For weather forecasts and study of climate, the meteorological department must undertake the study of the upper atmosphere, which is the primary determinant of the weather of an area, through chemical or temperature changes that take place here. The atmosphere is 100 to 125 kilometers thick. It is composed of different layers. The one important for the study of weather is the lowest layer called the troposphere, which is the part that begins from the surface of the earth and extends up to 10 km above it.
It is important to know the natural conditions in the higher atmosphere, in addition to that near the ground level, to make a weather forecast. This is done by sending balloons carrying radiosonde, i.e. meteorological data recording instruments and a radio transmitter, to high altitudes. A folded parachute with a container of the radiosonde is tied to helium or hydrogen-filled balloon. Meteorological instruments record the data, such as atmospheric pressure, wind speed, wind direction, temperature, relative humidity, etc. And then, transmit it to the meteorological observatories by radio transmitter.
Nearly 650 meteorological observatories, all over the world, send radiosonde balloons twice a day precisely at 00:00 hours. As the forces responsible for ‘concocting’ weather (humidity, wind temperature, atmospheric pressure, etc.) are fluctuating, unless all the countries ascertain atmospheric data at the same time, it is not possible to construct the overall picture for forecasting weather on a national or international scale.
Weather radars are an important source of obtaining information from the atmosphere about weather conditions. The radars are placed atop the meteorological stations. They send radio waves into the atmosphere, which are reflected from particles in the atmosphere and the specialists can assess the number and density of clouds, their velocity, and direction of movement, hence predicting whether or not there will be precipitation.
Weather forecast departments also use dual-polarization radars. They can send out radiation both vertically and horizontally and are better able to predict the cloud cover, the density of water vapors, and the predictability of precipitation and other weather events.
For monitoring remote weather conditions high up in the atmosphere, satellites are used. The satellites are launched to circulate in the atmosphere. They collect weather information by using visible light and infrared part of the electromagnetic spectrum.
Visible light is used to assess the cloud cover and density of particles in the atmosphere. At the same time, the infrared waves send back data about the number of water vapors, and the thermal changes in the atmosphere, which further provides a lot of information on the weather. The infrared imagery can predict such things as cyclones, eddies, and vortices, which may be very valuable for the fishermen and shipping industry.
Knowing weather forecast may be important for a small localized area, for the prediction of a strong wind, precipitation, etc., or a large-scale global prediction may be required about pressure changes, which may give rise to a cyclone or strong winds that might be moving in one particular direction. This is possible by studying chemical and physical changes in the atmosphere. Whether global or local, weather prediction requires a concerted effort by meteorologists from around the world.
Modern-day weather forecasting uses computer software that has numerical weather prediction, which became a reality only in the 20th century. It requires advanced computer software. However, traditional methods are still being used to study the higher atmosphere for making weather forecasts.