-
Abstract
In this paper, a nonlinear optimization method is used to explore the finite-time instability of the at-
mospheric circulation with a three-level quasigeostrophic model under the framework of the conditional
nonlinear optimal perturbation (CNOP). As a natural generalization of linear singular vector (SV), CNOP
is defined as an initial perturbation that makes the cost function the maximum at a prescribed forecast
time under certain physical constraint conditions. Special attentions are paid to the different structures and
energy evolutions of the optimal perturbations.
The results show that the most instable region of the global atmospheric circulation lies in the midla-
titude Eurasian continent. More specially, SV and CNOP in the total energy norm with an optimization
time of 2 days both present localness: they are mainly located in the midlatitude Asian continent and its
east coast. With extension of the optimization time, SVs are more upstream and less localized in the zonal
direction, and CNOPs differ essentially from SVs with broader zonal and meridional coverages; as a result,
CNOPs acquire larger kinetic and available potential energy amplifications than SVs in the nonlinear model
at the corresponding optimization time. For the climatological wintertime flow, it is seen that the baroclinic
terms remain small over the entire time evolution, and the energy production comes essentially from the
eddy kinetic energy, which is induced by the horizontal shear of the basic flow.
In addition, the effects of SVs and CNOPs on the Eurasian atmospheric circulation are explored. The
results show that the weather systems over the Eurasian continent in the perturbed fields by CNOPs are
stronger than those by SVs at the optimization time. This reveals that the CNOP method is better in
evaluating the instability of the atmospheric circulation while the SV method underestimates the possibility
of extreme weather events.
-
-
Citation
JIANG Zhina, WANG Donghai. 2011: Nonlinearity and Finite-Time Instability in a T21L3 Quasigeostrophic Model. Journal of Meteorological Research, 25(4): 419-429.
JIANG Zhina, WANG Donghai. 2011: Nonlinearity and Finite-Time Instability in a T21L3 Quasigeostrophic Model. Journal of Meteorological Research, 25(4): 419-429.
|
JIANG Zhina, WANG Donghai. 2011: Nonlinearity and Finite-Time Instability in a T21L3 Quasigeostrophic Model. Journal of Meteorological Research, 25(4): 419-429.
JIANG Zhina, WANG Donghai. 2011: Nonlinearity and Finite-Time Instability in a T21L3 Quasigeostrophic Model. Journal of Meteorological Research, 25(4): 419-429.
|
Export: BibTex EndNote
Article Metrics
Article views:
PDF downloads:
Cited by: