One of major challenges facing Earth's science in the next decade and
beyondis the development of an accurate long term observational data set
to study global change. To accomplish this, a wide range of observations
will be required to provide both new measurements, not previously
achievable and measurements with a greater degreee of accuracy and
resolution than the ones which are presently and currently available.
Among the parameters that are currently retrieved from satellite
vertical sounding observations, temperature and moisture profiles are
the most important for the description of the thermodynamic state of the
medium. Other parameters, like those describing the cloud fields, the
surface state or the conditions close to the surface are also key
parameters for meteorology and climatology. A new generation of high
spectral atmospheric sounders in the infrared has recently been designed
to provide both new and more accurate data about the atmosphere, land
and oceans for application to climate studies. Among the important
observations that these instruments should contribute to the climate
data set are day and night global measurements of: atmospheric
temperature profiles; relative humidity profiles; cloud field
parameters; total ozone burden of the atmosphere; distribution of minor
atmospehric gases (methane, carbonmonoxide and nitrous oxide).