As is usually the case, one of the most basic questions in climate science has also been one of the most difficult to answer: How much energy is the Earth sending out into space? The pair of shoebox-sized satellites that comprise PREFIRE — Polar Radiant Energy in the Far-InfraRed Experiment — could very well provide the answer.
Principal investigator Tristan L’Ecuyer, a professor in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison and the director of the Cooperative Institute for Meteorological Satellite Studies, spoke with Heatmap about PREFIRE. Tentatively scheduled to launch in May, the project stands not only to make future climate models more accurate, but could also help shape a new generation of atmospheric exploration.
The interview has been edited for length and clarity.
Could you tell me a little bit about your research and the work that you do?
A lot of our climate information comes from models — where I come in is trying to make sure that those predictions are rooted in actual observations of our planet. But it’s impossible to cover the whole globe with a temperature sensor or water vapor [sensor] or those sorts of things, so I’ve always focused on using satellite observations, and in particular I’ve been focusing on the exchange of energy.
Basically, what drives the climate is the incoming energy from the sun and how that’s balanced by the thermal energy that the Earth emits. One of the big influencers of that balance are clouds — they reflect the sunlight, but they also have a greenhouse effect of their own; they trap the thermal energy emitted. So I’ve spent most of my career trying to understand the effects of clouds on the climate and how that might change if the climate warms.
And what’s the goal of this particular mission?
One of the fastest changing regions on Earth right now is the polar regions — I think a lot of people are aware of that. Normally, the polar regions are very cold — they reflect a lot of sunlight just because of the ice surface. But as the ice surface melts, the ocean is a lot darker than ice, and so [the poles] can actually absorb more of the solar radiation that’s coming in.
A lot of people say, “Well, okay, but that’s the Arctic. I don’t live there.” But the way the climate works is that in order to create an equilibrium between these really, really cold polar caps and the really, really warm tropics. It’s just like heating the end of a rod — the rod is going to transfer some of the heat from the hot end to the cold end to establish an equilibrium between them. The Earth does the same thing, but the way it does that is through our weather systems. So basically, how cold the polar region is versus the equator is what’s going to govern how severe our weather is in the mid-latitudes.
What we’re trying to do is make measurements of, basically, how that thermal energy is distributed. We just have a lack of understanding right now — or it’s more that the understanding comes from isolated, individual field projects, and what we really want to do is map out the whole Arctic and understand all of the different regions and how it’s changing.
How do you expect your findings to influence our climate models? Or how significantly do you expect them to affect the climate models?
This is quite unusual for a satellite project, we actually have climate modelers as part of our team. There’s the people that take, for example, the Greenland ice sheet, and they model things like the melting of the ice, how heat transports into the ice sheet, how the water once it melts percolates through the ice and then runs off at the bottom of the glacier, or even on top of the glacier. And then I have a general climate modeling group that basically uses climate models to project future climate.
There’s two ways that's going to happen. The first is we’ve developed a tool that allows us to kind of simulate what our satellite would see if it was flying in a climate model as opposed to around the real Earth — we can simulate exactly what the climate model is suggesting the satellite should see. And then of course, we’re making the real observations with the satellite. We can compare the two and evaluate, in today’s climate, how well is that climate model reproducing what the satellites see?
The other way is we’re going to generate models of how much heat comes off of various surfaces — ice surfaces, water surfaces, snow surfaces — and that information can be used to create a new module that goes right into the climate model and improves the way it represents the surface.
So what do these satellites look like and how do they work?
Our satellite is called a CubeSat. It’s not very big at all, maybe a foot wide, a foot-and-a-half or so long. There’s a little aperture, a little hole on the end of the satellite that lets the thermal energy from the Earth go in, and then the the rest of the satellite is basically just this big box that has a radio and a transmitter. In total, I think the whole thing weighs about 15 kilograms.
Because it's relatively small and relatively inexpensive, we're actually able to have two of those instead of just having one, and what that lets us do is put them into different orbits. At some point that will cross and see the same spot on the ground — let’s say somewhere in the center of Greenland — but up to eight or nine hours apart. Let’s say it melts in between, we’ll be able to understand how that melting process affected the heat that was emitted from the surface into the atmosphere.
How big of a deal do you think this is? Or how big of a deal do you think it could be?
There’s more than a couple of aspects to this. To really segue from the last question to this one, the reason [the satellites are] inexpensive, it’s not that they’re low-quality. It’s actually because they’re very uniform sizes and shapes. You can mass produce them. And so it’s that fact, coupled with the fact that we can now do real science on this small platform. We’ve been able to miniaturize the technology. If we can keep demonstrating that these missions are viable and producing realistic science data, this could be the future of the field.
Coming back to the polar climate, we absolutely know that the poles are warming at a very alarming rate. We know that the ice sheets are melting. We know that this has implications for the weather in the lower latitudes where we live, and for sea level. But when you try to predict that 100 years from now, there’s quite a range of different answers, from very catastrophic to still pretty bad. Depending on which of those answers is correct, it really dictates what we need to do today. How quickly do we need to adapt to a rising sea level, or to stronger storms or more frequent storms? After this mission, we will be able to improve the climate models in such a way that we’ll have a narrower range of possibilities.
The other thing that’s exciting is also just the unknown. There’s always new things that you learn by measuring something for the first time. We might learn something about the tropics, we might learn something about the upper atmosphere. There are some people in mountainous areas that are quite interested in the measurements — at the top of mountains, it’s actually quite similar in climate to the Arctic. So I’m also really excited about what happens when the science community in general explores that data for the first time.
