Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Elizabeth R. Jessup

Second Advisor

Allison H. Baker

Third Advisor

Dorit M. Hammerling

Fourth Advisor

Thomas Hauser

Fifth Advisor

Abtin Rahimian

Abstract

The Community Earth System Model (CESMTM) is a global climate model whose simulations have significant impact on social policy. The CESM is large and complex, consisting of about 1.5 million lines of code and several coupled component models. Quality assurance is necessary for the continued development and improvement of the CESM. To address this need, the CESM Ensemble Consistency Test (CESM-ECT) was developed as a statistical test for consistency between experimental outputs and an accepted ensemble. The CESM-ECT provides rapid feedback to model developers, scientists, and end users without expert knowledge of climate science. In this work, we investigate the properties and composition of the CESM-ECT ensemble, resulting in an improved test. We expand the CESM-ECT by creating an "ultra-fast" test at the ninth CESM time step and demonstrate that the test can detect statistical inconsistency in multiple CESM component models. Equipped with refined tests, we focus on locating sources of statistical inconsistency. Our approach uses graph analysis to find relevant segments of CESM code, and we propose an iterative instrumentation method for converging on the sources of inconsistency. We discuss the modification and performance optimization of a central atmospheric microphysics package with the assistance of our newly developed tools. We conclude by advancing a strategy to realize our iterative instrumentation process, which will identify specific code lines leading to statistical inconsistency. The framework created in this thesis will enable full-featured quality assurance for the CESM through consistency testing and error source identification.

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