Computers, GPS, Doppler Radar, the Internet, and high-resolution satellites have sure changed the way we forecast the weather since the 1930s, but you might be surprised to know there's still one weather measurement that is decidedly low-tech -- a hydrogen balloon.
Yes, some 70 years later, we still rely on a simple weather balloon to get some important data. In fact, all those fancy expensive computer forecast models would be lost without them.
In the Northwest, weather balloons are launched twice a day at 4 a.m. PST and 4 p.m. PST from near Forks, WA, Spokane, Salem, Medford and Boise (which is on Mountain Time, so it's 5 a.m./p.m. MST for them.)
The balloons have a small weather instrument panel attached 6 feet below and rise at about a rate of about 1,000 feet a minute, according to noaa.gov. Here are some other interesting facts from their web site:
The sensors measure temperature, relative humidity and atmospheric pressure. (And wind speed and direction, but that's come around thanks to some newer technology -- GPS. By knowing the balloons location versus time, it can compute the wind speed and direction at a given altitude.)
The data is then sent every two seconds via small 1950s-era radio transmitter back to the ground, which uses a 1980s era IBM PC/XT processing computer. However, the weather measuring devices these days are quite high-tech, says Bill Blackmore with the National Weather Service.
More interesting tidbits from NOAA:
- The balloon's flight can last over two hours and it can rise to around 115,000 feet -- that's above 99 percent of the lower atmopshere. In fact, just before bursting (actually, it's more like they disintergrate), the balloons typically make it to where there is just a tiny fraction of atmospheric pressure left. (If you took a home barometer and stuck it up there... it would freeze. But if it still worked, it would read roughly 0.30" of mercury, whereas the average at sea level is 29.92".)
- Typical distance covered is around 180 miles, but it can go father if it gets caught in a jet stream. If so, it can reach speeds of 250 mph. Blackmore says there is one documented case where a balloon launched from Gaylord, Michigan (near the northern shore of the state) was found just outside of Pittsburgh -- a distance of about 400 miles.
- As the balloon rises, drops in atmospheric pressure cause the balloon to expand. It's about 6 feet wide at launch but can get a large as 20-25 feet across before it bursts. A small parachute slows the weather instruments' descent to the ground.
The National Weather Service releases about 75,000 balloons across the U.S. each year, of which only about 20 percent are ever found and returned. Which brings up an important point -- those weather instruments can be reused. So if you do find one, you can send it back to the NWS -- they'll cover the postage as long as it's found in the U.S. (Sorry Canada) -- and save them the cost of a new one. Instructions to do so are written on the instrument box if you should ever find one.
Blackmore says it costs roughly $150 to send up a balloon with new data recorders each time, but only about $50 to recycle the instruments if they are returned. So add that up over the year and it's a good cost savings.
(And let me know if you ever do find one and want to return it. It might make a good follow up blog entry.)
Of course, sometimes, the instruments get mistaken for something more sinister, like this case in South Carolina. The FBI has had to respond more than once to incidents of people finding the instrument box and think it was some sort of explosive device. But Blackmore says the devices are marked as harmless NOAA weather instruments and the agency is working to spread the word in the hopes that people will realize what they are before calling police. (Also, Blackmore says it turned out the instrument panel found in S.C. was not from a National Weather Service balloon, but one launched from another agency or university, possibly overseas.)
The balloons give important upper air data for computer forecasting models to use in getting a current picture of the atmosphere to base its mathematical formulas on future weather developments. They can also be used for more immediate information for severe or marine weather events, climate research, or even verifying satellite data, according to noaa.gov.
So, what does this stuff look like?
One of the more useful charts generated from a weather balloon is called a "Skew T" chart, which shows the temperature (right white vertical-ish line) and dew point (left white vertical-ish line).
But the chart is quite complex. If you're interested in learning to decode it, check out atmos.millersville.edu
In what might be a somewhat more easily decodable chart, here is that same data in table format.. You can see the pressure on the left in millbars, the height in meters that reading was taken, the temperature and dew point in Celsius (yes, everything's metric), the wind direction and speed (in knots).
Scroll all the way down and there is some other pertinent information, such as the current freezing level, although most of that data has to do with convection potential and gives good information for possibilities of strong thunderstorm development (which around here, is quite rare.)
Who would have thought all that can come from just one simple balloon?
(Read more about weather balloons at noaa.gov)