North Pacific Storm Track And Its Relationship With Cold Air Activity In China

Using the NCEP/NCAR reanalyzed gridding data and the daily minimum temperature data of753stations in China, with climatological statistics analysis and variability diagnosis method of31points band-pass digital filter, Empirical Orthogonal Function(EOF), linear correlation analysis and composite analysis, the climatic characteristics and interannual variability of winter North Pacific storm track in nearly50years are studied. On that basis, the relationships of winter North Pacific storm track’s western, eastern region intensity index and different patterns, intensities storm track with the Northern Hemisphere atmospheric circulation, air temperature and cold air activity in China at the same time are analyzed. The results show that:(1) The climate mean states of winter North Pacific storm track behaves as zonal striped with single maximum center, which is located at the midwestern North Pacific. There are two centers both of the anomalous areas of mean square error distribution pattern and the frequency concentrated areas of the maximum points, one is consisted with the location of the climate mean states, and the other is located at the northeast of North Pacific.(2) The first eigenvector of Empirical Orthogonal Function with the actual value and departure value of winter North Pacific storm track reveal their interannual anomaly of strength in the vicinity of long-term mean locations. The second eigenvector of Empirical Orthogonal Function with the departure value of winter North Pacific storm track reveals their interannual northward or southward migration over the climate mean region and interannual anomaly of strength in northeastern region. The western and eastern region intensity interannual variability of winter North Pacific storm track is independence. There are two typical interannual patterns of winter North Pacific storm track, the single-center type and double-center type storm track.(3) The related distribution of winter North Pacific storm track’s WI (El) index with the Northern Hemisphere500hPa geopotential height field and the upper troposphere jet flows is analogous to WP (PNA) teleconnection pattern.In the year single-center type storm track is strong, the polar vortex southern expanding and three average troughs deepen, which is in favor of polar region cold air spills south. The single-center (double-center) type storm track has closer relationship with subtropical (vortex) jet location and its exit (entrance) region stretch or shrink. The related distribution of WI (EI) index with SLP is analogous to NPO (NAO) teleconnection pattern.In the year single-center type storm track is strong(week), the SLP anomalies present as positive (negative) phase of the AO teleconnection pattern, which is (is not) in favor of polar region cold air accumulate. In Eurasian, the correlation of WI index with near-surface air temperatures is positive, El index has no significant correlation, however. In the year single-center type storm track is strong (week), from south to north of eastern Eurasia, the temperature behaves positive (negative) and negative (positive) anomaly, respectively, which is as the cause of storm track strengthen and weaken, possibly. In the year of double-center type storm track, form south to north of the eastern North Pacific, the temperature behaves positive and negative anomaly, respectively, which is as the reason of the formation of the double-center storm track’s northeast center, possibly.(4) Winter North Pacific storm track WI index and the single-center type storm track have closer relationship with temperature and cold air activity in China. The correlation of the single-center type storm track with temperature in China is positive. In the year single-center type storm track is strong (week), most regions has the temperature anomaly between0.5and1.5degrees Celsius which especially significant in eastern inshore areas and Xinjiang province. The correlation of WI index with cold wave frequency (cooling temperature) in China is basically positive, especially significant in Northeast China and Huang-Huai valleys (northwest region). In the double-center type storm track year, the cold wave frequency is positive anomaly in most Chinese region, the cold wave cooling temperature is positive anomaly in north of China and negative anomaly in central and south China. As storm track behaves different patterns and intensities, the cold air frequency (cooling temperature) has-1to1times (-1.5to1.5degrees Celsius) anomaly. The correlation of WI (EI) index with strong cold air frequency and cooling temperature is positive (negative) in most parts of China, but correlation coefficient is not significant. As storm track behaves different patterns and intensities, the positive and negative anomaly fields and difference fields of strong cold air frequency and cooling temperature in China are staggered distributed with the characteristic of regional differences. The characteristic of correlation pattern of WI and El index with week cold air frequency and cooling temperature in China is positive, negative anomaly fields and difference fields distributed alternately, behaved as regional integrity, correlation coefficient is not significant.