| 摘要: |
| 用1951～1998年的资料研究了北半球500 hPa四季高度场的长期趋势变化。结果表明, 48年来低纬度 500 hPa高度场多为正趋势而高纬度则多为负趋势。近 48年低纬的西北非洲、地中海及以西的北非北部,低纬度的中太平洋、贝加尔湖及以东地区,西北北美的高度呈持续正趋势；而阿留申及北太平洋、格林兰以南及东北北美、阿拉伯海以北高度明显降低。突变分析表明,大约60年代初及1976年,500 hPa发生明显的环流突变。这两次变化在两大洋上的 500 hPa有明显不同,第 1次表现为低纬中大西洋高度降低,西北非洲高度增加。第2次则表现为低纬中太平洋、贝加尔湖地区高度增加,北太平洋高度降低。统计检验表明第2次突变,低纬的正突变比北太平洋负突变更明显,是一次北半球的大尺度跃变事件。 |
| 关键词: 北半球500 hPa高度场 趋势变化 年代际变化 突变 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金(No:49875019)资助 |
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| THE SECULAR TREND VARIATIONS AND ABRUPT CHANGE OF NORTHERN 500 hPa GEOPOTENTIAL HEIGHT |
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CHEN Hui,SHI Neng,WANG Yong-bo
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Nanjing Institute of Meteorology, Nanjing 210044, China
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| Abstract: |
| The trends and abrupt variations of Northern hemisphere (NH) 500 hPa seasonal geopotential height are examined using the data for the period 1951-1998. Evidence suggests that low (high) latitude 500 hPa geopotential height displays a remarkably positive (negative) trend; the positive anomaly of the height is maintained over NW Africa, the western Mediterranean Sea and northern North Africa, mid-Pacific at lower latitudes, Lake Balkal and area to the east and NW North America; the height drops significantly over the Aleutians and North pacific, the area to the south of the Greenland and NE North America and the sector to the north of the Arabian sea. Further, analysis of abrupt change shows that the 500 hPa circulations experience noticeable sudden change twice, once around the early 1960s and again in 1976, during which, however, the height exhibits great difference between the Pacific and Atlantic. In the first case it drops (rises) over the mid Atlantic at lower latitudes (NW Africa) in contrast to the height rise (drop) over the mid-Pacific at lower latitudes and Lake Balkal (the North Pacific) in the second abruptness. Statistical test indicates that in the 1976 case the low-latitude positive abrupt change is even more noticeable compared to the negative of the North pacific, thus representing a large-scale jumping event of the northern 500 hPa height. |
| Key words: northern 500 hPa height trend interdecadal variation abrupt change |
