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1.
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o event. By using historical upper layer temperature data (1955-2003) for the tropical Pacific Ocean, the tempera- ture-based SLAT is also calculated and the meridional variation can be found in the historical El Nio events (1955-2003), which suggests that the meridional shifts of the sea level anomaly are also intrinsic oscillating modes of the El Nio cycles like the zonal shifts.  相似文献   

2.
By analyzing the variability of global SST(sea surface temperature) anomalies,we propose a unified Ni o index using the surface thermal centroid anomaly of the region along the Pacific equator embraced by the 0.7°C contour line of the standard deviation of the SST anomalies and try to unify the traditional Ni o regions into a single entity.The unified Ni o region covers almost all of the traditional Ni o regions.The anomaly time series of the averaged SST over this region are closely correlated to historical Ni o indices.The anomaly time series of the zonal and meridional thermal centroid have close correlation with historical TNI(Trans-Ni o index) indices,showing differences among El Ni o(La Ni a) events.The meridional centroid anomaly suggests that areas of maximum temperature anomaly are moving meridionally(although slightly) with synchronous zonal movement.The zonal centroid anomalies of the unified Ni o region are found helpful in the classification of the Eastern Pacific(EP)/Central Pacific(CP) types of El Ni o events.More importantly,the zonal centroid anomaly shows that warm areas might move during a single warming/cooling phase.All the current Ni o indices can be well represented by a simple linear combination of unified Ni o indices,which suggests that the thermal anomaly(SSTA) and thermal centroid location anomaly of the unified Ni o region would yield a more complete image of each El Ni o/ La Ni a event.  相似文献   

3.
The interannual variability of the sea surface temperature (SST) in the South China Sea (SCS) is investigated according to its relationship with El Nio/La Nia (EN/LN) using monthly products from ICOADS. The SCS SST bears two peaks associated with EN/LN and shows the asymmetric features. Coinciding with the mature phase of EN/LN, the first SST warming/cooling peaks in December(0)-February(1) (DJF(1)) and centers in the southern part. The major difference is in the amplitude associated with the strength of EN/LN. However, the SCS SST anomaly shows distinct difference after the mature phase of EN/LN. The EN SST warm-ing develops a mid-summer peak in June-August(1) (JJA(1)) and persists up to September-October(1), with the same amplitude of the first warming peak. Whereas the LN SST cooling peaks in May(1), it decays slowly until the end of the year, with amplitude much weaker. Comparing with SST and atmospheric circulations, the weak response and early termination of the second cooling is due to the failure of the cyclonic wind anomalies to develop in the northwest Pacific during JJA(1).  相似文献   

4.
The South China Sea (SCS) is significantly influenced by El Nio and the Southern Oscillation (ENSO) through ENSO-driven atmospheric and oceanic changes.We analyzed measurements made from 1960 to 2004 to investigate the interannual variability of the latent and sensible heat fluxes over the SCS.Both the interannual variations of latent and sensible heat fluxes are closely related to ENSO events.The low-pass mean heat flux anomalies vary in a coherent manner with the low-pass mean Southern Oscillation Index ...  相似文献   

5.
Lag correlations between sea surface temperature anomalies(SSTA) in the southeastern tropical Indian Ocean(STIO) in fall and Nio 3.4 SSTA in the eastern equatorial Pacific in the following fall are subjected to decadal variation,with positive correlations during some decades and negative correlations during others. Negative correlations are smaller and of shorter duration than positive correlations. Variations in lag correlations suggest that the use of the Indian Ocean Dipole(IOD) as a predictor of the El Nio Southern Oscillation(ENSO) at a lead time of one year is not effective during some decades. In this study,lag correlations between IOD and ENSO anomalies were analyzed to investigate why the IOD-ENSO teleconnection disappears during decades with negative correlations. Anomalies induced by the IOD in the equatorial Pacific Ocean during decades with negative correlations are still present,but at a greater depth than in decades with positive correlations,resulting in a lack of response to oceanic channel dynamics in the cold tongue SSTA. Lag correlations between oceanic anomalies in the west Pacific warm pool in fall and the equatorial Pacific cold tongue with a one-year time lag are significantly positive during decades with negative correlations. These results suggest that oceanic channel dynamics are overwhelmed by oceanatmosphere coupling over the equatorial Pacific Ocean during decades with negative correlations. Therefore,the Indonesian throughflow is not effective as a link between IOD signals and the equatorial Pacific ENSO.  相似文献   

6.
We objectively define the onset date of the South China Sea (SCS) summer monsoon, after having evaluated previous studies and considered various factors. Then, interannual and interdecadal characteristics of the SCS summer monsoon onset are analyzed. In addition, we calculate air-sea heat fluxes over the Indian Ocean using the advanced method of CORARE3.0, based on satellite remote sensing data. The onset variation cycle has remarkable interdecadal variability with cycles of 16 a and 28 a. Correlation analysis between air-sea heat fluxes in the Indian Ocean and the SCS summer monsoon indicates that there is a remarkable lag correlation between them. This result has important implications for prediction of the SCS summer monsoon, and provides a scientific basis for further study of the onset process of this monsoon and its prediction. Based on these results, a linear regression equation is obtained to predict the onset date of the monsoon in 2011 and 2012. The forecast is that the onset date of 2011 will be normal or 1 pentad earlier than the normal year, while the onset date in 2012 will be 1-2 pentads later.  相似文献   

7.
The Flexible Global Ocean-Atmosphere-Land System Model-gamil (FGOALS-g) was used to study the spring prediction barrier (SPB) in an ensemble system. This coupled model was developed and maintained at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG). There are two steps in our hindcast experiments. The first is to integrate the coupled model continuously with sea surface temperature (SST) nudging, from 1971 to 2006. The second is to carry out a series of one-year hindcasts without SST nudging, by adopting initial values from the first step on January 1 st , April 1st , July 1st , and October 1st , from 1982 to 2005. We generate 10 ensemble members for a particular start date (1st ) by choosing different atmospheric and land conditions around the hindcast start date (1st through 10th ). To estimate the predicted SST, two methods are used: (1) Anomaly Correlation Coefficient and its rate of decrease; and (2) Talagrand distribution and its standard deviation. Results show that FGOALS-g offers a reliable ensemble system with realistic initial atmospheric and oceanic conditions, and high anomaly correlation (>0.5) within 6 month lead time. Further, the ensemble approach is effective, in that the anomaly correlation of ensemble mean is much higher than that of most individual ensemble members. The SPB exists in the FGOALS-g ensemble system, as shown by anomaly correlation and equal likelihood. Nevertheless, the role of the ensemble mean in reducing the SPB of ENSO prediction is significant. The rate of decrease of the ensemble mean is smaller than the largest deviations by 0.04-0.14. At the same time, the ensemble system "equal likelihood" declines during spring. An ensemble mean helps give a correct prediction direction, departing from largely-deviated ensemble members.  相似文献   

8.
This paper proposes a WD-GA-LSSVM model for predicting the displacement of a deepseated landslide triggered by seasonal rainfall,in which wavelet denoising(WD)is used in displacement time series of landslide to eliminate the GPS observation noise in the original data,and genetic algorithm(GA)is applied to obtain optimal parameters of least squares support vector machines(LSSVM)model.The model is first trained and then evaluated by using data from a gentle dipping(~2°-5°)landslide triggered by seasonal rainfall in the southwest of China.Performance comparisons of WD-GA-LSSVM model with Back Propagation Neural Network(BPNN)model and LSSVM are presented,individually.The results indicate that the adoption of WD-GA-LSSVM model significantly improves the robustness and accuracy of the displacement prediction and it provides a powerful technique for predicting the displacement of a rainfall-triggered landslide.  相似文献   

9.
The standard deviation of the central Pacific sea surface temperature anomaly (SSTA) during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the Central Pacific El Nio (CP-El Nio) and has a connection with the subtropical air-sea interaction in the northeastern Pacific. After removing the influence of the Eastern Pacific El Nio, an S-EOF analysis is conducted and the leading mode shows a clear seasonal SSTA evolving from the subtropical northeastern Pacific to the tropical central Pacific with a quasi-biennial period. The initial subtropical SSTA is generated by the wind speed decrease and surface heat flux increase due to a north Pacific anomalous cyclone. Such subtropical SSTA can further influence the establishment of the SSTA in the tropical central Pacific via the wind-evaporation-SST (WES) feedback. After established, the central equatorial Pacific SSTA can be strengthened by the zonal advective feedback and thermocline feedback, and develop into CP-El Nio. However, as the thermocline feedback increases the SSTA cooling after the mature phase, the heat flux loss and the re-versed zonal advective feedback can cause the phase transition of CP-El Nio. Along with the wind stress variability, the recharge (discharge) process occurs in the central (eastern) equatorial Pacific and such a process causes the phase consistency between the thermocline depth and SST anomalies, which presents a contrast to the original recharge/discharge theory.  相似文献   

10.
This study examines the modulation of tropical cyclogenesis over the South China Sea(SCS) by the El Nio-Southern Oscillation(ENSO) Modoki during the boreal summer. Results reveal that there were more tropical cyclones(TCs) formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors(including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity) contribute to this influence is investigated, using a genesis potential(GP) index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modoki-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC frequency over the SCS by the ENSO Modoki during the boreal summer.  相似文献   

11.
Debris flow is one of the most destructive phenomena of natural hazards. Recently, major natural haz-ard, claiming human lives and assets, is due to debris flow in the world. Several practical methods for forecasting de-bris flow have been proposed, however, the accuracy of these methods is not high enough for practical use because of the stochastic and non-linear characteristics of debris flow. Artificial neural network has proven to be feasible and use-fill in developing models for nonlinear systems. On the other hand, predicting the future behavior based on a time se-ries of collected historical data is also an important tool in many scientific applications. In this study we present a three-layer feed-forward neural network model to forecast surge of debris flow according to the time series data collect-ed in the Jiangjia Ravine, situated in north part of Yunnan Province of China. The simulation and prediction of debris flow using the proposed approach shows this model is feasible, however, further studies are needed.  相似文献   

12.
Perturbed solving method for interdecadal sea-air oscillator model   总被引：1，自引：0，他引：1  
A coupled system of the interdecadal sea-air oscillator model is studied.The El Nio-southern oscillation(ENSO) atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions.The oscillator model is involved with the variations of both the eastern and western Pacific anomaly pat-terns.This paper proposes an ENSO atmospheric physics model using a method of the perturbation theory.The aim is to create an asymptotic solving method for the ENSO model.Employing the perturbed method,the asymptotic solution of corresponding problem is obtained,and the asymptotic behaviour of the solution is studied.Thus we can obtain the prognoses of the sea surface temperature anomaly and related physical quantities.  相似文献   

13.
Long-range precipitation forecasts are useful when managing water supplies.Oceanicatmospheric oscillations have been shown to influence precipitation.Due to a longer cycle of some of the oscillations,a short instrumental record is a limitation in using them for long-range precipitation forecasts.The influence of oscillations over precipitation is observable within paleoclimate reconstructions;however,there have been no attempts to utilize these reconstructions in precipitation forecasting.A data-driven model,KStar,is used for obtaining long-range precipitation forecasts by extending the period of record through the use of reconstructions of oscillations.KStar is a nearest neighbor algorithm with an entropy-based distance function.Oceanic-atmospheric oscillation reconstructions include the El Nino-Southern Oscillation(ENSO),the Pacific Decadal Oscillation(PDO),the North Atlantic Oscillation(NAO),and the Atlantic Multi-decadal Oscillation(AMO).Precipitation is forecasted for 20 climate divisions in the western United States.A 10-year moving average is applied to aid in the identification of oscillation phases.A lead time approach is used to simulate a one-year forecast,with a 10-fold cross-validation technique to test the models.Reconstructions are used from 1658-1899,while the observed record is used from 1900-2007.The model is evaluated using mean absolute error(MAE),root mean squared error(RMSE),RMSE-observations standard deviation ratio(RSR),Pearson’s correlation coefficient(R),NashSutcliffe coefficient of efficiency(NSE),and linear error in probability space(LEPS) skill score(SK).The role of individual and coupled oscillations is evaluated by dropping oscillations in the model.The results indicate ’good’ precipitation estimates using the KStar model.This modeling technique is expected to be useful for long-term water resources planning and management.  相似文献   

14.
There are two different modeling approaches which have been proposed and utilized to derive residual currents: the first approach is equivalent to deducing residual currents from current-meter records using filtering techniques or time averages of time-series records to remove tidal variations; in the second approach, filters or time averages over several tidal cycles are applied to the hydrodynamic equations to generate the governing equations for residual circulation. Based on the latter, both the baroclinic dynamic models of residual circulation are proposed, of which one is a two-dimensional transport model and the other is a three-dimensional model with variable eddy viscosity. The two-dimensional transport model is a direct generalization from the barotropic model of residual circulation presented by Nihoul and Randy (1975) and Heaps (1978) to the baroclinic model. In the three-dimensional model with variable eddy viscosity, using a Sturm-Liouville system adopted in the reference [5], the nondimen  相似文献   

15.
A three-dimensional isopycnic-coordinate ocean model for the study of internal tides is presented. In this model, the ocean interior is viewed as a stack of isopycnic layers, each characterized by a constant density. The isopycnic coordinate performs well at tracking the depth variance of the thermocline, and is suitable for simulation of internal tides. This model consists of external and internal modes, and barotropic and baroclinic motions are calculated in the two modes, respectively. The capability of simulating internal tides was verified by comparing model results with an analytical solution. The model was then applied to the simulation of internal tides in the South China Sea (SCS) with the forcing of M2 and K1 tidal constituents. The results show that internal tides in the SCS are mainly generated in the Luzon Strait. The generated M2 internal tides propagate away in three different directions (branches). The branch with the widest tidal beam propagates eastward into the Pacific Ocean, the most energetic branch propagates westward toward Dongsha Island, and the least energetic branch propagates southwestward into the basin of the SCS. The generated K1 internal tides propagate in two different directions (branches). One branch propagates eastward into the Pacific Ocean, and the other branch propagates southwestward into the SCS basin. The steepening process of internal tides due to shoaling effects is described briefly. Meridionally integrated westward energy fluxes into the SCS are comparable to the meridionally integrated eastward energy fluxes into the Pacific Ocean.  相似文献   

16.
Chinese summer extreme rainfall often brings huge economic losses, so the prediction of summer extreme rainfall is necessary. This study focuses on the predictability of the leading mode of Chinese summer extreme rainfall from empirical orthogonal function(EOF) analysis. The predictors used in this study are Arctic sea ice concentration(ASIC) and regional sea surface temperature(SST) in selected optimal time periods. The most important role that Arctic sea ice(ASI) plays in the appearance of EOF1 may be strengthening the high pressure over North China, thereby preventing water vapor from going north. The contribution of SST is mainly at low latitudes and characterized by a significant cyclone anomaly over South China. The forecast models using predictor ASIC(PA), SST(PS), and the two together(PAS) are established by using data from 1980 to 2004. An independent forecast is made for the last 11 years(2005-2015). The correlation coefficient(COR) skills between the observed and cross-validation reforecast principal components(PC) of the PA, PS, and PAS models are 0.47, 0.66, and 0.76, respectively. These values indicate that SST is a major cause of Chinese summer extreme rainfall during 1980-2004. The COR skill of the PA model during the independent forecast period of 2004-2015 is 0.7, which is significantly higher than those of the PS and PAS models. Thus, the main factor influencing Chinese summer extreme rainfall in recent years has changed from low latitudes to high latitudes. The impact of ASI on Chinese summer extreme rainfall is becoming increasingly significant.  相似文献   

17.
Qinhuangdao City is located in the mid-latitude monsoon-affected region, and the timing of sea-ice coverage changes from year to year, making sea-ice forecasting difficult. In this paper, we propose a statistical model using the 1980–2013 data collected at the Qinhuangdao observation station. The start date and the duration of ice coverage are fitted with four marginal distributions, from which the best-fitted, i.e., the Weibull distribution, is selected to form a joint probability density function(PDF), built by the Gaussian copula method, for the two variables. With a given start date forecast by the Gray-Markov model(GMM), the joint PDF becomes a conditional probability model, which predicts that the duration of ice coverage is most likely 33 days at the Qinhuangdao observation station in 2014–2015. The predicted duration value is only two days less than the actual situation. The results prove that the new prediction model is feasible and effective to predict the period of ice coverage. The general sea-ice conditions that the sea ice would most likely form on December 8 and last for 80 days at the Qinhuangdao observation station could also be obtained from the joint PDF. The statistical model provides a useful tool to forecast ice conditions for planning and management of maritime activities.  相似文献   

18.
Heat center of the western Pacific warm pool   总被引：1，自引：0，他引：1  
A heat center (HC) of the western Pacific warm pool (WPWP) is defined, its variability is examined, and a possible mechanism is discussed. Analysis and calculation of a temperature dataset from 1945-2006 show that the mean position of the HC during this period was near 0.4°S/169.0°E, at 38.0 m depth. From a time series of the HC, remarkable seasonal variability was found, mainly in the meridional and vertical directions. Interannual variabilities were dominant in the zonal and vertical directions. In addition, semiannual variation in the HC depth was discovered. The longitude of the HC varies with ENSO events, and its latitude is weakly related to ENSO on time scales shorter than a decade. The variation of the HC longitude leads the Nio-3 index by about 3-4 months, and its depth lags the index for approximately 3 months. It is concluded that the HC depth results from a combination of its longitudinal and latitudinal variations. Low-pass-filtered time series reveal that the HC has moved eastward since the mid 1980s.  相似文献   

19.
A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one or several existing shear surfaces. The framework is developed based on a thorough analysis of the scientific literature and with reference to significant reported case studies for which a consistent dataset of continuous displacement measurements is available. Three distinct trends of movement are defined to characterize the kinematic behavior of the active stages of slow-moving landslides in a velocity-time plot： a linear trend-type I, which is appropriate for stationary phenomena; a convex shaped trend-type II, which is associated with rapid increases in pore water pressure due to rainfall, followed by a slow decrease in the groundwater level with time; and a concave shaped trend-type III, which denotes a non-stationary process related to the presence of new boundary conditions such as those associated with the development of a newly formed local slip surface that connects with the main existing slip surface. Within the proposed framework, a model is developed to forecast future displacements for active stages of trend-type II based on displacement measurements at the beginning of the stage. The proposed model is validated by application to two case studies.  相似文献   

20.
China is a country in the period of economy takeoff. We cannot use the common method to forecast its fu-ture economy level. This paper establishes an economic level forecast model of the countries whose economy is in the takeoff because of the stimulation of model country. The enlightenment of the model is from physics. If there are two sub-stances, A and B, and a medium between them, according to physics, when substance A is hotter than B, B‘ s tempera-ture will inevitably rise and close to that of A. Thus, this system tends to be a state of balance. Three factors affect heatconduction between substance A and B. They are the difference of temperature between two substances, the conductivityof medium and the characteristics of themselves. The model is testified through two examples. And then we forecast theeconomic development level of China in long term. This paper raises a model to solve the problem of research approaches.However, since there are some limitations on data source, problems will appear. For example, in certain years, our fore-cast results do not suit the real situation. But in the long term, the tendency is accurate. Then this model can be amendedin accordance with different situations.  相似文献   

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