Mechanisms of Intraseasonal Amplification of the Cold Siberian High

Abstract

Mechanisms of intraseasonal amplification of the Siberian high are investigated on the basis of composite anomaly evolution for its strongest events at each of the grid points over Siberia. At each location, the amplification of the surface high is associated with formation of a blocking ridge in the upper troposphere. Over central and western Siberia, what may be called "wave-train (Atlantic-origin)" type is common, where a blocking ridge forms as a component of a quasi-stationary Rossby wave train propagating across the Eurasian continent. A cold air outbreak follows once anomalous surface cold air reaches the northeastern slope of the Tibetan Plateau.It is found through the potential vorticity (PV) inversion technique that interaction between the upperlevel stationary Rossby wave train and preexisting surface cold anomalies is essential for the strong amplification of the surface high. Upper-level PV anomalies associated with the wave train reinforce the cold anticyclonic anomalies at the surface by inducing anomalous cold advection that counteracts the tendency of the thermal anomalies themselves to migrate eastward as surface thermal Rossby waves. The surface cold anomalies thus intensified, in turn, act to induce anomalous vorticity advection aloft that reinforces the blocking ridge and cyclonic anomalies downstream of it that constitute the propagating wave train. The baroclinic development of the anomalies through this vertical coupling is manifested as a significant upward flux of wave activity emanating from the surface cold anomalies, which may be interpreted as dissipative destabilization of the incoming external Rossby waves.

Recurrence of Intraseasonal Cold Air Outbreak during the 2009/2010 Winter in Japan and its Ties to the Atmospheric Condition over the Barents-Kara Sea

“…5b, c. This is consistent with the findings of Takaya and Nakamura (2005) where the surface Siberian high is strengthened through the upper level wave train from the Atlantic Sea. The accumulated cold air moves eastward along with the intensifying East Asian trough and reaches Japan (Fig.…”

“…Another line of argument is the role of stationary Rossby waves in the Eurasian continent as an external forcing which in turn intensifies the surface Siberian high and the accompanying cold air outflow (Takaya and Nakamura 2005;Honda et al 2009). One source of stationary Rossby waves is the existence of the Barents-Kara Sea.…”

A comprehensive analysis of coherent rainfall patterns in China and potential drivers. Part II: intraseasonal variability

“…We could not identify a stratospheric origin either. Studies that investigated the origin of cold surges over East Asia report antecedent large-scale wave trains over the Eurasian continent (Takaya and Nakamura 2005;Jeong et al 2006;Park et al 2008Park et al , 2011. Their wave patterns do not resemble the patterns we report here, but appear at higher latitudes.…”

Multi-annual variations in winter westerly disturbance activity affecting the Himalaya

“…The intensified thermal surface high, known as the SH, decreases energy transport into the stratosphere and reduces the meridional temperature gradient, thus decreasing the PE and AO. Negative phases of these two modes weaken the upper-level zonal wind and reduce dynamic instability aloft, thus further enhancing subsidence over Eurasia in a positive feedback during winter months (Gong et al 2001;Wu and Wang 2002a, b;Takaya and Nakamura 2005). The noted feedbacks and associated lags illuminate difficulties in attributing a climate signal in High Mountain Asia to any one mode.…”