Abstract

In addition to the tropical data, the OLR/U850/U200 data on a restricted region in southwestern Asia (17.5^°N-35^°N, 30°E-60°E) has been incorporated into the calculation of the Real-time Multivariate MJO (RMM) index. Introducing this data modifies the leading EOFs of the RMM index slightly and rotates them 14^° eastward as a consequence of the change in the column variances of the RMM anomaly matrix at 30°E-60°E longitudes. However, the leading principal components of the new index, which is called Regionally Modified RMM (hereafter, RM-RMM), remain approximately unchanged. Owing to this close relationship between the two indices, the 14^° phase-shift is considered as a basis for comparing the influences of the intraseasonal tropics-southwestern Asia variabilities on the precipitation over Iran with those of the MJO. Accordingly, by generating the spatial patterns of the precipitation anomaly, precipitation occurrence probability and other fields based on every active phase of the RM-RMM and RMM indices, the significant differences are revealed between the corresponding phases of the two indices for the phases 1, 3, 5, 7, and 8, separately. These results ameliorate the estimation of the impacts of the MJO on the precipitation and indicate that the RM-RMM index could be used as a companion to the RMM to forecast the precipitation in Iran. Remarkably, the precipitation forecast skill of the lag-regression model based on the RM-RMM index exceeds that of the model based on the RMM for certain time lags during the phases 1, 3, 5, 7 and 8 of the two indices.

中文翻译：

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实时多元MJO指数的类比，以改进对北方寒冷月份MJO对伊朗降水变化的影响的估计

摘要

除了热带数据外，亚洲西南部一个限制区域（17.5 ^° N-35 ^° N，30°E-60°E）的OLR / U850 / U200数据也已纳入实时多元分析中MJO（RMM）索引。引入此数据会稍微修改RMM索引的前导EOF，并将其向东旋转14 ^°，这是由于RMM异常矩阵在30°E-60°E经度上的列方差变化所致。但是，新索引的主要主要成分（称为区域修改的RMM（以下简称RM-RMM））大致保持不变。由于两个指数之间的这种紧密关系，因此14 ^°相移被认为是比较季节内热带地区-西南亚变率对伊朗和MJO降水的影响的基础。因此，通过基于RM-RMM和RMM指标的每个活动相位生成降水异常，降水发生概率和其他场的空间分布图，就可以发现两个指标在相对应的两个相位之间的显着差异：分别是3、5、7和8。这些结果改善了MJO对降水的影响的估计，并表明RM-RMM指数可以作为RMM的伴侣来预测伊朗的降水。值得注意的是