invariance principles mediate a fuller description of the potential vorticity conservation than the “classical” principle concerning the invariant ηθδθ/δp.
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  • 7
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary We have examined the performance of a limited-area mesoscale model of our design in cases of winter cyclones over the southern European-central Mediterranean area with particular ticular attention to standard precipitation statistical scores (bias, threat score, false alarms), obtaining results which compare favourably with other state-of-the-art LAM's documented in the literature. The model, which we briefly describe here, uses standard procedures and includes Geleyn's radiation package and Emanuel's moist convective adjustment scheme. We also discuss the model's performance from the viewpoint of individual surface fields, which display a variety of-mesoscale features correctly reproducing, in most cases, those of the observed fields. The latter have been re-analyzed for this purpose using conventional SYNOP data and ECMWF analyses as first guess.
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  • 8
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Orographically trapped disturbances (OTD) in the lower atmosphere propagate along sufficiently large mountain barriers and are trapped vertically by stable stratification and, laterally, by Coriolis effects against the mountains. Observed events have occurred along the coastal mountains of western North and South America, the Southern African coastal escarpment, the Australian Great Dividing Range, the Rockies and the Himalayas. Scale analysis indicates that, during generation, the fundamental parameters are the Rossby number and the ratio of the Rossby to the Froude number where the length scales in these numbers are the mountain half-width and height. Evaluation of these parameters indicates that only the Southern African case possibly remains in the quasi-geostrophic regime. For propagating disturbances, the observed asymmetry in the horizontal length scales implies that only the momentum balance in the across-mountain direction is likely to be geostrophic. In the along-mountain direction, the inertial, advective and frictional terms are also significant in the momentum balance.
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  • 9
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary First, the Group Method of Data Handling (GMDH) algorithm, a self-organizing method for constructing higher order regression, is applied to build a model for long-term forecasting. Then, the Group Method of Phase Space Component (GMPSC) model is set up based on chaos theory and GMDH. Several case studies show that both GMDH and GMPSC provide an efficient and potentially useful tool for non-linear time series modeling.
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  • 10
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary A fine-mesh regional model simulation of upper-level cyclogenesis is carried out to examine the structure and evolution of the accompanying tropopause fold and its relationship to the surface and upper-level cyclones. The initial state for the simulation, conducted using the 80-km, 16-level version of the National Meteorological Center Eta model, uses the Level III-b gridded dataset for 1200 UTC, 18 January 1986, during the First Intensive Observing Period (IOP-1) of the Genesis of Atlantic Lows Experiment (GALE) project. Results are presented from a 48 hour integration of the model. The emphasis is on the examination of the synoptic scale evolution and structure of the upper-level cyclone and tropopause fold, both of which were successfully simulated in the model. The potential vorticity structure associated with a propagating jet-streak displayed distinctive structure, with its tilt reversing as the jet-streak moved around the base of an amplifying upper-level trough. In addition, the model simulates the intrusion of dry, stratospheric air containing high potential vorticity anomalies into the lower troposphere as well as subsidence warming when the folding of the tropopause occurs. the model also predicts upper-level frontogenesis as a result of a thermally indirect secondary circulation in the exit region of the jet-streak. The success of the model simulation is most likely the result of comprehensive physics and the fine grid resolution employed and, more importantly, the excellent distribution of subsynoptic scale initial data during the GALE project.
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