中国东部夏季风雨带季内变化各模态的环流及海温特征   总被引：1，自引：1，他引：0  

宗海锋  陈烈庭 《大气科学》2013,37(5):1072-1082

本文根据中国气象局国家气候中心提供的中国160站月平均降水量,NCEP/NCAR再分析的850 hPa风场,及NOAA扩展重建的海温场资料,用合成分析和相关分析,研究了1951～2005年间中国夏季风雨带季内变化各模态的西太平洋副高夏季各月活动特点的差异,及其与前期冬季东亚季风和太平洋海温异常的联系,并分析了我国夏季风雨带季内变化各模态与夏季雨型的关系。结果表明,不仅不同模态对应的西太平洋副高自春至夏的两次北跳有明显不同的过程,而且两次北跳还具有相对独立性。第一次北跳主要对6月的雨带特征有重要影响,第二次北跳对7、8两月的雨带分布有决定性意义。太平洋海温异常对我国夏季风雨带季内变化的影响是多态的,在不同季风—ENSO循环的位相有不同的表现。第一模态主要出现在El Ni?o减弱位相,第二模态在La Ni?a发展位相,第三模态在El Ni?o发展位相,第四模态在La Ni?a减弱位相,第五模态ENSO的信号较弱,第六模态在La Ni?a持续位相。此外,不同海洋关键区的海温异常对我国雨带季内变化也有不同的调控作用。黑潮区的海温与6月的雨带活动关系密切,而赤道东太平洋的ENSO循环对7、8两月的雨带有重要影响。对我国夏季风雨带季内变化模态与夏季雨型关系的分析则表明,它们之间存在某些联系,但这并不意味着可以相互取代。  相似文献   

Predicting climate anomalies:A real challenge          下载免费PDF全文

Huijun Wang  Yongjiu Dai  Song Yang  Tim Li  Jingjia Luo  Bo Sun  Mingkeng Duan  Jiehua Ma  Zhicong Yin  Yanyan Huang 《大气和海洋科学快报》2022,15(1):2-11

过去几十年,气候变化和极端气候事件造成的经济损失和灾害显著增加.虽然全球的科学家在理解和预测气候变异方面做出了巨大的努力,但当前在气候预测领域仍然存在几个重大难题.2020年,依托于国家自然科学基金基础科学中心项目的气候系统预测研究中心(CCSP)成立了,该中心旨在应对和处理气候预测领域的三大科学难题:厄尔尼诺-南方涛动(ENSO)预测,延伸期天气预报,年际-年代际气候预测,并为更加准确的气候预测和更加有效的灾害防御提供科学依据.因此,本文介绍了CCSP的主要目标和面对的科学挑战,回顾了CCSP在季风动力过程,陆-气相互作用和模式开发,ENSO变率,季节内振荡,气候预测等方面已取得的重要研究成果.未来CCSP将继续致力于解决上述领域的关键科学问题.  相似文献   

Seasonal Rainfall Forecasts for the Yangtze River Basin in the Extreme Summer of 2020※     

Philip E.BETT  Gill M.MARTIN  Nick DUNSTONE  Adam A.SCAIFE  Hazel E.THORNTON  Chaofan LI 《大气科学进展》2021,38(12):2212-2220

Seasonal forecasts for Yangtze River basin rainfall in June, May–June–July (MJJ), and June–July–August (JJA) 2020 are presented, based on the Met Office GloSea5 system. The three-month forecasts are based on dynamical predictions of an East Asian Summer Monsoon (EASM) index, which is transformed into regional-mean rainfall through linear regression. The June rainfall forecasts for the middle/lower Yangtze River basin are based on linear regression of precipitation. The forecasts verify well in terms of giving strong, consistent predictions of above-average rainfall at lead times of at least three months. However, the Yangtze region was subject to exceptionally heavy rainfall throughout the summer period, leading to observed values that lie outside the 95％ prediction intervals of the three-month forecasts. The forecasts presented here are consistent with other studies of the 2020 EASM rainfall, whereby the enhanced mei-yu front in early summer is skillfully forecast, but the impact of midlatitude drivers enhancing the rainfall in later summer is not captured. This case study demonstrates both the utility of probabilistic seasonal forecasts for the Yangtze region and the potential limitations in anticipating complex extreme events driven by a combination of coincident factors.  相似文献   

热带印度洋秋季偶极子模态与南海夏季风强度变化的关系   总被引：2，自引：1，他引：2  

李东辉  张瑰  朱益民  谭言科  王学忠 《热带气象学报》2006,22(5):439-446

利用多年的Reynolds月平均海表温度资料和NCEP／NCAR全球大气再分析资料，采用经验正交函数（EOF）分析和滑动相关方法，研究了热带印度洋秋季偶极子模态和南海夏季风强度变化的关系。结果表明：（1）热带印度洋秋季海表温度距平（SSTA）的主要模态是全区一致型和偶极子（IOD）型，全区一致型模态主要代表了秋季SSTA全海盆一致的年代际及其以上时间尺度的变化，IOD型模态主要反映热带印度洋秋季SSTA年际时间尺度的变化。（2）当前期秋季热带印度洋存在正（负）IOD模态时，南海的夏季风强度减弱（增强）。二者年际变化的负相关关系在长期趋势的冷位相期不显著，而在暖位相期显著。（3）当南海夏季风强度增强（减弱）时，后期秋季热带印度洋出现正（负）IOD模态。二者年际变化的正相关关系在长期趋势的冷、暖位相期显著，在冷、暖位相转换期前后不显著。  相似文献   

季风涡旋对热带气旋生成影响的理想试验研究   总被引：1，自引：0，他引：1  

徐梦婷  周顺武  葛旭阳 《气象学报》2016,74(5):733-743

利用新一代非静力平衡中尺度数值模式WRF_ARW（3.3.1版本）模拟季风涡旋中热带气旋生成的过程,从动力和热力作用两方面分析大尺度季风涡旋对热带气旋生成的影响。结果表明:从动力学角度来看,能提供较大环境场涡度的季风涡旋不利于扰动涡旋快速发展成热带气旋。初始阶段,由于季风涡旋尺度大,垂直涡度径向梯度弱。而垂直涡度径向梯度的强弱可以通过“涡度隔离”效应影响对流单体向涡旋中心的聚集合并过程。随着扰动的组织化,径向入流对涡度的平流作用越来越重要。对流单体相对最大风速半径的位置对热带气旋生成作用明显,当其集中在最大风速半径附近时涡旋容易快速发展。此外,环境场相对涡度与热带气旋的尺度存在显著正相关。初始尺度大的涡旋最终具有较大的外围尺度,其涡度的分布范围也更广。从热力学角度来说,较大的环境场相对湿度有利于热带气旋的生成。虽然较大的环境场湿度能够诱发较强的外围对流,但同时也会使最大风速半径以内存在丰富的对流,后者能够提供充分的内区非绝热加热,降低中心气压,促进涡旋发展。   相似文献   

1994年华南暴雨期间夏季风的特征及其对水汽的输送   总被引：9，自引：4，他引：9  

吕梅  成新喜  陈中一  陆汉城 《热带气象学报》1998,14(2):135-141

用拉格朗日方法计算等熵面上空气质点和物质的轨迹。分析指出１９９４年华南暴雨和夏季风异常有密切的关系,特别是东亚热带季风更是决定性的作用;用这种方法可以追踪水汤的源地及演变过程,分析气流对水汽的输送作用。  相似文献   

南海西部54万年以来元素地球化学记录及其反映的古环境演变   总被引：3，自引：1，他引：2  

贺子丁  刘志飞  李建如  谢昕 《地球科学进展》2012,27(3):327-336

通过对南海西部上升流区MD05-2899孔开展高分辨率碳酸盐地层学和XRF岩芯扫描元素地球化学分析,重建了晚第四纪54万来以来东亚夏季风的演化历史,探讨海平面升降对南海西部陆源碎屑供应量的影响。研究选用了ln(Ba/Al)作为该海区古生产力的指标,ln(Br/Al)作为有机物的指标,ln(Ti/Al)作为陆源碎屑供应量的指标。研究结果显示,东亚夏季风在过去54万年以来强度不断增强,具有明显的冰期—间冰期旋回特征,在间冰期强盛和冰期减弱,是控制该海区有机物含量变化的主要因素。东亚夏季风不断强盛可能直接导致了南海周边陆地降雨增强,河流径流量加大,使得南海西部上升流区域的陆源碎屑供应量在间冰期明显高于冰期。研究发现,当相对海平面低于-60 m的时候,大面积暴露的巽他陆架可能向南海西部深水区输入大量陆源碎屑物质,造成研究站位的陆源碎屑供应量在冰盛期出现高值。因此,晚第四纪的东亚夏季风演化和海平面升降共同控制了南海西部上升流区陆源碎屑物质供应量的变化。  相似文献   

Impact of monsoon-driven circulation on phytoplankton assemblages near fringing reefs along the east coast of Hainan Island,China     

《Deep Sea Research Part II: Topical Studies in Oceanography》2013

Monsoonal hydrodynamic prevails over the east coast of Hainan Island induced by southwest monsoon (SWM) and northeast monsoon (NEM) which drives coastal Ekman divergence/convergence cycle and the reversal of Guangdong coastal current (GCC) between the sGCC in the SWM season and nGCC in the NEM season. We report the control of such hydrodynamics on biological properties such as phytoplankton assemblages in the east coast of Hainan Island. Physico-chemical and biological observations were carried out in two oceanographic cruises along the east coast of Hainan Island during SWM period (July–August) of 2008 and NEM period (March–April) of 2009. Results indicated that phytoplankton assemblages in coastal regions (fringing reefs and coastal shelf) changed dramatically accompanied with the reverse of monsoonal hydrodynamic processes, with chain-forming diatoms (mainly, Pseudo-nitzschia spp. and Thalassionema nitzschioides) dominating during SWM cruise when coastal Ekman divergence and the sGCC were prevailed, but the pelagic Noctiluca scintillans and Trichodesmium erythraeum dominating during NEM cruise when coastal Ekman convergence and the nGCC were prevailed. Furthermore, phytoplankton assemblages in fringing reefs along coastline were somewhat different from ones of coastal shelf, as fringing reefs are just located at dynamic boundary of offshore (or onshore) Ekman transport processes. Offshore diffusion of pelagic cells (such as T. erythraeum) driven by offshore Ekman transport process led to the lower abundance of T. erythraeum in fringing reefs than ones in coastal shelf during SWM cruise; on the contrary, onshore aggregation of pelagic cells (such as N. scintillans and T. erythraeum) driven by onshore Ekman transport process leads to higher abundances of N. scintillans and T. erythraeum in fringing reefs than ones in coastal shelf during NEM cruise; especially, N. scintillans formed bloom in fringing reefs. Last, we suggested that hydrodynamic processes must be taken into account in scientific management of fringing coral reefs health of the east coast of Hainan Island, especially during northeast monsoon season when blooming specie cells (such as N. scintillans) could be introduced from eutrophic South China mainland coast to the east coast of Hainan Island and piled to high-abundance at fringing reefs by monsoonal hydrodynamics.  相似文献   

Recent Sea Level and Sea Surface Temperature Changes Along the Maldives Coast     

O. P. Singh  Tariq Masood Ali Khan  Fahmida Aktar  Majajul Alam Sarker 《Marine Geodesy》2013,36(4):209-218

Maldives, a South Asian small island nation in the northern part of the Indian Ocean is extremely vulnerable to the impacts of Sea Level Rise (SLR) due to its low altitude from the mean sea level. This artricle attempts to estimate the recent rates of SLR in Maldives during different seasons of the year with the help of existing tidal data recorded in the Maldives coast. Corresponding Sea Surface Temperature (SST) trends, utilizing reliable satellite climatology, have also been obtained. The relationships between the SST and mean sea level have been comprehensively investigated. Results show that recent sea level trends in the Maldives coast are very high. At Male, the capital of the Republic of Maldives, the rising rates of Mean Tidal Level (MTL) are: 8.5, 7.6, and 5.8 mm/year during the postmonsoon (October-December), Premonsoon (March-May) and southwest monsoon (June-September) seasons respectively. At Gan, a station very close to the equator, the increasing rate of MTL is maximum during the period from June to September (which is 6.2 mm/year). These rising trends in MTL along the Maldives coast are certainly alarming for this small developing island nation, which is hardly one meter above the mean sea level. Thus there is a need for careful monitoring of future sea level changes in the Maldives coast. The trends presented are based on the available time-series of MTL for the Maldives coast, which are rather short. These trends need not necessarily reflect the long-term scenario. SST in the Maldives coast has also registered significant increasing trend during the period from June to September. There are large seasonal variations in the SST trends at Gan but SST and MTL trends at Male are consistently increasing during all the seasons and the rising rates are very high. The interannual mode of variation is prominent both in SST as well as MTL. Annual profile of MTL along the Maldives coast is bimodal, having two maxima during April and July. The April Mode is by far the dominant one. The SST appears to be the main factor governing the sea level variations along the Maldives coast. The influence of SST and sea level is more near the equatorial region (i.e., at Gan). There is lag of about two months for the maximum influence of SST on the sea level. The correlation coefficient between the smoothed SST and mean tidal level at Gan with lag of two months is as high as ~ +0.8, which is highly significant. The corresponding correlation coefficients at Male with the lags of one and two months are +0.5 and +0.3, respectively. Thus, the important finding of the present work for the Maldives coast is the dominance of SST factor in sea level variation, especially near the region close to the equator.  相似文献   

Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon   总被引：1，自引：1，他引：0  

O. P. Singh Tariq Masood Ali Khan  Tad S. Murty  Md. Sazedur Rahman 《Marine Geodesy》2013,36(1):65-72

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.  相似文献