Application of Clustering Algorithms to TRMM Precipitation over the Tropical and South Pacific Ocean
Application of Clustering Algorithms to TRMM Precipitation over the Tropical and South Pacific Ocean
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DOI：
10.1175/jcli-d-19-0537.1
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发表时间：
2020-06
影响因子：
4.9
通讯作者：
M. Pike;B. Lintner
中科院分区：
文献类型：
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作者：
M. Pike;B. Lintner
了解南太平洋辐合带（SPCZ），东南方向的带降水深对流在南太平洋的多尺度降雨变率，是至关重要的人类和自然系统依赖于它的降雨，并解释类似的离赤道对角对流区周围的地球仪。一个k-均值聚类方法应用于每日南方夏季（12月至2月）热带降雨测量使命（TRMM）卫星降雨量，以提取1998年至2013年期间的SPCZ区域降雨的代表性空间格局。对于k = 4的聚类，成对的聚类主要通过SPCZ对角线的空间平移而不同，反映了厄尔尼诺-南方涛动（ENSO）的暖相或冷相。在每个ENSO相位对中，一个集群沿着SPCZ表现出强降水，而另一个集群则表现出弱降水。分析簇的时间行为以研究更高频率的强迫（例如，Madden-Julian振荡和天气尺度扰动），在SST足够温暖的地方触发深对流。压力级风和比湿度从气候预报系统再分析合成相对于每日集群分配，以调查活动和静止SPCZ条件之间的差异，以揭示支持增强或抑制SPCZ降水的条件，如低层极地从赤道的水汽输送。TRMM降水的经验正交函数（EOFs）的计算与“模态视图”的SPCZ变异与EOFs的“状态视图”与集群相关联。最后，随着允许额外的自由度，集群数量增加，以说明TRMM降雨模式的变化。
Understanding multiscale rainfall variability in the South Pacific convergence zone (SPCZ), a southeastward-oriented band of precipitating deep convection in the South Pacific, is critical for both the human and natural systems dependent on its rainfall, and for interpreting similar off-equatorial diagonal convection zones around the globe. A k-means clustering method is applied to daily austral summer (December–February) Tropical Rainfall Measuring Mission (TRMM) satellite rainfall to extract representative spatial patterns of rainfall over the SPCZ region for the period 1998–2013. For a k = 4 clustering, pairs of clusters differ predominantly via spatial translation of the SPCZ diagonal, reflecting either warm or cool phases of El Niño–Southern Oscillation (ENSO). Within each of these ENSO phase pairs, one cluster exhibits intense precipitation along the SPCZ while the other features weakened rainfall. Cluster temporal behavior is analyzed to investigate higher-frequency forcings (e.g., the Madden–Julian oscillation and synoptic-scale disturbances) that trigger deep convection where SSTs are sufficiently warm. Pressure-level winds and specific humidity from the Climate Forecast System Reanalysis are composited with respect to daily cluster assignment to investigate differences between active and quiescent SPCZ conditions to reveal the conditions supporting enhanced or suppressed SPCZ precipitation, such as low-level poleward moisture transport from the equator. Empirical orthogonal functions (EOFs) of TRMM precipitation are computed to relate the “modal view” of SPCZ variability associated with the EOFs to the “state view” associated with the clusters. Finally, the cluster number is increased to illustrate the change in TRMM rainfall patterns as additional degrees of freedom are permitted.