Super-parameterization is a type of multi-model framework (MMF), which is a technique for modeling a physical system with a wide range of important scales (such as the climate system). A model is typically designed to simulate things on a certain scale of interest, but it also needs information about things happening on smaller and larger scales. This missing information is condensed into model parameters, which can be fixed or variable. A parameterization* is a method for estimating parameter values without explicitly simulating the processes directly. Parameterizations can sometimes be thought of as very low order models. Super-parameterization replaces one or more parameterizations with a second model that is designed to simulate the processes explicitly, in order to provide more accurate parameter values back to the main “host” model. Continue reading
I’ve been struggling with a model error for over a week now, and it all seemed to revolve around this Fortran subroutine “shr_sys_flush()”. The error usually showed up in the log file as a “floating point exception”, but other times I got a “segmentation fault”. I had an epiphany this afternoon that will hopefully help other people with similar errors. Continue reading
At a recent conference I was talking to a colleague about research ideas, and we kept coming back to the conclusion that we don’t know as much as we should about how clouds are treated in the various models used around the world. There are many different schemes in use today and most of them are closely related to one another, but it’s hard to keep track of the subtle differences between the approaches. Sometimes it’s hard to find any information about the particular configuration of the convective schemes in certain models. I decided to compile a list of the different types of parameterization schemes, and gather some notes on the key papers that developed these schemes. Continue reading
While working on my current research on the African monsoon system, I often wonder about how the monsoon would change if I could reshape the african continent. But to answer this, it would be nice if you could simplify the problem and remove all the other continents. I’ve talked to other people who have similar question about how the Inter-Tropical Convergence Zone (ITCZ) is affected by the existence of land masses. Below are some notes for setting up a model simulation using the NCAR CESM with an idealized land mass for exploring these questions. Continue reading
In a previous post I outlined how I set up CESM in aqua-planet mode with a specified sea surface temperature (SST) distribution. However, there are a few drawbacks to using prescribed SST. The biggest caveat is that fixed surface temperature can effectively be an infinite source of energy. I saw a poster a at a meeting last year that compared a simulation with prescribed SST to another with a slab ocean model (SOM) and the results were very striking, so I started thinking that I need to explore this type of modelling more. Below are my notes for setting up a aqua-planet slab-ocean configuration in CESM 1.2 on the Yellowstone machine (Linux) with the intel compiler.
These are just notes to remember how I fixed some errors encountered while trying to port CESM 1.2.0 onto my new linux server.
In a previous post, I exhaustively outlined the process of setting up the CESM model version 1.2 to run in single column mode on a Mac running OSX 10.9.5 (i.e. Darwin) with GCC 4.9.2.
This post documents some errors I ran into along the way. If I find more in the future, I’ll probably make a new post instead of updating this one, so be sure to check for new posts here, if you are looking for solutions to CESM bugs. Continue reading
This post documents the method I used for building and running the CESM 1.2 on a Mac running OSX 10.9.5 (Mavericks). I also included some debugging notes for my own reference. This took several weeks of tinkering to streamline the process, so I hope this helps other researchers looking for a convenient way to run single column model (SCM) experiments. Continue reading
Some years ago I did a small project that involved running the NCAR Community Earth System Model (CESM) in a series of single-column model (SCM) experiments to test some ideas about the diurnal cycle of convection (or diel cycle). One of my graduate school professors, Dave Randall, has a nice explanation of single-column models, Continue reading