Causes of Interannual Variability of Summer Precipitation Intraseasonal Oscillation Intensity over Southwest China

Abstract

The interannual variability in summer precipitation intraseasonal oscillation intensity over southwest China (SWC) is investigated in this study. The results indicate that the 7–20-day period dominates the intraseasonal variability in summer SWC precipitation. The leading mode of summer SWC precipitation 7–20-day oscillation intensity (SPOI) is a north-south dipole pattern with prominent interannual variability. The atmospheric circulation anomalies from both tropics and mid-high latitudes are responsible for the interannual variability in the dipole pattern. In the tropics, an enhanced local Hadley cell and an anomalous anticyclone over southern China and the Northwest Pacific contribute to the north-positive-south-negative pattern of SPOI by inducing moisture convergence/divergence over northern/southern SWC in the background state. In the mid-high latitudes, the 7–20-day Rossby wave trains along the subtropical jet are crucial for the 7–20-day precipitation over northern SWC. Further analyses suggest that the sea surface temperature (SST) anomalies over the Maritime Continent (MC) and the North Atlantic (NA) are associated with the SPOI dipole pattern. The MC SST warming causes convection anomalies over the tropical Indo-Pacific, consequently triggering a Matsuno-Gill-type atmospheric response conducive to the north-positive-south-negative pattern of SPOI. The NA SST tripole triggers a Rossby wave train across Eurasia that strengthens the East Asian westerly jet and enhances 7–20-day atmospheric variability, consequently favoring the variability of 7–20-day precipitation over northern SWC. Diagnoses of moisture and vorticity budgets further indicate the importance of the interaction between intraseasonal fluctuations and atmospheric background in the formation of the north-south difference in 7–20-day precipitation variability over SWC.

Causes of the interdecadal transition in interannual variability of summertime intraseasonal rainfall over Southern China

“…The above factors directly lead to the stronger interannual variability of SIR over SC in P2 compared to that in P1. Many studies pointed out that the Northwest Pacific convective activities related to the WPSH intensity may be forced by SSTA over the Pacific and Indian Ocean (Xu et al, 2019;Nie and Sun, 2022). The question that needs to be discussed is: how does SSTA affect the WPSH intensity and what physical processes are involved?…”

“…SC rainfall experiences multi-scale variabilities including interdecadal variability, interannual variability, intraseasonal variability and synoptic variability (Chen et al, 2012(Chen et al, , 2015(Chen et al, , 2017Wang et al, 2017;Nie and Sun, 2022), etc. Synoptic variability of rainfall is mainly affected by synoptic scale systems.…”

Variations in the 30–60‐Day Intra‐Seasonal Variability of Spring Precipitation Over the Mid‐Low Reaches of the Yangtze River and the Possible Mechanism

“…In addition to the monthly or seasonal mean precipitation variations, the precipitation intra‐seasonal variability (ISV) has also been emphasized because the precipitation ISV is related to extreme precipitation and persistent precipitation events (Gu et al., 2021; Hsu et al., 2016; Lee et al., 2017; Nie & Sun, 2022; S. Y. Yang et al., 2013; H. Yang & Li, 2003). For example, extreme precipitation events are more likely to occur during the wet phases of the precipitation ISV cycle (e.g., Chen et al., 2005; Hsu et al., 2016; Lee et al., 2017; J. Y. Li et al., 2021; Sun et al., 2016; C. W. Zhu et al., 2003).…”

“…In addition to the monthly or seasonal mean precipitation variations, the precipitation intra-seasonal variability (ISV) has also been emphasized because the precipitation ISV is related to extreme precipitation and persistent precipitation events (Gu et al, 2021;Hsu et al, 2016;Lee et al, 2017;Nie & Sun, 2022; S. Y. Yang et al, 2013;H.…”

Characteristics and related mechanisms of the persistent extreme precipitation in August 2020 over Western China

“…Therefore, the variability in autumn precipitation in WC is a major concern for the scientific community (Gao and Guo 1958;Zhang et al, 2019;. However, under the combination of the Indian, East Asian, and Tibetan Plateau monsoons, abundant summer precipitation in WC (Zhu and Yu 2003;Wang et al, 2016;Xu et al, 2021) is prone to trigger various geological disasters, such as landslides and debris flows, which seriously affect human life and cause large economic losses (Nie and Sun 2022). A more in-depth understanding of precipitation during different seasons in WC has practical application value for improving the accuracy of climate predictions and disaster prevention.…”