Artist’s impression of Metop-A in orbit.

Metop-B is the second of three identical Metop satellites which, together with dedicated ground infrastructure, form the EUMETSAT Polar System (EPS). Each of the three satellites has a nominal lifetime of five years, with a 6 month overlap, and their purpose is to provide continuous, long-term data sets for use in operational meteorology, and climate and environmental monitoring.

When Metop-B is launched later this year, it will join its predecessor Metop-A – launched in 2006 - in a “mid morning” polar orbit, 850 km above the Earth. Both satellites will be operated simultaneously by EUMETSAT, until the end of Metop-A’s lifetime.

The third of the series, Metop-C, is planned for launch in 2017, at the end of the nominal lifetime of Metop-B.

Following on from Metop-A

Alain Ratier, Director-General of EUMETSAT, said, “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.

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.”

The Metop 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). 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 mission’s duration. The US NOAA and the French Space Agency are also partners, providing some of the key instruments of the Metop payload.

Metop Instruments

Each satellite carries eight instruments capable of taking measurements of the atmosphere, including temperature and humidity profiles, cloud properties, greenhouse and trace gases such as ozone, methane and carbon monoxide, and even sulphur dioxide emitted from volcanoes. These instruments also observe the ocean and continental surfaces, providing measurements of wind at the ocean surface, ice, snow and soil moisture.

Florence Rabier, Deputy-Head of the Numerical Weather Prediction group (GMAP) of the CNRM-GAME (a joint research unit of Météo-France and CNRS) said, " 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.”

The vital role of Metop-A data in weather forecasting is best illustrated by a recent UK 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%.

When this analysis was focused on the contribution of data from individual satellites to NWP models, Metop-A’s contribution is nearly 40%. 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.

Figure 1 shows the contribution of Metop data (24%) - relative to other data sources - to NWP forecasts which are the basis of weather forecasts. Figure 2 shows the contribution of individual satellites to NWP forecasts (source: UK Met Office)

Metop instruments - IASI

One of the key instruments onboard the Metop satellites is the Infrared Atmospheric Sounding Interferometer (IASI). 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. 

Dieter Klaes, EUMETSAT EPS Programme Scientist said, “With IASI, forecast centres like ECMWF – European Centre for Medium Range Weather Forecasts- have gained about half to one day in forecast reliability compared to 15 years ago. IASI has also made a huge difference to our understanding of atmospheric chemistry, and what is particularly exciting is that that the instrument has much more capability than was originally foreseen.”

IASI has enabled scientists to be able 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, can also be mapped, allowing the identification of new sources.

Florence Rabier added; “The IASI instrument is highly innovative and is already one of the most informative among the remote sensing instruments of operational and research platforms.”
 
For climate monitoring, IASI is playing a key role by collecting data on a host of climate variables which include: temperature and water vapour, 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 have also 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.  

Detection of volcanic ash from the Grímsvötn volcano by IASI. Source: Belgian Institute for Space Aeronomy

ATOVS

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. ATOVS instruments provide temperature and water vapour data at different heights in the atmosphere – even in cloudy conditions – and this data plays 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 AMSU-A instrument measures radiances from the Earth’s surface and/or atmosphere in 15 microwave channels to derive atmospheric temperature profiles from the surface to an altitude of around 45 km

GOME-2

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 has also 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.

Observations of Ozone and Nitrogen Dioxide in the atmosphere, from GOME-2

GRAS

An atmospheric temperature profile (0-50km) obtained from the GRAS instrument (Kelvin). Source: GRAS SAF

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. The instrument is basically self-calibrating, which is of great value for tracking long-term climate change signals.

ASCAT: a look at the Ocean and land surfaces

Monitoring near surface wind speed and direction over the global oceans is the role of the Advanced SCATterometer (ASCAT) which is a radar instrument providing crucial data to follow the development of storms and hurricanes/typhoons/cyclones. But this is just one example of its many uses: it is also used to monitor sea ice (concentration, coverage, type ) and its ability to monitor soil moisture has opened up a multitude of uses, including input to NWP models. ASCAT is a derivative from the multipurpose Active Microwave Instrument (AMI-Scat) scatterometers first flown on ESA’s ERS-1 and ERS-2 satellites.

Left – ASCAT wind product showing Tropical Cyclone Phet over the Indian Ocean, close to Oman (source: KNMI). Right - ASCAT soil moisture (12.5 km resolution) provides an estimate of water saturation of the 5 cm topsoil layer, in relative units between 0 (red) and 100% (dark blue)

AVHRR: a multipurpose imager

The Advanced Very High Resolution Radiometer (AVHRR/3) is another heritage instrument provided by NOAA (first carried on NOAA-7 in 1981 - an earlier version of AVHRR) that provides visible/infrared monitoring of cloud cover, sea surface temperature, ice, snow and vegetation and land cover, and it is also being used to monitor winds in the polar regions.

Images captured by the AVHRR: left – Tropical Storm Katia 31 August 2011; right - The ash cloud from the Grimsvötn volcano on 23 May 2011

Metop-B – part of the Initial Joint Polar System

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 USA. This is cooperation between EUMETSAT and the US National Oceanic and Atmospheric Administration (NOAA), where Metop satellites from Europe, and NOAA satellites from USA, fly in complementary polar orbits, designed to ensure global data coverage, and instruments are exchanged between partners.

Alain Ratier said, “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.”

EPS-SG – beyond 2020

The series of consecutive Metop satellites are intended to operate until 2020. They will then be succeeded by the next generation system of European polar-orbiting satellites: EUMETSAT Polar System – Second Generation (EPS-SG).

Alain Ratier said’ “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. Our objective, with ESA, is to secure the availability of the first satellite of the EPS-SG programme by the end of 2020.”

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