Delayed Atmospheric Temperature Response to ENSO SST： Role of High SST and the Western Pacific

Tropical zonally symmetric atmospheric warming occurs during ENSO’s warm phase, and lags the equa- torial east Pacific sea surface temperatures (SSTs) by 3–4 months. The role of the Indian and Atlantic oceans on the atmospheric delayed response has been pointed out by earlier studies. For 1951–2004, a regression analysis based on the observed SST data shows the western Pacific has a similarly important role as the Indian and Atlantic. Nevertheless, there is time mismatch of around 1–2 months between the zon...

Delayed atmospheric temperature response to ENSO SST: Role of high SST and the western Pacific

Tropical zonally symmetric atmospheric warming occurs during ENSO's warm phase,and lags the equatorial east Pacific sea surface temperatures (SSTs) by 3--4 months. The roleof the Indian and Atlantic oceans on the atmospheric delayed response has been pointed outby earlier studies. For 1951--2004, a regression analysis based on the observed SST data showsthe western Pacific has a similarly important role as the Indian and Atlantic.Nevertheless, there is time mismatch of around 1--2 months between the zonally averaged tropicalSST anomalies and the atmospheric temperature anomalies. It is expected that the tropospherictemperature should be controlled by diabatic heating forcing, which is sensitive primarily toSST anomalies over regions of high climatological SST, rather than to the tropical mean SSTanomalies. To describe this mechanism, we propose a parameterization scheme of diabatic heatinganomalies dependant on SST anomalies and climatological SST.The 1--2 month mismatch between tropical mean SST anomalies and air temperature anomalies isreconciled by the fact that the tropical mean heating anomalies are dominated by the SST anomaliesover regions of high climatological SST, and lag the tropical mean SST anomalies by 1 month. Themechanism described by this parameterization scheme joins several physical processes of ENSO withreasonable time intervals. And the parameterized heating anomalies work better than the tropicalmean SST anomalies for capturing the atmospheric temperature signal relative to ENSO.