Temporal And Spatial Variation Characteristics Of The Negative Accumulated Temperature In Association With Circulation Changes Over North China In Recent50Years

The observed daily temperature data from62stations in North China and NCEP/NCAR monthly and daily reanalysis data from1961to2009are used to analyze temporal and spatial variation characteristics of negative accumulated temperature (NAT) and atmospheric circulation features related to NAT. Results show that:(1) During recent50years the NAT changes consistently in the whole area and rises year by year, rising significantly from the midterm of80’s in the20th century. The NAT displays5a variation period and the interdecadal oscillation of22-24a, but the mean value has regional difference. Characteristics of regional variation of NAT are:absolute value of NAT with linear variation significantly in the west of North China is larger than the NAT in the east of North China. There are both abrupt changes in the west and east of North China occurring at1988and1986respectively. A3-6year period is found in the west of North China while the east of North China is dominated by a2-4year period, which maybe are related to terrain.(2)Circulation features associated with NAT interdecadal variations show the NAO pattern: in cold and warm period, sea level pressure anomalies over high latitudes and the North Atlantic show see-saw distribution. Circulation related to NAT inter-annual changes is characterized by opposite distribution SLP difference in East Asia and the Pacific region:in cold and warm period.(3) North Atlantic Oscillation and NAT have positive correlation. NAO effect NAT through the influence of East Asian and the Siberian High(SH) intensity. SH and NAT is negatively correlated. When the index of SH is highx, the SH is enhanced and trough in East Asia is stronger, thereby causing the winter monsoon strengthened, obvious temperature drop in North China.(4) In1967Siberian High and the East Asia trough is stronger, causing the cold air stronger over Asia, In2006circulation situation is contrast. NAT of1967is controlled by the Siberian High. NAT of2006is controlled by the Siberian High and the North Atlantic Oscillation.(5) From December27th to December31th in1967, strong transient waves in the North Atlantic spread from the high latitudes to East Asia, corresponding to the North China low-temperature. From January6th to January10th in2007strong transient wave in the North Atlantic spread weakly to the downstream, in the Same period with North China high temperatures. It is found find that there is a good correspondence between the intensity of transient wave propagation and spread to reach the location and low temperature.