[세미나] 박재흥 박사님

Understanding of the connection between tropics and extratropics in the Pacific

#### 박재흥 박사 (포항공과대학교) #### 2021년 05월 11일 (화) 16:00 #### ZOOM Meeting
#### Abstract Various climate (i.e., oceanic and atmospheric) variability modes with interannual timescales are co- existed around the Pacific Ocean. In the tropics, the El Nino-Southern Oscillation (ENSO) which is characterized by the strongest interannual variability in the world exists. For the subtropical North Pacific, the Pacific Meridional Mode (PMM) which is another ocean-atmospheric coupled variability mode evolves, in association with the Pacific Intertropical Convergence Zone (ITCZ). For the midlatitudes, the Aleutian Low (AL) and the North Pacific Oscillation (NPO) reside together, which are primary atmospheric modes, featured as a monopole and a meridional dipole of sea level pressure anomaly, respectively.

It is known that the Pacific climate variability modes interact spatiotemporally. When a positive phase ENSO (i.e., El Nino) occurs in boreal winter, it accompanies stationary Rossby waves propagating midlatitudes. Simultaneously, the AL tends to intensify as moving toward the North America. Then, the intensified AL modulates underlying North Pacific condition and weather/climate over the East Asia to the North America (vice versa for La Nina).

Also, the climate variability in the midlatitudes is able to affect tropical climate. The positive phase NPO (north anticyclonic-south cyclonic flows) in boreal winter induces low-level westerly wind anomaly in the subtropical North Pacific. Interacting with the climatological mean trade wind, the low-level zonal wind anomaly induces anomalous sea surface temperature warming by reduced latent heat flux, which develops into an El Nino event in the following winter (vice versa for negative phase NPO). Additionally, the PMM in the subtropics in boreal spring is reported to trigger following ENSO events.

In the seminar, recent findings regarding tropics-extratropics connection in the Pacific Ocean will be addressed based on the analysis of the CMIP models and the observational reanalysis dataset.