What’s the weather doing? Is it going to rain today? How much? What about temperatures? We depend on modern weather forecasting, thanks, in part to the vast network of weather satellites. What instruments do they have, what orbits do they use.
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National Oceanic and Atmospheric Administration
Geostationary Satellites – GOES series
Polar sun-synchronous satellites EUMETSATs
Himawari (????, “sunflower”) geostationary satellites
Transcription services provided by: GMR Transcription
Fraser Cain: Astronomy Cast Episode 461: Measuring the Weather. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain. I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, the Director of Technology and Citizen Science at the Astronomical Society of the Pacific and the director of CosmoQuest. Hey, Pamela, how’s it going?
Dr. Pamela Gay: It’s going well. How’s it going with you, Fraser?
Fraser Cain: It’s going really well. And this is very well timed, I think, now that we’ve been seeing all of this crazy weather coming our way. So, we’ve got a special two-part episode about the weather, which is gonna be a lot of fun.
Dr. Pamela Gay: And this is one of those episodes that really came out of Susie asking me, “So, what should we have as a show topic?” while I was looking at a website that was like, “And a hurricane is headed towards Ireland,” which is not where hurricanes normally go, and it was just sort of like –
Fraser Cain: Is that even possible? Wait, a hurricane going to Ireland?
Dr. Pamela Gay: Yes. Yes, I’m looking at its track right now, and what’s kind of amazing to me, which is why we’re doing the particular two-parter we’re doing right now, is when Hurricane Ophelia first spun up as a tropical depression and then a tropical storm out in the Atlantic, it looked like it was just gonna do this little corkscrew out in the middle of the ocean and harm no one. And then, they showed it increasing to a Category 1, but it showed that it was never gonna get stronger than a Hurricane 1.
And then, I woke up yesterday to a notification on my phone saying that it had become a Category 2, and when I first looked, it was like, “And it shall never be a Hurricane 2 past this point.” And I’m now looking at the model, and it’s been a Hurricane Category 2 for quite some time, but as it has, every time I’ve looked at this page since this little hurricane spun up, the next weather model’s like, “And it shall become a Category 1,” and I no longer believe it. I no longer believe it.
But, yes, its track is straight on track to hit Ireland.
Fraser Cain: And I don’t know much about the weather, but as I recall, hurricanes form off the coast of Africa, or perhaps down in the Gulf, travel across the Atlantic Ocean, and smash into the Caribbean, the East Coast of North America, or they form out in the Pacific Ocean and smash into the coast of Asia. They don’t go the other way.
Dr. Pamela Gay: Yeah. So, the Azores actually have a hurricane/tropical storm advisory. The Azores are islands off the coast of Portugal. They have weather alerts in Portugal and Spain. And this is the kind of Atlantic hurricane that normally just doesn’t get seen, but has led to lots and lots of asterisks in the weather saying, “This could have happened in the past, but we wouldn’t know because, when it happened, there weren’t satellites.” So, we’re gonna talk about satellites.
Fraser Cain: Awesome. And I didn’t even do my intro. Here we go. What’s the weather doing? Is it gonna rain today? How much? What about temperatures? We depend on modern weather forecasting, thanks in part to the vast network of weather satellites. What instruments do they have? What orbits do they use? Tell me more.
Dr. Pamela Gay: So, where would you like to start?
Fraser Cain: So, let’s talk about what is the modern suite of weather satellites. What is up there right now?
Dr. Pamela Gay: So, you and I, here in the Northern American continent, are overseen by satellites that have been put up by NOAA and NASA, and these satellites are in two different kinds of orbits. We have satellites that are in geostationary orbit, and just sort of hang out directly above the earth’s equator a bazillion miles up, and just stare at one point all the time.
And then, the other kind of satellite that we have is a polar-orbiting satellite that comes across the exact same sun-incidence angle on the surface of the planet every time it orbits around the earth. These are much lower. They have much higher resolution imagery. And because they constantly see the planet at the exact same sun-planet angle, you end up with things like they get referred to as the “afternoon satellite” because that’s the orbit it’s on is to see the earth in the afternoon.
Fraser Cain: So, about how many of them are there?
Dr. Pamela Gay: For us, we currently have five up in orbit. These are the GOES satellites. But all different nations have all different satellites, so the entire planet ends up, basically, swarmed with these polar orbiters and these geostationary orbiters, and since each of them is interested in their own special places, the geostationary ones were pretty good about keeping out of each other’s way, but the polar orbiters… What’s cool is the polar orbiter that works for you and I works for both you and I because as the planet rotates, we, at different points, come out underneath the spacecraft. The polar orbiters sweep out the whole world, and there’s a bunch of them up there, so you never quite know who it is that’s looking down.
Fraser Cain: That doesn’t sound insidious and creepy. They’re there to help.
Dr. Pamela Gay: They are there to help.
Fraser Cain: They’re there to help you forecast the weather, and that’s a good thing.
Dr. Pamela Gay: It is.
Fraser Cain: So, what is on a typical weather satellite? What is the suite of instruments that they’re using to analyze the earth?
Dr. Pamela Gay: So, the ones that we’re most familiar with – because these are levels that we can readily turn on and off in Weather Underground, Weather.com, whichever suite of software that you’re using to look at the weather – the ones we’re familiar with are we’re going to look at the same wavelength that your eyeballs see. This is the visual imagery that you see of the earth.
Other ones that we use are infrared. This is where we look down at the planet and can start to tell what is the temperature. What’s cool is once you start looking at temperature, you can start to see different ocean currents because the water that’s in a current will be a different temperature than the water that’s just hanging out at a given latitude.
So, we have this whole suite of different visual bands and infrared bands.
Now, beyond that, it’s cool to be able to see things in visual and infrared, and that’s what a strictly weather satellite does, but we also have environmental satellites, and environmental satellites can get used for the weather, but they get you a whole lot more information as well. They start to look at how the atmosphere reflects light of different wavelengths in ways that tell us where is the atmosphere filled with different aerosol chemicals, so this is where we can start to see the ozone, the problems with the ozone. We can see smoke layers as compared to cloud layers. We can see smog, sulfur streams in the atmosphere. We can also start to get at what is the wind speed from different reflective capabilities. This is where Doppler and microwave starts to matter.
Fraser Cain: Before the episode, we were just talking a bit and saying just how good the weather system is now. I don’t know about you, but a lot of people out there, like I’ll be somewhere now and I can start to depend on what my phone says, and here on the West Coast, we definitely wanna know when it’s gonna rain, which is all the time. But, still, we look at the weather, and it’ll say like, “Oh, it’s not gonna rain until 3:00, and then it’s gonna start raining, but then it’ll be done around 5:00.” Before, I just knew it was all worthless, you know what I mean? You’re just like, “Pfft, forget it.”
Dr. Pamela Gay: Yeah, you lived on the West Coast. Me, growing up on the East Coast, we were pretty good.
Fraser Cain: But did you really used to depend on weather forecasts, or did you just go, “Well, he was wrong again,” talking about the weather forecaster?
Dr. Pamela Gay: I was one of those children that would look at the weather and decide if I really had to do my homework or not.
Fraser Cain: Why? Because you thought you might get a snow day?
Dr. Pamela Gay: And I often did.
Fraser Cain: And you often did, but I’m sure that went catastrophically wrong.
Dr. Pamela Gay: It didn’t, and this is what is amazing in how our satellites have changed over the years, is every few years, we add the ability to get more and more information, and this comes with the upgrades in what satellite systems that we’re using. So, we’re currently using the GOES satellites, which I often make fun of because they don’t always rename them as quickly as one would wish, or they refer to them in strange different ways. So, there is the GOES-R Series of spacecraft that get referred to as GOES-R. Then, there are some of them that, depending on what orbit they’re in, are referred to as GOES-E or GOES-W because of east and west. There’s occasionally a GOES-S.
And when they’re still being built, they all have letters. So, they recently constructed one that, while it was being built, was called GOES-P, and the second it hit orbit, they renamed it after a number.
Fraser Cain: What? Why? I don’t understand.
Dr. Pamela Gay: So, anyways, this particular series of satellites was able to totally get my attention by the crazy system they have for referring to them. And GOES is, of course, an acronym because it’s a spacecraft, so of course it has an acronym, and in this case, it’s Geostationary Operational Environmental Satellite, so GOES. And there’s a whole suite of them that have a variety of different orbits, a variety of different instruments, and the instruments they have on them have changed over the years.
And so, now, we have them that they have imagers. They have spectral suites. They have the ability to detect x-rays, to detect ultraviolet. They do lightning mapping, so when you see those weather layers that show all the little flickers of where lightning has happened, that’s getting measured by a satellite. They have magnometers on board so they can study the interplay between the solar radiation, the earth’s magnetic field.
And this is what they do today, but each of these different instruments suites have gotten updated over the years. So, the situation that we’re in right now is we have a bunch of them up there. They keep some in storage in case one dies. They keep some going all the time. And so, what we have right now is GOES-15 is in the GOES West location because they have to make you giggle while they go over the names. They have GOES-13 is in the GOES East position.
And where things get sad and where satellite isn’t always enough is there’s also a GOES South position that used to always be occupied by a spacecraft, but we had a spacecraft die, as they sometimes do. So, GOES-10 was decommissioned in 2009, and initially, the GOES-12 took over for it, but then it was retired in 2013, and now there’s no one living in the GOES South position, and so we’re missing a set of data.
Fraser Cain: Well, there’s people living there. There’s just not a satellite living there.
Dr. Pamela Gay: Yeah. So, we have an East Coast satellite, we have a West Coast satellite, and we currently have nothing in the southern position. And what this essentially means is we’re not getting all the data we used to get. So, there’s this brief period, up until 2013, when we had the modern satellite design, we had all the instrumentation, we had all the satellites in all of the spaces, and that was when we were able to do the amazing forecasts for the Snowmageddon that happened on the East Coast. We were able to do these amazing forecasts for all the nor’easters that tried to bury New England.
And now, you’ll notice, the past couple of years, the forecasts just haven’t been quite as reliable, and it’s because we’re missing a satellite.
Fraser Cain: But for a certain region.
Dr. Pamela Gay: But the thing is, you need to have the data from all of the regions. And this is actually what started me down this particular rabbit hole is growing up on the East Coast, I had all of the weather stations from where you were on the West Coast all across North America that were doing ground-truth data. Some of those stations actually report their data up to the satellites, and then it all gets sent down together. And all of this data from all across the landscape would go into the models where I grew up. But where you grew up, there’s a giant ocean to the west of you, and it’s out of that west that your weather is coming.
Fraser Cain: It sure does.
Dr. Pamela Gay: Yeah. And nowadays, we have better infrared imagers that are able to better take into consideration thermal models of the ocean. We have better models that can better study the interplay between that ocean and the atmosphere, but that’s the next episode. And by having better satellites, better instrumentation, more data that wasn’t there when you were growing up, and there weren’t the manmade weather stations in schools and farms, and so you had insufficient data to correctly forecast whether or not you were going to have a snow day.
Fraser Cain: Right, because there was nobody out there in the Pacific watching the storms come across the Pacific to reach us, while people in other parts of the country, for example, you could see the weather systems coming down from the north or coming from the east as necessary. So, yeah, maybe that’s why my childhood was hilariously wrong weather.
Dr. Pamela Gay: This episode of Astronomy Cast is sponsored by Away Luggage. Visit AwayTravel.com/Astro, and use the promo code ASTRO to get $20.00 off your suitcase purchase.
Now, any of you who have been listening to the show for a while know that I travel a lot, so when Away asked if we’d like to try out one of their suitcases, I said yes because I’m always on the lookout for the perfect suitcase, and the one thing I don’t have is a hard-top, hard-side piece of suitcase because I just haven’t found one that I liked before, and I think I finally did.
There are two things that I look for when I’m buying luggage. One is a lifetime warranty because I know I’m going to put the suitcase through all forms of trouble, and this one has that. The other thing I look for is something that’s lightweight, and most of the time, when you’re looking at hard-sided luggage, you’re looking at something that weighs a lot, and the Away Luggage does not.
When I first got this, I was like, “Ooh, maybe I shouldn’t sit on this. Maybe it’ll break.” No, it’s fine. I have sat on it. I’ve sat on it on its side. I’ve sat on it standing up because when you’re waiting in line, you want something to sit on sometimes, especially when you’re really jetlagged. This is rock-solid, lightweight, with-a-lifetime-warranty suitcase, and on top of that, it has built-in locks.
It has a built-in battery, which batteries are kind of a must-have nowadays when traveling, and the battery built in to the suitcase, first of all, can come out, so when you’re going through China or something, you’re good. It has you covered. You can remove the sucker and make it through security. But the other awesome part is it can do that 2.1-amp iPad I carry.
Anyways, Away Luggage, go to AwayTravel.com/Astro. Get a bag in whatever color you want. I got CosmoQuest burgundy. Promo code ASTRO during checkout, and you can get $20.00 off a suitcase and have something to sit on while waiting in line, just like I now have. Thanks a lot, Away.
Fraser Cain: So, you talked about this missing satellite then. Are there plans to fill this hole?
Dr. Pamela Gay: We’re launching another satellite in December. And so, the open question that we’re waiting to find out is when the new GOES satellite goes up in December, will, as it takes the position on – I forget whether it’s the East Coast or the West Coast – will the satellite that’s currently stationed in one of these must-have positions, will it get redirected into the GOES South position, or will it get put into a standby orbit and held to be used later if it’s needed.
Fraser Cain: Now, you’re talking about the GOES satellites, but that’s only a chunk of the earth focused on, say, one continent, one hemisphere, but there is other parts of this planet. So, there’s other weather satellites focused on other parts of the world.
Dr. Pamela Gay: And here, again, each nation has their own satellites. They do not have equally well-discussed-on-the-Internet satellites, and this, we have to say, actually, thank you to the US government for spending so much money on education and public outreach because NOAA and NASA have both been able to dedicate time and money to explaining on the Internet what it is that their satellites do.
Now, with Russia, we have the Elektro satellites, which operate out over the Indian Ocean. The Japanese have their MTSATs, which are out over the mid-Pacific, and – I’m gonna mispronounce this, but it wouldn’t be an episode of Astronomy Cast if I didn’t mispronounce something – the Himawari are out at 140 degrees east. Europeans have the Meteosat series of satellites. And China has the F?ngyún series of satellites. And finally, India has INSAT.
Now, if you’ll notice, there are only North Hemisphere satellites listed there. Now, the nice thing about geosynchronous is that since they’re up over the equator, the whole globe is sharing these satellites, and it just turns out that the nations able to launch them right now are North Hemisphere nations.
Fraser Cain: So, as you said, the NASA stuff, the NOAA stuff, that’s all just online. Anyone can go anytime they want and see the stuff in pretty much real time. I was sort of demoing this. You can go to certain pages. You can scroll your mouse wheel and just push the weather back and forth, which is really cool. They’ve mapped the weather onto the classic blue marble, so it’s more of a simulation, but still, you can see what the weather’s been doing. Thanks, NASA, for making all of that material available in real time to the public.
Is there sharing? What is the level of availability and accessibility for this kind of stuff?
Dr. Pamela Gay: So, in general, there are two different kinds of satellites. There’s military ones, which, because they’re military, we don’t really know anything about. But then, the public satellites are largely globally shared. This means that the GOES data gets used by everyone. The European Meteosat data gets used by everyone. And because we’re sharing, it’s leading to better models because the Europeans have their own hurricane models, the US has its own hurricane models, and we’re all working on the same data, and we can focus on the maths because we don’t have to focus on getting the data. So, this is super useful.
And then, with polar-orbiting satellites, we’re even in a different position because it turns out that the polar-orbiting satellites, because they’re closer to the planet, because they’re on a much shorter orbit, they’re actually seeing the whole planet two times a day as they go zipping around and around and around. So, we don’t even need quite as many of those.
Fraser Cain: So, it’s really important to understand the distance of these geostationary satellites. Because the way it works, you’ve gotta be tens of thousands of kilometers away from the earth.
Dr. Pamela Gay: It’s basically 36,000 kilometers or 22,000 miles.
Fraser Cain: And that’s far. When you think about where the International Space Station is, they’re only about 500 kilometers above.
Dr. Pamela Gay: 240 miles.
Fraser Cain: 240 miles, yeah, so it’s 300 and – I forget – 50 kilometers. Anyway, so, they’re not very far away, and so they get that big, beautiful view of Planet Earth, while those satellites that are out of the geostationary orbit, they’re 20 times, 50 times farther away, and so they’re just not getting the same kind of resolution. They’re not seeing the same kind of weather, the smaller formations that are happening inside, and that’s why these polar satellites are so valuable.
Dr. Pamela Gay: And the polar satellites, they’re higher up than the Space Station, but they’re still close enough to the earth that they can start to see things like if there is a large flock of fishing boats out off the coast of Japan, they easily turn up.
So, here, what we’re looking at is NOAA has a series that are conveniently named NOAA-17, 18, 15, whatever. They’re just NOAA satellites. That’s easy. Europe has the MetOp and EUMETSAT. I’m not sure how people say that one. And then, Russia has the Meteor and Resurs series satellites, and China has the ever ineloquently names FY-3A, -3B, -3C. And India has some that I don’t know the names of.
And so, again, it’s the same sets of nations. It’s India, Europe, China, the United States, and Japan has their geostationary satellites as well. And as they’re up there orbiting the entire planet, sending the data back, because these satellites are only 850 kilometers up, they do have that much, much higher resolution imagery.
Fraser Cain: And there are actually some really fascinating orbits. We did a whole episode on orbits a long time ago. But with the polar orbits, you can pull off kinds of orbits that sort of mimic a geostationary orbit by using this really funny elliptical orbit and sort of coming into the earth while the earth is turning, and be in the sky for quite a while before having to swing around the earth.
Dr. Pamela Gay: Those get used for communications, but they don’t actually get used for weather. With weather, they always do sun-synchronous orbits. So, these are orbits where they actually refer to them as morning orbits, afternoon orbits, where the sun is always at the same angle relative to the planet, and this allows you to always see shadows the same way, so that when you have a difference from one image to another, it’s not because the sun moved. It’s because the coloration on the surface of the world changed. So, if farmers’ fields appear significantly darker from one image to the next, they probably got soaked in a rainstorm. If you see a brightening of the surface, that’s either frost or snow or water that’s reflecting sunlight.
And so, with the polar orbits always being sun-synchronous, it gives you the ability to see things on a much more regular cadence than you would get with the communication satellite orbits, and it allows you to not have to worry about the chaos provoked by shadows.
Fraser Cain: So, I always like to give you the blank check, and you get to go and purchase some future weather satellites, future weather imaging capability, measuring capability. What would you like to see? Especially if there was like a decadal survey, what kinds of things do you think the scientists are looking for?
Dr. Pamela Gay: So, if I were given an unlimited budget, what I would want is a whole series of the advanced GOES satellites that are evenly spaced around the planet, every 20 or 30 degrees around the planet, allowing us to get this continual monitoring with the entire instrument suite and then have a morning, noon, evening, midnight – so, have basically those four different timeslots for the polar-synchronous orbits so that we have constant suite of data coming in, even spacing, get symmetric identical coverage because this is what makes computers so much happier.
One you’re able to start getting even coverage of the entire planet, you start being able to do models that take into account all the different things happening in the world. As we mentioned at the beginning of the show, hurricanes originate as hot air coming off of Africa, and so we need to understand what’s going on in Australia to be able to keep track of the Pacific El Niña, and we need to be able to keep track of the currents in the Atlantic to be able to understand when is a storm going to stall out. So, we need all the data, all of it. I want all the data.
Fraser Cain: All the data.
Dr. Pamela Gay: All of it.
Fraser Cain: I think about the upcoming SpaceX Elon Musk 4200 communication satellite constellation that could go up when the big freaking rocket launches, and think about the weather and just earth-observing capabilities of those things could provide in addition. It would be a mind-bending capability of a weather network as well.
Dr. Pamela Gay: And what we really need to do is start thinking more in terms of how can we create a network of satellites so that it’s accomplishing multiple different purposes. It was actually the early weather satellites that were used for global positioning, and it was just a test. It wasn’t highly accurate, couldn’t be used to test the innermost details of relativity, but it was proof of concept.
We have the ability to double up what these satellites are used for, the same way we currently double up that they can be used to check for emergency transponders. And by having this grid of emergency responders, satellite weather data, coming in, and this means that we have communications, we have position, and we have weather, and these are all public services. And if we can have the combined network that takes care of us for all these different things, it really starts to put us in a safer world.
Fraser Cain: Well, here ends Part 1. Part 2, we will be talking about putting those satellites to work predicting the future.
Dr. Pamela Gay: Thank you.
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Duration: 30 minutes