Anomalous convective activity over sub-tropical east Pacific during 2015 and associated boreal summer monsoon teleconnections

The eastern Pacific Ocean received a record highest number of sub-tropical convective activities during boreal summer (June-September) of 2015, since last four decades. The associated rainfall distribution was also atypical with anomalously enhanced rainfall extending from equator to sub-tropical central-eastern Pacific. The present analysis reveals a pronounced meridional sea surface temperature (SST) gradient across central-eastern Pacific, with the mean SST exceeding 28 A degrees C over sub-tropical north Pacific, setting up favorable conditions for these enhanced convective activities. It is found that these anomalous features promoted northward spanning of westerly anomalies and drastically modified the east-west circulation over sub-tropical north Pacific. This seems to induce large-scale subsidence over the off-equatorial monsoon regions of south and south-east Asia, thus constituting an east-west asymmetry over sub-tropical Indo-Pacific region. Based on our observational study, it can be concluded that the sub-tropical convective activities over east Pacific may play a pivotal role in mediating the Pacific-monsoon teleconnection through the unexplored meridional SST gradient across Pacific.