Abstract

The interannual variability of the boreal winter Hadley circulation extents during the period of 1979–2014 and its links to El Niño-Southern Oscillation (ENSO) were investigated by using reanalysis datasets. Results showed that the El Niño (La Niña) events can induce the shrinking (expansion) of Hadley circulation extent in the Southern Hemisphere. For the Northern Hemisphere, El Niño (La Niña) mainly leads to shrinking (expansion) of the Hadley circulation extent in the middle and lower troposphere and expansion (shrinking) of the Hadley circulation extent in the upper troposphere. The ENSO associated meridional temperature gradients have close relationship with the Hadley circulation extents in both Hemispheres. But in the Northern Hemisphere, the ENSO associated eddy momentum flux divergence plays more important role in affecting the Hadley circulation extent than the meridional temperature gradient because of the small local Rossby number. In the Southern Hemisphere, as the ENSO induced eddy momentum flux divergence is small, the meridional temperature gradient dominates the change of the Hadley circulation extent.

Abstract

Based on a daily precipitation observation dataset of 743 stations in China from 1951–2004, the Γ distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during El Niño events than during La Niña events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Niño and La Niña on the frequency of extreme precipitation events are found. Li, W., P. Zhai, and J. Cai, 2011: Research on the relationship of ENSO and the frequency of extreme precipitation events in China. Adv. Clim. Change Res., 2 (2), doi: 10.3724/SP.J.1248.2011.00101.