The Discussion Of The Influence Of QBO And SSW Over Quasi-zero Wind Layers

This paper uses ERA-Interim data sets,including month data sets and daily data sets of zonal wind fields and temperature fields,from ECWMF(European Centre for Medium-Range Weather Forecasts).These data sets' resolution ratio is 0.75°x0.75°.Composite analysis,wavelet analysis and EOF analysis are used to analyze QZWL(Quasi-zero wind layer)'s distribution and QZWL's Influence factors such as seasons,QBO(quasi-biennial oscillation)and SSW(Stratospheric Sudden Warming)in this paper.Main conclusions are followed:(1)In winters,QZWLs' range is the biggest at 15°N.mainly located at 50hPa;In springs,QZWLs are mainly located at high and low layers of stratosphere at low latitudes;In summers,QZWLs are mainly located at 70hPa of mid-high latitudes;In autumns.QZWLs are mainly located at stratopause at low latitudes and 28km as well as 21km at middle latitudes,there is almost no QZWL at high latitudes;(2)QZWLs' consistency is pretty good over latitudes;(3)QBO' consistency is pretty good over latitudes;East wind phase is much stronger than West wind phase;QBO's cycle is about 28.3 months;there is a center of change at 20hPa and 30hPa respectively;QBO's speed of propagate downward is about 0.9km-1.0km per month;(4)In terms of phases,at the first phase,a west wind disturbance is in the process of blending in the west wind zone at tropopause and the low layer of stratosphere,The QZWL above it is located at about 50hPa,a new west wind disturbance is in formation at the high layer of the stratosphere;at the second phase,the west wind disturbance in the low stratosphere has completely blended in the west wind zone,the west wind disturbance at high layer of stratosphere has already propagated downward,the QZWL formed below is located at about lOhPa;at the third phase,the west wind disturbance has already been mature and propagated downward,the QZWL formed above is located above 10hPa,the QZWL formed below is located between 30hPa and 70hPa;at the fourth phase,the west wind disturbance has propagated downward the low layer of stratosphere,is blending in the west wind zone at this level,the QZWL formed above is located at about 30hPa,the QZWL formed below is located at about 100hPa;(5)In the terms of seasons,from winter to summer,the thermal wind at the troposphere decreases and the thermal wind at the stratosphere turns to the opposite direction,so the wind of the stratosphere changes from west wind to east wind and thus there is a stable QZWL formed at high latitudes;in addition,QZWLs formed because of QBO at the low latitudes are also influenced by seasons:when at the same QBO phase,there will be one more QZWL at the high layer of the stratosphere at low latitudes in springs than in winters,when it comes to summers,the north Hemisphere part of QZWLs at low latitudes vanish,when it comes to autumns,the QZWL at the high layer of the stratosphere at the low latitudes recover;(6)When SSWs happens,there will be east wind zone forming at the winter stratosphere which is fully controlled by west wind before.With the forming,development and vanish of east zones,unstable QZWLs located at the boundary between east and west winds will form,change and vanish.