首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Zonal mean data and amplitudes and phases of planetary zonal waves were derived from daily hemispheric maps for tropospheric and stratospheric levels, for the four winters 1975–76 to 1978–79. Important year-to-year fluctuation in zonal means and wave activity are described, most notable of which are the changes from 1975–76 to 1976–77. Comparison of the relative strengths of the stratospheric and tropospheric jet streams shows a strong negative correlation (–0.8) between monthly mean zonal stratospheric winds (at 10 mb, 65°N) and zonal tropospheric winds (at 200 mb, 32.5°N, in the jet core) and a positive correlation (+0.7) between the stratospheric 10 mb winds and the tropospheric 200 mb winds at 65°N. Parameters correlated were the departures from the climatological mean zonal winds. The structure of correlation between wave amplitudes in the same wave number (1, 2) at different altitudes and between wave numbers 1 and 2 is investigated. We find a high correlation (+0.93) between wave 1 in the stratosphere (10 mb height) and wave 2 (height) in the troposphere at 65°N; but only a weak correlation (+0.2) between wave 1 amplitudes in the stratosphere and troposphere. These results suggest the possible importance of wave-wave interactions in processes linking the stratosphere and troposphere. The wave correlations presented here are based on comparisons of monthly means of daily amplitudes; the correlation structure in individual wave developments may differ, in view of the likelihood of altitudinal lags in wave amplification.  相似文献   

2.
Continuous MF and meteor radar observations allow detailed studies of winds in the mesosphere and lower thermosphere (MLT) as well as temperatures around the mesopause. This height region is characterized by a strong variability in winter due to enhanced planetary wave activity and related stratospheric warming events, which are distinct coupling processes between lower, middle and upper atmosphere. Here the variability of mesospheric winds and temperatures is discussed in relation with major and minor stratospheric warmings as observed during winter 2005/06 in comparison with results during winter 1998/99.Our studies are based on MF radar wind measurements at Andenes (69°N, 16°E), Poker Flat (65°N, 147°W) and Juliusruh (55°N, 13°E) as well as on meteor radar observations of winds and temperatures at Resolute Bay (75°N, 95°W), Andenes (69°N, 16°E) and Kühlungsborn (54°N, 12°E). Additionally, energy dissipation rates have been estimated from spectral width measurements using a 3 MHz Doppler radar near Andenes. Particular attention is directed to the changes of winds, turbulence and the gravity wave activity in the mesosphere in relation to the planetary wave activity in the stratosphere.Observations indicate an enhancement of planetary wave 1 activity in the mesosphere at high latitudes during major stratospheric warmings. Daily mean temperatures derived from meteor decay times indicate that strong warming events are connected with a cooling of the 90 km region by about 10–20 K. The onset of these cooling processes and the reversals of the mesospheric circulation to easterly winds occur some days before the changes of the zonal circulation in the stratosphere start indicating a downward propagation of the circulation disturbances from the MLT region to the stratosphere and troposphere during the stratospheric warming events. The short-term reversal of the mesospheric winds is followed by a period of strong westerly winds connected with enhanced turbulence rates and an increase of gravity wave activity in the altitude range 70–85 km.  相似文献   

3.
Stratospheric sudden warming events in the Northern Hemisphere of the Berlin TSM GCM are investigated. In about 50% of the simulated years (13 out of 28), major midwinter warmings occur. This agrees well with observations but, whereas real events tend to occur approximately every second season, those in the model are clustered, most of them occur in the period between years 15/16 and years 24/25. In most other years, minor warming events take place. The warming events are found earlier in the winter than in reality. Many of the observed characteristics of warming events are well captured by the model: pulses of wave activity propagate out of the troposphere; these transient events force the zonal-mean zonal wind in the stratosphere and coincide with increases of the temperature at the North Pole and cooling at low levels in the tropics; temperature changes of opposite sign are modelled at higher levels. Synoptically, the modelled stratosphere evolves quite realistically before the warmings: the cyclonic vortex is displaced from the Pole by an amplifying anticyclone. After minor warmings, the stratosphere remains too disturbed as the cyclonic centre does not return to the North Pole as quickly as in reality. In the aftermath of major warmings the cyclonic vortex is not fully eroded and the anticyclonic circulation does not develop properly over the Pole; furthermore, the wintertime circulation is not properly restored after the event.  相似文献   

4.
Radar measurements at Aberystwyth (52.4°N, 4.1°W) of winds at tropospheric and lower stratospheric heights are shown for 12–13 March 1994 in a region of highly curved flow, downstream of the jet maximum. The perturbations of horizontal velocity have comparable amplitudes in the troposphere and lower stratosphere with downward and upward phase propagation, respectively, in these two height regions. The sense of rotation with increasing height in hodographs of horizontal perturbation velocity derived for hourly intervals show downwards propagation of energy in the troposphere and upward propagation in the lower stratosphere with vertical wavelengths of 1.7 to 2.3 km. The results indicate inertia-gravity waves propagating in a direction similar to that of the jet stream but at smaller velocities. Some of the features observed contrast with those of previous observations of inertia-gravity waves propagating transverse to the jet stream. The interpretation of the hodographs to derive wave parameters has taken account of the vertical shear of the background wind transverse to the direction of wave propagation.  相似文献   

5.
Quasi-biennial oscillation (QBO) is a predominant phenomenon in the tropical stratosphere and troposphere. The possible interactions between the stratospheric QBO and tropospheric biennial oscillation (TBO) over the Indian monsoon region as well as the equatorial region is investigated using the zonal wind data of 23 vertical levels (1000–1 hpa) from 1960–2002. The structure of lower stratosphere and troposphere are entirely different over the equator and India. In biennial scales, both the stratosphere and troposphere over the Indian region are closely related and winter season QBO is a good predictor of Indian summer monsoon rainfall.  相似文献   

6.
We describe a series of sensitivity experiments with a quasi-geostrophic model of the interaction of stationary planetary waves with the mean zonal flow in the stratosphere and mesosphere. The model is of the Matsuno type, which neglects wave-wave interaction and includes only a single zonal harmonic of the planetary wave spectrum in each simulation. We employed the model to investigate the source of the double-layer structure previously obtained by several authors for the stratospheric sudden warming with wavenumber one. Our results suggest that this characteristic of the model-produced warming is a property only of models without damping. When reasonable dissipation is included in the model, the double-layer structure disappears. This implies the importance of the drag parameterization in properly simulating warming events and, since the actual drag very probably is effected by breaking internal waves, it suggests that future analysis should include a specific representation of this effect. We also investigated the dependence of stratospheric warming on the structure of the zonal wind field. Our analyses show in particular that substantial reduction of the height of the polar night jet mitigates strongly against the occurrence of a sudden warming event.  相似文献   

7.
A discussion is given of atmospheric reactions in the H2O–CH4–O2–O3–NO x system. In the lower troposphere such reactions may lead to significant production of ozone. Their role in the odd hydrogen balance, especially of the troposphere and lower stratosphere, is discussed. CH3OH may be an intermediate in the oxidation cycle of methane, especially in the cold stratosphere. Its photodissociation into H2 and CH2O may consequently provide an important source for stratospheric H2. Catalytic photochemical chains of reactions involving NO x and HO x may also lead to tropospheric destruction of ozone. Due to lack of knowledge it is not possible at present to evaluate the importance of the before-mentioned reactions.With the aid of model calculations it is indicated that stratospheric ozone is most sensitive to changes in the adopted lower boundary values of N2O and that an increase in water vapour concentrations in the lower stratosphere will indeed cause some increase in ozone as predicted.Fluctuations in the flux of solar radiation near 190 nm may cause significant variations in stratospheric ozone concentrations.  相似文献   

8.
冬季太阳11年周期活动对大气环流的影响   总被引：2，自引：0，他引：2       下载免费PDF全文
刘毅  陆春晖 《地球物理学报》2010,53(6):1269-1277
利用气象场的再分析资料和太阳辐射活动资料,对太阳11年周期活动影响北半球冬季(11月~3月)大气环流的过程进行了统计分析和动力学诊断.根据赤道平流层纬向风准两年振荡(QBO)的东、西风状态对太阳活动效应进行了分类讨论,结果表明：东风态QBO时,太阳活动效应主要集中在赤道平流层中、高层和南半球平流层,强太阳活动时增强的紫外辐射加热了赤道地区的臭氧层,造成平流层低纬明显增温,同时加强了南半球的Brewer-Dobson(B-D)环流,引起南极高纬平流层温度增加;而北半球中高纬的环流主要受行星波的影响,太阳活动影响很小.西风态QBO时,太阳活动效应在北半球更为重要,初冬时强太阳活动除了加热赤道地区臭氧层外,还抑制了北半球的B-D环流,造成赤道平流层温度增加和纬向风梯度在垂直方向的变化,从而改变了对流层两支行星波波导的强度;冬末时在太阳活动调制下,行星波向极波导增强,B-D环流逐渐恢复,造成北半球极地平流层明显增温,同时伴随着赤道区域温度的下降.  相似文献   

9.
Stratospheric warmings are attributed to an enhanced planetary wave activity, occurring nearly each winter – at least in the northern hemisphere – with different strengths. The generation of stratospheric warmings is not totally understood. One of the most promising explanations is the interaction of planetary waves: in many cases, the amplitude of the quasi-stationary planetary wave 1 builds up, until it transmits its momentum and energy to the background wind field. The role of wave 2 is usually considered to be less important.Based on ERA-40 and DYANA temperature data (January–February 1990), we found evidence that a resonant wave–wave interaction between a travelling and a stationary wave 2 was responsible for a minor stratospheric warming in February 1990. The interaction being observed during four weeks can eventually be used as an indication for an upcoming stratospheric warming.  相似文献   

10.
Continuous wind observations allow detailed investigations of the upper mesosphere circulation in winter and its coupling with the lower atmosphere. During winter the mesospheric/lower thermospheric wind field is characterized by a strong variability. Causes of this behaviour are planetary wave activity and related stratospheric warming events. Reversals of the dominating eastward directed mean zonal winds in winter to summerly westward directed winds are often observed in connection with stratospheric warmings. In particular, the amplitude and duration of these wind reversals are closely related to disturbances of the dynamical regime of the upper stratosphere.The occurrence of long-period wind oscillations and wind reversals in the mesosphere and lower thermosphere in relation to planetary wave activity and circulation disturbances in the stratosphere has been studied for 12 winters covering the years 1989–2000 on the basis of MF radar wind observations at Juliusruh (55°N, since 1989) and Andenes (69°N, since 1998). Mesospheric wind oscillations with long-periods between 10 and 18 days are observed during the presence of enhanced planetary wave activity in the stratosphere and are combined with a reversal of the meridional temperature gradient of the stratosphere or with upper stratospheric warmings.  相似文献   

11.
We present time series of January–May mean mesosphere/lower thermosphere (MLT) mean winds and planetary wave (PW) proxies over Europe together with stratospheric stationary planetary waves (SPW) at 50°N and time series of European ozone laminae occurrence. The MLT winds are connected with stratospheric PW and laminae at time scales of several years to decades. There is a tendency for increased wave activity after 1990, together with more ozone laminae and stronger MLT zonal winds. However, possible coupling processes are not straightforward. While mean MLT winds before the 1990s show similar interannual variations than stratospheric PW at 100 hPa, later a tendency towards a connection of the MLT with the middle stratosphere SPW is registered. There is also a tendency for a change in the correlation between lower and middle stratosphere SPW, indicating that coupling processes involving the European middle atmosphere from the lower stratosphere to the mesopause region have changed.  相似文献   

12.
This paper attempts to establish a connection between stratospheric anomalies in the North Pole and rainfall on the Iberian Peninsula through the occurrence of major midwinter warmings (MMWs) and cold events (CEs), taking February as a preliminary approach. We define the MMWs as the warmings which break down the polar vortex, whereas the CEs are the episodes in which the polar vortex remains cold and undisturbed. Both anomalies lead to a wind anomaly around the north polar stratosphere, which is connected with a shortly lagged tropospheric anomaly through a stratosphere–troposphere coupling in winter. A T-mode principal component analysis (PCA) was used as an objective pattern classification method for identifying the main daily surface-level pressure (SLP) patterns for February for the 1961–1990 reference period. Subsequently, those February months with an MMW or a CE influence in the troposphere are identified in the whole study period (1958–2000) by means of the Arctic Oscillation Index (AOI). Thus, performing the same analysis for the selected February months, new principal patterns for detecting changes in surface circulation structure and morphology are obtained. The results show a significant decrease in the westerlies and a southward shift of the storm tracks in Western Europe some weeks after an MMW occurrence, leading to an increase in precipitation in western Iberia and a slight decrease on the eastern Mediterranean fringe. The results are quite the opposite under a CE influence: the westerlies are strengthened and shifted northwards due to the displacement of the Atlantic anticyclone towards Central Europe; dry conditions are established throughout Iberia, except for the Mediterranean fringe, where precipitation shows a considerable increase due to the greater frequency of the northeasterly winds. Finally, an 11-year sunspot cycle–quasi-biennial oscillation (QBO) modulation might be demonstrated in Iberian rainfall in February through the occurrence of these stratospheric anomalies.  相似文献   

13.
The stratosphere–mesosphere response to the major sudden stratospheric warming (SSW) in the winter of 2003/2004 has been studied. The UKMO (UK Meteorological Office) data set was used to examine the features of the large-scale thermodynamic anomalies present in the stratosphere of the Northern Hemisphere. The vertical and latitudinal structure of the genuine anomalies, emphasized by removing the UKMO climatology, has been investigated as well. The features of the stratospheric anomalies have been related to the mesospheric ones in measured neutral winds from radars and temperatures from meteor radars (90 km). It was found that the stratospheric warming spread to the lower mesosphere, while cooling occurred in the upper mesosphere, a feature that may be related to the large vertical scales of the stationary planetary waves (SPWs). It was shown also that the beginning of the eastward wind deceleration in the stratosphere–mesosphere system coincided with the maximum amplification of the SPW1 accompanied by short-lived bursts of waves 2 and 3.  相似文献   

14.
Based on the daily NCEP/DOE reanalysis II data,dates of the boreal spring Stratospheric Final Warming(SFW) events during 1979–2010 are defined as the time when the zonal-mean zonal wind at the central latitudes(65°–75°N) of the westerly polar jet drops below zero and never recovers until the subsequent autumn.It is found that the SFW events occur successively from the mid to the lower stratosphere and averagely from the mid to late April with a temporal lag of about 13 days from 10 to 50 hPa.Over the past 32 years,the earliest SFW occurs in mid March whereas the latest SFW happens in late May,showing a clear interannual variability of the time of SFW.Accompanying the SFW onset,the stratospheric circulation transits from a winter dynamical regime to a summertime state,and the maximum negative tendency of zonal wind and the strongest convergence of planetary-wave are observed.Composite results show that the early/late SFW events in boreal spring correspond to a quicker/slower transition of the stratospheric circulation,with the zonal-mean zonal wind reducing about 20/5 m s-1 at 30 hPa within 10 days around the onset date.Meanwhile,the planetary wave activities are relatively strong/weak associating with an out-of-/in-phase circumpolar circulation anomaly before and after the SFW events in the stratosphere.All these results indicate that,the earlier breakdown of the stratospheric polar vortex(SPV),as for the winter stratospheric sudden warming(SSW) events is driven mainly by wave forcing;and in contrast,the later breakdown of the SPV exhibits more characteristics of its seasonal evolution.Nevertheless,after the breakdown of SPV,the polar temperature anomalies always exhibit an out-of-phase relationship between the stratosphere and the troposphere for both the early and late SFW events,which implies an intimate stratosphere–troposphere dynamical coupling in spring.In addition,there exists a remarkable interdecadal change of the onset time of SFW in the mid 1990s.On average,the SFW onset time before the mid 1990s is 11 days earlier than that afterwards,corresponding to the increased/decreased planetary wave activities in late winter-early spring before/after the 1990s.  相似文献   

15.
  相似文献   

16.
Spänkuch  D.  Döhler  W.  Kubasch  H. 《Pure and Applied Geophysics》1973,106(1):1208-1218
Summary The correlation matrix for the vertical ozone distribution and the temperature-ozone cross-correlation matrix, which was calculated from ozone soundings made over Berlin between 1967 and 1970, the statistical structure of the vertical ozone profile (correlation coefficients, average profiles, average standard deviation, relative variability) was derived for the three ozone seasons. The partial ozone pressure does not at all heights follow a normal distribution (e. g. at tropopause level). Generally, the correlation between tropospheric and stratospheric ozone is rather poor. In some layers the highest correlation coefficients, i.e. –0.3 and +0.4, occur in autumn (October to December) and in winter and spring (January to April). The correlation between the ozone amounts of various stratospheric layers is distinct in autumn, less distinct in summer (May to September) and entirely missing from January to April. Conspicuous cross-correlations between temperature and ozone have been found for all three seasons. a) With a negative correlation between tropospheric temperature and middle tropospheric to middle stratospheric ozone (maximum up to –0.8); b) with a rather strong positive correlation between the ozone amount and the temperature in the lower stratosphere (maximum up to +0.84); c) with a positive correlation between the ozone amount of the middle stratosphere and the temperature of the middle stratosphere (maximum up to +0.8). The highest correlation coefficients occur in autumn.  相似文献   

17.
The availability of global gridded precipitation and outgoing long-wave radiation (OLR) data after 1978 makes possible an investigation of the influence of the decadal solar oscillation in the tropics during three solar maxima and two solar minima. The NCEP/NCAR reanalyses starting in the 1950s allows the inclusion of an additional two solar maxima and minima to look for consistency of response across a longer time period. In the northern summer (July–August), the major climatological tropical precipitation maxima are intensified in solar maxima compared to solar minima during the period 1979–2002. The regions of this enhanced climatological precipitation extend from the Indian monsoon to the West Pacific oceanic warm pool and farther eastwards in the Intertropical Convergence Zone of the North Pacific and North American Monsoon, to the tropical Atlantic and greater rainfall over the Sahel and central Africa. The differences between solar maxima and minima in the zonal mean temperature through the depth of the troposphere, OLR, tropospheric vertical motion, and tropopause temperature are consistent with the differences in the rainfall. The upward vertical motion is stronger in regions of enhanced tropical precipitation, tropospheric temperatures are higher, tropopause temperatures are lower, and the OLR is reduced due to higher, colder cloud tops over the areas of deeper convective rainfall in the solar maxima than in the minima. These differences between the extremes of the solar cycle suggest that an increase in solar forcing intensifies the Hadley and Walker circulations, with greater solar forcing resulting in strengthened regional climatological tropical precipitation regimes. These effects are as strong or even more pronounced when warm and cold extremes in the Southern Oscillation are removed from the analyses. Additionally, lower stratospheric temperatures and geopotential heights are higher with greater solar forcing suggesting ozone interactions with solar forcing in the upper stratosphere.  相似文献   

18.
Stratospheric warming effects on the tropical mesospheric temperature field   总被引：1，自引：0，他引：1  
Temperature observations at 20–90 km height and 5–15°N during the winter of 1992–1993, 1993–1994 and 2003–2004, from the Wind Imaging Interferometer (WINDII) and Microwave Limb Sounder (MLS) experiments on the Upper Atmosphere Research Satellite (UARS) satellite and the Sounding the Atmosphere using Broadband Emission Radiometry (SABER) experiment on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite are analyzed together with MF radar winds and UK Meteorological Office (UKMO) assimilated fields. Mesospheric cooling is observed at the time of stratospheric warming at the tropics correlative with stratospheric warming events at middle and high latitudes. Planetary waves m=1 with periods of 4–5, 6–8, 10 and 12–18 days are found to dominate the period. Westward 7- and 16-day waves at the tropics appear enhanced by stationary planetary waves during sudden stratospheric warming events.  相似文献   

19.
The temporal variations in mean zonal wind, horizontal temperature gradient at 30 mb and Total Ozone in Antarctic Spring (1 Sept.–30 Nov.) for nine seasons (1979–1987) were examined. The ozone hole filling commenced when the zonal flow decelerated to 50–58 m.sec–1 at 30 mb. Our calculation of Rossby critical wave number with vertical shear suited for Antarctic Spring indicated that flow is preconditioned for vertical propagation of Rossby critical wave number two at this range of zonal flow. This preconditioning can be attributed to the diabatic heating in the Antarctic Spring since no sudden minor warmings/coolings have occurred during the period.  相似文献   

20.
The coupling of the neutral atmosphere and the ionosphere through planetary waves (PW) (zonal wavenumber 0–5) is investigated by spherical harmonic analyses of the ionospheric total electron content (TEC). These analyses detect mean variations, standing and travelling waves which are assumed to be signatures of PW. Database used for TEC analyses are 3 years of hourly TEC maps covering the higher middle and polar latitudes. They are regularly produced by DLR Neustrelitz. The obtained results are compared with PW analyses using NCEP/NCAR and Met Office stratospheric reanalyses. Case studies show that signatures of PW occur simultaneously in the middle atmosphere and ionosphere.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号