11:00 AM - 11:15 AM
[ACG33-07] Energetics of Atmospheric Meridional Teleconnections over the North Pacific in Winter
Keywords:Teleconnection, Energy conversion, Intraseasonal variability
The PNA pattern, the WP pattern, and the NPO are known as the dominant teleconnection patterns in the North Pacific in winter, all of which feature north-south dipoles of atmospheric circulation anomalies over the basin. For the formation of the PNA patterns, it has been pointed out that, in addition to tropical forcing, kinetic (barotropic) energy conversion and feedback from transient eddies are important, but their relative contributions including baroclinic processes have not been investigated. For the WP pattern, Tanaka et al. (2016) systematically evaluated the contribution of each energy conversion and generation and showed that the available potential (baroclinic) energy conversion from the climatological-mean field with strong baroclinicity is important for its maintenance. In this study, we systematically evaluated the energetics of atmospheric circulation variability with a north-south dipole structure over the North Pacific during winter. To focus on the atmospheric internal processes, the energy budget analysis was performed for the intraseasonal component of the monthly mean anomalies.
For the PNA pattern and the NPO, baroclinic energy conversion contributes to their maintenance with the highest efficiency, similar to the WP pattern. This conversion arises from the vertical structure with the vertical phase tilt of geopotential anomalies. For the PNA pattern, barotropic energy conversion is secondary for its maintenance but still has a higher efficiency compared to the WP pattern and NPO.
To investigate the dependence of the energetics with geographic location, a similar analysis was conducted systematically for atmospheric circulation variabilities with a north-south dipole structure over the North Pacific in winter. In all variability patterns, baroclinic energy conversion has the largest contribution. However, its efficiency is rather geographically uniform across variability patterns over the North Pacific. By contrast, the barotropic energy conversion efficiency is moderate but has a strong geographical dependence and primarily determines the geographical distribution of the total energy conversion efficiency. The variability pattern with the greatest energy conversion efficiency is associated with mid-tropospheric zonal wind anomalies situated in the exit region of the climatological jet in the central North Pacific. This is consistent with the fact that the PNA pattern is the most dominant variability over the wintertime North Pacific. There is another maximum in the energy conversion efficiency over the subpolar North Pacific. These results illustrate that the climatological jet difluence and baroclinicity are key to domination and energization in the meridional teleconnectivity over the wintertime North Pacific.
For the PNA pattern and the NPO, baroclinic energy conversion contributes to their maintenance with the highest efficiency, similar to the WP pattern. This conversion arises from the vertical structure with the vertical phase tilt of geopotential anomalies. For the PNA pattern, barotropic energy conversion is secondary for its maintenance but still has a higher efficiency compared to the WP pattern and NPO.
To investigate the dependence of the energetics with geographic location, a similar analysis was conducted systematically for atmospheric circulation variabilities with a north-south dipole structure over the North Pacific in winter. In all variability patterns, baroclinic energy conversion has the largest contribution. However, its efficiency is rather geographically uniform across variability patterns over the North Pacific. By contrast, the barotropic energy conversion efficiency is moderate but has a strong geographical dependence and primarily determines the geographical distribution of the total energy conversion efficiency. The variability pattern with the greatest energy conversion efficiency is associated with mid-tropospheric zonal wind anomalies situated in the exit region of the climatological jet in the central North Pacific. This is consistent with the fact that the PNA pattern is the most dominant variability over the wintertime North Pacific. There is another maximum in the energy conversion efficiency over the subpolar North Pacific. These results illustrate that the climatological jet difluence and baroclinicity are key to domination and energization in the meridional teleconnectivity over the wintertime North Pacific.