【作者】 张宇；

【导师】 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2012， 博士

【摘要】 南亚高压是北半球100hPa上除极地冷低压外最强大、最稳定的大气活动中心,它影响着西起非洲西海岸东至西太平洋的亚非及太平洋热带和副热带地区,特别是对我国夏半年天气与气候起着举足轻重的作用。因此,在全球气候变化异常的大背景下,对南亚高压的深入研究有助于进一步提高对大气环流异常演变规律的认识和区域性极端天气气候事件预测预报水平。为此,本文利用1961-2010年NCEP/NCAR再分析资料、我国160个台站观测资料,利用M-K检验、合成分析、EOF、奇异值分解等统计学方法,首先,研究了近50a南亚高压特征指数(脊线位置、中心位置、面积、强度、东伸脊点指数)的时空分布及其气候特征；然后,比较了南亚高压中心位置在年内不同月份中热力场、动力场的差异,并探究了青藏高原气温、坎顿岛海温、澳大利亚高压、马斯克林高压、索马里急流等对南亚高压的影响；最后探析了南亚高压特征指数与西太平洋副热带高压脊线、脊点位置的关系。主要研究结果如下：1.南亚高压的时空变化特征1961-2010年,南亚高压整体呈现出脊线位置南移、面积增大、强度增加、中心位置东移南压的趋势,且在1980s尤为明显,相对来说南亚高压夏半年特征指数变化趋势不显著。南亚高压脊线候平均位置变动表现为：1-20候主要呈南北向波动,其中18候位置最南(10.5°N)；20候之后其主体不同幅度的北抬,在24候脊线第一次北跳,越过15°N；28候第二次北跳,越过20°N,从30候之后北抬的幅度减小；37候再次北跳,越过30°N,在第42候北跳到最北位置(33.63°N),随后开始逐渐南撤。南亚高压中心位置从1月份至12月份的移动轨迹呈环状。其中,1、2月份位于菲律宾群岛以东洋面且稳定少动,2月份相对偏东；3月份已明显西移至菲律宾群岛以南；4月份西移至中南半岛以南,北抬幅度不明显；5月份西移且明显北跳,到达中南半岛上空；6月份已西移北抬至青藏高原附近；7月份明显西移北抬,到达伊朗高原；8月份到达最北位置,并东移到青藏高原上空；9月份开始南撤,10月份明显南撤东退,退至海上；11—12月份持续南撤东退,回到菲律宾群岛以东洋面。2.不同月份南亚高压热力场和动力场的差异温度脊的倾斜程度随着南亚高压中心的移动而变化。其中,1-3月倾斜程度相对稳定；4-7月北进过程中,出现明显北倾；8-12月南撤过程中,逐渐恢复到垂直。在100hPa涡度、散度、垂直速度场上,南亚高压中心的环状移动轨迹特征也很明显。随着移动,低层对应的正涡度区在1-6月份逐渐抬高,7-9月相对稳定,10-12月份逐渐降低。西移至菲律宾群岛以南的辐散中心在5月断裂为两个,其中,偏北的辐散中心在6月与青藏高原南侧另一辐散中心汇合,强烈的高层辐散与底层配合的强上升运动使得南亚高压加强。3.不同气候因子与南亚高压的关系研究结果表明,1月份高原东南部、2月份中部和东南部、4月份中南部和东部、5月份南部的气温较高时,南亚高压在高原上建立的时间偏早；11月份气温偏高时,来年南亚高压建立的时间偏早,反之,在高原上建立的时间偏迟。坎顿岛海温、马斯克林高压、澳大利亚高压和TNI指数这四个气候因子与南亚高压各特征指数均存在滞后相关关系,前三个气候因子与南亚高压滞后3-5月的面积指数、滞后4个月(马斯克林高压滞后9个月)强度指数存在显著正相关,与滞后1-3月脊线位置、中心纬度存在显著负相关；TNI指数与南亚高压滞后1个月的面积指数、滞后16个月强度指数为显著负相关,与滞后15月脊线位置、中心纬度为显著正相关。6月份索马里急流弱,则同期南亚高压中心经度偏东；7月份索马里急流强,则同期南亚高压东脊点偏东；8月份索马里急流强度强,则同期南亚高压面积偏大。4.夏季南亚高压与西太平洋副热带高压之间的关系近50a夏季,南亚高压与西太平洋副热带高压(西太副高)的脊线位置、面积、强度的年平均变化趋势基本一致；南亚高压与西太副高的东、西脊点和二者脊线位置逐日变化在有些年份同期、滞后相关表现为同位相变化,有些年为反位相变化。南亚高压东脊点与西太副高西脊点平均状态在36-37候时最为接近。进入6月份,南亚高压与西太副高两脊点之间经距较小时,在西太副高东北侧和西太副高西北侧发生强降水过程中释放大量潜热,诱发南亚高压东移。而南亚高压东移会加强西太副高,当南亚高压东移加强的西太副高与稳定的南亚高压配合,会影响我国西南部、长江中上游、华北、东北等地降水。当6月份南亚高压与西太副高两脊点之间经距较远时,且两脊点持续没有出现相近的经度,不利于我国夏季发生降水；到7月份当二者脊线北抬在西太副高控制区会出现伏旱；8月份副高提前东撤,而南亚高压仍稳定在伊朗高原、青藏高原上空,将会造成我国同期降水整体偏少。更多还原

【Abstract】 South Asian High (SAH) is the strongest and the most stable atmospheric active centers on the height of100hPa except the Polar low. It affects part of Asian and African which cover the areas starting from the west coast of African at its west end and the west Pacific at its east end, and also affects the tropical and subtropical areas. Particularly, SAH plays an important role in weather and climate during the summer half year in China. As a result, a further study on SAH can improve our understanding about the evolution of atmospheric circulation anomalies, and the prediction skill of regional extreme weather/climate.By using the NCEP/NCAR reanalysis data and station observation data,this study gives a systematic research on the characteristics of variations in the location of ridge line, center, area, intensity and the index of eastward ridge point of SAH in different time scales during1961-2010, and investigates the thermal and dynamic features of SAH in different months and the relationships with Western Pacific Subtropical High (WPSH), and explores the impacts of the temperature of Tibetan plateau, Sea-surface temperature,Australian high, Mascrene high, and Somali jet on SAH. Results show that:(A) The characteristics of SAH:During1961-2010, In particular, in the1980s, the ridge line of the South Asia High in the winter half year position southerly area increases, the intensity increases, the eastward shift of the center position southward obvious.Relatively speaking the characteristic exponent of the summer half year, the trend was not significant.The Position prediction of SAH’s Ridge:the1-20th pentad is mainly North-South movements, the18th pentad of the most southern (10.5°N); After the20th pentad of different ranges of the North, jump in the North for the first time, on the24th pentad Ridge, across15°N; the28th pentad North jumped for the second time, over20°N, North from the30th pentad after lifting rates decrease; the37th pentad North jumps again, crossed the30°N, North jump to the most northern location on the42th pentad (33.63°N), then began to withdraw South..Doughnut-shaped mobile track about the centre of SAH from January to December, Moving to the Philippines in the Pacific along the West from January to April, continuing along the West and accompanied to the North in the direction of movement,East-West oscillation over the Qinghai-Tibet plateau and Iran plateau from July to August,SAH began to retreat South from August-September, continuing along the South and accompanied to the East in the direction of movement from September toJanuary in the coming year, the end returned to the Pacific. (B) Investigates the thermal and dynamic features of SAH in different months:With the removing of SAH’s center, the direction of dip, difference of level, and mean status of the ridge line of temperature shows that it trend to north distinctly and far from south, even return to vertical. Hidden heat is much clearly action which effecting on moving of South Asia high center in winter year, compared with the action of sensible heat. However, it has a opposite phenomenon in summer year.Vorticify, divergence, vertical velocity fields on100hPa, also can show the SAH’s center moving track of doughnut-shaped With mobile low-level vorticity zone that corresponds to the gradual elevation From January to June, From July to September of relative stability, from October to December drift down.The monthly variations in divergence.vorticity and vertical motion field reflect the movement path of SAH, and that in divergence and ertical motion filed also present the upture of the divergence Field which shifts from offing to the south of Philippine Islands in May. The northern divergence Center after rupture combines with the divergence center over the south of Tibetan plateau in une,which cooperates with the strong low layer ascending motion, resulting in the intensity of SAH.(C) Influence factors on SAH:If the mean temperatureand When high temperatures in the Plateau South-East on January,Central and South-East of February.ln the South and East on April,in the South on May, SAH in the Highlands and to establish a time-early in the year,and in November is much higher over Southeast Qinghai-Tibet plateau. The ridge line of SAH occurred earlier in Qinghai-Tibet plateau.Moreover, it would be come much later while the mean temperature in that time.Canton Island sea temperature, Mascarene high and Australian high and TNI index of the four climatic factors and the South Asia High characteristic index lag correlation between the first three climatic factors and the South Asian high-pressure hysteresis area index of3-5months.delay of four months (Mascarene high lag9) intensity index exists a significant positive correlation, and lag the position of the ridge in January-March, the central latitude exists a significant negative correlation; the TNI index and the South Asia High area index lagged one month, hysteresis strength index of16months was significantly negatively correlated with lag15months ridge line position, the center latitude significantly positively correlated.In June, the weaker Somali jet. South Asian High and central longitude of the more easterly;In July the Somali Jet intensity increases, the South Asia High East ridge point, the more easterly;Somali Jet intensity increases in August, more large high-pressure area in South Asia.(D) The relationship between SAH and WPSH:Summer of nearly50years, the SAH and Western Pacific subtropical high (WPSH) Ridge position, size, and intensity of average annual change of trend line; the East and West ridges of SAH and WPSH daily changes in some locations, the lag associated with phase change from a year earlier, some years for reversed phase change.During1961-2010, the relationship of the west ridge points of WPSH and eastward ridge point of SAH is that they are the nearest with each other during the36-37th pentad. In June, if the distance between the west ridge points of WPSH and eastward ridge point of SAH is small, occurred in the north side of the the west ridge points of WPSH on the north side from East to West in strong precipitation process releases large amounts of latent heat, makes SAH move to the East. Precipitation in which the North,Southwest and Northeast of China.and the upper-middle reaches of Yangtze River has been influenced by the interaction of SAH and WPSH. In June SAH and WPSH when the margin between the two ridges farther, and two ridges continue does not appear similar to longitude, to the detriment of summer precipitation in China; In July, when both North ridge lift, drought occurs in areas controlled by the WPSH; when WPSH in advance East to retreat and SAH still stable in Iran Plateaus and Qinghai-Tibet plateau.will result in low precipitation over the same period in China.更多还原