2009年冬季平流层爆发性增温期间行星波活动特征

利用2008年12月至2009年4月的MERRA再分析数据资料,对2009年1月下旬北半球高纬平流层发生的强增温事件以及与之相关的行星波活动进行了研究.谱分析发现,SSW发生前后极区平流层内准16天行星波活动显著.利用二维谐波拟合法分别拟合温度场准16天波4个波模(W1,W2,E1,E2)的振幅和相位,结果表明:背景西...     

平流层冬季增温及大气中的行星波

本文利用NIMBUS-7SAMS资料分析了东经100度子午线上的两个站点(67.5°N和42.5°N)在10mb和0.0827mb高度上从1978年底至1982年间的大气温度,获得几年的平流层冬季增温结果.在1978/1979年和1981年初的冬季,高纬站点几天内出现的平流层增温最大幅度可达65K.对平流层增温的谱分析结果指出,在高纬冬季平流层有很强的16天、32夭、21天周期的行星波。中纬冬季平流层增温幅度较小,约为20K.中纬的中间层高度上整年存在有5天、8天和16天的行星波。分析研究、南、北半球不同纬度的温度随经度的分布,得出高纬冬季平流层、中间层大气温度随经度有明显的变化。波数1和波数2的波有大的幅度(主要是波数1),从高纬到低纬,波幅逐渐减小在冬季的平流层和中间层大气中,波数1和波数2的行星波在短期内可强烈增强,引起平流层冬季增温。     

武汉上空MLT中准16日波的流星雷达观测

利用武汉流星雷达2002年2月20日至2003年11月10日的观测数据,研究了武汉上空中间层-低热层(MLT)中的准16日波,即周期范围在12—20天的行星波。分析结果表明,16日波的纬向成分通常比经向成分要强．(1)在2002年和2003年,波振幅最强都出现在当年的秋季(约9月10日—10月10日)．Lomb-Scargle(L-S)谱分析得到振幅最大值约为16m／s．2002年夏季出现了同年次最强的波动,但2003年没有发现这一现象．两年的冬季都没有出现强的16日波．(2)2002年,在86—98km处波动较强,最大振幅(约16m／s)出现在90km、94km处,而2003年低高度的波动要比较高高度的波动强．武汉上空MLT中,秋季的16日波是能量上传的波动,即它的源在较低的大气层．2002年夏季的波动的能量是下行的,波源可能在南半球．     

平流层爆发性增温期间大气变化特性的COSMIC掩星观测

利用高精度和高垂直分辨率的COSMIC掩星观测资料, 详细深入分析了2007年冬---2008年春平流层爆发性增温(SSW)期间10~60 km高度范围内大气的变化特性, 尤其是上平流层和低中间层大气的变化特性. 结果表明, 在SSW过程中, 温度场、风场和剩余环流都发生了明显的变化. 根据温度在主增温前和主增温盛期的变化特性, 在水平方向, 大约以55ºN为界, 在垂直方向, 大约以42 km为界, 可以将温度场在纬度-高度的分布分为4个区域: 高纬下层增温区, 增温幅度约高达25 K; 高纬上层降温区, 降温幅度约达30,K; 中纬下层降温区, 降温幅度约为几K; 中纬上层增温区, 增温也约为几K. SSW期间上下层大气纬向风场的变化规律基本相同. 在纬度方向以45ºN为界, 45ºN以北地区的西风减弱东风增强, 风场变化高达50 m/s; 45ºN以南地区西风增强东风减弱, 变化幅度比较小, 约10 m/s. 在2008年1月下旬到2月底, 大气温度和纬向风有明显的振荡现象, 周期约为12天. 剩余环流的环流圈在SSW期间会发生反转, 由此也表明, SSW期间大气中物质的输运方向也会发生改变.     

地形对低平流层突然增温的可能影响

本文用Nimbus7 SAM卫星观测的温度资料,分析了突然增温事例中地面地形不同的四个子午圈剖面内的温度分布及变化过程。结果表明,高山地区、平原和海面上空的行星波加热和低平流层突然增温有很大的差别。地形的影响是明显的。      

大气准两年振荡对赤道行星波上传的影响

本文讨论了热带大气行星波在QBO风场中向上传播的规律,并运用数值模拟的方法,得到了开尔文波和混合罗斯贝重力波在QBO不同相位下交替上传的结果。试图用QBO对行星波的调制解释QBO在日地相关性中的作用.     

基于MST雷达数据的中纬对流层和低平流层大气行星波研究

通过分析中国河北香河站MST (Mesosphere-Stratosphere-Troposphere)雷达 2012-2014年的水平风场数据, 研究了北半球中纬地区对流层和低平流层 (Troposphere and Lower Stratosphere, TLS)区域大气行星波的特性. 谱分 析发现, 在这一区域准16天波和准10天波占据主导地位, 准16天波更为显著. 在 对流层区域, 行星波具有丰富的频谱成分, 活动具有间断性, 持续时间一般不 超过三个月, 并没有明显的季节性变化特征, 其中纬向分量的振幅大于经向分量. 在 平流层区域(高度17km以上), 行星波一般出现在冬季, 并且主要在纬向分量中. 通常平流层区域的振幅要小于对流层区域. 结合MERRA再分析资料分 析了强行星波传播特性, 结果表明: 2014年2-3月纬向分量中的准16天波垂 直向上传播, 垂直波长约为64km, 纬圈波数约为2, 纬向传播方向自西向东, 水平波长约为15324.7km, 对应的相速度为11.1m·s^-1 (向东为正); 2014年5月纬向分量中的准10天波在10~18km高度范围内向下传播, 垂直波长约为50km, 纬圈波数约为1, 传播方向自西向东, 水平波长约为 30649.4km, 对应相速为35.5m·s^-1.     

中国中部低层大气行星波无线电探空仪的观测研究

通过分析武汉、宜昌和恩施气象局无线电探空仪2001-2003年的观测数据,研究了中国中部地区对流层和低平流层中行星波的特性.通过Lomb-Scargle(L-S)的周期图方法发现了周期为准16天和周期为准10天的谱分量占据着主导地位.观察发现,较大振幅的行星波振荡主要集中在5-15 km之间.准16天行星波沿纬圈向西传播,对应的纬圈波数大约为2,水平波长约为17 324.8 km,传播相速度约为-12.5 m·s-1(东向为正),通过计算准16天行星波在10 km以下相位随高度的改变可以得到其垂直波长大约为25-30 km,而在对波层顶附近其相位几乎没有发生改变,呈现出静态波特性.准10天行星波沿纬圈向东传播,对应的纬圈波数大约为4,水平波长约为8627.3 km,传播相速度约为10.0 m·s-1,垂直波长约为22-40 km.     

重力波对中间层和低热层大气环流的影响

利用β通道准地转近似大气平均运动方程组,采用重力波线性饱和参量化方法,定性地研究大气重力波对中间层和低热层大气环流的作用.模拟计算得到,大气重力波对平均东西风速可产生100m·s^-1/d左右的作用力和产生120 m²/s的湍流扩散,这些作用平衡了Coriolis扭力,导致大气的平均东西风速大大偏离辐射平衡风场,中层顶附近的平均东西风速在冬季(夏季)甚至反转为东风(西风).平均东西风速计算结果与冬季和夏季中频雷达东西风速观测值和大气模式剖面等大致一致.     

2018－2019年平流层顶抬升事件期间的准定常行星波

2018－2019年北半球高纬地区的冬季发生了平流层顶抬升事件, 各种大气波动在该事件中所扮演的角色尚不完全清楚. 利用卫星和再分析数据, 给出了在这次ES事件发生前后平流层顶和背景大气的变化, 深入研究了准定常行星波在平流层和中间层下部的活动. 结果显示, 纬向波数为1的准定常行星1波在12月初开始增强, 在12月中旬达到最大值. 在整个12月, 即原平流层顶的下降与增温阶段, 都呈现出对背景大气强烈的西向波强迫. 在平流层顶抬升事件发生后, 该波活动减弱, 对背景大气的拽力很弱, 可能没有参与平流层顶抬升事件的后续阶段. 纬向波数为2的准定常行星在ES事件发生前活动较弱, 而在1月中旬开始增强, 在1月中旬到2月末, 即高平流层顶形成阶段以及之后的下降与增温阶段, 呈现出对背景大气的西向波强迫, 强迫中心随高度的下降与高平流层顶的下降一致, 说明该波主要在这一阶段发挥作用.     

Response of quasi-10-day waves in the MLT region to the sudden stratospheric warming in March 2020

We present an analysis of the response of quasi-10-day waves (Q10DWs) to the sudden stratospheric warming (SSW) event which occurred on March 23, 2020. The Q10DWs are observed in the mesosphere and lower thermosphere (MLT) region by three meteor radars, which are located at middle latitudes along the 120°E meridian from Mohe (MH, 53.5°N, 122.3°E), Beijing (BJ, 40.3°N, 116.2°E), to Wuhan (WH, 30.5°N, 114.6°E). The Q10DWs reveal similar temporal and altitudinal variations during the SSW in the MLT region at the three stations. The activities of Q10DWs are also captured in the temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite in the MLT region. Further analysis of the Q10DW phases indicates that the Q10DWs might be in situ generated due to mesospheric instabilities at higher latitudes around MH and then propagate southward to lower latitudes at BJ and WH. The atmospheric instabilities are not directly responsible for the excitations of Q10DWs at lower latitudes, while the observed equatorward propagation of the Q10DWs is important. Our result provides the observational evidence for latitudinal couplings in the MLT region after the SSW onset, which is achieved by southward propagating planetary waves in the MLT region.     

Investigation on the MLT tidal variability during September 2019 minor sudden stratospheric warming

Tidal variability in the mesosphere and lower thermosphere (MLT) during September 2019 Southern hemisphere minor sudden stratospheric warming (SSW) is investigated utilizing ground-based meteor radar wind observations from the equatorial, extratropical, middle, and high latitude stations and global reanalysis dataset. The polar warming is found to move from the mesosphere to the stratosphere until the peak warming day (PWD) of the SSW. The diurnal and semidiurnal tides at individual observational sites do not exhibit any consistent response during the observational interval, but a notable and consistent variability in some specific zonal wavenumber components, i. e., DW1 (migrating diurnal tide), DE3 (nonmigrating eastward wavenumber 3 diurnal tide), and SW2 (migrating semidiurnal tide) is found in the global reanalysis dataset. Incidentally, the warming event occurs during Spring equinox when a dominant seasonal change in the tidal activities generally takes place and hence seasonal variability is also looked into while identifying the SSW impact during the observational interval. It is found that the seasonal broad changes in the DW1, DE3, and SW2 amplitudes can be explained by the variability in the tidal sources, i.e., water vapor, convective activity, ozone, etc during the observational period. However, the extracted short-term variability in the global tidal modes on removing seasonal trend reveals noticeable response in connection with the warming event. The deseasoned amplitude of the DW1 significantly enhances around the PWD at most of the present latitudes. The deseasoned DE3 amplitude responds significantly in the middle atmosphere at low latitudes during the warming phase. The deseasoned SW2 exhibit clear enhancement around the PWD at all the latitudes. However, the deseasoned tidal features do not seem to correlate well with that of the source species unlike the seasonal ones that imply involvement of complex processes during the warming event, seeking further future investigations in this regard.     

Simulating planetary wave propagation to the upper atmosphere during stratospheric warming events at different mountain wave scenarios

Parameterization schemes of atmospheric normal modes (NMs) and orographic gravity waves (OGWs) have been implemented into the mechanistic Middle and Upper Atmosphere Model (MUAM) simulating atmospheric general circulation. Based on the 12-members ensemble of runs with the MUAM, a composite of the stratospheric warming (SW) has been constructed using the UK Met Office data as the lower boundary conditions. The simulation results show that OGW amplitudes increase at altitudes above 30 km in the Northern Hemisphere after the SW event. At altitudes of about 50 km, OGWs have largest amplitudes over North American and European mountain systems before and during the composite SW, and over Himalayas after the SW. Simulations demonstrate substantial (up to 50–70%) variations of amplitudes of stationary planetary waves (PWs) during and after the SW in the mesosphere-lower thermosphere of the Northern Hemisphere. Westward travelling NMs have amplitude maxima not only in the Northern, but also in the Southern Hemisphere, where these modes have waveguides in the middle and upper atmosphere. Simulated variations of PW and NM amplitudes correspond to changes in the mean zonal wind, EP-fluxes and wave refractive index at different phases of the composite SW events. Inclusion of the parameterization of OGW effects leads to decreases in amplitudes (up to 15%) of almost all SPWs before and after the SW event and their increase (up to 40–60%) after the SW in the stratosphere and mesosphere at middle and high northern latitudes. It is suggested that observed changes in NM amplitudes in the Southern Hemisphere during SW could be caused by divergence of increased southward EP-flux. This EP-flux increases due to OGW drag before SW and extends into the Southern Hemisphere.     

Height-latitude structure of stationary planetary waves in the stratosphere and lower mesosphere

Daily UK Met Office stratospheric assimilated data for the Northern and Southern Hemispheres, accumulated for the period from 2004 to 2012 and pressure range of 1000–0.1 hPa, are used in this paper. The paper presents and thoroughly discusses spatial–temporal distributions of stationary planetary wave (SPW) amplitudes and phases, calculated on the basis of geopotential height, temperature, zonal and meridional wind data for zonal wave numbers 1 and 2 (SPW1 and SPW2). The climatological planetary wave amplitudes and phases are calculated by extracting waves from three types of data: daily, monthly mean and climatological monthly mean. It has been established that magnitude of amplitudes and height-latitude distribution of amplitudes of SPW1 and SPW2 depend on data processing method for all parameters. It has also been established that height-latitude distribution amplitudes and phases significantly differ for geopotential height, temperature, zonal and meridional wind and depend on wave number and hemisphere. However, height-latitude distributions of phases are little different from each other for the used methods of data processing.     

Longitudinal MLT wind structure at higher mid-latitudes as seen by meteor radars at central and Eastern Europe (13°E/49°E)

The mid-latitude mesosphere and lower thermosphere (MLT) wind speeds measured by two SKiYMET meteor radars (MRs) at Collm (51°N, 13°E) and Kazan (56°N, 49°E) during 2016–2017 were analyzed to study longitudinal wind structures. The differences between monthly mean prevailing wind speeds and tidal amplitudes were compared with the corresponding differences obtained from TIMED/TIDI satellite winds and gradient wind speeds from the AURA/MLS instrument. It is shown that the MR wind difference between the two sites is statistically significant. The difference of the horizontal prevailing winds can be explained by a superposition of the background zonal flow, which is different at the two latitudes, with stationary planetary waves of different origin. Non-migrating tides contribute significantly to the difference of the semidiurnal tidal winds between the two sites.