The asymmetric effect of different types of ENSO and ENSO Modoki on rainy season over the Yellow River basin, China

Precipitation is considered one of the most important forcing data in scientific investigations involving agriculture, water management, and climate variability. Knowledge of precipitation variation during rainy seasons is the key to the understanding of the precipitation variability under the effect of climate change. This study evaluated some rainy season features (e.g., onset, retreat, and rainy-season precipitation) over the Yellow River basin (YRB), China, and the influence of the El Nino-Southern Oscillation (ENSO). The multi-scale moving t-test was applied to capture the onset and retreat of rainy season. The possible linkage between ENSO-induced precipitation and monsoon and atmospheric circulation was also explored. From the analysis, four conclusions can be drawn: (1) Rainy season began the earliest (latest) and ended the latest (earliest) in the southern (northern) YRB, with rainy-season precipitation increasing from northwest to southeast. (2) Rainy-season precipitation showed strong correlation to SST in Nino regions. Precipitation can reach up to 20% above the average precipitation for decaying central Pacific warming (CPW) and down to 35% below the average precipitation for developing eastern Pacific warming (EPW) in most areas of the YRB. (3) Developing El Nino showed the strongest dry signals among developing ENSO and ENSO Modoki phases. Decaying El Nino and El Nino Modoki indicated overall increasing precipitation, with La Nina and La Nina Modoki during the corresponding period showing the opposite tendency. (4) Different performances of ENSO-induced precipitation attributed to the combined influence of the monsoon from the India Ocean and the atmospheric circulation in the Western North Pacific (WNP). Stronger anti-cyclone and monsoon are related to increasing rainy-season precipitation. These findings can improve the predictability of rainy season features and ENSO-induced precipitation.

Automated summary

This study evaluated the rainy season features in the Yellow River basin, China, and the influence of the El Nino-Southern Oscillation (ENSO) on precipitation. The findings showed that the rainy season began and ended earliest in the southern region of the Yellow River basin, with increasing precipitation from northwest to southeast. Rainy-season precipitation also exhibited strong correlations with sea surface temperature in the Nino regions, and different ENSO phases had varying impacts on precipitation.