One of the most interesting, and perhaps personally resonant, papers I’ve ever come across is by Mikaela Sundberg (2010) and is called “Cultures of simulations vs. cultures of calculations? The development of simulation practices in meteorology and astrophysics". The two cultures named in the title refers to two different approaches to numerical modeling and simulation in science. The paper looks at characteristics of these two culture in astrophysics and meteorology, and finds some differences.

Like I’ve written about before, I have had a very strong interest in writing my own simple GCM/dynamical core. After several frustrating initial attempts, partly described here I switched strategy. Rather than attempting to reimplement someone else’s model from their description, I would start from the primitive equations and derive my own model, aiming for as much simplicity as possible in the system of equations. By working in an isobaric (pressure) vertical coordinate, the equations become very simple, but implementing a non-flat surface becomes computationally hard, so I chose simplicity over realism here for the first try.

The Simple Dynamical Core Lab (SDYCORE LAB) is a personal project to explore some numerical algorithms involved in primitive equations models of atmospheric dynamics in a simplified setting. The primitive equations are a set of nonlinear partial differential equations governing the large scale flow of fluids on a rotating planet. All modern weather prediction and general circulation models have at their core a solver for the primitive equations, with or without extra approximations.

Last spring, when I returned to work after my paternity leave, I felt frustrated that the GCM/ESM (CESM1) I’m using for my research is so damned complicated. It’s very hard to get any kind of feeling for how the massive model actually works. Of course I could spend forever reading the code and technical documentation, but the full complexity makes it difficult to grasp, and I would not have enough time to spend on actually doing my own research.

Don’t get me wrong, I like my model. It’s just that I’m a little bit uncomfortable with using models I don’t fully understand. I guess this is an aspect of a subtle cultural difference between meteorology and some other physical sciences [1]. Since I have about 6 years of training as a physicist I bring that cultural baggage with me into my climate science/meteorology work, and It’s making me uncomfortable with the “black-boxiness” of modern Earth System Models. In the physics fields I trained in you’re generalyy expected to build your own simulation code, and if you inherit some code you’re usually inheriting it from the person who built it and you’re expected to fully understand everything before using it. Needless to say, that’s not how it works in modern meteorology.