Large-scale atmospheric systems, such as the Southern Oscillation, North Atlantic Oscillation, and so on, are important climatic change indicators over the northern hemisphere. These systems play essential roles in regional-tocontinental scale climate fluctuation and vegetation activity in response to global change. Using the Pathfinder AVHRR NDVI (Advanced Very High Resolution Radiometer Normalized Difference Vegetation Index) data for the period 1982-2000, the authors investigated the relationship of the inter-annual variations of spring NDVI to nine large-scale climate indices. On average, 57.2% of the satellite-sensed NDVI variance was explained. These climate indices also accounted for a large portion of the trends in NDVI as observed in five regions, namely, north-west North America (climate-related trend was 18.2%/10 years), south-eastern North America (5.8%/10 years), Europe (6.9%/10 years), highlatitude Asia (12.4%/10 years), and East Asia (8.0%/10 years). The results are useful for understanding and predicting the regional-to-continental NDVI variations in response to global climate change.

In this study, the connection between Arctic Oscillation (AO) and variability of East Asian winter mon-soon is investigated. Two indices are chosen to describe the winter monsoon. One is the intensity of the Siberian High, defined as the average SLP over the center region, and the other is the temperature of eastern China, averaged over 76 surface stations. These are two tightly related components, correlate at-0.62 for period 1951-99. Temperature drops by 0.64 degrees Celsius in association witha one standard de-viation increase in Siberian High intensity. It is found that there are significant out-of-phase relationships between the AO and the East Asian winter monsoon. The correlation coefficient between the AO and the Siberian High inten-sity index is-0.48 for period 1958-98. AO is also signifi-cantly correlated with the temperature of eastern China at 0.34. However, when the li'near trend is removed, the corre-lation between AO and temperature is no longer significant. But the strong connection between the AO and Siberian High, and between the Siberian High and temperature are still significant. These results reveal that the AO influences the East Asian winter monsoon through the impact on the Siberian High. Negative phase of the AO is concurrent with a stronger East Asian Trough and an anomalous anticyclonic flow over Urals at the middle troposphere (500hPa). Both the AO and the Eurasian pattern play important roles in changes of the Siberian High and/or East Asian winter mon-soon. They account for 13.0% and 36.0% of the variance in the Siberian High respectively.

对近百年全球陆地平均降水量序列进行χ2检验，证明在El Niño年，全球陆地平均年降水量显著减少，而在La Niña 年则显著增加。近百年来我国东部冬季和秋季降水量与ENSO有显著的关系：El Niño年江南地区降水偏多，北方偏少；La Niña年相反。夏季的关系不如秋、冬季明显，但El Niño年黄河以北有干旱趋势。春季基本没有关系。