-
There have been a number of applications of satellite altimetry to seasonal and interannual sea level variability in the South China Sea. However, these applications usually exclude shallow waters along the coast, with one of the concerns being large aliased tide-correction error. In this study the authors analyzed 14 years of merged satellite altimeter data to obtain the amplitude and phase of the semi-annual cycle and to examine the variation at the K1 alias frequency (close to the semi-annual frequency). The results indicate that the amplitude of the semi-annual cycle ranges from 3-7 cm, substantial compared with that of the annual cycle; while the amplitude at the K1 alias frequency (error of the K1 tidal correction) is essentially 1 cm only. Altimeter-derived semi-annual cycle is in good agreement with that from independent tide-gauge observations, pointing to the competent ability of satellite altimetry in observing semi-annual sea level variations in the South China Sea.
2009年05期 v.28 1-5页 [查看摘要][在线阅读][下载 480K] Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early-austral-winter blooms are in phase with seasonal strengthening of the Leeuwin Current and its eddy field. From satellite altimeter and ocean color data , anticyclonic eddies are found to entrain the high phytoplankton biomass waters from the shelf and transport them offshore into the oligotrophic, subtropical marine environment. The late-austral-autumn/early-austral-winter blooms are highly linked with enhanced horizontal mixing by mesoscale eddies in the region, as derived from the finite-size Lyapunov exponent (FSLE) of the surface geostrophic flow field obtained from satellite altimeter data. The pathways of cross-shelf exchanges, which are mostly driven by the mesoscale eddies, are revealed with coalescing of the FSLE of the surface geostrophic flow field and the satellite chlorophyll a images.
2009年05期 v.28 6-10页 [查看摘要][在线阅读][下载 626K] -
The European Space Agency will launch the first salinity satellite for remotely sensing the global soil moisture and ocean salinity (SMOS) at a sun-synchronous orbit in 2009. One of the payloads on the satellite is a synthetic aperture microwave radiometer (MIRAS), which is an innovative instrument designed as a two-dimensional (2D) interferometer for acquiring brightness temperature (TB) at L-band (1.4 GHz). MIRAS allows measuring TB at a series of incidences for full polarizations. As the satellite travels, a given location within the 2D field of view is observed from different incidence angles. The authors develop a new scheme to retrieve the sea-surface salinity (SSS) from SMOS's TB at multi-incidence angles in a pixel, utilizing the properties of emissivity changing with incidence angles. All measurements of a given Stokes parameter in a pixel are first fitted to incidence angles in three order polynomial, and then the smoothed data are used for retrieving the SSS. The procedure will remove the random noise in TB greatly. Furthermore, the new method shows that the error in retrieved SSS is very sensitive to the system biases in the calibrated TB of the sensor, but the error in the retrieval is also a system bias, which can be corrected by post-launch validation. Therefore, this method may also serve as a means to evaluate the calibration precision in TB.
2009年05期 v.28 11-17页 [查看摘要][在线阅读][下载 492K] To retrieve sea-surface salinity (SSS) from radiometer data at 1.4 GHz, auxiliary data of sea-surface temperature (SST), surface roughness and meteorological variables are needed. The authors study oceanic passive polarimetric microwave remote sensing using 1.4 GHz and 10.7 GHz bands. A set of algorithms are developed for 1.4 GHz and 10.7 GHz microwave polarimetric radiometer at 50° incidence angle to retrieve wind vector, as well as other geophysical parameters, such as SSS, SST, atmospheric volumes of water vapor and liquid water. Idealized retrievals are conducted using 2 324 simulated brightness temperatures of full Stokes parameters at 1.4 GHz and 10.7 GHz. Results indicate that SSS, SST, sea-surface wind speed, direction, atmospheric volumes of water vapor and liquid water can be inversed at the same time. This suggests an alternative way for SSS remote sensing.
2009年05期 v.28 18-28页 [查看摘要][在线阅读][下载 877K] -
Marginal water east of the Hainan Island is where internal waves occur frequently. Few studies have been conducted on these internal waves so far, and their formation mechanism remains unclear. In this study, the author uses the China-Brazil Earth Resources Satellite data (CBERS) to detect and calculate the distribution, direction, wavelength and amplitude of internal waves in this area. The results show that the direction of these internal waves is offshore and their wavelength is about 150-200 m. The internal waves can be postulated as formed by upwelling or reversed tide.
2009年05期 v.28 29-34页 [查看摘要][在线阅读][下载 358K] - 汪文琦;董强;商少凌;吴璟瑜;李忠平;
基于42组不同年份不同季节获得的遥感反射率、水体各组分吸收系数的实测数据,对QAA(Quasi-Analytical Algorithm)和GSM(Garver-Siegel-Maritorena)算法在寡营养的南海和富营养的福建沿岸两种不同类型水体的吸收系数反演进行了检验。以水样测量值为参考,两种算法在本研究水体中的反演成效与他人在其它水域的研究结果相当。QAA算法在南海的反演成效高于福建沿岸水体。对于443nm的总吸收系数a(443),南海的对数均方根误差RMSE为0.044,平均相对误差ε为7.9%,对数平均偏差δ为0;福建沿岸水体RMSE=0.190,ε=30.6%,δ=-0.167。GSM算法在两类水体的反演成效类似,a(443)之RMSE和ε,南海分别为0.156和27.7%,福建沿岸分别为0.146和32.1%;但从a(443)的δ值看,其在南海反演值低于实测值(δ=-0.142),在福建沿岸则略呈高于实测值(δ=0.016)。两种算法中的部分经验参数与实测值之间的差异是产生反演误差的主要原因,为了提高反演精度,对算法中经验参数的更进一步区域化调整可能是必要的。
2009年05期 v.28 35-42页 [查看摘要][在线阅读][下载 562K] - 刘大召;陈楚群;刘汾汾;弓洁琼;
利用遥感技术估测水体中悬浮泥沙的浓度已经成为一门成熟的技术,但将其应用于河口地区悬浮泥沙的监测仍然存在一些限制。限制之一是遥感数据(例如MODIS)的空间分辨率太低,不适合应用于河口等狭小水域的监测。相比较而言,Hyperion高光谱遥感数据有196个波段,覆盖400—2500nm的光谱范围,光谱分辨率为10nm,空间分辨率为30m,其高光谱分辨率及高空间分辨率,显示了其在河口水体悬浮泥沙遥感中的巨大潜力。利用2006年12月4号的Hyperion数据、同步实测的高光谱数据及悬浮泥沙浓度数据,对珠江口海域悬浮泥沙浓度进行了研究。利用混合光谱分解模型计算了珠江口悬浮泥沙浓度的分布。分析结果表明,混合光谱分解模型可以作为遥感监测水体悬浮泥沙浓度的定量模型。
2009年05期 v.28 43-48页 [查看摘要][在线阅读][下载 358K] - 黄卓;徐海明;杜岩;谢强;
通过分析ICOADS海洋气象资料,结合ISCCP短波辐射和OISST海面温度,研究并探讨了ENSO等大尺度海气相互作用过程背景下南海海表面温度(SST)的年际变化。研究表明,南海SSTA的年际变化和ENSO关系密切,并且分为两个阶段。以增暖事件为例,在厄尔尼诺(ElNio)发生年的冬季和消亡年的夏季,南海出现了两次显著增暖。第一次增暖出现在ElNio盛期,是ElNio影响的一部分,这时南海云量减少,净太阳辐射通量增加,SST上升。第二次增暖出现在ElNio结束后的夏季,不是ElNio直接作用的结果;这时夏季风减弱,一方面使得海洋的潜热损失减少,另一方面减弱了越南东部沿岸的上升流,两者的共同作用导致SST增加。
2009年05期 v.28 49-55页 [查看摘要][在线阅读][下载 563K] - 莫慧尔;俞永强;刘海龙;林鹏飞;
利用LASG/IAP发展的一个0.25°×0.25°高分辨率太平洋-印度洋海盆环流模式初步分析了模式在太平洋区域的模拟结果,并与海洋同化资料的数据以及前人的研究结果作比较,检验此模式对该区域平均气候态、年际变化的模拟能力。分析表明,模式较好地再现了海表温度(SST)分布、赤道温跃层和纬向流结构、赤道流系分布形态、海表高度以及正压流函数空间分布特征;同时,对显著的El Nio和La Nia事件的模拟等方面与Simple Ocean Data Assimilation(SODA)2.0.2版本结果相近。此外,模式模拟北赤道流(NEC)分叉点位置的季节和年际变化以及吕宋海峡流量的年际变化与已有研究结果基本一致。进一步分析还发现,在年际尺度上,NEC分叉点位置和吕宋海峡流量与ENSO密切相关。
2009年05期 v.28 56-65页 [查看摘要][在线阅读][下载 1545K] - 张玉红;徐海明;杜岩;王东晓;
采用SODA海洋同化产品的月平均资料分析了阿拉伯海东南海域表层盐度的季节变化特征,发现局地海面淡水通量不能解释盐度的变化。两个典型区域的表层海水盐度收支分析表明,海洋的平流输送是造成阿拉伯海东南海域盐度冬季降低、夏季升高的主要原因,而淡水通量仅在夏季印度西侧沿岸区域造成盐度降低。冬季,东北季风环流将孟加拉湾北部的低盐水向西输送到阿拉伯海,然后向北输送,使表层海水盐度降低;夏季,西南季风环流把阿拉伯海西北部的高盐水向南、向东输送,使阿拉伯海东南海域盐度升高。受地理位置因素的影响,阿拉伯海东南海域表层盐度的变化冬季明显强于夏季。
2009年05期 v.28 66-74页 [查看摘要][在线阅读][下载 775K] - 刘祥翠;刘海龙;李薇;林鹏飞;
利用Argo浮标资料,估计了2003—2007年期间印度尼西亚贯穿流(ITF)出口处114.5°E断面上层(0—1000m)的地转流,并与WOA05资料进行对比。在114.5°E断面上9.5°—18.5°S之间,依据Argo资料计算的上层(0—1000m)地转流年平均输送为4.2Sv(1Sv=106m3·s-1),比依据WOA05资料计算的流量大0.5Sv左右,与前人对IX1断面的估算接近。依据Argo资料计算的ITF的季节变化也与WOA05比较一致,最大输送都出现在7月份,可以达到10Sv,而冬季二者差异较大。比较了盐度资料的差异以及114.5°E断面南侧缺测对估计ITF地转流输送的影响,发现盐度资料的改善可以改进对ITF地转输送量的估计,而断面南侧的缺测对ITF年平均输送的影响较小。因此,Argo资料可以作为监测ITF输送量的一种有效手段,特别是用于年平均流量的研究。
2009年05期 v.28 75-82页 [查看摘要][在线阅读][下载 1012K] - 范磊;刘秦玉;
利用超前滞后相关分析研究了西太平洋副热带高压与海表面温度异常的关系。选取各关键海区分析海温与西太平洋副热带高压在不同时段上的超前滞后相关,结果表明,冬季东太平洋海温与滞后其2—3个月的副高异常达最大正相关,热带印度洋海温异常与冬季同期副高异常的正相关最显著;西太平洋海温在冬春季与同期的副高负相关最显著;北太平洋海温在冬春季滞后副高1—2个月时存在负相关,大西洋暖池区6月与西太平洋副热带高压的同期正相关最大;对南太平洋来说,冬季的西太平洋副热带高压与从前秋到春季的SST都存在最大负相关。海表温度的异常主要解释冬春季的西太平洋副热带高压异常,而对于夏秋季副热带高压,SST的作用比较有限。
2009年05期 v.28 83-88页 [查看摘要][在线阅读][下载 457K] 下载本期数据