Variation of Precipitation in Taihu Lake Basin and Its Relationship with Atmospheric Circulation

Abstract

【Objective】 Precipitation and its variation is the driver of all ecological functions in a catchment. It is affected by many factors. This paper investigates the variation in precipitation and its multi-scale correlations with atmospheric circulation in the Taihu Lake Basin (TLB), China. 【Method】 The analysis was based on precipitation measured from 1960 to 2020 from 30 meteorological stations across the basin. Its multi-scale oscillations, as well as correlation with single and combined atmospheric circulation factors were analyzed using the Mann Kendall (MK), modified Mann Kendall (MMK), wavelet coherence (WTC), and multiple wavelet coherence (MWC). 【Result】 ① The annual and seasonal trends identified by MMK and MK from the precipitation series was similar, but the significance differed between the two methods. We found the largest upward trend in annual precipitation, but the seasonal precipitation in winter had the smallest upward trend. MMK detected significance that MK failed to identify, especially for spring precipitation. ② WTC found that the precipitation and atmospheric circulation factors were nonlinearly correlated in a complex way, but their correlation varied with time. ③ For single atmospheric circulation factors, the EASM was the most influential teleconnection affecting precipitaton in the TLB. Among the multivariates, Prep-AO-PDO-ENSO-EASM-DMI had the greatest impact on precipitation in TLB. 【Conclusion】 The dominant tele-correlation alone cannot explain the relationship between precipitation and atmospheric circulation, and a combination of atmospheric circulation factors and the highest percentage of significant power (POSP) offered the best explanation for precipitation variation in TLB.

Keywords

• mmk trend test
• multi-wavelet coherence
• combined atmospheric circulation
• multi-scale effect
• percentage of significant power