Accurate prediction of tropical cyclone(TC)intensity is challenging due to the complex physical processes involved.Here,we introduce a new TC intensity prediction scheme for the western North Pacific(WNP)based on a ti...Accurate prediction of tropical cyclone(TC)intensity is challenging due to the complex physical processes involved.Here,we introduce a new TC intensity prediction scheme for the western North Pacific(WNP)based on a time-dependent theory of TC intensification,termed the energetically based dynamical system(EBDS)model,together with the use of a long short-term memory(LSTM)neural network.In time-dependent theory,TC intensity change is controlled by both the internal dynamics of the TC system and various environmental factors,expressed as environmental dynamical efficiency.The LSTM neural network is used to predict the environmental dynamical efficiency in the EBDS model trained using besttrack TC data and global reanalysis data during 1982–2017.The transfer learning and ensemble methods are used to retrain the scheme using the environmental factors predicted by the Global Forecast System(GFS)of the National Centers for Environmental Prediction during 2017–21.The predicted environmental dynamical efficiency is finally iterated into the EBDS equations to predict TC intensity.The new scheme is evaluated for TC intensity prediction using both reanalysis data and the GFS prediction data.The intensity prediction by the new scheme shows better skill than the official prediction from the China Meteorological Administration(CMA)and those by other state-of-art statistical and dynamical forecast systems,except for the 72-h forecast.Particularly at the longer lead times of 96 h and 120 h,the new scheme has smaller forecast errors,with a more than 30%improvement over the official forecasts.展开更多
Based on the Regional Specialized Meteorological Center(RSMC)Tokyo-Typhoon Center best-track data and the NCEP-NCAR reanalysis dataset,extratropical transitioning(ET)tropical cyclones(ETCs)over the western North Pacif...Based on the Regional Specialized Meteorological Center(RSMC)Tokyo-Typhoon Center best-track data and the NCEP-NCAR reanalysis dataset,extratropical transitioning(ET)tropical cyclones(ETCs)over the western North Pacific(WNP)during 1951–2021 are classified into six clusters using the fuzzy c-means clustering method(FCM)according to their track patterns.The characteristics of the six hard-clustered ETCs with the highest membership coefficient are shown.Most tropical cyclones(TCs)that were assigned to clusters C2,C5,and C6 made landfall over eastern Asian countries,which severely threatened these regions.Among landfalling TCs,93.2%completed their ET after landfall,whereas 39.8%of ETCs completed their transition within one day.The frequency of ETCs over the WNP has decreased in the past four decades,wherein cluster C5 demonstrated a significant decrease on both interannual and interdecadal timescales with the expansion and intensification of the western Pacific subtropical high(WPSH).This large-scale circulation pattern is favorable for C2 and causes it to become the dominant track pattern,owning to it containing the largest number of intensifying ETCs among the six clusters,a number that has increased insignificantly over the past four decades.The surface roughness variation and three-dimensional background circulation led to C5 containing the maximum number of landfalling TCs and a minimum number of intensifying ETCs.Our results will facilitate a better understanding of the spatiotemporal distributions of ET events and associated environment background fields,which will benefit the effective monitoring of these events over the WNP.展开更多
There is limited understanding regarding the formation of multiple tropical cyclones(MTCs).This study explores the environmental conditions conducive to MTC formation by objectively determining the atmospheric circula...There is limited understanding regarding the formation of multiple tropical cyclones(MTCs).This study explores the environmental conditions conducive to MTC formation by objectively determining the atmospheric circulation patterns favorable for MTC formation over the western North Pacific.Based on 199 MTC events occurring from June to October 1980–2020,four distinct circulation patterns are identified:the monsoon trough(MT)pattern,accounting for 40.3%of occurrences,the confluence zone(CON)pattern at 26.2%,the easterly wave(EW)pattern at 17.8%,and the monsoon gyre(MG)pattern at 15.7%.The MT pattern mainly arises from the interaction between the subtropical high and the monsoon trough,with MTCs forming along the monsoon trough and its flanks.The CON pattern is affected by the subtropical high,the South Asian high,and the monsoon trough,with MTCs emerging at the confluence zone where the prevailing southwesterly and southeasterly flows converge.The EW pattern is dominated by easterly flows,with MTCs developing along the easterly wave train.MTCs in the MG pattern arise within a monsoon vortex characterized by strong southwesterly flows.A quantitative analysis further indicates that MTC formation in the MT pattern is primarily governed by mid-level vertical velocity and low-level vorticity,while mid-level humidity and vertical velocity are significantly important in the other patterns.The meridional shear and convergence of zonal winds are essential in converting barotropic energy from the basic flows to disturbance kinetic energy,acting as the primary source for eddy kinetic energy growth.展开更多
The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captu...The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captured by seasonal predictions,a skillful prediction of the WPSH variation might have warned us of the increased probability of extreme weather events in Central and Northern China.However,the mechanism for the WPSH variation in July 2021 and its seasonal predictability are still unknown.Here,the observed northward shift of the WPSH in July 2021 is shown to correspond to a meridional dipole pattern of the 850-hPa geopotential height to the east of China,the amplitude of which became the strongest since 1979.The meridional dipole pattern is two nodes of the Pacific–Japan pattern.To investigate the predictability of the WPSH variation,a 21-member ensemble of seasonal predictions initiated from the end of June 2021 was conducted.The predictable and unpredictable components of the meridional dipole pattern were identified from the ensemble simulations.Its predictable component is driven by positive precipitation anomalies over the tropical western Pacific.The positive precipitation anomalies are caused by positive horizonal advection of the mean moist enthalpy by southwesterly anomalies to the northwestern flank of anticyclonic anomalies excited by the existing La Niña,which is skillfully predicted by the model.The leading mode of the unpredictable component is associated with the atmospheric internal intraseasonal oscillations,which are not initialized in the simulations.The relative contributions of the predictable and unpredictable components to the observed northward shift of the WPSH at 850 hPa are 28.0%and 72.0%,respectively.展开更多
The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the e...The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the evolution of the El Niño-Southern Oscillation(ENSO).The possible linkage between the EZW over the western Pacific and the offequatorial monsoonal winds associated with the WNPSM and its decadal changes have not yet been fully understood.Here,we find a non-stationary relationship between the WNPSM and the western Pacific EZW,significantly strengthening their correlation around the late 1980s/early 1990s.This observed shift in the WNPSM–EZW relationship could be explained by the changes in the related sea surface temperature(SST)configurations across the tropical oceans.The enhanced influence from the springtime tropical North Atlantic,summertime tropical central Pacific,and maritime continent SST anomalies may be working together in contributing to the recent intensified WNPSM–EZW co-variability.The observed recent strengthening of the WNPSM–EZW relationship may profoundly impact the climate system,including prompting more effective feedback from the WNPSM on subsequent ENSO evolution and bolstering a stronger biennial tendency of the WNPSM–ENSO coupled system.The results obtained herein imply that the WNPSM,EZW,ENSO,and the tropical North Atlantic SST may be closely linked within a unified climate system with a quasi-biennial rhythm occurring during recent decades,accompanied by a reinforcement of the WNPSM–ENSO interplay quite possibly triggered by enhanced tropical Pacific–Atlantic cross-basin interactions.These results highlight the importance of the tropical Atlantic cross-basin influences in shaping the spatial structure of WNPSM-related wind anomalies and the WNPSM–ENSO interaction.展开更多
As important atmospheric circulation patterns in Northern Hemisphere(NH),the North Atlantic Oscillation(NAO)and the Western Pacific teleconnection(WP)affect the winter climate in Eurasia.In order to explore the combin...As important atmospheric circulation patterns in Northern Hemisphere(NH),the North Atlantic Oscillation(NAO)and the Western Pacific teleconnection(WP)affect the winter climate in Eurasia.In order to explore the combined effects of NAO and WP on East Asian(EA)temperature,the NAO and WP indices are divided into four phases from 1980−2021:the positive NAO and WP phase(NAO+/WP+),the negative NAO and WP phase(NAO−/WP−),the positive NAO and negative WP phase(NAO+/WP−),the negative NAO and positive WP phase(NAO−/WP+).In the phase of NAO+/WP+,the low geopotential height(GH)stays in north of EA at 50°−80°N;the surface air temperature anomaly(SATA)is 0.8−1℃lower than Southern Asian.In the phase of NAO−/WP−,the center of high temperature and GH locate in the northeast of EA;the cold air spreads to Southern Asia,causing the SATA decreases 1−1.5℃.In the phase of NAO+/WP−,the high GH belt is formed at 55°−80°N.Meanwhile,the center of high SATA locates in the north of Asia that increases 0.8−1.1℃.The cold airflow causes temperature dropping 0.5−1℃in the south of EA.The SATA improves 0.5−1.5℃in south of EA in the phase of NAO−/WP+.The belt of high GH is formed at 25°−50°N,and blocks the cold air which from Siberia.The NAO and WP generate two warped plate pressure structures in NH,and affect the temperature by different pressure configurations.NAO and WP form different GH,and GH acts to block and push airflow by affecting the air pressure,then causes the temperature to be different from the north and south of EA.Finally,the multiple linear regression result shows that NAO and WP are weakened by each other such as the phase of NAO+/WP+and NAO−/WP−.展开更多
This study reveals the strengthened interdecadal relationship between the western North Pacific summer monsoon(WNPSM)and tropical central-western Pacific sea surface temperature anomaly(SSTA)in summer after the early ...This study reveals the strengthened interdecadal relationship between the western North Pacific summer monsoon(WNPSM)and tropical central-western Pacific sea surface temperature anomaly(SSTA)in summer after the early 1990s.In the first period(1979–91,P1),the WNPSM-related precipitation anomaly and horizontal wind anomaly present themselves as an analogous Pacific-Japan(PJ)-like pattern,generally considered to be related to the Niño-3 index in the preceding winter.During the subsequent period(1994–2019,P2),the WNPSM-related precipitation anomaly presents a zonal dipole pattern,correlated significantly with the concurrent SSTA in the Niño-4 and tropical western Pacific regions.The negative(positive)SSTA in the tropical western Pacific and positive(negative)SSTA in the Niño-4 region,could work together to influence the WNPSM,noting that the two types of anomalous SSTA configurations enhance(weaken)the WNPSM by the positive(negative)phase PJ-like wave and Gill response,respectively,with an anomalous cyclone(anticyclone)located in the WNPSM,which shows obvious symmetry about the anomalous circulation.Specifically,the SSTA in Niño-4 impacts the WNPSM by an atmospheric Gill response,with a stronger(weaker)WNPSM along with a positive(negative)SSTA in the Niño-4 region.Furthermore,the SSTA in the tropical western Pacific exerts an influence on the WNPSM by a PJ-like wave,with a stronger(weaker)WNPSM along with a negative(positive)SSTA in the tropical western Pacific.In general,SSTAs in the tropical western Pacific and Niño-4 areas could work together to exert influence on the WNPSM,with the effect most likely to occur in the El Niño(La Niña)developing year in P2.However,the SSTAs in the tropical western Pacific worked alone to exert an influence on the WNPSM mainly in 2013,2014,2016,and 2017,and the SSTAs in the Niño-4 region worked alone to exert an influence on the WNPSM mainly in Central Pacific(CP)La Niña developing years.The sensitivity experiments also can reproduce the PJ-like wave/Gill response associated with SSTA in the tropical western Pacific/Niño-4 regions.Therefore,the respective and synergistic impacts from the Niño-4 region and the tropical western Pacific on the WNPSM have been revealed,which helps us to acquire a better understanding of the interdecadal variations of the WNPSM and its associated climate influences.展开更多
The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45'S, 156°E. Some characteristic parame...The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45'S, 156°E. Some characteristic parameters of the internal tides are vertical wavenumber -1.6×10^-3 m^-1, horizontal wavenumber (wavelength) 3.3×10^-2 km^-1 (210 km), vertical propagation speed -3.8 cm/s and horizontal propagation speed 2.0 m/s. The waveforms propagate downwards slantingly, that is, the wave energy transfers upwards slantingly. Depth-distribution of the'rotary spectral levels is a saddle-shape. The depths of the trough and the deeper peaks are almost coincident with those of the south boundaries of the South Equatorial Current and the Equatorial Undercurrent, respectively. The mean orientation of the rotary spectral ellipse changes with depth: 30° from north to east at 40 m, and changes into 14° from east to south at 324 m, and generally, it points to northeastward, which indicates "that waves come from the southwest.展开更多
ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provi...ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone (AAC) is a recurrent pattern in post-E1 Nifio summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean- atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind-evaporation-SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor (IPOC) effect explains why E1 Nifio stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20th century and after the 1970s, but not in between. Outstanding issues, including future climate projections, are also discussed.展开更多
Using a statistical model for simulating tropical cyclone (TC) formation and a trajectory model for simulating TC tracks, the influence of the El Nino-Southern Oscillation (ENSO) on the peak-season (July-Septembe...Using a statistical model for simulating tropical cyclone (TC) formation and a trajectory model for simulating TC tracks, the influence of the El Nino-Southern Oscillation (ENSO) on the peak-season (July-September) TC prevailing tracks in the western North Pacific basin is assessed based on 14 selected El Nino and 14 selected La Nina years during the period 1950-2007. It is found that the combination of statistical formation model and a trajectory model can simulate well the primary features of TC prevailing tracks on the interannual timescale. In the El Nino years, the significant enhancement of TC activity primarily occurs south of 20°N, especially east of 130°E. TCs that take the northwestward prevailing track and affect East Asia, including Taiwan Island, the Chinese mainland, Korea, and Japan, tend to move more westward in the El Nino years, while taking a more northward track in the La Nina years. Numerical simulations confirm that the ENSO-related changes in large-scale steering flows and TC formation locations can have a considerable influence on TC prevailing tracks.展开更多
This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-ext...This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-extending,resulting in anomalous high pressure and consequent extreme heat over CSC. The abnormal WNPSH was favored by the warming of the western tropical Pacific(WTP), which was unrelated to ENSO and manifested its own individual effect.The WTP warming enhanced the convection in-situ and led to anomalous high pressure over CSC via a local meridional circulation. The influence of the WTP was confirmed by CAM4 model experiments. A comparison between the 2017 midsummer and 2010 midsummer(with a stronger WNPSH but weaker extreme heat) indicated that the influence of the WNPSH on extreme heat can be modulated by the associated precipitation in the northwestern flank.The role of the WTP was verified by regression analyses on the interannual variation of the WTP sea surface temperature anomaly(SSTA). On the other hand, the WTP has undergone prominent warming during the past few decades, resulting from decadal to long-term changes and favoring extreme warm conditions. Through a mechanism similar to the interannual variation, the decadal to long-term changes have reinforced the influence of WTP warming on the temperature over CSC,contributing to the more frequent hot midsummers recently. It is estimated that more than 50% of the temperature anomaly over CSC in the 2017 midsummer was due to the WTP warming, and 40% was related to the decadal to long-term changes of the WTP SSTA.展开更多
The impact of surface sensible heating over the Tibetan Plateau (SHTP) on the western Pacific subtropical high (WPSH) with and without air-sea interaction was investigated in this study. Data analysis indicated th...The impact of surface sensible heating over the Tibetan Plateau (SHTP) on the western Pacific subtropical high (WPSH) with and without air-sea interaction was investigated in this study. Data analysis indicated that SHTP acts as a relatively independent factor in modulating the WPSH anomaly compared with ENSO events. Stronger spring SHTP is usually fol- lowed by an enhanced and westward extension of the WPSH in summer, and vice versa. Numerical experiments using both an AGCM and a CGCM confirmed that SHTP influences the large-scale circulation anomaly over the Pacific, which features a barotropic anticyclonic response over the northwestern Pacific and a cyclonic response to the south. Owing to different background circulation in spring and summer, such a response facilitates a subdued WPSH in spring but an en- hanced WPSH in summer. Moreover, the CGCM results showed that the equatorial low-level westerly at the south edge of the cyclonic anomaly brings about a warm SST anomaly (SSTA) in the equatorial central Pacific via surface warm advection. Subsequently, an atmospheric Rossby wave is stimulated to the northwest of the warm SSTA, which in turn enhances the at- mospheric dipole anomalies over the western Pacific. Therefore, the air-sea feedbacks involved tend to reinforce the effect of SHTP on the WPSH anomaly, and the role of SHTP on general circulation needs to be considered in a land-air-sea interaction framework.展开更多
The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter (namely, mode station variance percentage) based on 1951-2000 summer rainfall data from 160 stations in Chin...The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter (namely, mode station variance percentage) based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable. The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant (scarce) rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong (weak) heat sources over the eastern Tibetan Plateau, while the abundant (scarce) rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak (strong) heat sources over the tropical western Pacific.展开更多
Since the early or late onset of the South China Sea summer monsoon (SCSM) has a large impact on summer monsoon rainfall in East Asia, the mechanism and process of early or late onset of the SCSM are an worthy issue...Since the early or late onset of the South China Sea summer monsoon (SCSM) has a large impact on summer monsoon rainfall in East Asia, the mechanism and process of early or late onset of the SCSM are an worthy issue to study. In this paper, the results analyzed by using the observed data show that the onset date and process of the SCSM are closely associated with the thermal state of the tropical western Pacific in spring. When the tropical western Pacific is in a warming state in spring, the western Pacific subtropical high shifts eastward, and twin cyclones are early caused over the Bay of Bengal and Sumatra before the SCSM onset. In this case, the cyclonic circulation located over the Bay of Bengal can be early intensified and become into a strong trough. Thus, the westerly flow and convective activity can be intensified over Sumatra, the Indo-China Peninsula and the South China Sea (SCS) in mid-May. This leads to early onset of the SCSM. In contrast, when the tropical western Pacific is in a cooling state, the western Pacific subtropical high anomalously shifts westward, the twin cyclones located over the equatorial eastern Indian Ocean and Sumatra are weakened, and the twin anomaly anticyclones appear over these regions from late April to mid-May. Thus, the westerly flow and convective activity cannot be early intensified over the Indo-China Peninsula and the SCS. Only when the western Pacific subtropical high moves eastward, the weak trough located over the Bay of Bengal can be intensified and become into a strong trough, the strong southwesterly wind and convective activity can be intensified over the Indo-China Peninsula and the SCS in late May. Thus, this leads to late onset of the SCSM. Moreover, in this paper, the influencing mechanism of the thermal state of the tropical western Pacific on the SCSM onset is discussed further from the Walker circulation anomalies in the different thermal states of the tropical western Pacific.展开更多
There is a well-known seesaw pattern of precipitation between the tropical western North Pacific(WNP) and the Yangtze River basin(YRB) during summer. This study identified that this out-of-phase relationship experienc...There is a well-known seesaw pattern of precipitation between the tropical western North Pacific(WNP) and the Yangtze River basin(YRB) during summer. This study identified that this out-of-phase relationship experiences a subseasonal change;that is, the relationship is strong during early summer but much weaker during mid-summer. We investigated the large-scale circulation anomalies responsible for the YRB rainfall anomalies on the subseasonal timescale. It was found that the YRB rainfall is mainly affected by the tropical circulation anomalies during early summer, i.e., the anticyclonic or cyclonic anomaly over the subtropical WNP associated with the precipitation anomalies over the tropical WNP. During mid-summer, the YRB rainfall is mainly affected by the extratropical circulation anomalies in both the lower and upper troposphere. In the lower troposphere, the northeasterly anomaly north of the YRB favors heavier rainfall over the YRB by intensifying the meridional gradient of the equivalent potential temperature over the YRB. In the upper troposphere, the meridional displacement of the Asian westerly jet and the zonally oriented teleconnection pattern along the jet also affect the YRB rainfall. The subseasonal change in the WNP–YRB precipitation relationship illustrated by this study has important implications for the subseasonalto-seasonal forecasting of the YRB rainfall.展开更多
This paper describes the access to, and the content, characteristics, and potential applications of the tropical cyclone(TC) database that is maintained and actively developed by the China Meteorological Administratio...This paper describes the access to, and the content, characteristics, and potential applications of the tropical cyclone(TC) database that is maintained and actively developed by the China Meteorological Administration, with the aim of facilitating its use in scientific research and operational services. This database records data relating to all TCs that have passed through the western North Pacific(WNP) and South China Sea(SCS) since 1949. TC data collection has expanded over recent decades via continuous TC monitoring using remote sensing and specialized field detection techniques,allowing collation of a multi-source TC database for the WNP and SCS that covers a long period, with wide coverage and many observational elements. This database now comprises a wide variety of information related to TCs, such as historical or real-time locations(i.e., best track and landfall), intensity, dynamic and thermal structures, wind strengths, precipitation amounts, and frequency. This database will support ongoing research into the processes and patterns associated with TC climatic activity and TC forecasting.展开更多
This study focuses on the characteristics of the 30 60-day oscillation (MJO) associated with the interannual variability of the thermal state in the western Pacific warm pool. The composite results show that, the ampl...This study focuses on the characteristics of the 30 60-day oscillation (MJO) associated with the interannual variability of the thermal state in the western Pacific warm pool. The composite results show that, the amplitude of MJO convection over the tropical western Pacific tends to intensify (reduce) in the WARM (COLD) case. The negative correlations between MJO convection in the WARM and in the COLD cases are examined to be significant over most of the Asian-Pacific region. The evolutions of MJO convection and lower circulation, on the one hand, exhibit larger differences between the WARM and COLD cases, but on the other hand, display a unique feature in that a well-developed MJO cyclone (anticyclone) is anchored over the Asian-Western Pacific domain at the peak enhanced (suppressed) MJO convection phase over the western Pacific warm pool, either in the WARM or in the COLD case. This unique feature of MJO shows a Gill-type response of lower circulation to the convection and is inferred to be an inherent appearance of MJO. The context in the paper suggests there may exist interactions between MJO and the interannual variability of the thermal state in the western Pacific warm pool.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFC1501604)the National Natural Science Foundation of China(Grant Nos.41875114 and 41875057).
文摘Accurate prediction of tropical cyclone(TC)intensity is challenging due to the complex physical processes involved.Here,we introduce a new TC intensity prediction scheme for the western North Pacific(WNP)based on a time-dependent theory of TC intensification,termed the energetically based dynamical system(EBDS)model,together with the use of a long short-term memory(LSTM)neural network.In time-dependent theory,TC intensity change is controlled by both the internal dynamics of the TC system and various environmental factors,expressed as environmental dynamical efficiency.The LSTM neural network is used to predict the environmental dynamical efficiency in the EBDS model trained using besttrack TC data and global reanalysis data during 1982–2017.The transfer learning and ensemble methods are used to retrain the scheme using the environmental factors predicted by the Global Forecast System(GFS)of the National Centers for Environmental Prediction during 2017–21.The predicted environmental dynamical efficiency is finally iterated into the EBDS equations to predict TC intensity.The new scheme is evaluated for TC intensity prediction using both reanalysis data and the GFS prediction data.The intensity prediction by the new scheme shows better skill than the official prediction from the China Meteorological Administration(CMA)and those by other state-of-art statistical and dynamical forecast systems,except for the 72-h forecast.Particularly at the longer lead times of 96 h and 120 h,the new scheme has smaller forecast errors,with a more than 30%improvement over the official forecasts.
基金supported by the National Natural Science Foundation of China(Grant Nos.42075053 and 41975128)。
文摘Based on the Regional Specialized Meteorological Center(RSMC)Tokyo-Typhoon Center best-track data and the NCEP-NCAR reanalysis dataset,extratropical transitioning(ET)tropical cyclones(ETCs)over the western North Pacific(WNP)during 1951–2021 are classified into six clusters using the fuzzy c-means clustering method(FCM)according to their track patterns.The characteristics of the six hard-clustered ETCs with the highest membership coefficient are shown.Most tropical cyclones(TCs)that were assigned to clusters C2,C5,and C6 made landfall over eastern Asian countries,which severely threatened these regions.Among landfalling TCs,93.2%completed their ET after landfall,whereas 39.8%of ETCs completed their transition within one day.The frequency of ETCs over the WNP has decreased in the past four decades,wherein cluster C5 demonstrated a significant decrease on both interannual and interdecadal timescales with the expansion and intensification of the western Pacific subtropical high(WPSH).This large-scale circulation pattern is favorable for C2 and causes it to become the dominant track pattern,owning to it containing the largest number of intensifying ETCs among the six clusters,a number that has increased insignificantly over the past four decades.The surface roughness variation and three-dimensional background circulation led to C5 containing the maximum number of landfalling TCs and a minimum number of intensifying ETCs.Our results will facilitate a better understanding of the spatiotemporal distributions of ET events and associated environment background fields,which will benefit the effective monitoring of these events over the WNP.
基金supported by the National Natural Science Foundation of China(Grant No.42075015)the Science and Technology Commission of Shanghai Municipality,China(23DZ1204703).
文摘There is limited understanding regarding the formation of multiple tropical cyclones(MTCs).This study explores the environmental conditions conducive to MTC formation by objectively determining the atmospheric circulation patterns favorable for MTC formation over the western North Pacific.Based on 199 MTC events occurring from June to October 1980–2020,four distinct circulation patterns are identified:the monsoon trough(MT)pattern,accounting for 40.3%of occurrences,the confluence zone(CON)pattern at 26.2%,the easterly wave(EW)pattern at 17.8%,and the monsoon gyre(MG)pattern at 15.7%.The MT pattern mainly arises from the interaction between the subtropical high and the monsoon trough,with MTCs forming along the monsoon trough and its flanks.The CON pattern is affected by the subtropical high,the South Asian high,and the monsoon trough,with MTCs emerging at the confluence zone where the prevailing southwesterly and southeasterly flows converge.The EW pattern is dominated by easterly flows,with MTCs developing along the easterly wave train.MTCs in the MG pattern arise within a monsoon vortex characterized by strong southwesterly flows.A quantitative analysis further indicates that MTC formation in the MT pattern is primarily governed by mid-level vertical velocity and low-level vorticity,while mid-level humidity and vertical velocity are significantly important in the other patterns.The meridional shear and convergence of zonal winds are essential in converting barotropic energy from the basic flows to disturbance kinetic energy,acting as the primary source for eddy kinetic energy growth.
基金supported by the National Natural Science Foundation of China[grant number 42275025]the Youth Innovation Promotion Association of the Chinese Academy of Sciences[grant number 2023084].
基金supported by the National Natural Science Foundation of China under Grant No.41988101the Chinese Academy of Sciences under Grant XDA20060102the China Postdoctoral Science Foundation under Grant No.2022T150638 and K.C.Wong Education Foundation.
文摘The unprecedented Zhengzhou heavy rainfall in July 2021 occurred under the background of a northward shift of the western Pacific subtropical high(WPSH).Although the occurrence of this extreme event could not be captured by seasonal predictions,a skillful prediction of the WPSH variation might have warned us of the increased probability of extreme weather events in Central and Northern China.However,the mechanism for the WPSH variation in July 2021 and its seasonal predictability are still unknown.Here,the observed northward shift of the WPSH in July 2021 is shown to correspond to a meridional dipole pattern of the 850-hPa geopotential height to the east of China,the amplitude of which became the strongest since 1979.The meridional dipole pattern is two nodes of the Pacific–Japan pattern.To investigate the predictability of the WPSH variation,a 21-member ensemble of seasonal predictions initiated from the end of June 2021 was conducted.The predictable and unpredictable components of the meridional dipole pattern were identified from the ensemble simulations.Its predictable component is driven by positive precipitation anomalies over the tropical western Pacific.The positive precipitation anomalies are caused by positive horizonal advection of the mean moist enthalpy by southwesterly anomalies to the northwestern flank of anticyclonic anomalies excited by the existing La Niña,which is skillfully predicted by the model.The leading mode of the unpredictable component is associated with the atmospheric internal intraseasonal oscillations,which are not initialized in the simulations.The relative contributions of the predictable and unpredictable components to the observed northward shift of the WPSH at 850 hPa are 28.0%and 72.0%,respectively.
基金This work was supported by the National Natural Science Foundation of China(Grant No:41776031)the National Key Research and Development Program of China(Grant 2018YFC1506903)+1 种基金the team project funding of scientific research innovation for universities in Guangdong province(Grant 2019KCXTF021)the program for scientific research start-up funds of Guangdong Ocean University(Grant R17051).
文摘The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the evolution of the El Niño-Southern Oscillation(ENSO).The possible linkage between the EZW over the western Pacific and the offequatorial monsoonal winds associated with the WNPSM and its decadal changes have not yet been fully understood.Here,we find a non-stationary relationship between the WNPSM and the western Pacific EZW,significantly strengthening their correlation around the late 1980s/early 1990s.This observed shift in the WNPSM–EZW relationship could be explained by the changes in the related sea surface temperature(SST)configurations across the tropical oceans.The enhanced influence from the springtime tropical North Atlantic,summertime tropical central Pacific,and maritime continent SST anomalies may be working together in contributing to the recent intensified WNPSM–EZW co-variability.The observed recent strengthening of the WNPSM–EZW relationship may profoundly impact the climate system,including prompting more effective feedback from the WNPSM on subsequent ENSO evolution and bolstering a stronger biennial tendency of the WNPSM–ENSO coupled system.The results obtained herein imply that the WNPSM,EZW,ENSO,and the tropical North Atlantic SST may be closely linked within a unified climate system with a quasi-biennial rhythm occurring during recent decades,accompanied by a reinforcement of the WNPSM–ENSO interplay quite possibly triggered by enhanced tropical Pacific–Atlantic cross-basin interactions.These results highlight the importance of the tropical Atlantic cross-basin influences in shaping the spatial structure of WNPSM-related wind anomalies and the WNPSM–ENSO interaction.
基金The National Key Research and Development Program of China under contract No.2022YFE0140500the National Natural Science Foundation of China under contract Nos 41821004 and 42130406+2 种基金the National Natural Science Foundation of China-Shandong Joint Fund under contract No.U1906215the Open Fund of Key Laboratory of Ocean Circulation and Waves,Chinese Academy of Sciences under contract No.KLOCW2003the Project of Doctoral Found of Qingdao University of Science and Technology under contract No.210010022746.
文摘As important atmospheric circulation patterns in Northern Hemisphere(NH),the North Atlantic Oscillation(NAO)and the Western Pacific teleconnection(WP)affect the winter climate in Eurasia.In order to explore the combined effects of NAO and WP on East Asian(EA)temperature,the NAO and WP indices are divided into four phases from 1980−2021:the positive NAO and WP phase(NAO+/WP+),the negative NAO and WP phase(NAO−/WP−),the positive NAO and negative WP phase(NAO+/WP−),the negative NAO and positive WP phase(NAO−/WP+).In the phase of NAO+/WP+,the low geopotential height(GH)stays in north of EA at 50°−80°N;the surface air temperature anomaly(SATA)is 0.8−1℃lower than Southern Asian.In the phase of NAO−/WP−,the center of high temperature and GH locate in the northeast of EA;the cold air spreads to Southern Asia,causing the SATA decreases 1−1.5℃.In the phase of NAO+/WP−,the high GH belt is formed at 55°−80°N.Meanwhile,the center of high SATA locates in the north of Asia that increases 0.8−1.1℃.The cold airflow causes temperature dropping 0.5−1℃in the south of EA.The SATA improves 0.5−1.5℃in south of EA in the phase of NAO−/WP+.The belt of high GH is formed at 25°−50°N,and blocks the cold air which from Siberia.The NAO and WP generate two warped plate pressure structures in NH,and affect the temperature by different pressure configurations.NAO and WP form different GH,and GH acts to block and push airflow by affecting the air pressure,then causes the temperature to be different from the north and south of EA.Finally,the multiple linear regression result shows that NAO and WP are weakened by each other such as the phase of NAO+/WP+and NAO−/WP−.
基金supported by the Fund Project of the Hengyang Normal University(2022QD11)the National Natural Science Foundation of China(Grant No.42105063).
文摘This study reveals the strengthened interdecadal relationship between the western North Pacific summer monsoon(WNPSM)and tropical central-western Pacific sea surface temperature anomaly(SSTA)in summer after the early 1990s.In the first period(1979–91,P1),the WNPSM-related precipitation anomaly and horizontal wind anomaly present themselves as an analogous Pacific-Japan(PJ)-like pattern,generally considered to be related to the Niño-3 index in the preceding winter.During the subsequent period(1994–2019,P2),the WNPSM-related precipitation anomaly presents a zonal dipole pattern,correlated significantly with the concurrent SSTA in the Niño-4 and tropical western Pacific regions.The negative(positive)SSTA in the tropical western Pacific and positive(negative)SSTA in the Niño-4 region,could work together to influence the WNPSM,noting that the two types of anomalous SSTA configurations enhance(weaken)the WNPSM by the positive(negative)phase PJ-like wave and Gill response,respectively,with an anomalous cyclone(anticyclone)located in the WNPSM,which shows obvious symmetry about the anomalous circulation.Specifically,the SSTA in Niño-4 impacts the WNPSM by an atmospheric Gill response,with a stronger(weaker)WNPSM along with a positive(negative)SSTA in the Niño-4 region.Furthermore,the SSTA in the tropical western Pacific exerts an influence on the WNPSM by a PJ-like wave,with a stronger(weaker)WNPSM along with a negative(positive)SSTA in the tropical western Pacific.In general,SSTAs in the tropical western Pacific and Niño-4 areas could work together to exert influence on the WNPSM,with the effect most likely to occur in the El Niño(La Niña)developing year in P2.However,the SSTAs in the tropical western Pacific worked alone to exert an influence on the WNPSM mainly in 2013,2014,2016,and 2017,and the SSTAs in the Niño-4 region worked alone to exert an influence on the WNPSM mainly in Central Pacific(CP)La Niña developing years.The sensitivity experiments also can reproduce the PJ-like wave/Gill response associated with SSTA in the tropical western Pacific/Niño-4 regions.Therefore,the respective and synergistic impacts from the Niño-4 region and the tropical western Pacific on the WNPSM have been revealed,which helps us to acquire a better understanding of the interdecadal variations of the WNPSM and its associated climate influences.
基金supported by the National Natural Science Foundation of China[Grant No.41505050]the Open Fund of the Key Laboratory of Ocean Circulation and Waves of the Chinese Academy of Sciences[Grant No.KLOCW1902].
文摘本文分析了El Nino事件衰减速度的差异对衰退年夏季西北太平洋热带气旋(tropical cyclone,TC)频数的不同影响。按照ElNiio事件衰减速度不同,将其划分为迅速衰减(rapid decaying,RD)和缓慢衰减(slowdecaying,SD)的El Nino事件.SD(RD)El Nino事件的衰退年夏季,赤道中东太平洋海温仍维持正异常(衰减为负异常).与SD El Nino事件相比,RDElNino事件衰退年夏季西北太平洋TC频数显著减少.进一步的分析揭示了导致TC频数差异的大尺度环境要素,指出热带印度洋-太平洋海温异常密切相关的西北太平洋低层反气旋异常在其中起到了关键作用。
基金This paper is supported by the National Natural Science Foundation of China(Projects under contracts No.49676275,49976002,40506007)Microwave Imaging National Key Laboratory Foundation(No.51442020103JW1002).
文摘The analyses of a data series obtained during TOGA- COARE show the existence of remarkable semi-diurnal intemal tides in the western equatorial Pacific Ocean around 1°45'S, 156°E. Some characteristic parameters of the internal tides are vertical wavenumber -1.6×10^-3 m^-1, horizontal wavenumber (wavelength) 3.3×10^-2 km^-1 (210 km), vertical propagation speed -3.8 cm/s and horizontal propagation speed 2.0 m/s. The waveforms propagate downwards slantingly, that is, the wave energy transfers upwards slantingly. Depth-distribution of the'rotary spectral levels is a saddle-shape. The depths of the trough and the deeper peaks are almost coincident with those of the south boundaries of the South Equatorial Current and the Equatorial Undercurrent, respectively. The mean orientation of the rotary spectral ellipse changes with depth: 30° from north to east at 40 m, and changes into 14° from east to south at 324 m, and generally, it points to northeastward, which indicates "that waves come from the southwest.
基金supported by the National Basic Research Program of China (Grant No. 2012CB 955600)the U.S. National Science Foundation, the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA11010103)+1 种基金the Environment Research and Technology Development Fund 2-1503 of the Japanese Ministry of Environment, the Japan Society for the Promotion of Science Grant-in-Aid for Scientific Research 25287120 and for Young Scientists 15H05466the National Natural Science Foundation of China (Grant Nos. 41205049, 41275081, 41425019, 41525019, 41521005)
文摘ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone (AAC) is a recurrent pattern in post-E1 Nifio summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean- atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind-evaporation-SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor (IPOC) effect explains why E1 Nifio stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20th century and after the 1970s, but not in between. Outstanding issues, including future climate projections, are also discussed.
基金supported by the Typhoon Research Project (2009CB421503) of the National Basic Research Program (the 973 Program) of Chinathe National Natural Science Foundation of China (NSFCGrant No. 408750387)+2 种基金the Social Commonwealth Research Program of the Ministry of Science and Technology of the People’s Republic of China (GYHY200806009)The research project was funded by the Colleges and Universities in Jiangsu Province Graduate Study Innovation Plan (CX09B 224Z)ZHOU Weican was supported by the Jiangsu Key Laboratory of Meteorological Disaster Pro-gram (KLME 060206)
文摘Using a statistical model for simulating tropical cyclone (TC) formation and a trajectory model for simulating TC tracks, the influence of the El Nino-Southern Oscillation (ENSO) on the peak-season (July-September) TC prevailing tracks in the western North Pacific basin is assessed based on 14 selected El Nino and 14 selected La Nina years during the period 1950-2007. It is found that the combination of statistical formation model and a trajectory model can simulate well the primary features of TC prevailing tracks on the interannual timescale. In the El Nino years, the significant enhancement of TC activity primarily occurs south of 20°N, especially east of 130°E. TCs that take the northwestward prevailing track and affect East Asia, including Taiwan Island, the Chinese mainland, Korea, and Japan, tend to move more westward in the El Nino years, while taking a more northward track in the La Nina years. Numerical simulations confirm that the ENSO-related changes in large-scale steering flows and TC formation locations can have a considerable influence on TC prevailing tracks.
基金supported by National Key R&D Program of China (Grant No. 2016YFA0600601)the National Natural Science Foundation of China (Grant Nos. 41605027, 41721004, 41530530 and 41731173)+1 种基金the Leading Talents of Guangdong Province Program, the Pioneer Hundred Talents Program of the Chinese Academy of Sciencesthe Fundamental Research Funds for the Central Universities
文摘This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-extending,resulting in anomalous high pressure and consequent extreme heat over CSC. The abnormal WNPSH was favored by the warming of the western tropical Pacific(WTP), which was unrelated to ENSO and manifested its own individual effect.The WTP warming enhanced the convection in-situ and led to anomalous high pressure over CSC via a local meridional circulation. The influence of the WTP was confirmed by CAM4 model experiments. A comparison between the 2017 midsummer and 2010 midsummer(with a stronger WNPSH but weaker extreme heat) indicated that the influence of the WNPSH on extreme heat can be modulated by the associated precipitation in the northwestern flank.The role of the WTP was verified by regression analyses on the interannual variation of the WTP sea surface temperature anomaly(SSTA). On the other hand, the WTP has undergone prominent warming during the past few decades, resulting from decadal to long-term changes and favoring extreme warm conditions. Through a mechanism similar to the interannual variation, the decadal to long-term changes have reinforced the influence of WTP warming on the temperature over CSC,contributing to the more frequent hot midsummers recently. It is estimated that more than 50% of the temperature anomaly over CSC in the 2017 midsummer was due to the WTP warming, and 40% was related to the decadal to long-term changes of the WTP SSTA.
基金supported jointly by the National Natural Science Foundation of China(Grant No.91337216)the Special Fund for Public Welfare Industry(Meteorology),administered by the Chinese Ministry of Finance and the Ministry of Science and Technology(Grant No.GYHY201406001)the CAS XDA(Grant No.11010402)
文摘The impact of surface sensible heating over the Tibetan Plateau (SHTP) on the western Pacific subtropical high (WPSH) with and without air-sea interaction was investigated in this study. Data analysis indicated that SHTP acts as a relatively independent factor in modulating the WPSH anomaly compared with ENSO events. Stronger spring SHTP is usually fol- lowed by an enhanced and westward extension of the WPSH in summer, and vice versa. Numerical experiments using both an AGCM and a CGCM confirmed that SHTP influences the large-scale circulation anomaly over the Pacific, which features a barotropic anticyclonic response over the northwestern Pacific and a cyclonic response to the south. Owing to different background circulation in spring and summer, such a response facilitates a subdued WPSH in spring but an en- hanced WPSH in summer. Moreover, the CGCM results showed that the equatorial low-level westerly at the south edge of the cyclonic anomaly brings about a warm SST anomaly (SSTA) in the equatorial central Pacific via surface warm advection. Subsequently, an atmospheric Rossby wave is stimulated to the northwest of the warm SSTA, which in turn enhances the at- mospheric dipole anomalies over the western Pacific. Therefore, the air-sea feedbacks involved tend to reinforce the effect of SHTP on the WPSH anomaly, and the role of SHTP on general circulation needs to be considered in a land-air-sea interaction framework.
基金This work was supported by the National Key Program for Developing Basic Research (Grant No. 2004CB418303)the National Natural Science Foundation of China (Grant No. 40175018).
文摘The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter (namely, mode station variance percentage) based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable. The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant (scarce) rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong (weak) heat sources over the eastern Tibetan Plateau, while the abundant (scarce) rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak (strong) heat sources over the tropical western Pacific.
基金the National Natural Science Foundation of China grant No.40575026 "National Key ProgTamme for Developing Basic Science" Projects 2004CB418303, 2006CB403600.
文摘Since the early or late onset of the South China Sea summer monsoon (SCSM) has a large impact on summer monsoon rainfall in East Asia, the mechanism and process of early or late onset of the SCSM are an worthy issue to study. In this paper, the results analyzed by using the observed data show that the onset date and process of the SCSM are closely associated with the thermal state of the tropical western Pacific in spring. When the tropical western Pacific is in a warming state in spring, the western Pacific subtropical high shifts eastward, and twin cyclones are early caused over the Bay of Bengal and Sumatra before the SCSM onset. In this case, the cyclonic circulation located over the Bay of Bengal can be early intensified and become into a strong trough. Thus, the westerly flow and convective activity can be intensified over Sumatra, the Indo-China Peninsula and the South China Sea (SCS) in mid-May. This leads to early onset of the SCSM. In contrast, when the tropical western Pacific is in a cooling state, the western Pacific subtropical high anomalously shifts westward, the twin cyclones located over the equatorial eastern Indian Ocean and Sumatra are weakened, and the twin anomaly anticyclones appear over these regions from late April to mid-May. Thus, the westerly flow and convective activity cannot be early intensified over the Indo-China Peninsula and the SCS. Only when the western Pacific subtropical high moves eastward, the weak trough located over the Bay of Bengal can be intensified and become into a strong trough, the strong southwesterly wind and convective activity can be intensified over the Indo-China Peninsula and the SCS in late May. Thus, this leads to late onset of the SCSM. Moreover, in this paper, the influencing mechanism of the thermal state of the tropical western Pacific on the SCSM onset is discussed further from the Walker circulation anomalies in the different thermal states of the tropical western Pacific.
基金supported by the National Natural Science Foundation of China (Grant No. 41320104007)
文摘There is a well-known seesaw pattern of precipitation between the tropical western North Pacific(WNP) and the Yangtze River basin(YRB) during summer. This study identified that this out-of-phase relationship experiences a subseasonal change;that is, the relationship is strong during early summer but much weaker during mid-summer. We investigated the large-scale circulation anomalies responsible for the YRB rainfall anomalies on the subseasonal timescale. It was found that the YRB rainfall is mainly affected by the tropical circulation anomalies during early summer, i.e., the anticyclonic or cyclonic anomaly over the subtropical WNP associated with the precipitation anomalies over the tropical WNP. During mid-summer, the YRB rainfall is mainly affected by the extratropical circulation anomalies in both the lower and upper troposphere. In the lower troposphere, the northeasterly anomaly north of the YRB favors heavier rainfall over the YRB by intensifying the meridional gradient of the equivalent potential temperature over the YRB. In the upper troposphere, the meridional displacement of the Asian westerly jet and the zonally oriented teleconnection pattern along the jet also affect the YRB rainfall. The subseasonal change in the WNP–YRB precipitation relationship illustrated by this study has important implications for the subseasonalto-seasonal forecasting of the YRB rainfall.
基金supported by the Key Projects of the National Key R&D Program (Grant No. 2018YFC1506300)the Key Program for International S&T Cooperation Projects of China (Grant No. 2017YFE0107700)。
文摘This paper describes the access to, and the content, characteristics, and potential applications of the tropical cyclone(TC) database that is maintained and actively developed by the China Meteorological Administration, with the aim of facilitating its use in scientific research and operational services. This database records data relating to all TCs that have passed through the western North Pacific(WNP) and South China Sea(SCS) since 1949. TC data collection has expanded over recent decades via continuous TC monitoring using remote sensing and specialized field detection techniques,allowing collation of a multi-source TC database for the WNP and SCS that covers a long period, with wide coverage and many observational elements. This database now comprises a wide variety of information related to TCs, such as historical or real-time locations(i.e., best track and landfall), intensity, dynamic and thermal structures, wind strengths, precipitation amounts, and frequency. This database will support ongoing research into the processes and patterns associated with TC climatic activity and TC forecasting.
基金supported by the National Natural Science Foundation of China under Grant No.40275013the National Key Programme for Developing Basic Sciences(G1998040900-part 1)LASG,Institute of Atmospheric Physics,Chinese Academy of Sciences.
文摘This study focuses on the characteristics of the 30 60-day oscillation (MJO) associated with the interannual variability of the thermal state in the western Pacific warm pool. The composite results show that, the amplitude of MJO convection over the tropical western Pacific tends to intensify (reduce) in the WARM (COLD) case. The negative correlations between MJO convection in the WARM and in the COLD cases are examined to be significant over most of the Asian-Pacific region. The evolutions of MJO convection and lower circulation, on the one hand, exhibit larger differences between the WARM and COLD cases, but on the other hand, display a unique feature in that a well-developed MJO cyclone (anticyclone) is anchored over the Asian-Western Pacific domain at the peak enhanced (suppressed) MJO convection phase over the western Pacific warm pool, either in the WARM or in the COLD case. This unique feature of MJO shows a Gill-type response of lower circulation to the convection and is inferred to be an inherent appearance of MJO. The context in the paper suggests there may exist interactions between MJO and the interannual variability of the thermal state in the western Pacific warm pool.