由TOPEX/Poseidon和Jason-1/2探测的1993—2012中国海海平面时空变化

Temporal-spatial variations of sea level over China seas derived from altimeter data of TOPEX/Poseidon,Jason-1 and Jason-2 from 1993 to 2012

海平面变化是社会经济发展和科学研究的重要内容.利用1993年1月至2012年12月共20年的TOPEX/Poseidon、Jason-1和Jason-2卫星测高数据,研究中国海海平面的时空变化.首先通过三颗卫星伴飞阶段数据得到三颗卫星之间的逐点海面高系统偏差,进行逐点海面高改正,建立了20年的中国海海面高异常时间序列.分析了中国海海面高异常空间分布,给出了1月到12月月均平均海平面异常的空间变化规律.分析了中国海海面高异常的时变规律,分别给出了年、季度和月的海面上升速率.利用小波分析研究了中国海海面高异常周期变化规律,分别给出了渤海、黄海、东海和南海的海面高变化周期.讨论了ENSO对海面高异常的影响.

Variations of sea level are an important issue associated with global climate change,especially global warming.The sea level rising may lead to serious impact on the social-economic development of a country.Global oceans are continuously observed by altimetry satellite missionsfor more than 20 years.We use altimeter data of TOPEX/Poseidon（T/P）,Jason-1and Jason-2from 1993 to 2012to study the sea level change over China seas.China seas located in the western Pacific Ocean are selected as the study area.T/P MGDR data of 11 to 364cycles span January 1993 to August 2002.Jason-1GDR data of 1to 259 cycles span January 2002 to January 2009.Jason-2 GDR data of 1to 165 cycles span July 2008 to December 2012.Southern oscillation index（SOI）time series span January 1993 to December2012.Altimetry data in the tandem stages are used to calibrate biases of sea level anomalies（SLAs）from T/P,Jason-1and Jason-2point by point.The spatial distribution of China seas′level change is studied with the continuous tension spline method.Temporal variations of China seas′level are analyzed with the linear fitting method and the wavelet analysis.Relationships between the El Nio-Southern Oscillation（ENSO）and sea level changes of the South China Sea and the East China Sea are studied with the correlation analysis.By unifying altimetry data point by point in tandem stages,the mean differences of sea level heights for Jason-1vs T/P and Jason-2vs Jason-1are 0.21 cm and 0.03 cm,respectively.SLA time series are constructed after corrections of sea level biases from 1993 to 2012.In general,the mean SLA is positive over China seas.SLAs are higher in the south than those in the north,and lower in the west than those in the east.SLAs are negative over the western Bohai Sea,the northern Yellow Sea,the northern Taiwan Strait and the North Bay.SLAs rise with the increasing longitude and decrease with the growing latitude.This spatial distribution of SLAs over China seas is related to the water flux,sea surface wind stress,oceanic dynamics,monsoon,Kuroshio and ENSO.The mean rising rate of sea level for the 20 years is 4.64mm·a-1 over the whole study area.Sea levels are rising in the Bohai Sea,Yellow Sea,East China Sea and South China Sea with rising rates 4.44mm·a-1,2.37mm·a-1,3.02mm·a-1 and 4.25mm·a-1,respectively.The annual sea level variation is obvious in the study area.The sea level is higher in summer and autumn than in winter and spring.The main cycles of sea level change include one year and 9years over the whole seas.There are also minor cycles of 0.5years,1.5years,2years and 4years.Cyclical changes of sea level are related to the geographical position,climate,oceanic dynamics and submarine topography.The correlation coefficients between SOIs and SLAs of the South China Sea and the East China Sea are 0.39 and 0.02,respectively.The correlation coefficient is 0.44 after the two-month delay for the South China Sea.The correlation coefficient is 0.17 after the four-month delay for the East China Sea.This indicates that the sea level change over the South China Sea may be largely affected by ENSO.Altimetry data of T/P,Jason-1and Jason-2are processed to study the sea level change over China seas from 1993 to 2012.We used the altimetry data in tandem stages to calibrate the sea level biases of these three missions to achieve the seamless SLAs point by point.The spatial distribution of sea level change is given with the continuous tension spline method.The sea level is generally rising at the mean rate of 4.64mm·a-1 over China seas in these 20 years.The sea level variations change with different seas and seasons.The mean rising rates are 4.44mm·a-1,2.34mm·a-1,3.02mm·a-1 and 4.25mm·a-1 over Bohai Sea,Yellow Sea,East China Sea and South China Sea,respectively.Temporal-spatial change of sea level over the study area is related to oceanic dynamics,submarine topography,monsoon,Kuroshio and ENSO.The main cycles of sea level change are one year and 9years as derived from the wavelet analysis.El Nio and La Nia events make stronger effects on sea level variations over the South China Sea than the other seas.