In order to map the atmosphere we need measurements at many points along the surface and at different heights in the atmosphere. The remainder of this session will focus on where we take our measurements and the technology we use to get them.
The Surface and Aloft
Most of the data collected for forecasting, with the exception of special research studies, is collected by the National Weather Service (NWS). The NWS has ground stations established all over the country to monitor surface conditions as well as obtain data regularly from the atmosphere aloft. In addition to the NWS ground stations, the NWS works in cooperation with airports, businesses, farmers, schools, and other agencies to obtain surface data in order to construct detailed atmospheric surface maps.
While it is simple enough to obtain data from the surface, it is a bit more difficult to get readings from high up in the atmosphere. So how on earth, so to speak, do we get way up there to take those measurements? Well, one of the more obvious choices might be an airplane. Planes, however, are actually too limited in the heights they can fly. Commercial planes fly at heights of around 30,000 feet, or 6 miles. We need readings as high up as 19-20 miles at regular intervals. The answer is weather balloons. Attached to these weather balloons are radiosondes which are mini electronic weather stations that take measurements and transmit the data back to receivers on the ground.
The National Weather Service in the U. S., in conjunction with other similar agencies across the globe, releases weather balloons twice a day at weather stations all over the world. The balloons are released at 000 hours and 1200 hours UTC. UTC is a universal time reference where 0000 and 1200 represent noon and midnight (respectively) on the prime meridian or zero degrees longitude. All over the earth, twice a day, literally thousands of balloons are simultaneously released in an effort to collect weather data.
Each radiosonde that is released contains an electronic thermometer to measure the temperature, an aneroid barometer for pressure, and a hygrometer to determine the amount of moisture (dew point temperature) in the air. Every few seconds the radiosonde takes a measurement and transmits the data back to earth. Tracking equipment on the ground can determine the radiosonde's position so that wind speeds and directions can be determined as well as the height of the balloon for each measurement taken. A computer takes this data and constructs a profile of the atmosphere for each location at which a balloon is released. These profiles are graphically reproduced on a number of different charts and diagrams that can provide forecasters and air quality professionals quick and valuable references for determining atmospheric conditions all over the world. But even more impressive, this data is used in computers to actually model the atmosphere. Computer software performs the tedious task of computing the many advanced parameters required to simulate and model the atmosphere for weather forecasting and air pollutant transport, dispersion, deposition, and concentration estimates.
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