Impact of stratospheric variability on tropospheric climate change

An improved stratospheric representation has been included in simulations with the Hadley Centre HadGEM1 coupled ocean atmosphere model with natural and anthropogenic forcings for the period 1979–2003. An improved stratospheric ozone dataset is employed that includes natural variations in ozone as well as the usual anthropogenic trends. In addition, in a second set of simulations the quasi biennial oscillation (QBO) of stratospheric equatorial zonal wind is also imposed using a relaxation towards ERA-40 zonal wind values. The resulting impact on tropospheric variability and trends is described. We show that the modelled cooling rate at the tropopause is enhanced by the improved ozone dataset and this improvement is even more marked when the QBO is also included. The same applies to warming trends in the upper tropical troposphere which are slightly reduced. Our stratospheric improvements produce a significant increase of internal variability but no change in the positive trend of annual mean global mean near-surface temperature. Warming rates are increased significantly over a large portion of the Arctic Ocean. The improved stratospheric representation, especially the QBO relaxation, causes a substantial reduction in near-surface temperature and precipitation response to the El Chichón eruption, especially in the tropical region. The winter increase in the phase of the northern annular mode observed in the aftermath of the two major recent volcanic eruptions is partly captured, especially after the El Chichón eruption. The positive trend in the southern annular mode (SAM) is increased and becomes statistically significant which demonstrates that the observed increase in the SAM is largely subject to internal variability in the stratosphere. The possible inclusion in simulations for future assessments of full ozone chemistry and a gravity wave scheme to internally generate a QBO is discussed.     

Influence of the 11-year solar cycle on the effects of the equatorial quasi-biennial oscillation, manifesting in the extratropical northern atmosphere

Using the longest and most reliable ozonesonde data sets grouped for four regions (Japan, Europe, as well as temperate and polar latitudes of Canada) the comparative analysis of regional responses of ozone, temperature, horizontal wind, tropopause and surface pressure on the equatorial quasi-biennial oscillation (QBO effects), manifesting in opposite phases of the 11-year solar cycle (11-yr SC) was carried out. The impact of solar cycle is found to be the strongest at the Canadian Arctic, near one of two climatological centres of polar vortex, where in solar maximum conditions the QBO signals in ozone and temperature have much larger amplitudes, embrace greater range of heights, and are maximized much higher than those in solar minimum conditions. The strengthening of the temperature QBO effect during solar maxima can explain why correlation between the 11-yr SC and polar winter stratospheric temperature is reversed in the opposite QBO phases. At the border of polar vortex the 11-yr SC also modulates the QBO effect in zonal wind, strengthening the quasi-biennial modulation of polar vortex during solar maxima that is associated with strong negative correlation between stratospheric QBO signals in zonal wind and temperature. Above Japan the QBO effects of ozone, temperature, and zonal wind, manifesting in solar maxima reveal the downward phase dynamics, reminding similar feature of the zonal wind in the equatorial stratosphere. Above Europe, the QBO effects in solar maxima reveal more similarity with those above Japan, while in solar minima with the effects obtained at the Canadian middle-latitude stations. It is revealed that the 11-yr SC influences regional QBO effects in tropopause height, tropopause temperature and surface pressure. The influence most distinctly manifest itself in tropopause characteristics above Japan. The results of the accompanying analysis of the QBO reference time series testify that in the period of 1965–2006 above 50-hPa level the duration of the QBO cycle in solar maxima is 1–3 months longer than in solar minima. The differences are more distinct at higher levels, but they are diminished with lengthening of the period.     

IAP-AGCM对QBO模拟的动量收支分析

平流程准两年振荡(QBO)是赤道平流层(～100-1 hPa)变率的主要模态,可对中高纬地区的环流产生重要影响,但目前利用通用大气环流模式(GCM)对其进行准确模拟仍然是一个挑战.本文利用IAP大气环流模式(IAP-AGCM)的中高层大气模式版本(IAP-AGCML69)对QBO进行模拟,并对其动量收支情况进行分析.研究发现,QBO主要是由对流活动引起的重力波强迫(参数化)引起的,但该动量强迫被平流层赤道上升流所引起的平流过程显著削弱.模式可分辨尺度的波动强迫对赤道上空的QBO的总纬向风倾向有正贡献,在上平流层,其量值大小与参数化的重力波强迫相当.以上结果提供了QBO形成机制以及模式模拟差异可能原因的认识.     

NUMERICAL INVESTIGATION OF QBO IN OZONE

In this paper, a two-dimensional primitive equation model, coupling dynamical, radiative andphotochemical processes, is used to simulate the quasi-biennial oscillation (QBO) in ozone. TheQBO in total ozone has been successfully simulated when the forcing of equatorial stratosphericQBO in zonal wind is imposed. The simulated characters of QBO in ozone are in close agreementwith those observed. We further analyzed the mechanism of formation and maintenance of QBO inozone. In the different phases of QBO in equatorial stratospheric wind field, the global circulationhas so great difference that it makes the effects of advection transfer and eddy transfer present aquasi-biennial periodical variation. Chemical effect and dynamical effect are basically out-of-phase.They together form and maintain the QBO in ozone. Total variation rate is a tiny difference of thetwo large amounts. At the lower level of middle-high latitudes, however, it has a phase differenceof about 1-2 months between dynamical and negative chemical effects, where the dynamical effectis comparatively greater. QBO in ozone has no clear counter effects on atmospheric circulation. The experiment resultsshow that the effects of QBO in ozone on temperature field and wind field are very small.     

低平流层准两年变率研究

分析ＮＣＡＲ／ＮＣＥＰ４０年分析资料得出,赤道低平流层纬向风年际变率的平均周期约２８．２个月,最大振幅的２０ｈＰａ,西（东）风距平平垂直下传平均速度１．２１（１．０４）ｋｍ／月。用１０ｈＰａ和７０ｈＰａ月平均纬向风标准化距平之差反映整层准两年变率的相位。低平流层两半球中纬气温有与之配合的振荡,西（东）风切变时,中纬气温偏低（高）。赤道纬向风准两年变率引起的经圈环流异常是联系低续续向风与中纬气温准年     

低平流层准两年变率研究

分析NCAR/NCEP40年再分析资料得出,赤道低平流层纬向风年际变率的平均周期约28.2个月,最大振幅在20hPa,西(东)风距平垂直下传平均速度1.21(1.04)km/月。用10hPa和70hPa月平均纬向风标准化距平之差可反映整层准两年变率的相位,低平流层两半球中纬气温有与之配合的振荡,西(东)风切变时,中纬气温偏低(高)。赤道纬向风准两年变率引起的经圈环流异常是联系低纬纬向风与中纬气温准两年变率的纽带。     

Simulation of the QBO in IAP-AGCM: Analysis of momentum budget: IAP-AGCM对QBO模拟的动量收支分析

The quasi-biennial oscillation (QBO), a dominant mode of the equatorial stratospheric (~100–1 hPa) variability, is known to impact tropospheric circulation in the middle and high latitudes. Yet, its realistic simulation in general circulation models remains a challenge. The authors examine the simulated QBO in the 69-layer version of the Institute of Atmospheric Physics Atmospheric General Circulation Model (IAP-AGCML69) and analyze its momentum budget. The authors find that the QBO is primarily caused by parameterized gravity-wave forcing due to tropospheric convection, but the downward propagation of the momentum source is significantly offset by the upward advection of zonal wind by the equatorial upwelling in the stratosphere. Resolved-scale waves act as a positive contribution to the total zonal wind tendency of the QBO over the equator with comparable magnitude to the gravity-wave forcing in the upper stratosphere. Results provide insights into the mechanism of the QBO and possible causes of differences in models.摘要平流层准两年振荡 (QBO) 是赤道平流层 (~100–1 hPa) 变率的主要模态, 可对中高纬地区的环流产生重要影响, 但目前利用通用大气环流模式 (GCM) 对其进行准确模拟仍然是一个挑战.本文利用IAP大气环流模式 (IAP-AGCM) 的中高层大气模式版本 (IAP-AGCML69) 对QBO进行模拟, 并对其动量收支情况进行分析.研究发现, QBO主要是由对流活动引起的重力波强迫 (参数化) 引起的, 但该动量强迫被平流层赤道上升流所引起的平流过程显著削弱.模式可分辨尺度的波动强迫对赤道上空的QBO的总纬向风倾向有正贡献, 在上平流层, 其量值大小与参数化的重力波强迫相当.以上结果提供了对QBO形成机制以及模式模拟差异可能原因的认识.     

Interannual variations in total ozone fields at high latitudes of the Northern Hemisphere, November to March 1998–2005

Synoptic analysis of monthly and daily mean total ozone fields is carried out using ground-based (Roshydromet) and TOMS measurements. Large interannual changes in the evolution of the stratospheric polar vortex and the North Pacific anticyclone influence the formation and dynamics of the winter-spring ozone fields in the stratosphere of high northern latitudes. The analysis shows considerable variations in the direction of zonal ozone transport from the sector of ozone inflow from low latitudes and accumulation in the Far East depending on the winter polar stratosphere temperature and the quasi-biennial oscillation (QBO) phase. In years with the easterly QBO phase and the warm polar stratosphere, ozone at the end of winter is transported to northeastern Canada and Atlantic. In years with the easterly phase and cold polar stratosphere, ozone transport is directed to northern Eurasia. These characteristics will be verified on extensive observational data.     

赤道平流层QBO与我国7月雨型的关联

根据1953～1991年赤道平流层纬向风资料分析,得出我国东部地区7月份主要雨带位置与赤道平流层30～50 hPa平均纬向风准两年振荡（以下简称赤道平流层QBO）有较好的关联。在西风位相条件下,我国7月主要雨带位置较偏北;在东风位相条件下,我国7月主要雨带位置易偏南。它们之间的关系主要是通过对对流层环流的影响相联系的。利用赤道平流层纬向风的变化规律并结合冬季北太平洋对流层环流特征,对我国7月主要雨带类型的预报,有一定实用意义。     

基于DART +WACCM模式搭建的平流层同化、天气预报和气候预测模型研究

本论文基于WACCM（Whole Atmosphere Community Climate Model）模式最新版本WACCM6和DART（Data Assimilation Research TestBed）同化工具最新版本Manhattan,开发了中高层大气温度、臭氧和水汽卫星资料的同化接口,搭建了一个包含完整平流层过程的数值同化、天气预报和短期气候预测模型（此后简称模型）;本模型对2020年3～4月平流层大气变化进行了同化观测资料的模拟,并以同化试验输出的分析场作为初值,对5～6月的平流层大气进行了0～30天天气尺度预报以及31～60天短期气候尺度预测的回报试验。结果表明:本模型能较好地重现2020年3、4月北极平流层出现的大规模臭氧损耗事件随时间的演变特征,模拟结果和Microwave Limb Sounder（MLS）卫星观测结果很接近;而未进行同化的模拟试验,虽然可以模拟出北极臭氧损耗现象,但是模拟的臭氧损耗规模相比MLS卫星观测结果要低很多;利用同化试验4月末输出的分析场作为初值,预报的5月北极平流层臭氧体积混合比变化与MLS卫星观测值的差值小于0.5,预测的6月北极平流层臭氧变化只在10～30 hPa之间的区域,与观测之间的差异达到了1 ppm（ppm=10?6）。本模型不但改善了北极平流层化学成分变化的模拟,也显著地提升了北极平流层温度和环流的模拟。本模型同化模拟的3～4月、预报预测的5～6月北极平流层温度和纬向风变化与Modern-Era Retrospective analysis for Research and Applications, Version 2 （MERRA2）再分析资料结果具有很好的一致性,仅在北极平流层顶部,预报预测的温度和纬向风分别与再分析资料之间的均方根误差（RMSE）约为3 K和4 m s?1。未进行同化的试验模拟的3～4月、预报预测的5～6月北极平流层的温度和纬向风与MERRA2再分析资料之间的RMSE在大部分区域都达到6 K及5 m s?1以上。从全球范围来看,本模型对平流层中低层模拟性能改善最为显著,其预报预测结果与观测值之间的差异,比未进行同化试验的结果,减少了50%以上。     

北半球冬季行星波的传播及其输运作用

利用变换欧拉平均方程讨论了行星波动力学。观测和模拟结果都表明,在北半球冬季准定常行星波的经向传播存在两支波导。一支为高纬度波导,另一支则为低纬度波导。这些结果与理论分析相当一致。通过对EP通量进一步的研究表明,平流层爆发性增温是沿高纬度波导传播的异常行星波与平均气流相互作用的结果。而热带风场的准两年周期振荡（QBO）是低纬度平流层下层大气纬向平均流的一个重要年际变化,它可以影响行星波沿低纬度波导的传播;此外,由一个行星波一平均流耦合模式模拟的结果表明,这个热带风场的变化还可以通过波流相互作用调制行星波沿高纬度波导的传播。 行星波对臭氧的输运作用在文中也进行了分析。行星波强迫出的剩余平均环流表明,耗散的行星波有强的输运作用;向北的涡动热量输送可以强迫出一个正的输运环流,其在低纬度上升并在高纬度下沉。同时研究还表明,热带风场的QBO对行星波传播的调制对输运环流也有重要影响,模式结果表明,在QBO的东风位相期间行星波引起的输运作用明显增强,其结果可用于解释平流层高纬度臭氧的年际变化。     

赤道低平流层纬向风垂直切变与ENSO变率的关系

利用NCEP／NCAR 40a再分析资料研究了赤道低平流层纬向风垂直切变与ENSO变率间的关系。结果得出，赤道低平流层纬向风的垂直切变呈现明显的准两年振荡，SOI和Nino3区SSTA的准两年周期成分与赤道低平流层纬向风垂直切变分别呈现反位相和同位相关系。赤道低平流层西（东）风切变位相时，OLR、1000hPa高度，2000hPa高度和温度、850hPa温度等要素的距平分布与其在El Nino(La Nina)时段的分布相似。     

Connection of stratospheric QBO with global atmospheric general circulation and tropical SST. Part I: methodology and composite life cycle

The stratospheric quasi-biennial oscillation (QBO) and its association with the interannual variability in the stratosphere and troposphere, as well as in tropical sea surface temperature anomalies (SSTA), are examined in the context of a QBO life cycle. The analysis is based on the ERA40 and NCEP/NCAR reanalyses, radiosonde observations at Singapore, and other observation-based datasets. Both reanalyses reproduce the QBO life cycle and its associated variability in the stratosphere reasonably well, except that some long-term changes are detected only in the NCEP/NCAR reanalysis. In order to separate QBO from variability on other time scales and to eliminate the long-term changes, a scale separation technique [Ensemble Empirical Mode Decomposition (EEMD)] is applied to the raw data. The QBO component of zonal wind anomalies at 30?hPa, extracted using the EEMD method, is defined as a QBO index. Using this index, the QBO life cycle composites of stratosphere and troposphere variables, as well as SSTA, are constructed and examined. The composite features in the stratosphere are generally consistent with previous investigations. The correlations between the QBO and tropical Pacific SSTA depend on the phase in a QBO life cycle. On average, cold (warm) SSTA peaks about half a year after the maximum westerlies (easterlies) at 30?hPa. The connection of the QBO with the troposphere seems to be associated with the differences of temperature anomalies between the stratosphere and troposphere. While the anomalies in the stratosphere propagate downward systematically, some anomalies in the troposphere develop and expand vertically. Therefore, it is possible that the temperature difference between the troposphere and stratosphere may alter the atmospheric stability and tropical deep convection, which modulates the Walker circulation and SSTA in the equatorial Pacific Ocean.     

中部型ENSO和平流层准两年振荡对冬季北半球平流层臭氧的联合调制作用

利用观测和再分析资料通过合成分析方法,研究了中部型ENSO和平流层准两年振荡（QBO）对冬季北半球平流层臭氧的独立影响和联合调制作用。研究表明,北半球平流层臭氧在中部型厄尔尼诺年增加,而在中部型拉尼娜年减少;准两年振荡东风位相年份,北半球平流层臭氧增加,准两年振荡西风位相结果则相反。相比之下,北半球中、高纬度平流层臭氧异常对准两年振荡活动的响应明显小于其对ENSO活动的响应。进一步研究发现,准两年振荡东风位相会加强中部型厄尔尼诺事件引起的北半球平流层臭氧的增加,而减弱中部型拉尼娜事件造成的平流层臭氧的减少。在准两年振荡西风位相下,中部型厄尔尼诺事件仅导致北半球平流层臭氧含量少量升高,而中部型拉尼娜事件期间臭氧会大幅度减少。因此,准两年振荡东风位相会加强中部型厄尔尼诺事件对北半球平流层臭氧的影响,而减弱中部型拉尼娜事件对北半球平流层臭氧的影响。准两年振荡西风位相会减弱中部型厄尔尼诺而加强中部型拉尼娜事件对北半球平流层臭氧的影响。      

Interrelation between QBO and 11-year solar cycle effects in total column ozone over Europe

On the basis of total column ozone (TO) data obtained in the period of 1957–2007 at 10 ground-based European stations, characterized by long and highly reliable measurements, the effects of the quasi-biennial oscillation (QBO) and 11-year solar cycle (11-year SC), manifesting in TO are investigated. The results of comparative analysis of seasonal differences between different QBO/solar extremes convincingly demonstrate interrelation between the QBO and 11-year SC effects. It is shown that solar activity modulates the phase of the QBO effect so that the quasi-biennial TO signals during solar maximum and solar minimum are nearly in opposite phase. It is also demonstrated that isolated under permanent conditions of solar minimum or solar maximum the QBO effects in TO have the time scale of about 20 months. Solar modulation of the QBO effect makes the QBO a conductor of the solar cycle impact on TO over Europe. The mechanism of influence of the 11-year SC on the QBO and probably includes its impact on the QBO amplitude in the equatorial lower stratosphere, mainly through weakening of the equatorial easterlies during solar maximum.     

热带平流层臭氧准两年周期振荡的特征及数值模拟

利用HALOE的观测资料、对热带地区平流层臭氧垂直分布的年际变化及其准两年周期振荡（QBO）进行研究，并同赤道上空平均的纬向风场的准两年周期振荡进行了模拟研究。资料分析结果表明，平流层臭氧浓度高值区的位置在南北方向上和垂直方向上的有明显的准两年周期，臭氧浓度高值中心的南北移动和上下移动又引起局地臭氧总量的周期性变化和准两年周期振荡南北半球不对称。而臭氧浓度中心位置的准两年周期变化与赤道上空平均纬向风的准两年周期振荡密切相关。资料分析还表明，赤道上空平流层中臭氧浓度QBO的位相随高度变化多次。模拟试验表明，纬向风QBO引起垂直经圈环流的变化，在平流层有三对余差环流圈。它们对O3在不同纬度和高度的输送是引起O3准两年周期振荡的重要动力原因。其中，余差环流在平流层中层（25－35km)的环流圈起着重要的作用。     

全球平流层下部降温及其对纬向风的影响

利用NCEP/NCAR再分析资料,结合HALOE的臭氧和甲烷卫星观测资料,分析100~50 hPa的平流层下部温度变率及其与微量气体和平均纬向风的关系。结果表明,全球平流层下部大气温度自1948年至今总体呈下降趋势,而近十几年,全球平流层下部温度下降更加显著。热带和低纬甲烷的增长可能是其降温的一个重要原因。此外,由于平流层下部温度变率的经向不均匀性,同时还会引起该地区平均纬向风的变化。     

Uncertainty estimation of the global temperature trends for multiple radiosondes, reanalyses, and CMIP3/IPCC climate model simulations

Based on three groups of datasets that include radiosondes, reanalyses, and climate model simulations (e.g., Coupled Model Intercomparison Project, CMIP3) from 1979 to 2008, the interannual variability, global temperature trends, and their uncertainty using ensemble spread among intra-group and inter-group datasets have been discussed. The results show that the interannual temperature variability increased from the troposphere to stratosphere, and the maximum occurs around 50?hPa. The CMIP3 climate models have the largest discrepancy in the stratosphere. The intra-group correlations at 500?hPa generally show high similarity within each data group while the inter-group correlations between reanalyses and the CMIP3 climate model simulations indicate lesser similarity. In contrast, the inter-group correlation at 50?hPa is improved except with the Japanese 25-year Reanalysis Project (JRA-25) dataset, and the Twentieth Century Reanalysis (20CR) reanalysis shows a weak cross correlation. The global temperature trends are highly dependent on the individual data sources. Compared to the radiosondes, the reanalyses show a large ensemble spread of trends in the stratosphere, and the CMIP3 climate model simulations have a large ensemble spread in the height of the crossover point where tropospheric warming changes into stratospheric cooling. The largest ensemble spread among the reanalyses in the stratosphere is mainly from the large discrepancy in the JRA-25 reanalysis after 1998 and a relatively weak anomaly in the 20CR before 1986. The largest ensemble spread among the CMIP3 climate models in the troposphere is related to the influence of both volcanic eruptions and El Ni?o/La Ni?a–Southern Oscillation events. The strong anomalies corresponding to the volcanic eruptions of El Chichon in 1982 and Mt Pinatubo in 1991 are clearly identified in the stratosphere. These volcanic eruptions reduced the warming in the troposphere and strengthened the cooling in the stratosphere during the most recent 30?years.     

Features of ozone quasi-biennial oscillation in the vertical structure of tropics and subtropics

Summary Latitude-altitude structure of ozone QBO over the tropical-subtropical stratosphere (40° S–40° N) has been explored by analyzing Microwave Limb Sounder (MLS) aboard Upper Atmospheric Research Satellite (UARS) data for the period 1992–1999 using the multifunctional regression model. The inferred ozone QBO shows two maxima located at 22 hPa and 10 hPa with coefficient of 2–3% per 10 m/s centered at the equator. The equatorial maxima are out of phase with each other. Subtropics exhibit two peak structure near 14 hPa but of opposite sign to that of equatorial maximum near 10 hPa. Over the equatorial region, positive (zonal winds westerly) coefficients overlay negative (zonal winds easterlies) coefficients which descend with time. A pattern of equatorial maximum and two subtropical minima appears in the months December to February near 10 hpa and it propagates upward with progression of seasons. Equatorial QBO is seasonally asynchronous while subtropical QBO is seasonally synchronous. Correspondence: Suvarna Fadnavis, Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune 411008, India     

热带平流层CO浓度准两年振荡的位相变化特征

利用2005~2014年10年的卫星微波临边探测仪（MLS）资料分析了热带平流层一氧化碳（CO）体积混合比的年际变率,发现热带平流层CO浓度的准两年振荡（QBO）在30 hPa高度附近存在明显的位相变化特征。大气化学气候模式模拟结果表明,热带平流层CO的准两年振荡信号是化学和动力过程共同作用的结果,而动力作用主要是QBO引起的次级经向环流引起的物质传输。化学和动力过程共同作用导致热带平流层CO浓度的垂直梯度在30 hPa高度处发生反转,进而产生一氧化碳QBO信号的位相变化。此外,化学气候模式模拟结果还表明,与CO有关的化学过程不但可以减弱一氧化碳QBO信号的振幅,还可以在热带30~10 hPa高度范围内造成一氧化碳QBO和纬向风QBO信号之间约3个月的时间差。