The distribution characters of the stratospheric Brewer-Dobson circulation inferred from ERA-Interim
Author(s): WANG Wei-Guo, YANG Fang-Yuan, WANG Hao-Yue, YANG Tao, YU Ke, LIANG Shu-Kun, FAN Wen-Xuan, Department of Atmospheric Sciences, Yunnan University, Meteorological Bureau of Kunming, Meteorological Bureau of Yuxi, Meteorological Information Center of Yunnan Province
Pages: 371-382
Year: 2015 Issue: 2
Journal: Chinese Journal of Geophysics
Keyword: Brewer-Dobson circulation; Residual velocity; Mass flux; Zonal mean temperature;
Abstract: The spatial-temporal distribution characters of trace gases in the stratosphere and troposphere are affected by the Brewer-Dobson(BD)circulation.Understanding the distribution characters of BD circulation is very important to further study the influence of stratosphere and troposphere exchange and forecast the global climate change.The BD circulation is described as the Lagrangian-mean circulation,it is difficult to diagnose directly from meteorological observations.The methods of the transformed Eulerian-mean(TEM)equations,and integrating residual meridional velocity in the vertical were used to analyze the spatial-temporal distribution characters of BD circulation,by using the ERA-Interim reanalysis data for 1979—2011at 12∶00UTC.We further compared the distribution characters of BD circulation with the result calculated by the method of DC(downward control)principle and studied the relationship between the stratospheric zonal mean temperature and BD circulation.The BD circulation was calculated from ERA-Interim reanalysis data for 1979—2011 by integrating residual meridional velocity in the vertical.The results showed that:(1)The ascending centers of BD circulation were varied with seasons.It ascended at 30°S in the stratosphere for December to February(DJF),for June to August(JJA)it ascended between 25°N and 30°N,the circulation pattern in the winter hemisphere is stronger than the summer hemisphere.In March to May(MAM)and September to November(SON),the ascending center were between equator to 5°N,and circulation were relatively symmetrically for two hemispheres.(2)The maximum mass flux in the tropical and extratropical northern hemisphere appeared during DJF,the minimum appeared during JJA.The mass flux in extratropical southern hemisphere was just the opposite.Mass flux across the 100 hPa and 50 hPa pressure surface in tropical and extratropical trended to decreasing,and also had obviously seasonal variation.(3)The long-term trend of stratospheric zonal mean temperature was consistent with the long-term weakening trend of BD circulation,this indicated that the global BD circulation has been weakened.Meanwhile,the zonal mean temperature in different altitude and latitude bands varied with seasons.From the perspective of the global mass transportation,the stratospheric BD circulation has been weakened in the past 33 years,especially in the middle and lower stratosphere,and was consistent with the long-term trend of temperature.This weakened trend was consistent with the observation study in the age of stratospheric air and other model results.But the method of DC principle,GCMs model and other studies showed that the stratospheric BD circulation has been enhanced in the past years.Using different methods and data would lead the trend estimation of BD circulation were unreliable.Therefore,further research will be required to improve the reliability of BD circulation.
Pages: 371-382
Year: 2015 Issue: 2
Journal: Chinese Journal of Geophysics
Keyword: Brewer-Dobson circulation; Residual velocity; Mass flux; Zonal mean temperature;
Abstract: The spatial-temporal distribution characters of trace gases in the stratosphere and troposphere are affected by the Brewer-Dobson(BD)circulation.Understanding the distribution characters of BD circulation is very important to further study the influence of stratosphere and troposphere exchange and forecast the global climate change.The BD circulation is described as the Lagrangian-mean circulation,it is difficult to diagnose directly from meteorological observations.The methods of the transformed Eulerian-mean(TEM)equations,and integrating residual meridional velocity in the vertical were used to analyze the spatial-temporal distribution characters of BD circulation,by using the ERA-Interim reanalysis data for 1979—2011at 12∶00UTC.We further compared the distribution characters of BD circulation with the result calculated by the method of DC(downward control)principle and studied the relationship between the stratospheric zonal mean temperature and BD circulation.The BD circulation was calculated from ERA-Interim reanalysis data for 1979—2011 by integrating residual meridional velocity in the vertical.The results showed that:(1)The ascending centers of BD circulation were varied with seasons.It ascended at 30°S in the stratosphere for December to February(DJF),for June to August(JJA)it ascended between 25°N and 30°N,the circulation pattern in the winter hemisphere is stronger than the summer hemisphere.In March to May(MAM)and September to November(SON),the ascending center were between equator to 5°N,and circulation were relatively symmetrically for two hemispheres.(2)The maximum mass flux in the tropical and extratropical northern hemisphere appeared during DJF,the minimum appeared during JJA.The mass flux in extratropical southern hemisphere was just the opposite.Mass flux across the 100 hPa and 50 hPa pressure surface in tropical and extratropical trended to decreasing,and also had obviously seasonal variation.(3)The long-term trend of stratospheric zonal mean temperature was consistent with the long-term weakening trend of BD circulation,this indicated that the global BD circulation has been weakened.Meanwhile,the zonal mean temperature in different altitude and latitude bands varied with seasons.From the perspective of the global mass transportation,the stratospheric BD circulation has been weakened in the past 33 years,especially in the middle and lower stratosphere,and was consistent with the long-term trend of temperature.This weakened trend was consistent with the observation study in the age of stratospheric air and other model results.But the method of DC principle,GCMs model and other studies showed that the stratospheric BD circulation has been enhanced in the past years.Using different methods and data would lead the trend estimation of BD circulation were unreliable.Therefore,further research will be required to improve the reliability of BD circulation.
Related Articles