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1.
The Circum-Pacific Teleconnection Pattern (CPTP) is revealed in the meridional wind in the high troposphere via an emprirical orthogonal function (EOF) and correlation analysis on NCEP/NCAR reanalysis data. The CPTP is found to be composed of the North Pacific-North American teleconnection pattern (PNA), the South Pacific-South American teleconnection pattern (PSA), and the teleconnection patterns over the tropical western Pacific and the tropical eastern Pacific (or, Central America, or, tropical Atlantic). There is substantial interannual variability of the CPTP and a typical CPTP can be detected in some years. It is speculated that the zonal wind anomalies over the equatorial region in the western and eastern sides of the Pacific may play a role in linking the two hemispheres. The anomalous convection activities in the Tropics are plausible triggering factors for the zonal wind anomalies that are responsible for the composition of the CPTP.  相似文献   

2.
The sea surface temperature(SST) in the Indian Ocean affects the regional climate over the Asian continent mostly through a modulation of the monsoon system.It is still difficult to provide an a priori indication of the seasonal variability over the Indian Ocean.It is widely recognized that the warm and cold events of SST over the tropical Indian Ocean are strongly linked to those of the equatorial eastern Pacific.In this study,a statistical prediction model has been developed to predict the monthly SST over the tropical Indian Ocean.This model is a linear regression model based on the lag relationship between the SST over the tropical Indian Ocean and the Ni o3.4(5°S-5°N,170°W-120°W) SST Index.The predictor(i.e.,Ni o3.4 SST Index) has been operationally predicted by a large size ensemble El Ni o and the Southern Oscillation(ENSO) forecast system with coupled data assimilation(Leefs_CDA),which achieves a high predictive skill of up to a 24-month lead time for the equatorial eastern Pacific SST.As a result,the prediction skill of the present statistical model over the tropical Indian Ocean is better than that of persistence prediction for January 1982 through December 2009.  相似文献   

3.
Based on the monthly mean OLR, geopotential height and wind data from the NCEP/NCAR reanalyzed data sets for 1982-1996, the atmospheric teleconnection associated with the warm pool of the tropical western Pacific and Asian monsoon region during E1 Nino and non-El Niño years are studied diagnostically in this paper. It is found that, the teleconnection pattern caused by the activity of the Asian summer monsoon (ASM) emanates from the Asian monsoon region to the tropical eastern Pacific via the Aleutians in summer of the El Niño years. In the non-El Niño years, however, the ASM-related teleconnection pattern stretches northward and westward from the Asian monsoon region, exerting its influences mainly on the circulation over middle and high latitude rather than that over the tropical eastern Pacific. Evidences also show that the anomalous convection over the tropical western Pacific warm pool leads to the East Asia/Pacific(EAP) teleconnection pattern during the non-El Niño years. It is interesting to note that the teleconnection in the 500 height field associated with the warm pool convection disappears in the El Niño years. The differences of the teleconnection pattern between the El Niño years and the non-El Niño years suggest that the activities of the ASM and the convection over the warm pool of the tropical western Pacific, the most energetic weather events in boreal summer, are intertwined and interactive with other global-scale circulation in different ways under different climate backgrounds.  相似文献   

4.
Singular value decomposition (SVD) is conducted of 15 winter tropical Pacific SST with 500 hPa filtered potential height variance over the northern Pacific storm track. It is shown that the first coupled mode obtained depicts the effect on the track of SSTA over equatorial central and eastern Pacific. Further composite analysis indicates that the SSTA over there during winter can give rise to or invigorate PNA teleconnection response pattern in 500 hPa height field which, in turn, exerts crucial influence on the interannual variability in vigor and east-west displacement of the Pacific storm track, especially over its central and eastern part.  相似文献   

5.
In this paper the Bulk Aerodynamic Formulas are used to compute the latent and sensible heat fluxes over the area 8°S-20°N, 130°-180°E for each month from January 1950 through December 1979 by using the data set of COADS supplied by N'OAA of USA. The annual and monthly geographical distributions and the seasonal cycle of heat fluxes are carried out and a seasonal change of heal tluxes for ENSO year is also obtained by compositing individual ENSO year including 1951, 1953, 1957, 1963, 1965, 1969, 1972 and 1976. It is found that outing ENSO epi sodes positive anomalies of heal fluxes appeared during the period of March to July and negative anomalies from August to March of the following year. The time series of sum of heat fluxes for March, April, May, June and July in each year from 1950 through 1979 had a significant link to the eastern tropical Pacific SST index (Wright, 1983). The correlation coefficient was 0.56. As it is found that in the latter half of each ENSO year (August-December) the frequ  相似文献   

6.
In this study, in order to investigate the global climatic oscillations forced by sea surface temperature (SST) anomalies over equatorial central-eastern Pacific, two numerical schemes with different SST distri-butions (normal and anomalous cases) are tested by using a nine-layer global spectral model. Experiment results show that (i) in northern summer, a wave train that is similar to the teleconnection pattern suggested by Nitta (1987) and Huang (1987) in the Northern Hemisphere and another one in the Southern Hemisphere are reproduced; (ii) simulated results suggest that the response of atmosphere in middle-high latitudes of both hemispheres to an anomalous heating source is more sensitive in tropical western Pacific than in equatorial central-eastern Pacific; and (iii) in northern summer, the formation of low-frequency oscillations on monthly (seasonal) time scale results from energy dispersion as well as interactions between eddies and zonal flow; and between eddies.  相似文献   

7.
Previous studies suggest that spring SST anomalies over the northern tropical Atlantic(NTA) affect the tropical cyclone(TC) activity over the western North Pacific(WNP) in the following summer and fall. The present study reveals that the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is not stationary. The influence of spring NTA SST on following summer–fall WNP TC genesis frequency is weak and insignificant before, but strong and significant after, the late 1980 s. Before the late 1980 s, the NTA SST anomaly-induced SST anomalies in the tropical central Pacific are weak, and the response of atmospheric circulation over the WNP is not strong. As a result, the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is insignificant in the former period. In contrast,after the late 1980 s, NTA SST anomalies induce pronounced tropical central Pacific SST anomalies through an Atlantic–Pacific teleconnection. Tropical central Pacific SST anomalies further induce favorable conditions for WNP TC genesis,including vertical motion, mid-level relative humidity, and vertical zonal wind shear. Hence, the connection between NTA SST and WNP TC genesis frequency is significant in the recent period. Further analysis shows that the interdecadal change in the connection between spring NTA SST and following summer–fall WNP TC genesis frequency may be related to the climatological SST change over the NTA region.  相似文献   

8.
studying the relationship between SST in the tropical Indian Ocean （TIO）, tropical western Pacific （TWP）, and tropical eastern Pacific （TEP） and East Asian summer rainfall （EASR）, using data provided by NOAA/OAR/ESRL PSD and the National Climate Center of China for the period 1979-2008, an index, SSTDI, was defined to describe the SST difference between the TIO and TWP. In comparison with the winter ENSO, the spring SST contrast between the TIO and TWP was found to be more significantly associated with summer rainfall in East Asia, especially along the EASR band and in Northeast China. This spring SST contrast can persist into summer, resulting in a more significant meridional teleconnection pattern of lower-tropospheric circulation anomalies over the western North Pacific and East Asia. These circulation anomalies are dynamically consistent with the summer rainfall anomaly along the EASR band. When the SSTDI is higher （lower） than normal, the EASR over the Yangtze River valley, Korea, and central and southern Japan is heavier （less） than normal. The present results suggest that this spring SST contrast can be used as a new and better predictor of EASR anomalies.  相似文献   

9.
Using the ERA-40 data and numerical simulations, this study investigated the teleconnection over the extratropical Asian-Pacific region and its relationship with the Asian monsoon rainfall and the climatological characteristics of tropical cyclones over the western North Pacific, and analyzed impacts of the Tibetan Plateau （TP） heating and Pacific sea surface temperature （SST） on the teleconnection. The Asian-Pacific oscillation （APO） is defined as a zonal seesaw of the tropospheric temperature in the midlatitudes of the Asian-Pacific region. When the troposphere is cooling in the midlatitudes of the Asian continent, it is warming in the midlatitudes of the central and eastern North Pacific; and vice versa. The APO also appears in the stratosphere, but with a reversed phase. Used as an index of the thermal contrast between Asia and the North Pacific, it provides a new way to explore interactions between the Asian and Pacific atmospheric circulations. The APO index exhibits the interannual and interdecadal variability. It shows a downward trend during 1958-2001, indicating a weakening of the thermal contrast, and shows a 5.5-yr oscillation period. The formation of the APO is associated with the zonal vertical circulation caused by a difference in the solar radiative heating between the Asian continent and the North Pacific. The numerical simulations further reveal that the summer TP heating enhances the local tropospheric temperature and upward motion, and then strengthens downward motion and decreases the tropospheric temperature over the central and eastern North Pacific. This leads to the formation of the APO. The Pacific decadal oscillation and El Nino/La Nina over the tropical eastern Pacific do not exert strong influences on the APO. When there is an anomaly in the summer APO, the South Asian high, the westerly jet over Eurasia, the tropical easterly jet over South Asia, and the subtropical high over the North Pacific change significantly, with anomalous Asian monsoon rainfall and tropical cyclon  相似文献   

10.
The relationships between the tropical Indian Ocean basin(IOB)/dipole(IOD) mode of SST anomalies(SSTAs) and ENSO phase transition during the following year are examined and compared in observations for the period 1958–2008.Both partial correlation analysis and composite analysis show that both the positive(negative) phase of the IOB and IOD(independent of each other) in the tropical Indian Ocean are possible contributors to the El Nio(La Nia) decay and phase transition to La Nia(El Nio) about one year later. However, the influence on ENSO transition induced by the IOB is stronger than that by the IOD. The SSTAs in the equatorial central-eastern Pacific in the coming year originate from subsurface temperature anomalies in the equatorial eastern Indian and western Pacific Ocean, induced by the IOB and IOD through eastward and upward propagation to meet the surface. During this process, however the contribution of the oceanic channel process between the tropical Indian and Pacific oceans is totally different for the IOB and IOD. For the IOD, the influence of the Indonesian Throughflow transport anomalies could propagate to the eastern Pacific to induce the ENSO transition. For the IOB, the impact of the oceanic channel stays and disappears in the western Pacific without propagation to the eastern Pacific.  相似文献   

11.
Summer rainfall variations in North China closely relate to that in India. It seems that an alternation of signs of " , -, " exists in the geographical pattern of the correlation in summer rainfall from North China to India through the Tibetan Plateau. However, it appears that the teleconnection of summer rainfall variations between North China and India is unstable. Over 1945 - 1974, the correlation coefficient (hereafter as CC) is as large as 0.7. In contrast, the CC is about-0.3 over 1827-1856. Further studies, based on observations starting from 1813, showed that the correlation is strong when summer rainfalls in both North China and India are large, and vice versa. In order to find what induce the change of the teleconnection, variations of summer rainfall in both North China and India, mean sea surface temperature (SST) in the eastern equatorial Pacific and the frequency of ENSO events were examined in relation to the change of the teleconnection. The result showed that the teleconnection appears weak when the mean SST is high and the frequency of La Nia events is low; the teleconnection is strong when the mean SST is low and the frequency of La Nia events is high. At last, it is notable that La Nia happens in only 3 years during the recent 30 years from 1976 to 2005 and the teleconnection becomes weak too.  相似文献   

12.
The relationship between tropical cyclone activity and ENSO is examined for the major cyclone regions using crosscorrelations,spectral analysis and composite analysis of eastern equatorial Pacific sea surface temperature,thenormalised monthly Southern Oscillation Index(SOI),and tropical cyclone frequencies.The closest relationship betweenthe 3—4 year ENSO period and tropical cyclone activity was found in the western North Pacific west of 160°E and thereseems to be significant potential for seasonal forecasting in this region based on ENSO parameters alone.No significantrelationships were found for the North Indian Ocean,and the remainder of the basins were dominated by oscillationsnear the quasi-biennial period.Physical explanations and forecasting of the seasonal variations in tropical cyclone num-bers in these regions will need to account for the QBO as well as the 3—4 year ENSO connections.  相似文献   

13.
Applying the empirical orthogonal function (EOF) analysis to the sea surface temperature (SST) field of the tropical Pacific and Indian Oceans for determination of the first eigenvector field, the current work reveals that there are significant zonal gradients of SST in all seasons of the year in the northwestern and eastern Indian Ocean and equatorial central and eastern Pacific and western Pacific. It is also found that the variance contribution rates of the first EOF mode of every season is more than 33%. This shows that this kind of spatial distribution of the SST is stable. This pattern is named Pacific-Indian Oceans SSTA mode. Through careful analysis and comparison, an index of the mode was defined.  相似文献   

14.
Using the NCEP/NCAR reanalysis data, the China rainfall data of the China Meteorological Administration, and the sea surface temperature (SST) data of NOAA from 1951-2000, the features of the anomalous longitudinal position of the subtropical high in the western Pacific (SHWP) in the pre-rainy season in South China and associated circulation and precipitation are studied. Furthermore, the relationship between SHWP and SST and the eastern Asian winter monsoon is also investigated. Associated with the anomalous longitudinal position of SHWP in the pre-rainy season in South China, the flow patterns in both the middle and lower latitudes are different. The circulation anomalies greatly influence the precipitation in the pre-rainy season in South China. When the SHWP is in a west position (WP), the South China quasi-stationary front is stronger with more abundant precipitation there. However, when the SHWP is in an east position (EP), a weaker front appears with a shortage of precipitation there. There exists a good relationship between the longitudinal position of SHWP and SST in the tropical region. A negative correlation can be found both in the central and eastern tropical Pacific and the Indian Ocean.This means that the higher (lower) SST there corresponds to a west (east) position of SHWP. This close relationship can be found even in the preceding autumn and winter. A positive correlation appears in the western and northern Pacific and large correlation coefficient values also occur in the preceding autumn and winter. A stronger eastern Asian winter monsoon will give rise to cooler SSTs in the Kuroshio and the South China Sea regions and it corresponds to negative SST anomaly (SSTA) in the central and eastern Pacific and positive SSTA in the western Pacific in winter and the following spring. The whole tropical SSTA pattern, that is, positive (negative) SSTA in the central and eastern Pacific and negative (positive) SSTA in the western Pacific, is favorable to the WP (EP) of SHWP.  相似文献   

15.
The different patterns of SST changes under the +8.5 W m-2 Representative Concentration Pathway(RCP8.5) projected by the latest two versions of the Flexible Global Ocean-Atmosphere-Land System model(FGOALS-g2 and FGOALS-s2; grid-point version 2 and spectral version 2, respectively), and the potential mechanisms for their formation are studied in this paper. The results show that, although both FGOALS-g2 and FGOALS-s2 project global warming patterns, FGOALS-g2(FGOALS-s2) projects a La Nia-like(an El Nio-like) mean warming pattern with weakest(strongest) warming over the central(eastern) equatorial Pacific for 2081–2100 relative to 1986–2005 under RCP8.5. A mixed layer heat budget analysis shows that the projected tropical Pacific Ocean warming in both models is primarily caused by atmospheric forcing. The main differences in the heating terms contributing to the SST changes between the two models are seen in the downward longwave radiation and ocean forcing. The minimum SST warming over the equatorial Pacific in FGOALS-g2 is attributed to the local minimum heating of downward longwave radiation and maximum cooling of ocean forcing. In contrast, the maximum SST warming over the equatorial Pacific in FGOALS-s2 is due to the maximum warming of downward longwave radiation, and the contribution of ocean forcing is minor. The minimum SST warming over the equatorial Pacific in FGOALS-g2 emerges around the 2050 s, before when the SST over the equatorial Pacific is warmer than that over the extra-equatorial Pacific. In FGOALS-s2, the SST difference shows a continuous increasing trend for 2006– 2100. Further examination of the oceanic and atmospheric circulation changes is needed to reveal the process responsible for the longwave radiation and ocean forcing difference between the two models.  相似文献   

16.
Based on the reanalysis data of monthly mean global SST and wind from the NCEP/NCAR and the observation data of rain seasons in 124 stations of Yunnan province from 1961 to 2006, we applied the analytical methods of correlation analysis and composite analysis and a significance testing method to two sets of samples of average differences. The goal is to investigate into the influence of the Southern Hemispheric (SH) SST on the summer precipitation in Yunnan from January to May so as to identify the key time and marine regions. Physical mechanisms are obtained by analyzing the influence of sea level wind and the key marine regions on the precipitation during Yunnan’s rain season. Results show that there is indeed significant relationship between the SST in SH and summer precipitation in Yunnan. The key areas for influencing the summer precipitation are mainly distributed in a region called “West Wind Drift” in the SH, including the Southeast Indian, southern Australia, west coast of eastern Pacific off Chile, Peru and the southwest Atlantic Magellan. Besides, the most significant marine region is the west coast of Chile and Peru (cold-current areas of the eastern Pacific). Diagnostic analysis results also showed that monsoons in the Bay of Bengal, a cross-equatorial flow in the Indian Ocean near the equator and southwest monsoon in India weaken during the warm phase of the Peruvian cold current in the eastern Pacific. Otherwise, they strengthen.  相似文献   

17.
Using hindcasts of the Beijing Climate Center Climate System Model, the relationships between interannual variability （IAV） and intraseasonal variability （ISV） of the Asian-western Pacific summer monsoon are diagnosed. Predictions show reasonable skill with respect to some basic characteristics of the ISV and IAV of the western North Pacific summer monsoon （WNPSM） and the Indian summer monsoon （ISM）. However, the links between the seasonally averaged ISV （SAISV） and seasonal mean of ISM are overestimated by the model. This deficiency may be partially attributable to the overestimated frequency of long breaks and underestimated frequency of long active spells of ISV in normal ISM years, although the model is capable of capturing the impact of ISV on the seasonal mean by its shift in the probability of phases. Furthermore, the interannual relationships of seasonal mean, SAISV, and seasonally averaged long-wave variability （SALWV; i.e., the part with periods longer than the intraseasonal scale） of the WNPSM and ISM with SST and low-level circulation are examined. The observed seasonal mean, SAISV, and SALWV show similar correlation patterns with SST and atmospheric circulation, but with different details. However, the model presents these correlation distributions with unrealistically small differences among different scales, and it somewhat overestimates the teleconnection between monsoon and tropical central-eastern Pacific SST for the ISM, but underestimates it for the WNPSM, the latter of which is partially related to the too-rapid decrease in the impact of E1 Nifio-Southern Oscillation with forecast time in the model.  相似文献   

18.
By using the simulation results of an AGCM, which had been run from 1945 to 1993 forced by COADS SST, the interdecadal variability of the model atmosphere was investigated and compared with that of NCEP reanalysis data. It was found that, interdecadal variability exists significantly in both the tropical Pacific wind fields and the mid-high latitude atmospheric circulation of the model atmosphere. The tendency of time variation and spatial distributions of the interdecadal variability of the model atmosphere are basically consistent with observation. Relative to the mid-high latitude atmospheric circulation, the simulation of tropical Pacific wind is more satisfying, which suggests that anomalous variation of SST is still the main factor for the interdecadal variability of tropical Pacific wind. It might have more significant influence on the tropical wind than on the mid-high latitude atmosphere. However, there is still obvious difference between the simulation and observation. They could be attributed to both the simulation capability of the model and absence of other factors in the model which are important for the interdecadal climate variation.  相似文献   

19.
The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model.The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific.The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation.Equatorial upwelling dominates the heat budget in that region.Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model.After introducing the seasonal cycle of chlorophyll-a concentration,the peak of the power spectrum becomes broad,and longer periods(>3 years) are found.These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves,which are caused by the shallow mean thermocline in the northeastern Pacific.  相似文献   

20.
A statistically-based low-level cloud parameterization scheme is introduced, modified, and applied in the Flexible coupled General Circulation Model (FGCM-0). It is found that the low-level cloud scheme makes improved simulations of low-level cloud fractions and net surface shortwave radiation fluxes in the subtropical eastern oceans off western coasts in the model. Accompanying the improvement in the net surface shortwave radiation fluxes, the simulated distribution of SSTs is more reasonably asymmetrical about the equator in the tropical eastern Pacific, which suppresses, to some extent, the development of the double ITCZ in the model. Warm SST biases in the ITCZ north of the equator are more realistically reduced, too. But the equatorial cold tongue is strengthened and extends further westward, which reduces the precipitation rate in the western equatorial Pacific but increases it in the ITCZ north of the equator in the far eastern Pacific. It is demonstrated that the low-level cloud-radiation feedback would enhance the cooperative feedback between the equatorial cold tongue and the ITCZ. Based on surface layer heat budget analyses, it is demonstrated that the reduction of SSTs is attributed to both the thermodynamic cooling process modified by the increase of cloud fractions and the oceanic dynamical cooling processes associated with the strengthened surface wind in the eastern equatorial Pacific, but it is mainly attributed to oceanic dynamical cooling processes associated with the strengthening of surface wind in the central and western equatorial Pacific.  相似文献   

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