全新世南亚高压南北移动及其与亚洲夏季风降水的关系

南亚高压是亚洲夏季风系统的重要组成部分，它的强度及位置变化对亚洲夏季风降水有非常重要的影响，对其变化特征和物理机制的研究可以加深对亚洲夏季风演化的认识。论文利用一个海-气耦合模式（KCM），在轨道参数的强迫下模拟了全新世以来（9.5~0 ka B.P.）的气候变化，分析了全新世南亚高压的南北移动特征，并探讨其与亚洲夏季风降水的关系。研究发现，全新世以来南亚高压持续向南移动，同时也反映了对流层上层西风逐渐向南扩张，响应逐渐减少的夏季太阳辐射。早全新世南亚高压偏北主要是由于夏季太阳辐射增加导致伊朗高原感热加热加强。南亚高压的南北移动与亚洲夏季风降水有显著的关系，它与东亚季风区北部和印度季风区降水呈正相关关系，而与东亚季风区南部和西南季风区降水呈负相关关系。偏北的南亚高压在东亚北部上空产生异常反气旋，有利于对流层低层空气辐合上升，降水增加，此外异常反气旋还可以加强西太副高，使得输送到东亚北部的水汽增加。南亚高压偏北时还会在中低纬地区产生异常东风带，减弱了来自孟加拉湾的水汽输入，从而使得东亚南部和西南季风区降水减少。偏北的南亚高压还在阿拉伯海上空产生异常气旋，有利于印度夏季风降水的增加。南亚高压的南北振荡可以部分解释相同轨道强迫下亚洲夏季风降水出现显著空间差异的原因。

Meridional migration of the South Asian High and its association with Asian summer monsoon precipitation during the Holocene

The South Asian High is the most intense and persistent anticyclone in the upper troposphere in boreal summer, which is an important member of the Asian summer monsoon system. The South Asian High, in particular its position, plays an important role in the regional climate anomaly over Asia. The behaviors of the South Asian High have been extensively studied on the interannual-decadal time scales in present-day climate. However, its variability is rarely discussed on longer time scales during the Holocene. With the Kiel Climate model(KCM), this study simulated the Holocene climate to analysis the meridional movement of the South Asian High and its effect on Asian summer monsoon precipitation during the Holocene. The KCM is a coupled atmosphere-ocean-sea ice general circulation model. The model comprises the spectral atmospheric model ECHAM5 and the Nucleus for European Modeling of the Ocean(NEMO) ocean-sea ice general circulation model, coupled through OASIS3. The horizontal resolution of the atmospheric model ECHAM5 is T31(3.75°×3.75°), and in the vertical direction there are 19 levels up to 10 hPa. The horizontal resolution of the ocean model NEMO is on average 1.3° based on 2° Mercator meshes with grid refinement in the tropical regions, where the meridional grid-point separation reaches 0.5°. The Holocene climate simulation is forced by the Earth's orbital parameters for the period from 9.5 ka B.P. to 0 ka B.P. with a tenfold acceleration. Other factors, including ice-sheets and greenhouse gases concentrations, are kept the same as the pre-industrial levels. The South Asian High has experienced a persistent southward migration during the Holocene, following summer insolation. Accompanied by the southward migration of the South Asian High, the upper-level westerlies expanded southward during the Holocene. The southward migration of the South Asian High was mainly caused by the cooling of the Iranian Plateau resulting from the reducing summer insolation. The cooling of the Iranian plateau weakened the sensible heating, which further weakened the low-level convergence and the resultant upper-level divergence over the northern part of the South Asian High, ultimately leading to a southward migration of the South Asian High. The meridional migration of the South Asian High was closely related to Asian summer monsoon precipitation anomalies. A northward displacement of the South Asian High was associated with enhanced precipitation in northern East Asia and South Asia, and reduced precipitation in Central China, southern East Asia and Indochina Peninsula. Anomalous upward motions in northern East Asia and enhanced moisture transport towards northern East Asia were associated with a northward displacement of the South Asian High, leading to increased precipitation in northern East Asia. However, anomalous downward motions in Central Asia and weakened moisture transport towards southern East Asia and Indochina Peninsula were related to a northward displacement of the South Asian High, resulting in decreased precipitation in Central China, southern East Asia and Indochina Peninsula. A northward migration of the South Asian High induced anomalous cyclone over the Arabian Sea, causing enhanced precipitation in South Asia. Generally, the southward migration of the South Asian High was associated with a weakened East Asian summer monsoon and Indian summer monsoon, and an enhanced southwest monsoon. The spatial-temporal patterns of Asian summer monsoon precipitation during the Holocene can be partially explained by the meridional movement of the South Asian High.