Sebastiaan1973 schreef:
schreef:In een ander bericht van hem staat ook een plaatje van de stratosfeer op 70hpa 'nu' en over 10 dagen
Een volledige doorlopen cyclus MJO West Pacific-Rossby waves North Pacific-Stratosfeer (Vortex displacement/split)-Troposfeer (NAM) duurt ongeveer 30 dagen volgens Garfinkel in de definitieve publicatie in Geophysical Research Letters van 27 september j.l.
Eerst verwijst hij naar eerdere publikaties o.a. van Cassou:
'[5] In this study, we expand on these results and demonstrate a statistically significant connection between the MJO
and the stratospheric polar vortex, and subsequently the tropospheric NAM, at lags exceeding a month.'
De integrale eindconclusie luidt:
'Conclusions
[16] A strong connection has been shown to exist between the Madden-Julian Oscillation (MJO) and the Northern
Hemisphere wintertime stratospheric polar vortex. SSWs in the reanalysis record tend to follow certain MJO phases,
likely because the MJO influences the region in the North Pacific most strongly associated with tropospheric planetary
wave driving. Similarly, the strength of the polar vortex is significantly modulated by particular MJO phases at specified
lags, and the magnitude of the influence of the MJO on the polar vortex (4 K) is comparable to that associated with
the Quasi-Biennial Oscillation and El Niño.
[17] The MJO could lead to improved intra-seasonal predictions of the North Atlantic Oscillation (NAO) on
timescales exceeding one month. Previous studies on the MJO/NAO connection [e.g., Cassou, 2008; L’Heureux and
Higgins, 2008; Lin et al., 2009] examined lead times up to 2 weeks, presumably assuming that the MJO-excited poleward
propagating Rossby waves are confined to the troposphere. However, the results of this study allude to another
route, with a longer period, involving poleward and vertical Rossby wave propagation, alteration of the stratospheric
polar vortex, and then downward coupling to the tropospheric NAO. This physical mechanism is similar to that
proposed by Bell et al. [2009] and Ineson and Scaife [2009] with regards to El Niño’s effect on the NAO. However,
future work is necessary to confirm the importance of this mechanism for the connection between the MJO and the
polar vortex/NAM.
[18] Unfortunately, many comprehensive general circulation models (GCMs) do not generate a sufficiently realistic
MJO [Lin et al., 2006], and therefore likely fail to reproduce this connection. While “super-parametrized GCMs†are
capable of simulating the MJO, the computational costs of running such a model are high [Randall et al., 2003]. We
speculate that an accurate simulation of MJO variability in future comprehensive models might lead to improved variability
of the Northern Annular Mode in both the stratosphere and troposphere.'
)
