Most of us have to live on a budget. Think about your bank budget, how much money you have in the bank. What does that depend on? You have a job, we hope, maybe you have two jobs. That's money that comes into your bank account and when we think of just that part alone, of course your bank account increases, the money in the bank increases. But of course, there are expenses. Maybe it's the mortgage payment or the rent payment. You got to buy food and car payment, anything like that. Out here in Colorado, maybe you're buying recreational marijuana, who knows? In any case, those are basically deficits. That's money that's coming out of your bank account. If you look at the beginning of the month and you look at the end of the month, we can assess what the change in your bank account was if it was positive, that means there was simply more money coming in than there was going out. If it was negative, that change over the month is negative, which we hope it isn't, right. That means that there was more money going out than coming in. It's basically a budget is what we're talking about. We can think of an energy budget in the very same way. It's very, very analogous. It's just that we're dealing with different units of energy. We can think of energy budgets just like a bank account, just different units. So now let's use this concept to speak of the Arctic energy budget. Now, the key point is that a lot about how the Arctic works can be understood by studying its energy budget. What are the key elements of the energy budget of the Arctic? noting that these very, very much vary by season. One, an atmospheric energy flux convergence. There is energy coming in from lower latitudes by the atmosphere driven in considerable part, by our friend, the extra tropical cyclones and anticyclones. The top of atmosphere net radiation flux. What's the balance between incoming shortwave and outgoing longwave at the top of the atmosphere and something called the net surface energy flux. So now let's look at these and I put together this little schematic to try and illustrate the point. What we're going to speak about your think about is an atmospheric energy storage. How much energy is in the atmosphere versus, and also then, how much energy is in the ocean, the Arctic Ocean that lies below. So what we're thinking of here is an Arctic Ocean, from the top of the ocean, all the way basically down to the bottom, and think of a column of the atmosphere over the Arctic Ocean goes all the way to the top of the atmosphere. That's what we're talking about. The atmospheric energy storage in the ocean energy storage. Now, how do these things vary, what determines that energy storage and how it can change? Well, first of all, there's shortwave radiation coming down from the sun, from the top of the atmosphere, downward into the atmosphere. Well, there's also shortwave radiation going the other way, reflected back out into space both by the surface, by cloud, but scattering by oxygen and nitrogen in the atmosphere. Shortwave radiation going back out into space. There's also longwave radiation that is emitted upward from the surface and by the atmosphere. Now, other things going on. I mentioned this atmospheric energy flux convergence. This is energy coming in from the sides, from the atmospheric transport. So its heat in the sense of warm air coming in, also moisture coming in. Moisture actually represents energy because to get water vapor, we had to put energy into liquid water to evaporate it. So really water vapor, you think of that as energy as well. So that's an atmospheric energy convergence. Now, there's also shortwave down with a service. A lot of that shortwave radiation, it was not reflected by clouds, Things like that goes through the atmosphere and then is absorbed at the surface. But some of them that shortwave, as I'm just showing it by S-W here, is reflected back up. That's the surface albedo effect. Longwave radiation down, remember that the atmosphere emits radiation in the longwave because it has greenhouse gases, water vapor, carbon dioxide. So there's long wave down, but then there's also longwave radiation that is emitted from the surface upwards. A whole bunch of terms here, right? and there's more, there's actually several other terms here. I'm just calling it here. This includes things like melt, because it takes energy to melt conductive term that could be in here conduction. So I'm just throwing it in that other term. There's also an ocean energy flux convergence. That is heat coming into the north by the ocean. The atmosphere, that's where the big transfers of energy occur, but the ocean is also transporting energy polar. Remember this, that warm Atlantic water coming into the Arctic on the Atlantic side, well, of course, Atlantic water. But yeah, that's a big part of that ocean energy convergent. Lot of terms here. Let's simplify a bit though. Let's take the shortwave radiation down at the top of the atmosphere, add that to the shortwave radiation up, add that to the long-wave radiation up, and what do we get? Something we call the TOA, which is top of atmosphere net radiation. Net is just really say shortwave down, and we add that to the long-wave up. Shortwave down, shortwave radiation up, and the long-wave radiation up, it's the top of atmosphere net radiation. Now, let's look down below. Shortwave radiation down at the surface plus shortwave up, that's the reflected part, plus the long-wave down, coming from the atmosphere, plus the long-wave up emitted from the surface, plus these other terms, that's something called the net surface flux. What that is is the net energy exchange between the atmosphere and the underlying ocean. There's also, remember, still that ocean energy flux convergent that we had before. Now, let's look at what it looks like on an annual average basis, so averaging all the months together over a long-term. This is from measurements that we can take from satellite, from other sources. They're never perfect, but it gives us a good idea of what's going on. Top of atmosphere net radiation budget, about a minus 116 watts per square meter. That saying averaged over all of the area of the top of the atmosphere. We're talking about a domain here that is over the Arctic Ocean, at the top of the atmosphere, over that domain, per every square meter, about minus about 116 watts of energy that is going upward. Now, what this means is that there's more long-wave radiation emitted upwards than there is shortwave radiation coming down. That's what this is saying. Now, atmospheric energy flux convergence just about 100 watts per square meter. A little less than that, but just about 100 watts per square meter coming in from the sides. Now, ocean energy flux convergence, a much smaller term. You see in terms of that energy flux convergence big by the atmosphere is much smaller by the ocean, but of course it is very important what the ocean is doing. Now, the net surface flux, minus 16. What does that say? That means there's a transfer of energy on the annual average basis from the ocean into the atmosphere. So with respect to the atmosphere, that net surface flux acts to warm the atmosphere. The top of atmospheric net radiation is negative, the atmospheric energy flux convergence is positive coming in from the side, and there's some Some energy flux convergence. You put it all together, that yield, on the annual average basis, just about zero change in atmospheric energy storage, here it's minus 0.1. Now, remember this is real data, so it's got some errors in it. That is not bad, but we should think of it as a total completely stable climate. It should be right around zero. In other words, the atmosphere neither gaining energy nor losing energy, that's what we would expect. The real data I'm showing here that's about minus 0.1, I think what we're really talking about here is just errors in the data. Data are not perfect. Now, and the ocean energy storage about plus 0.3. So it saying in here, on an annual average basis, the ocean is warming a bit. Now again, in a steady-state climate, we'd expect that to be right around zero. Now, we know the ocean is in fact warming, but again, there's some errors in the data here, so it just shows you how hard it is to put these numbers together. Huge amount of work to put numbers like these together. Now, here's a question. Why is the top of atmosphere radiation budget negative as averaged over the year? The answer is the atmospheric energy transports bring in energy from lower latitudes. Remember there's this transport of energy from the atmosphere, from the lower latitudes into the higher latitudes, bringing in heat, what we sense as temperature, but also bringing in water vapor, and water vapor is a greenhouse gas. So the issue here is that the high latitudes really are warmer and moister in terms of water vapor than they have any right to be just given the amount of solar radiation they got. So because of this, the transport, there's more of a long-wave upward to space than you might expect just from the shortwave radiation that's received. So that is why it is negative. This is just a little illustration of this, looking at the net radiation at that the top of the atmosphere by latitude. What it's showing is that between zero and 30 degrees latitude in both hemispheres, I'm looking at the panel on the left, it's showing that the net radiation is positive. That means there's more solar radiation coming in than there is long wave emitted to space. But if we move into the higher latitudes to the opposite hold. There's less solar radiation received than in the lower latitudes. But because of those transport, the long-wave emission to space exceeds the short-wave gain. That's because of those heat transports by the atmosphere. If we average this altogether for steady-state climate, it should come out to about zero. But we see that it does not hold by latitude. That's the interesting thing about these atmospheric transports and what they do in terms of net radiation at the top of the atmosphere. Now let's look at the same thing here, these energy budgets, but let's just think now of what's going on in winter. Winter, we'll talk January. Essentially, no solar radiation. Top of atmosphere radiation budget strongly negative, no solar radiation coming in, big atmospheric energy flux convergent, big net surface flux from the ocean to the atmosphere, and a fairly modest ocean energy flux convergent. So I'll show some of these same sort here coming up for January that we can measure. Top of atmosphere net radiation budget pretty big negative, 177 or so watts per square meter. Atmospheric energy flux convergence, 123. Bigger than we would see in summer. We'll get to that in a moment. Ocean energy flux convergence, plus 21, fairly small but still significant. Net surface flux minus 59.9 or basically minus 60. That means there's a big transfer of energy from the ocean into the atmosphere. The numbers here are showing the atmospheric energy storage plus 5.9 or six. So it's saying that even in January, although it's cold, it's actually starting to warm up. That's what these numbers are really telling us. The ocean energy storage minus 14, so the ocean is losing energy. In January, ocean is losing energy, the atmospheric is gaining energy. So it's saying the ocean is cooling, the atmosphere is starting to warm up. Let's think of summer. Summer. So when you think of July, near the annual peak in solar radiation. Top of atmosphere net radiation budget slightly positive, smaller atmospheric energy flux convergent, big net surface flux from the atmosphere to the ocean, and a modest ocean energy flux convergence. So here we go again. Here we're going to go now look at July and look at these energy terms. Top of atmosphere net radiation budget slightly positive because what's happening here is yes, the atmosphere is losing energy to space. There's plenty of long-wave radiation out. But this is near the peak of solar radiation coming in. So in July, the effect of the solar radiation coming in slightly exceeds the effect of the long-wave radiation going out. Atmospheric energy flux convergence about 90 or 87, 88, something like that. Ocean energy flux convergence of about 21. Net surface flux of plus 94. What we're seeing is the atmosphere is gaining energy in July and what we're seeing is the ocean is also gaining energy. It makes sense. The ocean warming up in the summer, sea ice is melting, solar radiation penetrating into the ocean, warming it up. Now here's one question here. At what time of year will the atmospheric energy tendency tend to be the most positive? The answer is, in spring. We're talking about the tendency. What we're talking about is the change in energy storage. The change in energy storage is going to be most positive in the spring because the sun is rising higher in the sky, more energy coming into the surface, so the system is warming up. Now it'll tend to be at its maximum energy storage sometime in July, but at that time, even though the numbers here are showing that it's still gaining energy, the energy gain is not that big. Its really the biggest change is what we're going to see is in spring in terms of the positive change. In other words, in spring, that's when the system is gaining the most energy. We could ask the same question, when will the energy tendency be the most negative? In autumn, clearly. The sun is starting to set. So with that, I hope we learned a little bit about the Arctic energy budget and how it all works.
