The Madden-Julian Oscillation is one of the large-scale climate change patterns in the maritime tropics,with sub-seasonal time periods of 30 to 60 days affecting tropical and subtropical regions.This phenomenon can ca...The Madden-Julian Oscillation is one of the large-scale climate change patterns in the maritime tropics,with sub-seasonal time periods of 30 to 60 days affecting tropical and subtropical regions.This phenomenon can cause changes in various quantities of the atmosphere and ocean,such as pressure,sea surface temperature,and the rate of evaporation from the ocean surface in tropical regions.In this research,the effects of Madden-Julian fluctuation on the weather elements of Iran have been investigated with the aim of knowing the effects of different phases in order to improve the quality of forecasts and benefits in territorial planning.At first,the daily rainfall data of 1980-2020 were received from the National Meteorological Organization and quality controlled.Using the Wheeler and Hendon method,the two main components RMM1 and RMM2 were analyzed,based on which the amplitude of the above two components is considered as the main indicator of the intensity and weakness of this fluctuation.This index is based on the experimental orthogonal functions of the meteorological fields,including the average wind levels of 850 and 200 hectopascals and outgoing long wave radiation(OLR)between the latitudes of 20 degrees south and 20 degrees north.The clustering of the 7-day sequence with a component above 1 was used as the basis for clustering all eight phases,and by calculating the abnormality of each phase compared to its long term in the DJF time frame,the zoning of each phase was produced separately.In the end,phases 1,2,7,8 were concluded as effective phases in Iran’s rainfall and phases 3,4,5,6 as suppressive phases of Iran’s rainfall.展开更多
In the past decade there has been extensive research into tropical intraseasonal variability, one of the major components of the low frequency variability of the general atmospheric circulation. This paper briefly rev...In the past decade there has been extensive research into tropical intraseasonal variability, one of the major components of the low frequency variability of the general atmospheric circulation. This paper briefly reviews the state-of-the-art in this research area: the nature of the Madden-Julian Oscillation, its relation to monsoonal and extratropical circulations, and the current theoretical understandings.展开更多
2023年春季,我国西南地区发生了严重的气象干旱,对当地社会经济造成严重影响。为深入认识这次干旱事件的成因、并为未来西南地区春旱的预测提供科学依据,本文利用站点观测数据、美国国家环境预测中心和国家大气研究中心(National Center...2023年春季,我国西南地区发生了严重的气象干旱,对当地社会经济造成严重影响。为深入认识这次干旱事件的成因、并为未来西南地区春旱的预测提供科学依据,本文利用站点观测数据、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)再分析数据、美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)的海表温度等,采用T-N波作用通量和合成分析等方法,从海温和热带大气季节内振荡(Madden-Julian Oscillation,MJO)的角度深入探讨此次春旱成因。结果表明:(1)2023年我国西南春旱是高温干旱复合事件,3月干旱发生在中部,4月干旱加剧并向西扩展,5月干旱持续。(2)3月北太平洋的马蹄形海温异常导致西风急流偏南偏西,抑制了西南地区的降水。(3)4月印度洋暖海温通过Kelvin波导致孟加拉湾附近的反气旋式环流异常,西北太平洋暖海温通过Rossby波导致南海至菲律宾的气旋式环流异常,造成西南地区南部出现偏北风,导致水汽辐散,加剧干旱。(4)5月MJO长时间维持在西太平洋,通过Gill响应引发南海至菲律宾对流层低层的气旋异常,减少偏南水汽的输送,从而使得西南干旱持续。展开更多
This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from ...This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.展开更多
The authors examined the Madden-Julian Oscillation(MJO) in stratospheric ozone during boreal winter using a simulation from the Specified Dynamics version of the Whole Atmosphere Community Climate Model(SD-WACCM) in 2...The authors examined the Madden-Julian Oscillation(MJO) in stratospheric ozone during boreal winter using a simulation from the Specified Dynamics version of the Whole Atmosphere Community Climate Model(SD-WACCM) in 2004 and 2010. Comparison with European Centre for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim) data suggested that the model simulation represented well the three-dimensional structure of the MJO-related ozone anomalies in the upper troposphere and stratosphere(i.e., between 200 and 20 h Pa). The negative ozone anomalies were over the Tibetan Plateau and East Asia in MJO phases 3–7, when the MJO convective anomalies travelled from the equatorial Indian Ocean towards the equatorial western Pacific Ocean. Due to the different vertical structures of the MJO-related circulation anomalies, the MJO-related stratospheric ozone anomalies showed different vertical structure over the Tibetan Plateau(25–40°N, 75–105°E) and East Asia(25–40°N, 105–135°E). As a result of the positive bias in the model-calculated ozone in the upper troposphere and lower stratosphere, the amplitude of MJO-related stratospheric ozone column anomalies(10–16 Dobson Units(DU)) in the SD-WACCM simulation was slightly larger than that(8–14 DU) in the ERA-Interim reanalysis.展开更多
We investigate the Madden-Julian Oscillation （MJO） signal in wintertime stratospheric ozone over the Tibetan Plateau and East Asia using the harmonized dataset of satellite ozone profiles. Two different MJO indices ...We investigate the Madden-Julian Oscillation （MJO） signal in wintertime stratospheric ozone over the Tibetan Plateau and East Asia using the harmonized dataset of satellite ozone profiles. Two different MJO indices -- the all-season Real-Time multivariate MJO index （RMM） and outgoing longwave radiation-based MJO index （OMI） -- are used to compare the MJO- related ozone anomalies. The results show that there are pronounced eastward-propagating MJO-related stratospheric ozone anomalies （mainly within 20-200 hPa） over the subtropics, The negative stratospheric ozone anomalies are over the Tibetan Plateau and East Asia in MJO phases 4-7, when MJO-related tropical deep convective anomalies move from the equatorial Indian Ocean towards the western Pacific Ocean. Compared with the results based on RMM, the MJO-related stratospheric column ozone anomalies based on OM1 are stronger and one phase ahead. Further analysis suggests that different sampling errors, observation principles and retrieval algorithms may be responsible for the discrepancies among different satellite measurements. The MJO-related stratospheric ozone anomalies can be attributed to the MJO-related circulation anomalies, i.e., the uplifted tropopanse and the northward shifted westerly jet in the upper troposphere. Compared to the result based on RMM, the upper tropospheric westerly jet may play a less important role in generating the stratospheric column ozone anomalies based on OMI. Our study indicates that the circulation-based MJO index （RMM） can better characterize the MJO- related anomalies in tropopause pressure and thus the MJO influence on atmospheric trace gases in the upper troposphere and lower stratosphere, especially over subtropical East Asia.展开更多
This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of th...This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation(MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model's mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.展开更多
As one of the participants in the Subseasonal to Seasonal(S2S)Prediction Project,the China Meteorological Administration(CMA)has adopted several model versions to participate in the S2S Project.This study evaluates th...As one of the participants in the Subseasonal to Seasonal(S2S)Prediction Project,the China Meteorological Administration(CMA)has adopted several model versions to participate in the S2S Project.This study evaluates the models’capability to simulate and predict the Madden-Julian Oscillation(MJO).Three versions of the Beijing Climate Center Climate System Model(BCC-CSM)are used to conduct historical simulations and re-forecast experiments(referred to as EXP1,EXP1-M,and EXP2,respectively).In simulating MJO characteristics,the newly-developed high-resolution BCC-CSM outperforms its predecessors.In terms of MJO prediction,the useful prediction skill of the MJO index is enhanced from 15 days in EXP1 to 22 days in EXP1-M,and further to 24 days in EXP2.Within the first forecast week,the better initial condition in EXP2 largely contributes to the enhancement of MJO prediction skill.However,during forecast weeks 2–3,EXP2 shows little advantage compared with EXP1-M because the increased skill at MJO initial phases 6–7 is largely offset by the degraded skill at MJO initial phases 2–3.Particularly at initial phases 2–3,EXP1-M skillfully captures the wind field and Kelvin-wave response to MJO convection,leading to the highest prediction skill of the MJO.Our results reveal that,during the participation of the CMA models in the S2S Project,both the improved model initialization and updated model physics played positive roles in improving MJO prediction.Future efforts should focus on improving the model physics to better simulate MJO convection over the Maritime Continent and further improve MJO prediction at long lead times.展开更多
文摘The Madden-Julian Oscillation is one of the large-scale climate change patterns in the maritime tropics,with sub-seasonal time periods of 30 to 60 days affecting tropical and subtropical regions.This phenomenon can cause changes in various quantities of the atmosphere and ocean,such as pressure,sea surface temperature,and the rate of evaporation from the ocean surface in tropical regions.In this research,the effects of Madden-Julian fluctuation on the weather elements of Iran have been investigated with the aim of knowing the effects of different phases in order to improve the quality of forecasts and benefits in territorial planning.At first,the daily rainfall data of 1980-2020 were received from the National Meteorological Organization and quality controlled.Using the Wheeler and Hendon method,the two main components RMM1 and RMM2 were analyzed,based on which the amplitude of the above two components is considered as the main indicator of the intensity and weakness of this fluctuation.This index is based on the experimental orthogonal functions of the meteorological fields,including the average wind levels of 850 and 200 hectopascals and outgoing long wave radiation(OLR)between the latitudes of 20 degrees south and 20 degrees north.The clustering of the 7-day sequence with a component above 1 was used as the basis for clustering all eight phases,and by calculating the abnormality of each phase compared to its long term in the DJF time frame,the zoning of each phase was produced separately.In the end,phases 1,2,7,8 were concluded as effective phases in Iran’s rainfall and phases 3,4,5,6 as suppressive phases of Iran’s rainfall.
文摘In the past decade there has been extensive research into tropical intraseasonal variability, one of the major components of the low frequency variability of the general atmospheric circulation. This paper briefly reviews the state-of-the-art in this research area: the nature of the Madden-Julian Oscillation, its relation to monsoonal and extratropical circulations, and the current theoretical understandings.
文摘2023年春季,我国西南地区发生了严重的气象干旱,对当地社会经济造成严重影响。为深入认识这次干旱事件的成因、并为未来西南地区春旱的预测提供科学依据,本文利用站点观测数据、美国国家环境预测中心和国家大气研究中心(National Centers for Environmental Prediction/National Center for Atmospheric Research,NCEP/NCAR)再分析数据、美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)的海表温度等,采用T-N波作用通量和合成分析等方法,从海温和热带大气季节内振荡(Madden-Julian Oscillation,MJO)的角度深入探讨此次春旱成因。结果表明:(1)2023年我国西南春旱是高温干旱复合事件,3月干旱发生在中部,4月干旱加剧并向西扩展,5月干旱持续。(2)3月北太平洋的马蹄形海温异常导致西风急流偏南偏西,抑制了西南地区的降水。(3)4月印度洋暖海温通过Kelvin波导致孟加拉湾附近的反气旋式环流异常,西北太平洋暖海温通过Rossby波导致南海至菲律宾的气旋式环流异常,造成西南地区南部出现偏北风,导致水汽辐散,加剧干旱。(4)5月MJO长时间维持在西太平洋,通过Gill响应引发南海至菲律宾对流层低层的气旋异常,减少偏南水汽的输送,从而使得西南干旱持续。
基金National Basic Research Program of China(2012CB417202)National Natural Science Foundation of China(41175045,91337215,Ul 133603)Special Fund for Meteorological Research in the Public Interest(GYHY201206042)
文摘This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.
基金funded by the National Natural Science Foundation of China (Grant No. 41105025)the Dragon 3 Programme (ID: 10577)
文摘The authors examined the Madden-Julian Oscillation(MJO) in stratospheric ozone during boreal winter using a simulation from the Specified Dynamics version of the Whole Atmosphere Community Climate Model(SD-WACCM) in 2004 and 2010. Comparison with European Centre for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim) data suggested that the model simulation represented well the three-dimensional structure of the MJO-related ozone anomalies in the upper troposphere and stratosphere(i.e., between 200 and 20 h Pa). The negative ozone anomalies were over the Tibetan Plateau and East Asia in MJO phases 3–7, when the MJO convective anomalies travelled from the equatorial Indian Ocean towards the equatorial western Pacific Ocean. Due to the different vertical structures of the MJO-related circulation anomalies, the MJO-related stratospheric ozone anomalies showed different vertical structure over the Tibetan Plateau(25–40°N, 75–105°E) and East Asia(25–40°N, 105–135°E). As a result of the positive bias in the model-calculated ozone in the upper troposphere and lower stratosphere, the amplitude of MJO-related stratospheric ozone column anomalies(10–16 Dobson Units(DU)) in the SD-WACCM simulation was slightly larger than that(8–14 DU) in the ERA-Interim reanalysis.
基金funded by the National Natural Science Foundation of China(Grant No.41105025)the Dragon 3 Programme(ID:10577)the High Resolution Earth Observation Funds for Young Scientists(Grant No.GFZX04060103)
文摘We investigate the Madden-Julian Oscillation （MJO） signal in wintertime stratospheric ozone over the Tibetan Plateau and East Asia using the harmonized dataset of satellite ozone profiles. Two different MJO indices -- the all-season Real-Time multivariate MJO index （RMM） and outgoing longwave radiation-based MJO index （OMI） -- are used to compare the MJO- related ozone anomalies. The results show that there are pronounced eastward-propagating MJO-related stratospheric ozone anomalies （mainly within 20-200 hPa） over the subtropics, The negative stratospheric ozone anomalies are over the Tibetan Plateau and East Asia in MJO phases 4-7, when MJO-related tropical deep convective anomalies move from the equatorial Indian Ocean towards the western Pacific Ocean. Compared with the results based on RMM, the MJO-related stratospheric column ozone anomalies based on OM1 are stronger and one phase ahead. Further analysis suggests that different sampling errors, observation principles and retrieval algorithms may be responsible for the discrepancies among different satellite measurements. The MJO-related stratospheric ozone anomalies can be attributed to the MJO-related circulation anomalies, i.e., the uplifted tropopanse and the northward shifted westerly jet in the upper troposphere. Compared to the result based on RMM, the upper tropospheric westerly jet may play a less important role in generating the stratospheric column ozone anomalies based on OMI. Our study indicates that the circulation-based MJO index （RMM） can better characterize the MJO- related anomalies in tropopause pressure and thus the MJO influence on atmospheric trace gases in the upper troposphere and lower stratosphere, especially over subtropical East Asia.
基金sponsored by the Joint Project of Natural Science Foundation of China and Yunnan Province (U0833602)
文摘This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation(MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model's mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.
基金supported by the National Natural Science Foundation of China(Grant No.42075161).
文摘As one of the participants in the Subseasonal to Seasonal(S2S)Prediction Project,the China Meteorological Administration(CMA)has adopted several model versions to participate in the S2S Project.This study evaluates the models’capability to simulate and predict the Madden-Julian Oscillation(MJO).Three versions of the Beijing Climate Center Climate System Model(BCC-CSM)are used to conduct historical simulations and re-forecast experiments(referred to as EXP1,EXP1-M,and EXP2,respectively).In simulating MJO characteristics,the newly-developed high-resolution BCC-CSM outperforms its predecessors.In terms of MJO prediction,the useful prediction skill of the MJO index is enhanced from 15 days in EXP1 to 22 days in EXP1-M,and further to 24 days in EXP2.Within the first forecast week,the better initial condition in EXP2 largely contributes to the enhancement of MJO prediction skill.However,during forecast weeks 2–3,EXP2 shows little advantage compared with EXP1-M because the increased skill at MJO initial phases 6–7 is largely offset by the degraded skill at MJO initial phases 2–3.Particularly at initial phases 2–3,EXP1-M skillfully captures the wind field and Kelvin-wave response to MJO convection,leading to the highest prediction skill of the MJO.Our results reveal that,during the participation of the CMA models in the S2S Project,both the improved model initialization and updated model physics played positive roles in improving MJO prediction.Future efforts should focus on improving the model physics to better simulate MJO convection over the Maritime Continent and further improve MJO prediction at long lead times.
