Main research areas in Center for Monsoon System Research include

• variability of Asian monsoon system and its mechanisms,
• interaction between Asian monsoon and ENSO cycle,
• And the physical basis for East Asian climate system and short-term climate variations in China.

Impact of Atlantic SST anomalies on the Climate in the western North Pacific in Summer 1998

• Most attention has been paid to the influence of SSTs in the Pacific and Indian Ocean on the circulation and precipitation in the western North Pacific . The impact of Atlantic SST anomalies has been ignored.
• Seasonal mean of the Tropical North Atlantic (TNA) SST index (5.5-23.5oN, 15-57.5oW) in summer 1998 is the highest since 1948.

Fig. 1 Observed SST anomalies (oC) in the summer 1998. T he years 1961 to 1990 are chosen as the reference period.

Model and Experimental design
Model: Hadley Centre model (HadAM3) 2.5o by 3.75o 19 levels.
Global experiment: forced with global observed SSTs.
“without Atlantic” experiment: forced with observed SSTs except in the Atlantic (latitude band 30oS-75oN) where the climatological SSTs were used.
Atlantic experiment: “Global” – “without Atlantic”.

The rainfall anomalies and associated circulation anomalies are well reproduced when the model is forced with the observed global SSTs.
The SST anomalies in the Atlantic play a comparable role as those outside the Atlantic in influencing the circulation and precipitation in the western North Pacific in summer 1998, through an eastward equatorial stationary wave.

Fig. 2 Observed and ensemble-mean anomalies (mm day-1).

 

The propagation of quasi-stationary planetary waves and its interannual variations are studied with the observation data, dynamical theory and numerical simulations. Two waveguides are documented in the northern hemisphere winter. Further researches reveal the relationship between the wave propagation and the Arctic Oscillation on interannual timescales.

The E-P Flux of planetary waves based on the observation indicates the wave propagation along two waveguides.

Regression (contours) / correlation (shading) pattern between ū anomalies and the normalized planetary wave activity index based on winter data from 1959 to 1998. This north-south seesaw of ū corresponds to the Northern Annular Mode or the Arctic Oscillation.

Schematic picture of the waveguides showing the three-dimensional propagation of quasi-stationary planetary waves during the northern hemisphere winter.
 

Director: Prof. Chen Wen
Deputy Director: Prof. Lu Riyu
Tel: +86-10-62564620