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1.
The daily and monthly-mean characteristics of cold water patches(CWPs) off the Jiangsu coast in 35 a of1982–2016 are examined based on advanced very high resolution radiometer(AVHRR) data. Most of the CWPs are found to occur in the warm and hot months(May–September), with some CWPs in the cool and cold months(October–April). The average radius and intensity of the monthly-mean CWPs are about 81 km and 0.6°C,respectively. The average difference in the sea surface temperature(SST) between the centers of the CWPs and the nearshore is about 2.0°C. The correlation analysis between the CWPs, winds and tides indicates that most of the CWPs occurred during the southerly winds, with some CWPs occurring during the northerly winds. The average intensity of the CWPs during spring tides is slightly stronger than that during neap tides in the warm and hot months, and the difference is very small in the cool and cold months.  相似文献   

2.
The recent decline in the Arctic sea ice has coincided with more cold winters in Eurasia.It has been hypothesized that the Arctic sea ice loss is causing more mid-latitude cold extremes and cold winters,yet there is lack of consensus in modeling studies on the impact of Arctic sea ice loss.Here we conducted modeling experiments with Community Atmosphere Model Version 5(CAM5) to investigate the sensitivity and linearity of Eurasian winter temperature response to the Atlantic sector and Pacific sector of the Arctic sea ice loss.Our experiments indicate that the Arctic sea ice reduction can significantly affect the atmospheric circulation by strengthening the Siberian High,exciting the stationary Rossby wave train,and weakening the polar jet stream,which in turn induce the cooling in Eurasia.The temperature decreases by more than 1°C in response to the ice loss in the Atlantic sector and the cooling is less and more shifts southward in response to the ice loss in the Pacific sector.More interestingly,sea ice loss in the Atlantic and Pacific sectors together barely induces cold temperatures in Eurasia,suggesting the nonlinearity of the atmospheric response to the Arctic sea ice loss.  相似文献   

3.
2007和2012年北极最小海冰范围空间分布不同的原因分析   总被引：1，自引：0，他引：1  
Satellite records show the minimum Arctic sea ice extents(SIEs) were observed in the Septembers of 2007 and2012, but the spatial distributions of sea ice concentration reduction in these two years were quite different.Atmospheric circulation pattern and the upper-ocean state in summer were investigated to explain the difference.By employing the ice-temperature and ice-specific humidity(SH) positive feedbacks in the Arctic Ocean, this paper shows that in 2007 and 2012 the higher surface air temperature(SAT) and sea level pressure(SLP)accompanied by more surface SH and higher sea surface temperature(SST), as a consequence, the strengthened poleward wind was favorable for melting summer Arctic sea ice in different regions in these two years. SAT was the dominant factor influencing the distribution of Arctic sea ice melting. The correlation coefficient is –0.84 between SAT anomalies in summer and the Arctic SIE anomalies in autumn. The increase SAT in different regions in the summers of 2007 and 2012 corresponded to a quicker melting of sea ice in the Arctic. The SLP and related wind were promoting factors connected with SAT. Strengthening poleward winds brought warm moist air to the Arctic and accelerated the melting of sea ice in different regions in the summers of 2007 and 2012. Associated with the rising air temperature, the higher surface SH and SST also played a positive role in reducing summer Arctic sea ice in different regions in these two years, which form two positive feedbacks mechanism.  相似文献   

4.
Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002, the study classifies the airflows in favor of sea fog over the Huanghai (Yellow) Sea in boreal spring (April-May) with the method of trajectory analysis, and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow. According to the heat balance equation, we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths. The major results are summarized as follows. (1) Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog. The proportion of warm fog only accounts for 44% in April, while increases as high as 57% in May. (2) Four primary airflow paths leading to spring sea fog are identified. They are originated from the northwest, east, southeast and southwest of the Huanghai Sea, respectively. The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%, while these along the southwest and northwest airflow paths are merely 17.9% and 50%. (3) The key physical processes governing the warm/cold sea fog are heat advection transport, longwave radiation cooling at fog top, solar shortwave warming and latent heat flux between airsea interfaces. (4) The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection, and the vertical distribution of relative humidity.  相似文献   

5.
A coastal upwelling event in the southern Taiwan Strait (STWS) was investigated using intensive cruise surveys (four repeated transects in a month) and satellite data in July and early August 2004.The extensive upwelling-associated surface cold water was first observed in early July (～2.0×10 4 km 2) along the STWS coast.Then,the cold surface water reduced in size by ～50% with decreased chlorophyll concentrations after 15 days,indicating the weakening of the upwelling event.At the end of July,the cold surface water disappeared.The temporal variations of the surface cold water and the 3-D hydrography around Dongshan Island are thought to be mainly attributed to the weakened upwelling-favorable southwestern wind,the asymmetric spatial structure of the wind field and the intrusion of warm water from the northern South China Sea.  相似文献   

6.
This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.  相似文献   

7.
Three warm currents, the Kuroshio, its shelf intrusion branch in the northeast of Taiwan and the Taiwan Warm Current (hereafter TWC), dominate the circulation pattern in the East China Sea (hereafter ECS). Their origination, routes and variation in winter and summer are studied. Their relationship with four major high and low temperature centers is analyzed. Differing from the previous opinion, we suggest that the four major centers are generated to a great extent by the interaction of the currents in the ECS. In summer, a cold water belt in the northeast of Taiwan is preserved from winter between the Kuroshio and the TWC. The shelf intrusion branch of the Kuroshio separates the water belt, and two low temperature centers generate in the northeast of Taiwan. In the southern ECS, the TWC transports more heat flux northward to form a warm pool. But it is separated in the lower layer by the cold water driven by the intrusion branch of the Kuroshio. So the TWC and the intrusion branch of the Kuroshio play a dominating role to generate the high temperature center. The interaction among the eastward TWC, the northward Tsushima Warm Current (hereafter TSWC) and the southward Su Bei Coastal Flow (hereafter SBCF) generates the low temperature center in the northern ECS. In winter, the strengthening of the shelf intrusion branch of the Kuroshio obscures the two low temperature centers in the northeast of Taiwan. For the weakening of the TWC, the high temperature center in the southern ECS vanishes, and the low temperature center in the northern ECS shifts to south.  相似文献   

8.
An algal bloom is defined as a relatively rapid increase in the biomass of phytoplankton in an aquatic system. During 30 March to 24 April 2007, a cruise was conducted in the central Southern Huanghai Sea to investigate the spring bloom processes. The spatial and temporal variations of phytoplankton are discussed based on the in-situ observations and simultaneous remote sensing data. The explosive algal blooming varied quickly in temporal and spatial scales, due to the highly patchy distribution. Data obtained at the 2 anchor stations (BM1 and BM2) were analyzed in the present study. Horizontal advection is speculated to be responsible for the abrupt decrease in the concentration of chlorophyll-a at stations BM1 and BM2. At station BM2, the intermediate high chlorophyll-a concentration, coinciding with the low temperature, was found to be advected from the inshore colder water mass located to the east of the site.  相似文献   

9.
Bifenthrin(BF) is a pyrethroid insecticide that is widely used in agriculture, horticulture, and for residential purposes. However, few studies addressing the reproductive toxicity of BF on fishes are available. The present study was conducted to investigate the effects of BF on testicular development in Sebastiscus marmoratus and to gain insight into its mechanism. After exposure to 1, 10 and 100 ng/L BF for 50 days, there was a reduced number of mature sperm and an abundance of the late stages of spermatocysts in the testes. The levels of 17β-estradiol and testosterone were decreased significantly after BF exposure. The activity of caspase-3 was increased in a dosedependent manner after BF exposure, TUNEL assay indicated that BF exposure resulted in the occurrence of apoptosis in the testes, which might be main reason for the inhibition of spermatogenesis.  相似文献   

10.
Sea-ice physical characteristics were investigated in the Arctic section of 143°-180°W during August and early September 2008. Ship-based observations show that both the sea-ice thickness and concentration recorded during southward navigation from 30 August to 6 September were remarkably less than those recorded during northward navigation from 3 to 30 August, especially at low latitudes. Accordingly, the marginal ice zone moved from about 74.0°N to about 79.5°N from mid-August to early September. Melt-pond coverage increased with increasing latitude, peaking at 84.4°N, where about 27% of ice was covered by melt ponds. Above this latitude, melt-pond coverage decreased evidently as the ice at high latitudes experienced a relatively short melt season and commenced its growth stage by the end of August. Regional mean ice thickness increased from 0.8 (±0.5) m at 75.0°N to 1.5 (±0.4) m at 85.0°N along the northward navigation while it decreased rapidly to 0.6 (±0.3) m at 78.0°N along the southward navigation. Because of relatively low ice concentration and thin ice in the investigated Arctic sector, both the short-term ice stations and ice camp could only be set up over multiyear sea ice. Observations of ice properties based on ice cores collected at the short-term ice stations and the ice camp show that all investigated floes were essentially isothermal with high temperature and porosity, and low density and salinity. Most ices had salinity below 2 and mean density of 800-860 kg/m~3 . Significant ice loss in the investigated Arctic sector during the last 15 a can be identified by comparison with the previous observations.  相似文献   

11.
利用欧洲中心气候再分析资料和美国国家冰雪数据中心北极海冰面积资料，分析了夏季北极海冰面积与前期大气经向热量输送年际变化的联系。结果表明：6月北半球中高纬大气的经向热量输送以瞬变热量形式为主，其中巴芬湾西部（B区）和格陵兰岛东部（G区）是瞬变热量向极区传输的两个通道，二者之间存在反位相的协同变化，且这种协同变化与夏季北极海冰面积变化密切相关。可能的机制为：6月，AD、AO和NAO三种北极大气环流型能够引起巴芬湾西部和格陵兰岛东部瞬变热量输送的协同变化，这种协同变化通过涡旋动力作用激发夏季极区大气表现为AD异常，同时影响途经区域的气温，从而通过热动力作用影响夏季北极海冰。将向极区输送的热量称为暖输送，从极区输出的热量为冷输送，则上述两个区域的瞬变热量协同输送可分为三种情况：B暖G冷、B冷G暖、B和G均冷，而B和G均暖的情况十分罕见。当B区向极区输入、G区输出热量时，有利于太平洋扇区和喀拉海的海冰偏少；当G区输入、B区输出热量时，利于喀拉海和拉普捷夫海海冰偏少；当B区和G区均输出热量时，利于波佛特海南部、喀拉海和拉普捷夫海海冰偏多，反之则相反。  相似文献   

12.
中国近海海表温度变化的极端特性及其气候特征研究   总被引：4，自引：0，他引：4  
本文基于1982–2017年日再分析数据，分析了中国近海海表温度变化的极端特性、历史演变、空间格局及可能影响，并探讨了与全球变化和区域气候变率的关联性。近30多年来，中国近海海表总体升温明显，尤以春季长江口附近及以南的外部近岸海域升温最为显著，线性升温速率高达0.2°C/(10 a)。相比而言，沿岸海域对气候变暖暂缓的响应可能更为明显；极端高(低)温强度以显著增强(减弱)为主，尤以春(夏)季幅度最大。沿岸海域春季极值温差增强显著，易通过物候变化引起生物迁移和赤潮等生态灾害突发、频发；北部海域极端事件持续天数大于南部，其中，黄海、东海极端高温持续天数增加显著，可能对渔业资源产生较大影响。受气候变暖暂缓影响，极端低温持续天数亦显著增加；极端高温在长江口附近，台湾海峡和南海北部等海域累积频次上升显著，未来极端海洋热浪事件可能持续增加，将对南海珊瑚礁等产生较大影响。极端低温累积频次以显著降低为主。然而长江口及以南沿岸极端低温在冬春季增强明显，可能对红树林等产生一定影响；太平洋年代际振荡(PDO)暖位相期间，ENSO暖事件得到增强，易引起中国近海海表极端低温的频发。北极涛动(AO)正位相时，限制了极区冷空气向南扩展，中国近海海表极端高温频次趋于增加，其危险性增强。  相似文献   

13.
北极秋季海冰减少与亚洲大陆冬季温度异常   总被引：1，自引：1，他引：0  
本文使用SVD等诊断分析方法探讨北极秋季海冰密集度与亚洲冬季温度异常之间的关系。结果表明,近30余年来,北极秋季海冰减少伴随着亚洲大陆冬季温度降低,但青藏高原地区、北冰洋和北太平洋沿岸除外。北极秋季海冰密集度减小激发欧亚大陆和北冰洋北部两个区域位势高度的改变,这种异常的变化模态从秋季持续到冬季。位势高度异常的负值中心位于巴伦支海和喀拉海。位势高度异常的正值中心位于蒙古区域。与重力位势高度异常伴随的风场异常为亚洲冬季温度降低提供自北向南的冷气流。随着北极海冰的不断减少,其与亚洲大陆冬季温度降低之间的关系将为气候长期预测提供参考。  相似文献   

14.
收集了1963—1996年长江口外海域水温的观测数据,分析了该海域冬、春季表层、10m层、20m层和30m层不同层次水温的季节和年际变化规律,以及其间水温垂向结构的变化。季节变化上,表层多年平均水温在8月最高,3月最低,底层多年平均水温9月最高,3月最低。年际变化上,冬季在1979年存在一个由冷到暖的跃迁;4月水温的年际变化较冬季复杂,表层、10m层、20m层和30m层水温分别在1979、1973、1973和1975年发生从冷到暖的跃迁。水平分布上,冬季除东南角小范围表层水温降低外,沿岸及北部海区表层水温均升高,春季北部和南部中间海域水温升高,升温幅度由表层至30m层逐渐变小。垂向结构上,冬季表底混合均匀,表层与20m层的年际变化相关系数高达0.97,春季表层与20m层的水温差存在10年左右的变化周期。本文将一些可能影响春季水温年际变化的因素与海温进行了比较并发现,在冷期,春季表层海温与长江口外海域气温相关较暖期好,相关指数为0.79;而暖期的春季表层与20m层的水温差与净热通量相关系数较高,为0.65。  相似文献   

15.
Remote sensing data sets and a high-resolution three-dimensional regional ocean model were utilized to investigate the shifting of warm/cold regime and the associated sea level variation in the South China Sea (SCS) during 2000–2003. Both the altimetry data and the model results showed an increase in the sea level (warm phase) followed by an abrupt decrease (cold phase) in the SCS during 2000–2003. Heat budget calculations performed with the model revealed excess heat advection from the western Pacific warm pool into the SCS during the warm phase than the cold phase. The warm phase, which occurred during La Niña episodes, resulted from the intrusion of abnormally warmer western Pacific water that increased the heat content and thus sea level in the SCS. The cold phase, which occurred during El Niño episodes, was triggered by a reduction in the net atmospheric heat flux followed by cold water advection into the SCS. Decrease in the rate of precipitation minus evaporation (P?E) also accounted for the falling of sea level during cold phase. The present study integrated the available remote sensing data and advanced numerical model to identify the time-dependent three-dimensional dynamic and thermodynamic forcing that are important in governing the warm/cold regime shift in the SCS.  相似文献   

16.
黄河口邻近海域海冰是渤海海冰的一部分,为了解其独特的变化特征及机制,本研究基于北海预报中心提供的黄河口周边海洋台站观测数据以及CMEMS (Copernicus Marine Environment Monitoring Service)全球海冰密集度再分析数据,使用统计分析和两种滑动相关分析,结合小波相干方法及大气过程的影响,得到长期变化分析的结果。黄河口冰情在1979—2020年间整体呈减轻趋势(–0.25%/a),显然其直接因素为局地温度整体升高;海冰密集度与黄河径流量呈明显正相关,相关系数为0.46,其原因为径流增大导致盐度降低,海冰增加;与北极涛动指数(AOI,Arctic Oscillation Index)呈明显负相关,相关系数为–0.44,因为当北极涛动为正位相时,东亚大槽强度减弱,北极冷空气南侵受阻隔,冬季黄河口的整体气温升高,导致海冰减少;1997年和2016年左右与北极涛动的相关性都出现了显著正异常,其原因为两次强厄尔尼诺事件的影响,同时海冰密集度在1985年左右的跃变可能与AOI和黄河径流量的突变有关。短期变化分析的结果显示:从2010年和2020年冬季逐日的典型寒潮过程与海冰密集度的变化分析可知,海冰与前6 d负积温的相关性最大,平均相关系数为–0.77,寒潮的出现时间、强度及间隔,控制海冰的生成,而整体气温的低频变化控制海冰的维持和发展。  相似文献   

17.
Composites of warm and cold temperature anomalies were constructed, and the distribution of the recurrence frequency of days with temperature anomalies in the four seasons of the year was evaluated based on satellite measurements data on sea surface temperature. Regions of the formation of cold anomalies in the northwestern part of the sea and warm anomalies in the northern and northeastern parts of sea were distinguished, related to advection by the Black Sea Rim Current. The distribution functions of temperature anomalies and the lifetime of the cold and warm anomalies were estimated. A plausible physical mechanism of the generation of cold anomaly in the southeastern marginal part of the sea related to Ekman pumping of cold water from the thermocline was considered.  相似文献   

18.
夏季北冰洋无冰海域次表层暖水结构的形成机理   总被引：1，自引：0，他引：1  
在夏季北冰洋的无冰海域,经常可以观测到次表层暖水现象,即在水深20～50m的范围内发生海水温度的极大值。建立了一个一维的热力学解析模式,用于研究夏季北冰洋次表层暖水的形成机制。模式的计算结果表明,太阳辐射作用是形成次表层暖水的关键因素。在北冰洋的开阔水域,大气吸收海洋热量的过程导致了海面温度下降,使温度极大值出现在次表层。海洋垂向湍流热扩散对次表层暖水温度有显著影响;当湍流热扩散较弱时,热扩散的范围较小,有利于形成次表层暖水。次表层暖水的位置随着时间的推移不断加深,温度不断增高。在北极,大气温度低于海面温度是普遍现象,次表层暖水经常发生。虽然当海面气温发生变化时,次表层海水温度结构会发生相应的变化,但次表层暖水结构形成之后,如果不受强烈天气过程的破坏,则会一直存在下去。按照本文的结论,随着北极气候变暖,海冰将进一步减少,次表层暖水现象还会明显增加,海洋对气候变化将有更加强烈的响应和反馈,对全球气候变化产生意义深远的影响。  相似文献   

19.
北冰洋西伯利亚陆架海是北极气候快速变化最为显著的海域之一,而沉积硅藻作为极地海洋生态系统的重要组成部分,对环境变化具有敏感的响应。对楚科奇海、东西伯利亚海和拉普捷夫海表层沉积物开展了硅藻组成鉴定,利用典型对应分析方法分析了硅藻属种与1986～2015年环境变量之间的关系。结果表明,夏季和秋季海冰密集度、表层海水盐度是影响研究区表层硅藻分布特征最主要的因素。此外,根据表层站位与环境变量的典型对应分析,可将西伯利亚极地海域划分为4个区域,分别为海冰硅藻组合带、暖水硅藻组合带、沿岸硅藻组合带和混合硅藻组合带。这些表层站位的分区与相应区域的海流模式有明显的相关性,海冰硅藻组合带仅分布于研究区北部的高纬度地区;暖水硅藻组合带位于受白令水和太平洋海水的分支——阿拉斯加沿岸水影响为主的区域;拉普捷夫海南部的沿岸硅藻组合带则受到河流径流和西伯利亚沿岸流的强烈影响;混合硅藻组合带受极地冷水、海冰覆盖、太平洋暖水和陆地径流的共同影响。  相似文献   

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