Interannual and Interdecadal Variations in Heat Content of the Upper Ocean of the South China Sea

The vertically averaged temperature (TAV) from surface to 100 m depth of the South China Sea for the period 1959-1988 is analyzed. The results indicate that there is a significant long-term variability from interannual to interdecadal scales in the heat content in the upper ocean. The heat content of the upper ocean of the South China Sea increases evidently in the El Nino year. TAV anomaly in the ocean was negative from the end of 1950’s to early l970’s, and then changed to positive. The changes of TAV of the ocean are closely related to ENSO events, the Asian winter monsoon and the tropical atmospheric circulation anomalies.     

Internal tides in the coastal zone of the Sea of Japan in autumn

The results are presented of hydrological studies in the coastal zone of the Sea of Japan in autumn in different years. It is revealed that the typical density stratification of water is formed there in autumn. The amplitudes are estimated of regular (with the periodicity of tidal harmonic M₂) vertical displacements of isotherms in the intermediate layer and maximum values of flow velocity in the surface and bottom layers. It is demonstrated that temperature perturbations are induced at the shelf edge and propagate to the coastal zone with the velocity that is close to the velocity of the first mode of internal gravity waves with the frequency of the tidal harmonic M₂.     

秋季西北太平洋热带气旋累积能量的年际变化及其预报

秋季是西北太平洋热带气旋平均强度最强的季节,热带气旋累积能量（accumulated cyclone energy, ACE）是热带气旋平均强度的表征指标,基于1979—2015年日本气象厅最佳路径热带气旋数据集,以及美国冰雪中心海冰数据和哈得来环流中心海温数据,利用回归分析和多元逐步回归等方法,对秋季西北太平洋ACE指数进行了分析和预报。研究表明：秋季西北太平洋ACE指数具有显著的年际变化特征,与厄尔尼诺-南方涛动（ENSO）有关,最大和最小值分别出现在1991年的厄尔尼诺年和1999年的拉尼娜年,在厄尔尼诺发展年的秋季ACE一般较强,而在拉尼娜衰减年的秋季热带气旋强度则较弱;ACE指数变化受来自北极海冰变化强迫中纬度异常波列的影响及其受到厄尔尼诺海温模态的调制;由于海冰在波弗特海的异常增多,强迫对流层高层夏季出现类似北半球环球遥相关型异常波列,波列正压下传,使得夏秋季西北太平洋副热带高压东退北移;副热带高压活动的变化和太平洋海温的异常分布影响了局地的环流,热带气旋生成源地弱的垂直风切变区域偏东和涡度显著增大有利于热带气旋在暖海洋上发展强盛。最后进行建模预报,预报效果为0.69。若单独使用海温或海冰作为唯一要素来预报,预报效果将大大降低。     

Interannual variability of water discharge through the Korea (Tsushima) Strait and its influence on the dissolved oxygen content in the Sea of Japan

The interannual variations of the sea level at the coastal stations of the Sea of Japan and of the water discharge through the Korea (Tsushima) Strait are studied. It is demonstrated that the interannual variations of the water discharge through this strait are determined by the water discharge of the Oyashio (in the subarctic Pacific) and the Kuroshio (in the East China Sea) currents and by the zonal wind stress component over the Sea of Japan in winter period. It is revealed that the variations in the East China Sea water transport through the Korea (Tsushima) Strait cause the interannual variations of the dissolved oxygen content in intermediate (500 m) and deep (1000 m and more, σ_θ = 27.35) waters of the Sea of Japan.     

晚秋前冬海洋性大陆区域向外长波辐射年际变化及其与云贵高原降水异常的联系

利用美国国家海洋和大气管理局(NOAA)向外长波辐射(OLR)月平均资料、欧洲中期数值预报中心(ECMWF)ERA-interim月平均再分析资料、全球降水气候中心(GPCC)降水资料及中国气象局国家气象信息中心提供的中国756站逐日观测资料,通过定义一个海洋性大陆区域对流强度指数(I_OLR),分析了海洋性大陆区域(Maritime Continent,MC)近35年来11月—次年1月对流活动特征,并揭示了11月—次年1月海洋性大陆区域对流活动强度的年际变化与同期云贵高原降水的联系。结果表明:海洋性大陆区域对流活动除了有逐渐增强的趋势外,还存在3—5 a及8—10 a的振荡周期。当海洋性大陆区域对流活动偏弱(强)时,云贵高原西部降水偏少(多),东部降水偏多(少),高原东西部之间降水分布差异加大(减小)。引起云贵高原降水异常的原因有3个方面:一是在海洋性大陆区域与云贵高原间存在显著的异常垂直环流圈,当下沉(上升)支位于海洋性大陆区域时,上升(下沉)支将位于云贵高原地区。而云贵高原地形可能对云贵高原降水异常在东南部和西北部的差别的产生存在影响;二是海洋性大陆区域在对流层低层的辐散和对流层上层的辐合运动为热带和高原以东地区提供了异常的位涡强迫,直接导致对流层低层南海—孟加拉湾地区异常反气旋和对流层上层位于中国南方的异常气旋性环流的产生;三是由于海洋性大陆区域辐散运动作为位涡制造而激发的位涡扰动的能量从热带地区向云贵高原及其东侧频散并辐合,对云贵高原上空扰动异常的维持起到了重要作用。这些结果有利于深刻理解云贵高原冬季降水异常的形成机理以及为寻找降水异常预测因子提供了有用的线索。     

冬季北半球大气对秋冬季巴伦支海海冰异常的敏感性研究

基于ERA-Interim再分析资料,借助大气模式CAM4,分析了北半球冬季不同月份的平均大气对巴伦支海不同振幅及不同季节海冰扰动的敏感性,并考察了中高纬度典型大气模态的分布变化情况.结果表明,冬季巴伦支海海冰的减少,会导致湍流热通量异常向上、局地异常变暖及水汽含量的异常升高,且相关异常的强度和范围随着海冰减少幅度的减...     

Interannual and intraannual variations in total precipitable water over the North Atlantic from satellite microwave measurements

Based on the long-term data of satellite microwave radiometers, the estimates are obtained of interannual and intraannual variations in monthly mean values of total precipitable water in the atmosphere over the North Atlantic from 1988 to 2011, in particular, in the regions characterized by the maximum rate of heat and moisture exchange between the ocean and atmosphere such as the Gulf Stream, Newfoundland, and Norway-Greenland energy-active zones. Long-term trends in total precipitable water in the atmosphere over these regions are estimated. The variations in total precipitable water in the atmosphere in 2010 are noted which were caused by oil spills in the Gulf of Mexico (the spring of 2010) and by the severe drought in the European part of Russia (the summer of 2010).     

Interannual and interdecadal oscillation patterns in sea level

Relative sea-level height (RSLH) data at 213 tide-gauge stations have been analyzed on a monthly and an annual basis to study interannual and interdecadal oscillations, respectively. The main tools of the study are singular spectrum analysis (SSA) and multi-channel SSA (M-SSA). Very-low-frequency variability of RSLH was filtered by SSA to estimate the linear trend at each station. Global sea-level rise, after postglacial rebound corrections, has been found to equal 1.62±0.38 mm/y, by averaging over 175 stations which have a trend consistent with the neighboring ones. We have identified two dominant time scales of El Niño-Southern Oscillation (ENSO) variability, quasi-biennial and low-frequency, in the RSLH data at almost all stations. However, the amplitudes of both ENSO signals are higher in the equatorial Pacific and along the west coast of North America. RSLH data were interpolated along ocean coasts by latitudinal intervals of 5 or 10 degrees, depending on station density. Interannual variability was then examined by M-SSA in five regions: eastern Pacific (25°S–55°N at 10° resolution), western Pacific (35°S–45°N at 10°), equatorial Pacific (123°E–169°W, 6 stations), eastern Atlantic (30°S, 0°, and 30°N–70°N at 5°) and western Atlantic (50°S–50°N at 10°). Throughout the Pacific, we have found three dominant spatio-temporal oscillatory patterns, associated with time scales of ENSO variability; their periods are 2, 2.5–3 and 4–6 y. In the eastern Pacific, the biennial mode and the 6-y low-frequency mode propagate poleward. There is a southward propagation of low-frequency modes in the western Pacific RSLH, between 35°N and 5°S, but no clear propagation in the latitudes further south. However, equatorward propagation of the biennial signal is very clear in the Southern Hemisphere. In the equatorial Pacific, both the quasi-quadrennial and quasi-biennial modes at 10°N propagate westward. Strong and weak El Niño years are evident in the sea-level time series reconstructed from the quasi-biennial and low-frequency modes. Interannual variability with periods of 3 and 4–8 y is detected in the Atlantic RSLH data. In the eastern Atlantic region, we have found slow propagation of both modes northward and southward, away from 40–45°N. Interdecadal oscillations were studied using 81 stations with sufficiently long and continuous records. Most of these have variability at 9–13 and some at 18 y. Two significant eigenmode pairs, corresponding to periods of 11.6 and 12.8 y, are found in the eastern and western Atlantic ocean at latitudes 40°N–70°N and 10°N–50°N, respectively.     

秋季巴伦支海海冰与中国京津冀地区2月气温变化的联系

利用中国京津冀地区94个气象台站气温观测资料以及美国国家环境预报中心和国家大气研究中心联合制作的再分析资料、美国国家海洋和大气管理局海冰密集度资料,采用经验正交函数分解、相关分析、回归分析、合成分析等方法,研究冬季气候变暖背景下近32 a中国京津冀地区Feb_4-20(2月4—20日)平均气温异常与前期秋季北极海冰异常的关系,探讨秋季巴伦支海海冰影响中国京津冀地区Feb_4-20气温的可能机制。结果表明：(1)1988/1989年冬季是中国京津冀地区冬季变暖的突变点,暖背景下Feb_4-20气温第一模态呈空间一致变化型,其时间系数年际变化特征明显;(2)秋季巴伦支海、喀拉海和东西伯利亚海关键区海冰密集度与中国京津冀地区Feb_4-20气温存在显著正相关,可作为Feb_4-20气温预测的前兆信号;(3)秋季巴伦支海关键区多(少)冰年,其冬季海冰也偏多(少),为持续冷(热)源,在欧亚大陆对流层中高层激发出负(正)位相的斯堪的纳维亚遥相关型分布,西伯利亚高压偏弱(强),欧亚中高纬近地面多为南(...     

Interannual variability of water transport by the East Kamchatka and East Sakhalin Currents and their influence on dissolved oxygen concentration in the Sea of Okhotsk and subarctic pacific

The influence of interannual variability of water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current on the dissolved oxygen concentration in the western subarctic Pacific and the Sea of Okhotsk is considered for studying climate change impact on sea water chemical parameters. It is shown that statistically significant relation is observed between the calculated with the Sverdrup equation interannual variations in water transport with the East Kamchatka Current, the Oyashio, and the East Sakhalin Current and changes in mean sea water level at coastal stations in winter. It is found that the main reason of interannual variability of the dissolved oxygen concentration at isopycnic surfaces in the intermediate water layer (100–800 m) of the Sea of Okhotsk and in the western subarctic Pacific is caused by variations in water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current.     

东北地区夏季干旱的年际—年代际变化特征

利用国家气候中心提供的1951—2012年160个标准站的逐月降水和温度资料,计算了表征东北地区干旱的SPEI指数,并对该指数进行EMSD分解,研究了东北地区干旱的年际—年代际变化特征。结果表明,东北地区夏季干旱年际—年代际变化特征明显,年际变化中具有显著的准2 a、准5 a和准7 a振荡周期;年代际变化中则具有显著的准17 a和22 a振荡周期。进一步分析发现,1975—1984年和1994—2008年为相对干旱阶段,其中1994—2008年旱情比较严重,1953—1975年、1984—1994年以及2009—2012年为相对湿润阶段。Mann-Kendal检验结果表明,东北地区夏季旱涝突变发生在1975年和1994年。     

Physical processes responsible for the interannual variability of sea ice concentration in Arctic in boreal autumn since 1979

Arctic sea ice concentration (ASIC) in boreal autumn exhibits prominent interannual variability since 1979. The physical mechanism responsible for the year-to-year variation of ASIC is investigated through observational data analyses and idealized numerical modeling. It is found that the ASIC interannual variability is closely associated with the anomalous meridional circulations over the Northern Hemisphere, which is further linked with the tropical sea surface temperature (SST) forcing. A tropics-wide SST cooling anomaly leads to an enhanced meridional SST gradient to the north of the equator in boreal summer, generating strengthened and northward shifting Hadley circulation over the Northern Hemisphere. Consequently, the meridional circulations are enhanced and pushed poleward, leading to an enhanced descending motion at the North Pole, surrounded by an ascending motion anomaly; the surface outflow turns into easterly anomalies, opposing the mean-state winds. As a result, positive cloudiness and weakened surface wind speed emerge, which reduce ASIC through changes in the surface latent heat flux and the downward longwave radiation.     

Interannual variations in the local spatial autocorrelation of tropospheric temperatures

Many dimensions of the global temperature pattern have been explored intensely over the past few decades. In this investigation, we explore the underlying spatial autoregressiveness of annual tropospheric temperature anomalies measured by polar-orbiting satellites. We found that the percent of the Earth covered by areas of significantly high local autocorrelation ranged from 11.92% to 25.90% over the 1979 to 2008 study period. We gathered 13 different teleconnection indices that have been linked to regional to global temperatures and found two (Polar/Eurasia pattern and North Atlantic Oscillation) that were positively correlated to the percent area with high local spatial autocorrelation. The magnitude but not the sign of the El Ni?o Southern Oscillation is also an important factor in the variation of spatial autocorrelation. The physical mechanism driving high local spatial autocorrelation is thought to be zonal and hemispheric flow governed by the subtropical and polar jet streams.     

Interannual variability and predictability of sea level along the Indian Coast

Summary The Indian coast stretching more than 7,500 km constitutes the major portion of the South Asian coastline in the North Indian Ocean region. The South Asian region is significantly influenced by meteorological/oceanographic phenomena like monsoons, El Ni?o/Southern Oscillation (ENSO) and tropical cyclones. Direct/indirect impacts of these phenomena, which exhibit large interannual variabilities, on sea level changes in this region are considerable. Our results show that the mean sea level along the eastern coast of India, which is highly vulnerable to the incidence of severe tropical cyclones, is considerably higher than normal during the intense cyclonic period of a year falling in the positive phase of the Southern Oscillation (La Ni?a epoch), thereby enhancing the hazardous potential of tropical cyclones. Further, in the closing phase of the La Ni?a southwest monsoon, higher sea level anomalies prevail along the Indian coast raising the flooding potential of such monsoons. Over the west coast of India significant simultaneous correlations have been found between the amount of southwest monsoon rainfall and the mean sea level during the period from June to September. Over the east coast of India at Visakhapatnam, mean sea level is predictable with a fair degree of confidence one month in advance, by using the Sea Surface Temperature (SST) and the Southern Oscillation Index (SOI) as predictors. These results will be useful in the annual preparedness programmes aimed at mitigating the impacts of natural disasters like tropical cyclones and floods in the South Asian region. Received November 9, 2001     

北印度洋—南海海面风速和有效波高的年代际变化

采用1958年1月—2001年12月ECMWF ERA-40的10m风场资料,以及由该风场资料驱动WAVEWATCHⅢ得到的北印度洋—南海海域44a的海浪场资料,通过EOF分析、正交小波分析和M-K检测方法,分析了北印度洋—南海海域海面风场和有效波高的年代际变化特征。结果表明：北印度洋—南海海域存在3个大风、大浪区,其中亚丁湾以东洋面风力最强,有效波高最高;表面风场和有效波高存在35、15和3a的主周期变化,并自20世纪70年代中期以来,年平均风场和有效波高均存在明显增强趋势,1977年为突变起始年;年平均海表10m风速和有效波高随时间增大主要是由冬季和春季海表10m风速和有效波高随时间增大引起的;冬、秋季海面风场与有效波高的年际、年代际变化周期较一致,冬季以35～40a的周期为主,秋季以11～12a的周期为主。     

Impact of interannual variations of spring sea ice in the Barents Sea on East Asian rainfall in June

本研究揭示了春季巴伦支海海冰偶极子分布的年际变化和东亚夏季降水之间存在显著关联。对应春季巴伦支海北部海冰增加、东南部海冰减少,东亚夏季雨带位置向北移动。这两者主要是通过初夏欧亚大陆北部对流层低层的波列联系起来:该波列从极地向东南传播到东亚北部地区,导致东北亚低压增强,进而引起东亚夏季雨带北侧降水增加,雨带位置北移。该研究暗示春季巴伦支海海冰偶极子模态作为一个前期预测因子,有利于提高东亚夏季降水预测。     

一个冰气相互作用数值模拟结果的可能统计解释

基于一个全球海-冰-气耦合模式的数值模拟结果,选取冬季格陵兰海海表面温度(SST)、海冰密集度、海表面感热通量等物理量以及3个相关区域海平面气压分别作经验正交函数展开,取第一模时间系数作相关分析。结果表明,上一年海冰密集度偏大(小)与来年的SST偏低(高)相联系,但二者同期相关性最大。当海气热通量交换变化超前一年时,其与SST相关性最大。模式最低层大气温度与海洋表面热通量之间的同时相关性最大,冬季模式最低层气温偏高(低)与海洋表面失去的感热、潜热通量偏少(多)相联系。气温、比湿都和冰岛低压区及格陵兰海的海平面气压相关性最强,冰岛低压气压偏低(高)与模式最低层气温和比湿偏高(低)相联系。所以,在海-冰-气年际尺度的相互作用中,主要关系是大气环流调整造成大气中云量和低层气温、湿度变化,进而影响海气界面上的通量交换,造成SST的变化。SST变化决定着海冰范围及海冰密集度的变化,但海冰变化时通过相变潜热的释放或吸收反过来对SST变化有较明显影响。     

Interannual and interdecadal variations of tropical cyclone activity over the western North Pacific

Summary This paper reviews the interannual and interdecadal variations in tropical cyclone (TC) activity over the western North Pacific (WNP) and the possible physical mechanisms responsible for such variations. Interannual variations can largely be explained by changes in the planetary-scale flow patterns. Sea-surface temperatures (SSTs) in the WNP, however, do not contribute to such variations. Rather, SSTs in the central and eastern equatorial Pacific are significantly correlated with TC activity over the WNP. Causality can be established: changes in the SST in the equatorial Pacific are related to the El Niño/Southern Oscillation (ENSO) phenomenon, and modifications of the planetary-scale flow associated with ENSO alter the conditions over the WNP and hence TC activity there. Variations in annual TC activity are also associated with different phases of the stratospheric quasi-biennial oscillations due to its modification of the vertical wind shear of the environment in which TCs form. Interdecadal variations in TC activity are apparently related to the location, strength and extent of the North Pacific subtropical high. However, the mechanisms responsible for modifying these characteristics of the subtropical high have yet to be identified.