PAOC Colloquium: Marianna Linz (Harvard)

Title: Midlatitude Temperature Extremes and Horizontal Temperature Advection

Abstract:
Local probability distributions of temperature have an asymmetry in the hot and cold sides of the distribution in most locations around the world. The non-Gaussianity of the temperature distribution has implications for extremes with global warming, and so understanding what physically sets the shape of temperature distributions will enable more robust predictions of future temperature. I will present a simple, two-dimensional model of midlatitude temperatures and show how even in such a simple model, asymmetry is achieved. The location of the jet is critical for determining the asymmetries in the temperature distributions. Motivated by the success of this two-dimensional model, I will derive a relationship between the temperature distribution shape and the advection of temperature conditionally-averaged at each temperature percentile. This method enables quantification of the shift of each percentile that is due to changes in the mean temperature, in horizontal temperature advection, and other processes (e.g., radiation and convection). I use the relationship to examine global model simulations in an idealized aquaplanet model with increasing carbon dioxide. Horizontal temperature advection is dominant in decreasing variance, partially compensated by other processes, but the relative roles of horizontal temperature advection and other processes are different for the different carbon dioxide perturbations. The methods presented are general enough to be applied to any tracer.