You experience weather at the Earth's surface, but there is weather high in the atmosphere, too. Have you ever taken a ride in a hot-air balloon or climbed a high mountain? You would know that the air temperature usually decreases with altitude. The basic reason has to do with where the atmosphere receives its heat and where it loses its heat. The Earth's surface is heated by the sun at some times and places. It loses heat to outer space at other times and places. On balance, however, the Earth's surface gains more heat than it loses. The atmosphere near the ground is then heated by the ground. High up in the atmosphere, however, the air loses more heat to space than it absorbs from sunlight. Air pressure decreases with increasing altitude.
Many kinds of devices have been invented for measuring things like temperature, pressure, and humidity in the upper atmosphere. These devices, called sondes, are packages of several instruments. Balloons are used to carry them up through the atmosphere. As they rise, they send back measurements by radio. Eventually the balloon pops, and the instruments crash back to Earth. Their fall is not dangerous to humans, because the instruments are very small and light.