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The Structure of Low Frequency Phenomena in the Tropics and Its Interaction with the Extratropics

Advances in Atmospheric Sciences 1992年第1期9卷 1-16页

作者： Peter J.Webster 董敏 Department of Meteorology The Pennsylvania Stale University PA 16802 USA Academy of Meteorological Science State Meteorological Administration Beijing 100081 PRChe structure of planetary scale low freonency phenomena in the tropics is studied and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean when the Southern Oscillation Index is negative almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile the second logitudinal mode almost disappears. On the other hand the meridional wind field possesses maximum amplitude at higher wave numbers. However near the equatorthe amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving mechanisms.Correlation analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this "remote" correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a "corridor" of communication between the low and high latitudes. The regionality of the correlations confirms to some extent recent theoretical development regarding trapped equatorial modes. Finally

The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher *** the tropics, it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean, when the Southern Oscillation Index is negative, almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile, the second logitudinal mode almost disappears. On the other hand, the meridional wind field possesses maximum amplitude at higher wave numbers. However, near the equator,the amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving *** analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact, stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this 'remote' correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a 'corridor' of communication between the low and high latitudes. The regionality of the correlations confirms, to some extent, recent theoretical development regarding trapped equatorial modes. Finally, time lagged correlations from plus and minus six months between variations of U and OLR indicate that the interactio

关键词： In The Structure of Low Frequency Phenomena in the Tropics and Its Interaction with the Extratropics

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Variations of δ^(18)O in Precipitation along Vapor Transport Paths

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Advances in Atmospheric Sciences 2004年第4期21卷 562-572页

作者：章新平刘晶淼田立德何元庆姚檀栋 College of Resources and Environment Sciences Hunan Normal University Changsha 410081 Chinese Academy of Meteorological Sciences Beijing 100081 Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000hree sampling cross sections along the south path starting from the Tropics through the vapor passage in the Yunnan-Guizhou Plateau to the middle-low reaches of the Yangtze River the north path from West China via North China to Japan under the westerlies and the plateau path from South Asia over the Himalayas to the northern Tibetan Plateau are set up based on the IAEA (International Atomic Energy Agency)/WMO global survey network and sampling sites on the Tibetan Plateau. The variations and the relationship with precipitation and temperature of the δ18 O in precipitation along the three cross sections are analyzed and compared. Along the south path the seasonal differences of mean δ18O in precipitation are small at the stations located in the Tropics but increase markedly from Bangkok towards the north with the δ18O in the rainy season smaller than inthe dry season. The δ18O values in precipitation fluctuate on the whole which shows that there are different vapor sources. Along the north path the seasonal differences of the mean δ18O in precipitation for the stations in the west of Zhengzhou are all greater than in the east of Zhengzhou. During the cold half of the year the mean δ18O in precipitation reaches its minimum at Urumqi with the lowest temperature due to the wide cold high pressure over Mongolia then increases gradually with longitude and remains at roughly the same level at the stations eastward from Zhengzhou. During the warm half of the year the δ18O values in precipitation are lower in the east than in the west markedly influenced by the summer monsoon over East Asia. Along the plateau path the mean δ18O val

Three sampling cross sections along the south path starting from the Tropics through the vapor passage in the Yunnan-Guizhou Plateau to the middle-low reaches of the Yangtze River, the north path from West China, via North China, to Japan under the westerlies, and the plateau path from South Asia over the Himalayas to the northern Tibetan Plateau, are set up, based on the IAEA (International Atomic Energy Agency)/WMO global survey network and sampling sites on the Tibetan Plateau. The variations, and the relationship with precipitation and temperature, of the δ18 O in precipitation along the three cross sections are analyzed and compared. Along the south path, the seasonal differences of mean δ18O in precipitation are small at the stations located in the Tropics, but increase markedly from Bangkok towards the north, with the δ18O in the rainy season smaller than in,the dry season. The δ18O values in precipitation fluctuate on the whole, which shows that there are different vapor sources. Along the north path, the seasonal differences of the mean δ18O in precipitation for the stations in the west of Zhengzhou are all greater than in the east of Zhengzhou. During the cold half of the year, the mean δ18O in precipitation reaches its minimum at Urumqi with the lowest temperature due to the wide, cold high pressure over Mongolia, then increases gradually with longitude, and remains at roughly the same level at the stations eastward from Zhengzhou. During the warm half of the year, the δ18O values in precipitation are lower in the east than in the west, markedly influenced by the summer monsoon over East Asia. Along the plateau path, the mean δ18O values in precipitation in the rainy season are correspondingly high in the southern parts of the Indian subcontinent, and then decrease gradually with latitude. A sharp depletion of the stable isotopic compositions in precipitation takes place due to the very strong rainout of the stable isotopic compositions in vapor in the pr

关键词： stable isotope vapor transport path temperature precipitation

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