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<p>Drought events in China are becoming more frequent in the context of global warming. The scope and harm of drought are more prominent, especially for ecologically fragile areas such as micro mountainous areas. Standardized Precipitation Evapotranspiration Index (SPEI) is used to characterize the dry-wet conditions (including the drought frequency and intensity) of the climate. And spatiotemporal characteristics and its circulation background in Northeast Sichuan over the past 60 years are analyzed based on trend test, correlation test and abnormal circulation during drought. The main results showed that: (1) The SPEI of various time scales in the northeastern Sichuan region is stable but in August 1997 and August 2006, extreme drought occurred. The oscillation period duration of SPEI at the annual scale is about 6.5 years. From 1961 to 1990, it showed a pattern of turning from dry in the north to wet in the south, while it showed a pattern of turning from wetness in the north to dryness in the south from 1991 to 2020. The dryness and wetness transition varies in different seasons. SPEI shows an increasing trend in summer (concentrated in the southeast, with the highest growth rate reaching 0.224 per decade), while SPEI shows a decreasing trend in winter (−&#xa0;0.120 per decade ). (2) The frequency of extreme drought in the northern mountainous areas of northeastern Sichuan is relatively high, and the spatial distribution of drought is uneven in different seasons. Among them, the areas with the most severe summer drought are Pingchang and Wanyuan. The first mode of EOF shows quasi-consistent dry-wet change type and the second mode shows northwest-southeast oscillation change type. (3) The northwest-southeast oscillation change type in the region is mainly influenced by SOI (in April, July, and November) and PDO (in summer and autumn). When SOI is high (low), it shows that the southeast is relatively dry (wet), and when PDO is high (low), it shows that the southeast is relatively wet (dry). In addition, the more northward and westward the position of WPSH in July and August, the drier the area becomes (<i>p</i> &lt; 0.01). Furthermore, it is not necessarily the stronger EASMI, the wetter the summer in northeastern Sichuan. On the contrary, it may become drier. The abnormal summer drought in the region may be caused by the abnormal moisture transport in the southwest monsoon and the sinking airflow with the abnormal potential height.</p>

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The dry-wet changes and the correlation with atmospheric circulation in Northeast Sichuan, Western China

  • 期刊论文

  • 发表日期：

    2025年12月31日

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  • Zhaoqi Yin,
  • Weipeng Li,
  • Zhongsheng Chen,
  • Panheng Shui,
  • Li Zhu

摘要

Drought events in China are becoming more frequent in the context of global warming. The scope and harm of drought are more prominent, especially for ecologically fragile areas such as micro mountainous areas. Standardized Precipitation Evapotranspiration Index (SPEI) is used to characterize the dry-wet conditions (including the drought frequency and intensity) of the climate. And spatiotemporal characteristics and its circulation background in Northeast Sichuan over the past 60 years are analyzed based on trend test, correlation test and abnormal circulation during drought. The main results showed that: (1) The SPEI of various time scales in the northeastern Sichuan region is stable but in August 1997 and August 2006, extreme drought occurred. The oscillation period duration of SPEI at the annual scale is about 6.5 years. From 1961 to 1990, it showed a pattern of turning from dry in the north to wet in the south, while it showed a pattern of turning from wetness in the north to dryness in the south from 1991 to 2020. The dryness and wetness transition varies in different seasons. SPEI shows an increasing trend in summer (concentrated in the southeast, with the highest growth rate reaching 0.224 per decade), while SPEI shows a decreasing trend in winter (− 0.120 per decade ). (2) The frequency of extreme drought in the northern mountainous areas of northeastern Sichuan is relatively high, and the spatial distribution of drought is uneven in different seasons. Among them, the areas with the most severe summer drought are Pingchang and Wanyuan. The first mode of EOF shows quasi-consistent dry-wet change type and the second mode shows northwest-southeast oscillation change type. (3) The northwest-southeast oscillation change type in the region is mainly influenced by SOI (in April, July, and November) and PDO (in summer and autumn). When SOI is high (low), it shows that the southeast is relatively dry (wet), and when PDO is high (low), it shows that the southeast is relatively wet (dry). In addition, the more northward and westward the position of WPSH in July and August, the drier the area becomes (p < 0.01). Furthermore, it is not necessarily the stronger EASMI, the wetter the summer in northeastern Sichuan. On the contrary, it may become drier. The abnormal summer drought in the region may be caused by the abnormal moisture transport in the southwest monsoon and the sinking airflow with the abnormal potential height.