@Article{MesingerVelj:2017:RePaRe,
author = "Mesinger, Fedor and Veljovic, Katarina",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {University
of Belgrade}",
title = "Eta vs. sigma: review of past results, Gallus–Klemp test, and
large-scale wind skill in ensemble experiments",
journal = "Meteorology and Atmospheric Physics",
year = "2017",
volume = "129",
number = "9",
pages = "573--593",
month = "Dec.",
abstract = "To determine the effect of switching between the eta and the sigma
coordinate in numerical weather prediction involving topography,
five sets of tests were performed. The eta version did better in
all of them particularly with precipitation scores and more
accurate placement of storms. However, a problem of flow
separation in the lee of the bell-shaped topography discovered by
Gallus and Klemp seemed to many to suggest the eta coordinate to
be ill suited for high-resolution models. Flow separation is shown
not to occur following a refinement of the eta discretization.
Trying to identify a primary cause of the improvement in 250 hPa
winds previously demonstrated in Eta ensemble members over their
ECMWF driver members, ten of the Eta members were run switched to
sigma. At a critical time, the Eta members in eta mode showed a
tendency for more accurate tilt of a 250 hPa trough than the
members run in sigma mode. The experiment was rerun for a more
recent and higher resolution ECMWF ensemble, and for an increased
number of members. The advantage of the Eta over ECMWF is seen
again, even though this time, the Eta resolution during the first
10 days of the experiment was about the same as that of driver
members. Rerunning the Eta ensemble switched to sigma showed an
advantage in the Eta/eta 250 hPa wind scores used, again
associated with an upper-air trough's movement across the Rockies.
Better positioning of lee lows ahead of these troughs using
Eta/eta is suggested to be making significant contributions to its
better precipitation scores. Implications of experiments done for
regional climate modeling are discussed as well.",
doi = "10.1007/s00703-016-0496-3",
url = "http://dx.doi.org/10.1007/s00703-016-0496-3",
issn = "0177-7971",
language = "en",
targetfile = "fedor_eta.pdf",
urlaccessdate = "27 abr. 2024"
}