Europe’s Metop Satellites: Monitoring the Weather and Climate from Space
Europe’s next weather satellite, Metop-B, is scheduled to launch on May 23 from the Baikonur Cosmodrome, in Kazakhstan, and join its predecessor, Metop-A, in polar orbit, 817 kilometers above Earth.
Metop-B is the second of three identical Metop satellites, which, together with dedicated ground infrastructure, form the EUMETSAT Polar System (EPS). The purpose of the Metop satellites is to provide continuous, long-term data sets for operational meteorology, climate and environmental monitoring until 2020.
“The first of the Metop series, Metop-A, has already exceeded all our expectations, and the data its instruments provide have made a major contribution to improving Numerical Weather Prediction (NWP) models, the basis for today’s weather forecasts,” said Alain Ratier, Director-General of EUMETSAT. “By helping to improve the weather forecasts and severe weather warnings delivered by the national weather services across Europe, Metop-A helps save lives and limit damage to property. It also delivers high benefits for transport, agriculture, energy, tourism, climate policy and environmental protection.”
Each Metop satellite has a nominal lifetime of five years, with a six-month overlap. Metop-A has been in orbit since its launch in 2006. When Metop-B launches in 2012, both satellites will be operated simultaneously by EUMETSAT, until the end of Metop-A’s lifetime. The last of the series, Metop-C, is expected to launch in 2017, at the end of the nominal lifetime of Metop-B.
The satellites are built in Europe by a consortium led by EADS Astrium, within the framework of a successful partnership between EUMETSAT and the European Space Agency (ESA). The ESA is responsible for the development of the space segment, while EUMETSAT is responsible for the development of the overall system, the ground segment and operating the satellites over the duration of the mission. The U.S. National Oceanic and Atmospheric Administration (NOAA) and the French Space Agency also are partners, providing some of the key instruments of the Metop payload.
Each Metop satellite carries eight instruments for taking measurements of the atmosphere, including temperature and humidity profiles, cloud properties, and greenhouse and trace gases such as ozone, methane, carbon monoxide, and volcano-emitted sulphur dioxide. These instruments also observe the ocean and continental surfaces, providing measurements of wind at the ocean surface, ice, snow and soil moisture.
“It is very impressive how Metop-A observations are now used by meteorologists, atmospheric scientists and climatologists in Europe, and all over the world. The various instruments on board the satellite provide a wealth of invaluable data,” said Florence Rabier, deputy-head of the Numerical Weather Prediction Group (GMAP) of the CNRM-GAME, a joint research unit of Météo-France and CNRS.
The vital role of Metop-A data in weather forecasting is best illustrated by a recent U.K. Met Office estimate of the impact of various data sources, in situ, airborne and space-based, on NWP models, in which Metop-A accounts for the highest level of contribution at over 24 percent.
When this analysis was focused on the contribution of data from individual satellites to NWP models, Metop-A’s contribution is nearly 40 percent. This is more than double the contribution of other individual weather satellites, and highlights the importance of investment in new, more technologically advanced satellites such as Metop, and NASA’s recently launched SUOMI NPP.
Metop instruments – IASI
One of the key instruments aboard the Metop satellite is the Infrared Atmospheric Sounding Interferometer (IASI). The IASI measures infrared energy emitted by the Earth-atmosphere system in thousands of spectral channels. Vertical profiles of atmospheric temperature and moisture of unprecedented accuracy can then be extracted from this wealth of information, along with the concentration of some greenhouse and trace gases.
“With IASI, forecast centers like ECMWF – European Centre for Medium Range Weather Forecasts – have gained about half to one day in forecast reliability compared to 15 years ago,” said Dieter Klaes, EUMETSAT EPS Programme Scientist. “IASI has also made a huge difference to our understanding of atmospheric chemistry, and what is particularly exciting is that the instrument has much more capability than was originally foreseen.”
IASI has enabled scientists to produce global distribution maps of gases such as ozone and carbon monoxide in near-real time, while short-lived chemicals in the atmosphere, such as ammonia or methanol, also can be mapped, allowing the identification of new sources.
“The IASI instrument is highly innovative and is already one of the most informative among the remote sensing instruments of operational and research platforms,” said Rabier of the Numerical Weather Prediction Group.
For climate monitoring, IASI is playing a key role by collecting data on a host of climate variables including temperature and water vapor, and greenhouse and trace gases such as carbon monoxide (CO), methane (CH4), ozone (O3), nitrous oxide (N2O) and even carbon dioxide (CO2) in certain conditions.
IASI data also have been used to successfully track the location and chemistry of gaseous plumes and particles resulting from volcanic eruptions and fires, providing valuable data for aircraft safety and air quality monitoring. As examples, IASI data were used to follow ash and sulphur dioxide (SO2) emitted from the Eyjafjallajökull and Grímsvötn volcanic eruptions and to monitor the depth of the carbon monoxide plume over Moscow arising from Russian wildfires in 2010.
The ATOVS (Advanced TIROS Operational Sounder) is an heritage instrument package delivered by NOAA, which includes the Advanced Microwave Sounding Unit-A (AMSU-A), Microwave Humidity Sounder (MHS) and High Resolution Infrared Radiation Sounder (HIRS/4) sounding instruments. The ATOVS instruments provide temperature and water vapor data at different heights in the atmosphere – even in cloudy conditions – and this data play a key role in weather forecasting, including input to NWP. As the ATOVS instruments were flown on NOAA satellites, they provide data continuity, which helps to build up time series of data for climate monitoring.
The GOME-2 is a spectrometer that provides the capability to monitor atmospheric ozone (O3), nitrogen dioxide (NO2), sulphur dioxide (SO2), and other trace gases, in near real-time. It is an important instrument to continue ongoing monitoring of the Antarctic ozone hole and an important source of atmospheric quality information. Because of its ability to monitor SO2, GOME-2 also has played an important role in monitoring recent volcanic eruptions and, in full synergy with IASI, it is now a component of volcanic activity and air quality warning systems such as TEMIS.
The GOME-2 instrument is an enhanced successor to the original GOME, which was first flown by ESA on ERS-2 in 1995, and so it is extending a growing time-series of global atmospheric ozone and other trace gas measurements.
The GRAS instrument (Global Navigation Satellite System Receiver for Atmospheric Sounding) uses signals from the Global Positioning System and provides information on vertical profiles of temperature and humidity, which are used in Numerical Weather Prediction (NWP) models and for climate monitoring. As GRAS is basically self-calibrating, it is extremely valuable for tracking long-term climate change signals.
Monitoring near-surface wind speed and direction over the global oceans is the role of the Advanced Scatterometer (ASCAT), a radar instrument providing crucial data to follow the development of storms and hurricanes, typhoons and cyclones. Still, this is just one example of its many uses, as it is also used to monitor sea ice concentration, coverage and type, and its ability to monitor soil moisture has opened up a multitude of uses, including input to NWP models.
The Advanced Very High Resolution Radiometer (AVHRR/3) is another heritage instrument provided by NOAA, first carried on NOAA-7 in 1981, that provides visible infrared monitoring of cloud cover, sea surface temperature, ice, snow and vegetation and land cover, and is also being used to monitor winds in the polar regions.
After its launch in 2012, Metop-B will be the second European contribution to the Initial Joint Polar System (IJPS) shared by Europe and the United States.
This is cooperation between EUMETSAT and NOAA, where Metop satellites from Europe, and NOAA satellites from the U.S., fly in complementary polar orbits, designed to ensure global data coverage, and instruments are exchanged between partners.
“The benefits of Metop for users in terms of improved weather forecasting, flood and storm warnings are high and these benefits are amplified by our collaboration with NOAA,” said Ratier.
The series of consecutive Metop satellites are intended to operate until 2020, when they will be succeeded by the next generation system of European polar-orbiting satellites: EUMETSAT Polar System – Second Generation (EPS-SG).
“It is absolutely vital that we continue to collect and improve satellite observations from the polar orbit beyond 2020, to further improve forecasts and thus increase benefits to society,” said Ratier. “Our objective, with ESA, is to secure the availability of the first satellite of the EPS-SG programme by the end of 2020.”
Neil Fletcher is communications manager for EUMETSAT in Darmstadt, Germany. With a background in marine science and Earth observation, Neil has been working as a science communicator for the last 10 years.