The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean me- ridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.
FAN Ke1,2,3 & WANG Huijun2 1. Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Based on the reanalysis data fromNCEP/NCAR and other observational data, interannualvariability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), when the circumpolar low in the high southern lati-tudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Nio and South Oscillation (ENSO), the intensity of AH will be inten-sified when El Nio occurs. Both correlation analysis andcase study demonstrate that summer rainfall over East Asia is closely related to MH and AH. When MH intensifies from boreal spring to summer (i.e. from austral autumn to winter)there is more rainfall over regions from the Yangtze Rivervalley to Japan, in contrast, less rainfall is found over south-ern China and western Pacific to the east of Taiwan, andmost of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is lim-ited to localized regions, there is more rainfall over southern China with the intensification of AH. The results in this study show that AAO is a strong signal on interannual time-scale, which plays an important role in summer rainfall over East Asia. This discovery is of real importance to revealing the physical mechanism of interannual variability of EastAsian summer monsoon and prediction of summer precipi-tation in China.
Much geological research has illustrated the transition of paleoenvironmental patterns during the Cenozoic from a planetary-wind-dominant type to a monsoon-dominant type, indicating the initiation of the East Asian monsoon and inland-type aridity. However, there is a dispute about the causes and mechanisms of the transition, especially about the impact of the Himalayan/Tibetan Plateau uplift and the Paratethys Sea retreat, Thirty numerical sensitivity experiments under different land-sea distributions and Himalayan/Tibetan Plateau topography conditions are performed here to simulate the evolution of climate belts with emphasis on changes in the rain band, and these are compared with the changes in the paleoenvironmental patterns during the Cenozoic recovered by geological records. The consistency between simulations and the geological evidence indicates that both the Tibetan Plateau uplift and the Paratethys Sea retreat play important roles in the formation of the monsoon-dominant environmental pattern. Furthermore, the simulations show the monsoon-dominant environmental pattern comes into being when the Himalayan/Tibetan Plateau reaches 1000-2000 m high and the Paratethys Sea retreats to the Turan Plate.
In this paper, the temporal variation characteristics of the dust storm in North China are investigated. Based on power spectrum analysis and wavelet analysis, 1956-1970 and 1985-1999 are chosen as the high-frequency and low-frequency dust storm decades respectively. Analysis results clearly show that the spring and wintertime anomalous atmospheric circulation between these two dec-ades are significantly different. Compared with the former decade, there are a strengthened polar vortex, enhanced westerlies near 50°N, and a weak East Asian major though in the winter of the latter decade. The north and center parts of the Siberian high and the Aleutian low become weak. The southerly and easterly wind anomalies appear over the north and east parts of China, which implies the weakening of East Asian winter monsoon. Meanwhile, northern China experiences warmer winters and wetter springs, which are in favor of the weakening of dust storm intensity in North China. There are significant out-of-phase relationships between dust frequency and wintertime westerly intensity, as well as between dust frequency and Arctic Oscillation. It is also found that the frequency of dust weather is strongly re-lated to winter-springtime East Asian monsoon intensity.
KANG Dujuan1,2 & WANG Huijun1 1. NZC/LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100871, China
