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1.
大气季节内振荡对印度洋—西太平洋地区热带低压/气旋生成的影响 总被引：24，自引：4，他引：24
文中利用EOF分析大气季节内振荡 (MJO)的时空变化的方法 ,研究了 1996年 9月～ 1997年 6月间的MJO活动对生成在印度洋—西太平洋海域的热带低压 /气旋的影响。结果发现 ,除西北太平洋之外 ,发生在其他区域的热带低压 /气旋有半数以上生成在向东移动的MJO的湿位相中。伴随MJO的向东传播 ,热带低压 /气旋平均生成位置也随之向东移动 ,而生成在西北太平洋的热带低压 /气旋分别受到向东和向西传播的MJO影响 相似文献
2.
The Grid-point Atmospheric Model of IAP LASG version 2 (GAMIL2) has
been developed through upgrading the deep convection parameterization, cumulus
cloud fraction and two-moment cloud microphysical scheme, as well as changing
some of the large uncertain parameters. In this paper, its performance is
evaluated, and the results suggest that there are some significant improvements
in GAMIL2 compared to the previous version GAMIL1, for example, the components
of the energy budget at the top of atmosphere (TOA) and surface; the geographic
distribution of shortwave cloud radiative forcing (SWCF); the ratio of
stratiform versus total rainfall; the response of atmospheric circulation to
the tropical ocean; and the eastward propagation and spatiotemporal structures
of the Madden Julian Oscillation (MJO). Furthermore, the indirect aerosols
effect (IAE) is -0.94 W m-2, within the range of 0 to -2 W m-2
given by the IPCC 4th Assessment Report (2007). The influence of uncertain
parameters on the MJO and radiation fluxes is also discussed. 相似文献
3.
AbstractIntervention experiments using the Coupled Forecast System model, version 2 (CFSv2), have been performed in which various Madden-Julian Oscillation (MJO) evolutions were added to the model’s internally generated heating: Slow Repeated Cycles, Slow Single Cycle, Fast Repeated Cycles, and Fast Single Cycle. In each experiment, one of these specified MJO evolutions of tropical diabatic heating was added in multiple ensemble reforecasts of boreal winter (1 November to 31 March for 31 winters: 1980–2010). Since in each experiment, multiple re-forecasts were made with the identical heating evolution added, predictable component analysis is used to identify modes with the highest signal-to-noise ratio. Traditional MJO-phase analysis of total model heating (dominated by internally generated heating) shows that the MJO-related heating structure compares well with heating estimated from observed fast and slow episodes; however, the model heating is larger by a factor of two. The evolution of Euro-Atlantic circulation regimes indicates a clear response due to the added heating, with a robust increase in the frequency of occurrence of the negative phase of the North Atlantic Oscillation (NAO?) after the heating crosses into the Pacific and a somewhat less robust increase in the positive phase of the NAO (NAO+) following Indian Ocean heating. In the Fast Cycle experiments, the model response is somewhat muted compared with the Slow Cycle experiments. The Scandinavian Blocking regime becomes more frequent prior to the NAO? regime. The two leading modes in the predictable component analysis of 300?hPa height (Z300), synoptic scale feedback (DZ300), and planetary wave diabatic heating in all experiments form an oscillatory pair with high statistical significance. The oscillatory pair represents the cyclic response to the particular MJO signal (Fast or Slow, Single, or Repeated Cycles) in each case. The period is about 64 days for the Slow Cycle and 36 days for the Fast Cycle, consistent with the imposed periods. The time series of one of the leading modes of Z300 is highly anti-correlated with the frequency of occurrence of the NAO– in the Repeated Cycle experiments. A clear cycle involving the Z300 and DZ300 leading modes is identified. 相似文献
4.
利用NCEP OLR、风场再分析资料和日本APHRO_MA_V1003R1降水资料,针对云南主汛期季节内振荡(ISO)活跃年分析了对应低频对流场、环流场和降水的异常特征,以及热带印度洋大尺度振荡MJO分别激发孟加拉湾西南季风ISO和南海热带季风ISO,从而对云南主汛期ISO和降水产生的影响.在云南主汛期ISO活跃年,低频对流场和环流场在云南ISO波动的1～3位相和4～6位相呈反位相特征,这主要由热带印度洋低频对流东传、北传和副热带西太平洋低频对流西传造成的.热带印度洋的低频对流在发展过程中,一方面沿孟加拉湾西岸向西南-东北方向传播,激发了孟加拉湾西南季风ISO活跃并继续向云南传播;另一方面沿孟加拉湾以南继续东传到南海,激发了南海热带季风ISO活跃并北传到副热带中国东部地区,再沿副热带西传至云南,越过云南后与沿孟加拉湾西岸从东北方向传来的低频对流在孟加拉湾以北地区交汇,完成了一个经纬向接力传播的周期.云南主汛期降水在1～3位相由于副热带低频对流西传和孟加拉湾低频对流东北向传播而处于正距平(第2位相降水最多);在4～6位相,由于副热带低频对流抑制区西传和孟加拉湾低频对流抑制区东北向传播而降水减少(第5位相降水最少),云南主汛期降水与当地低频对流有较好的对应关系.当热带印度洋MJO较强时,4-7月以两条路径向云南的三次传播增强和提前,使得云南主汛期ISO活动也加强,对应产生三次低频对流活跃期,这种MJO由热带印度洋向云南的传播需要30～40天的时间.因此,正是热带印度洋MJO分别对孟加拉湾西南季风ISO和南海热带季风ISO的激发,使得东亚夏季风和南亚夏季风这两个亚洲夏季风系统共同作用于云南主汛期ISO,影响当地降水. 相似文献
5.
This study addresses an understanding of the possible mutual interactions of sub-seasonal variability of the two neighboring
regional monsoon systems through data analysis. The NCEP/NCAR re-analysis and OLR data for three years was used to reveal
the large-scale organization of convective episodes on synoptic (~5 days) and low frequency (15–50 day) scales. It is found
that synoptic scale organization over both the sectors is influenced by the eastward migration of large-scale convective episodes
associated with the Madden Julian Oscillation (MJO) on the low frequency scale. The organization of convection associated
with the African monsoon on the synoptic scale is influenced by the pulsatory character of lower mid-troposphere and upper
troposphere wind regimes moving westward over the African sector. Over the Indian region formation of low pressure areas and
depressions in the monsoon trough occur in an overlapping manner under an envelope of low frequency seasonal oscillation.
We have also found some correspondence between the summer monsoon rainfall over tropical North Africa and India on a decadal
basis, which would suggest a common mode of multi-decadal variability in the two monsoon systems. The study points out the
need to organize simultaneous field campaigns over the Indian and the African monsoon regions so as to bring out observational
features of possible interactions between the two neighboring systems, which could then be validated through modeling studies. 相似文献
6.
热带大气季节内振荡研究进展——观测、动力机制和数值模拟 总被引：3，自引：0，他引：3
热带大气季节内振荡（MJO）是热带大气活动的强信号。对MJO动力机制的探讨，经历了由考虑完全的大气内部过程（波动－CISK理论），到考虑海洋影响的大气过程（WISHE理论），到最新的考虑大气－海洋耦合作用（WCMC模式）的逐步发展、完善的阶段。现阶段大气模式能够模拟MJO的一些基本特征但存在许多缺陷。在大气模式中引入上层海洋的反馈作用，可以有效改善模拟MJO的时空结构。MJO的强度变化、季节特征、传播速度等的精确描述只能借助于海气耦合模式。 相似文献
7.
基于MJO的延伸预报 总被引：30，自引：3，他引：27
近10年来,2～4周的延伸预报成为天气和气候业务预报发展的一个方向。目前比较有效的方法是根据季节内振荡的传播,尤其是MJO振荡(30～60天周期)的传播来制作延伸期预报。国际上一些天气-气候预报中通过数年的业务试验已取得了初步结果。作者首先介绍了MJO振荡及季风的季节内振荡(MISO)特征,并从季节内振荡与中纬度相互作用的角度讨论了制作延伸预报的理论依据;进一步对延伸预报的可预报性、预报方法及国内外业务应用进展进行了综述,并以江淮梅雨为例探讨了我国延伸预报的可预报性及信号;最后阐述了延伸预报的发展趋势。 相似文献
8.
热带大气季节内振荡(MJO)实时监测预测业务 总被引：8，自引：2，他引：6
参考目前国际上普遍认可的Wheeler和Hendon设计的MJO监测指标,设计了适合开展实时业务监测的MJO计算方法,初步在国家气候中心建立了逐日的MJO实时监测业务,通过与国外同类监测结果的比较分析表明,监测指标可以很好地描述MJO的强度和传播特征,与国外同类监测产品有很好的一致性。另外,引入了两种统计方法进行了针对MJO指数的实时预测,对预测结果的检验表明,对MJO在两周内有较好的预测技巧,其中利用滞后线性回归方法（PCL）的预测技巧要高于自回归模型（ARM）。 相似文献
9.
Vertical cumulus momentum transport is an important physical process in the tropical atmosphere and plays
a key role in the evolution of the tropical atmospheric system. This paper focuses on the impact of the vertical
cumulus momentum transport on Madden-Julian Oscillation (MJO) simulation in two global climate models (GCMs). The
Tiedtke cumulus parameterization scheme is applied to both GCMs [CAM2 and Spectral Atmospheric general circulation
Model of LASG/IAP (SAMIL)]. It is found that the MJO simulation
ability might be influenced by the vertical cumulus momentum transport through the cumulus parameterization scheme.
However, the use of vertical momentum transport in different models provides different results. In order to improve
model's MJO simulation ability, we must introduce vertical cumulus momentum transport in a more reasonable way into
models. Furthermore, the coherence of the parameterization and the underlying model also need to be considered. 相似文献
10.
The low frequency oscillation of latent heat flux over the tropical oceans has been studied. The NCEP reanalyzed fields of
wind and humidity alongwith Reynolds SST are used to compute the instantaneous as well as monthly mean surface latent heat
fluxes (LHF) for the year 1999. The procedure of LHF computation is based on bulk method. Spectral analysis shows that significant
energy is contained in Madden Julian Oscillation band in the winds, SST, moisture and in the latent heat flux. The global
distribution of wind, humidity, SST and LHF oscillation on the time scale of 30–50 days are analyzed. Maximum amplitude of
oscillation on this time scale in all the above mentioned parameters were found over the Indian Ocean. The fluctuation of
surface wind speed and moisture controls the latent heat flux on this time scale. The fluctuation of SST on this time scale
does not seem to be important over most of the oceans. 相似文献