NOAA/AVHRR卫星海表温度在西北太平洋的印证及分析

本文详细分析了TeraScan系统反演NOAA/AVHRR卫星海表温度的过程,解决了反演过程中的海陆匹配问题和云检测过程中的误检、漏检问题,处理得到2002年(5°～45°N)、(105°～150°E)区域内的卫星海表温度数据.利用东北亚地区海洋观测系统NEAR-GOOS提供的现场海表温度数据做比较,印证NOAA/AVHRR海表温度在西北太平洋海域的精度,并分析其误差产生的来源.     

2004年苏门答腊地震前后海面高趋势的变化

利用苏门答腊附近海域T/P、Jason-1测高卫星近20年的海面高连续观测资料,分别计算了该区域(80°E~105°E,5°S~20°N)在2004年苏门答腊大地震前后的海面高变化趋势,并与该区域对应时间段GRACE重力卫星反演的地表质量迁移结果进行比较。研究结果表明,由卫星测高观测资料估算的震区地震前后海平面趋势的变化与卫星重力反演结果基本一致。由于卫星测高沿轨观测具有高精度、高时空分辨率的特性,卫星测高资料估算的海平面趋势变化可以更为准确地反映震区海平面变化的局部特征。还对该区域震后形变特征进行了初步分析。     

利用遥感SST反演上层海洋三维温度场

通过统计相关分析验证了一个简单的温度参数模型在太平洋海域的较好适用性。基于Argo观测资料及WOA09气候态温度数据,采用最大角度法求得此模型的相关参数,并利用高分辨率卫星遥感海表温度反演了太平洋上层海域空间分辨率为1°×1°的气候态月平均三维温度场。与实测资料的比较分析表明反演结果是较为真实可靠的,并可作为海洋数值模式积分的初猜场,为实现现场观测(如:Argo)与卫星观测的优势互补,构建太平洋海域完整的三维温度分析场提供一种新途径。     

VIIRS和AVHRR海表温度场空间精细度估算

对上层海洋次中尺度过程研究至关重要的卫星海表温度(Sea Surface Temperature,SST)场的空间精细度一直未受到足够重视。由于卫星SST产品反演噪声的影响和实测数据的缺乏等原因,目前对卫星SST场空间精细度的研究受到较大限制。本研究开发了一套估算卫星SST场空间精细度的方法,将Suomi National Polar-orbiting Partnership卫星Visible Infrared Imager Radiometer Suite(Suomi-NPP/VIIRS)和NOAA-15卫星Advanced Very High Resolution Radiometer(NOAA-15/AVHRR)Level-2 SST场的空间能量谱与长时间在同一航线反复观测的高空间分辨率实测海温数据的空间能量谱进行了比较。研究发现VIIRS SST场夜间沿扫描方向在1.5~50 km尺度对海表温度空间能量的分布特征和变化趋势描述准确,日变化导致VIIRS白天场次中尺度空间谱能量相对夜晚有所增加。AVHRR SST场空间谱能量在次中尺度相比VIIRS有较大升高。     

连续台风对海表温度和海表高度的影响

利用多卫星观测资料,分析了2008年9月3个连续台风前后的海表温度(SST)和海表高度距平(SSHA)的时空变化特征,并探讨了影响其变化的主要因子。结果表明:(1)3个台风引起了强烈的上升流(1×10-5~150×10-5 m/s),海表显著降温(1~6 ℃),海表高度也有不同程度降低(10~50 cm);(2)台风引起的SST最大降温中心与SSHA负值或中尺度冷涡的区域中心十分吻合,同时台风使得先前存在的海洋中尺度冷涡得到加强;(3)同一区域台风对SST影响程度大小受台风的强度、移动速度以及台风对海面强迫时间等因素控制;(4)在原先SSHA为正值的海域,3个台风连续强迫下使得局地洋面形成一个SSHA为负值的中尺度涡,这与单一"打转"台风强迫海洋生成中尺度涡的现象不同。因此,对于西北太平洋海域而言,频发的台风在中尺度涡生消演变过程中的影响应不容忽视。     

黑潮延伸体海域典型涡旋的次中尺度特征分析*

本文基于卫星遥感资料和高分辨率ROMS(Regional Ocean Modeling System)数值模拟结果, 对黑潮延伸体海域典型中尺度涡旋的次中尺度特征进行了探讨。卫星观测和模拟结果显示, 黑潮延伸体涡旋海域伴随着活跃的次中尺度现象。涡旋演变与多尺度能量分析结果表明, 涡旋海域次中尺度动能的强弱与涡旋海域地转流动能有着密切联系, 锋生可能是涡旋边缘次中尺度动能增强的重要机制。次中尺度现象在中尺度涡旋海域具有沿地转流方向的复杂涡丝状结构特征, 意味着涡旋边缘较强的水平浮力梯度和地转流侧向剪切为次中尺度过程形成与发展提供了有利条件。此外, 垂向结构分析表明, 次中尺度过程能引起较大的垂向速度, 最大可达100m·day^-1, 该垂向速度可以影响至混合层下200m深度处, 对海洋内部的垂向物质能量交换、海—气相互作用等有着重要的影响。     

基于Argo浮标数据的Aquarius数据产品质量评估

Aquarius/SAC-D卫星于2010年6月发射,极大地增强了人类观测海表盐度的能力,因而对理解全球水循环具有重要意义。利用Argo盐度现场观测资料对2014年全球的Aquarius L2产品进行了分析与讨论,结果表明:Aquarius数据盐度值总体偏差为正,但是由于降水和反演法的不完美偏差使得热带海域偏差为负;三大洋中,太平洋盐度反演最为精确,3个波束(beam)中,beam 1反演最准确。另外,还用BP神经网络对Aquarius L2产品的误差进行校正,使均方根误差由0.507减小到0.298。     

南海中尺度涡强度的季节和年际变化分析

为了研究南海中尺度涡强度的季节和年际变化规律,利用Matlab提取50 a(1958~2007年)简单海洋资料同化(Simple Ocean Data Assimilation,SODA)月平均数据集中流场和海表面高度场数据,应用一个涡旋自动探测算法对南海中尺度涡初始生成位置进行分析,并分析了海表面高度异常均方根值的季节变化和年际变化。结果表明:50 a里南海中尺度涡主要分布在吕宋岛西北海域、吕宋岛西南海域和越南以东广大海域,秋、冬季中尺度涡能量较高,春季中尺度涡最弱,中尺度涡强度高值区年际变化明显。从季节变化上看,海面高度异常均方根春、夏季最小,秋冬季最大;从年际变化上看,与同时期Nino3指数有显著负相关,周期大约为3 a。     

基于SMOS卫星数据的海表面盐度模型

海表面盐度是研究海洋对全球气候影响以及大洋环流的重要参量之一,而卫星遥感技术是获取海表面盐度数据的最有效方法.目前,L波段的SMOS和Aquarius/SAC-D遥感卫星正在用于探测海表面盐度,并根据卫星观测数据和物理机制反演出海表面盐度的产品.但在某些近陆地区域,由于淡水流入及陆地射频(RFI)等因素影响,卫星反演盐度的产品精度较低.文中利用“东方红2号”科学考察船的实测数据、SMOS卫星数据,首次针对中国南海海域提出了用贝叶斯网络模型计算海表面盐度,并用验证数据集(实测Argo盐度)对模型进行适应性评估.经过计算,模型误差和验证误差分别为0.47 psu和0.45 psu,而相应的SMOS Level 2产品的精度分别为1.90 psu和1.82 psu.此模型为海表面盐度的计算提供了一个新方法.     

基于OceanDataView的中尺度涡分析研究

以西太平洋海域 2 个中尺度涡为例,利用 AVISO 卫星高度计观测的海平面高度异常(Sea Level Anomaly,SLA)数据、HYCOM 模式的温度、盐度数据及水下滑翔机实测数据,分析了 Ocean Data View 软件(ODV)在实现该区域中尺度涡运动特征规律研究的实用性,探讨了中尺度涡分析处理的关键技术和方法。 结果表明：利用 ODV 软件能够快速绘制海平面高度异常值和海表面流速的平面图,进而准确判别中尺度涡类型、追踪中尺度涡在海表面的水平空间尺度及演化特征;也可绘制任意航迹温、盐深断面图用于分析中尺度涡的垂直结构和判别涡结构类型;同时 ODV 软件也提供了垂直涡结构实测数据与模式数据对比分析模式,为中尺度涡研究提供强有力的分析工具和技术支撑方法。     

Atmospheric Internal Gravity Waves Caused by Tsunamis over Kuril Islands

MODIS (Aqua and Terra) space images of the northwest part of the Pacific Ocean at instants of considerable tsunamis in 2009–2011 have been analyzed. Periodic cloud structures typical for internal gravity waves (IGWs) in the atmosphere have been revealed in the region of the Kuril Islands in five cases. It has been shown that the meteorological conditions observed during those events favored the appearance of such phenomena. The continuous oceanic upwelling in the region of the Kuril–Kamchatka Trench is a favorable factor for IGW generation due to the creation of temperature contrasts observed both in warm and cold seasons between the ground layer of the atmosphere and ocean surface. The estimate of the structure of cloud manifestations of atmospheric waves by satellite images testifies also to the influence of the Kuril Ridge orography on their appearance and propagation over the water area under study. The increase in amplitudes and duration of oscillations caused by the tsunami in the shelf zone can be an auxiliary factor for the IGW generation over coastal territories.     

Surface manifestations of internal waves observed using a land-based video system

This paper presents the results of processing sea-surface optical images in the coastal zone of the Sea of Japan with manifestations of internal gravity waves (IGWs) in the region of the Gamov Peninsula and the results of an analysis of IGW field observations in the same region. The following parameters of IGWs have been determined from the results of processing: their lengths and phase velocities. We calculate the IGW parameters in the region of observations using a mathematical model that takes into account the field data on the vertical stratification of coastal waters and the nonlinearity of the wave process. A comparison of the IGW parameters obtained from model calculations with the parameters obtained from the processing of optical images demonstrates a good agreement between them.     

Propagating tsunami wave and subsequent resonant response signals detected by HF radar in the Kii Channel,Japan

Signals from the tsunami waves induced by the March 11, 2011 moment magnitude (M_w) 9.0 Tohoku-Oki earthquake and from subsequent resonances were detected as radial velocity variability by a high-frequency ocean surface radar (HF radar) installed on the eastern coast of the Kii Channel, at a range of about 1000 km from the epicenter along the eastern to southern coasts of Honshu Island. A time–distance diagram of band-passed (9–200 min) radial velocity along the beam reveals that the tsunami waves propagated from the continental shelf slope to the inner channel as progressive waves for the first three waves, and then natural oscillations were excited by the waves; and that the direction of the tsunami wave propagation and the axis of the natural oscillations differed from that of the radar beam. In addition, spectral analyses of the radial velocities and sea surface heights obtained in the channel and on the continental shelf slope suggest complex natural oscillation modes excited by the tsunami waves.     

基于回归模型的热带气旋条件下的海表降温参数化方案设计

Combining a linear regression and a temperature budget formula, a multivariate regression model is proposed to parameterize and estimate sea surface temperature(SST) cooling induced by tropical cyclones(TCs). Three major dynamic and thermodynamic processes governing the TC-induced SST cooling(SSTC), vertical mixing, upwelling and heat flux, are parameterized empirically using a combination of multiple atmospheric and oceanic variables:sea surface height(SSH), wind speed, wind curl, TC translation speed and surface net heat flux. The regression model fits reasonably well with 10-year statistical observations/reanalysis data obtained from 100 selected TCs in the northwestern Pacific during 2001–2010, with an averaged fitting error of 0.07 and a mean absolute error of 0.72°C between diagnostic and observed SST cooling. The results reveal that the vertical mixing is overall the pre dominant process producing ocean SST cooling, accounting for 55% of the total cooling. The upwelling accounts for 18% of the total cooling and its maximum occurs near the TC center, associated with TC-induced Ekman pumping. The surface heat flux accounts for 26% of the total cooling, and its contribution increases towards the tropics and the continental shelf. The ocean thermal structures, represented by the SSH in the regression model,plays an important role in modulating the SST cooling pattern. The concept of the regression model can be applicable in TC weather prediction models to improve SST parameterization schemes.     

黑海西北部涡旋与环流对跨陆架水交换的影响

涡旋对海洋中的能量传递和物质交换有重要作用。黑海西北部陆坡边缘是长生命周期涡旋经常发生的海域,但涡旋引起的陆架和海盆之间水交换通量的季节性特征,以及海盆边缘环流对跨陆架水交换的作用等方面的研究还不是很充分。本文对黑海西北部陆架区与深海盆区间的跨陆架水交换进行了研究,利用高分辨率三维原始方程模式模拟的温、盐、流等资料,结合涡旋自动探测方法,统计了黑海西北部海域的涡旋活动,研究了涡致跨陆架水交换的季节性特征,计算对比了2002年到2010年间海盆边缘环流与涡旋对跨陆架水交换通量的各自贡献。结果表明:黑海西北部地区海盆边缘环流强度与跨陆架进、出通量的相关系数分别为0.57和0.67,海盆边缘环流位置与跨陆架交换量的相关系数为0.52;海盆边缘环流强度与位置的季节性变化导致了黑海西北部跨陆架通量的季节性变化。黑海西北部地区表层3月到8月之间涡旋所引起跨陆架交换量约占了跨陆架交换总量的16%~31%;涡致跨陆架通量也具有季节性特征。文中对单个涡旋进行了详细研究:2005年5月5日到2005年7月20日之间在黑海西北部存在一个直径最大值时达到120 km的反气旋式涡旋,涡旋存在期间完成了从陆架区向深海区的水体传输,相当于黑海西北陆架区水体积的30.9%。     

A study of internal solitary waves observed on the continental shelf in the northwestern South China Sea

Based on in-situ time series data from the acoustic Doppler current profiler (ADCP) and thermistor chain in Wenchang area, a sequence of internal solitary wave (ISW) packets was observed in September 2005, propagating northwest on the continental shelf of the northwestern South China Sea (SCS). Corresponding to different stratification of the water column and tidal condition, both elevation and depression ISWs were observed at the same mooring location with amplitude of 35 m and 25 m respectively in different days. Regular arrival of the remarkable ISW packets at approximately the diurnal tidal period and the dominance of diurnal internal waves in the study area, strongly suggest that the main energy source of the waves is the diurnal tide. Notice that the wave packets were all riding on the troughs and shoulders of the internal tides, they were probably generated locally from the shelf break by the evolution of the internal tides due to nonlinear and dispersive effects.     

Internal tide and nonlinear internal wave behavior at the continental slope in the northern south China Sea

A field program to measure acoustic propagation characteristics and physical oceanography was undertaken in April and May 2001 in the northern South China Sea. Fluctuating ocean properties were measured with 21 moorings in water of 350- to 71-m depth near the continental slope. The sea floor at the site is gradually sloped at depths less than 90 m, but the deeper area is steppy, having gradual slopes over large areas that are near critical for diurnal internal waves and steep steps between those areas that account for much of the depth change. Large-amplitude nonlinear internal gravity waves incident on the site from the east were observed to change amplitude, horizontal length scale, and energy when shoaling. Beginning as relatively narrow solitary waves of depression, these waves continued onto the shelf much broadened in horizontal scale, where they were trailed by numerous waves of elevation (alternatively described as oscillations) that first appeared in the continental slope region. Internal gravity waves of both diurnal and semidiurnal tidal frequencies (internal tides) were also observed to propagate into shallow water from deeper water, with the diurnal waves dominating. The internal tides were at times sufficiently nonlinear to break down into bores and groups of high-frequency nonlinear internal waves.     

基于多源遥感数据的日本海内波特征研究

日本海特殊的地理位置和复杂的地形使得该海域内波表征极为复杂,遥感是大范围观测内波的有效手段,已被广泛应用于内波的探测研究。本文利用MODIS、GF-1和ENVISAT ASAR遥感影像,开展了日本海内波特征研究。通过提取内波波峰线,生成了日本海内波空间分布图;获取了内波的波峰线长度和传播速度,并基于非线性薛定谔方程反演了内波振幅。研究结果表明,日本海内波分布范围宽广,不仅大陆架沿海区内波分布密集,深海盆地也探测到了大量内波;日本海北部45°N附近海域有少量内波出现,利用高分影像探测到朝鲜陆架浅海区有大量小尺度内波,大和海盆、大和隆起的西南部海域没有发现内波。日本海内波波峰线长达100多千米,深海区的传播速度大于1 m/s;浅海区内波振幅约10 m左右,深海区可达60 m以上。     

Altimetric Algorithm and Errors of Ocean Altimetry Using GNSS Reflection Signals

As a new remote sensing technology, the global navigation satellite system (GNSS) reflection signals can be used to collect the information of ocean surface wind, surface roughness and sea surface height. Ocean altimetry based on GNSS reflection technique is of low cost and it is easy to obtain large amounts of data thanks to the global navigation satellite constellation. We can estimate the sea surface height as well as the position of the specular reflection point. This paper focuses on the study of the algorithm to determine the specular reflection point and altimetry equations to estimate the sea surface height over the reflection region. We derive the error equation of sea surface height based on the error propagation theory. Effects of the Doppler shift and the size of the glistening zone on the altimetry are discussed and analyzed at the same time. Finally, we calculate the sea surface height based on the simulated GNSS data within the whole day and verify the sea surface height errors according to the satellite elevation angles. The results show that the sea surface height can reach the precision of 6 cm for elevation angles of 55° to 90°, and the theoretical error and the calculated error are in good agreement.     

“桑吉”号泄漏物质扩散与漂移数值模拟预测

基于ROMS(Regional Ocean Modeling System)模式,对西北太平洋海域进行了水平分辨率高达4km的水动力环境数值模拟,该分辨率可以很好地分辨我国东海陆架环流以及中尺度涡旋等过程,此外模式考虑了8个分潮,模式结果很好地再现了黄、东海陆架环流等。基于模式结果,对"桑吉"号泄漏物质可能的扩散和迁移轨迹进行了数值模拟分析。在"桑吉"号沉船位置的表、底Ekman层内,释放拉格朗日粒子和示踪物来示踪"桑吉"号泄漏物质的可能影响范围。拉格朗日粒子和示踪物模拟结果表明:在未来3个月,"桑吉"号泄漏物质对我国黄海的影响较小,其主要随着对马暖流进入日本海和随着黑潮进入日本九州以南的太平洋海域。随着冬、春的季节转换,三个月后,北风会减弱,减弱风场的试验表明,风场减弱会减少泄漏物质向黄海的输送。5月份后黄海冷水团逐渐形成,由于斜压效应,在黄海深层水中会逐渐建立起气旋式环流,从而进一步阻碍了"桑吉"号泄漏物质向黄海的输送,该气旋式环流有利于"桑吉"号泄漏物质通过对马海峡向日本海的输送,而会抑制底层泄漏物质向我国黄海西侧的输送。