During the last decade, it became clear that the chemical composition of the atmosphere changed globally. Moreover, human activities are partly responsible for this evolution. This is why experiments conducted on the Space Pole are integrated in international programs like the one called Global Change. For a better understanding of the phenomena, which influence the Earth’s atmosphere and climate, the programs study atmospheric mechanisms on a global scale.

With this goal, the experimental programs at the Belgian Institute for Space Aeronomy use a broad variety of means: observations and measurements are carried out from Earth observatories, stratospheric balloons, rocket probes on board of spacecrafts like space shuttles and satellites. More and more, space research depends on measurements in the laboratory. Furthermore, theoretical research is important because the theoretical modelling is necessary for the interpretation of experimental data. These models map the past, the present and the future atmospheric conditions.

The atmospheric environment studies imply measures on particles coming from various sources such urban pollution and volcanic plumes to the atmosphere as a whole. The observations have to be spread over a longer period. This permits the distinction between long term tendencies and natural changes that are related to seasonal or other cyclic phenomena like the activity of the Sun.

The combination of different kinds of techniques and measuring platforms (ground stations, airplane, balloon, rocket, spacecraft, satellite) permits to obtain good results. The experiments on the ground (picture 1) or carried out in a balloon or in an airplane are preferable because of their accuracy in the studies of physical chemical processes. The satellite instruments (video 1), make it possible to extrapolate these studies to a worldwide scale. They provide constant world cartography of the most important atmospheric elements and parameters. To obtain a total vision, scientists integrate the different processes into mathematical computer models of the atmosphere.

Concerning meteorological forecast (picture 2), it is essential to precisely visualize the present state of the weather. That implies the construction of a graphic model on a broad scale, from the surface and upward.
To build such a graphic model, the Royal Meteorological Institute, through a network of observation stations, collect parameters like atmospheric pressure, air temperature, direction and intensity of the wind, cloudiness, atmospheric humidity and the amount of rainfall, every three hours. These observations are carried out all over the world at the same time in a standardized way.

In addition to the observations at the surface, other observations on the level of the atmosphere must be carried out to elaborate a 3D meteorology graphical model. On different places in the world aerological probes are carried out. In Belgium, the RMI performs this kind of (picture 3) modelling four times per day. A balloon filled with hydrogen and transporting a radio probe, will gather weather data up to thirty kilometers. The measurements are then sent back to a receiving station located at Ukkel.

Besides the classical observations, as described above, satellite observations try to fill the shortages since the sixties. Meteorological satellites in an orbit around the Earth deliver on regular points in time images of parts of the atmosphere. Thanks to these, we can see the cloud animations, during the weather reports on television. Moreover, the original images coming from the satellite have an enormous scientific value.

Radar images have gained of importance in the last decade. These images make it possible to follow the displacement of rainfall in almost real time. By a system called SAFIR, the Royal Meteorological Institute can follow the evolution of storms by recording the discharges of thunders, and then emit warnings useful for the population.

Because of enormous progress in the space research, we are now able to study every part of the radiations balance on an international scale. Certain instruments, like the radiometers, developed in Ukkel, become an international reference. The obtained data are interesting for the whole scientific community interested in the changes of the climatologic balance.

Following and understanding the water cycle to contribute to a durable development and respect for indispensable resources is a task that passions certain scientists.
Measuring the amount of rainfall (picture 4) is less simple than one would think. For a correct evaluation of what a hydrologic basin receives, one has to choose measuring instruments in function of the type of rain (rain showers, frontal rain…).
The measurements of water vapor is an important parameter, by either direct measurement, or indirect starting from different parameters. The development of new means on board of satellites (video 2) or on the ground therefore demands hydrologists, specialized in the atmospheric part of the water cycle, bending over new challenges.