In this study,two possible persistent anomalies of the Madden-Julian Oscillation mode(MJO) are found in the summer season(persistently Pacific active and Indian Ocean active),and an index is set to define the intensit...In this study,two possible persistent anomalies of the Madden-Julian Oscillation mode(MJO) are found in the summer season(persistently Pacific active and Indian Ocean active),and an index is set to define the intensity of the two modes.They are proved to have high statistical correlations to the later ENSO events in the autumn and winter seasons:When persistent anomaly of MJO happens in the Pacific Ocean in summer,El Nino events are often induced during the autumn and winter seasons of that year.However,during the other MJO mode when the summer persistent anomaly of MJO occurs in the Indian Ocean,La Nina events often follow instead.The analysis of the atmospheric circulation field indicates that persistent anomaly of MJO can probably affect the entire Equatorial Pacific circulation,and results in wind stress anomalies.The wind stress anomalies could excite warm or cold water masses which propagate eastwards at the subsurface ocean.The accumulation of warm or cold subsurface water in the Equatorial Eastern Pacific Ocean may eventually lead to the formation of an ENSO.展开更多
Within the frame of the Zebiak-Cane model,the impact of the uncertainties of the Madden-Julian Oscillation(MJO) on ENSO predictability was studied using a parameterized stochastic representation of intraseasonal for...Within the frame of the Zebiak-Cane model,the impact of the uncertainties of the Madden-Julian Oscillation(MJO) on ENSO predictability was studied using a parameterized stochastic representation of intraseasonal forcing.The results show that the uncertainties of MJO have little effect on the maximum prediction error for ENSO events caused by conditional nonlinear optimal perturbation(CNOP);compared to CNOP-type initial error,the model error caused by the uncertainties of MJO led to a smaller prediction uncertainty of ENSO,and its influence over the ENSO predictability was not significant.This result suggests that the initial error might be the main error source that produces uncertainty in ENSO prediction,which could provide a theoretical foundation for the data assimilation of the ENSO forecast.展开更多
In this paper, the influence of El Ni?o event on the Madden-Julian Oscillation(MJO) over the equatorial Pacific is studied by using reanalysis data and relevant numerical simulation results. It is clearly shown that E...In this paper, the influence of El Ni?o event on the Madden-Julian Oscillation(MJO) over the equatorial Pacific is studied by using reanalysis data and relevant numerical simulation results. It is clearly shown that El Ni?o can reduce the intensity of MJO. The kinetic energy of MJO over the equatorial Pacific is stronger before the occurrence of the El Ni?o event, but it is reduced rapidly after El Ni?o event outbreak, and the weakened MJO even can continue to the next summer. The convection over the central-western Pacific is weakened in El Ni?o winter. The positive anomalous OLR over the central-western Pacific has opposite variation in El Ni?o winter comparing to the non-ENSO cases. The vertical structure of MJO also affected by El Ni?o event, so the opposite direction features of the geopotential height and the zonal wind in upper and lower level troposphere for the MJO are not remarkable in the El Ni?o winter and tend to be barotropic features. El Ni?o event also has an influence on the eastward propa- gation of the MJO too. During El Ni?o winter, the eastward propagation of the MJO is not so regular and unanimous and there exists some eastward propagation, which is faster than that in non-ENSO case. Dynamic analyses suggest that positive SSTA(El Ni?o case) affects the atmospheric thickness over the equatorial Pacific and then the excited atmospheric wave-CISK mode is weakened, so that the intensity of MJO is reduced; the combining of the barotropic unstable mode in the atmosphere excited by external forcing(SSTA) and the original MJO may be an important reason for the MJO vertical structure tending to be barotropic during the El Ni?o.展开更多
This study investigates the potential influences of anthropogenic forcings and natural variability on the risk of summer extreme temperatures over China. We use three multi-thousand-member ensemble simulations with di...This study investigates the potential influences of anthropogenic forcings and natural variability on the risk of summer extreme temperatures over China. We use three multi-thousand-member ensemble simulations with different forcings (with or without anthropogenic greenhouse gases and aerosol emissions) to evaluate the human impact, and with sea surface temperature patterns from three different years around the E1 Nino-Southern Oscillation (ENSO) 2015/16 event (years 2014, 2015 and 2016) to evaluate the impact of natural variability. A generalized extreme value (GEV) distribution is used to fit the ensemble results. Based on these model results, we find that, during the peak of ENSO (2015), daytime extreme tem- peratures axe smaller over the central China region compared to a normal year (2014). During 2016, the risk of nighttime extreme temperatures is largely increased over the eastern coastal region. Both anomalies are of the same magnitude as the anthropogenic influence. Thus, ENSO can amplify or counterbalance (at a regional and annual scale) anthropogenic effects on extreme summer temperatures over China. Changes are mainly due to changes in the GEV location parameter. Thus, anomalies are due to a shift in the distributions and not to a change in temperature variability.展开更多
This paper investigates the contrasts between strong and weak Madden-Julian Oscillation(MJO) activity over the equatorial western Pacific during winter using the NCEP reanalysis data. It is shown that the MJO over the...This paper investigates the contrasts between strong and weak Madden-Julian Oscillation(MJO) activity over the equatorial western Pacific during winter using the NCEP reanalysis data. It is shown that the MJO over the equatorial western Pacific in winter shows significant interannual and interdecadal variabilities. During the winters with strong MJO activity, an anomalous cyclonic circulation lies east of the Philippines, strong anomalous easterlies control the equatorial eastern Pacific, and anomalous westerlies extend from the Indian Ocean to the western Pacific in the lower troposphere, which strengthens the convergence and convection over the equatorial western Pacific. The moisture convergence in the lower troposphere is also enhanced over the western Pacific, which is favorable to the activity of MJO. Eastward propagation is a significant feature of the MJO, though there is some westward propagation. The space-time spectral power and center period of the MJO are higher during strong MJO activity winters. The anomalous activity of MJO is closely related to the sea surface temperature(SST) and East Asian winter monsoon(EAWM).During strong MJO activity winters, there are positive/negative anomalies at high/low latitudes in both sea level pressure and 500 h Pa geopotential height, and the temperature is lower over the central part of the Chinese mainland, which indicates a strong EAWM. China experiences more rainfall between the Yellow and Yangtze Rivers, but less rainfall south of the Yangtze River. The SSTA is negative near the Taiwan Island due to the impact of strong EAWM and shows a La Nina pattern anomaly over the eastern Pacific. During the weak MJO activity winters, the situation is reversed.展开更多
The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convecti...The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convective branches shifted south of the equator over the MC during eastern Pacific(EP)El Nino winters,while it became relatively symmetric about the equator during La Ni?a winters.The impact of central Pacific(CP)El Ninos to MJO pattern,on the other hand,is not statistically significant.The cause of the distinctive MJO pattern evolutions is likely attributed to the ENSO-induced changes of the background moisture and vertical shear over the MC.Idealized numerical experiments with a 2.5-layer model were carried out,and the result revealed that the background moisture change played a dominant role.An observational diagnosis of column-integrated moist static energy(MSE)budgets was further conducted.The result indicated that the MJO pattern difference was attributed to the MSE tendency asymmetry in front of MJO convection between EP El Nino and La Ni?a,caused by the advection of the mean MSE by anomalous meridional wind.The difference in the MJO-scale anomalous meridional wind was ultimately controlled by the change of the background meridional moisture gradient associated with EP El Nino and La Ni?a.展开更多
利用忻州各县(市、区)42 a 7-8月的降水数据和23 a的玉米产量数据,分析了极端降水对玉米气候产量的影响。结果表明:在1981-2022年期间,忻州及其各县(市、区)7-8月的极端降水指数均呈上升的变化趋势,上升速率由西部向东部逐渐增加;玉米...利用忻州各县(市、区)42 a 7-8月的降水数据和23 a的玉米产量数据,分析了极端降水对玉米气候产量的影响。结果表明:在1981-2022年期间,忻州及其各县(市、区)7-8月的极端降水指数均呈上升的变化趋势,上升速率由西部向东部逐渐增加;玉米实际单产及趋势产量均呈显著的上升趋势;玉米气候产量与极端降水指数呈正相关,两者间的相关系数在海拔较高地区明显大于平川地区;正极端降水事件发生在拉尼娜结束年的概率明显高于开始年,负极端降水事件发生在厄尔尼诺开始年(或持续年)的概率明显高于结束年;正、负极端降水事件一般与玉米气候产量的丰、歉相对应;因ENSO而发生的极端降水事件使得忻州的玉米气候产量平均下降了15.3 kg/hm^(2),下降幅度近7%。展开更多
由大气科学和地球流体力学数值模拟国家重点实验室(LASG)和中科院大气物理研究所(IAP)主办的国际热带大气季节内振荡(MJO)专题讨论会于2016年8月6—9日在成都召开,来自美国、加拿大、日本、韩国、欧洲中心等9个国家和地区高校和...由大气科学和地球流体力学数值模拟国家重点实验室(LASG)和中科院大气物理研究所(IAP)主办的国际热带大气季节内振荡(MJO)专题讨论会于2016年8月6—9日在成都召开,来自美国、加拿大、日本、韩国、欧洲中心等9个国家和地区高校和气象机构的124名学者参加了会议。结合2017—2019年"海洋大陆年(Years of the Maritime Continent,YMC)"增强对印度洋到太平洋之间海洋大陆的观测和模拟的倡议.展开更多
基金National Natural Science Foundation of China(41375059)National Public Welfare(Meteorological Sector)Special Project of China(GYHY201306022)
文摘In this study,two possible persistent anomalies of the Madden-Julian Oscillation mode(MJO) are found in the summer season(persistently Pacific active and Indian Ocean active),and an index is set to define the intensity of the two modes.They are proved to have high statistical correlations to the later ENSO events in the autumn and winter seasons:When persistent anomaly of MJO happens in the Pacific Ocean in summer,El Nino events are often induced during the autumn and winter seasons of that year.However,during the other MJO mode when the summer persistent anomaly of MJO occurs in the Indian Ocean,La Nina events often follow instead.The analysis of the atmospheric circulation field indicates that persistent anomaly of MJO can probably affect the entire Equatorial Pacific circulation,and results in wind stress anomalies.The wind stress anomalies could excite warm or cold water masses which propagate eastwards at the subsurface ocean.The accumulation of warm or cold subsurface water in the Equatorial Eastern Pacific Ocean may eventually lead to the formation of an ENSO.
基金supported by the National Natural Science Foundation of China [grant number 41420104002]the China National 973 Project [grant number 2015CB453200]+2 种基金the Public Science and Technology Research Funds Projects of the Ocean[grant number 201505013]the Natural Science Foundation of Jiangsu Province [grant numbers BK20150907 and 14KJA170002]the National Science Foundation of the US [grant number AGS-1540783]
基金sponsored by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No. KZCX2-YW-QN203)the National Basic Research Program of China (Grant Nos. 2012CB955202 and 2010CB950402)the National Natural Science Foundation of China (Grant No. 40821092)
文摘Within the frame of the Zebiak-Cane model,the impact of the uncertainties of the Madden-Julian Oscillation(MJO) on ENSO predictability was studied using a parameterized stochastic representation of intraseasonal forcing.The results show that the uncertainties of MJO have little effect on the maximum prediction error for ENSO events caused by conditional nonlinear optimal perturbation(CNOP);compared to CNOP-type initial error,the model error caused by the uncertainties of MJO led to a smaller prediction uncertainty of ENSO,and its influence over the ENSO predictability was not significant.This result suggests that the initial error might be the main error source that produces uncertainty in ENSO prediction,which could provide a theoretical foundation for the data assimilation of the ENSO forecast.
基金supported by the National ‘973’ Programme (No. 2013CB956203)the National Natural Science Foundation of China (No. 41275086)
文摘In this paper, the influence of El Ni?o event on the Madden-Julian Oscillation(MJO) over the equatorial Pacific is studied by using reanalysis data and relevant numerical simulation results. It is clearly shown that El Ni?o can reduce the intensity of MJO. The kinetic energy of MJO over the equatorial Pacific is stronger before the occurrence of the El Ni?o event, but it is reduced rapidly after El Ni?o event outbreak, and the weakened MJO even can continue to the next summer. The convection over the central-western Pacific is weakened in El Ni?o winter. The positive anomalous OLR over the central-western Pacific has opposite variation in El Ni?o winter comparing to the non-ENSO cases. The vertical structure of MJO also affected by El Ni?o event, so the opposite direction features of the geopotential height and the zonal wind in upper and lower level troposphere for the MJO are not remarkable in the El Ni?o winter and tend to be barotropic features. El Ni?o event also has an influence on the eastward propa- gation of the MJO too. During El Ni?o winter, the eastward propagation of the MJO is not so regular and unanimous and there exists some eastward propagation, which is faster than that in non-ENSO case. Dynamic analyses suggest that positive SSTA(El Ni?o case) affects the atmospheric thickness over the equatorial Pacific and then the excited atmospheric wave-CISK mode is weakened, so that the intensity of MJO is reduced; the combining of the barotropic unstable mode in the atmosphere excited by external forcing(SSTA) and the original MJO may be an important reason for the MJO vertical structure tending to be barotropic during the El Ni?o.
基金supported by the UK-China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP) China as part of the Newton Fund
文摘This study investigates the potential influences of anthropogenic forcings and natural variability on the risk of summer extreme temperatures over China. We use three multi-thousand-member ensemble simulations with different forcings (with or without anthropogenic greenhouse gases and aerosol emissions) to evaluate the human impact, and with sea surface temperature patterns from three different years around the E1 Nino-Southern Oscillation (ENSO) 2015/16 event (years 2014, 2015 and 2016) to evaluate the impact of natural variability. A generalized extreme value (GEV) distribution is used to fit the ensemble results. Based on these model results, we find that, during the peak of ENSO (2015), daytime extreme tem- peratures axe smaller over the central China region compared to a normal year (2014). During 2016, the risk of nighttime extreme temperatures is largely increased over the eastern coastal region. Both anomalies are of the same magnitude as the anthropogenic influence. Thus, ENSO can amplify or counterbalance (at a regional and annual scale) anthropogenic effects on extreme summer temperatures over China. Changes are mainly due to changes in the GEV location parameter. Thus, anomalies are due to a shift in the distributions and not to a change in temperature variability.
基金National Basic Research Program of China(2015CB453200,2013CB956200)National Nature Science Foundation of China(41275086,41475070,41575062)
文摘This paper investigates the contrasts between strong and weak Madden-Julian Oscillation(MJO) activity over the equatorial western Pacific during winter using the NCEP reanalysis data. It is shown that the MJO over the equatorial western Pacific in winter shows significant interannual and interdecadal variabilities. During the winters with strong MJO activity, an anomalous cyclonic circulation lies east of the Philippines, strong anomalous easterlies control the equatorial eastern Pacific, and anomalous westerlies extend from the Indian Ocean to the western Pacific in the lower troposphere, which strengthens the convergence and convection over the equatorial western Pacific. The moisture convergence in the lower troposphere is also enhanced over the western Pacific, which is favorable to the activity of MJO. Eastward propagation is a significant feature of the MJO, though there is some westward propagation. The space-time spectral power and center period of the MJO are higher during strong MJO activity winters. The anomalous activity of MJO is closely related to the sea surface temperature(SST) and East Asian winter monsoon(EAWM).During strong MJO activity winters, there are positive/negative anomalies at high/low latitudes in both sea level pressure and 500 h Pa geopotential height, and the temperature is lower over the central part of the Chinese mainland, which indicates a strong EAWM. China experiences more rainfall between the Yellow and Yangtze Rivers, but less rainfall south of the Yangtze River. The SSTA is negative near the Taiwan Island due to the impact of strong EAWM and shows a La Nina pattern anomaly over the eastern Pacific. During the weak MJO activity winters, the situation is reversed.
基金Supported by the National Natural Science Foundation of China(42088101 and 41875069)US National Science Foundation(AGS-2006553)+2 种基金US NOAA Grant(NA18OAR4310298)SOEST contribution number 11206IPRC contribution number 1494。
文摘The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convective branches shifted south of the equator over the MC during eastern Pacific(EP)El Nino winters,while it became relatively symmetric about the equator during La Ni?a winters.The impact of central Pacific(CP)El Ninos to MJO pattern,on the other hand,is not statistically significant.The cause of the distinctive MJO pattern evolutions is likely attributed to the ENSO-induced changes of the background moisture and vertical shear over the MC.Idealized numerical experiments with a 2.5-layer model were carried out,and the result revealed that the background moisture change played a dominant role.An observational diagnosis of column-integrated moist static energy(MSE)budgets was further conducted.The result indicated that the MJO pattern difference was attributed to the MSE tendency asymmetry in front of MJO convection between EP El Nino and La Ni?a,caused by the advection of the mean MSE by anomalous meridional wind.The difference in the MJO-scale anomalous meridional wind was ultimately controlled by the change of the background meridional moisture gradient associated with EP El Nino and La Ni?a.
文摘利用忻州各县(市、区)42 a 7-8月的降水数据和23 a的玉米产量数据,分析了极端降水对玉米气候产量的影响。结果表明:在1981-2022年期间,忻州及其各县(市、区)7-8月的极端降水指数均呈上升的变化趋势,上升速率由西部向东部逐渐增加;玉米实际单产及趋势产量均呈显著的上升趋势;玉米气候产量与极端降水指数呈正相关,两者间的相关系数在海拔较高地区明显大于平川地区;正极端降水事件发生在拉尼娜结束年的概率明显高于开始年,负极端降水事件发生在厄尔尼诺开始年(或持续年)的概率明显高于结束年;正、负极端降水事件一般与玉米气候产量的丰、歉相对应;因ENSO而发生的极端降水事件使得忻州的玉米气候产量平均下降了15.3 kg/hm^(2),下降幅度近7%。
文摘利用1948—2011年NCEP等再分析资料,采用合成分析等方法对比分析了冬季(冬半年)热带西太平洋MJO(Madden-Julian Oscillation)活动强、弱年的环境场特征。结果表明,冬季热带西太平洋MJO的活动具有显著的年际和年代际变化。MJO活动强年,对流层低层在菲律宾以东洋面上空有异常气旋式环流,赤道东太平洋上空为较强的东风距平,赤道印度洋到赤道西太平洋上空是异常西风,西太平洋地区有较强辐合,从而导致热带西太平洋地区积云对流活动显著加强;而MJO活动弱年的环流特征相反。热带MJO以东传为主,有少量西传波动。在MJO活动强年,无论东传还是西传其时空谱值都显著大于MJO活动弱年,其中心频率较MJO活动弱年偏高。MJO活动的异常和海温及东亚冬季风紧密相连,在MJO活动强年,海平面气压和500 h Pa位势高度异常场表现为中高纬度的正异常和低纬地区的负异常,东亚冬季风活动偏强,中国大陆中部气温普遍偏低,同时,黄河以南长江以北地区降水偏多,而长江以南地区降水偏少;台湾附近海域受强东亚冬季风影响,海表温度偏低,东太平洋上海温距平呈现La Nia型的异常分布,而在MJO活动弱年上述特征基本相反。
文摘由大气科学和地球流体力学数值模拟国家重点实验室(LASG)和中科院大气物理研究所(IAP)主办的国际热带大气季节内振荡(MJO)专题讨论会于2016年8月6—9日在成都召开,来自美国、加拿大、日本、韩国、欧洲中心等9个国家和地区高校和气象机构的124名学者参加了会议。结合2017—2019年"海洋大陆年(Years of the Maritime Continent,YMC)"增强对印度洋到太平洋之间海洋大陆的观测和模拟的倡议.