ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • 2010-2014  (3)
Collection
Publisher
Years
Year
  • 1
    facet.materialart.
    Unknown
    Comparison of Objective Supercell Identification Techniques Using an Idealized Cloud Model (2012)
    American Meteorological Society
    Details
    Publication Date: 2012-07-01
    Description: The accuracy, reliability, and skill of several objective supercell identification methods are evaluated using 113 simulations from an idealized cloud model with 1-km horizontal grid spacing. Horizontal cross sections of vorticity and radar reflectivity at both mid- and low levels were analyzed for the presence of a supercell, every 5 min of simulation time, to develop a “truth” database. Supercells were identified using well-known characteristics such as hook echoes, inflow notches, bounded weak-echo regions (BWERs), and the presence of significant vertical vorticity. The three objective supercell identification techniques compared were the Pearson correlation (PC) using an analysis window centered on the midlevel storm updraft; a modified Pearson correlation (MPC), which calculates the PC at every point in the horizontal using a small 3 km × 3 km analysis window; and updraft helicity (UH). Results show that the UH method integrated from 2 to 5 km AGL, and using a threshold value of 180 m2 s−2, was equally as accurate as the MPC technique—averaged from 2 to 5 km AGL and using a minimum updraft threshold of 7 m s−1 with a detection threshold of 0.3—in discriminating between supercells and nonsupercells for 1-km horizontal grid spacing simulations. At courser resolutions, the UH technique performed best, while the MPC technique produced the largest threat scores for higher-resolution simulations. In addition, requiring that the supercell detection thresholds last at least 20 min reduced the number of false alarms.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    The Impact of Airmass Boundaries on the Propagation of Deep Convection: A Modeling-Based Study in a High-CAPE, Low-Shear Environment (2012)
    American Meteorological Society
    Details
    Publication Date: 2012-01-01
    Description: A suite of experiments conducted using a cloud-resolving model is examined to assess the role that preexisting airmass boundaries can play in regulating storm propagation. The 27 May 1997 central Texas tornadic event is used to guide these experiments. The environment of this event was characterized by multiple preexisting airmass boundaries, large CAPE, and weak vertical shear. Only the experiments with preexisting airmass boundaries produce back-building storm propagation (storm motion in opposition to the mean wind). When both the cold front and dryline are present, storm maintenance occurs through the quasi-continuous maintenance of a set of long-lived updrafts and not through discrete updraft redevelopment. Since the cold front is not required for back building, it is clear that back building in this environment does not require quasi-continuous updraft maintenance. The back-building storm simulated with both the cold front and dryline is found to be anchored to the boundary zipper (the intersection of the cold front and dryline). However, multiple preexisting airmass boundaries are not required for back building since experiments with only a dryline also support back building. A conceptual model of back building and boundary zippering is developed that highlights the important role that preexisting boundaries can play in back-building propagation.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    The Dependence of Storm Longevity on the Pattern of Deep Convection Initiation in a Low-Shear Environment (2011)
    American Meteorological Society
    Details
    Publication Date: 2011-10-01
    Description: The sensitivity of storm longevity to the pattern of deep convection initiation (e.g., multiple, quasi-linearly arranged initial deep convective cells versus an isolated deep convective cell) is examined using idealized cloud-resolving simulations conducted with a low-shear initial environment. When multiple deep convective cells are initialized in close proximity to one another using either a line of thermals or a shallow airmass boundary, long-lived storms are produced. However, when isolated deep convection is initiated, the resultant storm steadily decays following initiation. These results illustrate that a quasi-linear mechanism, such as a preexisting airmass boundary, that initiates multiple deep convective cells in close proximity can lead to longer-lived storms than a mechanism that initiates isolated deep convection. The essential difference between the experiments conducted is that an isolated initial storm produces a shallower cold pool than when a quasi-linear initiation is used. It is argued that the deep cold pools promote deep forced ascent, systematic convective cell redevelopment, and thus long-lived storms, even in environments with small values of vertical shear. The difference in cold pool depth between the simulations is attributed to differences in the horizontal flux of cold air to the gust front. With a single initial storm, the few convective cells that subsequently form provide only a limited source of cold air, leading to a cold pool that is shallow and incapable of fostering continued updraft redevelopment.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...