Climate Sense

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EUMETSAT has already made good progress in a programme

for the third generation of operational geostationary satellites.

The unique nature of geostationary measurements and their high

temporal frequency provide the capability to observe sub-synop-

tic atmospheric and surface events – particularly precipitating

cloud systems – and to characterize the diurnal cycles of the

atmospheric-surface system. Characterization of the annual,

as well as diurnal cycles, is crucial for an understanding of the

physical processes determining the status of the climate system

and its potential changes.

Since the launch of Metop-A in October 2006, EUMETSAT

has been operating a polar orbiting satellite system, called the

EUMETSAT Polar System (EPS), with a long-term operational

and global perspective. Through its innovative payload, the

Metop satellite can provide information on a large number of

key climate variables over at least 14 years of operational service

on a global scale.

The hyper spectral Infrared Atmospheric Sounding

Interferometer (IASI) allows the retrieval of temperature and

moisture profiles with high accuracy (1 Kelvin, 15

per cent, respectively) over one-kilometre layers. IASI

also allows the observation of trace gases relevant

to the greenhouse effect and for atmospheric chem-

istry. The Global Ozone Monitoring Experiment-2

(GOME-2) continues to measure ozone profiles and

related trace gases with high accuracy. The Global

Navigation Satellite System Radio-occultation

Atmospheric Sounder (GRAS) also provides informa-

tion on temperature and humidity profiles, with the

advantage that no adaption of calibration between

subsequent satellites is required for the creation of

long-term data sets. The observations are absolute,

based on time. From the other instruments on Metop

– the Advanced Very High Resolution Radiometer

(AVHRR), Advanced TIROS Operational Vertical

Sounder (ATOVS) and Advanced Scatterometer

(ASCAT) – long-term climate records can be derived,

especially with regard to AVHRR and ATOVS, which

Images of the Ocean Surface Topography Mission/Jason 2 satellite (left) and the Metop-A, which was launched in October 2006

Image: EUMETSAT