华北春季降水及其与前期印度洋海温的关系

利用华北17站1951-2002年春季（3-5月）逐月降水资料和NOAA再分析海表温度资料，研究了华北地区春季降水特征及其与海温的关系。得知华北春季降水偏少年出现频次比偏多年频次高，但是年际变化明显，强度没有偏多年严重。华北地区春季降水有一定的年代际变化和周期性，降水周期在20世纪70年代中期以前为4-6a，在70年代中期以后为6-8a。同时用相关分析方法找出了影响华北地区春季降水的海温关键区为印度洋，发现印度洋在前一年11月到当年1月存在一个相关系数较高海区。用SVD方法证实了前期冬季印度洋海温正是与华北春季降水相关最显著的时段和地区。并用合成分析初步得到印度洋海温异常强迫影响大气环流，并通过遥相关影响华北地区降水。     

印度洋海温异常与南亚高压东西振荡的关系

利用1952~2001年的印度洋海表温度资料、NCEP/NCAR的高度场资料,采用小波分析、交叉谱分析等方法,讨论了印度洋海温偶极子指数与南亚高压东西振荡的关系。结果表明:印度洋偶极子指数与南亚高压存在明显的负相关,且春季印度洋偶极子指数对同年夏季南亚高压的东西振荡有一定指示作用。印度洋偶极子指数与南亚高压东伸指数均存在8 a左右显著时间尺度。两者在1.5~8 a的周期上存在密切联系,在3 a左右的周期上,印度洋偶极子指数变化超前于南亚高压东伸指数,说明印度洋海温异常是影响南亚高压东西振荡的重要因素之一。     

太平洋-印度洋海表温度加热对中高纬低频振荡的调频作用

用数值试验的方法，分别以无热源型、El Nino初期、El Nino成熟期对应的赤道中东太平洋与赤道印度洋海表温度作为外强迫源，应用强迫耗散准地转正压涡度方程的全球谱模式，考虑了摩擦耗散及3波准共振的共同作用，采用非定常、定常加热两种形式积分90d，研究了对中高纬大气低频振荡的调频作用。结果表明：（1）3个行星波之间存在很强的波-波相互作用，且波动振荡呈现准双周和季节内振荡；（2）在El Nino初期和El Nino成熟期，无论是赤道中东太平洋海温还是赤道印度洋海温在逐渐增暖的过程中，大气低频振荡周期都有缩短的趋势。1997年2月-1997年4月，赤道印度洋调节作用强；而在1998年5月，赤道中东太平洋调节作用强；（3）赤道印度洋西区对大气低频振荡的调节作用要强于赤道印度洋东区；Nino3区对大气低频振荡的调节作用要强于Ninol＋2区；（4）太平洋-印度洋海温异常模态在1997年10月为高指数（简称PIMI一型），在1996年9月为低指数（简称PIMI二型），前者对应的东太平洋-西印度洋区对大气的调频作用要大于后者对应的西太平洋一东印度洋区。     

Interannual Variability of Sea Surface Temperature in the Northern Indian Ocean Associated with ENSO and IOD

The Northern Indian Ocean(NIO) sea surface temperature(SST) warming,associated with the El Ni o/Southern Oscillations(ENSO) and the Indian Ocean Dipole(IOD) mode,is investigated using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) monthly data for the period 1979 2010.Statistical analyses are used to identify respective contribution from ENSO and IOD.The results indicate that the first NIO SST warming in September November is associated with an IOD event,while the second NIO SST warming in spring-summer following the mature phase of ENSO is associated with an ENSO event.In the year that IOD co-occurred with ENSO,NIO SST warms twice,rising in the ENSO developing year and decay year.Both shortwave radiation and latent heat flux contribute to the NIO SST variation.The change in shortwave radiation is due to the change in cloudiness.A cloud-SST feedback plays an important role in NIO SST warming.The latent heat flux is related to the change in monsoonal wind.In the first NIO warming,the SST anomaly is mainly due to the change in the latent heat flux.In the second NIO warming,both factors are important.     

Variations of the Precipitation over the Three-River Headwaters Region Affected by the North Atlantic and Indian Ocean

Using the daily precipitation data from the global precipitation measurement (GPM) satellite and meteorological stations from 2001 to 2020, the present study has analyzed the seasonal and interannual spatial-temporal variations of the precipitation over the Three-River Headwaters region. The rainfall of the Three-River Headwaters region is verified to have obvious spatial-temporal variations and is mainly concentrated in summer. Then, the empirical orthogonal function (EOF) method is performed and reveals that the summer precipitation in the Three-River Headwaters region mainly shows three patterns, e.g., the “north?south dipole pattern,” “northeast?southwest diploe pattern,” and “east?west dipole pattern,” among which the northeast?southwest diploe pattern has a strong correlation with the mid-latitude westerlies and summer monsoon. Further analysis reveals that the northeast-southwest diploe pattern of summer precipitation is significantly related to the tripolar sea surface temperature (SST) anomalies (SSTAs) of the North Atlantic Ocean in the preceding winter and the tropical Indian Ocean SSTAs in the simultaneous summer. In the preceding winter, a wave-like pattern zonally propagating along the mid-latitude westerlies is triggered downstream by the North Atlantic tripolar SSTAs. One of the cyclones generated by the wave-like pattern coincidentally locates in Northeastern China and forms a deep northeastern low system in summer. Moreover, the warming of the tropical Indian Ocean SSTAs in summer weakens the Walker circulation, which leads to the strengthening and westward extension of the Western Pacific subtropical high (WPSH). Northerly anomalies from the deep northeastern cyclonic anomalies and southwesterly anomalies from the enhancing WPSH exactly met at the eastern Three-River Headwaters region. Hence, more water vapor and ascending motion anomalies likely appear over the east part of the Three-River Headwaters region. Opposite anomalies cover the south- western Three-River Headwaters region and its surroundings. Then, the northeast-southwest reverse diploe pattern of the summer rainfall in the Three-River Headwaters region is directly produced.     

热带太平洋与印度洋相互作用的年代际变化

利用全球海表海温资料（GISST）和NCEP／NCAR再分析资料,研究了热带太平洋与印度洋之间的相互作用及其在不同年代二者作用关系的变化。结果表明：热带印度洋偶板子指数超前热带太平洋Nin03指数2月时相关最大,印度洋单板子指数滞后Nin03指数3～4月时相关最大。印度洋偶板子在一定程度上影响E1 Nino事件的发生,而E1 Nino事件的发生、发展会影响印度洋单板子事件的发生。热带印度洋偶板子事件与热带太平洋ENSO事件的相互作用在1961年发生了明显跃变,其原因可能是1961年之前热带印度洋偶板子对热带太平洋上空的纬向风影响很小,而1961年以后其影响明显加强。热带印度洋单板子事件与热带太平洋ENSO事件的相关一直显著,没有明显跃变。     

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。     

印度洋偶极子与中国秋季降水的关系

利用1950--1999年Hadley中心全球海温资料、NCEP／NCAR再分析资料以及国家气象局整编的160站降水资料，分析讨论了夏季印度洋偶极子与中国秋季降水的时滞关系及秋季印度洋偶极子与同期中国降水的关系。结果表明：夏、秋季印度洋偶极子均与中国南方秋季降水有很好的正相关关系；通过对印度洋偶极子时期秋季异常环流场特征分析，发现正偶极子时期中国西南部受中层槽前西南气流影响，带来充足水汽，同时低层为异常气旋性环流控制，使该地区降水增加。     

南印度洋偶极子的变化特征及其与ENSO的关系

利用近三十年逐月的OISST和ERSST资料、NCEP2表面风场等资料和数据分析了南印度洋偶极子的形成原因、结构特征.结果表明：南印度洋偶极子形态的年际SST异常出现在10-12月,有两个明显的冷暖中心,达到极值是在次年的2月份,然后在4-5月份消亡;南印度洋偶极子的形成主要是风场、潜热通量起作用,另外,短波辐射通量也对其有重要的影响;SIOD在北半球春冬季出现,达到盛期是在次年的二月份或三月份,超前ENSO9-10个月,且具有季节锁相特征,在70年代中期的年代际气候突变后,SIOD与ENSO的关系显著增强.     

Relationship Between Upper-Ocean Heat Content in the Tropical Indian Ocean and Summer Precipitation in China

An analysis of the Ishii ocean heat content(OHC) in the tropical Indian Ocean from the surface to 700-m depth shows that the OHC changes dramatically on the interannual timescale in the Indian Ocean.The first mode of empirical orthogonal function(EOF1) of the OHC shows that there is a strong air-sea interaction pattern in the Indian Ocean with a positive(negative) loading in the east and a negative(positive) loading in the west.This seesaw oscillation pattern influences the summer precipitation in China with a North-South reversed distribution.Composite analysis shows that during a positive(negative) OHC episode,an anomalous cyclonic(anticyclonic) circulation over the western Pacific and South China weakens(enhances) the monsoonal northward flow in the lower troposphere;meanwhile,anomalous meridional circulation connects the descending(ascending) branch over the Southeast Indian Ocean and the ascending(descending) branch in South China as well as a descending(ascending) branch over North China.Analysis of the mechanism behind these features suggests that(1) the accumulation of OHC-induced vorticity is related to the wave activity over the mid-latitudes and that(2) the meridional teleconnection induced by the Indo-Pacific air-OHC interaction appears over East Asia and the western Pacific.Both of these patterns can cause summer precipitation anomalies in China.     

印度洋海温的偶极振荡与高原汛期降水和温度的关系

利用1961—2000年近40年印度洋海温距平场资料及对应的青藏高原35个观测站的降水与温度资料,通过相关普查得出,印度洋地区东西海温的偶极振荡与青藏高原汛期降水、温度有较好的相关关系,特别是前期1月、12月～2月的印度洋地区东西海温的偶极指数与青藏高原汛期(6～8月)降水和前一年6月的印度洋地区东西海温的偶极指数与青藏高原汛期(6～8月)温度有很好的相关。分析1961—2002年NCEP／NCAR 500hPa北半球高度场资料发现,印度洋地区东西海温的偶极指数与欧亚500hPa的高度场异常有密切的关系,并通过印度西南季风的强弱,影响到青藏高原汛期降水和温度的变化。     

印度洋海温异常和南海夏季风建立迟早的关系I.耦合分析

运用CSVD和联合CSVD等较新颖的统计方法,在去除/未去除ENSO影响的思路下,探讨了印度洋海温异常和南海夏季风建立迟早的关系,结果表明:在没有去除ENSO信号(外部作用)影响的情况下,全区一致型的海温异常分布对南海夏季风建立迟早起着重要的作用。当全区温度距平为正(负)时,南海夏季风建立较晚(早)。在去除了ENSO信号的影响后,非ENSO全区一致型和SIODM型是影响南海夏季风建立早晚的两个主要的印度洋海温分布型。对于非ENSO全区一致型的海温分布,当前期海温全区为负(正)距平时,南海夏季风建立较早(晚)。而对于SIODM型的海温分布,则当前期海温距平为西负东正(西正东负)的SIODM型时,南海夏季风建立较早(晚)。     

Intercomparison of Surface Radiative Fluxes in the Arctic Ocean

Recent satellite data analysis has provided improved data sets relevant to the surface energy budget in the Arctic Ocean. In this paper, surface radiation properties in the Arctic Ocean obtained from the Surface Radiation Budget（SRB3.0） and the International Satellite Cloud Climatology Project（ISCCP-FD） during 1984– 2007 are analyzed and compared. Our analysis suggests that these datasets show encouraging agreement in basin-wide averaged seasonal cycle and spatial distribution of surface albedo; net surface shortwave and all-wave radiative fluxes; and shortwave, longwave, and all-wave cloud radiative forcings. However, a systematic large discrepancy is detected for the net surface longwave radiative flux between the two data sets at a magnitude of ~ 23 W m–2, which is primarily attributed to significant differences in surface temperature, particularly from April to June. Moreover, the largest difference in surface shortwave and all-wave cloud radiative forcings between the two data sets is apparent in early June at a magnitude of 30 W m–2.     

青藏高原气温与印度洋海温遥相关的初步研究

利用1960—2000年青藏高原54个常规气象观测站的年平均地面气温资料,考察了高原气温的空间分布和气候变异特征;利用同期印度洋海温资料和奇异值分解方法,着重研究了青藏高原气温与印度洋海温之间的遥相关关系,并初步探讨了物理机制问题。分析结果表明:在空间分布上,青藏高原气温中部低,四周高,41年来呈逐步上升趋势,振幅不断加大;高原气温与印度洋海温之间存在显著的主要遥相关模态,这与印度洋海温异常激发遥相关波列影响到高原气温有关。     

夏季北印度洋海温异常对西北太平洋低层反气旋异常的影响

采用1957—2002年850 hPa风场的ERA-40再分析资料,分析得知西北太平洋低层环流存在着明显的年际变化。这种年际变化表征了西北太平洋夏季风的年际变化,并且会影响东亚夏季风的变化。用Hadley海表面气压以及海表温度资料诊断得到,这种夏季西北太平洋反气旋异常（WPAC,northwest Pacific anomalous anticyclone）的年际变化与北印度洋同期海表温度变化存在很好的相关。用偏相关方法消除N ino3.4信号的同期线性影响,这种同期相关更加显著,而西南热带印度洋的同期海温与WPAC的相关并不显著。数值试验结果表明,北印度洋存在正海温异常时,北印度洋降水偏多,同时伴随着西北太平洋反气旋异常。当只有西南热带印度洋有正海温异常时,北印度洋会出现东风异常且降水减少,而西北太平洋有弱的气旋异常。数值模式结果与观测数据的诊断结果相吻合,说明当夏季北印度洋海表温度为正异常时,可能会产生西北太平洋反气旋异常。     

Summertime Seawater Concentrations of Dimethylsulfide in the Western Indian Ocean: Reconciliation of Fluxes and Spatial Variability with Long-Term Atmospheric Observations

Dimethylsulfide (DMS) measurements in the seawater of the subtropical and the temperate western Indian Ocean were conducted for the first time from 3 December to 20 December 1997. In total, 443 surface seawater DMS determinations were performed between 24°–49° S and 50° E–77° E with a frequency of 1 sample every 10 km. An important spatial variability was observed in seawater DMS concentrations with values ranging from 0.9 to 35.8 nM. DMS maxima coincided in most cases with thermal fronts and were in reasonable agreement with mean pigment figures obtained from satellite observations. The deduced DMS fluxes are consistent with long-term observations of atmospheric DMS and rainwater concentrations of nss- SO4= and MSA measured at Amsterdam island (37° S, 77° E); then account for the differences observed in atmospheric DMS concentrations between Amsterdam island and Cape Grim, Indian Ocean monitoring stations.     

印度洋海温异常和南海夏季风建立迟早的关系 II.机理分析

通过区分ENSO外部影响和偶极子内部局地作用,探讨了前期春季的印度洋海温异常对南海夏季风建立早晚的可能影响途径。结果表明:在没有去除ENSO信号(外部作用)的情况下,全区一致型的海温分布主要通过影响热带印度洋上空纬向季风环流的强弱来影响南海夏季风建立的早晚。去除ENSO信号后,非ENSO全区一致型的海温分布则主要通过影响低层东西向的气压差异和对流层中上层的南北温度梯度的逆转,进而对南海夏季风建立的早晚产生影响;而南印度洋偶极子(SIODM)型的海温分布则主要通过影响亚洲大陆热低压、西太平洋副热带高压和高低层的辐合辐散运动影响南海夏季风的建立。     

Warming in the Northwestern Indian Ocean Associated with the El Ni(n)o Event

This paper investigates possible warming effects of an El Ni(n)o event on the sea surface temperature anomaly(SSTA)in the northwestern Indian Ocean.Most pure positive Indian Ocean dipole(IOD)events (without an El Ni(n)o event co-occurring) have a maximum positive SSTA mainly in the central Indian Ocean south of the equator.while most co-occurrences with an El Ni(n)o event exhibit a northwest-southeast typical dipole mode.It is therefore inferred that warming in the northwestern Indian Ocean is closely related to the El Ni(n)o event.Based on the atmospheric bridge theory,warming in the northwestern Indian Ocean during co-occurring cases may be primarily caused by relatively less latent heat loss from the ocean due to reduced wind speed.The deepened thermocline also contributes to the warming along the east coast of Africa through the suppressed upwelling of the cold water.Therefore,the El Ni(n)o event is suggested to have a modulating effect on the structure of the dipole mode in the tropical Indian Ocean.     

The Kelvin Wave Processes in the Equatorial Indian Ocean during the 2006–2008 IOD Events

The present study investigates the role of Kelvin wave propagations along the equatorial Indian Ocean during the 2006–2008 Indian Ocean Dipole (IOD). The 2006 IOD lasted for seven months, developing in May and reaching its peak in December, while the 2007 and 2008 IODs were short-lived events, beginning in early May and ending abruptly in September, with much weaker amplitudes. Associated with the above IODs, the impulses of the sea surface height (SSH) anomalies reflect the forcing from an intraseasonal time scale, which was important to the evolution of IODs in 2007 and 2008. At the thermocline depth, dominated by the propagation of Kelvin waves, the warming/cooling temperature signals could reach the surface at a particular time. When the force is strong and the local thermocline condition is favorable, the incoming Kelvin waves dramatically impact the sea surface temperature (SST) in the eastern equatorial Indian Ocean. In July 2007 and late July 2008, the downwelling Kelvin waves, triggered by the Madden-Julian Oscillation (MJO) in the eastern and central equatorial Indian Ocean, suppressed the thermocline in the Sumatra and the Java coast and terminated the IOD, which made those events short-lived and no longer persist into the boreal fall season as the canonical IOD does.     

The Role of the Aerosol Indirect Effect in the Northern Indian Ocean Warming Simulated by CMIP5 Models

The northern Indian Ocean （NIO） experienced a decadal-scale persistent warming from 1950 to 2000, which has influenced both regional and global climate. Because the NIO is a region susceptible to aerosols emis- sion changes, and there are still large uncertainties in the representation of the aerosol indirect effect （ALE） in CMIP5 （Coupled Model Intercomparison Project Phase 5） models, it is necessary to investigate the role of the AIE in the NIO warming simulated by these models. In this study, the authors select seven CMIP5 models with both the aerosol direct and indirect effects to investigate their performance in simulating the basin-wide decadal-scale NIO warming. The results show that the decreasing trend of the downwelling shortwave flux （FSDS） at the surface has the major damping effect on the SST increasing trend, which counteracts the warming effect of greenhouse gases （GHGs）. The FSDS decreasing trend is mostly contrib- uted by the decreasing trend of cloudy-sky surface downwelling shortwave flux （FSDSCL）, a metric used to measure the strength of the AIE, and partly by the clear-sky surface downwelling shortwave flux （FSDSC）. Models with a relatively weaker AIE can simulate well the SST increasing trend, as compared to observation. In contrast, models with a relatively stronger AIE produce a much smaller magnitude of the increasing trend, indicat- ing that the strength of the AIE in these models may be overestimated in the NIO.