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Diablo Wind 10/26 Asynchronous School

Show Transcript October 26, 2020 Good morning students, This week in Northern California we have the Diablo Wind. This is our windiest time of the year. This is also our time with the greatest risk of fire. We haven’t had rain in months. We are extremely dry. PG&E is planning to shut off power to lots of areas that they are worried about power lines with winds sparking wildfires. This is how the Diablo Wind happens. We’ve talked about the change in seasons before. As we move from the summer months to the winter, our angle of Earth to the sun changes. Instead of leaning in at 23.5 degrees, we are starting to lean away, so the northern hemisphere gets less direct rays of sunlight. That means we heat up the land and water less, because there is less heat input. For the land, this cooling happens rapidly. Almost overnight, all of that heat absorbed is gone. A few days of cooler temperatures and we stay cool. The ocean is made of water. Water is slower to react. It holds on to it's heat for much longer, which means it will be drawing the cold air toward it. That creates an upward pull of air off the coast. Where is that air going to come from? It comes from someplace that’s colder. Someplace that isn’t rising as quickly. Notice my oatmeal. You can see the mountain peaks have concentrated the rising heat, so they draw the wind from places with less heat. Now over in Nevada, we have the Great Basin. This is a big flat desert area that is cooling down. As the air from the higher atmosphere cools, it drops down closer to the ground. It is drawn over the mountains, across the warm central valley, past Mount Diablo, across another range of smaller mountains, and into the ocean, where it rises again as it is warmed. Now look at this model of an ice cube melting. The cold water sinks because it is less dense that the water around it. Now look at this demonstration. I put two drops of food coloring in the jar, so you could tell what came from which side. I set the jars on two mugs. One with ice water, and one with hot water. The hot water is transferring it's thermal energy to the water in the jar, causing the red dye to rise up the side of the jar. But look- the blue dye is creeping across the bottom to follow that same path. The warming water on the red side needed to be replaced by something, so it pulled in the water from the blue side. When the warmed water rises to the surface, away from the heat source, it cools again, and starts to sink. PG&E Outages https://pgealerts.alerts.pge.com/outa... Diablo winds can feed Northern California fires. Here's how they form https://www.latimes.com/california/st... Earth wind patterns https://earth.nullschool.net/?fbclid=...