North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?

The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.     

Relationships between the North Pacific Oscillation and the typhoon/hurricane frequencies

Relationships between the North Pacific Oscillation (NPO) and the typhoon as well as hurricane fre-quencies are documented. The correlation between NPO index in June-July-August-September and the annual typhoon number in the western North Pacific is 0.37 for the period of 1949―1998. The NPO is correlated with the annual hurricane number in the tropical Atlantic at -0.28 for the same period. The variability of NPO is found to be concurrent with the changes of the magnitude of vertical zonal wind shear, sea-level pressure patterns, as well as the sea surface temperature, which are physically asso- ciated with the typhoons and hurricanes genesis. The NPO associated atmospheric circulation vari- ability is analyzed to explain how NPO is linked with variability of the tropical atmospheric circulation in the western Pacific and the tropical Atlantic, via the atmospheric teleconnection.     

The 20–30-day oscillation of the global circulation and heavy precipitation over the lower reaches of the Yangtze River valley

Based on the observational data in summer, the variations of intraseasonal oscillation (ISO) of the daily rainfall over the lower reaches of the Yangtze River valley (LYRV) were studied by using the non-integer spectrum analysis. The NCEP/NCAR reanalysis data for the period of 1979–2005 were analyzed by principal oscillation pattern analysis (POP) to investigate the spatial and temporal characteristics of principal ISO patterns of the global circulation. The relationships of these ISO patterns to the rainfall ISO and the heavy precipitation process over LYRV were also discussed. It is found that the rainfall over LYRV in May–August is mainly of periodic oscillations of 10–20, 20–30 and 60–70 days, and the interannual variation of the intensity of its 20–30-day oscillation has a strongly positive correlation with the number of the heavy precipitation process. Two modes (POP1, POP2) are revealed by POP for the 20–30-day oscillation of the global 850 hPa geopotential height. One is a circumglobal teleconnection wave train in the middle latitude of the Southern Hemisphere (SCGT) with an eastward propagation, and the other is the southward propagation pattern in the tropical western Pacific (TWP). The POP modes explain 7.72% and 7.66% of the variance, respectively. These two principal ISO patterns are closely linked to the low frequency rainfall and heavy precipitation process over LYRV, in which the probability for the heavy precipitation process over LYRV is 54.9% and 60.4% for the positive phase of the imaginary part of POP1 and real part of POP2, respectively. Furthermore, the models of the global atmospheric circulation for the 20–30-day oscillation in association with or without the heavy precipitation process over LYRV during the Northern Hemisphere summer are set up by means of the composite analysis method. Most of the heavy precipitation processes over LYRV appear in Phase 4 of SCGT or Phase 6 of TWP. When the positive phases of 20–30-day oscillations for the rainfall over LYRV are associated with (without) the heavy precipitation process, a strong westerly stream appears (disappears) from the Arabian Sea via India and Bay of Bengal (BOB) to southern China and LYRV for the global 850 hPa filtered wind field during Phase 4 of SCGT. This situation is favorable (unfavorable) for the forming of the heavy precipitation process over LYRV. Similarly, a strong (weak) western wind belt forms from India through BOB to southern China and LYRV and the subtropical northwestern Pacific and central and eastern equatorial Pacific during Phase 6 of TWP for the cases with (without) the heavy precipitation process. The evolutions of these ISO patterns related to the 20–30-day oscillation are excited by either the interaction of extratropical circulation in both hemispheres or the heat source forcing in Asia monsoon domain and internal interaction of circulation in East Asia. These two global circulation models might therefore provide valuable information for the extended-range forecastof the heavy precipitation process over LYRV during the 10–30 days.     

Dynamical effect of the zonal wind anomalies over the tropical western Pacific on ENSO cycles

The circulation and zonal wind anomalies in the lower troposphere over the equatorial western Pacific and their roles in the developing and decaying processes of the 1982–1983, 1986 –1987, 1991–1992 and 1997–1998 El Ni?o events and the occurrence of La Ni?a events are analyzed by using the observed data in this paper. The results show that before the developing stage of these El Ni?o events, there were cyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies brought the westerly anomalies over the Indonesia and the tropical western Pacific. However, when the El Ni?o events developed to their mature phase, there were anticyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies made the easterly anomalies appear over the tropical western Pacific. A simple, dynamical model of tropical ocean is used to calculate the response of the equatorial oceanic waves to the observed anomalies of wind stress near the sea surface of the equatorial Pacific during the 1997/98 ENSO cycle, which was the strongest one in the 20th century. It is shown that the zonal wind stress anomalies have an important dynamical effect on the devel-opment and decay of this El Ni?o event and the occurrence of the following La Ni?a event.     

Interdecadal change of the linkage between the North Atlantic Oscillation and the tropical cyclone frequency over the western North Pacific

The relationship between the North Atlantic Oscillation(NAO) and the tropical cyclone frequency over the western North Pacific(WNPTCF) in summer is investigated by use of observation data. It is found that their linkage appears to have an interdecadal change from weak connection to strong connection. During the period of 1948–1977, the NAO was insignificantly correlated to the WNPTCF. However, during the period of 1980–2009, they were significantly correlated with stronger(weaker) NAO corresponding to more(fewer) tropical cyclones in the western North Pacific. The possible reason for such a different relationship between the NAO and the WNPTCF during the former and latter periods is further analyzed from the perspective of large-scale atmospheric circulations. When the NAO was stronger than normal in the latter period, an anomalous cyclonic circulation prevailed in the lower troposphere of the western North Pacific and the monsoon trough was intensified, concurrent with the eastward-shifting western Pacific subtropical high as well as anomalous low-level convergence and high-level divergence over the western North Pacific. These conditions favor the genesis and development of tropical cyclones, and thus more tropical cyclones appeared over the western North Pacific. In contrast, in the former period, the impact of the NAO on the aforementioned atmospheric circulations became insignificant, thereby weakening its linkage to the WNPTCF. Further study shows that the change of the wave activity flux associated with the NAO during the former and latter periods may account for such an interdecadal shift of the NAO–WNPTCF relationship.     

East Asia Winter Monsoon changes inferred from environmentally sensitive grain-size component records during the last 2300 years in mud area southwest off Cheju Island,ECS

The last 2000 years are an important time span both for IGBP-PAGES and CLIVAR of WCRP. One of the main aims of these projects is to obtain high-resolution records of global change, such as that stored in ice cores, tree rings, speleothems, corals, lakes, marine records, etc., and then use these data to make sound estimates for future global change. To accomplish these projects, we first need to obtain high-resolution geological records and proxies for climatic/environ- mental changes. …     

Two modes of dipole events in tropical Indian Ocean

By analyzing the distributions of subsurface temperature and the surface wind stress anomalies in the tropical Pacific and Indian Oceans during the Indian Ocean Dipole (IOD) events, two major modes of the IOD and their formation mechanisms are revealed. (1) The subsurface temperature anomaly (STA) in the tropical Indian Ocean during the IOD events can be described as a “<” -shaped and west-east-oriented dipole pattern; in the east side of the “<” pattern, a notable tongue-like STA extends westward along the equator in the tropical eastern Indian Ocean; while in the west side of the “<” pattern, the STA has opposite sign with two centers (the southern one is stronger than the northern one in intensity) being of rough symmetry about the equator in the tropical mid-western Indian Ocean. (2) The IOD events are composed of two modes, which have similar spatial pattern but different temporal variabilities due to the large scale air-sea interactions within two independent systems. The first mode of the IOD event originates from the air-sea interaction on a scale of the tropical Pacific-Indian Ocean and coexists with ENSO. The second mode originates from the air-sea interaction on a scale of the tropical Indian Ocean and is closely associated with changes in the position and intensity of the Mascarene high pressure. The strong IOD event occurs when the two modes are in phase, and the IOD event weakens or disappears when the two modes are out of phase. Besides, the IOD events are normally strong when either of the two modes is strong. (3) The IOD event is caused by the abnormal wind stress forcing over the tropical Indian Ocean, which results in vertical transports, leading to the upwelling and pileup of seawater. This is the main dynamic processes resulting in the STA. When the anomalous easterly exists over the equatorial Indian Ocean, the cold waters upwell in the tropical eastern Indian Ocean while the warm waters pileup in the tropical western Indian Ocean, hence the thermocline in the tropical Indian Ocean is shallowed in the east and deepened in the west. The off-equator component due to the Coriolis force in the equatorial area causes the upwelling of cold waters and the shallowing of the equatorial India Ocean thermocline. On the other hand, the anomalous anticyclonic circulations and their curl fields located on both sides of the equator, cause the pileup of warm waters in the central area of their curl fields and the deepening of the equatorial Indian Ocean thermocline off the equator. The above three factors lead to the occurrence of positive phase IOD events. When anomalous westerly dominates over the tropical Indian Ocean, the dynamic processes are reversed, and the negative-phase IOD event occurs. Supported by National Natural Science Foundation of China (Grant No. 40776013), National Basic Research Program of China (Grant No. 2006CB403601) and the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KZCX-SW-222)     

海南井水位对热带气旋响应特征分析

2001——2010年, 海南省地下流体观测台网记录到多次热带气旋引起的井水位抖动现象．本文以2003年7月21日强热带气旋ldquo;天鹅rdquo;和2005年9月27日台风ldquo;达维rdquo;为例, 系统地研究了这两次热带气旋引起的水位抖动变化的特征．结果表明, 经过高通滤波, 水位抖动变化图像更加明显;通过频谱分析,得知热带气旋引起的水位抖动周期为100——101 min;井水位抖动的起始时间、 幅度最大值的时间与热带气旋通过海南岛陆的时间一致, 且与热带气旋的结构特点、发展和运动过程密切相关,与井孔自身的井-含水层系统对微动态信息响应的能力也有关系．分析认为,气压振荡式升降变化和摩擦是热带气旋引起水位抖动的原因．      

Tropical cyclones as a possible factor affecting seismic activity in the cyclonic zone of the northwestern Pacific

A possible influence of tropical cyclones on seismic activity in the cyclonic zone of the northwestern Pacific is considered. There is no direct and sufficiently reliable method for calculating the degree of impact of tropical cyclones on the Earth’s crust. Therefore, a sort of inverse problem is solved in the investigation: a possible qualitative influence of tropical cyclones on seismic activity is estimated from its intra-annual dynamics. It is established that for territories of the cyclonic zone, the intra-annual dynamics of cyclonic and seismic activities are similar. Low monthly mean values of the cyclonic and seismic energies are attained in July–October, whereas in the continental territories under consideration (Central Asia), the seismic activity is higher in January–March. The results obtained suggest that cyclones can affect the seismic regime in the cyclonic zone of the northwestern Pacific.     

The Preferred Structure of the Interannual Indian Monsoon Variability

The leading empirical orthogonal function (EOF) of the June-Sept. mean, rotational horizontal wind at 850 hPa and 200 hPa (over the region 12.5°S–42.5°N, 50°E–100°E) from 56 years (1948–2003) of reanalysis (from the National Centers for Environmental Prediction) shows strong anti-cyclonic circulation at upper levels, strong Indian Ocean cross-equatorial flow and on-shore flow over western India at lower levels . The associated principal component (PC) is correlated at the 0.75 level with the seasonal mean observed Indian Monsoon rainfall (IMR). Composite differences of vertically integrated divergence (surface to 800 hPa) and vorticity (surface to 500 hPa) between ``strong' years (PC-1 exceeds one standard deviation σ) and ``weak' years (PC-1 less than − σ) suggest increased rising motion and storminess over the Bay of Bengal and central India. Composite difference maps of station rainfall from the India Meteorological Department (IMD) between strong years and normal years (weak years and normal years) are statistically significant over central India, with strong (weak) years associated with increased (decreased) precipitation. In both cases the maps of rainfall anomalies are of one sign throughout India. The correlation of PC-1 with global seasonal mean SST is strong and negative over the eastern equatorial Pacific, but positive in a surrounding horse-shoe like region. Significant negative correlation occurs in the northwestern Indian Ocean. The lag/lead correlation between the NINO3 SST index and PC-1 is similar to but stronger than the NINO3/IMR correlation. Modest (but significant) negative correlation is seen when NINO3 leads PC-1 (or IMR) by one-two months. Strong negative correlation is seen when PC-1 (or IMR) leads NINO3. The projections of running five-day means of horizontal rotational winds at 850 and 200 hPa onto EOF-1 (after removing the seasonal mean for each year) were pooled for strong, normal and weak years. The strong and normal year probability distribution functions (pdfs) are nearly indistinguishable, but the weak year pdf has more weight for moderate negative values and in both extreme tails and shows some hint of bi-modality.     

27.3-day and 13.6-day atmospheric tide

An analysis of time variations in the earth's length of day (LOD) for 25 years (1973-1998) versus at- mospheric circulation changes and lunar phase is presented. It is found that, on the average, there is a 27.3-day and 13.6-day period oscillation in global zonal wind speed, atmospheric geopotential height, and LOD following alternating changes in lunar phase. Every 5-9 days (6.8 days on average), the fields of global atmospheric zonal wind and geopotential height and LOD undergo a sudden change in rela- tion to a change in lunar declination. The observed atmospheric oscillation with this time period may be viewed as a type of atmospheric tide. Ten atmospheric tidal cases have been analyzed by comparing changes in LOD, global zonal wind speed and atmospheric geopotential height versus change in lunar declination. Taken together these cases reveal prominent 27.3-day and 13.6-day tides. The lunar forcing on the earth's atmosphere is great and obvious changes occur in global fields of zonal wind speed and atmospheric geopotential height over the equatorial and low latitude areas. The driving force for the 27.3-day and 13.6-day atmospheric tides is the periodic change in lunar forcing during the moon's revolution around the earth. When the moon is located on the celestial equator the lunar declination equals zero and the lunar tidal forcing on the atmosphere reaches its maximum, at this time the global zonal wind speed increases and the earth's rotation rate decreases and LOD increases. Conversely, when the moon reaches its most northern or southern positions the lunar declination is maximized, lunar tidal forcing decreases, global zonal wind speed decreases, earth's rotation rate increases and LOD decreases. 27.3-day and 13.6-day period atmospheric tides deserve deeper study. Lunar tidal forcing should be considered in models of atmospheric circulation and in short and medium range weather forecasting.     

Study of spatial and temporal structure of long-term effects of solar activity and cosmic ray variations on the lower atmosphere circulation

The spatial and temporal structure of the effects of solar activity (SA) and galactic cosmic ray (GCR) flux variations on the lower atmosphere circulation has been studied based on NCEP/NCAR reanalysis archive for 1948–2006 and MSLP (Climatic Research Unit, UK) data for 1873–2000. It has been shown that the GCR effects on pressure variations are characterized by a strong latitudinal and regional dependence, which is determined by specific features of the tropospheric circulation in the studied regions. The distribution of the correlation coefficients for mean yearly values of atmospheric pressure with the GCR flux intensity is closely related to the position of the main climatological fronts. The periodic (∼60 years) changes in the correlation sign of the pressure at high and middle latitudes with Wolf numbers have been revealed. It has been suggested that the changes of the sign of SA/GCR effects on atmospheric pressure are caused by the changes of the macrocirculation epochs, which, in turn, may be related to large-scale processes on the Sun.     

南海夏季风爆发与南大洋海温变化之间的联系

利用1979-2009年NCEP第二套大气再分析资料和ERSST海温资料,分析南海夏季风爆发时间的年际和年代际变化特征,考察南海夏季风爆发早晚与南大洋海温之间的联系.主要结果为:(1)南海夏季风爆发时间年际和年代际变化明显,1979-1993年与1994-2009年前后两个阶段爆发时间存在阶段性突变;(2)南海夏季风爆发时间与前期冬季(12-1月)印度洋-南大洋(0-80°E,75°S-50°S)海温、春季(2-3月)太平洋-南大洋(170°E -80°W,75°S-50°S)海温都存在正相关关系,当前期冬、春季南大洋海温偏低(高)时,南海夏季风爆发偏早(晚).南大洋海温信号,无论是年际还是年代际变化,都对南海夏季风爆发具有一定的预测指示作用;(3)南大洋海温异常通过海气相互作用和大气遥相关影响南海夏季风爆发的迟早.当南大洋海温异常偏低(偏高)时,冬季南极涛动偏强(偏弱),同时通过遥相关作用使热带印度洋-西太平洋地区位势高度偏低(偏高)、纬向风加强(减弱),热带大气这种环流异常一直维持到春季4、5月份,位势高度和纬向风异常范围逐步向北扩展并伴随索马里越赤道气流的加强(减弱),从而为南海夏季风爆发偏早(偏晚)提供有利的环流条件.初步分析认为,热带大气环流对南大洋海气相互作用的遥响应与半球际大气质量重新分布引起的南北涛动有关.     

Climatic features of atmospheric heat source/sink over the Qinghai-Xizang Plateau in 35 years and its relation to rainfall in China

Using the 1961–1995 monthly averaged meteorological data from 148 surface stations in the Qinghai-Xizang Plateau (QXP) and its surrounding areas, calculation of the 35-year atmospheric heat source/sink (<Qi>) and an analysis on its climatic features and relation to rainfall in China have been made. It is found that on the average, the atmospheric heat source over the QXP is the strongest in June (78 W / m²) and cold source is the strongest in December (−72 W/m²). The sensible heat of the surface increases remarkably over the southwest of the QXP, causing the obvious increase of <Qi> there in February and March, which makes a center of the atmospheric heat source appear over the north slope of the Himalayas. Afterwards, this center continues to intensify and experiences noticeable migration westwards twice, separately occurring in April and June. The time when the atmosphere over the east of the QXP becomes heat source and reaches strongest is one month later than that over the southwest of the QXP. In summer, the latent heat of condensation becomes a heating factor as important as the sensible heat and is also a main factor that makes the atmospheric heat source over the east of the QXP continue growing. On the interdecadal time scale, (Q₁) of the QXP shows an abrupt change in 1977 and a remarkable increase after 1977. The atmospheric heat source of the spring over the QXP is a good indicator for the subsequent summer rainfall over the valleys of the Changjiang and Huaihe rivers and South China and North China. There is remarkable positive correlation between the QXP heat source of summer and the summer rainfall in the valleys of the Changjiang River.     

Multi-scale variability of the tropical Indian Ocean circulation system revealed by recent observations

The tropical Indian Ocean circulation system includes the equatorial and near-equatorial circulations, the marginal sea circulation, and eddies. The dynamic processes of these circulation systems show significant multi-scale variability associated with the Indian Monsoon and the Indian Ocean dipole. This paper summarizes the research progress over recent years on the tropical Indian Ocean circulation system based on the large-scale hydrological observations and numerical simulations by the South China Sea Institute of Oceanology(SCSIO), Chinese Academy of Sciences. Results show that:(1) the wind-driven Kelvin and Rossby waves and eastern boundary-reflected Rossby waves regulate the formation and evolution of the Equatorial Undercurrent and the Equatorial Intermediate Current;(2) the equatorial wind-driven dynamics are the main factor controlling the inter-annual variability of the thermocline in the eastern Indian Ocean upwelling;(3) the equatorial waves transport large amounts of energy into the Bay of Bengal in forms of coastal Kelvin and reflected free Rossby waves. Several unresolved issues within the tropical Indian Ocean are discussed:(i) the potential effects of the momentum balance and the basin resonance on the variability of the equatorial circulation system, and(ii) the potential contribution of wind-driven dynamics to the life cycle of the eastern Indian Ocean upwelling. This paper also briefly introduces the international Indian Ocean investigation project of the SCSIO, which will advance the study of the multi-scale variability of the tropical Indian Ocean circulation system, and provide a theoretical and data basis to support marine environmental security for the countries around the Maritime Silk Road.     

A Study of Mean Winter Circulation Characteristics and Energetics over Southeastern Asia

A mean climatology is studied to examine atmospheric circulation characteristics to assess the wintertime (December, January, February and March - DJFM) synoptic weather system affecting northern India. The main objective is to study the mean circulation and mean energetics distribution pertaining to the winter season, which are embedded with an eastward moving synoptic weather system in westerlies, called Western Disturbances (WDs). Forty years (1958–1997) of uninitialized daily re-analysis data of the National Center for Environmental Prediction - National Center for Atmospheric Research (NCEP- NCAR, henceafter NCEP), U.S. has been considered for this study. Winter circulations are considered over the domain 15°S–45°N and 30°E–120°E. This domain is considered particularly to illustrate the impact of wintertime synoptic weather system Western Disturbances (WDs), which travel towards the east over the western Himalayas during winter and yield an enormous amount of precipitation in the form of snow. Large-scale balances of kinetic energy, vorticity, angular momentum, heat and moisture budget terms are analyzed. The main findings of the study show that strong rising motion in the extratropical region brings a significant amount of precipitation over the region of study. Also, horizontal flux of kinetic energy converges in the tropical region and diverges over the extratropical region. It is seen that both the zonal and meridional component of kinetic energy contributes to the production of kinetic energy in the upper troposphere. Vorticity budget shows that wintertime circulation over the western Himalayas is characterized by a negative generation of vorticity. The relative and planetary vorticity advection contributes to the horizontal transport of vorticity. The moisture flux transported into the region shows that in the middle tropospheric levels moisture undergoes phase transformation due to turbulent exchange and hence releases latent heat.     

Forecasting the summer rainfall in North China using the year-to-year increment approach

A new approach to forecasting the year-to-year increment of rainfall in North China in July–August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North China in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965–1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North China. The prediction model makes a hindcast for 2000–2007, with an average relative root mean square error of 21% for the percentage of precipitation rate anomaly over North China. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North China during 1965–2006. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%–70%, it has been more difficult to forecast the summer rainfall over North China. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation. Supported by National Basic Research Program of China (Grant No. 2009CB421406), National Natural Science Foundation of China (Grant Nos. 40631005, 40775049) and Excellent Ph. D Dissertation in Chinese Academy of Sciences     

Basin‐scale stream‐flow forecasting using the information of large‐scale atmospheric circulation phenomena

It is well recognized that the time series of hydrologic variables, such as rainfall and streamflow are significantly influenced by various large‐scale atmospheric circulation patterns. The influence of El Niño‐southern oscillation (ENSO) on hydrologic variables, through hydroclimatic teleconnection, is recognized throughout the world. Indian summer monsoon rainfall (ISMR) has been proved to be significantly influenced by ENSO. Recently, it was established that the relationship between ISMR and ENSO is modulated by the influence of atmospheric circulation patterns over the Indian Ocean region. The influences of Indian Ocean dipole (IOD) mode and equatorial Indian Ocean oscillation (EQUINOO) on ISMR have been established in recent research. Thus, for the Indian subcontinent, hydrologic time series are significantly influenced by ENSO along with EQUINOO. Though the influence of these large‐scale atmospheric circulations on large‐scale rainfall patterns was investigated, their influence on basin‐scale stream‐flow is yet to be investigated. In this paper, information of ENSO from the tropical Pacific Ocean and EQUINOO from the tropical Indian Ocean is used in terms of their corresponding indices for stream‐flow forecasting of the Mahanadi River in the state of Orissa, India. To model the complex non‐linear relationship between basin‐scale stream‐flow and such large‐scale atmospheric circulation information, artificial neural network (ANN) methodology has been opted for the present study. Efficient optimization of ANN architecture is obtained by using an evolutionary optimizer based on a genetic algorithm. This study proves that use of such large‐scale atmospheric circulation information potentially improves the performance of monthly basin‐scale stream‐flow prediction which, in turn, helps in better management of water resources. Copyright © 2007 John Wiley & Sons, Ltd.     

A preliminary dynamic view of the circulation of Jupiter's atmosphere

Summary The problem of the gross nature of the Jovian atmospheric circulation is examined from the viewpoint of the following previous findings of the writer and others. 1) The equatorial acceleration cannot be accounted for by axisymmetric motions. 2) The departures from symmetry in a rotating system having an equatorial acceleration must impart angular momentum selectively to those particles moving toward the jet maximum and abstract it from those moving away. 3) These selective (pressure) torques and associated sorting processes arise spontaneously in the presence of a vertical convection mode involving motions not independent of longitude, if the cell sizes and other conditions are right.Since there is evidence that Jovian dark spots have statistical maxima of occurrence along the tropical shear lines flanking the equator, these are assumed to be vertical convective systems forming, in effect,convective vortex sheets which generate the high angular momentum of the equatorial zone. Various additional concepts are discussed, and many comparisons with conditions in the sun and in the earth's atmosphere are made.     

欧亚地区夏季大气环流年际变化的关键区及亚洲夏季风的关联信号

本文利用资料分析和数值模拟方法研究了欧亚地区夏季大气环流的相关性及其与亚洲夏季风的关联信号,以期为欧亚地区的气候变异及可预测性研究提供科学依据.结果表明:欧亚区域同期(JJA)500 hPa高度场年际变化的关键区包括热带区、中纬度的贝加尔湖和巴尔喀什湖之间以及欧洲地中海附近地区;表面气温的关键区主要位于热带海洋;海平面气压的关键区包括热带的海洋性大陆区域、印度洋和非洲大陆赤道附近部分区域、中高纬的贝加尔湖与巴尔喀什湖之间的地区.另外,夏季大气环流年际变化的春季关键区明显西移/南退,特别是表面气温(其西太平洋区不再是关键区).公用气候系统模式CCSM4.0的大气模式在给定海温年际变化的情况下对于上述大气环流相关场及其关键区的模拟基本合理,其中500 hPa高度场的模拟结果较好,海平面气压场的结果逊之;对于同期和前期的结果,模式都有夸大西太平洋海温影响的倾向.对于东亚夏季风指数与大气环流的同期年际变化信号而言,其空间分布基本表现为以30°N为界呈西南东北向的波列状分布;其春季前期信号中,30°N以南的显著区几乎都位于海洋,30°N以北主要位于欧洲、巴尔喀什湖与贝加尔湖之间的地区.南亚夏季风指数的前期显著相关区比同期明显西移/南退.总之,模式的模拟结果和观测结果相当吻合,但其同期模拟结果比前期的更好一些.这些结果说明:模式对于大气环流年际变化的耦合变化信息的刻画是基本合理的,这为利用气候模式进行有关可预测性研究和降尺度预测研究奠定了基础.