On the sensitive areas for targeted observations in ENSO forecasting

Abstract Using the outputs from CMCC-CM in CMIP5 experiments, the authors identified sensitive areas for targeted observations in ENSO forecasting from the perspective of the initial error growth (IEG) method and the particle filter (PF) method. Results showed that the PF targets areas over the central-eastern equatorial Pacific, while the sensitive areas determined by the IEG method are slightly to the east of the former. Although a small part of the areas targeted by the IEG method also lie in the southeast equatorial Pacific, this does not affect the large-scale overlapping of the sensitive areas determined by these two methods in the eastern equatorial Pacific. Therefore, sensitive areas determined by the two methods are mutually supportive. When considering the uncertainty of methods for determining sensitive areas in realistic targeted observation, it is more reasonable to choose the above overlapping areas as sensitive areas for ENSO forecasting. This result provides scientific guidance for how to better determine sensitive areas for ENSO forecasting. 摘要 本研究分别从初始误差增长和粒子滤波同化的角度识别了ENSO预测的目标观测敏感区.结果表明:与粒子滤波同化方法确定的敏感区相比, 基于初始误差增长确定的敏感区位置稍微偏东, 且在东南太平洋也有分布, 但整体而言, 这两种方法确定的敏感区存在大范围重合区域, 是互为印证的.在实际目标观测中, 如果考虑使用确定敏感区方法的不确定性, 那么选择上述两种方法确定的敏感区的重合区域作为ENSO预测的目标观测敏感区将更为合理.