ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1745-1758 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The coalescence of two identical vortices with uniform vorticity is investigated using the numerical method of "contour surgery,'' for two-dimensional inviscid, incompressible vortex dynamics (2VD), and quasigeostrophic shallow-water dynamics (QGSW), to quantify the differences and similarities between the two models. High-resolution calculations show that the evolution of the vortices may fall into three different regimes depending on the initial intercentroid separation. The efficiency of the merger of two vortices into a single elliptical-like vortex is determined by calculating the loss of globally conserved quantities to filaments and small-scale structures. In the 2VD model, it is found that the resultant central vortex always has at least 56% more circulation than either of the initial vortices, showing that the merger process indeed forms larger scales. From energetics, the initial separation for an inviscid transition from two elliptical vortices to a single elliptical vortex is determined, and is shown to be close to the critical merger separation obtained from full numerical calculations. Confirming the results of Polvani et al. [J. Fluid Mech. 205, 215 (1989)], the calculations in the QGSW model show that as the radius of deformation LR decreases, the critical merger separations decrease, the resultant vortex is nonelliptical, fewer filaments are shed, and those filaments shed show an increased propensity to roll up into small vortices (consistent with previous analysis of the stability of strips of potential vorticity with imposed shear). Furthermore, the efficiency of the merger process increases as LR decreases (to perfect efficiency in the limit of small LR).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 365 (1993), S. 535-537 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Measurements from the recently launched Upper Atmosphere Research Satellite (UARS) are providing valuable insights into the distribution of trace constituents and fluid motions throughout the middle atmosphere. Randel et aLl have recently analysed global measurements of the long-lived stratospheric ...
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2020-09-01
    Print ISSN: 0019-1035
    Electronic ISSN: 1090-2643
    Topics: Physics
    Published by Elsevier
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2018-02-22
    Description: The distribution of most trace species within the troposphere depends on a complex interplay between chemistry and transport. Holzer and Waugh (2015) introduced the concept of a path-dependent lifetime τc(r), that parameterizes the integrated chemical loss during transport from the source to a given location r. Here we examine whether this parameterization provides a new approach for decoupling transport and chemistry. We present calculations of path-dependent lifetimes for a suite of chlorofluorocarbon replacement gases in a simple 12-box model and show that for trace species with global lifetimes from 0.5 years to 50 years τc provides an accurate representation of the integrated chemical loss during transport. The value of τc is shown to be sensitive to tropical hydroxyl radical (OH) concentrations, with much weaker sensitivity to extratropical OH or transport. Furthermore, fractional changes in Southern Hemisphere extratropical τc are similar to the corresponding fractional changes in tropical OH; that is, a 10% increase in tropical OH results in a 10% decrease in τc. This suggests that observation-based estimates of τc may be used to constrain tropical OH concentrations provided that τc can be determined with sufficient precision. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2018-01-19
    Description: Climate models predict that the Hadley circulation will expand poleward in a warmer climate, a trend which may cause significant changes in global precipitation patterns. However, recent studies have disagreed as to how strongly changes in the Hadley circulation and changes in the hydrological cycle (specifically the latitude at which precipitation balances evaporation) are related. Here we analyze dynamical and hydrological measures of the Southern Hemisphere edge of the tropics using simulations from the fifth Coupled Model Intercomparison Project (CMIP5) and four reanalysis data sets. In simulations with an abrupt quadrupling of atmospheric CO2 concentrations, all models show a poleward expansion in both metrics. However, there is a large spread among models; the ratio of the hydrological to dynamical expansions varies from 0.6 to 1.4. We show that this model spread can be largely explained by differences in internal variability, which in turn is related to the mean state of models. Differences in mean states among reanalyses are similar to those of models, and so reanalyses do not help constrain uncertainty in model trends. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2016-12-21
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2017-01-01
    Description: How much does minimum daily air temperature vary within neighborhoods exhibiting high land surface temperature (LST), and does this variability affect agreement with the nearest weather station? To answer these questions, a low-cost sensor network of 135 “iButton” thermometers was deployed for summer 2015 in Baltimore, Maryland (a midsized American city with a temperate climate), focusing on an underserved area that exhibits high LST from satellite imagery. The sensors were evaluated against commercial and NOAA/NWS stations and showed good agreement for daily minimum temperatures. Variability within the study site was small: mean minimum daily temperatures have a spatial standard deviation of 0.9°C, much smaller than the same measure for satellite-derived LST. The sensor-measured temperatures agree well with the NWS weather station in downtown Baltimore, with a mean difference for all measurements in time and space of 0.00°C; this agreement with the station is not found to be correlated with any meteorological variables with the exception of radiation. Surface properties are found to be important in determining spatial variability: vegetated or green spaces are observed to be 0.5°C cooler than areas dominated by impervious surfaces, and the presence of green space is found to be a more significant predictor of temperature than surface properties such as elevation. Other surface properties—albedo, tree-canopy cover, and distance to the nearest park—are not found to correlate significantly with air temperatures.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geography , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2017-01-01
    Description: The term polar vortex has become part of the everyday vocabulary, but there is some confusion in the media, general public, and science community regarding what polar vortices are and how they are related to various weather events. Here, we clarify what is meant by polar vortices in the atmospheric science literature. It is important to recognize the existence of two separate planetary-scale circumpolar vortices: one in the stratosphere and the other in the troposphere. These vortices have different structures, seasonality, dynamics, and impacts on extreme weather. The tropospheric vortex is much larger than its stratospheric counterpart and exists year-round, whereas the stratospheric polar vortex forms in fall but disappears in the spring of each year. Both vortices can, in some circumstances, play a role in extreme weather events at the surface, such as cold-air outbreaks, but these events are not the consequence of either the existence or gross properties of these two vortices. Rather, cold-air outbreaks are most directly related to transient, localized displacements of the edge of the tropospheric polar vortex that may, in some circumstances, be related to the stratospheric polar vortex, but there is no known one-to-one connection between these phenomena.
    Print ISSN: 0003-0007
    Electronic ISSN: 1520-0477
    Topics: Geography , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2016-09-07
    Description: The distribution of transit times from the Northern Hemisphere (NH) midlatitude surface is a fundamental property of tropospheric transport. Here, the authors present an analysis of the transit-time distribution (TTD) since air last contacted the NH midlatitude surface, as simulated by the NASA Global Modeling Initiative Chemistry Transport Model. Throughout the troposphere, the TTD is characterized by young modes and long tails. This results in mean transit times or “mean ages” Γ that are significantly larger than their corresponding modal transit times or “modal ages” τmode, especially in the NH, where Γ ≈ 0.5 yr, while τmode 〈 20 days. In addition, the shape of the TTD changes throughout the troposphere as the ratio of the spectral width Δ—the second temporal moment of the TTD—to the mean age decreases sharply in the NH from ~2.5 at NH high latitudes to ~0.7 in the Southern Hemisphere (SH). Decreases in Δ/Γ in the SH reflect a narrowing of the TTD relative to its mean and physically correspond to changes in the contributions of fast transport paths relative to slow eddy-diffusive recirculations. It is shown that fast transport paths control the patterns and seasonal cycles of idealized 5- and 50-day loss tracers in the Arctic and the tropics, respectively. The relationship between different TTD time scales and the idealized loss tracers, therefore, is conditional on the shape of the TTD.
    Print ISSN: 0022-4928
    Electronic ISSN: 1520-0469
    Topics: Geography , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2016-09-28
    Description: Recent studies have suggested that the response of the Southern Ocean to stratospheric ozone depletion is nonmonotonic in time; consisting of an initial cooling followed by a long-term warming. This result may be significant for the attribution of observed Southern Ocean temperature and sea ice trends, but the time scale and magnitude of the response is poorly constrained, with a wide spread among climate models. Furthermore, a long-lived initial cooling period has only been observed in a model with idealized geometry and lacking an explicit representation of ozone. Here the authors calculate the transient response of the Southern Ocean to a step-change in ozone in a comprehensive coupled climate model, GFDL-ESM2Mc. The Southern Ocean responds to ozone depletion with an initial cooling, lasting 25 yr, followed by a warming. The authors extend previous studies to investigate the dependence of the response on the ozone forcing as well as the regional pattern of this response. The response of the Southern Ocean relative to natural variability is shown to be largely independent of the initial state. However, the magnitude of this response is much less than that of natural variability found in the model, which limits its influence and detectability.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...