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1.
基于Argo浮标的热带印度洋混合层深度季节变化研究 总被引：2，自引：0，他引：2
根据2004-2005年热带印度洋(30°S以北)的Argo浮标(自持式海洋剖面观测浮标)温度-盐度剖面观测资料,采用位势密度判据(Δσθ=0.03 kg/m3),针对每个Argo浮标的温度-盐度观测剖面确定了海洋混合层的深度,然后采用Krig插值方法构建了3°×3°空间分辨率的月平均网格化混合层深度产品。通过与已有气候平均混合层深度资料的比较表明了该产品的合理性,在此基础上进一步对热带印度洋海盆尺度的混合层深度空间特征和季节变化规律进行了讨论。研究结果表明,Argo浮标资料可用于热带印度洋混合层变化的研究,为进一步研究热带印度洋海-气相互作用提供了基础资料。 相似文献
2.
判定局地海-气相互作用的特征对海-气耦合模式中应用哪种形式的“强迫模拟”具有重要指导作用。本文根据海表热通量异常与海表温度异常及海表温度变率之间的相关关系,对全球大洋季节内尺度上的海-气相互作用特征进行了综合分析。结果表明:(1)南、北半球亚热带地区海-气相互作用的特征主要表现为大气对海洋的强迫,且在夏季(北半球为6—8月,南半球为12—翌年2月)强迫作用的范围最大,冬季强迫作用的范围最小;(2)赤道中、东太平洋及赤道大西洋地区海-气相互作用的特征全年表现为海洋对大气的强迫,印度洋索马里沿岸、阿拉伯海以及孟加拉湾地区仅在6—8月表现出海洋强迫大气的现象,而孟加拉湾则在9—11月表现为大气强迫海洋;(3)45°N(S)以上的高纬度地区海表温度的异常和变率无法用局地热通量的交换来解释,这是因为该区域海表温度的变化主要由平流等海洋内部动力过程决定,因此海-气之间在季节内尺度上的相互作用不明显。在某些海区,季节内尺度上的海-气相互作用关系与季节以上时间尺度的这种关系可能会有明显不同。 相似文献
3.
基于1980~2015年的全球简单海洋资料同化分析系统(SODA)、全球海气通量(OAFlux)和全球降水气候学计划(GPCP)等海洋、大气观测再分析资料,采用线性拟合、经验正交函数(EOF)分解、相关分析和波谱分析等数理统计方法,分析了热带西太平洋海表盐度(SSS)和淡水通量时空变化特征及其关系.结果表明,SSS与淡水通量的气候态及长期线性变化趋势有较好的空间对应关系,两者均有多种时间尺度的EOF模态,其年代际变化模态有较好的正相关关系,并与太平洋年代际振荡(PDO)有密切的滞后相关.分析表明,PDO可能通过影响Walker环流的变化来影响热带西太平洋的淡水通量分布,从而影响SSS的时空格局. 相似文献
4.
热带印度洋上层水温的年循环特征 总被引：1，自引：0，他引：1
通过分析多年气候月平均的Levitus水温资料，结合多年气候月平均海表面风场资料以及观测的热带印度洋上层海流的分布状况，探讨热带印度洋上层水温的时空分布特征，剖析了热带印度洋混合层深度及印度洋暖水的季节变化规律。分析表明：热带印度洋的海表面温度低值区始终位于大洋的南部，而高值区呈现明显的季节变化，冬季位于赤道附近，在夏季则处于大洋的东北部；在热带印度洋的中西部、赤道偏南海域的次表层终年存在一冷心结构；热带印度洋表面风场的季节变化是影响该海域混合层深度季节性变化的主要因素；印度洋暖水在冬、春季范围较大，与西太平洋暖池相连，而在夏、秋季范围较小，并与西太平洋暖池分开。 相似文献
5.
于2014年的5月(春季)和9月(秋季)在台湾海峡及其邻近南海和东海海域,采用水气平衡法进行了2个航次的海表和大气pCO_2连续走航观测,同时获取了海表温度、海表盐度、风速及气压等数据,并采用海-气CO_2分压差减法估算了海-气CO_2通量.结果显示,春、秋2个航次平均海表pCO_2分别为387±16μatm和408±18μatm.温度是影响台湾海峡及其邻近海域海表pCO_2的主控因子,水团混合和其他因素等也对海表pCO_2有一定影响.2014年春、秋季节,对研究区域的海-气CO_2释放通量的估算结果分别为0.11±1.60 mmol/(m2·d)和2.51±1.10 mmol/(m2·d).台湾海峡海表pCO_2既存在显著的季节变化,又存在较大的空间差异. 相似文献
6.
7.
冬季风期(11月—翌年3月)南海显著的气候特点是盛行东北季风并频繁地发生冷涌天气过程。使用2008年10月到2009年4月在西沙群岛永兴岛近海进行的海-气通量观测试验资料,分析了西沙海域冬季风期,尤其是冷涌时段的海-气通量交换和热量收支特征。结果表明:冬季风前期由于海-气温差增大,感热通量比西南季风期稍增加;潜热通量平均值与西南季风期接近;太阳总辐射明显降低,大气长波辐射减小,海洋热量净收入成为负值,使得秋季之后海面温度不断降低。冷涌期间海-气之间的感热通量高于冬季风期平均值,潜热通量大部分(1月份之前)也高于冬季风期平均值;由于潜热通量增大和太阳短波辐射减小,1月份之前的冷涌过程海洋热量净收支普遍出现较大负值,海洋失热量强于冬季风期,甚至强于2008年台风过程平均值。到了冬季后期太阳总辐射增强,海洋热量净收入转为正值,海水温度又逐渐升高。季节之间比较,观测区感热通量以冬季风期间最大,秋季次之,春季最小;而潜热通量夏季风期出现最大值,冬季次之,秋季最小。 相似文献
8.
利用1870～2004年的HadiSST的月平均海表面温度(SST)资料,对去除了全球增暖趋势的印度洋-太平洋海表温度异常(SSTA)作季节经验正交函数(Season-reliant Empirical Orthogonal Function, S-EOF)分解,得到了印度洋-太平洋海表温度年际变化的2个联合模态,并且分析了与之相对应的大气环流特征.结果表明:低频的厄尔尼诺/南方涛动(ENSO)是控制印度洋-太平洋的主导模态,能使赤道印度洋维持一异常反气旋性环流,削弱印度洋夏季风的作用并且将东印度洋暖池的暖水输送到西印度洋,印度洋SSTA在一年四季中都出现全海盆同号变化,因此,第一主模态是ENSO的低频模与印度洋海盆一致模的联合模态;第二模态表现为太平洋上准2 a的ENSO位相转换模与印度洋偶极子模的联合模态,ENSO的位相转换发生于春季,与季风的异常转换有关,印度洋上出现异常的气旋性环流,叠加在印度洋夏季风上,增大东西印度洋的温差,在秋季出现西低东高的偶极子型海温分布,印度洋夏季风和这个模态的产生发展有很大的联系. 相似文献
9.
一个区域海-气耦合模式的建立:模式验证及其对热带气旋“云娜”的模拟 总被引：3，自引：1，他引：2
本文以区域热带气旋模式(GRAPES-TCM)为基础,引入海洋环流模式(Estuarine,Coastal and Ocean Model(semi-implicit),ECOM-si)和Ocean Atmosphere Sea Ice Soil 3(OASIS3)耦合器,建立了一个区域海-气耦合模式。利用该模式对0414号热带气旋"云娜"进行了数值模拟,验证了模式的性能。结果表明,耦合模式模拟的"云娜"强度相比单独的大气模式更接近观测,单独大气模式模拟的近地面风场偏强,而耦合模式模拟的近地面风场的强度和非对称结构均与观测更为接近。数值实验中,"云娜"热带气旋过境引起的海表面温度的下降与实况接近,海表面温度下降引起的海-气热通量相比控制实验的结果明显下降,分析资料表明这一下降是合理的。海洋模式的引入导致了热带气旋"云娜"结构的变化,这种变化不但反应在径向风的减弱(强度下降),还反应在对流强度和最强对流发生位置的变化,并最终引起了热带气旋降水结构的改变。 相似文献
10.
海表二氧化碳分压(pCO2)是指海洋表层水和大气之间的二氧化碳(CO2)交换处于动态平衡时CO2的含量, 是描述海-气CO2交换的一个主要因子。本文利用2008—2014年覆盖南海大部分海域的海表pCO2观测资料, 结合现场海表温度和海表盐度以及卫星观测的叶绿素a数据, 构建了基于多元线性回归方法的分区域反演模型。模型在水深浅于30m的区域均方根误差为5.3μatm, 其余海区均方根误差为10.8μatm, 与前人基于个别航次的有限区域反演结果的均方根误差相当。利用该模型公式和HYbrid Coordinate Ocean Model(HYCOM)再分析海表温、盐数据及MODIS-Aqua卫星观测的叶绿素a数据进行反演, 得到了时空分辨率为5'×5'的2004—2016年的逐月南海海表pCO2数据。该数据能较好地反映南海海表pCO2在海表温度影响下, 春夏高、秋冬低的季节变化特征, 与前人基于航次观测的研究结果相似, 表明反演模型具有较高的可信度。进一步分析发现, 南海及邻近海域平均海表pCO2具有显著的准十年振荡特征: 2012年附近出现了极小值, 之前表现为降低的趋势, 之后略有升高的趋势。受海表pCO2的影响, 南海海盆平均海-气CO2通量在2012年之前出现了显著降低的趋势, 表明南海释放到大气中的CO2减少, 并在2007年之后的冬季出现了负值(从碳源变为碳汇), 2012年之后变化较为平缓。热带太平洋年代际振荡引起的南海区域海表盐度变化是造成海表pCO2及海-气CO2通量准十年变化的主要原因。分区分析的结果表明, 南海北部海表pCO2变化最为显著, 在南海海表pCO2的季节和准十年变化中都起到非常重要的作用。 相似文献
11.
Robert L. Molinari 《Progress in Oceanography》2004,62(1):33-66
Upper ocean (above 750 m) temperature structure of the northwestern subtropical Atlantic, including the Gulf Stream and a recirculation gyre south of the Stream, is characterized using primarily bathythermograph (BT) data collected between 1950 and 2003. Geostrophic calculations, using mean temperature-salinity relationships to compute dynamic height, are used to estimate velocities and transports. The mean annual Gulf Stream transport at 72° W relative to 750 m, 36.1 Sv, is approximately equal to the sum of the transport of the Florida Current, 32.0 Sv, and a shallow recirculation gyre described by Wang and Koblinsky [Journal of Physical Oceanography 26 (1996) 2462-2479], 5.5 Sv. The annual cycle of geostrophic transport relative to 750 m at 72° W is in phase with both an earlier published annual cycle of transport relative to 2000 m derived from hydrographic observations and the annual cycle of Florida Current transport measured indirectly by a submarine cable (i.e., maximum transports are observed in the summer and minimum in the fall, early winter). However, simple Sverdrup dynamics are inadequate to explain these cycles as maximum Sverdrup transports extend from winter to summer, while observed transports are minimum (maximum) in fall/winter (summer). The annual cycles derived from the BT data of the size of the shallow southern recirculation gyre, Gulf Stream position and upper layer transport (relative to 300 m) are in phase (maximum size, northern position and transport in fall) and consistent with the WK results derived from altimetry. However, the shallower annual cycles are out of phase with the deeper signals (i.e., maximum for the former (latter) are observed in fall (summer)). Decadal signals after 1965 in Gulf Stream position, geostrophic transport relative to 450 m, and the size of a recirculation gyre south of the Stream are approximately in phase as observed for the annual signal. This gyre and the shallow WK gyre exhibit the same horizontal structure, however, the decadal signal propagates deeper into the water column (at least to 700 m). The eastern expansion and contraction of the gyre on decadal time-scales is correlated with propagating SST signals. The sampling implications of these findings are addressed. 相似文献
12.
A new maximum angle method has been developed to determine surface mixed-layer (a general name for isothermal/constant-density
layer) depth from profile data. It has three steps: (1) fitting the profile data with a first vector (pointing downward) from
an upper level to a depth and a second vector (pointing downward) from that depth to a deeper level; (2) identifying the angle
(varying with depth) between the two vectors; (3) after fitting and calculating angle all depths, and then selecting the depth
with maximum angle as the mixed layer depth (MLD). Temperature and potential density profiles collected from two seagliders
in the Gulf Stream near the Florida coast during 14 November–5 December 2007 were used to demonstrate the method’s capability.
The quality index (1.0 for perfect identification of the MLD) of the maximum angle method is about 0.96. The isothermal layer
depth is generally larger than the constant-density layer depth, i.e., the barrier layer occurs during the study period. Comparison
with the existing difference, gradient, and curvature criteria shows the advantage of using the maximum angle method. Uncertainty
in determining MLD because of varying threshold using the difference method is also presented. 相似文献
13.
14.
Pressure-induced forces and shear stresses on rubble mound breakwater armour layers in regular waves
This paper presents the results from an experimental investigation of the pressure-induced forces in the core material below the main armour layer and shear stresses on the armour layer for a porous breakwater structure. Two parallel experiments were performed which both involved pore pressure measurements in the core material: (1) core material with an idealized armour layer made out of spherical objects that also allowed for detailed velocity measurements between and above the armour, and (2) core material with real rock armour stones. The same core material was applied through the entire structure i.e. no additional filter layers were applied. For both experiments, high-speed video recordings were synchronised with the pressure measurements for a detailed investigation of the coupling between the run-up and run-down flow processes and the measured pressure variations. Outward directed pressure gradients were found which exerted a lift force up to ≈ 60% of the submerged weight of the core material. These maximum outward directed pressure gradients were linked to the maximum run-down event and were in general situated at, or slightly below, the maximum run-down level. Detailed velocity and turbulence measurements showed that the large outward directed pressure gradients in general coincide, both in time and space, with the maximum bed-shear stresses on the armour layer based on the Reynolds-stresses. The bed-shear stresses were found to result in a Shields parameter in the same order of magnitude as the critical value for movement of the armour stones. 相似文献
15.
Wave parameters and functions in wavelet analysis 总被引：2，自引：0，他引：2
A preliminary study of wave parameters and functions in wavelet analysis is conducted in this paper. The Morlet wavelet transform is used to calculate the time–frequency wavelet energy density function, its volume (i.e. the total energy), its frequency-integral (i.e. the wavelet smoothed instantaneous wave energy history), its time-integral (i.e. the wavelet spectral density function), and two non-dimensional wave indices (NIF, NIT). The processing of the measured wave data obtained from the Chi-Gu coastal observation tower during the period August 2000 to July 2001 indicates that the inter-comparison of wavelet smoothed instantaneous wave energy history and smoothed instantaneous wave energy history (SIWEH) as defined by Funke and Mansard (Proc 17th Int Conf on Ocean Eng, 1980) can reveal the noise structure of the wave signal. The wave data with index NIF greater than 2 is always accompanied with noise, therefore NIF can be used as one of the data quality criteria. The index NIT is linearly correlated with the significant wave period and with the significant wave height, therefore NIT can be used to study the wave growth and decaying phenomena. 相似文献
16.
利用桑沟湾海带播苗前和成熟期的海流剖面资料,对最显著的M2分潮流椭圆四要素(最大流速、椭圆率、最大流速方向和最大流速出现时间)的垂直分布特征进行对比分析,结果表明筏式海带养殖对潮流垂直结构有显著影响,由海带播苗前的单一海底边界层,变为海带成熟期的海表和海底双重边界层。海带播苗前,M2分潮流椭圆要素在垂向上变化不大;而在海带成熟期,从中层向海面和海底,最大流速迅速减小、椭圆率逐渐增大、最大流速方向左偏、最大流速出现时间提前。湾口中部的最大流速方向从海带播苗前的南北方向转为海带成熟期的西北—东南方向,这是由水位梯度的变化造成的。 相似文献
17.
Automatic tracing of the foot of the continental slope 总被引：1，自引：0，他引：1
The UNCLOS III (Article 76, Section 4(b)) defines the foot of the continental slope as the point of maximum change in the gradient at its base. It is impossible to locate so defined afoot and thus to trace the foot‐line objectively by eye. In this study we show a method designed automatically to detect and trace the foot‐line of the continental slope from an irregular array of bathymetrical data. Our algorithm first transforms the bathymetric surface to a maximum curvature surface. On this new surface, the foot‐line corresponds to one of the ridges; instead of tracing the foot‐line on the bathymetric surface, we now can trace the ridges on the maximum curvature surface. The tracing of the ridges can be done automatically and objectively and the foot‐line is identified as being one of these ridges. We devote particular attention to the case when the ridge‐line is not defined, i.e., to the case when the point of maximum gradient change becomes a region of maximum gradient change. 相似文献
18.
阿拉伯海淡水输运量的季节变化特征研究 总被引：1，自引：1，他引：0
本文利用简单海洋模式同化再分析产品等资料，阐述了阿拉伯海与赤道西印度洋，阿拉伯海与阿曼湾之间淡水输运量的季节变化特征，揭示了阿拉伯海淡水输运量的基本平衡和季节变化特征。结果表明，阿拉伯海得到的淡水输运量(包括来自赤道西印度洋、河流)和失去的淡水输运量(包括降水量减蒸发量、向阿曼湾输运)基本相当。阿拉伯海通过海气交换失去的淡水(降水量减蒸发量)主要由来自赤道西印度洋(包括孟加拉湾)的淡水输运来补偿，赤道西印度洋向阿拉伯海的淡水输运对维持阿拉伯海的盐度基本平衡起到至关重要的作用。阿拉伯海的淡水输运量在1?6月和12月为负值，失去淡水；7?11月为正值，9月最大，得到淡水。阿拉伯海的净淡水输运量的季节变化特征表现为单峰现象。阿拉伯海与赤道西印度洋(9°N断面）的淡水输运量主要出现在表层至约200 m层，多年平均约为0.1×106 m3/s，向阿拉伯海输运。从10月至翌年3月，来自孟加拉湾的低盐水向阿拉伯海输运，该输运主要出现在印度半岛西南端近海约60 m层以浅区域。夏季和秋季，出现在索马里半岛东部海域的涡旋(大回旋)引起的输运(涡旋的西部低盐水向北输运，东部高盐水向南输运)，不仅输运量是一年当中最大的，而且影响的深度可达约300 m。该输运从6月开始形成，8?9月最强，11月迅速减弱。阿拉伯海与阿曼湾的淡水输运量较小，其垂直分布呈现3层结构，表层至10 m层，高盐水向阿拉伯海输运；15～170 m层，低盐水向阿曼湾输运；175～400 m层，高盐水向阿拉伯海输运。阿曼湾湾口断面多年平均淡水输运量约为0.39×104 m3/s，向阿曼湾输运。 相似文献
19.
Mamun?Abdullah Al Rahman?Muhammed?Forruq Aysha?Akhtar Md.?Wahidul?Alam Mohammad?Nurul?Azim?Sikder Alan?Warren Henglong?Xu
To investigate the seasonal heterogeneity of the periphytic ciliate communities, a 1-year baseline survey was conducted in the Karnaphuli River estuary, northern Bay of Bengal, Bangladesh. A total of 54 ciliate species were recorded, including seven common and 14 dominant species. Maximum species number was in autumn whereas maximum abundance was in winter; the minimum for both occurred in summer. Multivariate analyses, i.e., canonical analysis of principal coordinates (CAP) and principal co-ordinates analysis (PCoA), revealed a clear seasonal heterogeneity of community structure and environmental variables. Multivariate correlation analysis (RELATE) demonstrated that the community structure of the periphytic ciliate communities was significantly correlated with environmental variables, and best matching analysis (BIOENV) indicated that heterogeneity of community patterns was mainly driven by water temperature, pH, dissolved oxygen, total dissolved solids and nutrients. Species richness and diversity peaked in autumn whereas species evenness peaked in summer. These results suggest that environmental conditions shape periphytic ciliate community structure, which is a potentially useful bio-indicator of estuarine water quality. 相似文献
20.
《Marine Geology》2004,203(1-2):185-197
Spatially and temporally extensive nearshore bathymetric datasets have recently been analyzed with complex principal component analysis (CPCA) to extract propagating spatial patterns that constitute most to the dominant lower-dimensional structure in the datasets. CPCA assumes this structure to be linear, which may be an oversimplification of the true structure as the nearshore is a strongly non-linear system. Here we investigate whether a neural network-based circular non-linear principal component analysis (NLPCA.cir) provides a more representative approximation of the underlying lower-dimensional structure of nearshore depth data than possible with CPCA. To that end, NLPCA.cir was applied to three datasets characterized by interannual offshore-directed sandbar behavior, coming from Egmond (The Netherlands), Hasaki Coast (Japan) and Duck (North Carolina, USA). The main difference between these datasets is the temporal variation in sandbar amplitude, which is smallest at Egmond and largest at Duck. We find that the first NLPCA.cir mode 1 at Egmond and Hasaki leads to a more complete characterization of the lower-dimensional data structure than possible with CPCA (i.e. the underlying low-dimensional structure of bathymetric data at Egmond and Hasaki is indeed non-linear). This is not the case at Duck, where the temporal variations in sandbar amplitude are so large that the non-linear lower-dimensional structure in the data, should it exist, is no longer visually apparent and can no longer be detected by NLPCA.cir. This suggests that a simple visual check of the data suffices to decide whether one should resort to NLPCA.cir or to the more simple and computationally quicker CPCA. 相似文献