Future tracer transport in CAM-SE

02/05/2013 - 10:00am to 11:00am
NCAR Mesa Lab Main Seminar Room
Christoph Erath



Christoph Erath, NCAR/IMAGe and University of Colorado, Boulder


Future tracer transport in CAM-SE

Finite Volume based Semi-Lagrangian schemes in HOMME



Recently, a highly scalable spectral-element-based version of the High-Order Method Modeling

Environment (HOMME) was integrated in the Community Atmosphere Model (CAM-SE). In

next generation climate modeling efforts there is the need for on the order of 100 prognostic

tracers. Thus, scalable, monotonic, and conservative multi-tracer efficient advection schemes are

of high interest in HOMME.


To address this, we integrate conservative semi-lagrangian multi-tracer transport schemes into

HOMME. The algorithms are specifically designed for multiple processors and the cubed-sphere

grid with the element-wise domain decomposition as employed by HOMME. Our data structures

and design allow us to provide finite volume based numerical schemes with only one commu-

nication of tracer values for each time step. Our semi-lagrangian schemes conserve mass up to

machine precision with monotonic option also on multiple processor systems. In particular, we

discuss and compare the approach of the Conservative Semi-LAgrangian Multi-tracer transport

scheme (CSLAM) algorithm and a new scheme, called SPELT (SPectral Element Lagrangian

Transport), specifically designed for arbitrary quadrilateral grids. Both schemes run on multiple

processor platforms, are highly scalable and multi-tracer efficient.


The ultimate goal is to replace the spectral element tracer transport scheme in CAM-SE while

still using the velocity provided by the spectral element discretization. We compare the effec-

tiveness of our hybrid approach on the baroclinic wave test example. This strategy promise to

be very suitable and computationally cheaper for future climate modeling with CAM-SE.


CISL Seminar Recording