Predictable patterns of the May–June rainfall anomaly over East Asia

Abstract

During early summer (May–June, MJ), East Asia (EA) subtropical front is a defining feature of Asian monsoon, which produces the most prominent precipitation band in the global subtropics. Here we show that dynamical prediction of early summer EA (20°N–45°N, 100°E–130°E) rainfall made by four coupled climate models' ensemble hindcast (1979–2010) yields only a moderate skill and cannot be used to estimate predictability. The present study uses an alternative, empirical orthogonal function (EOF)‐based physical‐empirical (P‐E) model approach to predict rainfall anomaly pattern and estimate its potential predictability. The first three leading modes are physically meaningful and can be, respectively, attributed to (a) the interaction between the anomalous western North Pacific subtropical high and underlying Indo‐Pacific warm ocean, (b) the forcing associated with North Pacific sea surface temperature (SST) anomaly, and (c) the development of equatorial central Pacific SST anomalies. A suite of P‐E models is established to forecast the first three leading principal components. All predictors are 0 month ahead of May, so the prediction here is named as a 0 month lead prediction. The cross‐validated hindcast results demonstrate that these modes may be predicted with significant temporal correlation skills (0.48–0.72). Using the predicted principal components and the corresponding EOF patterns, the total MJ rainfall anomaly was hindcasted for the period of 1979–2015. The time‐mean pattern correlation coefficient (PCC) score reaches 0.38, which is significantly higher than dynamical models' multimodel ensemble skill (0.21). The estimated potential maximum attainable PCC is around 0.65, suggesting that the dynamical prediction models may have large rooms to improve. Limitations and future work are discussed.

Predicting June Mean Rainfall in the Middle/Lower Yangtze River Basin

“…Despite the growing evidence in the literature of the potential value of considering EASM rainfall prediction on subseasonal timescales, the vast majority of predictability studies has focused only on the seasonal mean rainfall. Those that have considered subseasonal prediction (including Kim et al, 2008;Wang et al, 2009;Yim et al, 2014Yim et al, , 2016Xing et al, 2016Xing et al, , 2017Xing and Huang, 2019) have found better skill when using physical-empirical models compared with dynamical models, even with multi-model ensembles. Generally, these studies have demonstrated value in separating predictions for the early and late summer season rainfall, with greater skill at earlier lead times generally being demonstrated for the early summer (May-June).…”

Decisive Atmospheric Circulation Indices for July–August Precipitation in North China Based on Tree Models

“…Although the EASM rainy season typically extends from May to September, North China mainly receives rain during July-August, with climatological features different from those in the other East Asian regions (Xing et al 2017). Therefore, this paper focuses on the monthly rainfall in July and August.…”

Cause of Extreme Heavy and Persistent Rainfall over Yangtze River in Summer 2020

“…East Asian subtropical frontal rainfall is sensitive to the strength and location of the western Pacific subtropical high (WPSH), which is largely determined by the local atmosphere-ocean interaction (Wang et al, 2017a). Some studies have further shown that the origins and predictabilities of East Asia rainfall in early summer and late summer are obviously different (Wang et al, 2009;Xing et al, 2016Xing et al, , 2017.…”