Dynamical Diagnoses And Analyses Of The Northern Hemisphere Stratospheric Sudden Warming In Winter

In this paper we diagnose the dynamical characteristics of an intense stratospheric sudden warming broke out from December 2003 to March 2004 by using the ECMWF model daily data. By investigating the abnormality of stratospheric circulation, interaction between planetary wave and basic flow, propagation of zonal wind and temperature variation inducing by the oscillation of polar vortex, and exchange between stratosphere and troposphere, we draw the conclusions as follows:1. This SSW event has a long and intense process. After the beginning of warming and variation of zonal average wind in higher stratosphere, the abnormality of stratospheric circulation developed downward and the SSW lasted about three months. During the progress of this SSW, polar vortex weakened and divided into two parts from upper stratosphere to lower. With the establishment of zonal easterlies in 10hPa altitude, transport of energy and heat by planetary wave began to descend, making the broken polar vortex start to reconstruct from upper level. Above the 10hPa altitude, polar vortex recovered and reestablished soon after the beginning of SSW.2. During the process of SSW with polar vortex oscillation, there is a pair of propagating modes which are pole-ward and downward in stratosphere and an equator-ward propagating mode in troposphere. Along with these two modes, zonal wind and temperature anomalies transport as two opposite signals. These two propagating modes mentioned above have some relations in time scale, which is that the starting time of the equator ward propagating is nearly the same as the arrival time of pole ward propagating, and we can explain the variance of polar vortex by a meridional mass circulation driven by both diabatic heating in low latitudes and baroclinic eddies. This circulation leads to the exchange of warm and cold air between the high and low latitudes areas and stratosphere to troposphere, making the reestablishment of the whole atmosphere dynamical and thermal characteristics.3. The residual circulation in stratosphere reversed after SSW, inducing the alternation of transmission between high and low latitudes and distribution in different vertical levels. Because ozone is the most significant air to the sustainment of stratospheric radiation equilibrium, the affection of residual circulation to the stratosphere can't be ignored.4. By comparing to the development of 02-03 SSW, we found that the constitution of zonal easterlies in 10hPa altitude prevent the planetary wave transporting through this level and the energy bringing by planetary wave operated to the lower atmosphere below 10hPa. After erectingθ-PVLAT coordinate, we draw a conclusion that this kind of warming mode like 03-04 is propitious to the propagation of circulation anomalies from stratosphere to troposphere, and has more affection on STE. Therefore, this facet of SSW attracts us to contribute more attention to investigate the evolution of stratospheric circulation abnormal signals.