I have been studying Arctic weather for at least three decades now. It continues to fascinate me. I think that fascination will probably come through as part of this video. key points; a lot of Arctic weather is linked to the passage of cyclones and anticyclones. In this sense, a lot of what we see in the Arctic is just like we have in the middle latitudes. Now, there are also a lot of local and regional phenomena such as blowing snow in winter, whiteouts in winter. You don't want to get caught in a whiteout if you don't know where you're going. In summer a lot of thunderstorms over there. Who would have thought it, thunderstorms in the Arctic, but oh yes, they're surprisingly common. Now, let's talk first about cyclones and anticyclones. Okay, so what is a cyclone? It's a low pressure system. In such a low pressure system in the northern hemisphere, the winds will tend to blow counterclockwise around that low. An anticyclone goes the opposite way; the winds tend to blow clockwise around an anticyclone. Now a cyclone, that's what we associated the passage of a cyclone, that's what we associated with precipitation and clouds because there are uplift mechanisms associated with warm fronts and cold fronts. Anticyclones, generally associated with good weather, not necessarily warm weather, can be quite cold under an anticyclone, but generally good weather. In other words, not a lot of cloud cover, we don't generally associate them with a lot of precipitation. Now I'm going to focus here on cyclones because there the more interesting of the two in my opinion, although it's nice to have good weather. But okay, first of all, why cyclones and anticyclones? This puts us to ask the question here of; why do we even have these things? They are basically nature's way of transporting atmospheric energy from warm, low latitude to cold, high latitudes. What happens of course, is that we have differential heating of solar radiation, by solar radiation. So the high latitudes are cold. The low latitudes are warm. You see that at the surface, you see that through a fairly thick layer of the atmosphere. What cyclones and anticyclones do is they try to get rid of that temperature gradient. Nature does not like gradients, so that gradient set up by the differential heating, there are mechanisms trying to get rid of that and that's really the role of cyclones and anticyclones. A cyclone, for example, transports warm air pole-ward and cold air equator-ward. Anticyclones turn out to be doing basically the same thing. Now here's a surface weather map. What we see on this surface weather map are a series of thin lines, those are called isobars, which are lines of equal pressure connecting equal pressure. Then you see those darker lines and some of them have barbs on them, some of them have half-moons on them. The half-moons are warm fronts and that's where warm air is advancing into colder air, transporting warm air pole-ward. What's happening in these situations is the warm air is rising over the cold air so that warm air cools and condenses, clouds form, precipitation may fall. The areas with the barbs, those are cold fronts and that's where basically the cold air is digging into the warm air, shoves the warm air aloft and that warm air cools and condenses, and precipitation may ensue. Now there's also areas we can see both barbs and half-moons together. That's what we call an occluded front. Now also what you see on here is some areas where there's mapped with the letters H and L. That means high pressure and low pressure; so cyclones and anticyclones. Also some numbers which are simply indicating the pressures within the middle of the cyclones and anticyclones. So here I'm showing by that arrow an anticyclone. So it's marked with an H. It has a central pressure of 1034. Pretty high, not terribly high, but reasonably high. Here's a cyclone that has a central pressure of 983 millibars and you can see a nice warm front and a cold front associated with this. Now this map is for the northern North Atlantic, so Greenland is kind of on the top left of this. Now I've mentioned warm fronts and cold fronts. So here's kind of a cross section of a warm front. The warm front is where the warm air is advancing into the colder air. That warm air rides above, rides along the surface of that cold air and it is forced upward or rises upward. It does so because it's less dense than the colder air. As it rises, it cools and condenses. Clouds may form, precipitation may ensue. Here's the opposite, here's your cold front, here's what the cold air is digging into the warm air. We have the advancing cold air, digs into the cold air. The warm air is more or less forced upwards, cools, and condenses, precipitation may ensue. Now here's a satellite image of a couple of nice cyclones near Iceland, is a satellite image and you see that nice swirly patterns. Look at the one on the right, you see that beautiful swirl. This is showing that generally counterclockwise rotation that you have with a cyclone. Now, let's look at a cyclone and a little more carefully. This is an idealized cyclone would it might look like. You see the L is marked, there's the warm front where warm air is advancing. There's the cold front where cold air is advancing southward, and you can see by the arrows showing the basic circulation. In the green there, it's showing where you're likely to find precipitation both along associated with the warm front and the cold front. Now, then the cyclone will mature. Here's a midlife cyclone. You see it's gotten a deeper or more pronounced circulation. There's your warm front and your cold front. Again, you see the counterclockwise rotation and the precipitation patterns fairly widespread. Then here's a mature cyclone which is what we call it getting towards the occlusion phase. When cyclones occlude, basically you can think of it as the warm front catching up with the cold front. That's marking the mature stage of the cyclone and then it's going to die out, because these things have a life cycle. Here's the question, how long does the typical cyclone live? The answer is 3-7 days. Some live longer, some don't live as long. Three to seven days is fairly typical. These things do have a life cycle. Now, this is a map I'm showing of winter cyclone frequency across the Arctic, which is a study I did all quite a few years ago. Don't worry too much about the numbers. The point being here is those areas with a dotted contours, that's a lot of cyclones and the areas that have the solid contours, that's where there's not so many. This was assessment of cyclone frequency, but just remember the pattern here. Now, this is for winter. What you see is, there's a lot of cyclones over the northern North Atlantic sector extending well into the Arctic. That's where you find them mostly. A lot of them in winter, you find them all across the Arctic in winter, but they're most common in that area. Number of reasons for that; there's strong temperature gradients in that region. You've got, for example, that cold a sea ice cover to the north and west contrasting with a warm, open waters on the east ocean waters, big temperature contrast. This is part of the broader feature called the North Atlantic storm track. One area we got quite a few cyclones is associated with a feature called the Icelandic Low, which we'll talk about shortly. Now, here's the pattern of summer cyclone frequency and you see it's rather different. There's still a lot of cyclones over that northern North Atlantic sector. You still see a lot of those dotted contours. But now you also see dotted contours over the central Arctic Ocean. What happens here? There's a lot of cyclones that are formed over the Eurasian continent, also within the Arctic Ocean itself, which move then into the central Arctic Ocean. Lots of cyclones there in the summer, not so many over the North Atlantic as in winter, but still quite a few. Now, let's look at this in terms of patterns of precipitation across the Arctic. Now, this is annual precipitation and what you'll see here is the largest precipitation amounts are over that Atlantic sector. Makes sense because there's a hell lot of winter cyclones there. There's still a lot of summer cyclones, not as many as winter, but still plenty of them. Cyclones, that's one of our key precipitation mechanisms. What you see over the Central Arctic Ocean is not much precipitation at all. It's in those yellows, very dry. It really a polar desert environment, despite the fact that you've got a lot of cyclones there in summer. Now it turns out summer, late summer, autumn, that's the precipitation maximum over the Central Arctic Ocean. But there's not a lot of moisture to work with there. High latitudes, the air is cold, so it's rather arid in that sector compared to rather moist over the Northern North Atlantic sector. Now let's talk about blowing snow and whiteouts. It's getting towards this more local, regional thing. Blowing snow; drifting, reduced visibility, definitely a travel hazard. Whiteouts; when you have low clouds and fog over a snow surface, you can get a whiteout. There's just no horizon, you can't see anything. It can be a very much a travel hazard. You have to be very careful what you're doing. You can find yourself walking in circles or taking a snow machine right over a cliff if you don't really know what you're doing, nearly done that a few times. Blowing snow. This is a photograph that my former adviser took of me years ago in 1982 on Ellesmere Island. I'm trying to read an anemometer there during this blizzard, wind was blowing pretty hard, but there's blowing snow, definitely a hazard. Here's just an example of a whiteout. This was a photograph that I took doing some work on the North Slope with my colleague Matt Sturm and others. We had a situation. We had a low cloud over a very white fresh snow surface and there was no horizon, no horizon at all here. Now, I took this photograph was an iPhone. What I discovered is an iPhone does not work well in this situation when you have a whiteout and also when the temperature is rather low, well below zero Fahrenheit, as I recall. I found that iPhones do not perform very well in that situation. So take that as a pointer next time you're out in a whiteout in sub-zero temperatures. Now, thunderstorms in the Arctic? Yeah, overland areas. You need strong surface heating, so that's why you find them overland areas, not the Arctic Ocean. But yeah, thunderstorms are surprisingly common, and of course, thunder and lightning. This raises a question. Most forest fires in the Arctic latitudes, are they human caused or not? The answer is no, false. They are not human caused. They are as a result of lightning. Some are human caused, but most are lightning. There's areas with the massive burns. I was up with [inaudible] a while ago near Yellowknife, Canada, that sort just huge fires are evidence of them. They were fairly frequent, but you have these huge forest fires in Arctic. Remember a lot of Arctic is forest. But yeah, lightning-induced. Arctic heat waves. I'll end with this. We've seen some crazy things in the Arctic in recent years. For example, in 2015, December 30, just before the New Year, an Arctic heat wave where temperatures at the North Pole reached the melting point, just unheard of. Why did this occur? It was caused by an unusually large transport of heat from the South associated with cyclones. Remember cyclones transport heat poleward, energy poleward, transport cold air poleward. Well, this was a case where we have seen the effects of one of several of them, as it turned out, I recall, transporting a lot of warm air poleward. Here's a map showing temperature anomalies for that time, departures from average. Focus your attention near the North Pole where you see that big red blob, those were where temperatures got to the melting point, basically December 30th, crazy stuff that we've been seeing things like that in the Arctic. I hope on this video you've gotten a little better appreciation for Arctic weather, something that's continued to fascinate me for years and I think it will continue to fascinate me until I retire, if such a thing ever happened.
