Water Supply (May 2021)

Spatial distribution of extreme precipitation in the Tibetan Plateau and effects of external forcing factors based on Generalized Pareto Distribution

  • Jiajia Gao,
  • Pengfei Ma,
  • Jun Du,
  • Xiaoqing Huang

DOI
https://doi.org/10.2166/ws.2020.365
Journal volume & issue
Vol. 21, no. 3
pp. 1253 – 1262

Abstract

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The daily precipitation data of the years 1955–2017 from May to September were retrieved; then a Generalized Pareto Distribution (GPD) and maximum likelihood methods were adopted to understand trends and calculate the reappearance period of heavy precipitation in the Tibetan Plateau (TP). The daily precipitation values at 22 stations in the TP were found to conform to the model, and theoretical and measured frequencies were consistent. According to the spatial distribution of the maximum precipitation value, the extreme values of Shigatse and Lhasa showed large fluctuations, and the probability of record-breaking precipitation events was low. In the western part of Nagqu, the probability of extreme precipitation was relatively low, and that of record-breaking precipitation was relatively high. The peak values of extreme precipitation in the flood season in the TP generally exhibited a decreasing trend from southeast to northwest, and the extreme value of the flood season that reappeared in the southeast region was approximately twice that of the northwest region. The maximum rainfall in most areas will exceed 20 mm in the next 5–10 years, and the maximum rainfall in Shigatse will reach 52.7 mm. After 15 years of recurrence in various regions, the peak rainfall in the flood season has become low. Most of the regions in the model have different responses to ENSO and Indian Ocean monsoon indices with external forcing factors. HIGHLIGHTS The Generalized Pareto Distribution method was first used in the TP.; The fitting results agree with the observation results.; The probability of breaking records was higher due to the lower probability of extreme precipitation.; The recurrence period of extreme precipitation gradually decreases from southeast to northwest in the TP.; ENSO and SST index for the Indian Ocean has a great influence on the extreme precipitation in the TP.;

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