ISSN 1006-9895

CN 11-1768/O4

Effects of 10-30-day Atmospheric Low Frequency Oscillations at Mid-High Latitudes and Low Latitudes on Summer Precipitation in China
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Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Infomation Science and Technology

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    Abstract:

    Atmospheric low frequency oscillations are closely related to summer precipitation and related catastrophic weather in China, and it is of great significance to study the effects of 10-30-day low frequency oscillations on weather and climate. In this paper, the effects and mechanisms of the 10-30-day oscillations at mid-high latitudes and low latitudes on the average summer precipitation in China during the period 1991-2020 are investigated by using station observations data and ERA5 reanalysis data, etc. According to the singular value decomposition(SVD) analysis, the 10-30-day oscillations at mid-high latitude are closely related to the spatial distribution of inverse-phase precipitation over Yangtze River and South China Sea, When the 10-30-day oscillations in north of Lake Baikal are weak and the oscillations in south of Lake Baikal are strong, the precipitation exhibits a significant decrease in the Yangtze River basin while showing a notable increase from the South China Sea to South China; The key region of the low latitudes 10-30-day oscillations is located in the northwestern Pacific, where precipitation in southern China exhibits a significant positive anomaly during periods of strong oscillation within this region. The 10-30-day oscillations at mid-high latitudes mainly affect the mean position of the summer subtropical westerly jet stream through wave-current interactions, which makes the position of the secondary circulation near the jet stream to be anomalous, thus indirectly affecting the precipitation in the Yangtze River Basin and the South China Sea to South China, and making it show anomalous inverse-phase distributions; Distinguishing it from the mid-high latitudes, the 10-30-day oscillations at low latitudes over northwest Pacific propagate northwestward to southern China, directly inducing precipitation anomalies.

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History
  • Received:September 28,2023
  • Revised:February 06,2024
  • Adopted:April 01,2024
  • Online: April 07,2024
  • Published: