Publications

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2018
Wang, CY, Xie SP, Kosaka Y.  2018.  Indo-Western Pacific Climate Variability: ENSO Forcing and Internal Dynamics in a Tropical Pacific Pacemaker Simulation. Journal of Climate. 31:10123-10139.   10.1175/jcli-d-18-0203.1   AbstractWebsite

El Nino-Southern Oscillation (ENSO) peaks in boreal winter but its impact on Indo-western Pacific climate persists for another two seasons. Key ocean-atmosphere interaction processes for the ENSO effect are investigated using the Pacific Ocean-Global Atmosphere (POGA) experiment with a coupled general circulation model, where tropical Pacific sea surface temperature (SST) anomalies are restored to follow observations while the atmosphere and oceans are fully coupled elsewhere. The POGA shows skills in simulating the ENSO-forced warming of the tropical Indian Ocean and an anomalous anticyclonic circulation pattern over the northwestern tropical Pacific in the post-El Nino spring and summer. The 10-member POGA ensemble allows decomposing Indo-western Pacific variability into the ENSO forced and ENSO-unrelated (internal) components. Internal variability is comparable to the ENSO forcing in magnitude and independent of ENSO amplitude and phase. Random internal variability causes apparent decadal modulations of ENSO correlations over the Indo-western Pacific, which are high during epochs of high ENSO variance. This is broadly consistent with instrumental observations over the past 130 years as documented in recent studies. Internal variability features a sea level pressure pattern that extends into the north Indian Ocean and is associated with coherent SST anomalies from the Arabian Sea to the western Pacific, suggestive of ocean-atmosphere coupling.

2017
Hu, KM, Xie SP, Huang G.  2017.  Orographically Anchored El Nino Effect on Summer Rainfall in Central China. Journal of Climate. 30:10037-10045.   10.1175/jcli-d-17-0312.1   AbstractWebsite

Year-to-year variations in summer precipitation have great socioeconomic impacts on China. Historical rainfall variability over China is investigated using a newly released high-resolution dataset. The results reveal summer-mean rainfall anomalies associated with ENSO that are anchored by mountains in central China east of the Tibetan Plateau. These orographically anchored hot spots of ENSO influence are poorly represented in coarse-resolution datasets so far in use. In post-El Nino summers, an anomalous anticyclone forms over the tropical northwest Pacific, and the anomalous southwesterlies on the northwest flank cause rainfall to increase in mountainous central China through orographic lift. At upper levels, the winds induce additional adiabatic updraft by increasing the eastward advection of warm air from Tibet. In post-El Nino summers, large-scale moisture convergence induces rainfall anomalies elsewhere over flat eastern China, which move northward from June to August and amount to little in the seasonal mean.