印度洋dipole事件的年际变化与ENSO事件的联系

通过对nino3指数和DMI序列的分析,发现两种物理现象都有4 a左右的主要周期,而且印度洋偶极子事件还存在有2 a左右的振荡周期,而厄尔尼诺事件在2 a时间尺度上周期性不明显;对nino3指数和DMI进行年际时间尺度滤波,结果表明,在年际时间尺度上,两者的相关性比未滤波时有了一定的提高;对年际滤波之后的偶极子事件和ELNINO事件的相关分析可以发现,ELNINO对于印度洋偶极子事件的影响要大于IOD对于太平洋ENSO事件,显示了两者物理现象的影响不对称。     

印度洋dipole事件的年际变化与ENSO事件的联系

通过对nino3指数和DMI序列的分析，发现两种物理现象都有4a左右的主要周期，而且印度洋偶极子事件还存在有2a左右的振荡周期，而厄尔尼诺事件在2a时间尺度上周期性不明显；对nino3指数和DMI进行年际时间尺度滤波，结果表明，在年际时间尺度上，两者的相关性比未滤波时有了一定的提高；对年际滤波之后的偶极子事件和ELNINO事件的相关分析可以发现，ELNINO对于印度洋偶极子事件的影响要大于IOD对于太平洋ENSO事件，显示了两者物理现象的影响不对称。     

Influence of Indian Ocean Dipole on Tropical Cyclone Activity over Western North Pacific in Boreal Autumn

In this study, we investigated the influence of the Indian Ocean Dipole(IOD) on the interannual variability of tropical cyclone(TC) activity over the western North Pacific(WNP) during autumn(September–November) from 1961–2015. We found the number of TCs making landfall in China to be significantly negatively correlated with the IOD index, which can be attributed to shifts in the location of TC formation together with the abnormal steering flow at 500 hPa. During negative IOD autumns, TC genesis regions move obviously westward due to the westward retreat of the WNP monsoon trough. The TC activity is remarkably enhanced near South China coastal areas, which is due to a contiguous 500-hPa subtropical ridge. In contrast, during positive IOD autumns, TC genesis positions obviously shift eastward and more TCs tend to exhibit recurvature around 130?E or a westward path south of 15?N led by an equatorward movement of the 500-hPa subtropical ridge with a break near 125?E. In our examination of large-scale circula-tion, we found a pair of equator-symmetric anticyclones in the lower troposphere resulting from variations in the large-scale Walker circulation induced by the anomalous sea surface temperature(SST) associated with a positive IOD. The resulting Philippines anti-cyclonic anomalies are closely related to the variability of the monsoon trough over the WNP region. Furthermore, the variations in the steering flow can be explained by the suppressed(enhanced) convective activities around the Philippines and the weakened(strengthened) local meridional circulation over East Asia in positive(negative) IOD years.     

Variations of SST and thermocline depth in the tropical Indian Ocean during Indian Ocean Dipole events

Interannual variations in the surface and subsurface tropical Indian Ocean were studied using HadISST and SODA datasets.Wind and heat flux datasets were used to discuss the mechanisms for these variations.Our results indicate that the surface and subsurface variations of the tropical Indian Ocean during Indian Ocean Dipole(IOD)events are significantly different.A prominent characteristic of the eastern pole is the SSTA rebound after a cooling process,which does not take place at the subsurface layer.In the western pole,the surface anomalies last longer than the subsurface anomalies.The subsurface anomalies are strongly correlated with ENSO,while the relationship between the surface anomalies and ENSO is much weaker.And the subsurface anomalies of the two poles are negatively correlated while they are positively correlated at the surface layer.The wind and surface heat flux analysis suggests that the thermocline depth variations are mainly determined by wind stress fields,while the heat flux effect is important on SST.     

Influence of ENSO Events on Tropical Cyclone Activity over the Western North Pacific

Based on an analysis of 51-year(1965–2015) data, the influence of El Ni?o–Southern Oscillation(ENSO) events on tropical cyclone(TC) activity is examined over the western North Pacific(WNP). The total number of TCs formed in the entire WNP reduces by about 3.4 TCs per year in La Ni?a years, whereas TCs have an equivalent genesis number between El Ni?o years and climatology. During El Ni?o years, the frequency of TC formation increases remarkably in the southeast quadrant(140?E–180?, 0?–17?N) and decreases in the northwest quadrant(120?–140?E, 17?–30?N). During La Ni?a years, TCs tend to form in the northwest and southwest quadrants(120?–140?E, 0?–17?N) quadrants. TCs tend to become long-lived in the peak season(from July to September) of El Ni?o years and during strong El Ni?o events. TC genesis shows a southeastward positive shift in terms of lifetime and intensity during El Ni?o years, thus more super TCs(winds ≥ 58.64 m s-1) are formed in the southeast quadrant. Further analysis using the genesis potential index(GPI) indicates that the interannual variations in the TC genesis and track are significantly influenced by a combination of large-scale dynamic and thermodynamic conditions.     

Surface Heat Budget and Solar Radiation Allocation at a MeltPond During Summer in the Central Arctic Ocean

The heat budget of a melt pond surface and the solar radiation allocation at the melt pond are studied using the 2010Chinese National Arctic Research Expedition data collected in the central Arctic. Temperature at a melt pond surface is proportionalto the air temperature above it. However, the linear relationship between the two varies, depending on whether the air temperature ishigher or lower than 0°C. The melt pond surface temperature is strongly influenced by the air temperature when the latter is lowerthan 0°C. Both net longwave radiation and turbulent heat flux can cause energy loss in a melt pond, but the loss by the latter is largerthan that by the former. The turbulent heat flux is more than twice the net longwave radiation when the air temperature is lower than0°C. More than 50% of the radiation energy entering the pond surface is absorbed by pond water. Very thin ice sheet on the pondsurface （black ice） appears when the air temperature is lower than 0°C; on the other hand, only a small percentage （5.5%） of netlongwave in the solar radiation is absorbed by such a thin ice sheet.     

Revisiting the Seasonal Evolution of the Indian Ocean Dipole from the Perspective of Process-Based Decomposition

The seasonal phase-locking feature of the Indian Ocean Dipole(IOD) is well documented. However, the seasonality tendency of sea surface temperature anomalies(SSTAs) during the development of the IOD has not been widely investigated. The SSTA tendencies over the two centers of the IOD peak in September-October-November are of different monthly amplitudes. The SSTA tendency over the west pole is small before June-July-August but dramatically increases in July-August-September. Meanwhile, the SSTA ...     

The role of barrier layer in southeastern Arabian Sea during the development of positive Indian Ocean Dipole events

Using data from Argo and simple ocean data assimilation (SODA), the role of the barrier layer (BL) in the southeastern Arabian Sea (SEAS: 60°E–75°E, 0°–10°N) is investigated during the development of positive Indian Ocean Dipole (IOD) events from 1960 to 2008. It is found that warmer sea surface temperature (SST) in the northern Indian Ocean appears in June in the SEAS. This warm SST accompanying anomalous southeastern wind persists for six months and a thicker BL and a corresponding thinner mixed layer in the SEAS contribute to the SST warming during the IOD formation period. The excessive precipitation during this period helps to form a thicker BL and a thinner mixed layer, resulting in a higher SST in the SEAS. Warm SST in the SEAS and cold SST to the southeast of the SEAS intensify the southeasterly anomaly in the tropical Indian Ocean, which transports more moisture to the SEAS, and then induces more precipitation there. The ocean-atmosphere interaction process among wind, precipitation, BL and SST is very important for the anomalous warming in the SEAS during the development of positive IOD events.     

青藏高原-热带印度洋地区大气热源的时空变化特征

为了寻求青藏高原一热带印度洋地区大气热源空间变化的敏感区,进一步深入研究季风的形成、变异和预测,利用NCEP1979-2008年的再分析资料计算分析了青藏高原一热带印度洋地区30年来不同季节大气热源分布的气候特征,并且利用经验正交函数分解研究了该区大气热源在夏、冬季的时空变化特征。结论如下：春季大气热源有明显的经向差异;夏季的热源明显比春季的热源强度强,范围广,热源最强中心在孟加拉湾北部大陆边缘;秋季热源区域明显南缩,热源强度较夏季明显减弱;冬季大气热源呈西西南一东东北方向分布,大气热源位置继续南移。对于夏季,前3个模态分别反映了青藏高原一热带印度洋地区大气热源的纬向差异型、经向差异型、西北一东南分布型。对于冬季,前3个模态分别反映了青藏高原一热带印度洋地区大气热源的经向差异主导型、经向差异型、纬向差异型。     

夏冬季热带太平洋、印度洋海表温度年际异常的年代际变化

用Nino 3指数、印度洋单极指数、偶极子指数描述热带太平洋、印度洋海表温度 (SST)的年际异常 ,季节分析表明 :冬季Nino3区与热带印度洋海表温度距平 (SSTA)相互关系表现为单极 ,且 1976年以后两者的相互关系减弱 ,其可能原因 :一是冬季是ENSO(厄尔尼诺 )事件的盛期 ;二是冬季西太平洋暖水区东移 ,造成两洋的垂直纬向环流耦合减弱。夏季两者相互关系表现为偶极 ,1976年以后两者的相互关系加强 ,其可能原因 ,一是夏季是偶极子盛期 ,ENSO事件的发展期 ;二是夏季西太平洋暖水区虽然东移 ,但暖水区位置偏北 ,且东南印度洋的上升支强度增大 ,造成两洋的纬向环流耦合更强烈     

Diffusion Characteristics of Swells in the North Indian Ocean

Research on the diffusion characteristics of swells contributes positively to wave energy forecasting, swell monitoring, and early warning. In this work, the South Indian Ocean westerly index(SIWI) and Indian Ocean swell diffusion effect index(IOSDEI) are defined on the basis of the 45-year(September 1957–August 2002) ERA-40 wave reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF) to analyze the impact of the South Indian Ocean westerlies on the propagation of swell acreage. The following results were obtained: 1) The South Indian Ocean swell mainly propagates from southwest to northeast. The swell also spreads to the Arabian Sea upon reaching low-latitude waters. The 2.0-meter contour of the swell can reach northward to Sri Lankan waters. 2) The size of the IOSDEI is determined by the SIWI strength. The IOSDEI requires approximately 2–3.5 days to fully respond to the SIWI. The correlations between SIWI and IOSDEI show obvious seasonal differences, with the highest correlations found in December–January–February(DJF) and the lowest correlations observed in June–July–August(JJA). 3) The SIWI and IOSDEI have a common period of approximately 1 week in JJA and DJF. The SIWI leads by approximately 2–3 days in this common period.     

Meridional Variation of the 1955-2003 Sea Level Anomalies in the Tropical Pacific Ocean Associated with El Ni(n)o Events

The Sea Level Anomaly-Torque (SLAT, relative to a reference location in the Pacific Ocean), which means the total torque of the gravity forces of sea waters with depths equal to the Sea Level Anomaly (SLA) in the tropical Pacific Ocean, is defined in this study. The time series of the SLAT from merged altimeter data (1993-2003) had a great meridional variation during the 1997-1998 El Ni(n)o event. By using historical upper layer temperature data (1955-2003) for the tropical Pacific Ocean, the temperature-based SLAT is also calculated and the meridional variation can be found in the historical El Ni(n)o events (1955-2003), which suggests that the meridional shifts of the sea level anomaly are also intrinsic oscillating modes of the El Ni(n)o cycles like the zonal shifts.     

Events of decadal thermocline variations in the South Pacific Ocean

1 INTRODUCTION It has been suggested that interior thermal anomalies that subduct into the subtropics of the North Pacific may propagate to the equatorial region of the Pacific (Russell, 1994; Deser et al., 1996; Gu and Philander, 1997; Huang and Huang an…     

NUMERICAL SIMULATION OF THE MINDANAO EDDY AND TROPICAL CURRENTS OF PACIFIC OCEAN

Results of numerical simulation of currents in the western North Tropical Pacific Ocean by using a barotropic primitive equation model with fine horizontal resolution agreed well with observations and showed that the Mindanao Cyclonic Eddy located north of the equator and east of Mindanao Island exists during most of the year with monthly (and large seasonal) variations in scope . strength and central location . In June , an anticyclonic eddy occurs northeast of Halmahera Island, strengthens to maximum in August , exists until October and then disappears . The observed large-scale circulation systems such as the North Equatorial Current . the Mindanao Current and the North Equatorial Countercurrent are all very well reproduced in the simulations.     

上层海洋对热带风暴“天鹰”的响应

根据2005年7、8月份锚系温盐和海流观测资料并结合卫星遥感数据,重点关注海南岛东南侧热带风暴影响区域,研究了2005年第8号热带风暴"天鹰"引起的上层海水降温机制,分析结果表明:热带风暴过境期间,海表面有着显著的降温,且台风路径右侧海表温度下降的幅值和范围要远大于左侧;观测点处,海表温度下降2~4℃,混合层加深10~20 m,海洋热容量变化为-10~-20 k J·cm~(-2),上升流及垂向夹卷对于海洋热容量的变化有着最重要的作用,是导致海表温度下降的主要原因。而在海表温度降低过程中,通过比较发现,垂向的夹卷相较于上升流又占据着主导作用。     

Contrast between the climatic states of the warm pool in the Indian Ocean and in the Pacific Ocean

Based on the analysis of Levitus data, the climatic states of the warm pool in the Indian Ocean (WPIO) and in the Pacific Ocean (WPPO) are studied. it is found that WPIO has a relatively smaller area, a shallower bottom and a slightly lower seawater temperature than those of WPPO. The horizontal area at different depths, volumes, central positions, and bottom depths of both WPIO and WPPO show quite apparent signals of seasonal variation. The maximum amplitude of WPIO surface area’s seasonal variation is 58% larger over the annual mean value. WPIO’s maximum volume variation amplitude is 66% larger over the annual mean value. The maximum variation amplitudes of the surface area and volume of WPPO are 20.9% and 20.6% larger over the annual mean value respectively. WPIO and WPPO show different temporal and spatial characteristics mainly due to the different wind fields and restriction of ocean basin geometry. For instance, seasonal northern displacement of WPIO is, to some extent, constrained by the basin of the Indian Ocean, while WPPO moves relatively freely in the longitudinal direction. The influence of WPIO and WPPO over the atmospheric motion must be quite different.     

Impacts of Indonesian Throughflow on seasonal circulation in the equatorial Indian Ocean

Impacts of the Indonesian Throughflow(ITF) on seasonal circulation in the equatorial eastern Indian Ocean are investigated using the ocean-only model LICOM by opening and closing ITF passages. LICOM had daily forcing from NCEP reanalysis data during 2000–2011. It can reproduce vertical profiles of mean density and buoyancy frequency of World Ocean Atlas 2013 data. The model also simulates well annual oscillation in the central Indian Ocean and semiannual oscillation in the eastern Indian Ocean of sea level anomalies(SLA) using satellite altimeter data, as well as the semiannual oscillation of surface zonal equatorial currents of Ocean Surface Current Analyses Real Time current data in the equatorial Indian Ocean. The wave decomposition method is used to analyze the propagation and reflection of equatorial long waves based on LICOM output. Wave analysis suggests that ITF blockage mainly influences waves generated from the Indian Ocean but not the Pacific Ocean, and eastern boundary reflections play an important role in semiannual oscillations of SLA and zonal current dif ferences in the equatorial Indian Ocean associated with ITF. Reconstructed ITF-caused SLA using wave decomposition coefficient dif ferences between closed and open ITF-passage experiments suggest both Kelvin and Rossby waves from the first baroclinic mode have comparable contributions to the semiannual oscillations of SLA diff erence. However, reconstructed ITFcaused surface zonal currents at the equator suggest that the first meridional-mode Rossby wave has much greater contribution than the first baroclinic mode Kelvin wave. Both reconstructed sea level and zonal currents demonstrate that the first baroclinic mode has a greater contribution than other baroclinic modes.     

Vertical structure of low-level atmosphere over the south- east Indian Ocean fronts

During the 25th Chinese National Antarctic Research Expedition, GPS radiosondes were launched to detect the atmos- pheric vertical structure over the southeast Indian Ocean frontal region. Some low-level characteristics along the cruise are studied based on in-situ observation. The observations reveal that vertical distributions of the low-level wind field and air temperature field on both sides of the Subantarctic Front are very different. A stronger （weaker） vertical gradient is on the cold （warm） side, which demonstrates that the mid-latitude ocean-atmosphere interaction is active in the southeast Indian Ocean frontal region. A low-level jet is observed over the Subantarctic Front, with speed up to 14 m＇s-1. For the Antarctic polar front, low-level wind speed near the sea surface is greater than that aloft, in contrast with the situation of the Subantarctic Front. Comparing satellite remote sensing data and widely-used reanalysis datasets with our in-situ observations, differences of varying magnitudes are found. Air temperature from Atmospheric Infrared Sounder （AIRS） data has a limited difference. The European Center for Medium Range Weather Forecasts Interim Re-Analysis （ERA Interim） dataset is much more consistent with the observations than the National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） Reanalysis 1 in the southeast Indian Ocean frontal region.     

Intraseasonal variability of the equatorial Pacific Ocean and its relationship with ENSO based on Self-Organizing Maps analysis

We investigated the intraseasonal variability of equatorial Pacific subsurface temperature and its relationship with El Nino-Southern Oscillation(ENSO) using Self-Organizing Maps(SOM) analysis.Variation in intraseasonal subsurface temperature is mainly found along the thermocline.The SOM patterns concentrate in basin-wide seesaw or sandwich structures along an east-west axis.Both the seesaw and sandwich SOM patterns oscillate with periods of 55 to 90 days,with the sequence of them showing features of equatorial intraseasonal Kelvin wave,and have marked interannual variations in their occurrence frequencies.Further examination shows that the interannual variability of the SOM patterns is closely related to ENSO;and maxima in composite interannual variability of the SOM patterns are located in the central Pacific during CP El Nino and in the eastern Pacific during EP El Nino.The se results imply that some of the ENSO forcing is manife sted through changes in the occurrence frequency of intraseasonal patterns,in which the change of the intraseasonal Kelvin wave plays an important role.