Summertime Moisture Sources and Transportation Pathways for China and Associated Atmospheric Circulation Patterns

Zhiyan Zuo,QuCheng Chu,Ruonan Zhang,Yanjun Qi

doi:10.3389/feart.2021.756943

Abstract

Based on the Lagrangian particle dispersion model, HYSPLIT 4.9, this study analyzed the summertime atmospheric moisture sources and transportation pathways affecting six subregions across China. The sources were: Midlatitude Westerly (MLW), Siberian-Arctic regions (SibArc), Okhotsk Sea (OKS), Indian Ocean (IO), South China Sea (SCS), Pacific Ocean (PO), and China Mainland (CN). Furthermore, the relative contributions of these seven moisture sources to summertime precipitation in China were quantitatively assessed. Results showed that the CN precipitation source dominates the interannual and interdecadal variation of precipitation in most subregions, except Southwest and South China. The Northeast China vortex and Pacific–Japan (PJ) teleconnection, which transport water vapor from the MLW, OKS and PO sources, are crucial atmospheric systems and patterns for the variation of precipitation in Northeast China. The interannual variation of precipitation in Northwest and North China is mainly dominated by mid–high-latitude Eurasian wave trains, which provide the necessary dynamical conditions and associated moisture transport from the MLW and SibArc sources. In addition, an enhanced western North Pacific subtropical high (WNPSH) accompanied by the East Asian–western North Pacific summer monsoon and PJ teleconnection, transports extra moisture to North China from the SCS and PO sources, as well to the Yangtze River Valley and South China. The Indian summer monsoon (ISM) is also critically important for the interdecadal change in precipitation over the Yangtze River Valley and South China, via the southwesterly branch of moisture transport from the IO source. The interdecadal changes in precipitation over Southwest China are determined by the IO and SCS sources, via enhanced WNPSH coupling with a weakened ISM. These results suggest that the interdecadal and interannual variations of moisture sources contribute to the attendant variation of summertime precipitation in China via large-scale circulation regimes in both the mid–high and lower latitudes.

Highlights

Interannual and interdecadal variations of summer precipitation over China are fundamentally controlled by water vapor transport (Zhou and Yu, 2005; Zhao et al, 2007; Sun and Wang, 2011; Zhu et al, 2011), dynamically associated with large-scale atmospheric circulation in both the lower and mid–high latitudes
Most air parcels arriving in the three northern subregions (i.e., Northwest, North and Northeast China) originate from the China Mainland (CN), Midlatitude Westerly (MLW), Siberian-Arctic regions (SibArc) and Okhotsk Sea (OKS) sources, whereas air parcels that arrive in the southern subregions (i.e., Southwest, South and Southeast China) are governed predominantly by the tropical ocean and CN sources
The precipitation of the SibArc and OKS sources contributes little to summertime precipitation over the whole of China, and the target region is spatially confined to Northwest and Northeast China, which is located in the vicinity of the source origins (Figures 1B,C)

Summary

Introduction

Interannual and interdecadal variations of summer precipitation over China are fundamentally controlled by water vapor transport (Zhou and Yu, 2005; Zhao et al, 2007; Sun and Wang, 2011; Zhu et al, 2011), dynamically associated with large-scale atmospheric circulation in both the lower and mid–high latitudes. In high-latitude regions, Arctic sea-ice loss and the North Atlantic Oscillation have additional influence on the moisture transport over Northwest China (Liu et al, 2012; Li and Wang, 2013; Zhang and Zhou, 2015; Hua et al, 2017) and North China (Zhang et al, 2018) through large-scale Eurasian wave trains. Besides these large-scale atmospheric regimes, local evapotranspiration is another crucial source of atmospheric moisture, which accounts for approximately 9.6% of total rainfall as estimated by the global annual mean recycling (Trenberth, 1999). Past studies have identified various moisture sources of regional precipitation, they do not provide a complete picture of affecting factors in both the lower and mid–high latitudes

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Conclusion