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1.
Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current(SCSWC) in the northern South China Sea(NSCS) during winter monsoon relaxation. The model reproduces the mean surface circulation of the NSCS during winter, while model-simulated subtidal currents generally capture its current pattern. The model shows that the current over the continental shelf is generally southwestward, under a strong winter monsoon condition, but a northeastward counter-wind current usually develops between 50-and 100-m isobaths, when the monsoon relaxes. Model experiments, focusing on the wind relaxation process, show that sea level is elevated in the northwestern South China Sea(SCS), related to the persistent northeasterly monsoon. Following wind relaxation, a high sea level band builds up along the mid-shelf, and a northeastward current develops, having an obvious vertical barotropic structure. Momentum balance analysis indicates that an along-shelf pressure gradient provides the initial driving force for the SCSWC during the first few days following wind relaxation. The SCSWC subsequently reaches a steady quasi-geostrophic balance in the cross-shelf direction, mainly linked to sea level adjustment over the shelf. Lagrangian particle tracking experiments show that both the southwestward coastal current and slope current contribute to the northeastward movement of the SCSWC during winter monsoon relaxation.  相似文献   

2.
The nonwind-driven mechanism of the winter circulation in the northern South China Sea is discussed. Linked by the Bashi Strait to the Pacific Ocean, the northern South Cnina Sea is treated as a part of the Pacific western boundary where the circulation variation (except the very thin surface layer) is closely related to that of the ocean interior and the effect of local wind might be neglected (at least for some seasons). Based on the assumption that the thick and strong westward current which flows in through the Bashi Strait can effectively prevent water exchange between the northern and southern South China Seas, the model sea only includes the northern part. Barotropic numerical experiments show that part of this westward current is deflected by the continental slope and forms the slope area NE current—the South China Sea Warm Current. Besides, the topographical flow fed by the extension of the western boundary current and the anticyclonic eddy born near the eastern boundary are also fundamental components of the South China Sea Warm Current. The reflection of the incident Rossby waves by the continental slope is found to be of significance in the intensification of the South China Sea Warm Current. Contribution No. 1362 from Institute of Oceanology, Academia  相似文献   

3.
Wind and waves are key components of the climate system as they drive air-sea interactions and influence weather systems and atmospheric circulation. In marine environments, understanding surface wind and wave fields and their evolution over time is important for conducting safe and efficient human activities, such as navigation and engineering. This study considers long-term trends in the sea surface wind speed(WS) and significant wave height(SWH) in the China Seas over the period 1988–2011 using the Cross-Calibrated Multi-Platform(CCMP) ocean surface wind product and a 24-year hindcast wave dataset obtained from the WAVEWATCH-III(WW3) wave model forced with CCMP winds. The long-term trends in WS and SWH in the China Seas are analyzed over the past 24 years to provide a reference point from which to assess future climate change and offshore wind and wave energy resource development in the region. Results demonstrate that over the period 1988–2011 in the China Seas: 1) WS and SWH showed a significant increasing trend of 3.38 cm s~(-1)yr~(-1) and 1.52 cm yr~(-1), respectively; 2) there were notable regional differences in the long-term trends of WS and SWH; 3) areas with strong increasing trends were located mainly in the middle of the Tsushima Strait, the northern and southern areas of the Taiwan Strait, and in nearshore regions of the northern South China Sea; and 4) the long-term trend in WS was closely associated with El Ni?o and a significant increase in the occurrence of gale force winds in the region.  相似文献   

4.
The statistical characterization of sea conditions in the South China Sea(SCS) was investigated by analyzing a 30-year(1976–2005) numerically simulated daily wave height and wind speed data. The monthly variation of these parameters shows that wave height and wind speed have minimum values of 0.54 m and 4.15 ms~(-1), respectively in May and peak values of 2.04 m and 8.12 ms~(-1), respectively in December. Statistical analysis of the daily wave height and wind speed and the subsequent characterization of the annual, seasonal and monthly mean sea state based on these parameters were also done. Results showed that, in general, the slight sea state prevails in the SCS and has nearly the highest occurrence in all seasons and months. The moderate sea condition prevails in the winter months of December and January while the smooth(wavelets) sea state prevails in May. Furthermore, spatial variation of sea states showed that calm and smooth sea conditions have high occurrences(25%–80%) in the southern SCS. The slight sea condition shows the largest occurrence(25%–55%) over most parts of the SCS. High occurrences(8%–17%) of the rough and very rough seas distribute over some regions in the central SCS. Sea states from high to phenomenal conditions show rare occurrence(12%) in the northern SCS. The calm(glassy) sea condition shows no occurrence in the SCS.  相似文献   

5.
Tropical disturbances over the South China Sea (SCS) during the period of 1997-2006 are analyzed using the Tropical Storm and Hurricane WX products. A total of 158 tropical disturbances were formed over the SCS from 1997 to 2006, with 54 developing tropical disturbances which developed into tropical depressions and 104 non-developing tropical disturbances which never developed into tropical depressions. The development rate of tropical disturbances into tropical depressions was 34.18% in these ten years. During the period of this study, total annual numbers of tropical disturbances and developing tropical disturbances over the SCS had significant decreasing trends; however, the development rate of tropical disturbances had an insignificant increasing trend.  相似文献   

6.
Tropical disturbances over the South China Sea (SCS) during the period of 1997-2006 are analyzed using the Tropical Storm and Hurricane WX products. A total of 158 tropical disturbances were formed over the SCS from 1997 to 2006, with 54 de-veloping tropical disturbances which developed into tropical depressions and 104 non-developing tropical disturbances which never developed into tropical depressions. The development rate of tropical disturbances into tropical depressions was 34.18% in these ten years. During the period of this study, total annual numbers of tropical disturbances and developing tropical disturbances over the SCS had significant decreasing trends; however, the development rate of tropical disturbances had an insignificant increasing trend.  相似文献   

7.
Using interpolation and averaging methods, we analyzed the sea surface wind data obtained from December 1992 to November 2008 by the scatterometers ERS-1, ERS-2, and QuikSCAT in the area of 2°N–39 °N, 105°E–130°E, and we reported the monthly mean distributions of the sea surface wind field. A vector empirical orthogonal function (VEOF) method was employed to study the data and three temporal and spatial patterns were obtained. The first interannual VEOF accounts for 26% of the interannual variance and displays the interannual variability of the East Asian monsoon. The second interannual VEOF accounts for 21% of the variance and reflects the response of China sea winds to El Niño events. The temporal mode of VEOF-2 is in good agreement with the curve of the Niño 3.4 index with a four-month lag. The spatial mode of VEOF-2 indicates that four months after an El Niño event, the southwesterly anomalous winds over the northern South China Sea, the East China Sea, the Yellow Sea, and the Bohai Sea can weaken the prevailing winds in winter, and can strengthen the prevailing winds in summer. The third interannual VEOF accounts for 10% of the variance and also reflects the influence of the ENSO events to China Sea winds. The temporal mode of VEOF-3 is similar to the curve of the Southern Oscillation Index. The spatial mode of VEOF-3 shows that the northeasterly anomalous winds over the South China Sea and the southern part of the East China Sea can weaken the prevailing winds, and southwesterly anomalous winds over the northern part of the East China Sea, the Yellow Sea, and the Bohai Sea can strengthen the prevailing winds when El Niño occurs in winter. If El Niño happens in summer, the reverse is true.  相似文献   

8.
In this study, the statistical characterization of sea conditions in the East China Sea(ECS) is investigated by analyzing a significant wave height and wind speed data at a 6-hour interval for 30 years(1980–2009), which was simulated and computed using the WAVEWATCH Ⅲ(WW3) model. The monthly variations of these parameters showed that the significant wave height and wind speed have minimum values of 0.73 m and 5.15 ms~(-1) and 1.73 m and 8.24 ms~(-1) in the month of May and December, respectively. The annual, seasonal, and monthly mean sea state characterizations showed that the slight sea generally prevailed in the ECS and had nearly the highest occurrence in all seasons and months. Additionally, the moderate sea prevailed in the winter months of December and January, while the smooth(wavelets) sea prevailed in May. Furthermore, the spatial variation of sea states showed that the calm and smooth sea had the largest occurrences in the northern ECS. The slight sea occurred mostly(above 30%) in parts of the ECS and the surrounding locations, while higher occurrences of the rough and very rough seas were distributed in waters between the southwest ECS and the northeast South China Sea(SCS). The occurrences of the phenomenal sea conditions are insignificant and are distributed in the northwest Pacific and its upper region, which includes the Southern Kyushu-Palau Ridge and Ryukyu Trench.  相似文献   

9.
用交叉点数据计算中国近海海平面变化   总被引：2，自引：0，他引：2  
讨论了由测高卫星升、降弧段海面高在交叉点上的约束监测海平面变化的方法；用TOPEX／POSIDON测高数据计算了中国黄海、东海、南海海域的海平面变化，其中黄海、东海海域受两个月周期分量的振荡信号影响，而南海海域以年周期变化为主要表现特征；分析了3个海区海平面变化的相关性，扣除两个月的周期分量振荡信号后，其海平面变化的相关性达到90％以上；分析了海水面积随纬度带的变化对不同纬度分布的海区海平面变化量的影响。  相似文献   

10.
The interdecadal factors affecting the summer monsoon winds over Somalia and the South China Sea were studied. Global geopotential heights and wind velocity fields of the 850-hPa and 200-hPa pressure levels, as well as sea surface temperature anomaly data and correlation coefficients were analyzed. The monsoons over Somalia and the South China Sea were found to be two different monsoon systems, operating on different mechanisms and being affected by different ocean-atmosphere interactions. The intensity of the Asian subtropical summer monsoon is influenced by the intensity of the summer monsoon over Somalia in the month of June and by the intensity of the summer monsoon over the South China Sea in the months of June and July. The summer monsoon wind strength over Somalia is affected by regional factors, such as the heating of the Tibetan plateau, and by global mechanisms, such as the subtropical heat exchange with Antarctica. The summer monsoon over the South China Sea is affected by different ocean-atmosphere interactions. The Somalia and subtropical summer monsoons have wind blowing down the pressure gradient from area over ocean to that over land, like typical summer monsoons. The South China Sea summer monsoon has winds that blow down the pressure gradient from area over land to that over ocean. The South China Sea summer monsoon is affected by the Kuroshio Current off the east coast of Japan.  相似文献   

11.
A novel method is proposed to obtain the power spectra of hidden variables in a chaotic time series. By embedding the data in phase space , and recording the conditional probability densityof points that the trajectory encounters as it evolves in the reconstructed phase space, it is possible torecover the power spectra of hidden variables in chaotic time series through a spectral analysis over theconditional probability density time series. The method is robust in the application to Lorenz system, 4-di-mension Rossler system and rigid body motion by linear feedback system (LFRBM). Applying the method the time series of sea surface temperature (SST) of the South China Sea, we obtained the power spectraof the wind speed (WS) from SST data. Furthermore, the results showged that there exists an importantnonlinear interaction between the SST and the WS.  相似文献   

12.
We analyzed interdecadal variability of the South China Sea monsoon and its relationship with latent heat flux in the Pacific Ocean, using NCEP wind field and OAFlux heat flux datasets. Results indicate that South China Sea monsoon intensity had an obvious interdecadal variation with a decreasing trend. Variability of the monsoon was significantly correlated with latent heat flux in the Kuroshio area and tropical Pacific Ocean. Variability of latent heat flux in the Kuroshio area had an interdecadal increasing trend, while that in the tropical Pacific Ocean had an interdecadal decreasing trend. Latent heat flux variability in these two sea areas was used to establish a latent heat flux index, which had positive correlation with variability of the South China Sea monsoon. When the latent heat flux was 18 months ahead of the South China Sea monsoon, the correlation coefficient maximized at 0.58 (N=612), with a 99.9% significance level of 0.15. Thus, it is suggested that latent heat flux variability in the two areas contributes greatly to interdecadal variability of the South China Sea monsoon.  相似文献   

13.
The chlorophyll a(Chl a) is an important indicator of marine ecosystems. The spatiotemporal variation of the Chl a greatly aff ects the mariculture and marine ranching in coastal waters of the Shandong Peninsula. In the current study, the climatology and seasonal variability of surface Chl-a concentration around the Shandong Peninsula are investigated based on 16 years(December 2002–November 2018) of satellite observations. The results indicate that the annual mean Chl-a concentration is greater in the Bohai Sea than in the Yellow Sea and decreases from coastal waters to off shore waters. The highest Chl-a concentrations are found in Laizhou Bay(4.2–8.0 mg/m 3), Haizhou Bay(4.2–5.9 mg/m 3) and the northeast coast of the Shandong Peninsula(4.4–5.0 mg/m 3), resulting from the combined eff ects of the intense riverine input and long residence time caused by the concave shape of the coastline. The seasonal Chl-a concentration shows a signifi cant spatial variation. The Chl-a concentrations in these three subregions generally exhibit an annual maximum in August/September, due to the combined eff ects of sea surface temperature, river discharge and sea surface wind. In the southeast coast region, however, the Chl-a concentration is lowest throughout the year and reaches a maximum in February with a minimum in July, forced by the seasonal evolution of the Yellow Sea Cold Water and monsoon winds. The interannual Chl-a concentration trends vary among regions and seasons. There are signifi cant increasing trends over a large area around Haizhou Bay from winter to summer, which are mainly caused by the rising sea surface temperature and eutrophication. In other coastal areas, the Chl-a concentration shows decreasing trends, which are clearest in summer and induced by the weakening land rainfall. This study highlights the diff erences in the Chl-a dynamics among regions around the Shandong Peninsula and is helpful for further studies of coupled physical-ecological-human interactions at multiple scales.  相似文献   

14.
This paper examines the capability of three regional climate models(RCMs),i.e.,RegCM3(the International Centre for Theoretical Physics Regional Climate Model),PRECIS(Providing Regional Climates for Impacts Studies)and CMM5(the fifth-generation Pennsylvania State University-the National Center for Atmospheric Research of USA,NCAR Mesoscale Model)to simulate the near-surface-layer winds(10 m above surface)all over China in the late 20th century.Results suggest that like global climate models(GCMs),these RCMs have the certain capability of imitating the distribution of mean wind speed and fail to simulate the greatly weakening wind trends for the past 50 years in the country.However,RCMs especially RegCM3 have the better capability than that of GCMs to simulate the distribution and change feature of mean wind speed.In view of their merits,these RCMs were used to project the variability of near-surface-layer winds over China for the 21st century.The results show that 1)summer mean wind speed for 2020-2029 will be lower compared to those in 1990-1999 in most area of China; 2)annual and winter mean wind speed for 2081-2100 will be lower than those of 1971-1990 in the whole China; and 3)the changes of summer mean wind speed for 2081-2100 are uncertain.As a result,although climate models are absolutely necessary for projecting climate change to come,there are great uncertainties in projections,especially for wind speed,and these issues need to be further explored.  相似文献   

15.
In a study of surface monsoon winds over the China marginal seas, Sun et al. (2012) use singular value decomposition method to identify regional dominant modes and analyze their interdecadal variability. This paper continues to evaluate the interannual variability of each dominant mode and its relation to various atmospheric, oceanic and land factors. The findings include: 1) The intensity of the winter monsoon over the East China Sea is highly correlated with the Siberian High intensity and anti-correlated with the latitudinal position of the Aleutian Low as well as the rainfall in eastern China, Korean Peninsula and Japan; 2) The western Pacific subtropical high is significantly correlated with the summer monsoon intensity over the East China Sea and anti-correlated with the summer monsoon over the South China Sea; 3) The winter monsoon in a broad zonal belt through the Luzon Strait is dominated by the ENSO signal, strengthening in the La Ni a phase and weakening in the El Ni o phase. This inverse relation exhibits interdecadal shift with a period of weak correlation in the 1980s; 4) Analysis of tidal records validates the interdecadal weakening of the East Asian summer monsoon and reveals an atmospheric bridge that conveys the ENSO signal into the South China Sea via the winter monsoon.  相似文献   

16.
海面风场是海洋学的基本参量,获取海面风场对了解海洋的物理过程以及海洋与大气之间的相互作用至关重要。宽阔的海域面积及复杂的海面状况通常使南海海面上的风场信息很难被及时获取。ENVISAT ASAR是一种全天候全天时监测海面的微波雷达传感器,可实时获取海面风场数据。本文基于已有ASAR数据对南海海面风场进行反演实验,首先将结合高斯曲线拟合的FFT风向反演方法应用于南海风向反演,并参考Cross-Calibrated Multi-Platform （CCMP）风场数据去除180o方向模糊获得海面风向。然后,将高斯曲线拟合-FFT风向与传统的峰值-FFT风向进行对比,最后将准确率较高的高斯曲线拟合-FFT风向分别输入CMOD4模型和CMOD5模型获得海面风速大小。实验结果与CCMP参考数据的比较结果表明,在风条纹不明显的情况下,利用结合高斯曲线的FFT风向反演方法和CMOD4模型风速反演方法可有效地进行南海海面风场反演。该成果对利用SAR数据实时获取南海大面积海面风场信息,尤其是观测点缺乏海域的风场信息,具有重要的指导意义。  相似文献   

17.
There are numerous studies on polar amplification and its influence on mid-latitude weather and climate. However, assessments on whether polar amplification occurs in Antarctica are rarely conducted. Based on the latest atmospheric reanalysis of ERA5 produced by European Centre for Medium-Range Weather Forecasts(ECMWF), we have defined the Antarctic amplification index, and calculated the trend of annual and seasonal Surface Air Temperature(SAT) mean during 1979-2019 for Antarctic Ice Sheet(AIS) and the trend mean of different meridional sectors of Antarctic sub regions including East Antarctic Ice Sheet(EAIS), West Antarctic Ice Sheet(WAIS) and Antarctic Peninsula(AP). Antarctic amplification shows regional differences and seasonal variations. Antarctica shows a slight warming with the largest magnitude in AP. The temperature anomalies indicate the least fluctuations in austral summer, and the more fluctuations in winter and spring. In austral summer, the warming trend domains EAIS and WAIS, while the cooling trend appears over AP. The zonal mean in Southern Hemisphere maintains a warming trend in the low latitudes, and fluctuates greatly in the middle and high latitudes. The strongest Antarctic amplification phenomenon occurs in spring, with the amplification index of 1.20. For AP, the amplification occurs in austral autumn, and the amplification index is 2.16. At South Pole and the surrounding regions, SAT for land only fluctuates largely and shows different trends in different seasons. The mechanism of Antarctic amplification is unclear till now, and its research suffers from the limitation of measured data. This suggests that future research needs progress in comprehensive ground observation network, remote sensing data accumulation, and high-resolution climate modeling with better representation of both atmospheric and cryospheric processes in Antarctica.  相似文献   

18.
Analysis on long-term change of sea surface temperature in the China Seas   总被引：4，自引：0，他引：4  
Long-term change of sea surface temperature (SST) in the China Seas from 1900 to 2006 is examined based on two different observation datasets (HadISST1 and HadSST3). Similar to the Atlantic, SST in the China Seas has been well observed dur-ing the past 107 years. A comparison between the reconstructed (HadISST1) and un-interpolated (HadSST3) datasets shows that the SST warming trends from both datasets are consistent with each other in most of the China Seas. The warming trends are stronger in winter than in summer, with a maximum rate of SST increase exceeding 2.7℃ (100 year)-1 in the East China Sea and the Taiwan Strait during winter based on HadISST1. However, the SST from both datasets experienced a sudden decrease after 1999 in the China Seas. The estimated trend from HadISST1 is stronger than that from HadSST3 in the East China Sea and the east of Taiwan Island, where the difference in the linear SST warming trends are as large as about 1℃ (100 year)-1 when using respectively HadISST1 and HadSST3 datasets. When compared to the linear winter warming trend of the land surface air temperature (1.6℃ (100 year)-1), HadSST3 shows a more reasonable trend of less than 2.1℃ (100 year)-1 than HadISST1’s trend of larger than 2.7℃ (100 year)-1 at the mouth of the Yangtze River. The results also indicate large uncertainties in the estimate of SST warming patterns.  相似文献   

19.
Tree-ring chronologies from pine, oak and black locust tree species were used to reconstruct annual streamflow and examine hydrological drought years for Palgong Mountain forested watershed in southeastern South Korea for the period from 1954-2015. The backward elimination multiple regression analysis provided the statistically significant predictor chronologies of streamflow. The final calibration and verification test models accounted for 84.8% and 81.6%, respectively, of the variability in streamflow observed in the gage data. Further verification of the validity of the reconstructed model was undertaken with the Pearson Correlation Coefficient, the Reduction of Error Test, and the Durbin-Watson Statistics and indicated fidelity of the model for reconstructing the annual streamflow. Analyses of the reconstructed annual streamflow indicate that the most persistent years of high flows above the median annual discharge occurred from 1986-2008. This period included 7 single or multiple years of highest flow above the 90th percentile discharge and multiple years of high flows with a time interval of 2-6 years, although with intervening multiple years of low flows below the 10th and 50th percentile. In comparison, the most persistent years of low flows below the median annual discharge occurred from 1954-1985 and 2009-2015. This period included 8 single or multiple years of lowest flow below the 10th percentile discharge and multiple years of low flows with a time interval of 2-9 years, although also with intervening multiple years of high flows above the 50th percentile. No single years of extreme hydrological droughts below the 10th percentile were identified from 1986-2015 whereas a greater proportion of high flows above the 90th percentile occurred during this period. The persistent single or multiple years of lowest flows between 1954 and 1985 were the recent most critical hydrological drought years identified in the Palgong Mountain forested watershed providing supportive evidence of the severity of past hydrological droughts during that period, applicable to the southeastern South Korea where the study watershed is located. This interpretation agrees with the hydrological drought event years identified from 1951 to the early 1980s in a related national study that used precipitation proxy data to reconstruct past occurrences of droughts in Korea.  相似文献   

20.
Using the wave model WAVEWATCH III(WW3), we simulated the generation and propagation of typhoon waves in the South China Sea and adjacent areas during the passage of typhoon Nesat(2011). In the domain 100°–145°E and 0°–35°N, the model was forced by the cross-calibrated multi-platform(CCMP) wind fi elds of September 15 to October 5, 2011. We then validated the simulation results against wave radar data observed from an oil platform and altimeter data from the Jason-2 satellite. The simulated waves were characterized by fi ve points along track using the Spectrum Integration Method(SIM) and the Spectrum Partitioning Method(SPM), by which wind sea and swell components of the 1D and 2D wave spectra are separated. There was reasonable agreement between the model results and observations, although the WW3 wave model may underestimate swell wave height. Signifi cant wave heights are large along the typhoon track and are noticeably greater on the right of the track than on the left. Swells from the east are largely unable to enter the South China Sea because of the obstruction due to the Philippine Islands. During the initial stage and later period of the typhoon, swells at the fi ve points were generated by the propagation of waves that were created by typhoons Haitang and Nalgae. Of the two methods, the 2D SPM method is more accurate than the 1D SIM which overestimates the separation frequency under low winds, but the SIM method is more convenient because it does not require wind speed and wave direction. When the typhoon left the area, the wind sea fractions decreased rapidly. Under similar wind conditions, the points located in the South China Sea are affected less than those points situated in the open sea because of the infl uence of the complex internal topography of the South China Sea. The results reveal the characteristic wind sea and swell features of the South China Sea and adjacent areas in response to typhoon Nesat, and provide a reference for swell forecasting and offshore structural designs.  相似文献   

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