Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data

A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. A case study on two catchments in eastern Australia illustrates this framework. To develop an identifiable model characterizing long-term variability for the first level of the hierarchy, paleoclimate proxies, and instrumental indices describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. The Markov chain model, previously used to simulate oscillating wet/dry climate states, is found to underestimate the probability of wet/dry periods >5 yr, and is rejected in favor of a gamma distribution for simulating the run lengths of the wet/dry IPO-PDO states. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. The model is able to replicate observed statistics such as seasonal and multiyear accumulated rainfall distributions and interannual autocorrelations. Mean seasonal rainfall in the IPO-PDO dry states is found to be 15%-28% lower than the wet state at the case study sites. In comparison, an annual lag-one autoregressive model is unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Copyright © 2011 by the American Geophysical Union.Benjamin J. Henley, Mark A. Thyer, George Kuczera and Stewart W. Frank

Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data

A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. A case study on two catchments in eastern Australia illustrates this framework. To develop an identifiable model characterizing long-term variability for the first level of the hierarchy, paleoclimate proxies, and instrumental indices describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. The Markov chain model, previously used to simulate oscillating wet/dry climate states, is found to underestimate the probability of wet/dry periods >5 yr, and is rejected in favor of a gamma distribution for simulating the run lengths of the wet/dry IPO-PDO states. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. The model is able to replicate observed statistics such as seasonal and multiyear accumulated rainfall distributions and interannual autocorrelations. Mean seasonal rainfall in the IPO-PDO dry states is found to be 15%-28% lower than the wet state at the case study sites. In comparison, an annual lag-one autoregressive model is unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Copyright © 2011 by the American Geophysical Union.Benjamin J. Henley, Mark A. Thyer, George Kuczera and Stewart W. Frank

Review: The Incendiaries by R.O. Kwon

A book review of R.O. Kwon\u27s 2018 debut novel, The Incendiaries

Hyun Kwon

Today I had the wonderful opportunity to discover more of the story of one of our faculty, Hyun Kwon, chair of the Department of Engineering & Computer Science. The conversation left me inspired, reminding me yet again of the amazing faculty who work at Andrews University. Hyun was born as a second child among three siblings in South Korea. Her father was a police office, her mom a full-time mom. She was a high achiever academically and after attending an elite science track high school, she continued to the prestigious Korean Advanced Institute of Technology (KAIST) with a full governmental scholarship. She chose engineering to study because in that area math and science are applied to bring positive change to society. It was while pursuing her PhD at KAIST that Hyun visited the U.S. and it so impressed her that she decided she wanted to come and live here at some point. It happened sooner than she expected; Hyun transferred and was soon on her way to complete her PhD at the University of Louisville. Up to that time in her life Hyun had been focused on academic and professional success. She never had many Christian friends in her circle in Korea and still thinks that if she had stayed in Korea her ego would have become so big she would not have needed God! And so started her Exodus experience: Leaving her country, crossing the ocean and facing difficulties that come with that kind of transition. Read the rest of Hyun’s story in Stories of Andrews at andrews.edu/stories. Hers is a story that is part of the spirit of Andrews. Andrea Luxtonhttps://digitalcommons.andrews.edu/stories-2017-spring/1003/thumbnail.jp

Sensitivity analysis of finite element-based equilibrium problems using Padé approximants

Finite element analysis is commonly used to analyze structures. It is often desirable to use the solution of finite element problems as part of the objective function for structural optimization;Since finite element solutions can be quite demanding numerically, it is a common practice to approximate the finite element solution in the neighborhood of an original design for the purpose of simplifying the calculation of the objective function. This procedure is called sensitivity analysis. The range of validity of the approximation is very important. The range usually depends on whether high order terms are included in the expansion and, if they are included, on the convergence of the expansion;This thesis presents the sensitivity analysis of finite element-based equilibrium problems using Pade approximants. The goal is to provide an approximation valid for a large design change. The thesis lays the foundation for Pade approximants in a finite element context and illustrates their use through several examples