An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a...An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a period of weak trends.The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage,the areas north to Victoria Land and Wilkes Land,and the central parts of the South Indian sector.The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector.The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.展开更多
The meridional gradient of surface air temperature associated with“Warm Arctic–Cold Eurasia”(GradTAE)is closely related to climate anomalies and weather extremes in the mid-low latitudes.However,the Climate Forecas...The meridional gradient of surface air temperature associated with“Warm Arctic–Cold Eurasia”(GradTAE)is closely related to climate anomalies and weather extremes in the mid-low latitudes.However,the Climate Forecast System Version 2(CFSv2)shows poor capability for GradTAE prediction.Based on the year-to-year increment approach,analysis using a hybrid seasonal prediction model for GradTAE in winter(HMAE)is conducted with observed September sea ice over the Barents–Kara Sea,October sea surface temperature over the North Atlantic,September soil moisture in southern North America,and CFSv2 forecasted winter sea ice over the Baffin Bay,Davis Strait,and Labrador Sea.HMAE demonstrates good capability for predicting GradTAE with a significant correlation coefficient of 0.84,and the percentage of the same sign is 88%in cross-validation during 1983−2015.HMAE also maintains high accuracy and robustness during independent predictions of 2016−20.Meanwhile,HMAE can predict the GradTAE in 2021 well as an experiment of routine operation.Moreover,well-predicted GradTAE is useful in the prediction of the large-scale pattern of“Warm Arctic–Cold Eurasia”and has potential to enhance the skill of surface air temperature occurrences in the east of China.展开更多
Subduction process is a dynamical bridge for the exchanges of heat between the atmosphere and subsurface ocean water,which is regarded as a central proxy for the ocean climate studies.Given its key indicator in climat...Subduction process is a dynamical bridge for the exchanges of heat between the atmosphere and subsurface ocean water,which is regarded as a central proxy for the ocean climate studies.Given its key indicator in climate signals,it is of importance to examine the ability of a model to simulate the global subduction rate before investigating the climate dynamics.In this paper,we evaluated the ability of 21 climate models from Coupled Model Intercomparison Project Phase 6(CMIP6)in simulating the subduction rate.In general,the simulation ability of the models to the subduction climatology is better than that to the long-term variation trend.Based on the comprehensive analysis of climatology distribution and long-term trend of the subduction rate,GISS-E2-1-G performs better in reproducing the subduction rate climatology and IPSL-CM6A-LR can simulate positive long-term trend for both the global mean subduction rate and the lateral induction term in the Antarctic Circumpolar Current(ACC)region.However,it is still challenging to capture both the distribution characteristics of the subduction climatology and the long-term temporal trend for the 21 CMIP6 models.In addition,the model results demonstrate that,the ACC area is the major region contributing to the long-term trend of the global mean subduction rate.The analysis in this paper indicates that the poor simulation ability of reproducing the long-term trend of global mean subduction rate might be attributed to the ocean dynamics,for example,the zonal velocity at the bottom mixed layer and zonal gradient of mixed layer depth.展开更多
During 1979–2015, the intensity of the Siberian high(SH) in November and December–January(DJ) is frequently shown to have an out-of-phase relationship, which is accompanied by opposite surface air temperature and ci...During 1979–2015, the intensity of the Siberian high(SH) in November and December–January(DJ) is frequently shown to have an out-of-phase relationship, which is accompanied by opposite surface air temperature and circulation anomalies.Further analyses indicate that the autumn Arctic sea ice is important for the phase reversal of the SH. There is a significantly positive(negative) correlation between the November(DJ) SH and the September sea ice area(SIA) anomalies. It is suggested that the reduction of autumn SIA induces anomalous upward surface turbulent heat flux(SHF), which can persist into November, especially over the Barents Sea. Consequently, the enhanced eddy energy and wave activity flux are transported to mid and high latitudes. This will then benefit the development of the storm track in northeastern Europe. Conversely, when downward SHF anomalies prevail in DJ, the decreased heat flux and suppressed eddy energy hinder the growth of the storm track during DJ over the Barents Sea and Europe. Through the eddy–mean flow interaction, the strengthened(weakened)storm track activities induce decreased(increased) Ural blockings and accelerated(decelerated) westerlies, which makes the cold air from the Arctic inhibited(transported) over the Siberian area. Therefore, a weaker(stronger) SH in November(DJ) occurs downstream. Moreover, anomalously large snowfall may intensify the SH in DJ rather than in November. The ensemble-mean results from the CMIP5 historical simulations further confirm these connections. The different responses to Arctic sea ice anomalies in early and middle winter set this study apart from earlier ones.展开更多
In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key r...In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes.Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east–west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific–Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.展开更多
Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution GCM.However, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine r...Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution GCM.However, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine resolution, close to that of an RCM, and, if so, which is the better approach, are open questions. These questions are important for understanding and using these two kinds of simulation approaches, but have not yet been investigated. Accordingly, the present reported work compared simulation results over China from a very-fine-resolution GCM(VFRGCM) and from RCM dynamical downscaling. The results showed that:(1) The VFRGCM reproduces the climatologies and trends of both air temperature and precipitation, as well as inter-monthly variations of air temperature in terms of spatial pattern and amount, closer to observations than the coarse-resolution version of the GCM. This is not the case, however, for the inter-monthly variations of precipitation.(2) The VFRGCM captures the climatology, trend, and inter-monthly variation of air temperature, as well as the trend in precipitation, more reasonably than the RCM dynamical downscaling method.(3) The RCM dynamical downscaling method performs better than the VFRGCM in terms of the climatology and inter-monthly variation of precipitation. Overall,the results suggest that VFRGCMs possess great potential with regard to their application in climate simulation in the future,and the RCM dynamical downscaling method is still dominant in terms of regional precipitation simulation.展开更多
The boreal spring Antarctic Oscillation(AAO) has a significant impact on the spring and summer climate in China. This study evaluates the capability of the NCEP's Climate Forecast System, version 2(CFSv2), in pred...The boreal spring Antarctic Oscillation(AAO) has a significant impact on the spring and summer climate in China. This study evaluates the capability of the NCEP's Climate Forecast System, version 2(CFSv2), in predicting the boreal spring AAO for the period 1983–2015. The results indicate that CFSv2 has poor skill in predicting the spring AAO, failing to predict the zonally symmetric spatial pattern of the AAO, with an insignificant correlation of 0.02 between the predicted and observed AAO Index(AAOI). Considering the interannual increment approach can amplify the prediction signals, we firstly establish a dynamical–statistical model to improve the interannual increment of the AAOI(DY AAOI), with two predictors of CFSv2-forecasted concurrent spring sea surface temperatures and observed preceding autumn sea ice. This dynamical–statistical model demonstrates good capability in predicting DY AAOI, with a significant correlation coefficient of 0.58 between the observation and prediction during 1983–2015 in the two-year-out cross-validation. Then, we obtain an improved AAOI by adding the improved DY AAOI to the preceding observed AAOI. The improved AAOI shows a significant correlation coefficient of 0.45 with the observed AAOI during 1983–2015. Moreover, the unrealistic atmospheric response to March–April–May sea ice in CFSv2 may be the possible cause for the failure of CFSv2 to predict the AAO. This study gives new clues regarding AAO prediction and short-term climate prediction.展开更多
Fine characterization of pore systems and heterogeneity of shale reservoirs are significant contents of shale gas reservoir physical property research. The research on micro-control factors of low productivity in the ...Fine characterization of pore systems and heterogeneity of shale reservoirs are significant contents of shale gas reservoir physical property research. The research on micro-control factors of low productivity in the Qiongzhusi Formation(Fm.) is still controversial. The lower Cambrian Qiongzhusi Fm. in the Qujing, Yunnan was taken as the object to investigate the influence of mineral compositions on the physical properties of the reservoir and the heterogeneity of shale, using the algorithm to improve the characterization ability of Atomic Force Microscopy(AFM). The results showed that:(1) The pores are mainly wedge-shaped pores and V-shaped pores. The pore diameter of the main pore segment ranges from 5 to 10 nm. Mesopores are mainly developed in the Qiongzhusi Fm. shale in Well QD1, with the average pore diameter of 6.08 nm.(2) Microscopic pore structure and shale surface properties show strong heterogeneity, which complicates the micro-migration of shale gas and increases the difficulty of identifying high-quality reservoirs.(3) The increase of clay mineral content intensifies the compaction and then destroys the pores. Conversely, brittle minerals can protect pores. The support and protection of brittle minerals to pores space depend on their content, mechanical properties and diagenesis.(4)Compression damage to pores, large microscopic roughness and surface fluctuations and strong pore structure heterogeneity are the reasons for the poor gas storage capacity of the Qiongzhusi Fm., which will lead to poor productivity in the Qiongzhusi Fm.展开更多
This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover.The results show that there is a significant negative correlation betwe...This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover.The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China.The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly.More(less)eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher(lower)than normal in the polar region and lower(higher)in the northern mid-high latitudes.Due to the persistence of the eastern Siberia snow from October to the following winter,the winter atmospheric anomaly is favorable(unfavorable)to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and,hence,lower(higher)temperature over Northeast China.Simultaneously,when the October snow cover is more(less),the SST in the northwestern Pacific is continuously lower(higher)as a whole; then,the Aleutian low and the East Asia trough are reinforced(weakened),favoring the lower(higher)temperature over Northeast China.展开更多
This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China(NEC) and their associated atmospheric circulation anomalies. It is shown that the first pri...This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China(NEC) and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC(referred to as the south mode), whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC(referred to as the north mode). Further findings reveal that, through modulating moisture transportation and upper-and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC's northern and western boundaries. Furthermore, the north(south) mode is strongly related to the intensity(meridional shift) of the East Asian westerly jet.展开更多
Climate change is one of the most challenging issues faced by human beings. Although many remarkable achievements have been made in climate change research,there is still a tremendous amount of uncertainty
This paper documents a decadal strengthened co-variability of the Antarctic Oscillation(AAO)and ENSO in austral spring after the mid-1990 s.During the period 1979–93,the ENSO(AAO)spatial signatures are restricted to ...This paper documents a decadal strengthened co-variability of the Antarctic Oscillation(AAO)and ENSO in austral spring after the mid-1990 s.During the period 1979–93,the ENSO(AAO)spatial signatures are restricted to the tropics–midlatitudes(Antarctic–midlatitudes)of the Southern Hemisphere(SH),with a weak connection between the two oscillations.Comparatively,after the mid-1990 s,the El Ni o-related atmospheric anomalies project on a negative AAO pattern with a barotropic structure in the mid–high latitudes of the SH.The expansion of El Ni o-related air temperature anomalies have a heightened impact on the meridional thermal structure of the SH,contributing to a weakened circumpolar westerly and strengthened subtropical jet.Meanwhile,the ENSO-related southern three-cell circulations expand poleward and then strongly couple the Antarctic and the tropics.Numerical simulation results suggest that the intensified connection between ENSO and SST in the South Pacific since the mid-1990 s is responsible for the strengthened AAO–ENSO relationship.展开更多
Precipitation over southeastern Lake Baikal features a significant decreasing trend in July and August over 1979–2018 and is closely related to blocking occurrence over central Siberia(45°–70°N,75°–1...Precipitation over southeastern Lake Baikal features a significant decreasing trend in July and August over 1979–2018 and is closely related to blocking occurrence over central Siberia(45°–70°N,75°–115°E).This study investigates the formation and maintenance of anticyclonic and cyclonic wave-breaking(AWB and CWB)blocking events and their climate impacts on precipitation in the southeastern Lake Baikal area.Both AWB and CWB blocking events are characterized by a cold trough deepening from the sub-Arctic region and a ridge amplifying toward its north over central Siberia,as well as an evident Rossby wave train over midlatitude Eurasia.For AWB blocking events,the ridge and trough pair tilts clockwise and the wave train exhibits a zonal distribution.In contrast,ridge and trough pair associated with CWB blocking events leans anticlockwise with larger-scale,meridional,and more anisotropic signatures.Moreover,the incoming Rossby wave energy associated with CWB blocking events is more evident than for AWB blocking events.Therefore,CWB blocking events are more persistent.AWB blocking events produce more extensive and persistent precipitation over the southeastern Lake Baikal area than CWB blocking events,in which moderate above-normal rainfall is seen in the decaying periods of blockings.A significant decreasing trend is found in terms of AWB blocking occurrence over central Siberia,which may contribute to the downward trend of precipitation over southeastern Lake Baikal.展开更多
Haze pollution in early winter(December and January) in the Yangtze River Delta(YRD) and in North China(NC)are both severe;however, their monthly variations are significantly different. In this study, the dominant lar...Haze pollution in early winter(December and January) in the Yangtze River Delta(YRD) and in North China(NC)are both severe;however, their monthly variations are significantly different. In this study, the dominant large-scale atmospheric circulations and local meteorological conditions were investigated and compared over the YRD and NC in each month. Results showed that the YRD(NC) is dominated by the so-called Scandinavia(East Atlantic/West Russia)pattern in December, and these circulations weaken in January. The East Asian December and January monsoons over the YRD and NC have negative correlations with the number of haze days. The local descending motion facilitates less removal of haze pollution over the YRD, while the local ascending motion facilitates less removal of haze pollution over NC in January, despite a weaker relationship in December. Additionally, the monthly variations of atmospheric circulations showed that adverse meteorological conditions restrict the vertical(horizontal) dispersion of haze pollution in December(January) over the YRD, while the associated local weather conditions are similar in these two months over NC.展开更多
基金The National Natural Science Foundation of China under contract No.41605052。
文摘An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a period of weak trends.The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage,the areas north to Victoria Land and Wilkes Land,and the central parts of the South Indian sector.The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector.The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.
基金This research is supported by the National Key R&D Program of China(Grant No.2022YFF0801604).
文摘The meridional gradient of surface air temperature associated with“Warm Arctic–Cold Eurasia”(GradTAE)is closely related to climate anomalies and weather extremes in the mid-low latitudes.However,the Climate Forecast System Version 2(CFSv2)shows poor capability for GradTAE prediction.Based on the year-to-year increment approach,analysis using a hybrid seasonal prediction model for GradTAE in winter(HMAE)is conducted with observed September sea ice over the Barents–Kara Sea,October sea surface temperature over the North Atlantic,September soil moisture in southern North America,and CFSv2 forecasted winter sea ice over the Baffin Bay,Davis Strait,and Labrador Sea.HMAE demonstrates good capability for predicting GradTAE with a significant correlation coefficient of 0.84,and the percentage of the same sign is 88%in cross-validation during 1983−2015.HMAE also maintains high accuracy and robustness during independent predictions of 2016−20.Meanwhile,HMAE can predict the GradTAE in 2021 well as an experiment of routine operation.Moreover,well-predicted GradTAE is useful in the prediction of the large-scale pattern of“Warm Arctic–Cold Eurasia”and has potential to enhance the skill of surface air temperature occurrences in the east of China.
基金the National Natural Science Foundation of China[Grants No.41991283]the Research Council of Norway Funded Project BASIC[Grant No.325440]Chinese-Norwegian Collaboration Projects Within Climate funded by the Research Council of Norway(COMBINED)[Grant No.328935].
基金the National Natural Science Foundation of China[grant number 42088101]the Postgraduate Research and Practice Innovation Program of Jiangsu Province[grant number KYCX22_1147].
基金the National Key Research and Development Program of China[grant number 2018YFA0606403]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA23090102]the National Natural Science Foundation of China[grant number 41822502].
基金The National Natural Science Foundation of China under contract Nos 42192561 and 41605052the National Key Research and Development Program of China under contract No.2020YFA0608804.
文摘Subduction process is a dynamical bridge for the exchanges of heat between the atmosphere and subsurface ocean water,which is regarded as a central proxy for the ocean climate studies.Given its key indicator in climate signals,it is of importance to examine the ability of a model to simulate the global subduction rate before investigating the climate dynamics.In this paper,we evaluated the ability of 21 climate models from Coupled Model Intercomparison Project Phase 6(CMIP6)in simulating the subduction rate.In general,the simulation ability of the models to the subduction climatology is better than that to the long-term variation trend.Based on the comprehensive analysis of climatology distribution and long-term trend of the subduction rate,GISS-E2-1-G performs better in reproducing the subduction rate climatology and IPSL-CM6A-LR can simulate positive long-term trend for both the global mean subduction rate and the lateral induction term in the Antarctic Circumpolar Current(ACC)region.However,it is still challenging to capture both the distribution characteristics of the subduction climatology and the long-term temporal trend for the 21 CMIP6 models.In addition,the model results demonstrate that,the ACC area is the major region contributing to the long-term trend of the global mean subduction rate.The analysis in this paper indicates that the poor simulation ability of reproducing the long-term trend of global mean subduction rate might be attributed to the ocean dynamics,for example,the zonal velocity at the bottom mixed layer and zonal gradient of mixed layer depth.
基金supported by the National Natural Science Foundation of China[grant number 42088101]the National Postdoctoral Program for Innovative Talent of China[grant number BX2021133]the China Postdoctoral Science Foundation of No.70 General Fund[grant number 2021M701753]。
基金supported by the National Key R&D Program of China (Grant No.2016YFA0600703)the National Natural Science Foundation of China (Grant Nos.41505073 and 41605059)+1 种基金the Research Council of Norway–supported project SNOWGLACE (Grant No.244166/E10)and the Young Talent Support Program of the China Association for Science and Technology (Grant No.2016QNRC001)
文摘During 1979–2015, the intensity of the Siberian high(SH) in November and December–January(DJ) is frequently shown to have an out-of-phase relationship, which is accompanied by opposite surface air temperature and circulation anomalies.Further analyses indicate that the autumn Arctic sea ice is important for the phase reversal of the SH. There is a significantly positive(negative) correlation between the November(DJ) SH and the September sea ice area(SIA) anomalies. It is suggested that the reduction of autumn SIA induces anomalous upward surface turbulent heat flux(SHF), which can persist into November, especially over the Barents Sea. Consequently, the enhanced eddy energy and wave activity flux are transported to mid and high latitudes. This will then benefit the development of the storm track in northeastern Europe. Conversely, when downward SHF anomalies prevail in DJ, the decreased heat flux and suppressed eddy energy hinder the growth of the storm track during DJ over the Barents Sea and Europe. Through the eddy–mean flow interaction, the strengthened(weakened)storm track activities induce decreased(increased) Ural blockings and accelerated(decelerated) westerlies, which makes the cold air from the Arctic inhibited(transported) over the Siberian area. Therefore, a weaker(stronger) SH in November(DJ) occurs downstream. Moreover, anomalously large snowfall may intensify the SH in DJ rather than in November. The ensemble-mean results from the CMIP5 historical simulations further confirm these connections. The different responses to Arctic sea ice anomalies in early and middle winter set this study apart from earlier ones.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0600703)the National Natural Science Foundation of China(Grant Nos.41605059,41505073 and 41375083)+1 种基金the Young Talent Support Program of the China Association for Science and Technology(Grant No.2016QNRC001)the Research Council of Norway SNOWGLACE(244166/E10)project
文摘In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes.Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east–west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific–Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.
基金jointly supported by the National Natural Science Foundation of China (Grant Nos. 41130103, 41421004 and 41405087)
文摘Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution GCM.However, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine resolution, close to that of an RCM, and, if so, which is the better approach, are open questions. These questions are important for understanding and using these two kinds of simulation approaches, but have not yet been investigated. Accordingly, the present reported work compared simulation results over China from a very-fine-resolution GCM(VFRGCM) and from RCM dynamical downscaling. The results showed that:(1) The VFRGCM reproduces the climatologies and trends of both air temperature and precipitation, as well as inter-monthly variations of air temperature in terms of spatial pattern and amount, closer to observations than the coarse-resolution version of the GCM. This is not the case, however, for the inter-monthly variations of precipitation.(2) The VFRGCM captures the climatology, trend, and inter-monthly variation of air temperature, as well as the trend in precipitation, more reasonably than the RCM dynamical downscaling method.(3) The RCM dynamical downscaling method performs better than the VFRGCM in terms of the climatology and inter-monthly variation of precipitation. Overall,the results suggest that VFRGCMs possess great potential with regard to their application in climate simulation in the future,and the RCM dynamical downscaling method is still dominant in terms of regional precipitation simulation.
基金supported by the National Key Research and Development Program of China (Grant No. 2016YFA0600703)the funding of the Jiangsu Innovation & Entrepreneurship Team and the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The boreal spring Antarctic Oscillation(AAO) has a significant impact on the spring and summer climate in China. This study evaluates the capability of the NCEP's Climate Forecast System, version 2(CFSv2), in predicting the boreal spring AAO for the period 1983–2015. The results indicate that CFSv2 has poor skill in predicting the spring AAO, failing to predict the zonally symmetric spatial pattern of the AAO, with an insignificant correlation of 0.02 between the predicted and observed AAO Index(AAOI). Considering the interannual increment approach can amplify the prediction signals, we firstly establish a dynamical–statistical model to improve the interannual increment of the AAOI(DY AAOI), with two predictors of CFSv2-forecasted concurrent spring sea surface temperatures and observed preceding autumn sea ice. This dynamical–statistical model demonstrates good capability in predicting DY AAOI, with a significant correlation coefficient of 0.58 between the observation and prediction during 1983–2015 in the two-year-out cross-validation. Then, we obtain an improved AAOI by adding the improved DY AAOI to the preceding observed AAOI. The improved AAOI shows a significant correlation coefficient of 0.45 with the observed AAOI during 1983–2015. Moreover, the unrealistic atmospheric response to March–April–May sea ice in CFSv2 may be the possible cause for the failure of CFSv2 to predict the AAO. This study gives new clues regarding AAO prediction and short-term climate prediction.
基金This work was supported by the National Key R&D Program of China(No.2020YFA 0711800)the National Natural Science Foundation of China(No.41772141,41972171)+1 种基金the Natural Science Foundation of Jiangsu Province(BK20181362)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Fine characterization of pore systems and heterogeneity of shale reservoirs are significant contents of shale gas reservoir physical property research. The research on micro-control factors of low productivity in the Qiongzhusi Formation(Fm.) is still controversial. The lower Cambrian Qiongzhusi Fm. in the Qujing, Yunnan was taken as the object to investigate the influence of mineral compositions on the physical properties of the reservoir and the heterogeneity of shale, using the algorithm to improve the characterization ability of Atomic Force Microscopy(AFM). The results showed that:(1) The pores are mainly wedge-shaped pores and V-shaped pores. The pore diameter of the main pore segment ranges from 5 to 10 nm. Mesopores are mainly developed in the Qiongzhusi Fm. shale in Well QD1, with the average pore diameter of 6.08 nm.(2) Microscopic pore structure and shale surface properties show strong heterogeneity, which complicates the micro-migration of shale gas and increases the difficulty of identifying high-quality reservoirs.(3) The increase of clay mineral content intensifies the compaction and then destroys the pores. Conversely, brittle minerals can protect pores. The support and protection of brittle minerals to pores space depend on their content, mechanical properties and diagenesis.(4)Compression damage to pores, large microscopic roughness and surface fluctuations and strong pore structure heterogeneity are the reasons for the poor gas storage capacity of the Qiongzhusi Fm., which will lead to poor productivity in the Qiongzhusi Fm.
基金supported by the National Natural Science Foundation of China(Grant Nos.41130103 and 41210007)the National Basic Research Program of China(Grant No.2009CB421406)the CAS–CSIRO Cooperative Research Program(Grant No.GJHZ1223)
文摘This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover.The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China.The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly.More(less)eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher(lower)than normal in the polar region and lower(higher)in the northern mid-high latitudes.Due to the persistence of the eastern Siberia snow from October to the following winter,the winter atmospheric anomaly is favorable(unfavorable)to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and,hence,lower(higher)temperature over Northeast China.Simultaneously,when the October snow cover is more(less),the SST in the northwestern Pacific is continuously lower(higher)as a whole; then,the Aleutian low and the East Asia trough are reinforced(weakened),favoring the lower(higher)temperature over Northeast China.
基金supported by the National Key Research and Development Program of China (Grant No.2016YFA0600703)the National Natural Science Foundation of China (Grant No.41805046)+2 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No.18KJB170013)the Startup Foundation for Introducing Talent of NUIST (Grant No.2243141701085)the funding of the Jiangsu Innovation and Entrepreneurship Team
文摘This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China(NEC) and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC(referred to as the south mode), whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC(referred to as the north mode). Further findings reveal that, through modulating moisture transportation and upper-and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC's northern and western boundaries. Furthermore, the north(south) mode is strongly related to the intensity(meridional shift) of the East Asian westerly jet.
文摘Climate change is one of the most challenging issues faced by human beings. Although many remarkable achievements have been made in climate change research,there is still a tremendous amount of uncertainty
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.41421004 and 41210007)the Special Fund for Public Welfare Industry(Meteorology)(Grant No.GYHY201306026)
文摘This paper documents a decadal strengthened co-variability of the Antarctic Oscillation(AAO)and ENSO in austral spring after the mid-1990 s.During the period 1979–93,the ENSO(AAO)spatial signatures are restricted to the tropics–midlatitudes(Antarctic–midlatitudes)of the Southern Hemisphere(SH),with a weak connection between the two oscillations.Comparatively,after the mid-1990 s,the El Ni o-related atmospheric anomalies project on a negative AAO pattern with a barotropic structure in the mid–high latitudes of the SH.The expansion of El Ni o-related air temperature anomalies have a heightened impact on the meridional thermal structure of the SH,contributing to a weakened circumpolar westerly and strengthened subtropical jet.Meanwhile,the ENSO-related southern three-cell circulations expand poleward and then strongly couple the Antarctic and the tropics.Numerical simulation results suggest that the intensified connection between ENSO and SST in the South Pacific since the mid-1990 s is responsible for the strengthened AAO–ENSO relationship.
基金supported by the National Science and Technology Support Program of China (Grant No. 2015BAC03B03)the National Natural Science Foundation of China (Grant Nos. 41861144014, 41630424 and 41875078)
文摘Precipitation over southeastern Lake Baikal features a significant decreasing trend in July and August over 1979–2018 and is closely related to blocking occurrence over central Siberia(45°–70°N,75°–115°E).This study investigates the formation and maintenance of anticyclonic and cyclonic wave-breaking(AWB and CWB)blocking events and their climate impacts on precipitation in the southeastern Lake Baikal area.Both AWB and CWB blocking events are characterized by a cold trough deepening from the sub-Arctic region and a ridge amplifying toward its north over central Siberia,as well as an evident Rossby wave train over midlatitude Eurasia.For AWB blocking events,the ridge and trough pair tilts clockwise and the wave train exhibits a zonal distribution.In contrast,ridge and trough pair associated with CWB blocking events leans anticlockwise with larger-scale,meridional,and more anisotropic signatures.Moreover,the incoming Rossby wave energy associated with CWB blocking events is more evident than for AWB blocking events.Therefore,CWB blocking events are more persistent.AWB blocking events produce more extensive and persistent precipitation over the southeastern Lake Baikal area than CWB blocking events,in which moderate above-normal rainfall is seen in the decaying periods of blockings.A significant decreasing trend is found in terms of AWB blocking occurrence over central Siberia,which may contribute to the downward trend of precipitation over southeastern Lake Baikal.
基金supported by the National Natural Science Foundation of China [grant number 42088101]the Major Program of the National Natural Science Foundation of China [grant number 41991283]。
基金supported by the National Key Research and Development Plan (Grant No. 2016YFA0600703)the National Natural Science Foundation of China (Grant Nos. 91744311, 41991283 and 41705058)the funding of the Jiangsu Innovation & Entrepreneurship Team。
文摘Haze pollution in early winter(December and January) in the Yangtze River Delta(YRD) and in North China(NC)are both severe;however, their monthly variations are significantly different. In this study, the dominant large-scale atmospheric circulations and local meteorological conditions were investigated and compared over the YRD and NC in each month. Results showed that the YRD(NC) is dominated by the so-called Scandinavia(East Atlantic/West Russia)pattern in December, and these circulations weaken in January. The East Asian December and January monsoons over the YRD and NC have negative correlations with the number of haze days. The local descending motion facilitates less removal of haze pollution over the YRD, while the local ascending motion facilitates less removal of haze pollution over NC in January, despite a weaker relationship in December. Additionally, the monthly variations of atmospheric circulations showed that adverse meteorological conditions restrict the vertical(horizontal) dispersion of haze pollution in December(January) over the YRD, while the associated local weather conditions are similar in these two months over NC.
