Author Archives: Walter

A New Graphic for Explaining E3SM-MMF

When I explain the concept of a multiscale modelling framework (MMF), or super-parameterization, I often find it helpful to show a picture of what it “looks like”. There’s a few classic images for this that I’ve used for years. Here’s one of the original images commissioned by CMMAP:

And here’s a more recent one commissioned by the Exascale Computing Project to develop E3SM-MMF:

And now I have this fancy one that I made with ACTUAL data from a E3SM-MMF run:

This is an instantaneous output from a run where I made the CRMs a bit higher resolution than normal to make it look nicer. The surface shading is the precipitation rate, and the shading within each CRM is using the cloud liquid and ice tracers.

I’m a bit embarrassed to share the code that I used to make this… it’s very convoluted… but I’m happy to share if somebody actually wants it.

Also, feel free to use any of these images for… whatever.

Overdue Updates for 2019

So it’s been awhile since I’ve posted any updates, and that’s partly because I’ve been busy/lazy, but also because MY WEBSITE GOT HACKED! It was a very frustrating experience. Since I’m cheap and I like DIY projects, I decided to try an manually clean up the code. Most of a wordpress site is written in PHP, which I actually learned a bit about in college but I don’t remember much of it. It was a good learning experience and I’d encourage anyone in a similar situation to try it out before paying a big company to come in and fix it for you.

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Should We Give Climate Skeptics a Platform?

I was recently interviewed for an article at the Daily Beast by Bahar Gholipour. She had recently been forwarded a press release from Peter Ward about an upcoming talk at the 2018 meeting of the Geological Soceity of America about his “ground-breaking” research showing that the common understanding of the greenhouse effect is wrong. This is, of course, ridiculous, and she found my previous post on Peter’s ideas and wondered what I thought about whether we should really be accommodating to people like him.

Why Is a Climate Change Skeptic Headlining Science Conferences?

I think this is an excellent question that I’ve thought about it quite a bit. I really like the discussion in the article. There’s a clear distinction in the article that his ideas are clearly misguided, and the discussion nicely focuses on the central question of how and why these ideas are given a platform. 

To answer the central question plainly, I think that people like Dr. Ward should be given a platform at conferences. However, in the specific case of Dr. Ward, he has repeatedly failed to support his claims with concrete evidence, and we should NOT give valuable conference speaking time to people who do not adhere to the scientific method. 

Giving time to climate skeptics may feel like a painful waste, but it’s the fair and professional thing to do. This is assuming that they are civil, respectful, and open to criticism of their fringe ideas. The tendency of scientists to eviscerate each other’s work means that conference talks about potentially paradigm shifting ideas will invoke well-informed and thoughtful challenges, which you won’t get from personal blogs or social media. Being able to adequately address these challenges is critical for moving a fringe idea into mainstream acceptance. 

Notes on Eddy Vorticity and Eddy Enstrophy budgets

I was going through some stuff today and found these notes I typed up a couple years ago on the derivation of the “perturbation enstrophy budget” that I never posted! So I’m putting them here now in case anyone is stumbling around the internet looking for such things. I also wrote up some notes on the “perturbation potential enstrophy budget”, which is pretty interesting, but I can’t find them. Maybe in another year I’ll stumble on them too! Continue reading

Friday Fun with GPM Rainfall Animations

I recently realized that the data from the relatively new Global Precipitation Measurement (GPM) satellite can show incredibly fine detail! The spatial resolution is 0.1×0.1 degrees and its available at a 30 minute temporal resolution! This is particularly exciting because lately I’ve been doing some very fine grained analysis of a model with a 30 minute timestep, so this allows a very direct comparison between the “real-time” weather in observations and a model. Today I made some animations of GPM data and just wanted to share. The animations below are from January 1, 2017. This choice was arbitrary, there’s nothing special about this date that I chose. Note that the swath of the GPM data can’t cover the whole globe every 30 minutes, so the swath data is blended with other satellite data to make the IMERG data that was used here (The specific IMERG variable here is “precipitationCal”). This sometimes results in some funny looking artifacts or clouds that don’t seem to move in a natural way. Continue reading

de Roode et al. (2012): Parameterization of the Vertical Velocity Equation for Shallow Cumulus Clouds

I’ve been stewing on an idea to build a convective parameterization for a couple years, but there are a lot of issues to work out so I’ve been trying to study up on how other parameterizations work. The biggest issue with a convective parameterization always seems to revolve around entrainment. In reading about recent parameterization developments, like Chikira and Sugiyama (2010), many people seem to like the idea of relating entrainment to the vertical velocity of the cloud updraft. This is not a new idea, but it has taken awhile to be utilized in weather and climate models. The paper discussed below provides a great discussion of this relationship, and I was surprised to learn that it is based on an inaccurate assumption about how important entrainment is for cloud momentum.

de Roode, S.R., A.P. Siebesma, H.J. Jonker, and Y. de Voogd, 2012: Parameterization of the Vertical Velocity Equation for Shallow Cumulus Clouds. Mon. Wea. Rev., 140, 2424–2436.

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What is Super-Parameterization?

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

House Committee Hearing on Climate Science (March 29, 2017)

This morning I listened to the recent hearing on climate science for the house of representatives committee on science, space, and technology. I found the exchange very fascinating. I was disappointed to hear the naive questions coming from the representatives. Some are still touting the myth of the cooling predictions in the 70’s.  Another congressman seemed to be on a witch hunt by aggressively asking a panel witness to prove that he wasn’t part of the union of concerned scientists. Aside from the conduct of the representatives, I wanted to share some thoughts about the conduct of the panel.  Continue reading