WFO Jackson does not have an upper air program

- - but like all NWS offices, the data collected from Upper Air stations is used extensively. Computer atmosphere models are designed around the upper air data gathered by the Upper Air stations across the country. The National Weather Service Upper-air Observations Program is managed by the Observing Systems Branch (OSB), which is part of NWS Headquarters located in Silver Spring, Maryland.  Upper-air Program staff oversee the operation of 92 Radiosonde stations in North America and the Pacific islands. It also supports the operation of 10 stations in the Caribbean.  Radiosondes provide upper-air data that are essential for weather forecasts and research. OSB staff are involved in the development and implementation of a new radiosonde ground tracking system that will replace the obsolete systems currently in use.


Early upper air observations began in 1898 and were obtained by using kites which carried an instrument package as high as the observer was able to fly his kite.
In WWII, with the use of rubber and radio transmission, balloons made possible much higher upper air observations.


For over 60 years, upper air observations have been made by the National Weather Service (NWS) with radiosondes. The radiosonde is a small, expendable instrument package that is suspended below a 6 foot wide balloon filled with hydrogen or helium.  As the radiosonde rises at about 1,000 feet per minute, sensors on the radiosonde measure pressure, temperature, and relative humidity. These sensors are linked to a battery powered, 300 milliwatt radio transmitter that sends the sensor measurements to a sensitive ground receiver by radio. By tracking the position of the radiosonde in flight, information on wind speed and direction aloft is also obtained.  Observations where winds aloft are also obtained are called "rawinsonde" observations.


Today's weather balloon is nearly identical to those used in WWII. The instrument package has changed, becoming much smaller, but still operating by sending the data back to the operator via a radio signal. The NWS is in the process of "modernizing" the upper-air program with new tracking systems. The balloon however, will remain much the same.


The radiosonde flight can last in excess of two hours, and during this time the radiosonde can ascend to over 35 km (about 115,000 feet) and drift more than 200 km (about 125 miles) from the release point. During the flight, the radiosonde is exposed to temperatures as cold as -90C (-130F) and an air pressure only few thousandths of what is found on the Earth's surface. When the balloon has expanded beyond its elastic limit and bursts (about 20 feet in diameter), a small parachute slows the descent of the radiosonde, minimizing the danger to lives and property.

Only about 20 percent of the approximately 75,000 radiosondes released by the NWS each year are found and returned to the NWS for reconditioning. These rebuilt radiosondes are used again, saving the NWS the cost of a new instrument. If you find a radiosonde, follow the mailing instructions printed on the side of the instrument.

Worldwide, there are nearly 900 upper-air observation stations.  Most are located in the Northern Hemisphere and all observations are usually taken at the same time each day (00:00 and/or 12:00 UTC), 365 days a year. (UTC stands for Universal Time Coordinated - meaning that everyone on earth can operate on the same time. UTC used to be called Greenwich Mean Time, or GMT, and is 5 hours ahead of Eastern Standard Time). Observations are made by the NWS at 92 stations - 69 in the conterminous United States, 13 in Alaska, 9 in the Pacific, and 1 in Puerto Rico. NWS supports the operation of 10 other stations in the Caribbean.  Through international agreements data are exchanged between countries and the data is encoded following the same format. Collecting the data at virtually the same time around the globe gives the meteorologist a "photographic" picture of the atmosphere. An interesting note, the collection and processing of weather data is the only successful world-wide venture.


For additional nformation:


NWS Jackson Home Page

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