TRR 181 Seminar "A flexible tool for diagnosing water, energy and entropy budgets in climate models"

The TRR 181 seminar is held by Dr. Valerio Lembo (Universität Hamburg, TP S1) on

A flexible tool for diagnosing water, energy and entropy budgets in climate models

at Universität Hamburg on June 15 at 10 am, Bundesstr. 53, room 22/23 (ground floor).

Abstract

With the increasing number and complexity of climate models, the demand for diagnostic tools has dramatically increased in recent years. Performance metrics have been thus developed, for comparison of model simulations with observations, when possible. Metrics are also aimed at assessing whether models obey to basic physical principles, such as the conservation of energy and mass and the second law of thermodynamics. As a non-equilibrium steady state dissipative system, climate can be viewed in its long-term behaviour as a thermal engine, under certain assumptions approximating to an equivalent Carnot energy cycle. Global metrics are thus developed, relying on thermodynamic quantities, such as efficiency, irreversibility and entropy production. These metrics are informative of various processes
involving energy exchanges in the climate system, linking together the conversion of available potential energy into kinetic energy through meridional heat transports from lower to higher latitudes, and its dissipation to smaller scales through viscous processes.
The Earth System Model eValuation Tool (ESMValTool) is a community effort to adapt existing model diagnostics (and develop new ones) to a common standard for the assessment of future climate model simulations, with a particular focus on the Phase 6 of the CMIP Project. As part of this effort, a new flexible diagnostic tool is here presented, aimed at studying the global energy budget and meridional heat transports, the hydrological cycle, and the material entropy production of global climate models and reanalyses. Annual mean maps, meridional sections, time series and global mean values are computed. A measure of the Carnot efficiency and the degree of irreversibility are also provided. The program receives as input 2-D gridded data at the surface, near-surface and TOA. If a land-sea mask is provided, the
program also computes the required quantities separately on the continents and oceans. The program currently includes computation of material entropy production from two methods: the direct method, involving the main individual irreversible processes occurring in the system, and the indirect method, involving heating by convergence of radiative heat fluxes. Depending on the limitations imposed by the availability of fields with appropriate time and space resolution in standard climate model outputs, the former method will be either included in the ESMValTool community diagnostics or not.