热带太平洋-印度洋海温联合模及其气候影响

本文基于观测资料和LICOM2.0模拟结果的分析研究，简要介绍讨论了太平洋—印度洋海温(异常)联合模(PIOAM)的存在、特征、演变及其影响等问题。热带太平洋—印度洋区域乃至全球范围的海表温度异常(SSTA)资料进行EOF分解，都清楚表明其第一分量在热带太平洋—印度洋的空间形态与太平洋—印度洋海温(异常)联合模(PIOAM)非常相似，说明PIOAM是热带太平洋—印度洋实实在在存在的一种海温异常模态。对应PIOAM的正、负位相，热带印度洋和西太平洋地区的夏季(JJA)850 hPa距平风场有近乎相反的异常流场形势；对流层低层的Walker环流支和亚洲夏季风都出现了不同特征的(近乎相反)异常；在PIOAM正(负)位相将使得100 hPa的南亚高压位置偏东(西)。对热带太平洋和印度洋温跃层曲面上的海温异常(为了方便将其称为SOTA)进行EOF分解，发现其第一模态也是一个三极子模态，即当赤道中西印度洋大部分海域与赤道中东太平洋大部分海域偏暖(偏冷)时，赤道东印度洋和赤道西太平洋大部分海域则偏冷(偏暖)；它与太平洋—印度洋表层的PIOAM十分类似，也表明PIOAM在海洋次表层也是存在的。高分辨海洋环流模式LICOM2.0的模拟结果，无论是对太平洋—印度洋表层还是次表层的PIOAM的特征和演变都刻画得很好，这从另一个角度进一步说明PIOAM是热带太平洋—印度洋实际存在的一种海温变化模态。PIOAM正、负位相不仅对亚洲及西太平洋地区的天气气候有非常不一样的影响(不少地方有反向的特征)，还会对南北美洲和非洲一些地区产生不同影响；而且其影响与单独的厄尔尼诺(El Ni?o)及印度洋偶极子(IOD)都不尽相同。

Tropical Pacific-Indian Ocean Associated Mode and Its Climatic Impacts

Based on observational data and simulation results by LICOM2.0 model, a synthetic introduction with regard to the existence, feature, evolution and impacts of the Pacific-Indian Ocean associated mode (PIOAM) are given in this paper. EOF analyses of SSTA both in the tropical Pacific-Indian Ocean and in the global ocean show that the EOF-1 pattern in the tropical Pacific-Indian Ocean is perfectly similar to the PIOAM, which indicates that the PIOAM is a very real mode of oceanic temperature anomalies in the tropical Pacific-Indian Ocean. Corresponding to positive and negative phases of the PIOAM, the wind field anomalies at 850 hPa over the tropical Pacific-Indian Ocean in the summer (JJA) are almost opposite, the Walker circulation at the lower troposphere and the Asian summer monsoon display different anomalous (close to opposite) features. In positive (negative) phase of the PIOAM, the South Asia high is located to the east (west) of its normal position. EOF analyses of subsurface oceanic temperature anomalies (SOTA) at the thermocline camber in the tropical Pacific-Indian Ocean reveals that the EOF-1 is a triangle mode similar to the PIOAM at the sea surface. This result suggests that the PIOAM also occurs in the oceanic subsurface. The numerical simulation by the high resolution oceanic circulation model LICOM2.0 shows that when the tropical central-western Indian Ocean and central-eastern Pacific are abnormally warmer/colder, the tropical eastern Indian Ocean and western Pacific are correspondingly colder/warmer. This result further confirms that the tropical PIOAM is an important mode that is significant in both sea surface temperature anomaly (SSTA) field and subsurface ocean temperature anomaly (SOTA) field. The positive and negative phases of the PIOAM not only affect the weather / climate in Asian and west Pacific regions, but also have impacts in south-north American and Africa regions. The influences of the PIOAM are different from that of ENSO and Indian Ocean Dipole (IOD).