Alexand er, M., J. Scott, 2002: The influence of ENSO on air-sea interaction in the Atlantic. Geophys. Res. Lett.,29, 46-1-46-4, doi: 10.1029/2001GL014347.10.1029/ and model experiments are used to investigate the influence of El Niño/the Southern Oscillation (ENSO) on air-sea interaction in the north Atlantic, Gulf of Mexico and Caribbean Sea. In one experiment, observed sea surface temperatures (SSTs) in the tropical Pacific are specified as boundary conditions in an atmospheric general circulation model (AGCM), while SSTs over the remainder of the global oceans are simulated by a mixed layer model. The observed warming in the tropical North Atlantic and cooling in the Gulf of Mexico in the winter/spring after ENSO peaks is well simulated by the model. Prior to the basin wide warming, latent heat fluxes generate negative SST anomalies in the Caribbean during August-October. Ocean-atmosphere coupling outside of the tropical Pacific significantly enhances the warm season atmospheric response to ENSO in the Caribbean region.
Ashok K., S. K. Behera, S. A. Rao, H. Y. Weng, and T. Yamagata, 2007: El Niño Modoki and its possible teleconnection. J. Geophys. Res.,112, doi: 10.1029/2006JC003798.10.1029/;jsessionid=F2C5797F7539FC367A07E919851C7401.f03t02[1] Using observed data sets mainly for the period 1979–2005, we find that anomalous warming events different from conventional El Ni09o events occur in the central equatorial Pacific. This unique warming in the central equatorial Pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly (SSTA) on both sides along the equator. empirical orthogonal function (EOF) analysis of monthly tropical Pacific SSTA shows that these events are represented by the second mode that explains 12% of the variance. Since a majority of such events are not part of El Ni09o evolution, the phenomenon is named as El Ni09o Modoki (pseudo-El Ni09o) (“Modoki” is a classical Japanese word, which means “a similar but different thing”). The El Ni09o Modoki involves ocean-atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution, analogous to the Southern Oscillation in the case of El Ni09o. Hence the total entity is named as El Ni09o–Southern Oscillation (ENSO) Modoki. The ENSO Modoki events significantly influence the temperature and precipitation over many parts of the globe. Depending on the season, the impacts over regions such as the Far East including Japan, New Zealand, western coast of United States, etc., are opposite to those of the conventional ENSO. The difference maps between the two periods of 1979–2004 and 1958–1978 for various oceanic/atmospheric variables suggest that the recen
Camargo S. J., A. G. Barnston, P. J. Klotzbach, and C. W. Landsea, 2007: Seasonal tropical cyclone forecasts. WMO Bulletin, 56, 297- 309.
Cao X., G. H. Chen, R. H. Huang, and W. Chen, 2014a: The intensity variation of the summer intertropical convergence zone in western North Pacific and its impact on tropical cyclones. Journal of Tropical Meteorology, 20, 193- 201.10.4028/ on the satellite data from the National Oceanic and Atmospheric Administration and the NCEP/NCAR reanalysis data, the variation of the intensity of convection over the Intertropical Convergence Zone(ITCZ) in summer and its impacts on tropical cyclones are studied. In this paper, an intensity index of the ITCZ is proposed according to Outgoing Longwave Radiation(OLR) in the region of(5°–20°N, 120°–150°E) in the western North Pacific(WNP). Then strong and weak ITCZ years are classified and different variables during the strong/weak ITCZ years are analyzed. The composite results show that the ITCZ anomaly is connected to the general atmospheric circulation and SST distribution. In the strong ITCZ years, the subtropical anticyclone weakens and shifts northward. Besides, there is salient cyclonic anomaly at the low level and anticyclonic anomaly at the high level. SST patterns in the preceding winter resemble to those of La Nina. It could persist into the succeeding summer. However, it is opposite in the weak ITCZ years. The impact of the ITCZ anomaly on the tropical cyclone(TC) formation and track is also discussed. There are more TCs over the WNP(5°–20°N, 120°–150°E) in the strong ITCZ years and there is a significant increase in the northward recurving TCs. In the weak ITCZ years, fewer TCs occur and the frequency of the northwestward track is higher.
Cao X., T. Li, M. Peng, W. Chen, and G. H. Chen, 2014b: Effects of monsoon trough interannual variation on tropical cyclogenesis over the western North Pacific. Geophys. Res. Lett.,41, 4332-4339, doi: 10.1002/2014GL060307.10.1002/ The western North Pacific monsoon trough (MT) exhibits marked interannual variation (IAV) associated with El Niño–Southern Oscillation forcing. The role of MT IAV in tropical cyclone (TC) development was investigated using the Advanced Research Weather Research and Forecasting model placed on a beta plane. It was found that MT IAV has a great influence on vortex development. In strong years, the MT provides more favorable environmental conditions—primarily through enhanced low-level vorticity, convergence and midlevel moisture—for TC formation and vice versa in weak years. Sensitivity experiments that separated the dynamic and thermodynamic (moisture) factors from strong MT IAV showed that the thermodynamic impact associated with MT IAV is comparable to the dynamic impact.
Cao X., T. Li, M. Peng, W. Chen, and G. H. Chen.2014c: Effects of monsoon trough intraseasonal oscillation on tropical cyclogenesis over the western North Pacific. J. Atmos. Sci., 71, 4639-
Cao X., S. F. Chen, G. H. Chen, W. Chen, and R. G. Wu.2015: On the weakened relationship between spring Arctic Oscillation and following summer tropical cyclone frequency over the western North Pacific: A comparison of 1968-1986 and 1989-2007. Adv. Atmos. Sci.,32, 1319-1328, doi: 10.1007/s00376-015-4256-y.10.1007/ study documents a weakening of the relationship between the spring Arctic Oscillation (AO) and the following summer tropical cyclone (TC) formation frequency over the eastern part (150°-180°E) of the western North Pacific (WNP). The relationship is strong and statistically significant during 1968-1986, but becomes weak during 1989-2007. The spring AOrelated SST, atmospheric dynamic, and thermodynamic conditions are compared between the two epochs to understand the possible reasons for the change in the relationship. Results indicate that the spring AO leads to an El Niño-like SST anomaly, lower-level anomalous cyclonic circulation, upper-level anomalous anticyclonic circulation, enhanced ascending motion, and a positive midlevel relative humidity anomaly in the tropical western-central Pacific during 1968-1986, whereas the AOrelated anomalies in the above quantities are weak during 1989-2007. Hence, the large-scale dynamic and thermodynamic anomalies are more favorable for TC formation over the eastern WNP during 1968-1986 than during 1989-2007.
Chan J. C. L., 1995: Tropical cyclone activity in the western North Pacific in relation to the stratospheric quasi-biennial oscillation. Mon. Wea. Rev., 123, 2567- 2571.10.1175/1520-0493(1995)123<2567:TCAITW>2.0.CO; Available
Chan J. C. L., 2005: Interannual and interdecadal variations of tropical cyclone activity over the western North Pacific. Meteor. Atmos. Phys., 89, 143- 152.10.1007/ paper reviews the interannual and interdecadal variations in tropical cyclone (TC) activity over the western North Pacific (WNP) and the possible physical mechanisms responsible for such variations. Interannual variations can largely be explained by changes in the planetary-scale flow patterns. Sea-surface temperatures (SSTs) in the WNP, however, do not contribute to such variations. Rather, SSTs in the central and eastern equatorial Pacific are significantly correlated with TC activity over the WNP. Causality can be established: changes in the SST in the equatorial Pacific are related to the El Niño/Southern Oscillation (ENSO) phenomenon, and modifications of the planetary-scale flow associated with ENSO alter the conditions over the WNP and hence TC activity there. Variations in annual TC activity are also associated with different phases of the stratospheric quasi-biennial oscillations due to its modification of the vertical wind shear of the environment in which TCs form. Interdecadal variations in TC activity are apparently related to the location, strength and extent of the North Pacific subtropical high. However, the mechanisms responsible for modifying these characteristics of the subtropical high have yet to be identified.
Chen D., H. J. Wang, J. P. Liu, and G. P. Li, 2014: Why the spring North Pacific Oscillation is a predictor of typhoon activity over the Western North Pacific. Int. J. Climatol.,35, 3353-3361, doi: 10.1002/joc.4213.10.1002/ In this study, we investigated the impact of the spring North Pacific Oscillation (NPO) on typhoon frequency over the Western North Pacific (WNP, north of the equator and west of dateline). To reduce the statistical uncertainty, all the data we used have been excluded the El Nino/Southern Oscillation signals. We found that the spring NPO positively correlated with the annual typhoon number over the WNP (hereafter TNWNP) during the period 1968-2010, with a correlation coefficient of 0.62 (above the 99% significance level). When the Northern Low and Southern High pattern over the north Pacific weakens, the TNWNP tends to increase. A positive phase of spring NPO is associated with the tropical circulation and sea surface temperature (SST) anomalies in the North Pacific, which may lead to unfavorable dynamical and thermal conditions for typhoon genesis over the WNP during JJAS. The negative anomaly of SST over the WNP, associated with the positive spring NPO anomaly, is connected to the tropical atmospheric circulations from spring to summer via good oceanic seasonal persistence and air-搒ea interaction. Thus, the spring NPO-related variability of the tropical atmospheric circulation as well as the SST can affect typhoon activity over the WNP. In addition, the spring NPO can also be adopted as a predictor for the summer rainfall in South China, since the spring NPO can modulate the WNP SST and western Pacific subtropical high from spring to summer.
Chen G. H., R. H. Huang, 2008: Influence of monsoon over the warm pool on interannual variation on tropical cyclone activity over the western North Pacific. Adv. Atmos. Sci.,25, 319-328, doi: 10.1007/s00376-008-0319-7.10.1090/ relationship between the interannual variation in tropical cyclone (TC) activity over the western North Pacific (WNP) and the thermal state over the warm pool (WP) is examined in this paper. The results show that the subsurface temperature in the WP is well correlated with TC geographical distribution and track type. Their relation is linked by the East Asian monsoon trough. During the warm years, the westward-retreating monsoon trough creates convergence and vorticity fields that are favorable for tropical cyclogenesis in the northwest of the WNP, whereas more TCs concentrating in the southeast result from eastward penetration of the monsoon trough during the cold years. The steering flows at 500 hPa lead to a westward displacement track in the warm years and recurving prevailing track in the cold years. The two types of distinct processes in the monsoon environment triggering tropical cyclogenesis are hypothesized by composites centered for TC genesis location corresponding to two kinds of thermal states of the WP. During the warm years, low-frequency intraseasonal oscillation is active in the west of the WNP such that eastward-propagating westerlies cluster TC genesis in that region. In contrast, during the cold years, the increased cyclogenesis in the southeast of the WNP is mainly associated with tropical depression type disturbances transiting from equatorially trapped mixed Rossby gravity waves. Both of the processes may be fundamental mechanisms for the inherent interannual variation in TC activity over the WNP.
Chen G. H., C. Y. Tam, 2010: Different impacts of two kinds of Pacific Ocean warming on tropical cyclone frequency over the western North Pacific. Geophys. Res. Lett., 37,L01803, doi: 10.1029/2009GL041708.10.1029/[1] The present study examines the relationship of ENSO Modoki and canonical ENSO, respectively, with the tropical cyclone (TC) frequency over the western North Pacific (WNP) for the period 1960–2008. The TC frequency is significantly positively correlated with ENSO Modoki index. The Ni09o-3 index has a markedly negative (positive) correlation with the TC frequency in the northern (southeastern) portion of the WNP. In response to heating source related to El Ni09o Modoki, a large-scale cyclonic anomaly forms over the WNP. In contrast, during the canonical El Ni09o years, zonally-elongated heating source and sink exhibit a meridional dipole pattern, which induces an anticyclonic anomaly in the subtropics and a cyclonic anomaly near the equatorial central Pacific. Numerical experiments under the realistic mean state and heating profiles validate that the anomalous circulation responses to heating play essential roles in different modulations of two kinds of Pacific Ocean warming on the TC frequency.
Chen S. F., R. G. Wu, and W. Chen, 2015: The changing relationship between interannual variations of the North Atlantic Oscillation and Northern Tropical Atlantic SST. J.Climate, 28, 485- 504.10.1175/ Available
Chen T. C., S. P. Weng, N. Yamazaki, and S. Kiehne, 1998: Interannual variation in the tropical cyclone formation over the western North Pacific. Mon. Wea. Rev., 126, 1080- 1090.10.1175/1520-0493(1998)126<1080:IVITTC>2.0.CO; The interannual variation in tropical cyclone genesis frequency over the western North Pacific was examined for the active tropical cyclone (including summer and fall) during 1979–94. An emphasis was put on the possible effect of the interannual variation of atmospheric circulation and monsoon trough on tropical cyclone occurrence. The major findings of this study are the following. A distinct increase (decrease) of tropical cyclone genesis frequency occurs north of the climatological location of the monsoon trough in the Philippine Sea during summers (June–August) with anomalous cold (warm) sea surface temperature (SST) over the NINO3 region. The interannual variation of tropical cyclone genesis in this region results from the appearance of an anomalous cyclonic (anticyclonic) cell situated in a summer teleconnection wave train emanating from the western tropical Pacific and progressing along the rim of the North Pacific. In addition to the north–south interannual variation, there is also a longitudinal interannual variation in the summer tropical cyclone genesis frequency over this region. The contrast of tropical cyclone genesis between the regions west and east of 150°E is reduced (enhanced) when the monsoon trough extends (retreats) eastward (westward) across this longitude during warm (cold) summers. For fall (September–November), there is no clear relationship between the north–south interannual variation in the tropical cyclone genesis over the western North Pacific and SST (NINO3). However, there is a perceptible tendency of the longitudinal interannual variation in tropical cyclone genesis frequency to follow the eastward extension/westward retreat of the monsoon trough in a way such as it does during the summer season.
Chia H. H., C. F. Ropelewski, 2002: The interannual variability in the genesis location of tropical cyclones in the northwest Pacific. J.Climate, 15, 2934-
Chiang J. C. H., A. H. Sobel, 2002: Tropical tropospheric temperature variations caused by ENSO and their influence on the remote tropical climate. J.Climate, 15, 2616- 2631.10.1175/1520-0442(2002)015<2616:TTTVCB>2.0.CO; The warming of the entire tropical free troposphere in response to El Niño is well established, and suggests a tropical mechanism for the El Niño outhern Oscillation (ENSO) teleconnection. The potential impact of this warming on remote tropical climates is examined through investigating the adjustment of a single-column model to imposed tropospheric temperature variations, assuming that ENSO controls interannual tropospheric temperature variations at all tropical locations. The column model predicts the impact of these variations in three typical tropical climate states (precipitation &gt; evaporation; precipitation &lt; evaporation; no convection) over a slab mixed layer ocean. Model precipitation and sea surface temperature (SST) respond significantly to the imposed tropospheric forcing in the first two climate states. Their amplitude and phase are sensitive to the imposed mixed layer depth, with the nature of the response depending on how fast the ocean adjusts to imposed tropospheric temperature forcing. For larger mixed layer depth, the SST lags the tropospheric temperature by a longer time, allowing greater disequilibrium between atmosphere and ocean. This causes larger surface flux variations, which drive larger precipitation variations. Moist convective processes are responsible for communicating the tropospheric temperature signal to the surface in this model. Preliminary observational analysis suggests that the above mechanism may be applicable to interpreting interannual climate variability in the remote Tropics. In particular, it offers a simple explanation for the gross spatial structure of the observed surface temperature response to ENSO, including the response over land and the lack thereof over the southeast tropical Atlantic and southeast tropical Indian Oceans. The mechanism predicts that the air-搒ea humidity difference variation is a driver of ENSO-related remote tropical surface temperature variability, an addition to wind speed and cloudiness variations that previous studies have shown to be important.
Choi K. S., C. C. Wu, and H. R. Byun, 2012: Possible connection between summer tropical cyclone frequency and spring Arctic Oscillation over East Asia. Climate Dyn., 38, 2613- 2629.10.1007/ study shows that the frequency of summer tropical cyclones (TCs) in the areas of Japan, Korea, and Taiwan (JKT), which are located in the middle latitudes of East Asia, has a positive correlation with the Arctic Oscillation (AO) occurring during the preceding spring, while summer TC frequency in the Philippines (PH), located in the low latitudes, has a negative correlation with the AO of the preceding spring. During a positive AO phase, when the anomalous anticyclone forms over the mid-latitudes of East Asia, other anomalous cyclones develop not only in the high latitudes but also in the low latitudes from the preceding spring to the summer months. With this change, while southeasterlies in the JKT area derived from the mid-latitude anticyclone plays a role in steering TCs toward this area, northwesterlies strengthened in the PH area by the low-latitude cyclone plays a role in preventing TC movement toward this area. In addition, because of this pressure systems developed during this AO phase, TCs occur, move, and recurve in further northeastern part of the western North Pacific than they do during a negative AO phase.
Chu P. S., X. Zhao, 2004: Bayesian change-point analysis of tropical cyclone activity: The central North Pacific case. J.Climate, 17, 4893- 4901.10.1175/ analysis is applied to detect change points in the time series of annual tropical cyclone counts over the central North Pacific. Specifically, a hierarchical Bayesian approach involving three layers—data, parameter, and hypothesis—is formulated to demonstrate the posterior probability of the shifts throughout the time from 1966 to 2002. For the data layer, a Poisson process with gamma distributed intensity is presumed. For the hypothesis layer, a “no change in the intensity” hypothesis and a “single change in the intensity” hypothesis are considered. Results indicate that there is a great likelihood of a change point on tropical cyclone rates around 1982, which is consistent with earlier work based on a simple log-linear regression model. A Bayesian approach also provides a means for predicting decadal tropical cyclone variations. A higher number of tropical cyclones is predicted in the next decade when the possibility of the change point in the early 1980s is taken into account.
Dee D. P., S. Uppala, 2009: Variational bias correction of satellite radiance data in the ERA-Interim reanalysis. Quart. J. Roy. Meteor. Soc., 135, 1830- 1841.10.1002/ Available
Ding H., N. S. Keenlyside, and M. Latif, 2012: Impact of the equatorial Atlantic on the El Niño Southern oscillation. Climate Dyn., 38, 1965- 1972.10.1007/ indicate that the Atlantic zonal mode influences El Niño Southern Oscillation (ENSO) in the Pacific, as already suggested in previous studies. Here we demonstrate for the first time using partial coupled experiments that the Atlantic zonal mode indeed influences ENSO. The partial coupling experiments are performed by forcing the coupled general circulation model (ECHAM5/MPI-OM) with observed sea surface temperature (SST) in the Tropical Atlantic, but with full air-sea coupling allowed in the Pacific and Indian Ocean. The ensemble mean of a five member simulation reproduces the observational results well. Analysis of observations, reanalysis, and coupled model simulations all indicate the following mechanism: SST anomalies associated with the Atlantic zonal mode affect the Walker Circulation, driving westward wind anomalies over the equatorial Pacific during boreal summer. The wind stress anomalies increase the east-west thermocline slope and enhance the SST gradient across the Pacific; the Bjerknes positive feedback acts to amplify these anomalies favouring the development of a La Niña-like anomalies. The same mechanisms act for the cold phase of Atlantic zonal mode, but with opposite sign. In contrast to previous studies, the model shows that the influence on ENSO exists before 1970. Furthermore, no significant influence of the Tropical Atlantic on the Indian Monsoon precipitation is found in observation or model.
Dommenget D., V. Semenov, and M Latif, 2006: Impacts of the tropical Indian and Atlantic Oceans on ENSO. Geophys. Res. Lett., 33,L11701, doi: 10.1029/2006GL025871.10.1029/ impacts of the tropical Indian and Atlantic Oceans on ENSO are studied using a series of 500 years long GCM simulations, in which the tropical Indian and/or Atlantic Ocean SSTs are fixed. The results indicate that the tropical Indian and/or Atlantic Oceans SST anomalies substantially influence the coupling over the equatorial Pacific. In the absence of SST variability in the tropical Indian and/or Atlantic Ocean, the main ENSO period is shifted by almost one year. The total SST variance in the equatorial Pacific region is reduced if either Indian or Atlantic Ocean variability is present. At the same time the atmospheric ENSO teleconnections are damped more strongly than the SST. The results can be understood in the context of the recharge oscillator model. However, it is difficult to verify the feedback of the Indian and/or Atlantic Oceans onto ENSO only with statistical analyses of the coupled model control integration or observations.
Du Y., L. Yang, and S. P. Xie, 2011: Tropical Indian Ocean influence on northwest Pacific tropical cyclones in summer following strong El Niño. J.Climate, 24, 315-
Emanuel K., 2005: Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436, 686- 688.10.1038/ and modelling predict that hurricane intensity should increase with increasing global mean temperatures, but work on the detection of trends in hurricane activity has focused mostly on their frequency and shows no trend. Here I define an index of the potential destructiveness of hurricanes based on the total dissipation of power, integrated over the lifetime of the cyclone, and show that this index has increased markedly since the mid-1970s. This trend is due to both longer storm lifetimes and greater storm intensities. I find that the record of net hurricane power dissipation is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multi-decadal oscillations in the North Atlantic and North Pacific, and global warming. My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and-taking into account an increasing coastal population-a substantial increase in hurricane-related losses in the twenty-first century.
Emanuel K., 2007: Environmental factors affecting tropical cyclone power dissipation. J.Climate, 20, 5497- 5509.10.1175/ Available
Gill A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc., 106, 447- 462.10.1002/ A simple analytic model is constructed to elucidate some basic features of the response of the tropical atmosphere to diabatic heating. In particular, there is considerable east-west asymmetry which can be illustrated by solutions for heating concentrated in an area of finite extent. This is of more than academic interest because heating in practice tends to be concentrated in specific areas. For instance, a model with heating symmetric about the equator at Indonesian longitudes produces low-level easterly flow over the Pacific through propagation of Kelvin waves into the region. It also produces low-level westerly inflow over the Indian Ocean (but in a smaller region) because planetary waves propagate there. In the heating region itself the low-level flow is away from the equator as required by the vorticity equation. The return flow toward the equator is farther west because of planetary wave propagation, and so cyclonic flow is obtained around lows which form on the western margins of the heating zone. Another model solution with the heating displaced north of the equator provides a flow similar to the monsoon circulation of July and a simple model solution can also be found for heating concentrated along an inter-tropical convergence line.
Goldenberg S. B., C. W. Land sea, A. M. Mestas-Nu\ nez, and W. M. Gray, 2001: The recent increase in Atlantic Hurricane activity: Causes and implications. Science, 293, 474-;journalcode=sci&amp;resid=293/5529/474
Gray W. M., 1968: Global view of the origin of tropical disturbances and storms. Mon. Wea. Rev., 96, 669- 700.10.1175/1520-0493(1968)096<0669:GVOTOO>2.0.CO; - Scientific documents that cite the following paper: Global view of the origin of tropical disturbances and storms
Ham Y. G., J. S. Kug, J. Y. Park, and F. F. Jin, 2013: Sea surface temperature in the north tropical Atlantic as a trigger for El Niño/Southern Oscillation events. Nature Geosci., 6, 112- 116.10.1038/ Ni09o events, the warm phase of the El Ni09o/Southern Oscillation (ENSO), are known to affect other tropical ocean basins through teleconnections. Conversely, mounting evidence suggests that temperature variability in the Atlantic Ocean may also influence ENSO variability. Here we use reanalysis data and general circulation models to show that sea surface temperature anomalies in the north tropical Atlantic during the boreal spring can serve as a trigger for ENSO events. We identify a subtropical teleconnection in which spring warming in the north tropical Atlantic can induce a low-level cyclonic atmospheric flow over the eastern Pacific Ocean that in turn produces a low-level anticyclonic flow over the western Pacific during the following months. This flow generates easterly winds over the western equatorial Pacific that cool the equatorial Pacific and may trigger a La Ni09a event the following winter. In addition, El Ni09o events led by cold anomalies in the north tropical Atlantic tend to be warm-pool El Ni09o events, with a centre of action located in the central Pacific, rather than canonical El Ni09o events. We suggest that the identification of temperature anomalies in the north tropical Atlantic could help to forecast the development of different types of El Ni09o event.
Ho C. H., H. S. Kim, J. H. Jeong, and S. W. Son, 2009: Influence of stratospheric quasi-biennial oscillation on tropical cyclone tracks in the western North Pacific. Geophys. Res. Lett., 36,L06702, doi: 10.1029/2009GL037163.10.1029/ possible influence of the stratospheric quasi-biennial oscillation (QBO) on tropical cyclone (TC) passages in the western North Pacific (WNP) is examined using TC data recorded by the Tokyo Typhoon Center and the QBO index derived from reanalysis data. The influence is observed to be significant. The number of TCs approaching the East China Sea is large during the westerly phase of the QBO; however, during the easterly phase, the number of TCs approaching the eastern offshore of Japan is large. This difference in the TC tracks is found to be related to the background flow change associated with the QBO. However, the total number of TC events over the WNP and the sum of the number of TCs approaching the aforementioned two regions appear to be unrelated to the QBO phases.
Hsu P. C., P. S. Chu, H. Murakami, and X. Zhao, 2014: An abrupt decrease in the late-season typhoon activity over the western North pacific. J.Climate, 27, 4296- 4312.10.1175/ Available
Huo L. W., P. W. Guo, S. N. Hameed, and D. C. Jin, 2015: The role of tropical Atlantic SST anomalies in modulating western North Pacific tropical cyclone genesis. Geophys. Res. Lett.,42, 2378-2384, doi: 10.1002/2015GL063184.10.1002/ connection between north tropical Atlantic (NTA) sea surface temperature (SST) anomalies and tropical cyclone (TC) genesis over the western North Pacific (WNP) and associated physical mechanisms are investigated in this study. We demonstrate a remarkable negative correlation of WNP TC genesis frequency with the (preceding) boreal spring NTA SST anomalies. Our analysis suggests that major factors for TC genesis including distributions of large-scale vorticity and midtropospheric humidity are rendered unfavorable by remote teleconnections while barotropic energy conversion from the large-scale flow is suppressed. As shown in recent studies, the remote teleconnection from the Atlantic is sustained and enhanced throughout the typhoon season through local air-sea interactions. These results suggest that boreal spring NTA SST anomaly could be a new predictor for the seasonal WNP TC activity.
Kalnay E., Coauthors, 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc., 77, 437-
Kao H. Y., J. Y. Yu, 2009: Contrasting eastern-Pacific and central-Pacific types of ENSO. J.Climate, 22, 615- 632.10.1175/ Available
Knapp K. R., M. C. Kruk, D. H. Levinson, H. J. Diamond, and C. J. Neumann, 2010: The international best track archive for climate stewardship (IBTrACS). Bull. Amer. Meteor. Soc., 91, 363- 376.
Knight J. R., R. J. Allan, C. K. Folland , M. Vellinga, and M. E. Mann, 2005: A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett., 32,L20708, doi: 10.1029/2005GL024233.10.1029/ ensemble of simulations of 20th Century climate using the HadCM3 coupled climate model forced with estimates of natural and anthropogenic forcings is compared with instrumental temperature data sets. The results show that while external climate forcing can account for most of 20th century climate change, there are also significant multidecadal climate fluctuations that are not produced by forcings. A major part of this variability corresponds to the `Atlantic Multidecadal Oscillation' (AMO), which has been identified in observations, and represents coherent fluctuations in temperature throughout most of the Northern Hemisphere. Using a 1400 year calculation with HadCM3 without external forcings, we show the model produces a quasi-periodic internal mode with a pattern, amplitude and characteristic time scale similar to that of the observed AMO. Further, the model implies the AMO is a genuine long-lived quasi-cyclical climate phenomenon related to large-scale oceanic heat transport variations associated with changes in the strength of the thermohaline circulation (THC) of about 2 Sv (10%). In the simulation, stronger cross-equatorial temperature gradients are associated with the anomalous northward ocean heat transport during a warm AMO phase. This causes a northward displacement of the mean ITCZ, leading to more rainfall and the development of anomalously fresh water in the tropical North Atlantic. These sustained anomalies slowly propagate to the subpolar North Atlantic in about 5 decades, where they act to slow the THC. The results also confirm observed links between the AMO and multidecadal variability in north-east Brazil and Sahel precipitation, and Atlantic hurricane formation. In addition, the simulated link between temperature and the THC allows an estimate of possible past changes in THC strength. Our results imply that the THC has undergone distinct strong and weak phases in the 20th century and has strengthened over recent decades. We also produce a forecast of the natural component of future THC change that shows a likely decline in the next 35 years to levels similar to the lowest levels reconstructed in the 20th century. This would accelerate anthropogenic THC weakening and the associated change in the AMO would offset Northern Hemisphere warming.
Kug J. S., F. F. Jin, and S. I. An, 2009: Two types of El Niño events: Cold tongue El Niño and warm pool El Niño. J.Climate, 22, 1499- 1515.
Land er, M. A., 1994: An exploratory analysis of the relationship between tropical storm formation in the western North Pacific and ENSO. Mon. Wea. Rev., 122, 636- 651.10.1175/1520-0493(1994)122<0636:AEAOTR>2.0.CO; Available
Li T., 2012: Synoptic and climatic aspects of tropical cyclogenesis in western North Pacific. Cyclones: Formation, Triggers and Control, K. Oouchi and H. Fudeyasu, Eds., Nova Science Publishers, 61- 94.
Losada T., B. Rodrguez-Fonseca I. Polo, S. Janicot, S. Gervois, F. Chauvin, and P. Ruti, 2009: Tropical response to the Atlantic equatorial mode: AGCM multimodel approach. Climate Dyn., 33, 45- 52.10.1007/ the frame of the AMMA -EU project, sensitivity experiments for an Atlantic Equatorial mode (AEM) which origin, development and damping resembles the observed one during the last decades of the 20th century, has been analysed in order to investigate the influence on the anomalous summer West African rainfall. Recent studies raise the matter of the AEM influence on the next Pacific ENSO episodes and also on the Indian Monsoon. This paper evaluates the response of four different atmospheric global circulation models, using the above-mentioned AEM sensitivity experiments, to study the tropical forcing associated with the Atlantic Niño mode. The results show a remote signal in both the Pacific and Indian basins. For a warm phase of the AEM the associated southward location of the ITCZ, with rising motions over the Equatorial Atlantic, leads to a global subsidence over the rest of the tropics, weakening the Asian Monsoon and favouring the La Niña conditions in the central Pacific. Although ocean-tmosphere coupled experiments are required to test the latter hypothesis, the present studies shows how the AEM is able to influence the rest of the tropics, a result with important implications on ENSO seasonal predictability.
Luo J. J., W. Sasaki, and Y. Masumoto, 2012: Indian Ocean warming modulates Pacific climate change. Proceedings of the National Academy of Sciences of United States of America, 109, 18 701- 18 706.10.1073/ has been widely believed that the tropical Pacific trade winds weakened in the last century and would further decrease under a warmer climate in the 21st century. Recent high-quality observations, however, suggest that the tropical Pacific winds have actually strengthened in the past two decades. Precise causes of the recent Pacific climate shift are uncertain. Here we explore how the enhanced tropical Indian Ocean warming in recent decades favors stronger trade winds in the western Pacific via the atmosphere and hence is likely to have contributed to the La Niña-like state (with enhanced east-west Walker circulation) through the Pacific ocean-atmosphere interactions. Further analysis, based on 163 climate model simulations with centennial historical and projected external radiative forcing, suggests that the Indian Ocean warming relative to the Pacific's could play an important role in modulating the Pacific climate changes in the 20th and 21st centuries.
Matsuno T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc.Japan, 44, 25- - Scientific documents that cite the following paper: Quasi-geostrophic motions in the equatorial area
McBride J. L., R. Zehr, 1981: Observational analysis of tropical cyclone formation. Part II: Comparison of non-developing versus developing systems. J. Atmos. Sci., 38, 1132- 1151.10.1175/1520-0469(1981)038<1132:OAOTCF>2.0.CO; thermodynamic and dynamic fields surrounding the composite tropical weather systems described in Part I (McBride, 1981a) are examined for differences between non-developing and developing systems. The main findings are as follows: (i) Both non-developing and developing systems are warm core in the upper levels. The temperature (and height) gradients are more pronounced in the developing system, but the magnitudes are so small that the differences would be difficult to measure for individual systems. (ii) The developing or pre-typhoon cloud cluster exists in a warmer atmosphere over a large horizontal scale, for example, out to 8° latitude radius in all directions. (iii) There is no obvious difference in vertical stability for moist convection between the systems. (iv) There is no obvious difference in moisture content or moisture gradient. (v) Pre-typhoon and pre-hurricane systems are located in large areas of high values of low-level relative vorticity. The low-level vorticity in the vicinity of a developing cloud cluster is approximately twice as large as that observed with non-developing cloud clusters. (vi) Mean divergence and vertical motion for the typical western Atlantic weather system are well below the magnitudes found in pre-tropical storm systems. (vii) Once a system has sufficient divergence to maintain 100 mb or more per day upward vertical motion over a 4° radius area, there appears to be no relationship between the amount of upward vertical velocity and the potential of the system for development. (viii) Cyclogenesis takes place under conditions of zero vertical wind shear near the system center. (ix) There is a requirement for large positive zonal shear to the north and negative zonal shear close to the south of a developing system. There is also a requirement for southerly shear to the west and northerly shear to the east. The scale of this shear pattern is over a 10° latitude radius circle with maximum amplitude at 6° radius.Under the assumption of a symmetric disturbance, these findings can be synthesized into one parameter for the potential of a system for development into a hurricane or typhoon: Daily Genesis Potential (DGP) = , when applied over 0-6° radius.Wind fields are examined surrounding 79 individual weather systems in the tropical Atlantic and it is shown that the composite findings are present on a case by case basis. The individual case analysis also reveals that the high values of DGP must be made up of fairly equal contributions from all directions around the disturbance. This is consistent with the requirement for the existence of zero lines in both zonal and meridional vertical shear.
Molinari J., D. Vollaro, 2013: What percentage of western North Pacific tropical cyclones form within the monsoon trough? Mon. Wea. Rev., 141, 499- 505.10.1175/ Available
Nolan D. S., 2007: What is the trigger for tropical cyclogenesis? Aust. Meteor. Mag., 56, 241- 266.10.1016/ development of a tropical cyclone from a pre-existing, weak, warm-core vortex is investigated with high-resolution cloud-resolving simulations using the Weather Research and Forecast Model (WRF). The simulation design and initial conditions are quite favourable for tropical cyclogenesis: the environment has a tropical sounding with no mean wind or wind shear, and the sea-surface temperature is held constant at 29 degrees C. Nonetheless, it is found that sporadic convection must occur for 48 to 72 hours before genesis and rapid intensification begins. During this time, before intensification, the vortex is found to go through important structural changes in both its wind field and its thermodynamics. While the low-level wind field decays due to friction, the inner core slowly becomes humidified due to moist detrainment and precipitation from deep convective towers. As the relative humidity in the core exceeds values of 80 per cent over most of the depth of the troposphere, a mid-level vortex forms, contracts and intensifies. Once the mid-level vortex has reached a sufficient strength, and the inner core is nearly saturated, a smaller scale vortex forms very rapidly at the surface. This smaller vortex becomes the core of an intensifying tropical cyclone. This process is explored through careful study of the inner-core dynamics and thermodynamics, with close attention paid to the changes in the moist convection as the inner core approaches saturation. While the frequency of deeper and stronger updraughts increases with time, the frequency of cool downdraughts remains essentially unchanged. In the hours before genesis, the intensification of the mid-level vortex leads to a large increase in the efficiency of the conversion of latent heat energy to the kinetic energy of the cyclonic wind field. The relative importances of the mid-level vortex and inner-core saturation are illustrated with additional simulations with different initial conditions and environmental soundings. Implications of these results for identifying and forecasting tropical cyclogenesis are discussed.
Saji N. H., T. Yamagata, 2003: Possible impacts of Indian Ocean Dipole Mode events on global climate. Climate Research, 25, 151- 169.10.3354/ of Indian Ocean Dipole mode (IOD) events on global climate are estimated by correlation/regression analysis. The analysis examined land rain and temperature and 3-dimensional atmospheric variables for a 42 yr period from January 1958 to December 1999. The correlation between IOD and the El Niño Southern Oscillation (ENSO) is accounted for using the multiple regression technique. We used partial correlation coefficients to describe the unique contribution of IOD to climate variability, independent of ENSO. In the Indian Ocean rim countries, IOD is associated with significant temperature and rain variability manifesting 2 large-scale patterns. In one, land tem- perature and rain are anomalously high over countries west of the Indian Ocean and anomalously low to its east. In the second pattern, enhanced rainfall is found over the Asian monsoon trough, extending from Pakistan up to southern China. Also noted are IOD impacts on several regions remote from the Indian Ocean. Strong correlation is found over Europe, northeast Asia, North and South America and South Africa concurrent with IOD events. Over these regions, positive IOD events are associated with warm land surface anomalies and reduced rainfall. The troposphere above the Indian Ocean exhibits strong variability during IOD events characterized by the following structures: (1) a Walker cell anomaly over the equator; (2) a deep modulation of monsoon westerlies; and (3) a Hadley cell anomaly over the Bay of Bengal. In the extratropics, IOD is associated with equivalent barotropic geopotential anomalies. These assume annular structure in the northern hemisphere, but Rossby wave train structure in the southern hemisphere.
Smith T. M., R. W. Reynolds, T. C. Peterson, and J. Lawrimore, 2008: Improvements to NOAA's historical merged land-ocean surface temperature analysis (1880-2006). J.Climate, 21, 2283- 2296.
Uppala, S. M., Coauthors, 2005: The ERA-40 re-analysis. Quart. J. Roy. Meteor. Soc., 131, 2961- 3012.10.1256/ ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized. A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the -榮econd-generation- ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. 漏 Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright.
Vimont D. J., J. P. Kossin, 2007: The Atlantic Meridional Mode and hurricane activity. Geophys. Res. Lett., 34,L07709, doi: 10.1029/2007GL029683.10.1029/[1] Connections between the Atlantic Meridional Mode (AMM) and seasonal hurricane activity are investigated. The AMM, a dynamical “mode” of variability intrinsic to the tropical coupled ocean-atmosphere system, is strongly related to seasonal hurricane activity on both decadal and interannual time scales. The connection arises due to the AMM's relationship with a number of local climatic conditions that all cooperate in their influence on hurricane activity. Further analysis indicates that the Atlantic Multi-decadal Oscillation (AMO) can excite the AMM on decadal time scales. As such, it is suggested that the AMO's influence on seasonal hurricane activity manifests itself through the AMM. This relationship between the AMM, AMO, and seasonal hurricane activity refocuses our understanding of how climate variations relate to seasonal hurricane activity in the Atlantic, and offers an improved framework beyond purely thermodynamic arguments that relates hurricanes to large-scale climate variations.
Wang B., J. C. L. Chan, 2002: How strong ENSO events affect tropical storm activity over the western North Pacific. J.Climate, 15, 1643- 1658.10.1175/1520-0442(2002)015<1643:HSEEAT>2.0.CO; analysis of 35-yr (1965-99) data reveals vital impacts of strong (but not moderate) El Ni09o and La Ni09a events on tropical storm (TS) activity over the western North Pacific (WNP). Although the total number of TSs formed in the entire WNP does not vary significantly from year to year, during El Ni09o summer and fall, the frequency of TS formation increases remarkably in the southeast quadrant (0°-17°N, 140°E-180°) and decreases in the northwest quadrant (17°-30°N, 120°-140°E). The July-September mean location of TS formation is 6° latitude lower, while that in October-December is 18° longitude eastward in the strong warm versus strong cold years. After the El Ni09o (La Ni09a), the early season (January-July) TS formation in the entire WNP is suppressed (enhanced). In strong warm (cold) years, the mean TS life span is about 7 (4) days, and the mean number of days of TS occurrence is 159 (84) days. During the fall of strong warm years, the number of TSs, which recurve northward across 35°N, is 2.5 times more than during strong cold years. This implies that El Ni09o substantially enhances poleward transport of heat-moisture and impacts high latitudes through changing TS formation and tracks.The enhanced TS formation in the SE quadrant is attributed to the increase of the low-level shear vorticity generated by El Ni09o-induced equatorial westerlies, while the suppressed TS generation over the NW quadrant is ascribed to upper-level convergence induced by the deepening of the east Asian trough and strengthening of the WNP subtropical high, both resulting from El Ni09o forcing. The WNP TS activities in July-December are noticeably predictable using preceding winter-spring Ni09o-3.4 SST anomalies, while the TS formation in March-July is exceedingly predictable using preceding October-December Ni09o-3.4 SST anomalies. The physical basis for the former is the phase lock of ENSO evolution to the annual cycle, while for the latter it is the persistence of Philippine Sea wind anomalies that are excited by ENSO forcing but maintained by local atmosphere-ocean interaction.
Wang H. J., K. Fan, 2007: Relationship between the Antarctic oscillation in the western North Pacific typhoon frequency. Chin. Sci. Bull., 52, 561- 565.10.1007/ between the Antarctic oscillation (AAO) and the western North Pacific typhoon number (WNPTN) in the interannual variability is examined in this research. The WNPTN is correlated with the AAO in June–July–August–September (JJAS) in 1949–1998 at 0.48 for the detrended time series, statistically significant at 99% level. The tropical atmospheric circulation as well as the sea surface temperature variability over the western Pacific associated with AAO has been analyzed. It follows that a positive phase of JJAS AAO corresponds to the larger magnitude of the vertical zonal wind shear, the anomalous low-lever anti-cyclonic circulation and anomalous high-level cyclonic circulation, and lower sea surface temperature in the major typhoon genesis region in the western North Pacific, thus providing unfavorable environment for the typhoon genesis, and vice versa. Supported by the National Natural Science Foundation of China (Grant Nos. 40631005 and 40620130113), and CAS International Partnership Project
Weng H. Y., K. Ashok, S. K. Behera, S. A. Rao, and T. Yamagata, 2007: Impacts of recent El Niño Modoki on dry/wet conditions in the Pacific rim during boreal summer. Climate Dyn., 29, 113- 129.10.1007/ work uses 1979–2005 monthly observational data to study the impacts of El Ni09o Modoki on dry/wet conditions in the Pacific rim during boreal summer. The El Ni09o Modoki phenomenon is characterized by the anomalously warm central equatorial Pacific flanked by anomalously cool regions in both west and east. Such zonal SST gradients result in anomalous two-cell Walker Circulation over the tropical Pacific, with a wet region in the central Pacific. There are two mid-tropospheric wave trains passing over the extratropical and subtropical North Pacific. They contain a positive phase of a Pacific-Japan pattern in the northwestern Pacific, and a positive phase of a summertime Pacific-North American pattern in the northeastern Pacific/North America region. The western North Pacific summer monsoon is enhanced, while the East Asian summer monsoon is weakened. In the South Pacific, there is a basin-wide low in the mid-latitude with enhanced Australian high and the eastern South Pacific subtropical high. Such an atmospheric circulation pattern favors a dry rim surrounding the wet central tropical Pacific. The El Ni09o Modoki and its climate impacts are very different from those of El Ni09o. Possible geographical regions for dry/wet conditions influenced by El Ni09o Modoki and El Ni09o are compared. The two phenomena also have very different temporal features. El Ni09o Modoki has a large decadal background while El Ni09o is predominated by interannual variability. Mixing-up the two different phenomena may increase the difficulty in understanding their mechanisms, climate impacts, and uncertainty in their predictions.
Wu L., Z. P. Wen, R. H. Huang, and R. G. Wu., 2012: Possible linkage between the monsoon trough variability and the tropical cyclone activity over the western North Pacific. Mon. Wea. Rev., 140, 140- 150.10.1175/ The present study investigates the influence of the monsoon trough (MT) on the interannual variability of tropical cyclone (TC) activity over the western North Pacific during July-揘ovember for the period 1979-2007. It is shown that the TC activity is closely related to the MT location. During the years when the MT extends eastward (retreats westward), more (less) TCs form within the southeastern quadrant of the western North Pacific. Such a relationship can be explained by the changes in large-scale environmental factors associated with the movement of the MT. An eastward extension of the MT coincides with warmed ocean surface, enhanced convection, increased relative humidity in the lower and midtroposphere, reduced vertical shear of zonal wind, intensified upper-level divergence, and low-level anomalous cyclonic vorticity over the southeast quadrant of the western North Pacific. These conditions associated with the eastern extension of the MT are favorable for TC genesis, while those associated with the westward retreat of the MT are not. Diagnosis of the barotropic energy conversion indicates that synoptic-scale disturbances moving westward from tropical eastern Pacific will gain the energy from the mean flow when they meet with the eastward-extending MT. This is an important reason for the linkage between MT variability and TC genesis over the western North Pacific.
Xie S. P., K. M. Hu, J. Hafner, H. Tokinaga, Y. Du, G. Huang, and T. Sampe, 2009: Indian Ocean capacitor effect on Indo-western Pacific climate during the summer following El Niño. J.Climate, 22, 730- 747.
Yang J. L., Q. Y. Liu, S. P. Xie, Z Y. Liu, and L. X. Wu, 2007: Impact of the Indian Ocean SST basin mode on the Asian summer monsoon. Geophys. Res. Lett., 34,L02708, doi: 10.1029/2006GL028571.10.1029/ an El Niño event, a basin-wide warming takes place over the tropical Indian Ocean, peaks in late boreal winter and early spring, and persists through boreal summer. Our observational analysis suggests that this Indian Ocean warming induces robust climatic anomalies in the summer Indo-West Pacific region, prolonging the El Niño's influence after tropical East Pacific sea surface temperature has returned to normal. In response to the Indian Ocean warming, precipitation increases over most of the basin, forcing a Matsuno-Gill pattern in the upper troposphere with a strengthened South Asian high. Near the ground, the southwest monsoon intensifies over the Arabian Sea and weakens over the South China and Philippine Seas. An anomalous anticyclonic circulation forms over the subtropical Northwest Pacific, collocated with negative precipitation anomalies. All these anomaly patterns are reproduced in a coupled model simulation initialized with a warming in the tropical Indian Ocean mixed layer, indicating that the Indian Ocean warming is not just a passive response to El Niño but important for summer climate variability in the Indo-West Pacific region. The implications for seasonal prediction are discussed.
Yang J. L., Q. Y. Liu, and Z. Y. Liu, 2010: Linking observations of the Asian monsoon to the Indian Ocean SST: Possible roles of Indian Ocean basin mode and dipole mode. J.Climate, 23, 5889- 5902, DOI: 10.1175/2010JCLI2962.1.10.1175/ Available
Yeh S. W., S. K. Kang, B. P. Kirtman, J. H. Kim, M. H. Kwon, and C. H. Kim, 2010: Decadal change in relationship between western North Pacific tropical cyclone frequency and the tropical Pacific SST. Meteor. Atmos. Phys., 106, 179- 189.10.1007/ this study, we examine the relationship between the number of tropical cyclones (TCs) in the western North Pacific and the tropical Pacific sea surface temperature (SST) during the main TC season (July-November) for the period of 1965-2006. Results show that there are periods when TC frequency and the tropical Pacific SST are well correlated and periods when the relationship breaks down. Therefore, decadal variation is readily apparent in the relationship between the TC frequency and the SST variations in the tropical Pacific. We further examine the oceanic and atmospheric states in the two periods (i.e., 1979-1989 vs. 1990-2000) when the marked contrast in the correlation between the TC frequency and the tropical Pacific SST is observed. Before 1990, the analysis indicates that oceanic conditions largely influenced anomalous TC frequency, whereas atmospheric conditions had little impact. After 1990, there the reverse appears to be the case, i.e., atmospheric conditions drive anomalous TC frequency and oceanic conditions are relatively unimportant. A role of atmosphere and ocean in relation to the TC development in the western North Pacific changes, which is consistent with the change of the correlations between the TC frequency and the tropical Pacific SST.
Yoo S. H., S. Yang, and C. H. Ho, 2006: Variability of the Indian Ocean sea surface temperature and its impacts on Asian-Australian monsoon climate. J. Geophys. Res., 111,D03108, doi: 10.1029/2005JD006001.10.1029/ this study, the authors investigate the relationships between the Indian Ocean (IO) sea surface temperature (SST) and the Asian-Australian monsoon (AAM) on seasonal to interannual timescales. They focus on the dominant features of IO SST, the impacts of IO SST on different monsoon components, and the relative importance of the northern and southern IO for the AAM. The dominant mode of IO SST is often characterized by uniform warming or cooling, with maximum variance in the Southern Hemisphere. This mode exerts a larger impact on monsoon variability than does the tropical IO dipole. The IO SST is strongly persistent from the boreal fall to the next spring even summer and less persistent from boreal summer to fall, a feature related to seasonal alternation of the dominance of the impacts of Pacific and IO SSTs on the Asian-Australian monsoons. While the tropical central Pacific SST exerts an apparently larger impact on the monsoon climate in the boreal winter and the transitional seasons, the IO SST affects the summer regional climate more strongly. The springtime IO SST leads to opposite changes in the south Asian monsoon (SAM) and the Southeast Asian monsoon (SEAM), reinforcing the out-of-phase relationship that appears often between the two monsoon components. While a warmer IO strengthens the SAM, it weakens the SEAM. Furthermore, the southern IO SST is related to the Asian summer monsoon more closely than the northern IO SST. The boreal fall IO SST, especially that in the north IO, is strongly associated with the subsequent Australian summer monsoon.
Yu J. H., T. Li, Z. M. Tan, and Z. W. Zhu, 2015: Effects of tropical North Atlantic SST on tropical cyclone genesis in the western North Pacific. Climate Dyn., doi: 10.1007/s00382-015-2618-x.10.1007/ tropical cyclone genesis number (TCGN) in July-October (JASO) over the western North Pacific (WNP) exhibits a robust interannual variation. It shows a longitudinally tri-pole pattern with a high in the eastern WNP and South China Sea (SCS) and a low in the western WNP, which explain 42.2 and 23.4 % of total TCGN variance in the eastern WNP and SCS, respectively. The high-low-high pattern is similar to that derived from a TC genesis potential index (GPI). To understand the cause of the longitudinal distribution of the dominant interannual mode, we examine the contributions of environmental parameters associated with GPI. It is found that relative humidity and relative vorticity are important factors responsible for TC variability in the SCS, while vertical shear and relative vorticity are crucial in determining TC activity in eastern WNP. A simultaneous correlation analysis shows that the WNP TCGN in JASO is significantly negatively correlated (with a correlation coefficient of -0.5) with sea surface temperature anomalies (SSTA) in the tropical North Atlantic (TNA). The longitudinal distribution of TC genesis frequency regressed onto TNA SSTA resembles that regressed upon the WNP TCGN series. The spatial patterns of regressed environmental variables onto the SSTA over the TNA also resemble those onto TCGN in the WNP, that is, an increase of relative humidity in the SCS and a weakening of vertical shear in the eastern WNP are all associated with cold SSTA in the TNA. Further analyses show that the cold SSTA in the TNA induce a negative heating in situ. In response to this negative heating, a low (upper)-level anomalous aniti-cyclonic (cyclonic) flows appear over the subtropical North Atlantic and eastern North Pacific, and to east of the cold SSTA, anomalous low-level westerlies appear in the tropical Indian Ocean. Given pronounced mean westerlies in northern Indian Ocean in boreal summer, the anomalous westerly flows increase local surface wind speed and surface evaporation and cool the SST in situ. Cold SSTA in northern Indian Ocean further suppress local convection, inducing anomalous westerlies to its east, leading to enhanced cyclonic vorticity and low surface pressure over the WNP monsoon trough region. Idealized numerical experiments further confirm this Indian Ocean relaying effect, through which cold SSTA in the tropical Atlantic exert a remote impact to circulation in the WNP.
Zhan R. F., Y. Wang, and X. T. Lei, 2011: Contributions of ENSO and East Indian Ocean SSTA to the interannual variability of northwest Pacific tropical cyclone frequency. J.Climate, 24, 509- 521.10.1175/ Available
Zhan R. F., Y. Wang, and T. Li, 2014: Intensified impact of East Indian Ocean SST anomaly on tropical cyclone genesis frequency over the western North Pacific. J.Climate, 27, 8724-
Zhao X., P. S. Chu, 2010: Bayesian changepoint analysis for extreme events (typhoons, heavy rainfall, and heat waves): An RJMCMC approach. J.Climate, 23, 1034- 1046.10.1175/ Available
Zhou B. T., X. Cui, 2008: Hadley circulation signal in the tropical cyclone frequency over the western North Pacific. J. Geophys. Res., 113,D16107, doi: 10.1029/2007JD009156.10.1029/ relationship between the boreal spring (March-May) Hadley circulation (HC) and the following summer (June-September) tropical cyclone (TC) frequency expressed as the total number of TCs in the western North Pacific is investigated through using the observed data. Results show that the spring HC is negatively correlated to the summer TC frequency. Such a relationship can be explained by the changes of the atmospheric circulations related to anomalous spring HC. A strong spring HC is followed by the weaker East Asian monsoon, stronger vertical zonal wind shear, and reduced convection over the western North Pacific in summer, which are unfavorable for TC genesis, and vice versa. The potential mechanism of how the spring HC affects the summer atmospheric circulations is also preliminarily identified. It is found that sea surface temperature (SST) anomalies in the Indian Ocean and the South China Sea may play important roles, since an anomalous spring HC can excite simultaneous SST anomalies, which can persist to the following summer and in turn give rise to the atmospheric anomalies associated with TC activities. Thus the variation of the spring HC can be a potential indicator in predicting summer TC activities over the western North Pacific.
Zhou B. T., X. Cui, 2011: Sea surface temperature east of Australia: A predictor of tropical cyclone frequency over the western North Pacific? Chin. Sci. Bull., 56, 196- 201.10.1007/ relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is correlated negatively to spring SST east of Australia.When the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind shear.These conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF decreases.The negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North Pacific.The spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.
Zhou B. T., X. Cui, 2014: Interdecadal change of the linkage between the North Atlantic Oscillation and the tropical cyclone frequency over the western North Pacific. Science China Earth Sciences, 57, 2148- 2155.10.1007/ 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.