By Tiffany Stecker
The European Space Agency (ESA) has launched the first-ever satellite to gauge soil moisture and ocean salinity, with the mission of collecting crucial data on atmospheric and terrestrial water to provide more accurate weather forecasting.
The Soil Moisture and Ocean Salinity (SMOS) satellite was launched in early November from northern Russia. It is the second of six satellites the ESA have launched in their Earth Explorer Mission, which aims to track changes in the earth’s resources more efficiently.
The launch of the SMOS is a timely one. The mission began just days after torrential floods fell upon Scotland and Wales. Floods, as well as droughts, are two phenomena scientists hope to understand better from the data. Soil moisture can give an insight as to whether water runs off soil or absorbs into it.
“This touches on two very important aspects of the water cycle,” said Mark Drinkwater, head of the Mission Science Division of the ESA. “We have very little knowledge today on how water exchanges with the atmosphere.”
The satellite measures radioactivity in microwaves called L Band, waves approximately 20 cm long. It is the first L Band radiometre in space.
Using these waves, the satellite will measure moisture levels in the upper layer of soil, ocean salinity and evaporation rates. It is designed to track miniscule changes in moisture and salt concentration and consequently, how storms develop and how soils react to excessive amounts of water.
According to Drinkwater, SMOS can detect levels of moisture equivalent to a teaspoonful of water in a handful of soil. The satellite will be able to measure dampening and drying cycles of the soil in response to rainfall events every three days.
“It gives a global view on the distribution of soil moisture,” said Yann Kerr, lead investigator with the Center for Spatial Studies of the Biosphere. “There is no measurement of soil moisture in [current] weather forecast models.”
A major indicator of flood magnitude is not necessarily the amount of rainfall, said Kerr, but the ability for soil to absorb it.
“You can have dry soil with heavy rain, and there won’t be flooding,” he said, “Or you can have drenched soil and little rain and there is a flood.”
For example, floods in France earlier this year were linked to waterlogged soils, rather than heavy rain.
The satellite must undergo a six-month commissioning phase before it can engage in a longer program. It is guaranteed for three years, with a life expectancy of five, said Kerr.
SMOS will also measure water salinity, which indicates ocean current movement and can estimate how and at what rate climate will change. The satellite can measure salinity with an accuracy of 0.01 to 0.02 per cent, and has the sensitivity to detect a “small pinch of salt in a litre of water,” said Drinkwater. The team will accumulate global ocean data over longer intervals than soil moisture, in order to map changes throughout the year, and examine how patterns of surface salinity vary seasonally.
The European Centre for Medium-Range Weather Forecasts will be one of the primary users of this data. The centre predicts weather patterns across Europe and expects forecasts to become more accurate with the help of SMOS.
“What is important for us is the construction of a model between atmospheric variables and surface values of soil temperature,” said Patricia de Rosnay, a scientist at the centre.
Yet de Rosnay is aware that it is early days for SMOS, and the level of importance and reliability of the soil humidity and salinity data is yet to be known.
“We will wait and see how much it improves the forecast. The Earth Explorer mission is a new concept, and it is the first time we have soil moisture information,” she said. “In 2010, we will see how useful it is.”
The next satellite in the Earth Explorer series will be Cryosat, which will measure changes in ice formations.