Every day around 4 a.m., the 30th Weather Squadron from Vandenberg Air Force Base in northern Santa Barbara County launches a weather balloon with a tiny transmitter called a radiosonde attached. As the weather balloon climbs through the atmosphere, its transmitter broadcasts back to the receiving station readings on temperature, dew point temperature, pressure and GPS coordinates for the winds.
On a clear day last week, three U.S. Air Force meteorologists from VAFB and I launched a weather balloon from Branch Elementary School in Arroyo Grande to demonstrate the differences between surface winds and upper-level winds.
Pacific Gas and Electric Co. provided the weather balloon and Airgas of San Luis Obispo delivered the helium gas in a steel cylinder to fill it. Before the balloon was released, we showed the students the mid- and upper-level charts and a vertical graph of the atmosphere, called a Skew T chart, from that day’s weather balloon launch from the base.
It showed the air and dew point temperatures but more importantly for the demonstration was the wind direction and speed at different altitudes in the atmosphere. This data is also referred to as “soundings.” Aircraft that fly into hurricanes, such as the NOAA P-3 Orion and the U.S. Air Force C-130 Hercules, deploy dropsondes, which send a detailed look at the structure of the atmosphere below as it falls towards the sea.
Before the balloon was released, the students checked their school’s weather station (Davis Instruments Vantage Pro 2), which measures minute by minute temperatures, rainfall, wind speed and direction, humidity, barometric pressure and even peak solar radiation. This station was skillfully installed by Branch Elementary School’s maintenance department and Chris Arndt of www.sloweather.com a few years ago.
The students estimated which direction the balloon would travel at the Earth’s surface and as it ascended into the sky. Sure enough, the southwesterly winds at the surface carried the balloon toward the northeast. However, as it reached between 10,000 and 15,000 feet, it flew into 50 mph northeasterly winds, and it was carried back over the campus. As it traveled southwestward and to continue to rise, it disappeared into the sky.
This experiment showed the students the differences that can occur between the surface and upper-level winds.
“The school already had a weather station that allowed students to learn the science behind weather and forecasting in a very hands-on way. This week they took the learning to new heights with the weather balloon.” Principal Hillery Dixon said.
There are two main types of balloons — mylar and latex —that are in use today. Mylar balloons are made with mylar nylon, a material not classified as biodegradable. They often are coated with a metallic finish that conducts electricity. On the other hand, latex weather balloons are elastic and are composed of natural rubber that is biodegradable. These balloons are about 4 feet in diameter at sea level and expand in diameter as they rise.
By the time they reach about 100,000 feet, they expand to about 40 feet in diameter due to decreasing air pressure. Air temperatures at this altitude can drop to 50 degrees below zero or lower and freeze the latex. At this high altitude, a frozen balloon undergoes “brittle fracturing” and ruptures into small shreds of rubber that fall to earth and quickly decompose.
When mylar balloons climb between 3,000 and 7,000 feet, they either explode or lose their “lift” and can fall into the ocean. Unfortunately, oceanic creatures, such as sea turtles, can mistake these balloons for food. When eaten, they clog their intestinal tracts, causing them to starve. Not only do these metallic balloons litter pristine wilderness areas, but they also are a major cause of power outages.
PG&E reminds customers to follow these safety tips for metallic balloons:
• “Look Up and Live!” Use caution and avoid celebrating with metallic balloons near overhead electric lines.
• Make sure helium-filled metallic balloons are securely tied to a weight heavy enough to prevent them from floating away. Never remove the weight.
• When possible, keep metallic balloons indoors. Never permit metallic balloons to be released outside.
• Do not bundle metallic balloons together.
• Never attempt to retrieve any type of balloon, kite or toy that becomes caught in a power line. Leave it alone and immediately call PG&E at 800-743-5000 to report the problem.
• Never go near a power line that has fallen to the ground or is dangling in the air. Always assume downed electric lines are energized and extremely dangerous. Immediately call 911 to alert the police and fire departments.