Pressure and Contour Lines
Below is the audio transcription of my earth science course lectures (some words may have been incorrectly transcribed by the software)
Understanding Hurricane Behavior and Economic Impact
So the interesting thing that we're finding about hurricanes is they aren't necessarily becoming stronger, but they are living longer, which again, we're talking about economic losses here, that a hurricane can persist over land. Usually the thing that kills a hurricane is when it tracks over land because it loses its fuel source. But we're finding that even when they move over land, they can actually stall out and just sit over land because they have so much resident fuel sitting in them. And we believe that's because of increased evaporation from the oceans. The more fuel you get into these hurricanes, the longer they can sit over land or the farther they can track into to land in places that typically wouldn't get it. And so we're the reason you're seeing that 1850 is because that's when we, I believe, began tracking them. So, yes, it's a long time frame, but we really want longitudinal data like that, and the more the better.
The Basics of Meteorological Maps
So this should be the last slide? Nope. So you may or may not have gone through the forms Stratus, Nimbus, Sierra, Stratus, all that. We're going to skip that and go straight into contour lines because you will see these on maps. And I know that this isn't riveting and exciting, but it is important to understand and it's useful because contour lines are used to show elevation, but we also use similar lines called ISO bars. We do that for pressure. We use ISO terms for temperature, deviation or temperature changes. And this is a contour map of the big island of Hawaii. So what you see here, clearly you can actually see the peaks of the two volcanoes. Also in this map, you can see where the lava fields are. The closer together these contour lines are, the steeper the terrain. So when we see these ones that are concentrated, the concentric line moving away from the center of the two peaks, you see that very steep slopes. And then as they run off, you start seeing like especially here, this is very evidently a lava field, this one right here, because you have a 1000 foot change in elevation for every drop drawn bar or contour line. But here you have an extensive distance between two lines, meaning that it's changing in a thousand feet over a very long distance, meaning it has a slow, slow slope. So this would be an area where volcano magma that emanates from these peaks starts drying. And we see that similarly over on this side where we get a slowing of the slope. But what you should notice is that the closer they are together, the steeper the terrain. And again, that's because we draw one for every thousand foot change in elevation. So you can see, especially right here, it is very steep on Monica. It gets pretty steep right here on Monolayer. And then we have another one right here. This may have been like a dead volcano. I don't know. But these are contour lines. And so you can often find contour maps to tell you what the terrain of a specific area looks like.
Understanding isobars and Wind Patterns
If we want, let's throw it all the way back to our maps, lectures. What type of map is this? Is it a thematic map or a reference map? Reference. It's a reference map because all it does is tell me where something is occurring, where a change in elevation is occurring, and that's pretty much it. Then we have ISO bars. I know this can look overwhelming, but if you ever for whatever reason, if you decide to change your major and go into the pilot program, this would be very important to you. But if not, I guess it's not very important. But we also draw lines similar to contour lines for pressure differences. And these are called ISO bars. We draw them for every four millibars, change in pressure. And on this map, what you can see here, you do see low pressures and high pressures as indicated by the letters. So you should be familiar with what those are. Blue H, red else. But what we can see around like a low pressure system is we actually can see where wind occurs based on where ISO bars are drawn. And the closer together that you have ISO bars, the higher the winds. And that makes sense. If we take a look at this high pressure system sitting over Arizona in this map, you'll notice that the next closest ISO bar is pretty far from it. I mean, we would expect that because high pressure systems bring moderate weather. It's not very windy. It's fair. It's pretty fair. The temperatures are pretty moderate. So we wouldn't expect there to be a lot of wind. Now, if we go over here and we look at this low pressure system that actually trudged through Utah back in September of 2020, you can see that there's ISO bars very closely drawn together. This is the one that brought those hurricane force winds to Davis and Weber County. If any of you remember, I think it also spawned some tornadoes. This is like the first week of September 2020. So you can see very close ISO bars. And as a result, we get very high winds and we're not going to get into this. But if you do take meteorology as a class, you'll learn what these flags mean. These are all pendants and the more markers you have on them, the higher the winds. You can see right here, if we go to the high pressure system over Arizona, we have a half a pendent, which means very low wind. But if you go here to where the low pressure system is, you have a full three pendants and a half and then two and a half right here. That means or indicates high wind. You can see two, four pendants right here over Colorado. So, again, closer they are, the more wind. You wouldn't actually even need the pressure designation if you could understand or if you do understand how these are drawn. This is a larger ISO bar map. You can see the low pressure system has the rings close together. This is over it near Saskatchewan. And then you have a high pressure system here over in the Gulf of Alaska where there's one ISO bar drawn around the entire thing. But you can see right here, very stormy weather all around these lows that tracked through Utah, causing those hurricane force winds. And again, this is a reminder a high has diverging winds clockwise and a low has converging winds in a counterclockwise pattern.