Recorded presentation9A.4
Impact of Polar night jet on the Ural blocking circulation in boreal winter
Wen Zhou, City Univ. of Hong Kong, Hong Kong, China; and L. Wang, W. Chen, J. Chan, and R. H. Huang
The relationship between the Polar night jet (PNJ), Ural blocking and East Asia winter monsoon is examined. It is found that the internal atmospheric process related to the one-month-lead stratospheric PNJ might affect the Ural blocking circulation in boreal winter, and further lead to a warm or cold winter monsoon over East Asia regions.The close linkage between PNJ and Ural blocking might be due to the downward propagation of stratospheric signals. However, this PNJ-Ural blocking relationship has weakened during recent decades. Before 1976, the Ural Ural blocking is closely related to the statospheric PNJ. If the PNJ signal is removed from the Ural blocking index, the influence of Ural blocking on the East Aisa becomes weak and less significant. After 1976, the climate anomalies in the East Asia are no longer significantly associated with the Ural blocking, suggesting this stratospheric signal in the Ural blocking circulation is weakened. A possible mechanism resposible for such transition between troposhere and stratosphere could be related to the tropospheric propagation of planetary waves. When more planetary wave propagate into the stratosphere, the coupling between troposhere and stratosphere is strong, and vice versa. A weakened coupling process between troposhere and stratosphere since 1976 might prevent the stratospheric signal from propagating downward. Recorded presentation
Session 9A, General Climate Studies: Climate Dynamics
Wednesday, 23 January 2008, 8:30 AM-10:00 AM, 215-216
Previous paper Next paper