SLS Seminar: Rei Chemke (Columbia University)
The latitudinal dependence of geostrophic turbulence in the atmosphere and ocean
Abstract: The study of atmospheric and oceanic eddies is important for understanding the dynamics of the general circulation in the atmosphere and ocean and the governing scales within. Extant theories for the behavior of these eddies, such as geostrophic turbulence, rely on the theoretical work of two-dimensional turbulence. The latitudinal variations of the mean state (e.g., sphericity, temperature, winds, etc.) adds an additional complexity to geostrophic turbulence theory. Here the behavior of the eddies' energy cycle in both atmosphere and ocean is studied as a function of latitude using both idealized GCM simulations and atmospheric and oceanic reanalysis data. The energy fluxes (i.e., eddy-mean and eddy-eddy interactions) and macroturbulent scales are found to show different behavior poleward and equatorward of a ‘‘supercriticality latitude’’. Poleward of this latitude, where the quasi-geostrophic flow is supercritical to baroclinic instability, a classic geostrophic turbulence picture appears with a barotropization of the flow together with an inverse energy cascade up to the Rhines scale. Equatorward of this latitude the eddy-mean flow interactions play a major role in the balance. The effect of the nonlinear eddy-eddy interactions on the mean flow is further studied by comparing a set of full and quasi-linear idealized simulations. These interactions are found to have a minor effect on the jet scale, which thus coincides with the Rhines scale even when these interactions are absent. The eddy-eddy interactions are not a prerequisite for jet formation in the atmosphere, and even suppress their formation at high latitudes. Under global warming the eddy flow is found be dominated by eddy-mean flow interactions and have a more baroclinic nature.
About the Speaker
I am a NOAA Climate & Global Change Postdoctoral Fellow at Columbia University, working with Lorenzo Polvani on the response of the Hadley circulation to global warming, using hierarchy of configurations of the Community Earth System Model
About the Series
The Atmosphere, Ocean and Climate Sack Lunch Seminar Series is an informal seminar series within PAOC that focuses on more specialized topics than the PAOC Colloquium. Seminar topics include all research concerning the science of atmosphere, ocean and climate. The seminars usually take place on Wednesdays from 12-1pm in 54-915. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.
