Large-scale water transport is one of the key factors that affect sea surface temperature anomaly（SSTA） in the eastern equatorial Pacific（EEP）.The relationship between the wave transport in the tropical Pacific an...Large-scale water transport is one of the key factors that affect sea surface temperature anomaly（SSTA） in the eastern equatorial Pacific（EEP）.The relationship between the wave transport in the tropical Pacific and the SSTA in the EEP is examined by different methods,including band-pass filtering,period analysis,correlation analysis,significant analysis,and empirical orthogonal function（EOF） analysis.We have found that the eastward shift of the wave transport anomaly in the tropical Pacific,with a period of 2 a and enhancing the transport of warm waters from the western Pacific warm pool,precedes the increase of sea surface temperature（SST） in the EEP.The wave transport and the SSTA in the EEP have a maximum correlation of 0.65 with a time-lag of 6 months（transport variation precedes the temperature）.The major periods（3.7 a and 2.45 a） of the wave transport variability,as revealed by the EOF analysis,appear to be consistent with the SSTA oscillation cycle in the EEP.Based on the first occurrence of a significant SSTA in the Ni？o 3 region（5°S–5°N,90°–150°W）,two types of warm events are defined.The wave transport anomalies in two types present predominantly the west anomaly in the tropical Pacific,it is that the wave transport continues transport warm water from west to east before the onset of the warm event.The impact of wave-induced water transport on the SSTA in the EEP is confirmed by the heat flux of the wave transport.The wave transport exerts significant effect on the SSTA variability in the EEP and thus is not neglectable in the further studies.展开更多
Based on reanalysis data from 1979 to 2016,this study focuses on the sea surface temperature(SST)anomaly of the tropical North Atlantic(TNA)in El Nino decaying years.The TNA SST exhibits a clear warm trend during this...Based on reanalysis data from 1979 to 2016,this study focuses on the sea surface temperature(SST)anomaly of the tropical North Atlantic(TNA)in El Nino decaying years.The TNA SST exhibits a clear warm trend during this period.The composite result for 10 El Nino events shows that the TNA SST anomaly reaches its maximum in spring after the peak of an El Nino event and persists until summer.In general,the anomaly is associated with three factors-namely,El Nino,the North Atlantic Oscillation(NAO),and a long-term trend,leading to an increase in local SST up to 0.4℃,0.3℃,and 0.35℃,respectively.A comparison between 1983 and 2005 indicates that the TNA SST in spring is affected by El Niño,as well as the local SST in the preceding winter,which may involve a long-term trend signal.In addition,the lead-lag correlation shows that the NAO leads the TNA SST by 2-3 months.By comparing two years with an opposite phase of the NAO in winter(i.e.,1992 and 2010),the authors further demonstrate that the NAO is another important factor in regulating the TNA SST anomaly.A negative phase of the NAO in winter will reinforce the El Nino forcing substantially,and vise versa.In other words,the TNA SST anomaly in the decaying years is more evident if the NAO is negative with El Nino.Therefore,the combined effects of El Nino and the NAO must be considered in order to fully understand the TNA SST variability along with a long-term trend.展开更多
By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation an...By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there.展开更多
Global temperature has increased at a rapid rate in recent decades,and the warming rate at night is observed higher than that during the daytime among different regions.Nighttime anomalous high temperatures may pose a...Global temperature has increased at a rapid rate in recent decades,and the warming rate at night is observed higher than that during the daytime among different regions.Nighttime anomalous high temperatures may pose an additional risk to human health and society.Nevertheless,less research has explored the spatiotemporal trend and the local atmospheric mechanism of nocturnal temperature anomaly around the world.Here,we investigate the spatiotemporal trend of nighttime temperature anomaly(NTA)from 1961 to 2023,and analyze the underlying physical mechanism related to different extents of positive temperature anomaly.We find that NTA showed a significantly increased trend worldwide,with an increasing rate of0.21°C/decade.At the continental scale,NTA has increased faster in North America,Asia,and Europe.The occurrence of positive NTA is generally associated with local increased cloud cover,precipitation,and humidity,which contribute to enhanced downward longwave radiation and greenhouse effect at night.On the inter-annual scale,NTA is positively related to the preceding winter Oceanic Ni?o Index,indicating the possible modulation of El Ni?o-Southern Oscillation on the global nocturnal temperature.Our results could help to understand the variation and influence mechanism of anomalous nighttime temperature in recent decades,and inform the forecast of and response to hot nights.展开更多
Spring land surface temperature/subsurface soil temperature over the Qinghai-Xizang Plateau(QXP)substantially impacts downstream precipitation on subseasonal timescales.However,how well can climate models reproduce th...Spring land surface temperature/subsurface soil temperature over the Qinghai-Xizang Plateau(QXP)substantially impacts downstream precipitation on subseasonal timescales.However,how well can climate models reproduce this impact and its assoicated interannual variation remains unclear.This study utilized the Regional Climate Model(Reg CM)Version 4.7 coupled with the Community Land Model(CLM)Version 4.5(Reg CM4.7-CLM4.5)to investigate the impact of May QXP soil temperature anomalies on June precipitation in eastern China.Causes for different precipitation responses to land surface/subsurface conditions and atmospheric background states in four years were analyzed.The results indicate that warm surface and soil temperature anomalies over the QXP in May led to increased precipitation in the southern Yangtze River basin(SYRB)in June.Due to soil temperature memory,the QXP warming persisted into June,sustaining a negative geopotential height anomaly at 500 h Pa above the QXP.Concurrently,negative and positive height anomalies developed over northern China and the Sea of Japan.The corresponding cyclonic anomaly in the mid-to-lower troposphere over QXP enhanced monsoonal moisture transport in May,and the persistent soil temperature anomaly over QXP sustained moisture convergence over southern China in June,resulting in increased precipitation there.Of the four years examined,both the precipitation response in the SYRB and the intensity of the associated wave train pattern are the strongest in 1998.The combined effect of land surface conditions in May and the atmospheric circulation background in June influenced the precipitation responses.Thermal conditions affected snow cover variations and consequently the radiative balance in the western QXP,causing stronger low-level atmospheric responses in 1998 compared to other years.Additionally,the position of the westerly jet influenced the propagation of atmospheric anomalies,contributing to the different responses in the mid-to-high troposphere.The above findings underscore the role of spring soil temperature anomalies over the QXP as a source of predictability for precipitation in eastern China at the subseasonal timescale.展开更多
Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the ...Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the economy.In recent years,the sea surface temperature(SST)trend factor has been used to construct regression models for summer precipitation.In this study,through correlation analysis,winter SST anomaly predictors and the winter Central Pacific SST trend predictor(CPT)are identified as closely related to the following MLYR summer precipitation(YRSP).CPT can influence YRSP by inducing anomalous circulations over the North Pacific,guiding warm and moist air northward,and inhibiting the development of the anomalous anticyclone over the Northwest Pacific.This has improved the predictive skill of the seasonal regression model for YRSP.After incorporating the CPT,the correlation coefficient of the YRSP regression model improved by 40%,increasing from 0.45 to 0.63,and the root mean squared error decreased by 22%,from 1.15 to 0.90.展开更多
The time series of the sea surface temperature(SST)anomaly,covering the eastern (western)equatorial Pacific,central Indian Ocean,Arabian Sea.Bay of Bengal and South China Sea(SCS),have been analyzed by using wavelet t...The time series of the sea surface temperature(SST)anomaly,covering the eastern (western)equatorial Pacific,central Indian Ocean,Arabian Sea.Bay of Bengal and South China Sea(SCS),have been analyzed by using wavelet transform.Results show that there exists same interdeeadal variability of SST in the tropical Pacific and tropical Indian Ocean,and also show that the last decadal abrupt change occurred in the 1970s.On the interannual time scale,there is a similar interannual variability among the equatorial central Indian Ocean and the adjacent three sea basins(Arabian Sea.Bay of Bengal and South China Sea).but the SST interannual changes of the Indian Ocean lagged 4—5 months behind that of the equatorial central-east Pacific.Meanwhile, the interannual variability and long-range change between SST anomaly and Indian summer monsoon rainfall in recent decades have been explained and analyzed.It indicates that there existed a wet(dry)period in India when the tropical SST was lower(higher)than normal,but there was a lag of phase between them.展开更多
The connection between rainfall over topographic regions and their downstream areas represents a phenomenon of great concern in atmospheric research.Focusing on the rainfall events of the past two decades,we analyzed ...The connection between rainfall over topographic regions and their downstream areas represents a phenomenon of great concern in atmospheric research.Focusing on the rainfall events of the past two decades,we analyzed the impact of rainfall over the Northeastern Slope of the Tibetan Plateau(NSTP)on rainfall in downstream areas.We discovered that rainfall followed two propagation routes,guided by two modes related to the three-dimensional circulation structure.In the first mode,dominated by cold(warm)anomalies along the west(east)direction,rainfall over the NSTP was concentrated between an upstream cyclonic and a downstream anti-cyclonic anomalous circulation(an upstream trough and a downstream ridge).This pattern was accompanied by upper-level divergence,low-level convergence,a deep moist layer,and a vertical updraft.As a consequence of the eastward movement of the trough-ridge system associated with the coldwarm anomalies,the rainfall over the NSTP moved eastward along 37°-40°N,reaching North China after about 36 h.In the second mode,the circulation structure was also dominated by cold-warm anomalies but rotated clockwise,introducing cold anomalies to the northeast and warm anomalies to the east of the plateau.Following the southeastward movement of the circulation structure,rainfall concentrated upstream of the anti-cyclonic circulation around the warm center before moving southeastward to the Sichuan Basin along the eastern edge of the plateau after 30-36 h.The findings of this study could broaden the understanding of rainfall-related teleconnection between two distant regions and offer helpful guidance for identifying early signals of rainfall disasters over the Chinese mainland.展开更多
[Objective] This study aimed to analyze the characteristics of temperature variation in Zhangqiu City during the past 30 years. [Method] Variation characteristics of average annual maximum temperature, average annual ...[Objective] This study aimed to analyze the characteristics of temperature variation in Zhangqiu City during the past 30 years. [Method] Variation characteristics of average annual maximum temperature, average annual temperature and average annual minimum temperature in Zhangqiu City during the past 30 years were analyzed by using related temperature data during 1981 -2010 collected from National Meteorological Observation Station in Zhangqiu. [Result] Average annual maximum temperature, average annual temperature and average annual minimum temperature in Zhangqiu City showed an upward trend; average annual minimum temperature showed the most significant increasing tendency, with a tendency rate of 1.347 ℃/10 a; followed by average annual temperature; average annual maximum temperature showed the slowest increasing tendency, with a tendency rate of 0.062 ℃/10 a, indicating that the increase of average annual temperature mainly depended on the contribution of average annual minimum temperature. [Conclusion] This study provides reference and scientific basis for climate change monitoring, diagnosis, assessment, forecast and decision-making in Zhangqiu City.展开更多
A modified and improved primitive equation numerical model with p-sigma incorporated vertical coordinates is used to simulate the effects of different sea surface temperature distributions over the western Pacific on ...A modified and improved primitive equation numerical model with p-sigma incorporated vertical coordinates is used to simulate the effects of different sea surface temperature distributions over the western Pacific on the summer monsoon properties. The different sea surface temperature (SST) distributions are automatically generated in the time integrations by using two different SST models, one of which is called the deep ocean model (DOM) and the other the shallow ocean model (SOM). The SST generated by the DOM has the distribution pattern of the initial SST which is similar to the pattern in the cold water years over the western Pacific, while the SST generated by the SOM has the pattern similar to that in the warm water years. The differences between the experimental results by using DOM and SOM are analyzed in detail. The analyses indicate that the most basic and important characteristics of the summer monsoon climate can be simulated successfully in both experiments, that means the climatic properties in the monsoonal climate regions are mainly determined by the seasonal heating, the contrast between the land and the sea, the topography, and the physical properties of the underlying surfaces. However, the differences between the two experiments tell us that the climatic properties in the summer monsoon regions in the cold water year and the warm water year do differ from each other in details. In the warm water year, the thermal contrast between the land and the sea becomes weaker. Over the warm water area, the upward motions are induced and the dynamical conditions favorable for the convective activities are formed, the Somali low-level cross equatorial current is somewhat weakened, while the cross equatorial currents, east of 90°E, are strongly strengthened, the precipitation amount in the tropical regions largely increases, and the precipitation over the coastal regions increases, too. However the precipitation over the southeast China and its coastal area decreases. The precipitation amount mainly depends on the strength of the convective activity.展开更多
Anomalous changes of zonal wind quasi-biennial oscillation(QBO)in winter 2015−2016 have received close attention.Combining radiosonde and satellite observations and reanalysis data,we investigate anomalous changes in ...Anomalous changes of zonal wind quasi-biennial oscillation(QBO)in winter 2015−2016 have received close attention.Combining radiosonde and satellite observations and reanalysis data,we investigate anomalous changes in temperature and ozone QBOs from the lower to middle stratosphere.As wind shear direction is reversed due to unexpected changes of zonal wind QBO at about 24−30 km,the shortest cold phase at 21−27 km appears in temperature QBO.This is different from the completely interrupted westward phase in zonal wind QBO,while the longest cold phase above almost 27 km lasts for 2−3 years from 2015 to 2017,owing to the absence of corresponding warm phase.Meridional scale reduction of temperature QBO causes a small temperature anomaly,thus the thermal wind relationship looks seemingly different from that in the other regular QBO cycles.QBO in the ozone mixing ratio anomaly shows a double-peak with inverse phase,and its phase below(above)30 km is in agreement with(opposite to)the phase of temperature QBO because of different control mechanisms of ozone.Following temperature QBO variation,QBO in the ozone mixing ratio anomaly exhibits a less positive phase at 20−30 km in 2016−2017,and a very long positive phase above 30 km from 2015 to 2017.QBO in total column ozone shows a small peak in winter 2016−2017 since ozone is mainly concentrated at 20 to 30 km.Anomalous changes of temperature and ozone QBOs due to unexpected QBO zonal wind variation can be well-explained according to thermal wind balance and thermodynamic balance.展开更多
Based on the simple ocean data assimilation(SODA) reanalysis dataset from the University of Maryland and the method of Empirical Orthogonal Functions(EOF),the characteristics of interannual and interdecadal variabilit...Based on the simple ocean data assimilation(SODA) reanalysis dataset from the University of Maryland and the method of Empirical Orthogonal Functions(EOF),the characteristics of interannual and interdecadal variabilities of the equatorial Pacific subsurface oceanic temperature anomaly(SOTA) are captured.The first and second modes of the equatorial Pacific SOTA in the interannual and interdecadal variations are found respectively and the effect of the second mode on the ENSO cycle is discussed.Results show that the first mode of SOTA's interannual and interdecadal variabilities exhibit a dipole pattern,indicating that the warm and cold temperature anomalies appear simultaneously in the equatorial subsurface Pacific.The second mode shows coherent large-scale temperature anomalies in the equatorial subsurface Pacific,which is a dominant mode in the evolution of ENSO cycle.The temporal series of the second mode has a significant lead correlation with the Ni?o-3.4 index,which can make a precursory prediction signal for ENSO.The function of this prediction factor in SOTA is verified by composite and case analyses.展开更多
The dominant patterns of the winter(December-February)surface air temperature anomalies(SATAs)over Central Asia(CA)are investigated in this study.The first two leading modes revealed by empirical orthogonal function(E...The dominant patterns of the winter(December-February)surface air temperature anomalies(SATAs)over Central Asia(CA)are investigated in this study.The first two leading modes revealed by empirical orthogonal function(EOF)analysis represent the patterns by explaining 74%of the total variance.The positive phase of EOF1 is characterized by a monopole pattern,corresponding to cold SATAs over CA,while the positive phase of EOF2 shows a meridional dipole pattern with warm and cold SATAs over northern and southern CA.EOF1 is mainly modulated by the negative phase of the Arctic Oscillation(AO)in the troposphere,and the negative AO phase may be caused by the downward propagation of the precursory anomalies of the stratospheric polar vortex.EOF2 is mainly influenced by the Ural blocking pattern and the winter North Atlantic Oscillation(NAO).The SATAs associated with EOF2 can be attributed to a dipole-like pattern of geopotential height anomalies over CA.The dipole-like pattern is mainly caused by the Ural blocking pattern,and the NAO can also contribute to the northern part of the dipole.展开更多
The zonal averages of temperature (the so-called normal temperatures) for numerous parallels of latitude published between 1852 and 1913 by Dove, Forbes, Ferrel, Spitaler, Batchelder, Arrhenius, von Bezold, Hopfner, v...The zonal averages of temperature (the so-called normal temperatures) for numerous parallels of latitude published between 1852 and 1913 by Dove, Forbes, Ferrel, Spitaler, Batchelder, Arrhenius, von Bezold, Hopfner, von Hann, and Börnstein were used to quantify the global (spherical) and spheroidal mean near-surface temperature of the terrestrial atmosphere. Only the datasets of Dove and Forbes published in the 1850s provided global averages below 〈T〉=14°C, mainly due to the poor coverage of the Southern Hemisphere by observations during that time. The global averages derived from the distributions of normal temperatures published between 1877 and 1913 ranged from 〈T〉=14.0°C (Batchelder) to 〈T〉=15.1°C (Ferrel). The differences between the global and the spheroidal mean near-surface air temperature are marginal. To examine the uncertainty due to interannual variability and different years considered in the historic zonal mean temperature distributions, the historical normal temperatures were perturbed within ±2σ to obtain ensembles of 50 realizations for each dataset. Numerical integrations of the perturbed distributions indicate uncertainties in the global averages in the range of ±0.3°C to ±0.6°C and depended on the number of available normal temperatures. Compared to our results, the global mean temperature of 〈T〉=15.0°C published by von Hann in 1897 and von Bezold in 1901 and 1906 is notably too high, while 〈T〉=14.4°C published by von Hann in 1908 seems to be more adequate within the range of uncertainty. The HadCRUT4 record provided 〈T〉≌?13.7°C for 1851-1880 and 〈T〉=13.6°C for 1881-1910. The Berkeley record provided 〈T〉=13.6°C and 〈T〉≌?13.5°C for these periods, respectively. The NASA GISS record yielded 〈T〉=13.6°C for 1881-1910 as well. These results are notably lower than those based on the historic zonal means. For 1991-2018, the HadCRUT4, Berkeley, and NASA GISS records provided 〈T〉=14.4°C, 〈T〉=14.5°C, and 〈T〉=14.5°C, respectively. The comparison of the 1991-2018 globally averaged near-surface temperature with those derived from distributions of zonal temperature averages for numerous parallels of latitude suggests no change for the past 100 years.展开更多
Based on an empirical orthogonal function （EOF） analysis of the monthly NCEP Optimum Interpolation Sea Surface Temperature （OISST） data in the South China Sea （SCS） after removing the climatological mean and tre...Based on an empirical orthogonal function （EOF） analysis of the monthly NCEP Optimum Interpolation Sea Surface Temperature （OISST） data in the South China Sea （SCS） after removing the climatological mean and trends of SST, over the period of January 1982 to October 2003, the corresponding TCF correlates best with the Dipole Mode Index （DMI）, Nino1＋2, Nino3.4, Nino3, and Niflo4 indices with time lags of 10, 3, 6, 5, and 6 months, respectively. Thus, a statistical hindcasts in the prediction model are based on a canonical correlation analysis （CCA） model using the above indices as predictors spanning from 1993/1994 to 2003/2004 with a 1-12 month lead time after the canonical variants are calculated, using data from the training periods from January 1982 to December1992. The forecast model is successful and steady when the lead times are 1-12 months. The SCS warm event in 1998 was successfully predicted with lead times from 1-12 months irrespective of the strength or time extent. The prediction ability for SSTA is lower during weak ENSO years, in which other local factors should be also considered as local effects play a relatively important role in these years. We designed the two forecast models： one using both DMI and Nino indices and the other using only Nino indices without DMI, and compared the forecast accuracies of the two cases. The spatial distributions of forecast accuracies show different confidence areas. By turning off the DMI, the forecast accuracy is lower in the coastal areas off the Philippines in the SCS, suggesting some teleconnection may occur with the Indian Ocean in this area. The highest forecast accuracies occur when the forecast interval is five months long without using the DMI, while using both of Nino indices and DMI, the highest accuracies occur when the forecast interval time is eight months, suggesting that the Nino indices dominate the interannual variability of SST anomalies in the SCS. Meanwhile the forecast accuracy is evaluated over an independent test period of more than 11 years （1993/94 to October 2004） by comparing the model performance with a simple prediction strategy involving the persistence of sea surface temperature anomalies over a 1-12 month lead time （the persisted prediction）. Predictions based on the CCA model show a significant improvement over the persisted prediction, especially with an increased lead time （longer than 3 months）. The forecast model performs steadily and the forecast accuracy, i.e., the correlation coefficients between the observed and predicted SSTA in the SCS are about 0.5 in most middle and southern SCS areas, when the thresholds are greater than the 95% confidence level. For all 1 to 12 month lead time forecasts, the root mean square errors have a standard deviation of about 0.2. The seasonal differences in the prediction performance for the 1-12 month lead time are also examined.展开更多
Since the mid-20th century,the Mongolian Plateau(MP)has experienced decadal droughts coupled with extreme heatwaves,severely affecting regional ecology and social development.However,the mechanisms behind these decada...Since the mid-20th century,the Mongolian Plateau(MP)has experienced decadal droughts coupled with extreme heatwaves,severely affecting regional ecology and social development.However,the mechanisms behind these decadalscale compound heatwavedrought events remain debated.Here,using reconstructions and simulations from the Community Earth System Model Last Millennium Ensemble,we demonstrate that,over the last millennium,decadal droughts on the MP occurred under both warm and cold conditions,differing from recent compound heatwavedrought events.We found that by examining temperature changes during these drought periods,the distinct influences of external forcings and internal variability can be simply and effectively distinguished.Specifically,colddry events were primarily driven by volcanic eruptions that weakened the East Asian summer monsoon and midlatitude westerlies,reducing moisture transport to the MP.In contrast,warmdry events were predominantly induced by internal variability,notably the negative phase of the Atlantic Multidecadal Oscillation and the expansion of the Barents Sea ice extent.The recent extreme compound event was probably influenced by the combined effects of anthropogenic forcings and internal variability.These findings deepen our understanding of how external forcings and internal variability affect decadal drought events on the MP and highlight that recent compound events are unprecedented in the context of the last millennium.展开更多
The extreme high temperature anomaly (EHTA) events in a region are one of the most important climatic parameters to make climate assessment of the trend of regional climate change. The diagnosis and analysis of the EH...The extreme high temperature anomaly (EHTA) events in a region are one of the most important climatic parameters to make climate assessment of the trend of regional climate change. The diagnosis and analysis of the EHTA event in Zhejiang Province in East China in 2022 show that the event has set the rarest record in this region in the past 71 years from both time and space perspectives. The results of Mann-Kendall trend analysis showed that the mean annual high temperature days in Zhejiang Province had a sudden change. The sudden change occurred around 2004, and the trend was rising after the sudden change.展开更多
Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961-2002. A set of indices of warm extremes, cold extremes and daily tempera...Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961-2002. A set of indices of warm extremes, cold extremes and daily temperature range （DTR） extremes was studied with a focus on trends. The results showed that the frequency of warm extremes （F WE） increased obviously in most parts of China, and the intensity of warm extremes （I WE） increased significantly in northern China. The opposite distribution was found in the frequency and intensity of cold extremes. The frequency of high DTR extremes was relatively uniform with that of intensity： an obvious increasing trend was located over western China and the east coast, while significant decreases occurred in central, southeastern and northeastern China; the opposite distribution was found for low DTR extreme days. Seasonal trends illustrated that both F WE and I WE showed signifi- cant increasing trends, especially over northeastern China and along the Yangtze Valley basin in spring and winter. A correlation technique was used to link extreme temperature anomalies over China with global temperature anomalies. Three key regions were identified, as follows： northeastern China and its coastal areas, the high-latitude regions above 40~0N, and southwestern China and the equatorial eastern Pacific.展开更多
The vertical structures of atmospheric temperature anomalies associated with El Nio are simulated with a spectrum atmospheric general circulation model developed by LASG/IAP （SAMIL）. Sensitivity of the model’s resp...The vertical structures of atmospheric temperature anomalies associated with El Nio are simulated with a spectrum atmospheric general circulation model developed by LASG/IAP （SAMIL）. Sensitivity of the model’s response to convection scheme is discussed. Two convection schemes, i.e., the revised Zhang and Macfarlane （RZM） and Tiedtke （TDK） convection schemes, are employed in two sets of AMIP-type （Atmospheric Model Intercomparison Project） SAMIL simulations, respectively. Despite some deficiencies in the upper troposphere, the canonical El Nio-related temperature anomalies characterized by a prevailing warming throughout the tropical troposphere are well reproduced in both simulations. The performance of the model in reproducing temperature anomalies in ＂atypical＂ El Nio events is sensitive to the convection scheme. When employing the RZM scheme, the warming center over the central-eastern tropical Pacific and the strong cooling in the western tropical Pacific at sea surface level are underestimated. The quadru-pole temperature anomalies in the middle and upper troposphere are also obscured. The result of employing the TDK scheme resembles the reanalysis and hence shows a better performance. The simulated largescale circulations associated with atypical El Nio events are also sensitive to the convection schemes. When employing the RZM scheme, SAMIL failed in capturing the classical Southern Oscillation pattern. In accordance with the unrealistic anomalous Walker circulation and the upper tropospheric zonal wind changes, the deficiencies of the precipitation simulation are also evident. These results demonstrate the importance of convection schemes in simulating the vertical structure of atmospheric temperature anomalies associated with El Nio and should serve as a useful reference for future improvement of SAMIL.展开更多
The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly （SOTA） and the associated anomalous atmospheric circulation over the Asian North Pacific during the E1 Nifio-Southern Oscilla...The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly （SOTA） and the associated anomalous atmospheric circulation over the Asian North Pacific during the E1 Nifio-Southern Oscillation （ENSO） were investigated using National Centers for Environmental Prediction/ National Center for Atmospheric Research （NCEP/NCAR） atmospheric reanalysis data and simple ocean data simulation （SODA）. The relationship between the ENSO and the climate of China was revealed. The main results indicated the following： 1） there are two ENSO modes acting on the subsurface tropical Pacific. The first mode is related to the mature phase of ENSO, which mainly appears during winter. The second mode is associated with a transition stage of the ENSO developing or decaying, which mainly occurs during summer; 2） during the mature phase of E1Nifio, the meridionality of the atmosphere in the mid-high latitude increases, the Aleutian low and high pressure ridge over Lake Baikal strengthens, northerly winds prevail in northern China, and precipitation in northern China decreases significantly. The ridge of the Ural High strengthens during the decaying phase of E1 Nifio, as atmospheric circulation is sustained during winter, and the northerly wind anomaly appears in northern China during summer. Due to the ascending branch of the Walker circulation over the western Pacific, the western Pacific Subtropical High becomes weaker, and south-southeasterly winds prevail over southern China. As a result, less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia. The flood disaster that occurred south of Changjiang River can be attributed to this. The La Nifm event causes an opposite, but weaker effect; 3） the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport. This is known as the ＂atmospheric-bridge＂, where the energy anomaly within the tropical Pacific transfers to the mid-high latitude in the northern Pacific through Hadley cells and Rossby waves, and to the western Pacific-eastern Indian Ocean through Walker circulation. This research also discusses the special air-sea boundary processes during the ENSO events in the tropical Pacific, and indicates that the influence of the subsurface water of the tropical Pacific on the atmospheric circulation may be realized through the sea surface temperature anomalies of the mixed water, which contact the atmosphere and transfer the anomalous heat and moisture to the atmosphere directly. Moreover, the reason for the heavy flood within the Changjiang River during the summer of 1998 is reviewed in this paper.展开更多
文摘Large-scale water transport is one of the key factors that affect sea surface temperature anomaly（SSTA） in the eastern equatorial Pacific（EEP）.The relationship between the wave transport in the tropical Pacific and the SSTA in the EEP is examined by different methods,including band-pass filtering,period analysis,correlation analysis,significant analysis,and empirical orthogonal function（EOF） analysis.We have found that the eastward shift of the wave transport anomaly in the tropical Pacific,with a period of 2 a and enhancing the transport of warm waters from the western Pacific warm pool,precedes the increase of sea surface temperature（SST） in the EEP.The wave transport and the SSTA in the EEP have a maximum correlation of 0.65 with a time-lag of 6 months（transport variation precedes the temperature）.The major periods（3.7 a and 2.45 a） of the wave transport variability,as revealed by the EOF analysis,appear to be consistent with the SSTA oscillation cycle in the EEP.Based on the first occurrence of a significant SSTA in the Ni？o 3 region（5°S–5°N,90°–150°W）,two types of warm events are defined.The wave transport anomalies in two types present predominantly the west anomaly in the tropical Pacific,it is that the wave transport continues transport warm water from west to east before the onset of the warm event.The impact of wave-induced water transport on the SSTA in the EEP is confirmed by the heat flux of the wave transport.The wave transport exerts significant effect on the SSTA variability in the EEP and thus is not neglectable in the further studies.
基金supported by the National Natural Science Founda-tion of China[grant numbers 41630530 and 41861144015]the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”.
文摘Based on reanalysis data from 1979 to 2016,this study focuses on the sea surface temperature(SST)anomaly of the tropical North Atlantic(TNA)in El Nino decaying years.The TNA SST exhibits a clear warm trend during this period.The composite result for 10 El Nino events shows that the TNA SST anomaly reaches its maximum in spring after the peak of an El Nino event and persists until summer.In general,the anomaly is associated with three factors-namely,El Nino,the North Atlantic Oscillation(NAO),and a long-term trend,leading to an increase in local SST up to 0.4℃,0.3℃,and 0.35℃,respectively.A comparison between 1983 and 2005 indicates that the TNA SST in spring is affected by El Niño,as well as the local SST in the preceding winter,which may involve a long-term trend signal.In addition,the lead-lag correlation shows that the NAO leads the TNA SST by 2-3 months.By comparing two years with an opposite phase of the NAO in winter(i.e.,1992 and 2010),the authors further demonstrate that the NAO is another important factor in regulating the TNA SST anomaly.A negative phase of the NAO in winter will reinforce the El Nino forcing substantially,and vise versa.In other words,the TNA SST anomaly in the decaying years is more evident if the NAO is negative with El Nino.Therefore,the combined effects of El Nino and the NAO must be considered in order to fully understand the TNA SST variability along with a long-term trend.
基金Specialized Science Project for Public Welfare Industries(Meteorology)(GYHY200906016)State Key Program of National Natural Science Foundation of China(41230528)
文摘By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there.
基金supported by the National Natural Science Foundation of China(Grant No.42475191)the Fundamental Research Funds for the Central Universities-Cemac‘Geo X’Interdisciplinary Program(Grant No.2024300245)the Postgraduate Research&Practice Innovation Program of Jiangsu Province。
文摘Global temperature has increased at a rapid rate in recent decades,and the warming rate at night is observed higher than that during the daytime among different regions.Nighttime anomalous high temperatures may pose an additional risk to human health and society.Nevertheless,less research has explored the spatiotemporal trend and the local atmospheric mechanism of nocturnal temperature anomaly around the world.Here,we investigate the spatiotemporal trend of nighttime temperature anomaly(NTA)from 1961 to 2023,and analyze the underlying physical mechanism related to different extents of positive temperature anomaly.We find that NTA showed a significantly increased trend worldwide,with an increasing rate of0.21°C/decade.At the continental scale,NTA has increased faster in North America,Asia,and Europe.The occurrence of positive NTA is generally associated with local increased cloud cover,precipitation,and humidity,which contribute to enhanced downward longwave radiation and greenhouse effect at night.On the inter-annual scale,NTA is positively related to the preceding winter Oceanic Ni?o Index,indicating the possible modulation of El Ni?o-Southern Oscillation on the global nocturnal temperature.Our results could help to understand the variation and influence mechanism of anomalous nighttime temperature in recent decades,and inform the forecast of and response to hot nights.
基金Supported by the National Natural Science Foundation of China(U2442207 and 42075115)。
文摘Spring land surface temperature/subsurface soil temperature over the Qinghai-Xizang Plateau(QXP)substantially impacts downstream precipitation on subseasonal timescales.However,how well can climate models reproduce this impact and its assoicated interannual variation remains unclear.This study utilized the Regional Climate Model(Reg CM)Version 4.7 coupled with the Community Land Model(CLM)Version 4.5(Reg CM4.7-CLM4.5)to investigate the impact of May QXP soil temperature anomalies on June precipitation in eastern China.Causes for different precipitation responses to land surface/subsurface conditions and atmospheric background states in four years were analyzed.The results indicate that warm surface and soil temperature anomalies over the QXP in May led to increased precipitation in the southern Yangtze River basin(SYRB)in June.Due to soil temperature memory,the QXP warming persisted into June,sustaining a negative geopotential height anomaly at 500 h Pa above the QXP.Concurrently,negative and positive height anomalies developed over northern China and the Sea of Japan.The corresponding cyclonic anomaly in the mid-to-lower troposphere over QXP enhanced monsoonal moisture transport in May,and the persistent soil temperature anomaly over QXP sustained moisture convergence over southern China in June,resulting in increased precipitation there.Of the four years examined,both the precipitation response in the SYRB and the intensity of the associated wave train pattern are the strongest in 1998.The combined effect of land surface conditions in May and the atmospheric circulation background in June influenced the precipitation responses.Thermal conditions affected snow cover variations and consequently the radiative balance in the western QXP,causing stronger low-level atmospheric responses in 1998 compared to other years.Additionally,the position of the westerly jet influenced the propagation of atmospheric anomalies,contributing to the different responses in the mid-to-high troposphere.The above findings underscore the role of spring soil temperature anomalies over the QXP as a source of predictability for precipitation in eastern China at the subseasonal timescale.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(42175061)。
文摘Studying the causes of summer(June–July–August)precipitation anomalies in the middle and lower reaches of the Yangtze River(MLYR)and accurately predicting rainy season precipitation are important to society and the economy.In recent years,the sea surface temperature(SST)trend factor has been used to construct regression models for summer precipitation.In this study,through correlation analysis,winter SST anomaly predictors and the winter Central Pacific SST trend predictor(CPT)are identified as closely related to the following MLYR summer precipitation(YRSP).CPT can influence YRSP by inducing anomalous circulations over the North Pacific,guiding warm and moist air northward,and inhibiting the development of the anomalous anticyclone over the Northwest Pacific.This has improved the predictive skill of the seasonal regression model for YRSP.After incorporating the CPT,the correlation coefficient of the YRSP regression model improved by 40%,increasing from 0.45 to 0.63,and the root mean squared error decreased by 22%,from 1.15 to 0.90.
基金This work was supported by the National Climbing Project of China and Project 49875016 supported by NSFC.
文摘The time series of the sea surface temperature(SST)anomaly,covering the eastern (western)equatorial Pacific,central Indian Ocean,Arabian Sea.Bay of Bengal and South China Sea(SCS),have been analyzed by using wavelet transform.Results show that there exists same interdeeadal variability of SST in the tropical Pacific and tropical Indian Ocean,and also show that the last decadal abrupt change occurred in the 1970s.On the interannual time scale,there is a similar interannual variability among the equatorial central Indian Ocean and the adjacent three sea basins(Arabian Sea.Bay of Bengal and South China Sea).but the SST interannual changes of the Indian Ocean lagged 4—5 months behind that of the equatorial central-east Pacific.Meanwhile, the interannual variability and long-range change between SST anomaly and Indian summer monsoon rainfall in recent decades have been explained and analyzed.It indicates that there existed a wet(dry)period in India when the tropical SST was lower(higher)than normal,but there was a lag of phase between them.
基金supported by the National Natural Science Foundation of China(Grant No.U2142204 and 42475013)the Beijing Nova Program(Z211100002121100)+1 种基金the National Key Research and Development Program of China(2023YFC3007504)the Science&Technology Development Fund of Chinese Academy of Meteorological Sciences(CAMS)(2022KJ007)。
文摘The connection between rainfall over topographic regions and their downstream areas represents a phenomenon of great concern in atmospheric research.Focusing on the rainfall events of the past two decades,we analyzed the impact of rainfall over the Northeastern Slope of the Tibetan Plateau(NSTP)on rainfall in downstream areas.We discovered that rainfall followed two propagation routes,guided by two modes related to the three-dimensional circulation structure.In the first mode,dominated by cold(warm)anomalies along the west(east)direction,rainfall over the NSTP was concentrated between an upstream cyclonic and a downstream anti-cyclonic anomalous circulation(an upstream trough and a downstream ridge).This pattern was accompanied by upper-level divergence,low-level convergence,a deep moist layer,and a vertical updraft.As a consequence of the eastward movement of the trough-ridge system associated with the coldwarm anomalies,the rainfall over the NSTP moved eastward along 37°-40°N,reaching North China after about 36 h.In the second mode,the circulation structure was also dominated by cold-warm anomalies but rotated clockwise,introducing cold anomalies to the northeast and warm anomalies to the east of the plateau.Following the southeastward movement of the circulation structure,rainfall concentrated upstream of the anti-cyclonic circulation around the warm center before moving southeastward to the Sichuan Basin along the eastern edge of the plateau after 30-36 h.The findings of this study could broaden the understanding of rainfall-related teleconnection between two distant regions and offer helpful guidance for identifying early signals of rainfall disasters over the Chinese mainland.
文摘[Objective] This study aimed to analyze the characteristics of temperature variation in Zhangqiu City during the past 30 years. [Method] Variation characteristics of average annual maximum temperature, average annual temperature and average annual minimum temperature in Zhangqiu City during the past 30 years were analyzed by using related temperature data during 1981 -2010 collected from National Meteorological Observation Station in Zhangqiu. [Result] Average annual maximum temperature, average annual temperature and average annual minimum temperature in Zhangqiu City showed an upward trend; average annual minimum temperature showed the most significant increasing tendency, with a tendency rate of 1.347 ℃/10 a; followed by average annual temperature; average annual maximum temperature showed the slowest increasing tendency, with a tendency rate of 0.062 ℃/10 a, indicating that the increase of average annual temperature mainly depended on the contribution of average annual minimum temperature. [Conclusion] This study provides reference and scientific basis for climate change monitoring, diagnosis, assessment, forecast and decision-making in Zhangqiu City.
基金Supported by the National Fundamental Key Research:"studies on climate dynamics and climate prediction theory."
文摘A modified and improved primitive equation numerical model with p-sigma incorporated vertical coordinates is used to simulate the effects of different sea surface temperature distributions over the western Pacific on the summer monsoon properties. The different sea surface temperature (SST) distributions are automatically generated in the time integrations by using two different SST models, one of which is called the deep ocean model (DOM) and the other the shallow ocean model (SOM). The SST generated by the DOM has the distribution pattern of the initial SST which is similar to the pattern in the cold water years over the western Pacific, while the SST generated by the SOM has the pattern similar to that in the warm water years. The differences between the experimental results by using DOM and SOM are analyzed in detail. The analyses indicate that the most basic and important characteristics of the summer monsoon climate can be simulated successfully in both experiments, that means the climatic properties in the monsoonal climate regions are mainly determined by the seasonal heating, the contrast between the land and the sea, the topography, and the physical properties of the underlying surfaces. However, the differences between the two experiments tell us that the climatic properties in the summer monsoon regions in the cold water year and the warm water year do differ from each other in details. In the warm water year, the thermal contrast between the land and the sea becomes weaker. Over the warm water area, the upward motions are induced and the dynamical conditions favorable for the convective activities are formed, the Somali low-level cross equatorial current is somewhat weakened, while the cross equatorial currents, east of 90°E, are strongly strengthened, the precipitation amount in the tropical regions largely increases, and the precipitation over the coastal regions increases, too. However the precipitation over the southeast China and its coastal area decreases. The precipitation amount mainly depends on the strength of the convective activity.
基金supported by the National Natural Science Foundation of China(through grants 41974176 and 41674151).
文摘Anomalous changes of zonal wind quasi-biennial oscillation(QBO)in winter 2015−2016 have received close attention.Combining radiosonde and satellite observations and reanalysis data,we investigate anomalous changes in temperature and ozone QBOs from the lower to middle stratosphere.As wind shear direction is reversed due to unexpected changes of zonal wind QBO at about 24−30 km,the shortest cold phase at 21−27 km appears in temperature QBO.This is different from the completely interrupted westward phase in zonal wind QBO,while the longest cold phase above almost 27 km lasts for 2−3 years from 2015 to 2017,owing to the absence of corresponding warm phase.Meridional scale reduction of temperature QBO causes a small temperature anomaly,thus the thermal wind relationship looks seemingly different from that in the other regular QBO cycles.QBO in the ozone mixing ratio anomaly shows a double-peak with inverse phase,and its phase below(above)30 km is in agreement with(opposite to)the phase of temperature QBO because of different control mechanisms of ozone.Following temperature QBO variation,QBO in the ozone mixing ratio anomaly exhibits a less positive phase at 20−30 km in 2016−2017,and a very long positive phase above 30 km from 2015 to 2017.QBO in total column ozone shows a small peak in winter 2016−2017 since ozone is mainly concentrated at 20 to 30 km.Anomalous changes of temperature and ozone QBOs due to unexpected QBO zonal wind variation can be well-explained according to thermal wind balance and thermodynamic balance.
基金National Key Basic Research Program of China(2013CB956203)
文摘Based on the simple ocean data assimilation(SODA) reanalysis dataset from the University of Maryland and the method of Empirical Orthogonal Functions(EOF),the characteristics of interannual and interdecadal variabilities of the equatorial Pacific subsurface oceanic temperature anomaly(SOTA) are captured.The first and second modes of the equatorial Pacific SOTA in the interannual and interdecadal variations are found respectively and the effect of the second mode on the ENSO cycle is discussed.Results show that the first mode of SOTA's interannual and interdecadal variabilities exhibit a dipole pattern,indicating that the warm and cold temperature anomalies appear simultaneously in the equatorial subsurface Pacific.The second mode shows coherent large-scale temperature anomalies in the equatorial subsurface Pacific,which is a dominant mode in the evolution of ENSO cycle.The temporal series of the second mode has a significant lead correlation with the Ni?o-3.4 index,which can make a precursory prediction signal for ENSO.The function of this prediction factor in SOTA is verified by composite and case analyses.
基金This work was funded by the National Natural Science Foundation of China[grant numbers 42088101 and 41730964]an Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)[grant number 311021001].
文摘The dominant patterns of the winter(December-February)surface air temperature anomalies(SATAs)over Central Asia(CA)are investigated in this study.The first two leading modes revealed by empirical orthogonal function(EOF)analysis represent the patterns by explaining 74%of the total variance.The positive phase of EOF1 is characterized by a monopole pattern,corresponding to cold SATAs over CA,while the positive phase of EOF2 shows a meridional dipole pattern with warm and cold SATAs over northern and southern CA.EOF1 is mainly modulated by the negative phase of the Arctic Oscillation(AO)in the troposphere,and the negative AO phase may be caused by the downward propagation of the precursory anomalies of the stratospheric polar vortex.EOF2 is mainly influenced by the Ural blocking pattern and the winter North Atlantic Oscillation(NAO).The SATAs associated with EOF2 can be attributed to a dipole-like pattern of geopotential height anomalies over CA.The dipole-like pattern is mainly caused by the Ural blocking pattern,and the NAO can also contribute to the northern part of the dipole.
文摘The zonal averages of temperature (the so-called normal temperatures) for numerous parallels of latitude published between 1852 and 1913 by Dove, Forbes, Ferrel, Spitaler, Batchelder, Arrhenius, von Bezold, Hopfner, von Hann, and Börnstein were used to quantify the global (spherical) and spheroidal mean near-surface temperature of the terrestrial atmosphere. Only the datasets of Dove and Forbes published in the 1850s provided global averages below 〈T〉=14°C, mainly due to the poor coverage of the Southern Hemisphere by observations during that time. The global averages derived from the distributions of normal temperatures published between 1877 and 1913 ranged from 〈T〉=14.0°C (Batchelder) to 〈T〉=15.1°C (Ferrel). The differences between the global and the spheroidal mean near-surface air temperature are marginal. To examine the uncertainty due to interannual variability and different years considered in the historic zonal mean temperature distributions, the historical normal temperatures were perturbed within ±2σ to obtain ensembles of 50 realizations for each dataset. Numerical integrations of the perturbed distributions indicate uncertainties in the global averages in the range of ±0.3°C to ±0.6°C and depended on the number of available normal temperatures. Compared to our results, the global mean temperature of 〈T〉=15.0°C published by von Hann in 1897 and von Bezold in 1901 and 1906 is notably too high, while 〈T〉=14.4°C published by von Hann in 1908 seems to be more adequate within the range of uncertainty. The HadCRUT4 record provided 〈T〉≌?13.7°C for 1851-1880 and 〈T〉=13.6°C for 1881-1910. The Berkeley record provided 〈T〉=13.6°C and 〈T〉≌?13.5°C for these periods, respectively. The NASA GISS record yielded 〈T〉=13.6°C for 1881-1910 as well. These results are notably lower than those based on the historic zonal means. For 1991-2018, the HadCRUT4, Berkeley, and NASA GISS records provided 〈T〉=14.4°C, 〈T〉=14.5°C, and 〈T〉=14.5°C, respectively. The comparison of the 1991-2018 globally averaged near-surface temperature with those derived from distributions of zonal temperature averages for numerous parallels of latitude suggests no change for the past 100 years.
基金Supported by National Natural Science Foundation of China (No. 40706011)the Key Program of Knowledge Innovation Project of Chinese Academy of Sciences (No. KZCX1-YW-12)+2 种基金the National Science Foundation of China (Nos. 405201 and 40074)the International Cooperative Program of the Ministry of Science and Technology (No. 2006DFB21630)by the Open Foundation of Key Laboratory of Marine Science and Numerical Modeling (MASNUM)
文摘Based on an empirical orthogonal function （EOF） analysis of the monthly NCEP Optimum Interpolation Sea Surface Temperature （OISST） data in the South China Sea （SCS） after removing the climatological mean and trends of SST, over the period of January 1982 to October 2003, the corresponding TCF correlates best with the Dipole Mode Index （DMI）, Nino1＋2, Nino3.4, Nino3, and Niflo4 indices with time lags of 10, 3, 6, 5, and 6 months, respectively. Thus, a statistical hindcasts in the prediction model are based on a canonical correlation analysis （CCA） model using the above indices as predictors spanning from 1993/1994 to 2003/2004 with a 1-12 month lead time after the canonical variants are calculated, using data from the training periods from January 1982 to December1992. The forecast model is successful and steady when the lead times are 1-12 months. The SCS warm event in 1998 was successfully predicted with lead times from 1-12 months irrespective of the strength or time extent. The prediction ability for SSTA is lower during weak ENSO years, in which other local factors should be also considered as local effects play a relatively important role in these years. We designed the two forecast models： one using both DMI and Nino indices and the other using only Nino indices without DMI, and compared the forecast accuracies of the two cases. The spatial distributions of forecast accuracies show different confidence areas. By turning off the DMI, the forecast accuracy is lower in the coastal areas off the Philippines in the SCS, suggesting some teleconnection may occur with the Indian Ocean in this area. The highest forecast accuracies occur when the forecast interval is five months long without using the DMI, while using both of Nino indices and DMI, the highest accuracies occur when the forecast interval time is eight months, suggesting that the Nino indices dominate the interannual variability of SST anomalies in the SCS. Meanwhile the forecast accuracy is evaluated over an independent test period of more than 11 years （1993/94 to October 2004） by comparing the model performance with a simple prediction strategy involving the persistence of sea surface temperature anomalies over a 1-12 month lead time （the persisted prediction）. Predictions based on the CCA model show a significant improvement over the persisted prediction, especially with an increased lead time （longer than 3 months）. The forecast model performs steadily and the forecast accuracy, i.e., the correlation coefficients between the observed and predicted SSTA in the SCS are about 0.5 in most middle and southern SCS areas, when the thresholds are greater than the 95% confidence level. For all 1 to 12 month lead time forecasts, the root mean square errors have a standard deviation of about 0.2. The seasonal differences in the prediction performance for the 1-12 month lead time are also examined.
基金supported by the National Natural Science Foundation of China(Grant Nos.42130604)the National Key Research and Development Program of China(Grant No.2023YFF0804704)+2 种基金the National Natural Science Foundation of China(Grant Nos.42105044)Swedish STINT(Grant No.CH2019-8377)the Priority Academic Program Development of Jiangsu Higher Education Institutions(Grant No.164320H116)。
文摘Since the mid-20th century,the Mongolian Plateau(MP)has experienced decadal droughts coupled with extreme heatwaves,severely affecting regional ecology and social development.However,the mechanisms behind these decadalscale compound heatwavedrought events remain debated.Here,using reconstructions and simulations from the Community Earth System Model Last Millennium Ensemble,we demonstrate that,over the last millennium,decadal droughts on the MP occurred under both warm and cold conditions,differing from recent compound heatwavedrought events.We found that by examining temperature changes during these drought periods,the distinct influences of external forcings and internal variability can be simply and effectively distinguished.Specifically,colddry events were primarily driven by volcanic eruptions that weakened the East Asian summer monsoon and midlatitude westerlies,reducing moisture transport to the MP.In contrast,warmdry events were predominantly induced by internal variability,notably the negative phase of the Atlantic Multidecadal Oscillation and the expansion of the Barents Sea ice extent.The recent extreme compound event was probably influenced by the combined effects of anthropogenic forcings and internal variability.These findings deepen our understanding of how external forcings and internal variability affect decadal drought events on the MP and highlight that recent compound events are unprecedented in the context of the last millennium.
文摘The extreme high temperature anomaly (EHTA) events in a region are one of the most important climatic parameters to make climate assessment of the trend of regional climate change. The diagnosis and analysis of the EHTA event in Zhejiang Province in East China in 2022 show that the event has set the rarest record in this region in the past 71 years from both time and space perspectives. The results of Mann-Kendall trend analysis showed that the mean annual high temperature days in Zhejiang Province had a sudden change. The sudden change occurred around 2004, and the trend was rising after the sudden change.
基金supported by the National Natural Science Foundation of China under Grant Nos. 40675042, 40901016 and 40805041
文摘Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961-2002. A set of indices of warm extremes, cold extremes and daily temperature range （DTR） extremes was studied with a focus on trends. The results showed that the frequency of warm extremes （F WE） increased obviously in most parts of China, and the intensity of warm extremes （I WE） increased significantly in northern China. The opposite distribution was found in the frequency and intensity of cold extremes. The frequency of high DTR extremes was relatively uniform with that of intensity： an obvious increasing trend was located over western China and the east coast, while significant decreases occurred in central, southeastern and northeastern China; the opposite distribution was found for low DTR extreme days. Seasonal trends illustrated that both F WE and I WE showed signifi- cant increasing trends, especially over northeastern China and along the Yangtze Valley basin in spring and winter. A correlation technique was used to link extreme temperature anomalies over China with global temperature anomalies. Three key regions were identified, as follows： northeastern China and its coastal areas, the high-latitude regions above 40~0N, and southwestern China and the equatorial eastern Pacific.
基金supported by the National Natural Science Foundation of China (40890054, 40821092, 90711004)R&D Spe-cial Fund for Public Welfare Industry (meteorol-ogy)(GYHY200706010)National Key Technologies R&D Program (2007BAC29B03)
文摘The vertical structures of atmospheric temperature anomalies associated with El Nio are simulated with a spectrum atmospheric general circulation model developed by LASG/IAP （SAMIL）. Sensitivity of the model’s response to convection scheme is discussed. Two convection schemes, i.e., the revised Zhang and Macfarlane （RZM） and Tiedtke （TDK） convection schemes, are employed in two sets of AMIP-type （Atmospheric Model Intercomparison Project） SAMIL simulations, respectively. Despite some deficiencies in the upper troposphere, the canonical El Nio-related temperature anomalies characterized by a prevailing warming throughout the tropical troposphere are well reproduced in both simulations. The performance of the model in reproducing temperature anomalies in ＂atypical＂ El Nio events is sensitive to the convection scheme. When employing the RZM scheme, the warming center over the central-eastern tropical Pacific and the strong cooling in the western tropical Pacific at sea surface level are underestimated. The quadru-pole temperature anomalies in the middle and upper troposphere are also obscured. The result of employing the TDK scheme resembles the reanalysis and hence shows a better performance. The simulated largescale circulations associated with atypical El Nio events are also sensitive to the convection schemes. When employing the RZM scheme, SAMIL failed in capturing the classical Southern Oscillation pattern. In accordance with the unrealistic anomalous Walker circulation and the upper tropospheric zonal wind changes, the deficiencies of the precipitation simulation are also evident. These results demonstrate the importance of convection schemes in simulating the vertical structure of atmospheric temperature anomalies associated with El Nio and should serve as a useful reference for future improvement of SAMIL.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-Q11-02)the CAS Strategic Priority Research Program (No. XDA05090404)the National Basic Research Program of China (973 Program) (No. 2012CB417401)
文摘The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly （SOTA） and the associated anomalous atmospheric circulation over the Asian North Pacific during the E1 Nifio-Southern Oscillation （ENSO） were investigated using National Centers for Environmental Prediction/ National Center for Atmospheric Research （NCEP/NCAR） atmospheric reanalysis data and simple ocean data simulation （SODA）. The relationship between the ENSO and the climate of China was revealed. The main results indicated the following： 1） there are two ENSO modes acting on the subsurface tropical Pacific. The first mode is related to the mature phase of ENSO, which mainly appears during winter. The second mode is associated with a transition stage of the ENSO developing or decaying, which mainly occurs during summer; 2） during the mature phase of E1Nifio, the meridionality of the atmosphere in the mid-high latitude increases, the Aleutian low and high pressure ridge over Lake Baikal strengthens, northerly winds prevail in northern China, and precipitation in northern China decreases significantly. The ridge of the Ural High strengthens during the decaying phase of E1 Nifio, as atmospheric circulation is sustained during winter, and the northerly wind anomaly appears in northern China during summer. Due to the ascending branch of the Walker circulation over the western Pacific, the western Pacific Subtropical High becomes weaker, and south-southeasterly winds prevail over southern China. As a result, less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia. The flood disaster that occurred south of Changjiang River can be attributed to this. The La Nifm event causes an opposite, but weaker effect; 3） the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport. This is known as the ＂atmospheric-bridge＂, where the energy anomaly within the tropical Pacific transfers to the mid-high latitude in the northern Pacific through Hadley cells and Rossby waves, and to the western Pacific-eastern Indian Ocean through Walker circulation. This research also discusses the special air-sea boundary processes during the ENSO events in the tropical Pacific, and indicates that the influence of the subsurface water of the tropical Pacific on the atmospheric circulation may be realized through the sea surface temperature anomalies of the mixed water, which contact the atmosphere and transfer the anomalous heat and moisture to the atmosphere directly. Moreover, the reason for the heavy flood within the Changjiang River during the summer of 1998 is reviewed in this paper.
