Recognize seismic anomaly of telluric field by data projection vertical to the polarization

Based on the telluric field data from a Sino-France cooperation station and analysis of the linear characteristic of telluric field polarization, this paper puts forward a new method, called vertical projection to the polarization, to recognize seismic electrical anomaly from observation background. Through careful analysis of polarization variation in different time intervals, it is determined that the best time interval for the regression of polarization is 24 h. Telluric observational data from two earthquakes, one is Yongdeng M_s=5.8 earthquake on July 22, 1995, the other is west Tianzhu M_s=5.4 earthquake on June 1, 1996, are processed by this new method, it is interesting to discover that abnormal electrical signals appeared 28 days and respectively. The limit condition of using this method is discussed finally.

Multi-scale variation characteristics of polar vortex at 10 hPa in the Southern Hemisphere

By use of 1948-2007 NCEP/NCAR reanalysis monthly geopotential data, a set of circulation indices are defined to characterize the polar vortex at 10 hPa in the Southern Hemisphere, including area-（S）, intensity-（P） and centre position-（λc , φc） indices. Sea-sonal variation, interannual anomalies and their possible causes of 10 hPa polar vortex in the Southern Hemisphere are analyzed by using these indices, the relationship between 10 hPa polar vortex strength and the Antarctic Oscillation are analyzed as well. The results show that： （1） the polar region at 10 hPa in the Southern Hemisphere is controlled by anticyclone （cyclone） from Dec. to Jan. （from Mar. to Oct.）, Feb. and Nov. are circulation transition seasons. （2） Intensity index （P） and area index （S） of anticy-clone （cyclone） in Jan. （Jul.） show a significant spike in the late 1970s, the anticyclone （cyclone） enhances （weakens） from ex-tremely weak （strong） oscillation to near the climatic mean before a spike, anticyclone tends to the mean state from very strong oscillation and cyclone oscillates in the weaker state after the spike. （3） There is significant interdecadal change for the anticyclone center in Jan., while markedly interannual variation for cyclone center in July. （4） The ozone anomalies can cause the interannual anomaly of the polar anticyclone at 10 hPa in the Southern Hemisphere in Jan. （positive correlation between them）, but it is not related to the polar cyclone anomalies. （5） There is notable negative correlation between the polar vortex intensity index P and the Antarctic Oscillation index （AAOI）, thus AAOI can be represented by P.