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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Direct Statistical Simulation of a Two-Layer Primi
tive Equation Model - Marston\, B (Brown Universit
y)
DTSTART;TZID=Europe/London:20131204T113000
DTEND;TZID=Europe/London:20131204T121500
UID:TALK49174AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/49174
DESCRIPTION:Co-authors: Wanming Qi (Brown University)\, Steve
Tobias (University of Leeds) \n\nLow-order statist
ics of the large-scale circulation of planetary at
mospheres may be directly accessed by solving the
equations of motion for the equal-time statistics.
We implement such Direct Statistical Simulation o
f a two-layer primitive equation model by systemat
ic expansion in the cumulants. The first cumulant
is the zonally averaged vorticity\, divergence\, a
nd temperature as a function of latitude and level
\, and the second cumulant contains information ab
out nonlocal teleconnections. At second order (CE2
) the expansion retains the eddy mean-flow intera
ction but neglects eddy-eddy interactions and is r
ealizable. Eddy-eddy interactions appear at third
(CE3) order\, but care must be taken to maintain r
ealizability with a non-negative probability distr
ibution function. The cumulant expansion is conser
vative\, order-by order\, in the total angular mom
entum\, total energy\, and mean-squared potential
temperature. An intermediate approximation\, CE2.5
\, is related to the Edd y-Damped Quasi-Normal Mar
kovian (EDQNM) approximation and maintains realiza
bility at the expense of the introduction of a phe
nomenological timescale for eddy damping. First an
d second cumulants accumulated by time-integration
of the two-layer primitive equations are compared
with those obtained at the fixed points found at
CE2\, CE2.5\, and CE3 levels of approximation\, an
d against statistics obtained from reanalysis of t
he mid-level atmosphere of the Earth. CE2 reproduc
es qualitative features of the zonal mean general
circulation such as the mid-latitude jets. CE2.5 a
nd CE3 improve quantitative agreement in both the
zonal means\, and in the teleconnections. \n
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:Mustapha Amrani
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