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1.
The influence of El Nio-Southern Oscillation (ENSO) on the convectively coupled Kelvin waves over the tropical Pacific is investigated by comparing the Kelvin wave activity in the eastern Pacific (EP) El Nio, central Pacific (CP) El Nio, and La Nia years, respectively, to 30-yr (1982-2011) mean statistics. The convectively coupled Kelvin waves in this study are represented by the two leading modes of empirical orthogonal function (EOF) of 2-25-day band-pass filtered daily outgoing longwave radiation (OLR), with the estimated zonal wavenumber of 3 or 4, period of 8 days, and eastward propagating speed of 17 ms-1 . The most significant impact of ENSO on the Kelvin wave activity is the intensification of the Kelvin waves during the EP El Nios. The impact of La Nia on the reduction of the Kelvin wave intensity is relatively weaker, reflecting the nonlinearity of tropical deep convection and the associated Kelvin waves in response to ENSO sea surface temperature (SST) anomalies. The impact of the CP El Nio on the Kelvin waves is less significant due to relatively weaker SST anomalies and smaller spatial coverage. ENSO may also alter the frequency, wavelength, and phase speed of the Kelvin waves. This study demonstrates that low-frequency ENSO SST anomalies modulate high-frequency tropical disturbances, an example of weather-climate linkage. 相似文献
2.
Scale analyses for long wave, zonal ultralong wave (with zonal scale of disturbance L1~104 km and meridional scale L2~103 km) and meridional ultralong wave (L1~103 km, L2~104 km) are carried out and a set of approximate equations suitable for the study of these waves in a dry tropical atmosphere is obtained. Under the condition of sheared basic current, frequency analyses for the equations are carried out. It is found that Rossby waves and gravity waves may be separated for n ≥ l where n is the meridional wave number, whereas for n = 0 and L1~1000 km, the mixed Rossby-gravity wave will appear. Hence it is confirmed that the above results of scale analyses are correct. The consistency be-tween frequency analysis and scale analysis is established.The effect of shear of basic current on the equatorial waves is to change their frequencies and phase velocities and hence their group velocities. It increases the velocity of westward travelling Rossby waves and inertia-gravity and mixed waves, but decelerates the eastward inertia-gravity waves and the Kelvin wave. The recently observed low-frequency equatorial ocean wave may be interpreted as an eastward Kelvin wave in a basic current with shear. 相似文献
3.
Warm and cold phases of El Nino–Southern Oscillation (ENSO) exhibit a significant asymmetry in their decay speed. To explore the physical mechanism responsible for this asymmetric decay speed, the asymmetric features of anomalous sea surface temperature (SST) and atmospheric circulation over the tropical Western Pacific (WP) in El Nino and La Nina mature-to-decay phases are analyzed. It is found that the interannual standard deviations of outgoing longwave radiation and 850 hPa zonal wind anomalies over the equatorial WP during El Nino (La Nina) mature-to-decay phases are much stronger (weaker) than the intraseasonal standard deviations. It seems that the weakened (enhanced) intraseasonal oscillation during El Nino (La Nina) tends to favor a stronger (weaker) interannual variation of the atmospheric wind, resulting in asymmetric equatorial WP zonal wind anomalies in El Nino and La Nina decay phases. Numerical experiments demonstrate that such asymmetric zonal wind stress anomalies during El Nino and La Nina decay phases can lead to an asymmetric decay speed of SST anomalies in the central-eastern equatorial Pacific through stimulating di erent equatorial Kelvin waves. The largest negative anomaly over the Nino3 region caused by the zonal wind stress anomalies during El Nino can be threefold greater than the positive Nino3 SSTA anomalies during La Nina, indicating that the stronger zonal wind stress anomalies over the equatorial WP play an important role in the faster decay speed during El Nino. 相似文献
4.
YAN Bangliang 《大气科学进展》2005,22(5):741-750
The mechanism of the locking of the E1 Nino event onset phase to boreal spring （from April to June） in an intermediate coupled ocean-atmosphere model is investigated. The results show that the seasonal variation of the zonal wind anomaly over the equatorial Pacific associated with the seasonal variation of the ITCZ is the mechanism of the locking in the model. From January to March of the E1 Nino year, the western wind anomaly over the western equatorial Pacific can excite the downwelling Kelvin wave that propagates eastward to the eastern and middle Pacific by April to June. From April to December of the year before the E1 Nifio year, the eastern wind anomaly over the equatorial Pacific forces the downwelling Rossby waves that modulate the ENSO cycle. The modulation and the reflection at the western boundary modulate the time of the transition from the cool to the warm phase to September of the year before the E1 Nifio year and cause the strongest downwelling Kelvin wave from the reflected Rossby waves at the western boundary to arrive in the middle and eastern equatorial Pacific by April to June of the E1 Nino year. The superposition of these two kinds of downwelling Kelvin waves causes the El Nino event to tend to occur from April to June. 相似文献
5.
Recent advances in studies of the interaction between the East Asian winter and summer monsoons and ENSO cycle 总被引：26，自引：5，他引：21
Recent advances in studies on the interaction between the East Asian monsoon and the ENSO cycle are reviewed in this paper. Through the recent studies, not only have the responding features and processes of the East Asian winter and summer monsoon circulation anomalies and summer rainfall anomalies in East Asia to the ENSO cycle during its different stages been understood further, but also have the thermal and dynamic effects of the tropical western Pacific on the ENSO cycle been deeply analyzed from the observational facts and dynamic theories. The results of observational and theoretical studies showed that the dynamical effect of the atmospheric circulation and zonal wind anomalies in the lower troposphere over the tropical western Pacific on the ENSO cycle may be through the excitation of the equatorial oceanic Kelvin wave and Rossby waves in the equatorial Pacific. These studies demonstrated further that the ENSO cycle originates from the tropical western Pacific. Moreover, these recent studies also showed that the atmospheric circulation and zonal wind anomalies over the tropical western Pacific not only result from the air-sea interaction over the tropical western Pacific, but are also greatly influenced by the East Asian winter and summer monsoons. Additionally, the scientific problems in the interaction between the Asian monsoon and the ENSO cycle which should be studied further in the near future are also pointed out in this paper. 相似文献
6.
A Theoretical Explanation of Anomalous Atmospheric Circulation Associated with ENSO Modoki during Boreal Winter 
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下载免费PDF全文 Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events. 相似文献
7.
The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model performance in simulating the convectively coupled equatorial waves(CCEWs) by comparing the daily output of precipitation from a 23-yr coupled run with the observational precipitation data from Global Precipitation Climatology Project(GPCP). Four dominant modes of CCEWs including the Kelvin, equatorial Rossby(ER), mixed Rossby–gravity(MRG), tropical depression-type(TD-type) waves, and their annual mean and seasonal cycle characteristics are investigated respectively. It is found that the space–time spectrum characteristics of each wave mode represented by tropical averaged precipitation could be very well simulated by CAMS-CSM, including the magnitudes and the equivalent depths. The zonal distribution of wave associated precipitation is also well simulated, with the maximum centers over the Indian Ocean and the Pacific Ocean. However, the meridional distribution of the wave activities is poorly simulated, with the maximum centers shifted from the Northern Hemisphere to the Southern Hemisphere, especially the Kelvin, MRG, and TD waves. The seasonal cycle of each wave mode is generally captured by the model, but their amplitudes over the Southern Hemisphere during boreal winter are grossly overestimated. The reason for the excessive wave activity over the southern Pacific Ocean in the simulation is discussed. 相似文献
8.
Based on the aqua-planet experiments, the wavenumber-frequency characteristics of tropical waves and their influencing factors in SST distribution and the convective parameterization scheme are investigated using the spectral atmospheric general circulation model （SAMIL）. Space-time spectral analysis is used to obtain the variance of convectively coupled tropical waves. In the Control experiment with maximum SST located at the equator the simulated tropical-wave behaviors are in agreement with those in observations and theoretical solutions. When the maximum SST is located at 5°N, the symmetric and antisymmetric waves are much weaker than those in the control experiment, suggesting that tropical wave activities are very sensitive to the SST distributions. Importantly, the variance maximum of Madden-Julian oscillation （MJO） is found to occur around 5°N, which suggests that the development of the MJO depends largely on the latitude of maximum SST. Furthermore, the seasonal variations of MJO may be mainly caused by the seasonal variations of the maximum SST. The experiment results with two different cumulus schemes the Manabe moist convective adjustment and Zhang-McFarlane （ZM） convective scheme, were also compared to examine the impacts of convective parameterization. Weakened variances of each individual tropical wave when the ZM scheme is used suggest that the ZM scheme is not favorable for the tropical wave activities. However, the wave characteristics are different when the ZM scheme is used in different models, which may imply that the simulated basic state is important to the meridional distributions of the waves. The MJO signals suggest that the parameterization scheme may have great influence on the strength, but have less direct impact on the MJO distribution. The frequency of the tropical waves may be associated with the moisture control of convection and the large-scale condensation scheme used in the model. 相似文献
9.
ZONG Haifeng 《大气科学进展》2014,31(6):1395-1406
The physical processes involved in the formation of the ENSO cycle,as well as the possible roles of the Hadley circulation （HC）,Walker circulation （WC）,and the propagating waves of the Southern Oscillation/Northern Oscillation （SO/NO） in its formation,were studied using composite and regression methods.The analysis showed that the convection and heat release triggered by ENSO in the central-eastern equatorial Pacific are the primary drivers for the 3-5 year cycle of the HC,WC and the meridional/zonal circulation.The HC plays a key role in the influence of ENSO on the circulation outside the tropics through angular momentum transportation.Meanwhile,the feedback effects of the anomalous circulation in the mid-high latitudes on ENSO are accomplished by the propagating waves of SO/NO associated with the evolutions of HC and WC.These propagating waves are the main agents of the connections among the meridional/zonal circulation outside the tropics,the Asian/Australian monsoon,the anomalous easterly/westerly winds over the tropical Pacific,and ENSO events.It was found that the 3-5 year cycle of the meridional/zonal circulation forced by ENSO is quite different from the several-week variation of the circulation index triggered by the inner dynamic processes of the atmosphere.The former occurs at the global scale with a definite flow pattern,while the latter occurs only in a wide area without a definite flow pattern.Finally,a physical model for the formation of the ENSO cycle composed of two fundamental processes at the basin and global scale,respectively,is proposed. 相似文献
10.
One-dimensional retrieval was performed on Typhoon Haiyan utilizing the advanced technology microwave sounder onboard the satellite Suomi NPP to retrieve the temperature and water vapor profiles of the typhoon. Comparisons of the retrieved profiles and ECMWF reanalysis were made to assess the results. The main conclusions are as follows. (1) The results have high spatial resolution and therefore can precisely represent the temperature and humidity distribution of the typhoon. (2) The retrieved temperature is low in the areas of low temperature and high in the areas of high temperature; similar patterns are observed for humidity. This means that systematic revision may be needed during routine application. (3) The results of the retrieved temperature and humidity profiles are generally accurate, which is quite important for typhoon monitoring. 相似文献
11.
GPS radio occultation(GPS RO) method,an active satellite-to-satellite remote sensing technique,is capable of producing accurate,all-weather,round the clock,global refractive index,density,pressure,and temperature profiles of the troposphere and stratosphere.This study presents planetary-scale equatorially trapped Kelvin waves in temperature profiles retrieved using COSMIC(Constellation Observing System for Meteorology,Ionosphere,and Climate) satellites during 2006-2009 and their interactions with background atmospheric conditions.It is found that the Kelvin waves are not only associated with wave periods of higher than 10 days(slow Kelvin waves) with higher zonal wave numbers(either 1 or 2),but also possessing downward phase progression,giving evidence that the source regions of them are located at lower altitudes.A thorough verification of outgoing longwave radiation(OLR) reveals that deep convection activity has developed regularly over the Indonesian region,suggesting that the Kelvin waves are driven by the convective activity.The derived Kelvin waves show enhanced(diminished) tendencies during westward(eastward) phase of the quasi-biennial oscillation(QBO) in zonal winds,implying a mutual relation between both of them.The El Nino and Southern Oscillation(ENSO) below 18 km and the QBO features between 18 and 27km in temperature profiles are observed during May 2006-May 2010 with the help of an adaptive data analysis technique known as Hilbert Huang Transform(HHT).Further,temperature anomalies computed using COSMIC retrieved temperatures are critically evaluated during different phases of ENSO,which has revealed interesting results and are discussed in light of available literature. 相似文献
12.
13.
Summary ?The fields of sea-level height anomaly (SLHA) and surface zonal wind anomaly (SZWA) have been analyzed to investigate the
typical evolution of spatial patterns during El Ni?o-Southern Oscillation (ENSO) events. Sea surface temperature (SST) changes
during ENSO events are represented as an irregular interplay of two dominant modes, low-frequency mode and biennial mode.
Cyclostationary principal component (PC) time series of the former variables are regressed onto the PC time series of the
two dominant SSTA modes to find the spatial patterns of SLHA and SZWA consistent with the two SSTA modes. The two regressed
patterns of SLHA explain a large portion of SLHA total variability. The reconstruction of SLHA using only the two components
reasonably depicts major ENSO events. Although the low-frequency component of SST variability is much larger than the biennial
component, the former does not induce strong Kelvin and Rossby waves. The biennial mode induces much stronger dynamical ocean
response than the low-frequency mode.
Further decomposition of the SLHA modes into Kelvin and Rossby components shows how these two types of equatorial waves evolve
during typical ENSO events. The propagation and reflection of these waves are clearly portrayed in the regressed patterns
leading to a better understanding of the wave mechanism in the tropical Pacific associated with ENSO. A close examination
suggests that the delayed action oscillator hypothesis is generally consistent with the analysis results reported here. Rossby
wave development in the central Pacific in the initiation stage of ENSO and the subsequent reflection of Kelvin waves at the
western boundary seems to be an important mechanism for further development of ENSO. The development of Kelvin waves forced
by the surface wind in the far-western Pacific cannot be ruled out as a possible mechanism for the growth of ENSO. While Kelvin
waves in the far-western Pacific serve as an intiation mechanism of ENSO, they also cause the termination of existing ENSO
condition in the central and eastern Pacific, thereby leading to a biennial oscillation over the tropical Pacific. The Kelvin
waves from the western Pacific erode the thermocline structure in the central Pacific preventing further devlopment of ENSO
and ultimately terminating it. It should be emphasized that this wave mechanism is clear and active only in the biennial mode.
Received August 15, 2001; revised March 6, 2002 相似文献
14.
COSMIC是一个由6颗低轨卫星组成的用于天气、气候和电离层观测的空基GPS星座观测系统, 从2006年9月开始每天可提供覆盖全球的约2000~3000个掩星点, 掩星过程可提供从40 km高空到近地面的大气温、压、湿的廓线资料。为了有效利用这些资料, 以探空资料为基准, 对2007年1-10月我国及邻近区域的COSMIC掩星资料进行精度、可用性和全天候性的检验。结果表明: COSMIC反演的温度和折射率的精度很高, 水汽压的精度相对较差。与NCEP/NCAR再分析资料相比, 折射率和湿度廓线有更高精度。 相似文献
15.
This study investigates the spatial and temporal variability of global stratospheric gravity waves (GWs) and the characteristics of GW activity during sudden stratospheric warming (SSW) using the GPS radio occultation measurements from the COSMIC mission during September 2006 to May 2013. Corresponding to the COSMIC RO observational window and analysis method, GW potential energy (Ep) with vertical scales no shorter than ～2 km is resolved. It is found that the distributions of GW Ep over 20-30 km and 30-38 km show similar spatial and seasonal variations. The variations of GW Ep with altitude and latitude along the westerly wind are identified in different seasons over 60°-80°W. In the middle and high latitudes, seasonal cycles are distinct in the time-latitude and time-altitude distributions of GW activities, which show larger Ep in winters when westerly wind dominates and smaller Ep in summers when easterly wind dominates. The influence of quasi-biennial oscillation on GW activity is recognized in the tropics. GW Ep enhances closely following the occurrence of minor SSW events; while during major events, GW Ep may not enhance, and sometimes may even weaken, in the regions where reversals of zonal wind occur, probably caused by the filtering impact of the 0 m s-1 wind level on the GWs. 相似文献
16.
In recent years, radio occultation (RO) technology making
use of global positioning system (GPS) signals has been exploited to
obtain profiles of atmospheric parameters in the neutral atmosphere.
In this paper, the RO refractivity profiles obtained from the
Constellation Observing System for Meteorology, Ionosphere and
Climate (COSMIC) mission are statistically compared with the
observations of 38 radiosonde stations provided by the Australian
Bureau of Meteorology during the period from 15 July 2006 through 15
July 2007. Different collocation criteria are compared at first, and
COSMIC RO soundings that occur within 3 hours and 300 km of
radiosonde measurements are used for the final statistical
comparison. The overall results show that the agreements between the
COSMIC refractivity profiles and the radiosonde soundings from the
38 stations are very good at 0--30 km altitude, with mean absolute
relative refractivity deviations of less than 0.5%. Latitudinal
comparisons indicate that there are negative refractivity deviations
in the lower troposphere over the low latitude and middle latitude
regions and large standard deviations exist in the lower troposphere
of low latitude regions, which can reach up to ~6%. The
comparisons of COSMIC RO refractivity profiles and radiosonde
observations for 3 polar stations in four different seasons indicate
that the accuracy of GPS RO profiles is better in the Austral summer
and autumn than in the Austral spring and winter during the year
from September 2006 to August 2007. 相似文献
17.
18.
热带平流层多尺度波动分离方案的研究：多站点高分辨率无线电探空联合分析 总被引：1，自引：0，他引：1
利用太平洋地区台风过境期间6个热带气象站的高分辨率无线电探空资料,结合扩展经验正交函数（EEOF）展开,对热带下平流层行星波和重力波扰动进行了分离,给出了一种热带地区提取重力波扰动的新方案。对观测数据做EEOF展开后,选择表征行星尺度波动模态的特征向量和相应权重进行气象要素场的重建。结果显示,在不同的台风过程期间,温度、纬向风和经向风的重建扰动量显示出不同的动力学偏振关系:在准两年振荡（QBO）东风位相时与赤道开尔文波的偏振关系一致,而在准两年振荡西风位相时与混合罗斯贝-重力波（MRG）的偏振关系一致。把行星尺度波动模态从原始观测中剔除,得到新的扰动廓线,对其进行重力波垂直波数谱的谱型拟合。结果发现,与以往方法提取的重力波扰动相比,新方法所得谱型参数中特征垂直波长λ*在不同时期不同站点变化很小,稳定在1.7 km左右,且低频波数段谱斜率s的数值与理论假设1十分接近。综合其研究结果可以推测,用新方法提取的热带重力波扰动更加符合当前的理论垂直波数谱模型。 相似文献