南海海道再探

以海道针经记载的南海针路为依据,南海海道可分解为西洋海道、海峡海道、东洋海道进行讨论,并以《郑和航海图》中记载的针路分析明代初年西洋海道的走向和针位,同时根据海道针经中记载的有关针路叙述西洋海道、海峡海道和东洋海道的拓展历史,以航海史的视域尽可能地、较全面地展示我国古代航海家在南海及其周边海域展开的活动。

南海海道初探

我国古代称海上通道为海道。我国古代海上丝绸之路中最重要的一段经过南海的海道即南海海道,分为西洋海道、东洋海道、海峡海道、更路海道。西洋海道位在南海西部,为我国古代“下西洋”的主海道,由我国东南沿海过七洲列岛南下,沿海南岛东海岸航行,经大洲岛出洋到中南半岛、爪哇岛等处;东洋海道从闽粤沿海起航,经澎湖列岛或东沙群岛,驶向菲律宾群岛、苏禄海及加里曼丹岛各处;海峡海道则为穿过琼州海峡进入北部湾,经白龙尾岛驶向越南北部的海道。又有海道从海南岛东南部起航,经西沙群岛、中沙群岛和南沙群岛,驶向南海周边国家和地区,这些分布在南海诸岛中的海道,留存有大量的更路簿,故称之为更路海道。南海海道的开拓史就是南海发现、命名和管理的历史。从涨海、石塘(堂)到千里长沙、万里石塘、南澳气,是我国古代航海家随着航海能力的提升从而形成对南海认识从朦胧到清晰的过程,是历史的进步和必然。

Impacts of Indonesian Throughflow on seasonal circulation in the equatorial Indian Ocean

Impacts of the Indonesian Throughflow(ITF) on seasonal circulation in the equatorial eastern Indian Ocean are investigated using the ocean-only model LICOM by opening and closing ITF passages. LICOM had daily forcing from NCEP reanalysis data during 2000–2011. It can reproduce vertical profiles of mean density and buoyancy frequency of World Ocean Atlas 2013 data. The model also simulates well annual oscillation in the central Indian Ocean and semiannual oscillation in the eastern Indian Ocean of sea level anomalies(SLA) using satellite altimeter data, as well as the semiannual oscillation of surface zonal equatorial currents of Ocean Surface Current Analyses Real Time current data in the equatorial Indian Ocean. The wave decomposition method is used to analyze the propagation and reflection of equatorial long waves based on LICOM output. Wave analysis suggests that ITF blockage mainly influences waves generated from the Indian Ocean but not the Pacific Ocean, and eastern boundary reflections play an important role in semiannual oscillations of SLA and zonal current dif ferences in the equatorial Indian Ocean associated with ITF. Reconstructed ITF-caused SLA using wave decomposition coefficient dif ferences between closed and open ITF-passage experiments suggest both Kelvin and Rossby waves from the first baroclinic mode have comparable contributions to the semiannual oscillations of SLA diff erence. However, reconstructed ITFcaused surface zonal currents at the equator suggest that the first meridional-mode Rossby wave has much greater contribution than the first baroclinic mode Kelvin wave. Both reconstructed sea level and zonal currents demonstrate that the first baroclinic mode has a greater contribution than other baroclinic modes.

Surface thermal centroid anomaly of the eastern equatorial Pacific as a unified Nio index

By analyzing the variability of global SST （sea surface temperature） anomalies, we propose a unified Nifio index using the surface thermal centroid anomaly of the region along the Pacific equator embraced by the 0.7~C contour line of the standard deviation of the SST anomalies and try to unify the traditional Nifio regions into a single entity. The unified Nifio region covers almost all of the traditional Nifio regions. The anomaly time series of the averaged SST over this region are closely correlated to historical Nifio indices. The anomaly time series of the zonal and meridional thermal centroid have close correlation with historical TNI （Trans-Nifio index） indices, showing differences among E1 Nifio （La Nifia） events. The meridional centroid anomaly suggests that areas of maximum temperature anomaly are moving meridionally （although slightly） with synchronous zonal movement. The zonal centroid anomalies of the unified Nifio region are found helpful in the classification of the Eastern Pacific （EP）/Central Pacific （CP） types of E1 Nifio events. More importantly, the zonal centroid anomaly shows that warm areas might move during a single warming/cooling phase. All the current Nifio indices can be well represented by a simple linear combination of unified Nifio indices, which suggests that the thermal anomaly （SSTA） and thermal centroid location anomaly of the unified Nifio region would yield a more complete image of each E1 Nifio/ La Nina event.