Chapter 7 - Tropospheric Biennial Oscillation of Monsoon Rainfall and Its Association With El Niño–Southern Oscillation

Abstract

Based on observations and a set of atmospheric model intercomparison project (AMIP)-type simulations, the climatic characteristics and dominant spatial patterns of summer rainfall at tropospheric biennial oscillation (TBO) timescales over the East Asian summer monsoon (EASM) region are examined, and the association with sea surface temperature anomalies (SSTAs) and El Niño–Southern Oscillation are analyzed in this chapter. It was noted that, to some extent, the AMIP run successfully simulated the spatial distribution and amplitude of the observed TBO component. Furthermore, the AMIP ensemble mean increased the fraction of total variance of the TBO component, suggesting that SSTAs may have a rainfall response over the EASM region on TBO timescales. The analysis also indicated that a spatial pattern of rainfall at TBO timescales with opposite variations between northern and southern China showed a consistent and robust relationship with SSTAs in the tropical Pacific Ocean in both the AMIP simulations and observations. Statistically, when an El Niño (La Niña) develops, northern China favors deficient (enhanced) precipitation and southern China favors enhanced (deficient) precipitation at TBO timescales.