Springtime tropospheric temperature over the Tibetan Plateau and evolutions of the tropical Pacific SST

Abstract

Using monthly mean data from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCAR) reanalysis and HadISST SST data sets, we investigate the relationship between springtime tropospheric temperature over the Tibetan Plateau and sea surface temperature (SST) over the equatorial Pacific and the associated physical processes. When the Tibetan temperature is low (high) in spring, positive (negative) SST anomalies appear over the tropical central‐eastern Pacific in spring and summer. The relationship is explained by the Asian‐Pacific Oscillation (APO) and the ocean‐atmosphere interaction over the tropical Pacific. In the context of the APO, a lower spring Tibetan tropospheric temperature is associated with a higher tropospheric temperature over the subtropical North Pacific, which is accompanied by a weaker subtropical high over the eastern North Pacific. Accordingly, large‐scale westerly anomalies appear in the lower troposphere of the equatorial central‐eastern Pacific, resulting in an increase in SST over the equatorial central‐eastern Pacific. Numerical simulations with both an ocean‐atmosphere coupled model (the NCAR Community Climate System Model version 3) and an atmospheric model with a prescribed SST scheme (the NCAR Community Atmospheric Model version 3) demonstrate the impacts of the spring Tibetan thermal condition on the tropospheric temperature and atmospheric circulation over the Asian‐Pacific sector and then on the SST over the equatorial eastern Pacific, better explaining the physical processes of the observed Tibetan temperature–Pacific SST relationship.