摘要
Researchers have paid much attention to the influence of the tropical zonal wind quasi-biennial oscillation (QBO) on tropical methane,while generally ignoring the change in extra-tropical methane.The present study analyzed the interannual changes in the methane mixing ratio in extra-tropics of both the Southern Hemisphere (SH) and Northern Hemisphere (NH) using Halogen Occultation Experiment (HALOE) satellite data.The results show that interannual changes in extra-tropical methane exhibit QBO features in both hemispheres that are obviously different from those in the tropics.The extra-tropical methane QBO perturbations usually occur in two layers and are longitudinally asymmetrical about the equator.The amplitude of the methane QBO disturbance in the extra-tropics is smaller than that in the tropics from 10 to 1 hPa but much larger in the layer from 30 to 10 hPa.The interannual relative changes in the methane mixing ratio are similar in both the NH extra-tropics and the tropics in the middle and upper stratosphere.Using the National Center for Atmospheric Research two-dimensional,interactive chemical dynamical radiative model (SOCRATES),simulation was conducted to investigate the mechanism of the extra-tropical methane QBO.The results indicate that the tropical stratospheric zonal wind QBO results in the QBO of the induced residual circulation.It is the transport of methane by the induced residual circulation that causes the methane QBO in the extra-tropics.The induced residual circulations in the middle and upper stratosphere are not always longitudinally symmetrical about the equator,resulting in different distribution of the methane QBO in the SH and NH extra-tropics.
Researchers have paid much attention to the influence of the tropical zonal wind quasi-biennial oscillation （QBO） on tropical methane,while generally ignoring the change in extra-tropical methane.The present study analyzed the interannual changes in the methane mixing ratio in extra-tropics of both the Southern Hemisphere （SH） and Northern Hemisphere （NH） using Halogen Occultation Experiment （HALOE） satellite data.The results show that interannual changes in extra-tropical methane exhibit QBO features in both hemispheres that are obviously different from those in the tropics.The extra-tropical methane QBO perturbations usually occur in two layers and are longitudinally asymmetrical about the equator.The amplitude of the methane QBO disturbance in the extra-tropics is smaller than that in the tropics from 10 to 1 hPa but much larger in the layer from 30 to 10 hPa.The interannual relative changes in the methane mixing ratio are similar in both the NH extra-tropics and the tropics in the middle and upper stratosphere.Using the National Center for Atmospheric Research two-dimensional,interactive chemical dynamical radiative model （SOCRATES）,simulation was conducted to investigate the mechanism of the extra-tropical methane QBO.The results indicate that the tropical stratospheric zonal wind QBO results in the QBO of the induced residual circulation.It is the transport of methane by the induced residual circulation that causes the methane QBO in the extra-tropics.The induced residual circulations in the middle and upper stratosphere are not always longitudinally symmetrical about the equator,resulting in different distribution of the methane QBO in the SH and NH extra-tropics.
基金
National Basic Research Program of China (2010CB428603)
