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Intraseasonal Oscillation in the Tropical Indian Ocean
LI Chongyin,HU Ruijin,YANG Hui,
LI Chongyin
,HU Ruijin,YANG Hui

大气科学进展 , 2005,
Abstract: The features of the intraseasonal oscillation (ISO) of the tropical Indian Ocean are studied using several sources of observational data. It is shown that there are intraseasonal oscillations in the tropical Indian Ocean, but their periods vary with latitude: the major period is about 20-30 days in the equatorial region, about 30-50 days at 10°N/10°S latitude and 60-90 days at 20°N/20°S latitude. The intensity of the ISO increases with latitude but the speed of the westward propagation of the ISO decreases with latitude. The intensity and propagation speed of the ISO have clear interannual variation features. The atmospheric intraseasonal oscillation over the tropical Indian Ocean is also analyzed and compared with the oceanic intraseasonal oscillation. It is shown that the major period is in the range 30-60 days and the intensity and period of the atmospheric ISO decrease with latitude slightly. The zonal propagation of the atmospheric ISO also has some differences with the oceanic ISO. It is necessary to study the relationship between the atmospheric ISO and oceanic ISO in the tropical Indian Ocean deeply.
Indian Ocean Dipole and El Ni o/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean  [PDF]
J. C. Currie,M. Lengaigne,J. Vialard,D. M. Kaplan
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-5841-2013
Abstract: The Indian Ocean Dipole (IOD) and the El Ni o-Southern Oscillation (ENSO) frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled bio-physical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely-sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997–1998 ENSO and IOD event. Results show that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. IOD depresses integrated chlorophyll in the 5° S–10° S thermocline ridge region, even though the signal is negligible in surface chlorophyll. A previously-unreported negative influence of IOD on chlorophyll concentrations is also shown in a region around the southern tip of India. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Lastly, we show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. ENSO and IOD cause significant and predictable regional re-organisation of phytoplankton productivity via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.
Intensified Eastward and Northward Propagation of Tropical Intraseasonal Oscillation over the Equatorial Indian Ocean in a Global Warming Scenario

YANG Jing,BAO Qing,WANG Xiaocong,

大气科学进展 , 2013,
Abstract: Northward propagation in summer and eastward propagation in winter are two distinguished features of tropical intraseasonal oscillation (TISO) over the equatorial Indian Ocean. According to numerical modeling results, under a global warming scenario, both propagations were intensified. The enhanced northward propagation in summer can be attributed to the enhanced atmosphere-ocean interaction and the strengthened mean southerly wind; and the intensified eastward propagation in winter is associated with the enhanced convection-wind coupling process and the strengthened equatorial Kevin wave. Future changes of TISO propagations need to be explored in more climate models.
The ISO Events in the Winter of 2007
LIU Lin,
LIU
,Lin

大气和海洋科学快报 , 2012,
Abstract: The intraseasonal oscillation (ISO) events that occurred from November 2007 to February 2008 in the tropical Indian Ocean region were investigated by analyzing observational oceanic and atmospheric datasets. The results reveal that two ISO events were generated and developed from November 2007 to February 2008 in the tropical area of the Indian Ocean, which both originated from the southern African continent and propagated along a northeastward direction and finally penetrated into the equatorial eastern Indian Ocean. Compared with the general winter MJO event, which tended to travel along the equator from the western Indian Ocean into the western Pacific, the ISO of winter 2007 propagated not only along the equator into the eastern part of the Indian Ocean but was also transported northward into the subtropical region in the eastern Indian Ocean, which is more similar to the behavior of traditional summer ISO events.
Southern and Tropical Indian Ocean SST: A Possible Predictor of Winter Monsoon Rainfall over South India  [PDF]
Ravi P. Shukla, Shailendra Rai, Avinash C. Pandey
Atmospheric and Climate Sciences (ACS) , 2013, DOI: 10.4236/acs.2013.34045
Abstract:

The complexities in the relationship between winter monsoon rainfall (WMR) over South India and Sea Surface temperature (SST) variability in the southern and tropical Indian Ocean (STIO) are evaluated statistically. The data of the time period of our study (1950-2003) have been divided exactly in two halves to identify predictors. Correlation analysis is done to see the effect of STIO SST variability on winter monsoon rainfall index (WMRI) for South India with a lead-lag of 8 seasons (two years). The significant positive correlation is found between Southern Indian Ocean (SIO) SST and WMRI in July-August-September season having a lag of one season. The SST of the SIO, Bay of Bengal and North Equatorial Indian Ocean are negatively correlated with WMRI at five, six and seven seasons before the onset of winter monsoon. The maximum positive correlation of 0.61 is found from the region south of 500 S having a lag of one season and the negative correlations of 0.60, 0.53 and 0.57 are found with the SST of the regions SIO, Bay of Bengal and North Equatorial Ocean having lags of five, six and seven seasons respectively and these correlation coefficients have confidence level of 99%. Based on the correlation analysis, we defined Antarctic Circumpolar Current Index A and B (ACCIA (A) & ACCIB (B)), Bay of Bengal index (BOBI (C)) and North Equatorial Index (NEI (D)) by averageing SST for the regions having maximum correlation (positive or negative) with WMRI index. These SST indices are used to predict the WMRI using linear and multivariate linear regression models. In addition, we also attempted to detect a dynamic link for the predictability of WMRI using Nino 3.4 index. The predictive skill of these indices is tested by error analysis and Willmott’s index.

MONSOON RAINFALL AND SOUTHERN OSCILLATION RESPONSES IN THE PRESSURES OVER THE NORTHERN INDIAN OCEAN

KD Prasad,SV Singh,

大气科学进展 , 1988,
Abstract: The pressure variations over the North Indian Ocean during the summer monsoon season have been exam-ined using the monthly data from June to September for the period 1961 to 1968. It is found that these varia-tions can be described by two significant eigenvectors (EV1 and EV2) which together account for 53% of the total variance.The first eigenvector (EV1) represents in phase variation over both, the Arabian Sea and the Bay of Bengal with higher variations over the northern side of the area. The second eigenvector (EV2) depicts the out-of-phase variation between the pressure anomalies over the north and the south of 15°N latitude with two areas of pronounced variation, viz., the head Bay of Bengal and the equatorial region near 65°E longitude.The coefficients of EV1 show significant association with rainfall of West Coast and Central India for the concurrent months. These coefficients also show significant association with the pressure and temperature indices of the Southern Oscillation. The coefficients of EV2 show significant association with the monsoon rainfall of south peninsular India.
Short-term Climatic Fluctuations in North Atlantic Oscillation and Frequency of Cyclonic Disturbances over North Indian Ocean and Northwest Pacific
Short-term Climatic Fluctuations in North Atlantic Oscillation and Frequency of Cyclonic Disturbances over North Indian Ocean and Northwest Pacific

S S Dugam,S B Kakade,
S. S. Dugam
,S. B. Kakade

大气科学进展 , 1995,
Abstract: A relationship between mean sea level pressure gradient between Azores High (AH) and Icelandic Low (IL) here after called North Atlantic Oscillation Index (NAOI) and the frequency of cyclonic disturbances over North Indian Ocean is investigated using 98 years of date (1891-1988). The analysis is carried out on monthly, seasonel, annual and decadal scales. Similar studies are also done for North West Pacific ocean cyclonic disturbances. It is noticed that the number of cyclonic disturbances over North Indian Ocean during monsoon season (June-September) as well as on annual scale is significantly correlated with NAOI, However for pre (April-May) and post (October-November-December) monsoon seasons frequency of cyclonic disturbances do not bear similar relationship with NAOI. The study also shows that decadal scale variability of cyclonic disturbances during the summer monsoon over North In-dian Ocean has a remarkable correspondence with the decadal variability of NAOI.
Causes of the Intraseasonal SST Variability in the Tropical Indian Ocean
Tim Li,Francis Tam,Xiouhua Fu,ZHOU Tian-Jun,ZHU Wei-Jun,
Tim Li
,Francis Tam,Xiouhua Fu,周天军,朱伟军

大气和海洋科学快报 , 2008,
Abstract: Satellite observations reveal a much stronger intraseasonal sea surface temperature (SST) variability in the southern Indian Ocean along 5-10oS in boreal winter than in boreal summer. The cause of this seasonal dependence is studied using a 2?-layer ocean model forced by ERA-40 reanalysis products during 1987-2001. The simulated winter-summer asymmetry of the SST variability is consistent with the observed. A mixed-layer heat budget is analyzed. Mean surface westerlies along the ITCZ (5-10oS) in December-January-February (DJF) leads to an increased (decreased) evaporation in the westerly (easterly) phase of the intraseasonal oscillation (ISO), during which convection is also enhanced (suppressed). Thus the anomalous shortwave radiation, latent heat flux and entrainment effects are all in phase and produce strong SST signals. During June-July-August (JJA), mean easterlies prevail south of the equator. Anomalies of the shortwave radiation tend to be out of phase to those of the latent heat flux and ocean entrainment. This mutual cancellation leads to a weak SST response in boreal summer. The resultant SST tendency is further diminished by a deeper mixed layer in JJA compared to that in DJF. The strong intraseasonal SST response in boreal winter may exert a delayed feedback to the subsequent opposite phase of ISO, implying a two-way air-sea interaction scenario on the intraseasonal timescale. Citation: Li, T., F. Tam, X. Fu, et al., 2008: Causes of the intraseasonal SST variability in the tropical Indian ocean, Atmos. Oceanic Sci. Lett., 1, 18-23
Possible Process for Influences of Winter and Spring Indian Ocean SST Anomalies Interannual Variability Mode on Summer Rainfall over Eastern China
冬季和春季印度洋海温异常年际变率模态对中国东部夏季降水的可能影响过程

XU Zhiqing,FAN Ke,
徐志清
,范可

大气科学 , 2012,
Abstract: The thermal conditions of the Indian Ocean is an important factor that can affect the global climate and Asian monsoon variability. Previous studies have paid much more attention to sea surface temperature (SST) variability in the tropical Indian Ocean than the middle-and high-latitude South Indian Ocean, which limits the overall understanding about the Indian Ocean. This study presents the leading mode of the Indian Ocean sea surface temperature anomalies (SSTA) on interannual time scale and the possible process for its influences on summer rainfall over eastern China, ex- pecting to provide a theoretic basis for climate variations research and prediction. The results indicate that the leading mode of the Indian Ocean SSTA on interannual time scale is characterized by southwest-northeast oriented dipole oscil- lation in the subtropical South Indian Ocean. The western pole is located in the southeast of Madagascar and the eastern pole lies in the west of Australia, varying consistently with the tropical Indian Ocean SSTA. Here, the positive (negative) Indian Ocean SSTA interannual variability mode is defined as positive (negative) SSTA in the western pole and negative (positive) SSTA in the eastern pole and the tropical Indian Ocean. The interannual variability mode, which can persist during winter and spring, is significantly negatively correlated with summer rainfall over the middle reach of the Yangtze River (MYR), but significantly positively correlated with rainfall over South China (SC). The possible mechanism can be described as follows: for positive Indian Ocean SSTA interannual variability mode events during winter and spring, the meridional atmospheric teleconnection of zonal wind anomalies in the Indian Ocean leads to westerly anomalies in the tropical Indian Ocean which depress the convective activities over the Maritime Continent in spring and summer. The depressed convective activities make the western Pacific subtropical high weaken and shift northward and eastward, conducing to increased rainfall over SC and reduced rainfall over MYR, and vice versa. Moreover, the Indian Ocean SSTA interannual variability mode can also influence summer rainfall over MYR by changing its water vapor transport stemming from the Indian Ocean and the Bay of Bengal.
Two sides of the same coin: extinctions and originations across the Atlantic/Indian Ocean boundary as consequences of the same climate oscillation
Peter R. Teske,Gerardo I. Zardi,Christopher D. McQuaid,Katy R. Nicastro
Frontiers of Biogeography , 2013,
Abstract: Global climate change is correlated not only with variation in extinction rates, but also with speciation rates. However, few mechanisms have been proposed to explain how climate change may have driven the emergence of new evolutionary lineages that eventually became distinct species. Here, we discuss a model of range extension followed by divergence, in which the same climate oscillations that resulted in the extinction of coastal species across the Atlantic/Indian Ocean boundary in southwestern Africa also sowed the seeds of new biodiversity. We present evidence for range extensions and evolutionary divergence from both fossil and genetic data, but also point out the many challenges to the model that need to be addressed before its validity can be accepted.
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