On the reduced GloSea6 hindcast skill in Northeast Asian Summer Rainfall associated with two extreme El Niño events

Abstract In this study, the GloSea6 hindcast (HCST) of UK Met Office is used to investigate how this climate model explains the features of such opposite teleconnections on the following summer in decaying periods for two extreme El Niño cases ('97/'98 and '15/'16). In addition, the associated atmospheric and oceanic characteristics are analyzed to explore the reason of the inaccurate simulation of GloSea6. Results show that the ocean-atmosphere patterns such as an intensified Western North Pacific Anomalous Anticyclone (AAC) during both spring and summer in '98 HCST are broadly similar patterns to the observation in spite of the relatively weaker intensities of the atmospheric anomaly over monsoonal region and the northeast Asian summer rainfall anomaly (NASRA). Meanwhile, '16 HCST does not capture the observed spatial pattern of precipitation and SST. Actually, it simulates the teleconnection closer to '98 observation rather than '16 observation. '16 observation shows a weak formation of AAC and an extensive dry anomaly in the northeast Asia, but '16 HCST shows a meridional dipole of the rainband associated with AAC formation. The poor performance of the GloSea6 for the '16 case may be due to stronger simulated capacitor effect on the Indian Ocean than the observed, which is caused by higher sensitivity of atmospheric convective activity to the eastern equatorial Pacific SST and slower decaying of the warmed Indian Ocean during the spring season than the observation.