西太平洋副热带高压与海温关系的年代际变化及模式预测能力研究

发布时间：2018-09-18 18:03

【摘要】：西太平洋副热带(WPSH)与海温外强迫因子发生了明显的年代际变化。然而,WPSH与海温因子的关系是否发生了年代际变化目前并不清楚。因此,本文基于NCEP/NCAR和NOAA再分析资料,利用亚-澳季风区850hPa位势高度距平场经验正交函数(EOF)前两个模态表征WPSH,分析了EOF主模态与海温因子关系的年代际变化。结果表明,EOF前两个模态与海温外强迫因子大约在1976-1977和1993-1994年发生了明显的年代际变化。根据年代际变化年份,划分了三个时段,对比研究EOF主分量(PC)在三个时段对应的环流异常场,发现三个时段的PCs对应的SSTA和850hPa异常风场特征都不相同,且具有明显的年代际变化。正第一主分量(PC1)在三个时段的春季和夏季都对应赤道中东平洋暖海温、热带印度洋暖海温和西北太平洋冷海温。夏季热带印度洋暖海温“电容器效应”的放电过程在1978-1992和1995-2013两个时段被下沉气流明显抑制,使其对西北太平洋反气旋(WNPAC)不起作用。正第二主分量(PC2)在三个时段的春季和夏季都对应热带印度洋、海洋性大陆附近海区、西北太平洋暖海温和北太平洋冷海温,在夏季对应显著的赤道中东太平洋冷海温,而只在1954-1975时段春季对应显著的正位北大西洋三极子(NAT)。1995-2013时段的春季北太平洋冷海温上空的异常反气旋加速了El Ni?o向La Ni?a位相转变。1954-1975时段的春季NAT对WNPAC的增强作用被热带北大西洋暖海温引起的对流层温度正异常在一定程度上抵消了。东亚夏季环流变化对中国夏季降水的年际变化有重要影响,而热带海温对东亚夏季环流异常有至关重要的作用,因此需要进一步理解季节预测模式对东亚夏季环流的预测能力,以及对东亚夏季环流与热带海温关系的刻画能力。利用1991-2013年美国国家环境预测中心(NCEP)、中国气象局国家气候中心(NCC)和日本东京气候中心(TCC)的三个季节预测模式(CFS V2、BCC_CSM V2和MRI-CGCM)和NCEP/NCAR再分析资料,定量评估了模式对东亚夏季风(EASM)和WPSH强度的预测能力。在此基础上,分析了模式预测的EASM和WPSH对热带海温异常的响应能力,以及ENSO事件对EASM和WPSH预测的影响,阐述了预测误差产生的原因。结果表明:整体而言,三个模式对EASM和WPSH的预测技巧较高,但TCC模式对WPSH的预测技巧相对较低。三个模式预测的850hPa风场在西北太平洋存在一个异常气旋,使得预测的EASM偏强和WPSH偏弱。同时,二者的年际变率整体比观测小。三个模式预测的EASM和WPSH对热带海洋海温异常的响应随季节演变特征与观测比较接近,但NCEP模式和TCC模式预测的EASM对前期热带太平洋和前期、同期热带印度洋的海温异常响应要强于观测,NCC模式预测的EASM对前期和同期的热带太平洋的海温异常响应明显比观测强。此外,三个模式预测的WPSH对前期和同期的热带太平洋、热带印度洋和热带大西洋的海温异常响应明显强于观测。三个模式预测的EASM和WPSH在ENSO年的平均绝对误差(MAE)整体而言要比正常年的小很多,NCEP模式和NCC模式预测的EASM和WPSH的MAE在La Ni?a年和El Ni?o年差别不大,而TCC模式预测的EASM和WPSH的MAE在El Ni?o年比在La Ni?a年大很多,表明ENSO事件是东亚夏季环流重要的可预报源。
[Abstract]:However, it is not clear whether the relationship between WPSH and SST has undergone interdecadal variations. Therefore, based on NCEP/NCAR and NOAA reanalysis data, the empirical orthogonal function (EOF) of 850 hPa geopotential height anomalies over the Asian-Australian monsoon region is used in this paper. The interdecadal variations of the relationship between EOF main mode and SST factor are analyzed. The results show that the first two modes of EOF and SST forcing factor have obvious interdecadal variations from 1976 to 1977 and 1993 to 1994. According to the interdecadal variations, three periods are divided and the EOF principal component (PC) pairs are compared in three periods. It is found that the SSTA and 850 hPa anomalous wind fields corresponding to PCs in the three periods are different and have obvious interdecadal variations. The discharge process of the "capacitor effect" of the warm sea surface temperature (SST) was obviously suppressed by the subsidence currents during 1978-1992 and 1995-2013, which made it impossible for the Northwest Pacific anticyclone (WNPAC). The positive second principal component (PC2) corresponds to the tropical Indian Ocean in spring and summer in three periods, the warm SST in the sea area near the oceanic continents, and the warm SST in the Northwest Pacific Ocean. The cold sea surface temperature over the North Pacific corresponds to a significant equatorial central and Eastern Pacific cold sea surface temperature in summer, while the anomalous anticyclone over the cold sea surface temperature over the North Pacific corresponds to a significant positive North Atlantic Tripole (NAT) only in spring 1954-1975. The phase transition from El Ni?O to La Ni?A is accelerated by the anomalous anticyclone over the cold sea surface temperature over the North Pacific in spring 1995-2013. The enhancement is offset to some extent by the positive anomaly of the tropospheric temperature caused by the tropical North Atlantic warm sea surface temperature. Summer circulation changes in East Asia have an important impact on the interannual variability of summer precipitation in China, while the tropical sea surface temperature plays an important role in the anomaly of summer circulation in East Asia. Therefore, it is necessary to further understand the seasonal prediction model. The predictive ability of East Asian summer circulation and the descriptive ability of the relationship between East Asian summer circulation and tropical SST are studied. Three seasonal prediction models (CFS V2, BCC_CSM V2 and MRI-CGCM) and NCEP/NCAR are used to subdivide the East Asian summer circulation into 1991-2013 NCEP, NCC and TCC. On this basis, the response ability of EASM and WPSH to tropical SST anomalies and the influence of ENSO events on EASM and WPSH prediction are analyzed. The causes of prediction errors are explained. M and WPSH have higher prediction skills, but the TCC model has lower prediction skills for WPSH. The 850 hPa wind field predicted by the three models has an anomalous cyclone in the Northwest Pacific, which makes the prediction of EASM stronger and WPSH weaker. The response of EASM predicted by NCEP model and TCC model is stronger than that predicted by observation in the early tropical Pacific and the early tropical Indian Ocean, and the response of EASM predicted by NCC model to the early and contemporary tropical Pacific SSTA is stronger than that of observation. The mean absolute error (MAE) of EASM and WPSH predicted by the three models in ENSO year is much smaller than that predicted by normal year. The MAE of EASM and WPSH predicted by NCEP and NCC models in La Ni?A and El N? There is little difference in i? O year, while the EASM and WPSH MAE predicted by TCC model are much larger in El Ni? O year than in La Ni? A year, indicating that ENSO event is an important predictable source of summer circulation in East Asia.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P424;P731.11

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