The Finnish Meteorological Institute has developed a new, globally unique method for estimating surface albedo in the Arctic sea area solely on the basis of microwave data. Its advantage over conventional optical methods is that neither clouds nor darkness interfere with measurements.
Photo: Antti Samuli
The Finnish Meteorological Institute has developed a unique method for estimating surface albedo in the Arctic sea area. The method helps determine the amounts of solar radiation reflected from the Arctic sea area, information which is very important for climate change research. Albedo describes the ability of the Earth’s surface to reflect incoming radiation, and it is therefore associated with the Earth’s energy balance. Estimates of albedo affect the accuracy of model calculations pertaining to climate change, but they are also a good indicator of the change that has already taken place.
The surface albedo of Arctic regions is particularly important with respect to climate change, because changes in the extent of the ice cover in polar regions are crucial for albedo values. The albedo of the Arctic sea area is still relatively poorly known, but it has a major impact on climate model calculations. With global warming, the melting of sea ice reduces albedo values in the Arctic region. This means that more energy is absorbed in the region and more ice will melt. In other words, a decreasing albedo value will lead to climate feedback diminishing the albedo value further.
When compared against the conventional optical method, the microwave-based method for estimating albedo has the advantage that neither cloudiness nor the low Sun angle in the Arctic region interfere with the measurements. For instance, it is possible to detect whether spring is coming unusually early; this is something that optical instruments do not necessarily reveal at that time of year.
Albedo indicates how much of the radiation reaching a body is reflected back. The whiter the reflecting surface is, the higher is its albedo. A black body does not reflect any incoming light, and so its albedo is zero. A planet’s albedo is important in terms of thermal economy. Clouds and ice are good reflectors of solar radiation. About one third of radiation reaching the Earth is immediately reflected back to space, while two thirds is absorbed by the atmosphere, soil and seas. This radiation is also reflected back, but more slowly.
Terhikki Manninen, Research Scientist, tel. (09) 1929 4159, firstname.lastname@example.org