Model assessment of the observed relationship between El Niño and the northern East Asian summer monsoon using the Community Climate System Model Community Atmosphere Model-Community Land Model version 3 (CAM-CLM3)

Plausibility and reproducibility of the relationship and physical mechanisms proposed between the northern East Asian summer monsoon (NEASM) and El Niño are verified and illuminated using the Community Climate System Model (CCSM) with the Community Atmosphere Model-Community Land Model version 3 (CAM-CLM3). The climate responses over East Asia and western North Pacific to El Niño are simulated in the CCSM3 using dynamic atmosphere and land with prescribed climatological and El Niño sea surface temperature (SST) anomalies. A significantly intensified NEASM is simulated for the El Niño experiments, which validates the positive correlation between NEASM precipitation and El Niño found in recent observational analysis. Analysis of lower level wind vector and vorticity in the model experiments elucidates the physical mechanism behind the positive correlation between NEASM precipitation and El Niño, and shows that the western North Pacific anticyclone plays an important role in the connection between the NEASM and the tropical SST anomalies.