Interannual And Interdecadal Anomaly Features Of Siberian High And Their Impact On Winter Temperature Of China

Based on NCEP/NCAR monthly and daily data of sea level pressure, height and wind, the NOAA monthly sea surface temperature (SST) dataset, the sea ice concentration provided by the Met Office Hadley Centre, the monthly observed average temperature and daily minimum and maximum temperature in China, by using the harmonic analysis, correlation analysis, empirical orthogonal functions, the singular value decomposition and other methods, the interdecadal and interannual anomaly features of winter Siberian High(SH) are investigated, as well as the combined influence which the coordinated variation of SH feature variables has on winter temperature of China. It is also discussed the respond of SH to the SST change in North Atlantic and the anomaly of Arctic sea ice. The results are as followings:(1) On the interdecadal time scale, SH became weak and shrank after the late 1960s, with its east edge retreating to the west and its south edge backing up north. Since the 21st century, SH has a trend of expansion, other SH feature variables alternate between positive phase and negative phase. On the interannual timescale, the area of SH gets the maximum interannual variance. The interannual variability of area and intensity as well as east edge of SH has gone up since the beginning of 21st century. On the interdecadal timescale, starting around 1975, the interdecadal variability of the whole SH feature variables all turned smaller than before, along with the decrease of the amplitudes of SH interdecadal components, which indicates the drive energy of winter monsoon has weakened.(2) The mean winter temperature in China became abnormal high after the mid 1980s, along with the increase occurrence of warm day (night) and the decrease occurrence of cold day(night). When SH strengthens and enlarges with its frontiers sweeping eastward and southward on interannual timescale, then the intensity of SH makes the most impact, leading to the low anomaly of winter average temperature in most parts of China, especially in the South, and vice versa. However for the interdecadal scale, the area of SH has the greatest influence on winter temperature., the land to the north of the Yellow River is the main influence area. The effect SH has on winter warm day(night) in China is greater than the effect on winter cold day(night). On interannual timescale, when SH enhances and outreaches with an expansion to the east and south, the occurrence of cold day(night) goes up in the nation-wide range, particularly the south, while the occurrence of warm day(night) reduces in large area of China especially for the north, and the reverse is also true. On the interdecadal scale, SH provides less influence.(3) In terms of the impact SH has on the winter temperature variability in China, when there are great variations in interannual intensity and area of SH, and the interannual variability of its east edge and south edge is at lower level,as a result, the interannual fluctuation of temperature in most parts of China is sharp. On the interdecadal scale,when all the feature variables’interdecadal variability increases, consequently the interdecadal undulation of winter temperature in the north of the east China gets large, while the interdecadal fluctuation of winter temperature in the south is reduced, and vice versa.(4) The anomalous highness(lowness) of North Atlantic average SST and the positive(negative) phase of North Atlantic SST tripole in winter both can make winter SH strengthen (weaken) and expand(shrink), as well as its east edge moves eastward(westward) and its south edge shifts southward(northward). Both of their decadal correlation is better. Further by comparison, the relation between the former and SH intensity is more outstanding, and the intensity of SH is most heavily affected in especial. When the North Atlantic average SST is anomalously high in winter, a wave train is aroused in the downstream Eurasia, making the Ural mountain high-pressure ridge enhanced prominently. As a result, the negative relative vorticity advection over the SH increases, along with the downdraft grows significantly as well. The above situation causes the enhancement of SH intensity, and vice versa.(5) Both of the Atlantic smaller (larger) sea ice area of autumn and winter can result in the SH buildup (fade) and outreach(shrink) along with expansion eastward and southward(retreat westward and northward). Both of their correlation is more outstanding in interdecadal scale. The autumn smaller (larger) sea ice area gives rise to the enhancement (weakening) of Ural blocking high, then further affecting the development of SH, which has the greatest effects on the intensity, area and east edge of SH. However, the winter smaller (larger) sea ice area causes the abnormal change of spatial form of SH by making the intensity of winter polar vortex weak (reinforce) and Baikal Lake blocking high strengthen (weaken), thereinto the south edge of SH is affected most.