The simulation characteristics of the seasonal evolution of subtropical anticyclones in the Northern Hemisphere are documented for the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2...The simulation characteristics of the seasonal evolution of subtropical anticyclones in the Northern Hemisphere are documented for the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, the Institute of Atmospheric Physics. An understanding of the seasonal evolution of the subtropical anticyclones is also addressed. Compared with the global analysis established by the European Centre for Medium-Range Forecasts, the ERA-40 global reanalysis data, the general features of subtropical anticyclones and their evolution are simulated well in both winter and summer, while in spring a pronounced bias in the generation of the South Asia Anticyclone（SAA） exists. Its main deviation in geopotential height from the reanalysis is consistent with the bias of temperature in the troposphere. It is found that condensation heating （CO） plays a dominant role in the seasonal development of the SAA and the subtropical anticyclone over the western Pacific （SAWP） in the middle troposphere. The CO biases in the model account for the biases in the establishment of the SAA in spring and the weaker strength of the SAA and the SAWP from spring to summer. CO is persistently overestimated in the central-east tropical Pacific from winter to summer, while it is underestimated over the area from the South China Sea to the western Pacific from spring to summer. Such biases generate an illusive anticyclonic gyre in the upper troposphere above the middle Pacific and delay the generation of the SAA over South Asia in April. In mid- summer, the simulated SAA is located farther north than in the ERA-40 data owing to excessively strong surface sensible heating （SE） to the north of the Tibetan Plateau. Whereas, the two surface subtropical anticyclones in the eastern oceans during spring to summer are controlled mainly by the surface SE over the two continents in the Northern Hemisphere, which are simulated reasonably well, albeit with their centers shifted westwards owing to the weaker longwave radiation cooling in the simulation associated with much weaker local stratiform cloud. Further improvements in the related parameterization of physical processes are therefore identified.展开更多
This study investigates the distinct impacts of eastern Pacific(EP)and central Pacific(CP)El Niño events on winter shortwave solar radiation(SSR)in southern China,revealing different spatial distributions and und...This study investigates the distinct impacts of eastern Pacific(EP)and central Pacific(CP)El Niño events on winter shortwave solar radiation(SSR)in southern China,revealing different spatial distributions and underlying mechanisms.The results show that,during the developing winter of EP El Niño,significant SSR reductions occur in southwestern China and the east coast of southern China due to a strong,zonally extended Northwest Pacific anticyclone that transports moisture from the tropical Northwest Pacific and North Indian Ocean,while the northeast of southern China experiences a weak increase in SSR.In contrast,during the developing winter of CP El Niño,SSR decreases in the east of southern China with a significant decrease in the lower basin of the Yangtze River but an increase in the west of southern China with a remarkable increase in eastern Yunnan.The pronounced east-west dipole pattern in SSR anomalies is driven by a meridionally elongated Northwest Pacific anticyclone,which enhances northward moisture transport to the east of southern China while leaving western areas drier.Further research reveals that distinct moisture anomalies during the developing winter of EP and CP events result in divergent SSR distributions across southern China,primarily through modulating the total cloud cover.These findings highlight the critical need to differentiate between El Niño types when predicting medium and long-term variability of radiation in southern China.展开更多
Four observed blocking anticyclones in different regions of the Northern Hemisphere are in- vestigated.Analyses show that there exist distinct differences in the maintenance of the time-mean quasi-geostrophic potentia...Four observed blocking anticyclones in different regions of the Northern Hemisphere are in- vestigated.Analyses show that there exist distinct differences in the maintenance of the time-mean quasi-geostrophic potential vorticity(PV)low in 300 hPa within blocking areas.In two Pacific blocking cases,the PV advection by time-mean flow tends to flow the PV low to northwestern part of the blocking highs,and thus is beneficial to the maintenance of the blockings'strength.The transfer by transient eddies acts to balance the effect of the time-mean flow.In the Atlantic and Alaska blocking cases,however,the advection of mean flow tends to flow the PV low eastward. The PV transfer by transient eddies acts to flow potential vorticity low to the western part of the blocking ridges and also to balance the time-mean flow's effect.Thus,in the latter two cases,it is the transfer by the transient eddies that acts to maintain the blockings.展开更多
This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During...This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During Y0,monsoon precipitation surpasses climatological values,presenting a tripole spatial pattern,whereas Y1 is characterized by below-normal precipitation with a dipole pattern.In certain regions,the difference in precipitation between Y0 and Y1 reaches up to 3 mm day–1.This work provides further insight into the key tropical ocean regions driving the precipitation distinction,and elucidates their coupling mechanisms with large-scale atmospheric circulation anomalies.Influenced by the development of earlier ocean-atmosphere anomaly patterns,the Tropical Indian Ocean and Western Pacific(TIO-WP)warming(cooling)is significant during the summer of Y0(Y1).The elevated sea surface temperature(SST)in Y0 supports an anomalous Western North Pacific(WNP)anticyclone via a Kelvin-wave-induced Ekman divergence mechanism.This anomalous anticyclone intensifies the suppressed convection over the WNP,which results in increased divergence in the upper-level troposphere over the Indian Ocean and South Asian regions,thereby boosting convection.Simultaneously,the easterly winds associated with the strengthened equatorial latitude SST anomaly(SSTA)gradient and the anomalous anticyclone intensified,transporting a large amount of water vapor to the west.The combined moisture and dynamic conditions support the enhanced precipitation in the South Asian region.展开更多
In this paper, the case of Jupiter being found in hydrodynamic equilibrium is for the first time investigated solely by mathematical methods. With the help of the hydrodynamic method, formulas of energy balance for ov...In this paper, the case of Jupiter being found in hydrodynamic equilibrium is for the first time investigated solely by mathematical methods. With the help of the hydrodynamic method, formulas of energy balance for oval and vortex are found, which are summed as permanent kinetic energy and constantly provide equilibrium for the stable rotational movements of Jupiter. To find the total kinetic energy of the oval and vortex in turbulent mode, Green’s function methods with special definitions and flow functions that describe the movement of the vortex are applied. The results are expressed in lemmas and theorems. For the hydrodynamic equilibrium of Jupiter, the necessary and sufficient conditions for the preservation of the cyclone and the anticyclone are mentioned. The relationships between the angular velocity and the gradient of pressure and the Corolias parameter are also given. The Rossby number is given for steady rotational motion. These facts show the existence of necessary and sufficient conditions for maintaining the stability of rotational motion and prove the hydrodynamic equilibrium of Jupiter. In this case using stream function and constructing generalized Green’s function and accordance energy conservation laws, the hydrodynamic equilibrium of Jupiter is proved.展开更多
The given investigation presents the results of estimating the water circulation in the water area of the Bering Sea and the Sea of Okhotsks, considering the influence of various types of the atmospheric processes. To...The given investigation presents the results of estimating the water circulation in the water area of the Bering Sea and the Sea of Okhotsks, considering the influence of various types of the atmospheric processes. To solve the given problem it is used a hydrodynamic model calculating the integral functions of the flow from the surface to the bottom. By results of calculations, the maps of the integral water circulation were built for the following types of atmospheric circulation： ＂north-western＂ and ＂okhotsk-aleutian＂. In accordance with the performed calculations for the water area being studied, the hydrodynamic structures are distinguished both non-depending and depending on the type of the atmospheric circulation. The non-depending structures are characterized by the cyclonic activity in the Bering Sea and the Sea of Okhotsk in whole. Hydrodynamic structures depending on types of the atmospheric circulation have their peculiarities in the spatial-temporal distribution.展开更多
The climatic features associated with the eastern China summer rainfalls (ECSR) are examined in the National Center for Atmospheric Research (NCAR) Community Climate Model Version 3 (CCM3) of the United States of Amer...The climatic features associated with the eastern China summer rainfalls (ECSR) are examined in the National Center for Atmospheric Research (NCAR) Community Climate Model Version 3 (CCM3) of the United States of America, and run with time-evolving sea surface temperature (SST) from September 1978 to August 1993. The CCM3 is shown to capture the salient seasonal features of ECSR. As many other climate models, however, there are some unrealistic projections of ECSR in the CCM3. The most unacceptable one is the erroneously intensified precipitation center on the east periphery of the Tibetan Plateau and its northeastward extension. The artificial strong rainfall center is fairly assessed by comparing with the products of the station rainfall data, Xie and Arkin (1996) rainfall data and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (Gibson et al., 1997). The physical processes involved in the formation of the rainfall center are discussed. The preliminary conclusion reveals that it is the overestimated sensible heating over and around the Tibetan Plateau in the CCM3 that causes the heavy rainfall. The unreal strong surface sensible heating over the southeast and northeast of Tibetan Plateau favors the forming of a powerful subtropical anticyclone over the eastern China. The fake enclosed subtropical anticyclone center makes the moist southwest wind fasten on the east periphery of the Tibetan Plateau and extend to its northeast. In the southeast coast of China, locating on the southeast side of the subtropical anticyclone, the southwest monsoon is decreased and even replaced by northeast wind in some cases. In the CCM3, therefore, the precipitation is exaggerated on the east periphery of the Tibetan Plateau and its northeast extension and is underestimated in the southeast coast of China. Key words Eastern China summer rainfall - Model validation - Subtropical anticyclone - Diabatic heating This study was sponsored by Chinese Academy of Sciences under grant “ Hundred Talents” for “ Validation of Coupled Climate models” and the National Natural Science Foundation of China (Grant No.49823002), and IAP innovation fund (No. 8-1204).展开更多
ENSO＇s effect on the rainfall in eastern China in the following early summer is investigated by using station precipitation data and the ERA-40 reanalysis data from 1958 to 2002. In June, after the E1 Nifio peak, the...ENSO＇s effect on the rainfall in eastern China in the following early summer is investigated by using station precipitation data and the ERA-40 reanalysis data from 1958 to 2002. In June, after the E1 Nifio peak, the precipitation is significantly enhanced in the Yangtze River valley while suppressed in the Huaihe River-Yellow River valleys. This relationship between ENSO and the rainfall in eastern China is established possibly through two teleconnections： One is related to the western North Pacific （WNP） anticyclonic anomaly in the lower troposphere leading to enhanced precipitation in the Yangtze River valley, and the other is related to the southward displacement of the Asian jet stream （AJS） in the upper troposphere resulting in suppressed precipitation in the Huaihe River-Yellow River valleys. This southward displacement of the AJS is one part of ENSO＇s effect on the zonal flow in the whole Northern Hemisphere. After the E1 Nifio peak, the ENSO-related warming in the tropical troposphere persists into the following early summer, increasing the meridional temperature gradient and through the thermal wind balance, leads to the enhancement of westerly flow in the subtropics south of the westerly jet stream and results in a southward displacement of the westerly jet stream.展开更多
In this study, high-resolution temperature and salinity data obtained from three Sea-Wing underwater gliders were used together with satellite altimeter data to track the vertical thermohaline structure of an anticycl...In this study, high-resolution temperature and salinity data obtained from three Sea-Wing underwater gliders were used together with satellite altimeter data to track the vertical thermohaline structure of an anticyclonic eddy that originated from the loop current of the Kuroshio southwest of Taiwan, China. One of the gliders crossed the entire eddy and it observed a remarkable warm anomaly of as much as 3.9℃ extending to 500 dbar from the base of the mixed layer. Conversely, a positive salinity anomaly was found to be above 200 dbar only in the anticyclonic eddy, with a maximum value of >0.5 in the mixed layer. Below the mixed layer, water of higher salinity (>34.7) was found, which could have been preserved through constrained vertical mixing within the anticyclonic eddy. The salinity in the upper layer of the anticyclonic eddy was much similar to that of the northwestern Pacific Ocean than the northern South China Sea, reflecting Kuroshio intrusion with anticyclonic eddy shedding from the loop current.展开更多
Based on NCEP/NCAR reanalysis data, the interdecadal variability of Hadley circulation （HC） and its association with East Asian temperature in winter are investigated. Results indicate that the Northern Hemisphere w...Based on NCEP/NCAR reanalysis data, the interdecadal variability of Hadley circulation （HC） and its association with East Asian temperature in winter are investigated. Results indicate that the Northern Hemisphere winter HC underwent apparent change in the 1970s, with transition occurring around 1976/77. Along with interdecadal variability of HC, its linkage to surface air temperature （SAT） in East Asia also varied decadally, from weak relations to strong relations. Such a change may be related to the interaction between HC and the atmospheric circulation system over the Philippines, which is associated with the East Asian winter monsoon （EAWM）. Before the 1970s, the connection between HC and the anticyclonic circulation around the Philippines was insignificant, but after the late 1970s their linkage entered a strong regime. The intensification of this connection may therefore be responsible for the strong relations between HC and East Asian winter temperatures after the late 1970s.展开更多
The studies in China on the formation of the summertime subtropical anticyclone on the climate timescale are reviewed. New insights in resent studies are introduced. It is stressed that either in the free atmosphere o...The studies in China on the formation of the summertime subtropical anticyclone on the climate timescale are reviewed. New insights in resent studies are introduced. It is stressed that either in the free atmosphere or in the planetary boundary, the descending arm of the Hadley cell cannot be considered as a mechanism for the formation of the subtropical anticyclone. Then the theories of thermal adaptation of the atmosphere to external thermal forcing and the potential vorticity forcing are developed to understand the formation of the subtropical anticyclone in the three-dimensional domain. Numerical experiments are designed to verify these theories. Results show that in the boreal summer, the formation of the strong South Asian High in the upper troposphere and the subtropical anticyclone over the western Pacific in the middle and lower troposphere is, to a great extent, due to the convective latent heating associated with the Asian monsoon, but affected by orography and the surface sensible heating over the continents. On the other hand, the formation of the subtropical anticyclone at the surface over the northern Pacific and in the upper troposphere over North America is mainly due to the strong surface sensible heating over North America, but affected by radiation cooling over the eastern North Pacific. Moreover, in the real atmosphere such individual thermal forcing is well organized. By considering the different diabatic heating in synthesis, a quadruple heating pattern is found over each subtropical continent and its adjacent oceans in summer. A distinct circulation pattern accompanies this heating pattern. The global summer subtropical heating and circulation may be viewed as 'mosaics' of such quadruplet heating and circulation patterns respectively. At last, some important issues for further research in understanding and predicting the variations of the subtropical anticyclone are raised.展开更多
The Asian summer monsoon （ASM） anticyclone is a dominant feature of the circulation in the upper troposphere- lower stratosphere （UTLS） during boreal summer, which is found to have persistent maxima in carbon mono...The Asian summer monsoon （ASM） anticyclone is a dominant feature of the circulation in the upper troposphere- lower stratosphere （UTLS） during boreal summer, which is found to have persistent maxima in carbon monoxide （CO）. This enhancement is due to the upward transport of air with high CO from the planetary boundary layer （PBL）, and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting （WRF） with chemistry model （WRF- Chem）. According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result is mainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.展开更多
Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley(YRV)in June-July(JJ)2020.An observational data analysis has indicated that the strong and persistent rainfall arose from the co...Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley(YRV)in June-July(JJ)2020.An observational data analysis has indicated that the strong and persistent rainfall arose from the confluence of southerly wind anomalies to the south associated with an extremely strong anomalous anticyclone over the western North Pacific(WNPAC)and northeasterly anomalies to the north associated with a high-pressure anomaly over Northeast Asia.A further observational and modeling study has shown that the extremely strong WNPAC was caused by both La Niña-like SST anomaly(SSTA)forcing in the equatorial Pacific and warm SSTA forcing in the tropical Indian Ocean(IO).Different from conventional central Pacific(CP)El Niños that decay slowly,a CP El Niño in early 2020 decayed quickly and became a La Niña by early summer.This quick transition had a critical impact on the WNPAC.Meanwhile,an unusually large area of SST warming occurred in the tropical IO because a moderate interannual SSTA over the IO associated with the CP El Niño was superposed by an interdecadal/long-term trend component.Numerical sensitivity experiments have demonstrated that both the heating anomaly in the IO and the heating anomaly in the tropical Pacific contributed to the formation and maintenance of the WNPAC.The persistent high-pressure anomaly in Northeast Asia was part of a stationary Rossby wave train in the midlatitudes,driven by combined heating anomalies over India,the tropical eastern Pacific,and the tropical Atlantic.展开更多
In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anti...In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anticyclonic)eddies associated with warm(cold)cores in the South China Sea(SCS).These"abnormal"eddies pose a challenge to previous works on eddy detection,characteristic analysis,eddy-induced heat and salt transports,and even on mesoscale eddy dynamics.Based on a 9-year(2000–2008)numerical modelling data,the cyclonic warm-core eddies(CWEs)and anticyclonic cold-core eddies(ACEs)in the SCS are analyzed.This study found that the highest incidence area of the"abnormal"eddies is the northwest of Luzon Strait.In terms of the eddy snapshot counting method,8620 CWEs and 9879 ACEs are detected,accounting for 14.6%and 15.8%of the total eddy number,respectively.The size of the"abnormal"eddies is usually smaller than that of the"normal"eddies,with the radius only around 50 km.In the generation time aspect,they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan.The survival time of CWEs(ACEs)occupies 16.3%(17.1%)of the total eddy lifespan.Based on two case studies,the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these"abnormal"eddies near the northeastern SCS.展开更多
Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event. By analyzing the monthly data of HadISST from 1950 to 2007, it shows that the interannual component of SST anomalies p...Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event. By analyzing the monthly data of HadISST from 1950 to 2007, it shows that the interannual component of SST anomalies peak approximately 10 months after SST anomalies peak in the eastern equatorial Pacific. As the ENSO event progresses, the positive SST anomalies spread throughout the China seas and eastward along the Kuroshio extension. Atmospheric reanalysis data demonstrate that changes in the net surface heat flux entering into the China seas are responsible for the SST variability. During E1 Nifio, the western north Pacific anticyclone is generated, with anomalous southwester lies prevailing along the East Asian coast. This anticyclone reduces the mean surface wind speed which decreases the surface heat flux and then increases the SST. The delays between the developing of this anticyclone and the south Indian Ocean anticyclone with approximately 3-6 months cause the 2-3 months lag of the surface heat flux between the China seas and the Indian Ocean. The northwestern Pacific anticyclone is the key process bridging the warming in the eastern equatorial Pacific and that in the China seas.展开更多
In summer 2020,extreme rainfall occurred throughout the Yangtze River basin,Huaihe River basin,and southern Yellow River basin,which are defined here as the central China(CC)region.However,only a weak central Pacific(...In summer 2020,extreme rainfall occurred throughout the Yangtze River basin,Huaihe River basin,and southern Yellow River basin,which are defined here as the central China(CC)region.However,only a weak central Pacific(CP)El Niño happened during winter 2019/20,so the correlations between the El Niño–Southern Oscillation(ENSO)indices and ENSO-induced circulation anomalies were insufficient to explain this extreme precipitation event.In this study,reanalysis data and numerical experiments are employed to identify and verify the primary ENSO-related factors that cause this extreme rainfall event.During summer 2020,unusually strong anomalous southwesterlies on the northwest side of an extremely strong Northwest Pacific anticyclone anomaly(NWPAC)contributed excess moisture and convective instability to the CC region,and thus,triggered extreme precipitation in this area.The tropical Indian Ocean(TIO)has warmed in recent decades,and consequently,intensified TIO basinwide warming appears after a weak El Niño,which excites an extremely strong NWPAC via the pathway of the Indo-western Pacific Ocean capacitor(IPOC)effect.Additionally,the ENSO event of 2019/20 should be treated as a fast-decaying CP El Niño rather than a general CP El Niño,so that the circulation and precipitation anomalies in summer 2020 can be better understood.Last,the increasing trend of tropospheric temperature and moisture content in the CC region after 2000 is also conducive to producing heavy precipitation.展开更多
This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China （NEC） and their associated atmospheric circulation anomalies. It is shown that the first ...This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China （NEC） and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC （referred to as the south mode）, whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC （referred to as the north mode）. Further findings reveal that, through modulating moisture transportation and upper- and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC＇s northern and western boundal＇ies. Furthermore, the north （south） mode is strongly related to the intensity （meridional shift） of the East Asian westerly jet.展开更多
A robust anomalous anticyclonic circulation (AAC) was observed over Northeast Asia and the Japan Sea in boreal win-ter 1997/98 and over the Japan Sea in spring 1998. The formation mechanism is investigated. On the bac...A robust anomalous anticyclonic circulation (AAC) was observed over Northeast Asia and the Japan Sea in boreal win-ter 1997/98 and over the Japan Sea in spring 1998. The formation mechanism is investigated. On the background of the vertically sheared winter monsoonal flow, anomalous rainfall in the tropical Indo-Western Pacific warm pool excited a wave train towards East Asia in the upper troposphere during boreal winter of 1997/98. The AAC over Northeast Asia and the Japan Sea is part of the wave train of equivalent barotropic structure. The AAC over the Japan Sea persisted from winter to spring and even intensified in spring 1998. The diagnostic calculations show that the vorticity and temperature fluxes by synoptic eddies are an important mechanism for the AAC over the Japan Sea in spring 1998.展开更多
The relationship between sea surface temperature anomaly (SSTA) in the domain from the northwest of the Pacific to China seas (NWP-CS) and climate (precipitation and surface temperature) anomaly in winters over east ...The relationship between sea surface temperature anomaly (SSTA) in the domain from the northwest of the Pacific to China seas (NWP-CS) and climate (precipitation and surface temperature) anomaly in winters over east of Chinese Mainland (ECM) are investigated with composite analysis. The results suggest that (1) SSTA in NWP-CS usually appears as 'seesaw' pattern, i.e., sign of SSTA in the northwest of the Philippines is positive (negative) while in the southeast it is negative (positive), defined as SSTA 'seesaw' positive (negative) pattern. When SSTA 'seesaw' positive (negative) pattern appears, the surface temperature in ECM is higher (lower) than the normal winters but the precipitation anomaly is not distinct ; (2) there are two anomalous anticyclones (cyclones) locating in the northwest Pacific and east of the Philippines at 850 hPa level and an anomalous anti-Hadley (Hadley) circulation, which descends (ascends) south of 18oN, ascends (descends) north of 18oN; (3) heat flux anomaly from ocean into atmosphere is weaker (stronger) in the northwest of the Philippines but stronger (weaker) in the southeast of the Philippines than the normal winters, because the weaker (stronger) northerly prevails in the northwest of the Philippines and stronger (weaker) northeaster in the southeast of the Philippines induced by anomalous anticyclones (cyclones).展开更多
To better understand the relationship between anticyclones in Siberia and cold-air activities and temperature changes in East Asia,this study proposes a 2D anticyclone identification method based on a deep-learning mo...To better understand the relationship between anticyclones in Siberia and cold-air activities and temperature changes in East Asia,this study proposes a 2D anticyclone identification method based on a deep-learning model,Mask R-CNN,which can reliably detect the changes in the morphological characteristics of anticyclones.Using the new method,the authors identified the southeastward-extending Siberian cold high(SEESCH),which greatly affects wintertime temperatures in China.This type of cold high is one of the main synoptic systems(45.7%)emerging from Siberia in winter.Cold air carried by SEESCH has a significant negative correlation with the temperature changes in the downstream area,and 52% of SEESCHs are accompanied by cold-air accumulation in North and East China,which has a significant impact on regional cooling.These results provide clues for studying the interconnection between SEESCHs and extreme cold events.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40925015)the CAS Strategic Priority Research Program(Grant No.XDA01020303)the National Program on Key Basic Research Project(Grant No.2010CB950400)
文摘The simulation characteristics of the seasonal evolution of subtropical anticyclones in the Northern Hemisphere are documented for the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, the Institute of Atmospheric Physics. An understanding of the seasonal evolution of the subtropical anticyclones is also addressed. Compared with the global analysis established by the European Centre for Medium-Range Forecasts, the ERA-40 global reanalysis data, the general features of subtropical anticyclones and their evolution are simulated well in both winter and summer, while in spring a pronounced bias in the generation of the South Asia Anticyclone（SAA） exists. Its main deviation in geopotential height from the reanalysis is consistent with the bias of temperature in the troposphere. It is found that condensation heating （CO） plays a dominant role in the seasonal development of the SAA and the subtropical anticyclone over the western Pacific （SAWP） in the middle troposphere. The CO biases in the model account for the biases in the establishment of the SAA in spring and the weaker strength of the SAA and the SAWP from spring to summer. CO is persistently overestimated in the central-east tropical Pacific from winter to summer, while it is underestimated over the area from the South China Sea to the western Pacific from spring to summer. Such biases generate an illusive anticyclonic gyre in the upper troposphere above the middle Pacific and delay the generation of the SAA over South Asia in April. In mid- summer, the simulated SAA is located farther north than in the ERA-40 data owing to excessively strong surface sensible heating （SE） to the north of the Tibetan Plateau. Whereas, the two surface subtropical anticyclones in the eastern oceans during spring to summer are controlled mainly by the surface SE over the two continents in the Northern Hemisphere, which are simulated reasonably well, albeit with their centers shifted westwards owing to the weaker longwave radiation cooling in the simulation associated with much weaker local stratiform cloud. Further improvements in the related parameterization of physical processes are therefore identified.
基金funded by a Project from China Southern Power Grid Company Ltd.(Nos.ZBKJXM20232481 and ZBKJXM20232482)。
文摘This study investigates the distinct impacts of eastern Pacific(EP)and central Pacific(CP)El Niño events on winter shortwave solar radiation(SSR)in southern China,revealing different spatial distributions and underlying mechanisms.The results show that,during the developing winter of EP El Niño,significant SSR reductions occur in southwestern China and the east coast of southern China due to a strong,zonally extended Northwest Pacific anticyclone that transports moisture from the tropical Northwest Pacific and North Indian Ocean,while the northeast of southern China experiences a weak increase in SSR.In contrast,during the developing winter of CP El Niño,SSR decreases in the east of southern China with a significant decrease in the lower basin of the Yangtze River but an increase in the west of southern China with a remarkable increase in eastern Yunnan.The pronounced east-west dipole pattern in SSR anomalies is driven by a meridionally elongated Northwest Pacific anticyclone,which enhances northward moisture transport to the east of southern China while leaving western areas drier.Further research reveals that distinct moisture anomalies during the developing winter of EP and CP events result in divergent SSR distributions across southern China,primarily through modulating the total cloud cover.These findings highlight the critical need to differentiate between El Niño types when predicting medium and long-term variability of radiation in southern China.
文摘Four observed blocking anticyclones in different regions of the Northern Hemisphere are in- vestigated.Analyses show that there exist distinct differences in the maintenance of the time-mean quasi-geostrophic potential vorticity(PV)low in 300 hPa within blocking areas.In two Pacific blocking cases,the PV advection by time-mean flow tends to flow the PV low to northwestern part of the blocking highs,and thus is beneficial to the maintenance of the blockings'strength.The transfer by transient eddies acts to balance the effect of the time-mean flow.In the Atlantic and Alaska blocking cases,however,the advection of mean flow tends to flow the PV low eastward. The PV transfer by transient eddies acts to flow potential vorticity low to the western part of the blocking ridges and also to balance the time-mean flow's effect.Thus,in the latter two cases,it is the transfer by the transient eddies that acts to maintain the blockings.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Key Research and Development Program of China(2023YFF0805300)Civilian Space Programme of China(D040305)。
文摘This research analyzes the variations of the South Asian Summer Monsoon Rainfall Anomaly(SASMRA)between the first development year(Y0)and the following year(Y1)of all multi-year La Ni?a events from 1958 to 2022.During Y0,monsoon precipitation surpasses climatological values,presenting a tripole spatial pattern,whereas Y1 is characterized by below-normal precipitation with a dipole pattern.In certain regions,the difference in precipitation between Y0 and Y1 reaches up to 3 mm day–1.This work provides further insight into the key tropical ocean regions driving the precipitation distinction,and elucidates their coupling mechanisms with large-scale atmospheric circulation anomalies.Influenced by the development of earlier ocean-atmosphere anomaly patterns,the Tropical Indian Ocean and Western Pacific(TIO-WP)warming(cooling)is significant during the summer of Y0(Y1).The elevated sea surface temperature(SST)in Y0 supports an anomalous Western North Pacific(WNP)anticyclone via a Kelvin-wave-induced Ekman divergence mechanism.This anomalous anticyclone intensifies the suppressed convection over the WNP,which results in increased divergence in the upper-level troposphere over the Indian Ocean and South Asian regions,thereby boosting convection.Simultaneously,the easterly winds associated with the strengthened equatorial latitude SST anomaly(SSTA)gradient and the anomalous anticyclone intensified,transporting a large amount of water vapor to the west.The combined moisture and dynamic conditions support the enhanced precipitation in the South Asian region.
文摘In this paper, the case of Jupiter being found in hydrodynamic equilibrium is for the first time investigated solely by mathematical methods. With the help of the hydrodynamic method, formulas of energy balance for oval and vortex are found, which are summed as permanent kinetic energy and constantly provide equilibrium for the stable rotational movements of Jupiter. To find the total kinetic energy of the oval and vortex in turbulent mode, Green’s function methods with special definitions and flow functions that describe the movement of the vortex are applied. The results are expressed in lemmas and theorems. For the hydrodynamic equilibrium of Jupiter, the necessary and sufficient conditions for the preservation of the cyclone and the anticyclone are mentioned. The relationships between the angular velocity and the gradient of pressure and the Corolias parameter are also given. The Rossby number is given for steady rotational motion. These facts show the existence of necessary and sufficient conditions for maintaining the stability of rotational motion and prove the hydrodynamic equilibrium of Jupiter. In this case using stream function and constructing generalized Green’s function and accordance energy conservation laws, the hydrodynamic equilibrium of Jupiter is proved.
文摘The given investigation presents the results of estimating the water circulation in the water area of the Bering Sea and the Sea of Okhotsks, considering the influence of various types of the atmospheric processes. To solve the given problem it is used a hydrodynamic model calculating the integral functions of the flow from the surface to the bottom. By results of calculations, the maps of the integral water circulation were built for the following types of atmospheric circulation： ＂north-western＂ and ＂okhotsk-aleutian＂. In accordance with the performed calculations for the water area being studied, the hydrodynamic structures are distinguished both non-depending and depending on the type of the atmospheric circulation. The non-depending structures are characterized by the cyclonic activity in the Bering Sea and the Sea of Okhotsk in whole. Hydrodynamic structures depending on types of the atmospheric circulation have their peculiarities in the spatial-temporal distribution.
基金This study was sponsored by Chinese Academy of Sciences under grant " Hundred Talents" for " Validation of Coupled Climate model
文摘The climatic features associated with the eastern China summer rainfalls (ECSR) are examined in the National Center for Atmospheric Research (NCAR) Community Climate Model Version 3 (CCM3) of the United States of America, and run with time-evolving sea surface temperature (SST) from September 1978 to August 1993. The CCM3 is shown to capture the salient seasonal features of ECSR. As many other climate models, however, there are some unrealistic projections of ECSR in the CCM3. The most unacceptable one is the erroneously intensified precipitation center on the east periphery of the Tibetan Plateau and its northeastward extension. The artificial strong rainfall center is fairly assessed by comparing with the products of the station rainfall data, Xie and Arkin (1996) rainfall data and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (Gibson et al., 1997). The physical processes involved in the formation of the rainfall center are discussed. The preliminary conclusion reveals that it is the overestimated sensible heating over and around the Tibetan Plateau in the CCM3 that causes the heavy rainfall. The unreal strong surface sensible heating over the southeast and northeast of Tibetan Plateau favors the forming of a powerful subtropical anticyclone over the eastern China. The fake enclosed subtropical anticyclone center makes the moist southwest wind fasten on the east periphery of the Tibetan Plateau and extend to its northeast. In the southeast coast of China, locating on the southeast side of the subtropical anticyclone, the southwest monsoon is decreased and even replaced by northeast wind in some cases. In the CCM3, therefore, the precipitation is exaggerated on the east periphery of the Tibetan Plateau and its northeast extension and is underestimated in the southeast coast of China. Key words Eastern China summer rainfall - Model validation - Subtropical anticyclone - Diabatic heating This study was sponsored by Chinese Academy of Sciences under grant “ Hundred Talents” for “ Validation of Coupled Climate models” and the National Natural Science Foundation of China (Grant No.49823002), and IAP innovation fund (No. 8-1204).
基金supported by the National Natural Science Foundation of China (Grant Nos. 40725016 and 40221503).
文摘ENSO＇s effect on the rainfall in eastern China in the following early summer is investigated by using station precipitation data and the ERA-40 reanalysis data from 1958 to 2002. In June, after the E1 Nifio peak, the precipitation is significantly enhanced in the Yangtze River valley while suppressed in the Huaihe River-Yellow River valleys. This relationship between ENSO and the rainfall in eastern China is established possibly through two teleconnections： One is related to the western North Pacific （WNP） anticyclonic anomaly in the lower troposphere leading to enhanced precipitation in the Yangtze River valley, and the other is related to the southward displacement of the Asian jet stream （AJS） in the upper troposphere resulting in suppressed precipitation in the Huaihe River-Yellow River valleys. This southward displacement of the AJS is one part of ENSO＇s effect on the zonal flow in the whole Northern Hemisphere. After the E1 Nifio peak, the ENSO-related warming in the tropical troposphere persists into the following early summer, increasing the meridional temperature gradient and through the thermal wind balance, leads to the enhancement of westerly flow in the subtropics south of the westerly jet stream and results in a southward displacement of the westerly jet stream.
基金Supported by the National Natural Science Foundation of China(Nos.41621064,U1709202,41606003)the National Basic Research Program of China(973 Program)(No.2014CB441501)the project of the State Key Laboratory of Satellite Ocean Environment Dynamics(No.SOEDZZ1704)
文摘In this study, high-resolution temperature and salinity data obtained from three Sea-Wing underwater gliders were used together with satellite altimeter data to track the vertical thermohaline structure of an anticyclonic eddy that originated from the loop current of the Kuroshio southwest of Taiwan, China. One of the gliders crossed the entire eddy and it observed a remarkable warm anomaly of as much as 3.9℃ extending to 500 dbar from the base of the mixed layer. Conversely, a positive salinity anomaly was found to be above 200 dbar only in the anticyclonic eddy, with a maximum value of >0.5 in the mixed layer. Below the mixed layer, water of higher salinity (>34.7) was found, which could have been preserved through constrained vertical mixing within the anticyclonic eddy. The salinity in the upper layer of the anticyclonic eddy was much similar to that of the northwestern Pacific Ocean than the northern South China Sea, reflecting Kuroshio intrusion with anticyclonic eddy shedding from the loop current.
文摘Based on NCEP/NCAR reanalysis data, the interdecadal variability of Hadley circulation （HC） and its association with East Asian temperature in winter are investigated. Results indicate that the Northern Hemisphere winter HC underwent apparent change in the 1970s, with transition occurring around 1976/77. Along with interdecadal variability of HC, its linkage to surface air temperature （SAT） in East Asia also varied decadally, from weak relations to strong relations. Such a change may be related to the interaction between HC and the atmospheric circulation system over the Philippines, which is associated with the East Asian winter monsoon （EAWM）. Before the 1970s, the connection between HC and the anticyclonic circulation around the Philippines was insignificant, but after the late 1970s their linkage entered a strong regime. The intensification of this connection may therefore be responsible for the strong relations between HC and East Asian winter temperatures after the late 1970s.
基金supported by the Chinese Academy of Sciences(Grant No.ZKCX2 SW-210)the National Natural Science Foundation of China(Grant Nos.40135020,40221503,and 40023001).
文摘The studies in China on the formation of the summertime subtropical anticyclone on the climate timescale are reviewed. New insights in resent studies are introduced. It is stressed that either in the free atmosphere or in the planetary boundary, the descending arm of the Hadley cell cannot be considered as a mechanism for the formation of the subtropical anticyclone. Then the theories of thermal adaptation of the atmosphere to external thermal forcing and the potential vorticity forcing are developed to understand the formation of the subtropical anticyclone in the three-dimensional domain. Numerical experiments are designed to verify these theories. Results show that in the boreal summer, the formation of the strong South Asian High in the upper troposphere and the subtropical anticyclone over the western Pacific in the middle and lower troposphere is, to a great extent, due to the convective latent heating associated with the Asian monsoon, but affected by orography and the surface sensible heating over the continents. On the other hand, the formation of the subtropical anticyclone at the surface over the northern Pacific and in the upper troposphere over North America is mainly due to the strong surface sensible heating over North America, but affected by radiation cooling over the eastern North Pacific. Moreover, in the real atmosphere such individual thermal forcing is well organized. By considering the different diabatic heating in synthesis, a quadruple heating pattern is found over each subtropical continent and its adjacent oceans in summer. A distinct circulation pattern accompanies this heating pattern. The global summer subtropical heating and circulation may be viewed as 'mosaics' of such quadruplet heating and circulation patterns respectively. At last, some important issues for further research in understanding and predicting the variations of the subtropical anticyclone are raised.
基金supported by the National Basic Research Program of China (Grant No. 2010CB428602)the National Natural Science Foundation of China (Grant Nos. 41175040 and 91337214)
文摘The Asian summer monsoon （ASM） anticyclone is a dominant feature of the circulation in the upper troposphere- lower stratosphere （UTLS） during boreal summer, which is found to have persistent maxima in carbon monoxide （CO）. This enhancement is due to the upward transport of air with high CO from the planetary boundary layer （PBL）, and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting （WRF） with chemistry model （WRF- Chem）. According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result is mainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.
基金This work was jointly supported by China National Key R&D Program 2018YFA0605604,NSFC Grant No.42088101,NOAA NA18OAR4310298,and NSF AGS-2006553This is SOEST contribution number 11354,IPRC contribution number 1524,and ESMC number 350.
文摘Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley(YRV)in June-July(JJ)2020.An observational data analysis has indicated that the strong and persistent rainfall arose from the confluence of southerly wind anomalies to the south associated with an extremely strong anomalous anticyclone over the western North Pacific(WNPAC)and northeasterly anomalies to the north associated with a high-pressure anomaly over Northeast Asia.A further observational and modeling study has shown that the extremely strong WNPAC was caused by both La Niña-like SST anomaly(SSTA)forcing in the equatorial Pacific and warm SSTA forcing in the tropical Indian Ocean(IO).Different from conventional central Pacific(CP)El Niños that decay slowly,a CP El Niño in early 2020 decayed quickly and became a La Niña by early summer.This quick transition had a critical impact on the WNPAC.Meanwhile,an unusually large area of SST warming occurred in the tropical IO because a moderate interannual SSTA over the IO associated with the CP El Niño was superposed by an interdecadal/long-term trend component.Numerical sensitivity experiments have demonstrated that both the heating anomaly in the IO and the heating anomaly in the tropical Pacific contributed to the formation and maintenance of the WNPAC.The persistent high-pressure anomaly in Northeast Asia was part of a stationary Rossby wave train in the midlatitudes,driven by combined heating anomalies over India,the tropical eastern Pacific,and the tropical Atlantic.
基金The National Natural Science Foundation of China under contract Nos 41906008,41806039,41806030,42076021,41676010 and 41706205the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract Nos LTO1902 and LTO1807+9 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDB42000000the Youth Innovation Promotion Association CAS under contract No.2017397the Pearl River S&T Nova Program of Guangzhou under contract No.201806010105the Open Fund of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of OceanographyMNR under contract No.QNHX2022the Startup Foundation for Introducing Talent of Nanjing University of Information Science&Technology under contract No.2019r049the Startup Foundation for Introducing Talent of Zhejiang Ocean Universitythe National Key Research Programs of China under contract Nos2016YFC1401407 and 2017YFA0604100the National Programme on Global Change and Air-Sea Interaction under contract Nos GASIIPOVAI-03 and GASI-IPOVAI-05the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020004。
文摘In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anticyclonic)eddies associated with warm(cold)cores in the South China Sea(SCS).These"abnormal"eddies pose a challenge to previous works on eddy detection,characteristic analysis,eddy-induced heat and salt transports,and even on mesoscale eddy dynamics.Based on a 9-year(2000–2008)numerical modelling data,the cyclonic warm-core eddies(CWEs)and anticyclonic cold-core eddies(ACEs)in the SCS are analyzed.This study found that the highest incidence area of the"abnormal"eddies is the northwest of Luzon Strait.In terms of the eddy snapshot counting method,8620 CWEs and 9879 ACEs are detected,accounting for 14.6%and 15.8%of the total eddy number,respectively.The size of the"abnormal"eddies is usually smaller than that of the"normal"eddies,with the radius only around 50 km.In the generation time aspect,they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan.The survival time of CWEs(ACEs)occupies 16.3%(17.1%)of the total eddy lifespan.Based on two case studies,the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these"abnormal"eddies near the northeastern SCS.
基金The National Natural Science Foundation of China under contact No.41106023the State Oceanic Administration Marine Science Foundation for Youth of China under contact No.2012204the Open Research Program of the Key Laboratory of Ocean Circulation and Wave,Institute of Oceanology,Chinese Academy of Sciences,under contact No.KLOCAW1102
文摘Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event. By analyzing the monthly data of HadISST from 1950 to 2007, it shows that the interannual component of SST anomalies peak approximately 10 months after SST anomalies peak in the eastern equatorial Pacific. As the ENSO event progresses, the positive SST anomalies spread throughout the China seas and eastward along the Kuroshio extension. Atmospheric reanalysis data demonstrate that changes in the net surface heat flux entering into the China seas are responsible for the SST variability. During E1 Nifio, the western north Pacific anticyclone is generated, with anomalous southwester lies prevailing along the East Asian coast. This anticyclone reduces the mean surface wind speed which decreases the surface heat flux and then increases the SST. The delays between the developing of this anticyclone and the south Indian Ocean anticyclone with approximately 3-6 months cause the 2-3 months lag of the surface heat flux between the China seas and the Indian Ocean. The northwestern Pacific anticyclone is the key process bridging the warming in the eastern equatorial Pacific and that in the China seas.
基金This study was jointly supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(Grant No.XDB40000000)the CAS(Grant No.QYZDJ-SSW-DQC021)+3 种基金the National Natural Science Foundation of China(Grant No.41630531)the State Key Laboratory of Loess and Quaternary GeologyWe thank the supercomputer center of the Pilot Qingdao National Laboratory for Marine Science and Technology and Beijing Super Cloud Computing Center,who offered computing servicesWe also thank Dr.X.Z.LI,H.LIU,and L.LIU from the Institute of Earth Environment,CAS,who offered suggestions for our numerical experiments.
文摘In summer 2020,extreme rainfall occurred throughout the Yangtze River basin,Huaihe River basin,and southern Yellow River basin,which are defined here as the central China(CC)region.However,only a weak central Pacific(CP)El Niño happened during winter 2019/20,so the correlations between the El Niño–Southern Oscillation(ENSO)indices and ENSO-induced circulation anomalies were insufficient to explain this extreme precipitation event.In this study,reanalysis data and numerical experiments are employed to identify and verify the primary ENSO-related factors that cause this extreme rainfall event.During summer 2020,unusually strong anomalous southwesterlies on the northwest side of an extremely strong Northwest Pacific anticyclone anomaly(NWPAC)contributed excess moisture and convective instability to the CC region,and thus,triggered extreme precipitation in this area.The tropical Indian Ocean(TIO)has warmed in recent decades,and consequently,intensified TIO basinwide warming appears after a weak El Niño,which excites an extremely strong NWPAC via the pathway of the Indo-western Pacific Ocean capacitor(IPOC)effect.Additionally,the ENSO event of 2019/20 should be treated as a fast-decaying CP El Niño rather than a general CP El Niño,so that the circulation and precipitation anomalies in summer 2020 can be better understood.Last,the increasing trend of tropospheric temperature and moisture content in the CC region after 2000 is also conducive to producing heavy precipitation.
基金supported by the National Key Research and Development Program of China (Grant No.2016YFA0600703)the National Natural Science Foundation of China (Grant No.41805046)+2 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No.18KJB170013)the Startup Foundation for Introducing Talent of NUIST (Grant No.2243141701085)the funding of the Jiangsu Innovation and Entrepreneurship Team
文摘This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China （NEC） and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC （referred to as the south mode）, whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC （referred to as the north mode）. Further findings reveal that, through modulating moisture transportation and upper- and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC＇s northern and western boundal＇ies. Furthermore, the north （south） mode is strongly related to the intensity （meridional shift） of the East Asian westerly jet.
基金supported by the Ministry of Science and Technology of China(National Basic Research Program of China(Grant No.2012CB955602))the National Key Program for Developing Basic Science(Grant No.2010CB428904)the Natural Science Foundation of China(Grant Nos.40830106,40921004,41176006)
文摘A robust anomalous anticyclonic circulation (AAC) was observed over Northeast Asia and the Japan Sea in boreal win-ter 1997/98 and over the Japan Sea in spring 1998. The formation mechanism is investigated. On the background of the vertically sheared winter monsoonal flow, anomalous rainfall in the tropical Indo-Western Pacific warm pool excited a wave train towards East Asia in the upper troposphere during boreal winter of 1997/98. The AAC over Northeast Asia and the Japan Sea is part of the wave train of equivalent barotropic structure. The AAC over the Japan Sea persisted from winter to spring and even intensified in spring 1998. The diagnostic calculations show that the vorticity and temperature fluxes by synoptic eddies are an important mechanism for the AAC over the Japan Sea in spring 1998.
基金the project for the Knowledge Innovation Program of South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.50601-30.the National Natural Science Foundation of China(NSFC)under contract Nos 40l75018,40136010
文摘The relationship between sea surface temperature anomaly (SSTA) in the domain from the northwest of the Pacific to China seas (NWP-CS) and climate (precipitation and surface temperature) anomaly in winters over east of Chinese Mainland (ECM) are investigated with composite analysis. The results suggest that (1) SSTA in NWP-CS usually appears as 'seesaw' pattern, i.e., sign of SSTA in the northwest of the Philippines is positive (negative) while in the southeast it is negative (positive), defined as SSTA 'seesaw' positive (negative) pattern. When SSTA 'seesaw' positive (negative) pattern appears, the surface temperature in ECM is higher (lower) than the normal winters but the precipitation anomaly is not distinct ; (2) there are two anomalous anticyclones (cyclones) locating in the northwest Pacific and east of the Philippines at 850 hPa level and an anomalous anti-Hadley (Hadley) circulation, which descends (ascends) south of 18oN, ascends (descends) north of 18oN; (3) heat flux anomaly from ocean into atmosphere is weaker (stronger) in the northwest of the Philippines but stronger (weaker) in the southeast of the Philippines than the normal winters, because the weaker (stronger) northerly prevails in the northwest of the Philippines and stronger (weaker) northeaster in the southeast of the Philippines induced by anomalous anticyclones (cyclones).
基金supported jointly by the National Key Research and Development Program of China[grant number 2019YFC1510201]the National Natural Science Foundation of China[grant number 41975073].
文摘To better understand the relationship between anticyclones in Siberia and cold-air activities and temperature changes in East Asia,this study proposes a 2D anticyclone identification method based on a deep-learning model,Mask R-CNN,which can reliably detect the changes in the morphological characteristics of anticyclones.Using the new method,the authors identified the southeastward-extending Siberian cold high(SEESCH),which greatly affects wintertime temperatures in China.This type of cold high is one of the main synoptic systems(45.7%)emerging from Siberia in winter.Cold air carried by SEESCH has a significant negative correlation with the temperature changes in the downstream area,and 52% of SEESCHs are accompanied by cold-air accumulation in North and East China,which has a significant impact on regional cooling.These results provide clues for studying the interconnection between SEESCHs and extreme cold events.
