# Seminars

# Atmosphere Ocean Science Student Seminar

#### Isentropic Analysis of Convectionâ€™s Response to Numerics and Thermal Forcing

**Speaker:**
Michael Lever

**Location:**
Warren Weaver Hall 1314

**Date:**
Friday, February 14, 2020, 4 p.m.

**Synopsis:**

Thermodynamic relationships for moist air are highly

nonlinear, and therefore only truly hold on the length-scale of an

individual air parcel. Additionally, under the Eulerian framework of

integration, deep convection is a rare event in space-time with

approximately one percent of the domain involved at any one time. These

two facts couple to make analysis difficult. In practice, one petabyte

of floating point data may be generated for an experiment using a

numerical model of convection. This amount of data is infeasible to work

with and so averaging must be performed, but the rarity of events and

the non-linearity of the dynamics makes simple averages in space or time

inappropriate.

Instead, I will use an isentropic streamfunction and the Mean Air Flow

as Lagrangian Dynamics Approximation (MAFALDA). These methods use

averages of observed quantities conditioned on height and an adiabatic

invariant -- like entropy. This reduces the dimensionality of the data

from 4D to 2D and can reduce the size of the data from terabytes to a

few megabytes. Even though the data has been so strongly averaged, this

physically motivated averaging scheme preserves the information of

interest. Furthermore, the 2D, steady state nature of the average allows

construction of a streamfunction. Closed streamlines are then

interpreted as representative parcel paths, and classical thermodynamic

analysis -- which usually is accurate only for a parcel -- succeeds in

extracting important bulk properties of the flow.

Namely, the response of convection to vertical resolution and the change

in kinetic energy generation with warming sea surface temperatures will

be discussed.