Clouds from Both Sides
Monday, September 10th, 2012Whenever possible, I try to book a window seat on plane flights and look at clouds. If I remember to take my camera out of the carry-on bag, I like to shoot pictures of the pretty or interesting clouds and share them with other cloud afficianadoes.
Here’s a picture I took on a return flight from Colorado last week just as the sun was going down. When the tops of clouds form a fairly flat layer like this, it can indicate a demarcation in the atmosphere where conditions change from a turbulent air mass below the cloud tops where most of what we experience as weather oocurs to a more stable layer of the atmosphere. (The exception being really strong thunder-head clouds that punch through the others… when you see those anvil-shaped clouds from a plane, the pilot is usually trying to skirt around the often powerful storms below).
That transition point where clouds flatten out signifies the top of what’s technically known as the atmospheric boundary layer or planetary boundary layer. Generally about one or two kilometers thick, the boundary layer is affected by daytime heating and nighttime cooling, surface winds, fog and most clouds… in other words, weather.
Surprisingly the temperature above the boundary layer is generally warmer than the layer below. The way meteorologists traditionally measure the height of the boundary layer is by sending up weather balloons that continously measures temperature as they rise. When the temperature of air take a clear turn from gradual cooling towards warmth that signifies the top of the boundary layer. The National Weather Service for the Bay Area launches a weather balloon from the Oakland Airport twice a day to measure the height of the boundary layers and collect other atmospheric data for their forecasts.
As the Exploratorium prepares to move to the piers, we are making plans to install instruments and sensors that will monitor weather conditions, including an instrument to measure the height of the boundary layer without having to launch balloons (although we’d love to also launch weather balloons!). Called a radiometer, it detects the temperature inversion through microwave radiation measurments. It’s one of the instruments that will make up our “Wired Pier,” a set of sensors that will collect data about the Bay waters and atmosphere.









indicating to consumers that the fishery maintains a healthy population, doesn’t damage the environment, and is effectively managed. That appears to be the case for this Norwegian operation, which claims it only harvests 1% of the Antarctic krill population each year, but environmentalists are disgruntled with the Marine Stewardship Council in general for relying on consultants paid by the fisheries without taking into enough consideration the work of independent scientists and the growing realization that most of the world’s marine fisheries are not sustainable and indeed that most commercial stocks are on the 
That’s bad news for the tourists shivering in their shorts at Fishermans Wharf, but great news for a bicycle commuter like me who rides to the southeast end of the city to catch her train home. The 20 mph afternoon sea breeze that pushes me to my destination is a familiar weather pattern for most ocean communities, especially in summer. This pattern is caused when temperatures in the inland valleys warm up in the sun, causing air to rise and expand, creating a low-pressure region. Meanwhile, air over the cool ocean sinks and compresses, creating a relatively high-pressure region. Air flows from high to low pressure, creating what cyclists and tourists experience as wind. The greater the pressure difference, the stronger the wind.



