Dense fog events in the Yangtze Delta and their climatic characteristics |
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作者单位: | Zhou Zijiang~(**) Zhu Yanjun Ju Xiaohui (National Meteorological Information Centre,Beijing 100081,China) |
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基金项目: | 国家自然科学基金;国家科技部基础平台重点项目 |
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摘 要: | Based on daily observation records of fog and atmospheric visibility from 24 meteorological stations in the Yangtze Delta in the period from 1954 to 2005,the identification standard of dense fog events(DFE)has been proposed in this paper,a quite complete time series of DFEs for the delta constructed,and the climate characteristics of these events analyzed sequentially.Preliminary results showed that there were 564 typical DFEs in the delta from 1954 to 2005.The most frequent season for DFEs was from October to next April,when the number of the events accounted for 89.9% of the annual total,while the least frequent season was summer,when the number only accounted for 1.6% of the total due to higher temperature and more convective weather in the season.In the Yangtze Delta, DFEs occurred less and were weaker in the 1960s,but turned to increase from the end of the 1970s to the beginning of the 1980s,with an abrupt change in 1978.Afterwards,DFEs occurred more frequently,intensively,and indeterministically,and in particular,most fre- quently in the 1980s and intensively in the 1990s.However both the frequency and intensity of DFEs decline apparently in the period of 2000—2005 in the delta.
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Dense fog events in the Yangtze Delta and their climatic characteristics |
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Authors: | Zhou Zijiang Zhu Yanjun Ju Xiaohui |
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Institution: | National Meteorological Information Centre, Beijing 100081, China |
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Abstract: | Based on daily observation records of fog and atmospheric visibility from 24 meteorological stations in the Yangtze Delta in the period from 1954 to 2005, the identification standard of dense fog events (DFE) has been proposed in this paper, a quite complete time series of DFEs for the delta constructed, and the climate characteristics of these events analyzed sequentially. Preliminary results showed that there were 564 typical DFEs in the delta from 1954 to 2005. The most frequent season for DFEs was from October to next April, when the number of the events accounted for 89.9 % of the annual total, while the least frequent season was summer, when the number only accounted for 1.6% of the total due to higher temperature and more convective weather in the season. In the Yangtze Delta,DFEs occurred less and were weaker in the 1960s, but turned to increase from the end of the 1970s to the beginning of the 1980s, with an abrupt change in 1978. Afterwards, DFEs occurred more frequently, intensively, and indeterministically, and in particular, most frequently in the 1980s and intensively in the 1990s. However both the frequency and intensity of DFEs decline apparently in the period of 2000-2005 in the delta. |
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Keywords: | the Yangtze Delta dense fog events (DFE) inter-annual variation Mann-Kendall method running-t test |
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