Boreal winter rainfall anomaly over the tropical indo-pacific and its effect on northern hemisphere atmospheric circulation in CMIP5 models

Experimental outputs of 11 Atmospheric Model Intercomparison Project (AMIP) models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter. The analysis shows that the main features of the interannual variation of tropical rainfall anomalies, especially over the Central Pacific (CP) (5A degrees S-5A degrees N, 175A degrees E-135A degrees W) and Indo-western Pacific (IWP) (20A degrees S-20A degrees N, 110A degrees-150A degrees E) are well captured in all the CMIP5/AMIP models. For the IWP and western Indian Ocean (WIO) (10A degrees S-10A degrees N, 45A degrees-75A degrees E), the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation. During El Nio/La Nia mature phases in boreal winter, consistent with observations, there are geopotential height anomalies known as the Pacific North American (PNA) pattern and Indo-western Pacific and East Asia (IWPEA) pattern in the upper troposphere, and the northwestern Pacific anticyclone (cyclone) (NWPA) in the lower troposphere in the models. Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP, while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO, as the SST anomaly is same in AMIP experiments. It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.