Earthcare satellite to probe the impact of clouds on climate


A rocket carrying a sophisticated European-Japanese satellite has blasted off on a mission to measure how clouds affect the climate.

The Earthcare orbiter, a collaboration between the European Space Agency (ESA) and Japan's JAXA space agency, launched from Vandenberg air base in California on Tuesday.

Weighing 2.3 tonnes, the satellite was sent up from on a SpaceX rocket. It will orbit nearly 400 kilometers above Earth for three years.

ESA, which is leading the mission, has described it as the organisation's most complex Earth observation venture to date. 

"Tonight's launch is a reminder that space is not only about exploring distant galaxies and planets. It is about understanding our beautiful but fragile Earth," ESA director Josef Aschbacher said in a video.

Parasol or blanket?

Clouds – from cumulus and cirrus to cumulonimbus – are a varied and complicated phenomenon.

Low-level cumulus clouds are known to cool the planet, while the cirrus clouds higher up act as a blanket.

The white and bright cumulus clouds, which are made out of water droplets, sit low and work like a parasol, reflecting the Sun's radiation back into space and cooling the atmosphere.

But cirrus clouds, made of ice crystals, allow solar radiation to pass through, heating up the planet.

Their composition depends on where they are located in the troposphere, Earth's lowest layer of atmosphere.

"They are one of the main contributors to how the climate changes – and one of the least understood," Dominique Gillieron, head of ESA's Earth observation projects department, told AFP.

The troposphere starts at around eight kilometers above the polar regions, but near the equator it begins at around 18 kilometers up.

This means that clouds affect the climate differently depending on their altitude and latitude.

Probing the atmosphere

Earthcare will become the first satellite to measure both the vertical and horizontal distribution of clouds, said Simonetta Cheli, head of the ESA's Earth observation programs.

Two of the satellite's instruments will flash light at the clouds to probe their depths.

One of them, involving light detection and ranging, or LIDAR, will use a laser pulse to measure both clouds and aerosols, which are tiny particles such as dust, pollen or human-emitted pollutants like smoke or ash.

Aerosols are the precursors to clouds, Gillieron explained.

The satellite's radar will pierce through the clouds to measure how much water they contain, and track cloud speed. Other instruments will measure shape and temperature.

The data will form the first complete picture of clouds from the perspective of a satellite, and help update climate models that estimate how quickly the planet will warm.

The mission aims to find out whether the current effect of the clouds, which is cooling, will become stronger or weaker.

This trend has become more difficult to predict as global warming has changed the distribution of clouds.

(with AFP)