【作者】 曾刚；

【导师】 孙照渤； 王维强；

【作者基本信息】 南京信息工程大学 ， 气象学， 2008， 博士

【摘要】 本文采用1950～2000年观测的不同海域(全球、热带外、热带、热带印度洋—太平洋、热带印度洋及热带太平洋)海表温度分别驱动NCAR Cam3全球大气环流模式,进行了多组长时间积分试验,对比ERA-40再分析资料,讨论了这些海域海表温度异常(SSTA)对东亚夏季风及其环流系统主要成员年代际变化的影响。主要结论如下:(1)气候海表温度驱动全球大气环流模式模拟的大气内部变化中,东亚夏季风及其环流系统主要成员的自然变率主要表现为年际变率;东亚夏季风及南亚高压具有较明显的年代际变化特征,而西北太平洋副热带高压和东半球越赤道气流的年代际变化特征不明显;东亚夏季风与大气内部的EU型遥相关波列关系较密切。(2)全球、热带、热带印度洋—太平洋和热带太平洋海表温度变化对东亚夏季风的年代际变化均具有重要作用,热带太平洋是关键海区。利用观测的全球、热带、热带印度洋—太平洋及热带太平洋海表温度分别驱动全球大气环流模式均能模拟出东亚夏季风在20世纪70年代中后期发生的年代际减弱现象,与观测结果较一致;利用热带外海表温度驱动全球大气环流模式的数值试验结果表明,热带外海表温度异常对东亚夏季风年代际变化的影响小;利用观测的热带印度洋海表温度驱动全球大气环流模式的数值试验结果表明,当热带印度洋海表温度年代际偏暖(冷)时,东亚夏季风年代际增强(减弱),与热带太平洋海表温度变化对东亚夏季风年代际变化的影响相反。(3)数值试验结果表明,全球、热带、热带印度洋—太平洋和热带印度洋海表温度变化均对夏季西北太平洋副热带高压的年代际变化有重要作用,即在这些海域的海表温度变化影响下,西北太平洋副热带高压均在20世纪70年代中后期发生年代际变化,其后副高面积增大、强度增强、位置偏西、偏南,这与观测结果较一致;热带太平洋海表温度变化对夏季西北太平洋副热带高压的年代际变化也有重要作用,在其作用下,夏季西北太平洋副热带高压的强度、面积在20世纪60年代后期发生年代际变化,西伸脊点在60年代初发生年代际变化,南界在70年代中后期发生年代际变化,这些时段以后副高强度增强、面积增大、偏西、偏南;热带外海表温度变化对西北太平洋副热带高压年代际变化作用较小。(4)数值试验结果表明,热带太平洋海表温度变化对南亚高压的年代际变化有重要影响。热带太平洋海表温度的EOF第三模态,即“三明治”海温分布型(赤道东太平洋海表温度与其西北、西南海表温度呈反位相变化)具有明显的年代际变化特征,与南亚高压年代际变化的关系密切。(5)全球、热带、热带印度洋—太平洋及热带太平洋海表温度变化均对越赤道气流在20世纪70年代中后期的年代际变化具有重要作用,热带太平洋是关键海区。利用观测的全球、热带、热带太平洋—印度洋和热带太平洋海表温度分别驱动全球大气环流模式均能模拟出索马里、120°E和150°E越赤道气流在20世纪70年代中后期由弱变强的年代际变化特征,其中模拟的索马里越赤道气流年代际变化特征与观测结果较一致,而热带外及热带印度洋海表温度分别驱动全球大气环流模式均未能模拟出此年代际变化现象。(6)热带太平洋海表温度的年代际背景变化对东亚夏季风、西北太平洋副热带高压、南亚高压及东半球越赤道气流的年代际变化具有重要作用;热带印度洋海表温度的年代际背景变化也对西北太平洋副热带高压年代际变化具有重要作用。这些作用主要表现在:当热带太平洋海表温度处于暖背景年代(1981～1998年)时,东亚夏季风减弱,西北太平洋副热带高压面积增大、位置偏南、偏西南亚高压强度增强、面积增大、位置东伸、西扩、南压,夏季索马里、120°E、150°E越赤道气流强度均增强;当热带太平洋海表温度处于冷背景年代(1958～1975年)时,东亚夏季风及其环流系统主要成员的年代际变化情形基本与之相反。西北太平洋副高在热带印度洋暖背景年代比热带印度洋冷背景年代面积大、位置偏西。更多还原

【Abstract】 Used are the 1950-2000 observational SSTs from global, extratropical, tropical oceans, Indian Ocean-Pacific at tropics, tropical Indian Ocean and tropical Pacific, with each of them to conduct experiments by means of the NCAR Cam3 as the global atmospheric model, with the results compared to ERA-40 reanalysis in order to address the SSTA impact on inter-decadal change of East Asian summer monsoon (EASM) and the principal members of its circulation systems. The following are of note.1) The Cam3-simulated natural variability is dominantly the interannual variation in the main members of the summer monsoon and its circulations, with the monsoon and the south Asian high (western Pacific subtropical high and eastern hemispheric cross-equatorial flow) marked by more distinct (unremarkable) interdecadal variation and a close relation exists of the monsoon to atmospheric EU teleconnection wavetrain.2) The simulated EASM by means of observational SSTs of global/tropical oceans, Indian Ocean-Pacific at tropics and tropical Pacific shows an interdecadal weakening process to be in the mid-late 1970s, in better agreement with observations, thereby demonstrating that SSTA in these ocean regions play an active role in the interdecadal variability of the summer monsoon. The tropical Pacific is the key basin. The numerical experiment with extratropical SSTs indicates that the SSTA there has lower impact upon the interdecadal change of the monsoon. The modelings using tropical Indian Ocean SSTs demonstrates that the monsoon interdecadal variability is strengthened (weakened) when these SSTA are warmer (colder) than mean on an interdecadal basis with its variability opposite to that related to the tropical Pacific SSTs.3) Modelings show that variations in SSTs of global/tropical oceans, Indian Ocean -Pacific at tropics and tropical Indian Ocean exert pronounced impacts upon the interdecadal variability of western Pacific subtropical highs in summer, i.e., an interdecadal change happening to the highs’in the mid-late 1970s, after which the high’s area is enlarged, its vigor is intensified and position is west- and/or southward of mean, all in better harmony with in situ observations. Also, change in tropic Pacific SST is innegligible to the interdecadal variation of the western Pacific subtropical high in summer, whose strength and area experience interdecadal variability in the late 1960s, with its westward extending point (southern boundary) undergoing an interdecadal variation early in the 1960s (mid-late 1970s), after which its intensity is amplified, its area is enlarged and position west- and/or southward compared to mean. In comparison, change in extratropical SSTs has little effect on the interdecadal variability of the subtropical high.4) Simulations show that change in tropical Pacific SSTs plays an important role the interdecadal variation of the south Asian high. The related EOF3 mode is the "sandwich" looking SST pattern, implying the change in equatorial eastern Pacific SST contrary to those in SSTs to the north and south of the eastern equatorial Pacific, which is marked by distinct interdecadal variation, in close association with that of the south Asian high.5) In the context of SSTs from global/tropical oceans, tropical Indian Ocean-Pacific and tropical Pacific the Cam3-reproduces the interdecadal variation of the cross-equatorial flows over Somali, 120°E and 150°E that change toward a strong phase in the middle - late 1970s, with the emulated Somalian airflow closer to observations, failing to simulate the interdecadal variation by using SSTs of extratropical and tropical Indian Ocean, thereby illustrating the prominent impacts on the interdecadal variability of the cross-equatorial air exerted by the change in SSTs over global/tropical oceans, tropical Pacific - Indian Ocean and the tropical Pacific, the tropical Pacific acting as the key region.6) As a background, the interdecadal variation of tropical Pacific SST has important effects upon the equivalent scale change in east Asian summer monsoon, western Pacific subtropical high, south Asian high and cross-equatorial air of the eastern hemisphere The tropical Indian SST as the interdecadal background has prominent influence upon the interdecadal variation of the western Pacific subtropical high in the following aspects. When tropical Pacific SSTs are in a warm background (1981-1998), East Asian summer monsoon reduces in vigor, the subtropical high increases in area, and is positioned south- and/or westward, the south Asian high is intensified, expanding its size with its position extending eastward, expanding westward and moved southward, in conjunction with reinforcement of summer cross-equatorial air at Somali, 120°E and 150°E, and v.v. to great extent when tropical Pacific SST is in a cold background (1958-1975). On the other hand, the western Pacific subtropical high is larger in size and positioned westward of mean when tropical Indian SST is in a warm background compared to tropical Indian SST in a cold background.更多还原