In the summer of 2022,China(especially the Yangtze River Valley,YRV)suffered its strongest heatwave(HW)event since 1961.In this study,we examined the influences of multiscale variabilities on the 2022 extreme HW in th...In the summer of 2022,China(especially the Yangtze River Valley,YRV)suffered its strongest heatwave(HW)event since 1961.In this study,we examined the influences of multiscale variabilities on the 2022 extreme HW in the lower reaches of the YRV,focusing on the city of Shanghai.We found that about 1/3 of the 2022 HW days in Shanghai can be attributed to the long-term warming trend of global warming.During mid-summer of 2022,an enhanced western Pacific subtropical high(WPSH)and anomalous double blockings over the Ural Mountains and Sea of Okhotsk,respectively,were associated with the persistently anomalous high pressure over the YRV,leading to the extreme HW.The Pacific Decadal Oscillation played a major role in the anomalous blocking pattern associated with the HW at the decadal time scale.Also,the positive phase of the Atlantic Multidecadal Oscillation may have contributed to regulating the formation of the double-blocking pattern.Anomalous warming of both the warm pool of the western Pacific and tropical North Atlantic at the interannual time scale may also have favored the persistency of the double blocking and the anomalously strong WPSH.At the subseasonal time scale,the anomalously frequent phases 2-5 of the canonical northward propagating variability of boreal summer intraseasonal oscillation associated with the anomalous propagation of a weak Madden-Julian Oscillation suppressed the convection over the YRV and also contributed to the HW.Therefore,the 2022 extreme HW originated from multiscale forcing including both the climate warming trend and air-sea interaction at multiple time scales.展开更多
In this study, the interannual and interdecadal relationship between midsummer Yangtze River-Huaihe River valley (YHRV) rainfall and the position of the East Asia westerly jet (EAWJ) were investigated. The midsumm...In this study, the interannual and interdecadal relationship between midsummer Yangtze River-Huaihe River valley (YHRV) rainfall and the position of the East Asia westerly jet (EAWJ) were investigated. The midsummer YHRV rainfall was found to significantly increase after the 1980s. Moreover, the location of the EAWJ was found abnormally south of the climatic mean during 1980–2008 (ID2) compared to 1951–1979 (ID1). During ID2, associated with the southward movement of the EAWJ, an anomalous upper-level conver-gence occurred over middle-high latitudes (35° –55° N) and divergence occurred over lower latitudes (~30°N) of East Asia. Correspondingly, anomalous descending and ascending motion was observed in middle-high and lower latitudes along 90°–130° E, respectively, favoring more precipitation over YHRV. On an interan-nual time scale, the EAWJ and YHRV rainfall exhibited similar relationships during the two periods. When the EAWJ was centered abnormally southward, rainfall over YHRV tended to increase. However, EAWJ-related circulations were significantly different during the two periods. During ID1, the circulation of the southward-moving EAWJ exhibited alternating positive–negative–positive distributions from low to middle– high latitudes along the East Asian coast; the most significant anomaly appeared west of the Okhotsk Sea. However, during ID2 the EAWJ was more closely correlated with the tropical and subtropical circulations. Significant differences between ID1 and ID2 were also recorded sea surface temperatures (SSTs). During ID1, the EAWJ was influenced by the extratropical SST over the northern Pacific; however, the EAWJ was more significantly affected by the SST of the tropical western Pacific during ID2.展开更多
The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu (i.e., the East Asian rainy season in June) and the related tropical convection wer...The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu (i.e., the East Asian rainy season in June) and the related tropical convection were investigated. During the both flooding cases, although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere, the phase of the Rossby wave train is different over Eurasian continent. During flooding in the Huaihe River valley, only one single blocking anticyclone is located over Baikal Lake. In contrast, during flooding in the Yangtze River valley, there are two blocking anticyclones. One is over the Ural Mountains and the other is over Northeast Asia. In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific (SAWP) in both flooding cases, but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding. Fhrthermore, abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula. However, the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific. Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation. While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south, along with abundant rainfall.展开更多
This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs.Results show that more long-duration(over 8 days) high...This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs.Results show that more long-duration(over 8 days) high temperature events occur over the middle and lower reaches of the Yangtze River Valley(YRV) than over the surrounding regions,and control most of the interannual variation of summer mean temperature in situ.The synergistic effect of summer precipitation over the South China Sea(SCS) region(18°–27°N,115°–124°E) and the northwestern India and Arabian Sea(IAS) region(18°–27°N,60°–80°E) contributes more significantly to the variation of summer YRV temperature,relative to the respective SCS or IAS precipitation anomaly.More precipitation(enhanced condensational heating) over the SCS region strengthens the western Pacific subtropical high(WPSH) and simultaneously weakens the westerly trough over the east coast of Asia,and accordingly results in associated high temperature anomalies over the YRV region through stimulating an East Asia–Pacific(EAP) pattern.More precipitation over the IAS region further adjusts the variations of the WPSH and westerly trough,and eventually reinforces high temperature anomalies over the YRV region.Furthermore,the condensational heating related to more IAS precipitation can adjust upper-tropospheric easterly anomalies over the YRV region by exciting a circumglobal teleconnection,inducing cold horizontal temperature advection and related anomalous descent,which is also conducive to the YRV high temperature anomalies.The reproduction of the above association in the model results indicates that the above results can be explained both statistically and dynamically.展开更多
Using daily outgoing long-wave radiation (OLR) data from the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Environmental Prediction/National Center for Atmospheric Research (N...Using daily outgoing long-wave radiation (OLR) data from the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events (PHREs) in the Huaihe River valley (HRV) and the distribution pattern of convective activity in the tropical western Pacific warm pool (WPWP) is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high (WPSH) show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent "north weak south strong" distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley (YRV) are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak (strong) manner across the whole WPWP, persistent heavy (light) rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the "north weak south strong" pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the "north weak south strong" distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.展开更多
Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR ...Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.展开更多
Based on the National Oceanic and Atmospheric Administration (NOAA) daily satellite dataset of global outgoing longwave radiation (OLR) for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the ...Based on the National Oceanic and Atmospheric Administration (NOAA) daily satellite dataset of global outgoing longwave radiation (OLR) for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the linkage between persistent heavy rainfall (PHR) events in the vicinity of the Yangtze River valley and global OLR leading up to those events (with 1- to 3O-day lag) was investigated. The results reveal that there is a significant connection between the initiation of PHR events over the study area and anomalous convective activity over the tropical Indian Ocean, maritime continent, and tropical western Pacific Ocean. During the 30-day period prior to the onset of PHR events, the major significantly anomalous convective centers have an apparent dipole structure, always with enhanced convection in the west and suppressed convection in the east. This dipole structure continuously shifts eastward with time during the 30-day lead period. The influence of the anomalous convective activity over the tropical oceans on the initiation of PHR events over the study area is achieved via an interaction between tropical and extratropical latitudes. More specifically, anomalous convective activity weakens the Walker circulation cell over the tropical Indian Ocean first. This is followed by a weakening of the Indian summer monsoon background state and the excitation and dispersion of Rossby wave activity over Eurasia. Finally, a major modulation of the large scale background circulation occurs. As a result, the condition of a phase-lock among major large scale circulation features favoring PHR events is established over the study area.展开更多
With the IAP/LASG GOALS model, the relationships between the floods in the Yangtze River valley arid sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results sho...With the IAP/LASG GOALS model, the relationships between the floods in the Yangtze River valley arid sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results show that the model can reproduce the heavy rainfall over the Yangtze River valley in the sum-mer of 1998 forced by global observational sea surface temperatures (SST). The model can also reproduce the observed principal features of the subtropical high anomalies over the western Pacific. The experiments with the observed SST in different ocean areas and different periods have been made. By comparing the ef-fects of SSTA of different ocean areas on the floods, it is found that the SSTA in the Indian Ocean are a ma-jor contributor to the floods, and the results also show that the SSTA in the Indian Ocean and the western Pacific have a much closer relationship with the strong anomalies of the subtropical high over the western Pacific than the SSTA in other concerned areas. The study also indicates that the floods and subtropical high anomalies in the summer of 1998 are more controlled by the simultaneous summertime SSTA than by SSTA in the preceding winter and spring seasons.展开更多
To comprehensively investigate characteristics of summer droughts and floods in the Yangtze River valley, a meteorological and hydrological coupling index (MHCI) was developed using meteorological and hydro- logical...To comprehensively investigate characteristics of summer droughts and floods in the Yangtze River valley, a meteorological and hydrological coupling index (MHCI) was developed using meteorological and hydro- logical data. The results indicate that: (1) in representing drought/flood information for the Yangtze River valley, the MHCI can reflect composite features of precipitation and hydrological observations; (2) compre- hensive analysis of the interannual phase difference of the precipitation and hydrological indices is important to recognize and predict annual drought/flood events along the valley; the hydrological index contributes more strongly to nonlinear and continuity features that indicate transition from long-term drought to flood conditions; (3) time series of the MHCI from 1960-2009 are very effective and sensitive in reflecting annual drought/flood characteristics, i.e. there is more rainfall or typical flooding in the valley when the MHCI is positive, and vice versa; and (4) verification of the MHCI indicates that there is significant correlation between precipitation and hydrologic responses in the valley during summer; the correlation coefficient was found to reach 0.82, exceeding the 0.001 significance level.展开更多
In order to investigate the conversion of kinetic energy from a synoptic scale disturbance (SSD; period≤seven days) to a low-frequency fluctuation (LFF; period〉seven days), the budget equation of the LFF kinetic...In order to investigate the conversion of kinetic energy from a synoptic scale disturbance (SSD; period≤seven days) to a low-frequency fluctuation (LFF; period〉seven days), the budget equation of the LFF kinetic energy is derived. The energy conversion is then calculated and analyzed for the summers of 1997 and 1999. The results show that the energy conversion from the SSD to the LFF is obviously enhanced in the middle and lower troposphere during the heavy rainfall, suggesting this to be one of mechanisms inducing the heavy rainfall, although the local LFF kinetic energy may not be enhanced.展开更多
The Yangtze River Valley (YRV) occupies a very important position in the course of historical development of the Chinese nation. Since the early stage of Old Stone Age, our forefathers have laboured, lived and multipl...The Yangtze River Valley (YRV) occupies a very important position in the course of historical development of the Chinese nation. Since the early stage of Old Stone Age, our forefathers have laboured, lived and multiplied on this land, and left us plentiful of ancient cultural heritage. The fossil of Yunyang Man found in Yunyang of Hubei Province based on determination was two million years ago. That is to say, the populationenvironment relationship in the YRV has gone on at least over two million years. Here we briefly inquire into the history of variations in the development of the populationenvironment relationship in the YRV in the period of feudal society including semicolonial and semifeudal society in modern times.展开更多
It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of E1 Nifio, as demonstrated by the catastrophic flooding suffered in the summer of 1998....It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of E1 Nifio, as demonstrated by the catastrophic flooding suffered in the summer of 1998. Nevertheless, the rainfall over the YRV in the summer of 2016 was much weaker than that in 1998, despite the intensity of the 2016 E1 Nifio having been as strong as that in 1998. A thorough comparison of the YRV summer rainfall anomaly between 2016 and 1998 suggests that the difference was caused by the sub-seasonal variation in the YRV rainfall anomaly between these two years, principally in August. The precipitation anomaly was negative in August 2016--different to the positive anomaly of 1998.展开更多
Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system. This paper reviews the progress of Holocene environmental c...Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system. This paper reviews the progress of Holocene environmental change and environmental archaeology research in the Yangtze River Valley over the last three decades, that includes the evolution of large freshwater lakes, Holocene transgression and sea-level changes, Holocene climate change and East Asian monsoon variation, relationship between the rise and fall of primitive civilizations and environmental changes, cultural interruptions and palaeo- flood events, as well as relationship between the origin of agriculture and climate change. These research components are underpinned by the dating of lacustrine sediments, stalagmites and peat to establish a chronology of regional environmental and cultural evolution. Interdisciplinary and other environment proxy indicators need to be used in comparative studies of archaeological site formation and natural sedi- mentary environment in the upper, middle and lower reaches of the Yangtze River Valley. Modern tech- nology such as remote sensing, molecular bioarchaeology, and virtual reality, should be integrated with currently used dating, geochemical, sedimentological, and palaeobotanical methods of analysis in envi- ronmental archaeology macro- and micro-studies, so as to provide a greater comprehensive insight into Holocene environmental and cultural interaction and change in the Yangtze River Valley area.展开更多
In this study, the major features of a heavy rainfall event in the Yangtze River region on 3-7 June 2011 and its event-related large-scale circulation and predictability were studied. Both observational analysis and m...In this study, the major features of a heavy rainfall event in the Yangtze River region on 3-7 June 2011 and its event-related large-scale circulation and predictability were studied. Both observational analysis and model simulation were used, the latter being based on the Weather Research and Forecasting (WRF) model forced by NCEP Global Forecast System (GFS) datasets. It was found that, during 3-5 June, the western Pacific subtropical high apparently extended to the west and was much stronger, and the Indian summer monsoon trough was slightly weaker than in normal years. The east-west oriented shear line over the middle and lower reaches of the Yangtze River was favorable for the transportation and convergence of water vapor, and the precipitation band was located slightly to the south of the shear line. During 6-7 June, the western Pacific subtropical high retreated eastward, while the trough over the Okhotsk Sea deepened. The low vortex in Northeast China intensified, bringing much more cold air to the middle and lower reaches of the Yangtze River, and the shear line over this area moved slightly southward. The convection band moved southward and became weaker, so the rainfall during 6-7 June weakened and was located slightly to the south of the previous precipitation band. Many of the observed features, including background circulation and the distribution and amount of precipitation, were reproduced reasonably by the WRF, suggesting a feasibility of this model for forecasting extreme weather events in the Yangtze River region.展开更多
With the IAP/LASG GOALS model, the heavy rainfall of the summer of 1999 in the Yangtze River valley is simulated with observational sea surface temperature (SST). Comparing the simulations of 1999 with the correspondi...With the IAP/LASG GOALS model, the heavy rainfall of the summer of 1999 in the Yangtze River valley is simulated with observational sea surface temperature (SST). Comparing the simulations of 1999 with the corresponding ones of 1998 and the sensitivity experiments with different sea surface temperature anomalies (SSTA) at different ocean regions, the relationships between the floods in the Yangtze River valley and the SSTA in the Pacific and Indian Oceans are studied. The results show that the positive SSTA in the tropical Indian Ocean are a major contributor to the heavy rainfall and may be a very important index to predict the heavy rainfall over the Yangtze River valley in the summer. The simulations also show that the relationships between the SSTA in the tropical eastern Pacific and the heavy rainfall in the Yangtze River valley are very complicated, and the heavy rainfall in the Yangtze River valley can occur in both a decaying and an intensifying El Nino event and also in a La Nina event. However, the different SSTA of different periods in the above three cases play different parts.展开更多
The present paper shows that a seasonal prediction for the large scale flooding and waterlogging of the mid-lower Yangtze/ Huaihe River basins in the summer of 1991 made successfully in early April 1991.The seasonal f...The present paper shows that a seasonal prediction for the large scale flooding and waterlogging of the mid-lower Yangtze/ Huaihe River basins in the summer of 1991 made successfully in early April 1991.The seasonal forecasting method and some predictors are also introduced and analyzed herein. Because the extra extent of the abnormally early onset of the plum rain period in 1991 was unexpected,great efforts have been made to find out the causes of this abnormality. These causes are mainly associated with the large scale warming of SST surrounding the south and east part of Asia during the preceding winter,while the ENSO-like pattern of SSTA occurred in the North Pacific.In addition,the possible influence of strong solar proton events is analyzed.In order to improve the seasonal pre4iction the usage of the predicted SOl in following spring/summer is also introduced.The author believes thatthe regional climate anomaly can be correctly predicted for one season ahead only on the basis of physical understanding of the interactions of many preceding factors.展开更多
This paper discusses the role of geologic structures in the occurrence of floods and how to prevent flood in the middle reaches of the Yangtze River, and gives the author's suggestion that the Luoshan Qiakou be ex...This paper discusses the role of geologic structures in the occurrence of floods and how to prevent flood in the middle reaches of the Yangtze River, and gives the author's suggestion that the Luoshan Qiakou be expanded and the land reclaimed from Dongting Lake be returned to the lake in compliance with the law of geology.展开更多
The distribution of winter-spring snow cover over the Tibetan Plateau (TP) and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley (MLYRV) during 2003-2013 have been ...The distribution of winter-spring snow cover over the Tibetan Plateau (TP) and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley (MLYRV) during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer (MODIS) Terra data (MOD10A2) and precipitation observations. Results show that snow cover percentage (SCP) remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency (SCF) over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.展开更多
Seasonal prediction of summer rainfall over the Yangtze River valley(YRV) is valuable for agricultural and industrial production and freshwater resource management in China, but remains a major challenge. Earlier mu...Seasonal prediction of summer rainfall over the Yangtze River valley(YRV) is valuable for agricultural and industrial production and freshwater resource management in China, but remains a major challenge. Earlier multi-model ensemble(MME) prediction schemes for summer rainfall over China focus on single-value prediction, which cannot provide the necessary uncertainty information, while commonly-used ensemble schemes for probability density function(PDF) prediction are not adapted to YRV summer rainfall prediction. In the present study, an MME PDF prediction scheme is proposed based on the ENSEMBLES hindcasts. It is similar to the earlier Bayesian ensemble prediction scheme, but with optimization of ensemble members and a revision of the variance modeling of the likelihood function. The optimized ensemble members are regressed YRV summer rainfall with factors selected from model outputs of synchronous 500-h Pa geopotential height as predictors. The revised variance modeling of the likelihood function is a simple linear regression with ensemble spread as the predictor. The cross-validation skill of 1960–2002 YRV summer rainfall prediction shows that the new scheme produces a skillful PDF prediction, and is much better-calibrated, sharper, and more accurate than the earlier Bayesian ensemble and raw ensemble.展开更多
基金the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030004)the National Natural Science Foundation of China(Grant No.42175056)+3 种基金the Natural Science Foundation of Shanghai(Grant No.21ZR1457600)Review and Summary Project of China Meteorological Administration(Grant No.FPZJ2023-044)the China Meteorological Administration Innovation and Development Project(Grant No.CXFZ2022J009)the Key Innovation Team of Climate Prediction of the China Meteorological Administration(Grant No.CMA2023ZD03).
文摘In the summer of 2022,China(especially the Yangtze River Valley,YRV)suffered its strongest heatwave(HW)event since 1961.In this study,we examined the influences of multiscale variabilities on the 2022 extreme HW in the lower reaches of the YRV,focusing on the city of Shanghai.We found that about 1/3 of the 2022 HW days in Shanghai can be attributed to the long-term warming trend of global warming.During mid-summer of 2022,an enhanced western Pacific subtropical high(WPSH)and anomalous double blockings over the Ural Mountains and Sea of Okhotsk,respectively,were associated with the persistently anomalous high pressure over the YRV,leading to the extreme HW.The Pacific Decadal Oscillation played a major role in the anomalous blocking pattern associated with the HW at the decadal time scale.Also,the positive phase of the Atlantic Multidecadal Oscillation may have contributed to regulating the formation of the double-blocking pattern.Anomalous warming of both the warm pool of the western Pacific and tropical North Atlantic at the interannual time scale may also have favored the persistency of the double blocking and the anomalously strong WPSH.At the subseasonal time scale,the anomalously frequent phases 2-5 of the canonical northward propagating variability of boreal summer intraseasonal oscillation associated with the anomalous propagation of a weak Madden-Julian Oscillation suppressed the convection over the YRV and also contributed to the HW.Therefore,the 2022 extreme HW originated from multiscale forcing including both the climate warming trend and air-sea interaction at multiple time scales.
基金supported by the National Basic Research Program of China (No. 2009CB421401)the National Natural Science Foundation of China (No. 40975022)+1 种基金the Special funds for Meteorology scientific research on public causes (No. GYHY200906014)the National Science and Technology Support Program of China (No.2007BAC29B03)
文摘In this study, the interannual and interdecadal relationship between midsummer Yangtze River-Huaihe River valley (YHRV) rainfall and the position of the East Asia westerly jet (EAWJ) were investigated. The midsummer YHRV rainfall was found to significantly increase after the 1980s. Moreover, the location of the EAWJ was found abnormally south of the climatic mean during 1980–2008 (ID2) compared to 1951–1979 (ID1). During ID2, associated with the southward movement of the EAWJ, an anomalous upper-level conver-gence occurred over middle-high latitudes (35° –55° N) and divergence occurred over lower latitudes (~30°N) of East Asia. Correspondingly, anomalous descending and ascending motion was observed in middle-high and lower latitudes along 90°–130° E, respectively, favoring more precipitation over YHRV. On an interan-nual time scale, the EAWJ and YHRV rainfall exhibited similar relationships during the two periods. When the EAWJ was centered abnormally southward, rainfall over YHRV tended to increase. However, EAWJ-related circulations were significantly different during the two periods. During ID1, the circulation of the southward-moving EAWJ exhibited alternating positive–negative–positive distributions from low to middle– high latitudes along the East Asian coast; the most significant anomaly appeared west of the Okhotsk Sea. However, during ID2 the EAWJ was more closely correlated with the tropical and subtropical circulations. Significant differences between ID1 and ID2 were also recorded sea surface temperatures (SSTs). During ID1, the EAWJ was influenced by the extratropical SST over the northern Pacific; however, the EAWJ was more significantly affected by the SST of the tropical western Pacific during ID2.
基金supported by the National Natural Science Foundation of China(Grant No.40925015)the National Program on Key Basic Research Project(Grant Nos.2010CB950403and2012CB417203)
文摘The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu (i.e., the East Asian rainy season in June) and the related tropical convection were investigated. During the both flooding cases, although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere, the phase of the Rossby wave train is different over Eurasian continent. During flooding in the Huaihe River valley, only one single blocking anticyclone is located over Baikal Lake. In contrast, during flooding in the Yangtze River valley, there are two blocking anticyclones. One is over the Ural Mountains and the other is over Northeast Asia. In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific (SAWP) in both flooding cases, but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding. Fhrthermore, abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula. However, the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific. Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation. While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south, along with abundant rainfall.
基金the support of the National Natural Science Foundation of China(Grant Nos.41375090 and 41375091)the Basic Research Fund of the Chinese Academy of Meteorological Sciences(Grant Nos.2013Z002 and 2015Z001)the support of a Direct Grant of the Chinese University of Hong Kong(Grant No.4052057)
文摘This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs.Results show that more long-duration(over 8 days) high temperature events occur over the middle and lower reaches of the Yangtze River Valley(YRV) than over the surrounding regions,and control most of the interannual variation of summer mean temperature in situ.The synergistic effect of summer precipitation over the South China Sea(SCS) region(18°–27°N,115°–124°E) and the northwestern India and Arabian Sea(IAS) region(18°–27°N,60°–80°E) contributes more significantly to the variation of summer YRV temperature,relative to the respective SCS or IAS precipitation anomaly.More precipitation(enhanced condensational heating) over the SCS region strengthens the western Pacific subtropical high(WPSH) and simultaneously weakens the westerly trough over the east coast of Asia,and accordingly results in associated high temperature anomalies over the YRV region through stimulating an East Asia–Pacific(EAP) pattern.More precipitation over the IAS region further adjusts the variations of the WPSH and westerly trough,and eventually reinforces high temperature anomalies over the YRV region.Furthermore,the condensational heating related to more IAS precipitation can adjust upper-tropospheric easterly anomalies over the YRV region by exciting a circumglobal teleconnection,inducing cold horizontal temperature advection and related anomalous descent,which is also conducive to the YRV high temperature anomalies.The reproduction of the above association in the model results indicates that the above results can be explained both statistically and dynamically.
基金This study was supported by the "National Key Programme for Developing Basic Science" projects under Grant No. 2004CB418303the National Natural Science Foundation of China under Grant No. 40705022.
文摘Using daily outgoing long-wave radiation (OLR) data from the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events (PHREs) in the Huaihe River valley (HRV) and the distribution pattern of convective activity in the tropical western Pacific warm pool (WPWP) is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high (WPSH) show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent "north weak south strong" distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley (YRV) are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak (strong) manner across the whole WPWP, persistent heavy (light) rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the "north weak south strong" pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the "north weak south strong" distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.
基金supported by the projectof the National Basic Research Program of China (GrantNo. 2009CB421401)the Key Technologies R&D Program (Grant No. 2009BAC51B02)+2 种基金the Special Scientific Research Fund of the Meteorological Public Welfare Profession of China (Grant No. GYHY200906018)the National Natural Science Foundation of China (Grant No.40705039)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. IAP07415)
文摘Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.
基金supported by the National Natural Science Foundation of China under Grant No.40575015
文摘Based on the National Oceanic and Atmospheric Administration (NOAA) daily satellite dataset of global outgoing longwave radiation (OLR) for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the linkage between persistent heavy rainfall (PHR) events in the vicinity of the Yangtze River valley and global OLR leading up to those events (with 1- to 3O-day lag) was investigated. The results reveal that there is a significant connection between the initiation of PHR events over the study area and anomalous convective activity over the tropical Indian Ocean, maritime continent, and tropical western Pacific Ocean. During the 30-day period prior to the onset of PHR events, the major significantly anomalous convective centers have an apparent dipole structure, always with enhanced convection in the west and suppressed convection in the east. This dipole structure continuously shifts eastward with time during the 30-day lead period. The influence of the anomalous convective activity over the tropical oceans on the initiation of PHR events over the study area is achieved via an interaction between tropical and extratropical latitudes. More specifically, anomalous convective activity weakens the Walker circulation cell over the tropical Indian Ocean first. This is followed by a weakening of the Indian summer monsoon background state and the excitation and dispersion of Rossby wave activity over Eurasia. Finally, a major modulation of the large scale background circulation occurs. As a result, the condition of a phase-lock among major large scale circulation features favoring PHR events is established over the study area.
基金the"National Key Programme for Developing Basic Sciences"--Research on the Formation Mechanism and Prediction Theory of Severe Climate Disasters in China(G1998040900)the National Natrual Science Foundation of China under Grant No.40135020the Project ZKCX2-SW-2t0
文摘With the IAP/LASG GOALS model, the relationships between the floods in the Yangtze River valley arid sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results show that the model can reproduce the heavy rainfall over the Yangtze River valley in the sum-mer of 1998 forced by global observational sea surface temperatures (SST). The model can also reproduce the observed principal features of the subtropical high anomalies over the western Pacific. The experiments with the observed SST in different ocean areas and different periods have been made. By comparing the ef-fects of SSTA of different ocean areas on the floods, it is found that the SSTA in the Indian Ocean are a ma-jor contributor to the floods, and the results also show that the SSTA in the Indian Ocean and the western Pacific have a much closer relationship with the strong anomalies of the subtropical high over the western Pacific than the SSTA in other concerned areas. The study also indicates that the floods and subtropical high anomalies in the summer of 1998 are more controlled by the simultaneous summertime SSTA than by SSTA in the preceding winter and spring seasons.
基金supported by project GYHY201106050the National"973"Program of China under Grant No.2011CB403404,and Project No.2009Y002
文摘To comprehensively investigate characteristics of summer droughts and floods in the Yangtze River valley, a meteorological and hydrological coupling index (MHCI) was developed using meteorological and hydro- logical data. The results indicate that: (1) in representing drought/flood information for the Yangtze River valley, the MHCI can reflect composite features of precipitation and hydrological observations; (2) compre- hensive analysis of the interannual phase difference of the precipitation and hydrological indices is important to recognize and predict annual drought/flood events along the valley; the hydrological index contributes more strongly to nonlinear and continuity features that indicate transition from long-term drought to flood conditions; (3) time series of the MHCI from 1960-2009 are very effective and sensitive in reflecting annual drought/flood characteristics, i.e. there is more rainfall or typical flooding in the valley when the MHCI is positive, and vice versa; and (4) verification of the MHCI indicates that there is significant correlation between precipitation and hydrologic responses in the valley during summer; the correlation coefficient was found to reach 0.82, exceeding the 0.001 significance level.
基金jointly supported by jointly supported by the National Key Research and Development Program of China(Grant No.2016YFA0600702)the National Natural Science Foundation of China(Grant No.41625019)
文摘In order to investigate the conversion of kinetic energy from a synoptic scale disturbance (SSD; period≤seven days) to a low-frequency fluctuation (LFF; period〉seven days), the budget equation of the LFF kinetic energy is derived. The energy conversion is then calculated and analyzed for the summers of 1997 and 1999. The results show that the energy conversion from the SSD to the LFF is obviously enhanced in the middle and lower troposphere during the heavy rainfall, suggesting this to be one of mechanisms inducing the heavy rainfall, although the local LFF kinetic energy may not be enhanced.
文摘The Yangtze River Valley (YRV) occupies a very important position in the course of historical development of the Chinese nation. Since the early stage of Old Stone Age, our forefathers have laboured, lived and multiplied on this land, and left us plentiful of ancient cultural heritage. The fossil of Yunyang Man found in Yunyang of Hubei Province based on determination was two million years ago. That is to say, the populationenvironment relationship in the YRV has gone on at least over two million years. Here we briefly inquire into the history of variations in the development of the populationenvironment relationship in the YRV in the period of feudal society including semicolonial and semifeudal society in modern times.
基金supported by the National Natural Science Foundation of China (Grant Nos.41320104007,U1502233,41675078 and 41461164005)
文摘It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of E1 Nifio, as demonstrated by the catastrophic flooding suffered in the summer of 1998. Nevertheless, the rainfall over the YRV in the summer of 2016 was much weaker than that in 1998, despite the intensity of the 2016 E1 Nifio having been as strong as that in 1998. A thorough comparison of the YRV summer rainfall anomaly between 2016 and 1998 suggests that the difference was caused by the sub-seasonal variation in the YRV rainfall anomaly between these two years, principally in August. The precipitation anomaly was negative in August 2016--different to the positive anomaly of 1998.
基金supported by the Nalional Natural Science Foundation of China(Grant Nos.40971115,and 41171163)Scientific Research Foundation of Graduate School of Nanjing University (Grant No.2011CL11)+2 种基金National Key Technology R&D Program of China(Grant No.2010BAK67B02)University Doctoral Foundation of China(Grant No.20090091110036)Open Foundation of the State Key Laboratory of Loess and Quaternary Geology,and the Institute of Earth Enviroment,CAS(Grant No. S KLLQG0817)
文摘Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system. This paper reviews the progress of Holocene environmental change and environmental archaeology research in the Yangtze River Valley over the last three decades, that includes the evolution of large freshwater lakes, Holocene transgression and sea-level changes, Holocene climate change and East Asian monsoon variation, relationship between the rise and fall of primitive civilizations and environmental changes, cultural interruptions and palaeo- flood events, as well as relationship between the origin of agriculture and climate change. These research components are underpinned by the dating of lacustrine sediments, stalagmites and peat to establish a chronology of regional environmental and cultural evolution. Interdisciplinary and other environment proxy indicators need to be used in comparative studies of archaeological site formation and natural sedi- mentary environment in the upper, middle and lower reaches of the Yangtze River Valley. Modern tech- nology such as remote sensing, molecular bioarchaeology, and virtual reality, should be integrated with currently used dating, geochemical, sedimentological, and palaeobotanical methods of analysis in envi- ronmental archaeology macro- and micro-studies, so as to provide a greater comprehensive insight into Holocene environmental and cultural interaction and change in the Yangtze River Valley area.
基金supported by the Major State Basic Research Development Program of China(973Program) under Grant No.2009CB421406the National Natural Science Foundation of China under Grant Nos.41130103 and 40821092the Norwegian Research Council"East Asia DecCen"Project
文摘In this study, the major features of a heavy rainfall event in the Yangtze River region on 3-7 June 2011 and its event-related large-scale circulation and predictability were studied. Both observational analysis and model simulation were used, the latter being based on the Weather Research and Forecasting (WRF) model forced by NCEP Global Forecast System (GFS) datasets. It was found that, during 3-5 June, the western Pacific subtropical high apparently extended to the west and was much stronger, and the Indian summer monsoon trough was slightly weaker than in normal years. The east-west oriented shear line over the middle and lower reaches of the Yangtze River was favorable for the transportation and convergence of water vapor, and the precipitation band was located slightly to the south of the shear line. During 6-7 June, the western Pacific subtropical high retreated eastward, while the trough over the Okhotsk Sea deepened. The low vortex in Northeast China intensified, bringing much more cold air to the middle and lower reaches of the Yangtze River, and the shear line over this area moved slightly southward. The convection band moved southward and became weaker, so the rainfall during 6-7 June weakened and was located slightly to the south of the previous precipitation band. Many of the observed features, including background circulation and the distribution and amount of precipitation, were reproduced reasonably by the WRF, suggesting a feasibility of this model for forecasting extreme weather events in the Yangtze River region.
文摘With the IAP/LASG GOALS model, the heavy rainfall of the summer of 1999 in the Yangtze River valley is simulated with observational sea surface temperature (SST). Comparing the simulations of 1999 with the corresponding ones of 1998 and the sensitivity experiments with different sea surface temperature anomalies (SSTA) at different ocean regions, the relationships between the floods in the Yangtze River valley and the SSTA in the Pacific and Indian Oceans are studied. The results show that the positive SSTA in the tropical Indian Ocean are a major contributor to the heavy rainfall and may be a very important index to predict the heavy rainfall over the Yangtze River valley in the summer. The simulations also show that the relationships between the SSTA in the tropical eastern Pacific and the heavy rainfall in the Yangtze River valley are very complicated, and the heavy rainfall in the Yangtze River valley can occur in both a decaying and an intensifying El Nino event and also in a La Nina event. However, the different SSTA of different periods in the above three cases play different parts.
文摘The present paper shows that a seasonal prediction for the large scale flooding and waterlogging of the mid-lower Yangtze/ Huaihe River basins in the summer of 1991 made successfully in early April 1991.The seasonal forecasting method and some predictors are also introduced and analyzed herein. Because the extra extent of the abnormally early onset of the plum rain period in 1991 was unexpected,great efforts have been made to find out the causes of this abnormality. These causes are mainly associated with the large scale warming of SST surrounding the south and east part of Asia during the preceding winter,while the ENSO-like pattern of SSTA occurred in the North Pacific.In addition,the possible influence of strong solar proton events is analyzed.In order to improve the seasonal pre4iction the usage of the predicted SOl in following spring/summer is also introduced.The author believes thatthe regional climate anomaly can be correctly predicted for one season ahead only on the basis of physical understanding of the interactions of many preceding factors.
文摘This paper discusses the role of geologic structures in the occurrence of floods and how to prevent flood in the middle reaches of the Yangtze River, and gives the author's suggestion that the Luoshan Qiakou be expanded and the land reclaimed from Dongting Lake be returned to the lake in compliance with the law of geology.
基金supported by the National Natural Science Foundation of China(Grant No.41130960)the Project of the China Meteorological Administration(Grant Nos.CCSF201515 and CMAGJ2013M51)
文摘The distribution of winter-spring snow cover over the Tibetan Plateau (TP) and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley (MLYRV) during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer (MODIS) Terra data (MOD10A2) and precipitation observations. Results show that snow cover percentage (SCP) remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency (SCF) over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.
基金co-supported by the National Natural Science Foundation (Grant Nos. 41005052 and 41375086)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05110201)the National Basic Research Program of China (Grant No. 2010CB950403)
文摘Seasonal prediction of summer rainfall over the Yangtze River valley(YRV) is valuable for agricultural and industrial production and freshwater resource management in China, but remains a major challenge. Earlier multi-model ensemble(MME) prediction schemes for summer rainfall over China focus on single-value prediction, which cannot provide the necessary uncertainty information, while commonly-used ensemble schemes for probability density function(PDF) prediction are not adapted to YRV summer rainfall prediction. In the present study, an MME PDF prediction scheme is proposed based on the ENSEMBLES hindcasts. It is similar to the earlier Bayesian ensemble prediction scheme, but with optimization of ensemble members and a revision of the variance modeling of the likelihood function. The optimized ensemble members are regressed YRV summer rainfall with factors selected from model outputs of synchronous 500-h Pa geopotential height as predictors. The revised variance modeling of the likelihood function is a simple linear regression with ensemble spread as the predictor. The cross-validation skill of 1960–2002 YRV summer rainfall prediction shows that the new scheme produces a skillful PDF prediction, and is much better-calibrated, sharper, and more accurate than the earlier Bayesian ensemble and raw ensemble.