The authors investigate the statistical features of variations in the strength and position of stratospheric sudden warming (SSW) in the Northern Hemisphere based on ERA-Interim data from 1979 to 2016. It is found tha...The authors investigate the statistical features of variations in the strength and position of stratospheric sudden warming (SSW) in the Northern Hemisphere based on ERA-Interim data from 1979 to 2016. It is found that there are 55 SSW events in the past 38 years (average: 1.4 times per year), including 33 major SSW events and 22 minor SSW events. The events mainly occur in February. The variations of the maximum meridional gradient of the zonal mean temperature of the SSW events show increasing trends from 1979 to 1983 and from 1998 to 2011, and decreasing trends from 1984 to 1997 and from 2012 to 2016. However, the linear trend of the variations in the past three decades shows a negative trend. Meanwhile, the strength and duration of major SSW events show similar features. Some SSW events occur at nearly the same time at different levels from 100 hPa to 10 hPa, while others first occur at 10 hPa and then the signal propagates downwards to lower levels. A very interesting phenomenon is that the maximum temperature centers of these 55 SSW events are mainly located over the Eurasian continent between 30°E and 120°E. This may be related to a polar vortex shifting to the Eurasian continent in the past three decades.展开更多
The interannual variability of the boreal winter Hadley circulation extents during the period of 1979e2014 and its links to El Ni^no-Southern Oscillation(ENSO) were investigated by using reanalysis datasets. Results s...The interannual variability of the boreal winter Hadley circulation extents during the period of 1979e2014 and its links to El Ni^no-Southern Oscillation(ENSO) were investigated by using reanalysis datasets. Results showed that the El Ni^no(La Ni^na) events can induce the shrinking(expansion) of Hadley circulation extent in the Southern Hemisphere. For the Northern Hemisphere, El Ni^no(La Ni^na) mainly leads to shrinking(expansion) of the Hadley circulation extent in the middle and lower troposphere and expansion(shrinking) of the Hadley circulation extent in the upper troposphere. The ENSO associated meridional temperature gradients have close relationship with the Hadley circulation extents in both Hemispheres. But in the Northern Hemisphere, the ENSO associated eddy momentum flux divergence plays more important role in affecting the Hadley circulation extent than the meridional temperature gradient because of the small local Rossby number. In the Southern Hemisphere, as the ENSO induced eddy momentum flux divergence is small, the meridional temperature gradient dominates the change of the Hadley circulation extent.展开更多
Driven by the increase in CO_(2)concentration,climate models reach a consensus that the large-scale circulation of the South Asian summer monsoon(SASM) becomes weakened but with different magnitudes.This study investi...Driven by the increase in CO_(2)concentration,climate models reach a consensus that the large-scale circulation of the South Asian summer monsoon(SASM) becomes weakened but with different magnitudes.This study investigates the major uncertainty sources of the SASM response to an abrupt quadrupling of CO_(2)(abrupt-4×CO_(2))in 18 models of phase 6 of the Coupled Model Intercomparison Project.The projected weakening of the SASM indicated by both zonal and meridional monsoon circulation indices is closely linked to decreases in the meridional gradient of upper-tropospheric temperature between Eurasia and the Indian Ocean(EUTT-IUTT).A climate feedback-response analysis method is applied to linearly decompose the uncertainty of changes in EUTT-IUTT into the partial changes due to external forcing and internal processes of the earth-atmosphere column.Results show that the uncertainty of changes in EUTT-IUTT is contributed positively by the dominant atmospheric dynamic process,followed by the cloud shortwave radiative effect,and negatively by the surface latent heat flux and cloud longwave radiative effect.Contributions from CO_(2)forcing and other internal processes including albedo and water vapor feedbacks,oceanic heat storage,and sensible heat flux are found to be minor.展开更多
基金supported by the National Natural Science Foundation of China [grant numbers 41875018,91537214,and 41475037]
文摘The authors investigate the statistical features of variations in the strength and position of stratospheric sudden warming (SSW) in the Northern Hemisphere based on ERA-Interim data from 1979 to 2016. It is found that there are 55 SSW events in the past 38 years (average: 1.4 times per year), including 33 major SSW events and 22 minor SSW events. The events mainly occur in February. The variations of the maximum meridional gradient of the zonal mean temperature of the SSW events show increasing trends from 1979 to 1983 and from 1998 to 2011, and decreasing trends from 1984 to 1997 and from 2012 to 2016. However, the linear trend of the variations in the past three decades shows a negative trend. Meanwhile, the strength and duration of major SSW events show similar features. Some SSW events occur at nearly the same time at different levels from 100 hPa to 10 hPa, while others first occur at 10 hPa and then the signal propagates downwards to lower levels. A very interesting phenomenon is that the maximum temperature centers of these 55 SSW events are mainly located over the Eurasian continent between 30°E and 120°E. This may be related to a polar vortex shifting to the Eurasian continent in the past three decades.
基金supported by the National Natural Science Foundation of China (41530424)
文摘The interannual variability of the boreal winter Hadley circulation extents during the period of 1979e2014 and its links to El Ni^no-Southern Oscillation(ENSO) were investigated by using reanalysis datasets. Results showed that the El Ni^no(La Ni^na) events can induce the shrinking(expansion) of Hadley circulation extent in the Southern Hemisphere. For the Northern Hemisphere, El Ni^no(La Ni^na) mainly leads to shrinking(expansion) of the Hadley circulation extent in the middle and lower troposphere and expansion(shrinking) of the Hadley circulation extent in the upper troposphere. The ENSO associated meridional temperature gradients have close relationship with the Hadley circulation extents in both Hemispheres. But in the Northern Hemisphere, the ENSO associated eddy momentum flux divergence plays more important role in affecting the Hadley circulation extent than the meridional temperature gradient because of the small local Rossby number. In the Southern Hemisphere, as the ENSO induced eddy momentum flux divergence is small, the meridional temperature gradient dominates the change of the Hadley circulation extent.
基金jointly supported by the National Natural Science Foundation of China [grant numbers 4208810141911540470+3 种基金42075028]the Guangdong Major Project of Basic and Applied Basic Research [grant number 2020B0301030004]the Natural Science Foundation of Guangdong Province of China [grant number 2018A0303130268]the Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies [grant number2020B1212060025]。
文摘Driven by the increase in CO_(2)concentration,climate models reach a consensus that the large-scale circulation of the South Asian summer monsoon(SASM) becomes weakened but with different magnitudes.This study investigates the major uncertainty sources of the SASM response to an abrupt quadrupling of CO_(2)(abrupt-4×CO_(2))in 18 models of phase 6 of the Coupled Model Intercomparison Project.The projected weakening of the SASM indicated by both zonal and meridional monsoon circulation indices is closely linked to decreases in the meridional gradient of upper-tropospheric temperature between Eurasia and the Indian Ocean(EUTT-IUTT).A climate feedback-response analysis method is applied to linearly decompose the uncertainty of changes in EUTT-IUTT into the partial changes due to external forcing and internal processes of the earth-atmosphere column.Results show that the uncertainty of changes in EUTT-IUTT is contributed positively by the dominant atmospheric dynamic process,followed by the cloud shortwave radiative effect,and negatively by the surface latent heat flux and cloud longwave radiative effect.Contributions from CO_(2)forcing and other internal processes including albedo and water vapor feedbacks,oceanic heat storage,and sensible heat flux are found to be minor.
