The characteristic spatial sampling length scales (for example, in the longitudinal direction) to adequately resolve the variability associated with a quantity to be observed, depends on the typical length scales of its variability. For example, if temporal variations in the longitudinal direction are correlated over thousands of Kilometers then an observing network with a similar spatial density may be enough to sample the variability with adequate fidelity. Given the importance of surface wind stress in the equatorial tropical Pacific in determining sub-surface oceanic variability, particularly in relation to the evolution of El Niño—Southern Oscillation (ENSO), in this analysis the horizontal length scales of surface wind stress variability based on two reanalysis products—the Climate Forecast System Reanalysis and the ERA-Interim—are documented. The analysis is of relevance to the future evolution of the Tropical Pacific Observing System. As the current design of the Tropical Atmosphere Ocean [that has a wider (narrower) separation in the longitudinal (latitudinal) direction] was originally envisioned following estimates of the length scales of wind variability based on the observational record from tropical Pacific Islands (Harrison and Luther in J Clim 3:251–271, 1990), we find a similar characteristics for length scales for the surface wind variability based on reanalyses datasets. Further, the inferences based on two reanalysis products have a large degree of similarity, and thereby, give us some confidence in the reanalysis products for the purposes of analyzing the length scales of surface wind stress variability, and further, providing some basic information about the requirements for a sustained observing system in the tropical Pacific to monitor and to predict ENSO.

足以解决与待观察量有关的变异性的特征性空间采样长度标度（例如在纵向上）取决于其变异性的典型长度标度。例如，如果纵向方向的时间变化在数千公里上相关，则具有类似空间密度的观测网络可能足以以足够的保真度对变化进行采样。鉴于赤道热带太平洋中的表面风应力对于确定地下海洋的变化性（特别是与厄尔尼诺-南方涛动（ENSO）的演变有关）的重要性，在此分析中，记录了基于两种再分析产品（气候预测系统再分析和ERA-Interim）的地表风应力变化的水平长度尺度。该分析与热带太平洋观测系统的未来发展有关。由于目前的热带大气设计（在纵向（纬向）方向上具有较宽（较窄）的间隔）最初是根据热带太平洋群岛（哈里森和Luther在J Clim 3：251–271，1990）中，基于重新分析数据集，我们发现了地表风可变性长度尺度的相似特征。此外，基于两个重新分析产品的推论具有高度相似性，因此，