Intraseasonal variability in the equatorial Atlantic-West Africa during March–June
Intraseasonal variability in the equatorial Atlantic-West Africa during March–June
复制标题
3月至6月赤道大西洋-西非的季节内变化
DOI：
10.1007/s00382-008-0428-0
复制
发表时间：
2009
期刊：
影响因子：
4.6
通讯作者：
G. Gu
中科院分区：
文献类型：
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作者：
G. Gu
使用各种最近存档的卫星测量和NCEP/DOE AMIP-II再分析每日数据，研究了3月至6月期间赤道南极-西非部门的季节内（30-80天）变化。区域季节内信号的全球连接，首先检查1979-2006年期间，通过滞后回归分析对流（OLR）和其他动力成分对区域季节内对流（OLR）指数。对流向东传播的特征很容易被看到，伴随着相干环流异常，类似于全球热带季节内模态，即，Madden-Julian振荡（MJO）TRMM期间（1998-2006年）回归的TRMM降水（3B 42）异常表现出与1979-2006年回归的OLR异常相似的传播特征。因此，这些连贯的功能往往表明，区域性的季节内对流信号可能主要是一个区域性的响应，或密切相关的MJO，并可能有助于MJO的全球传播。利用高质量的TRMM微波成像仪（TMI）的海表温度（SST），柱状水汽和云液态水，和QuikSCAT海洋风（2000-2006年），在1998-2006年3 - 6月的大气和地面季节内变化进一步研究。在季节内对流信号通过期间，对流增强（抑制）或正（负）降水异常大致覆盖整个流域（0° ~ 10 ° N，30°W ~ 10°E），并伴有地面西风（东风）气流异常。此外，一个独特的传播功能似乎存在于热带大西洋盆地。降水异常总是首先出现在南美洲海岸附近的西北盆地，然后逐渐向东延伸，覆盖整个盆地。因此，在这一演变过程中，可以观察到降水异常与越赤道地面风异常的偶极结构，类似于过去研究中发现的年际时间尺度上的异常模式。在其他物理成分中也可以发现连贯的季节内变化和模式。
Intraseasonal (30–80 days) variability in the equatorial Atlantic-West African sector during March–June is investigated using various recently-archived satellite measurements and the NCEP/DOE AMIP-II reanalysis daily data. The global connections of regional intraseasonal signals are first examined for the period of 1979–2006 through lag-regression analyses of convection (OLR) and other dynamic components against a regional intraseasonal convective (OLR) index. The eastward-propagating features of convection can readily be seen, accompanied by coherent circulation anomalies, similar to those for the global tropical intraseasonal mode, i.e., the Madden–Julian oscillation (MJO). The regressed TRMM rainfall (3B42) anomalies during the TRMM period (1998–2006) manifest similar propagating features as for the regressed OLR anomalies during 1979–2006. These coherent features hence tend to suggest that the regional intraseasonal convective signals might be mostly a regional response to, or closely associated with the MJO, and probably contribute to the MJO’s global propagation. Atmospheric and surface intraseasonal variability during March–June of 1998–2006 are further examined using the high-quality TRMM Microwave Imager (TMI) sea surface temperature (SST), columnar water vapor, and cloud liquid water, and the QuikSCAT oceanic winds (2000–2006). Enhanced (suppressed) convection or positive (negative) rainfall anomalies approximately cover the entire basin (0°–10°N, 30°W–10°E) during the passage of intraseasonal convective signals, accompanied by anomalous surface westerly (easterly) flow. Furthermore, a unique propagating feature seems to exist within the tropical Atlantic basin. Rainfall anomalies always appear first in the northwestern basin right off the coast of South America, and gradually extend eastward to cover the entire basin. A dipolar structure of rainfall anomalies with cross-equatorial surface wind anomalies can thus be observed during this evolution, similar to the anomaly patterns on the interannual time scale discovered in past studies. Coherent intraseasonal variations and patterns can also be found in other physical components.