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Micrometeorology group web page – WELCOME

The coupling of the Earth's surface and the overlying atmosphere through mass and energy fluxes has an important role in atmospheric chemistry and physics in addition to boundary layer meteorology and ecosystem research. Our research group aims at increasing the fundamental understanding of atmosphere-biosphere coupling for different ecosystems and surfaces and to apply the gained information for practical applications and purposes.

 

 

 

 

Background of our work

Meteorological research can be divided into three groups according to the size of the phenomenon in concern. Global meteorology looks into global scale phenomena, synoptic meteorology explores phenomena the size of weather systems and micrometeorology aims at the understanding of phenomena near the ground with sizes ranging from a couple of hundred kilometers to less than a millimeter. Despite their small scale, micrometeorological phenomena play an important role for instance in global climate models and numerical weather prediction models since the models are still lacking the contribution of the small scale phenomena. Micrometeorological phenomena occur in the atmospheric boundary layer, the 10-2000 meter high atmospheric layer close to the ground. In this layer, air flow is almost always turbulent, that is, the flow field consists of chaotic, three dimensional swirls of motion. Consequently, the physical understanding of boundary layer processes is exceptionally challenging.

The atmosphere and the surface are coupled to each other through turbulence-induced vertical flows (fluxes) of momentum, mass and energy. The surface, in this context, includes the surface itself, its vegetation and potentially also buildings. Momentum flux becomes apparent for instance as shear stress when the wind bends trees. Mass flux, on the other hand, can be thought as a vertical flux of air pollutants or green house gases such as methane and water vapor. Such a flux can be caused e.g. by a methane flow from a fen to the atmosphere or by transpiration of a tree. In the latter case, the flux is closely connected to tree physiology. A heat flux composes of a sensible heat flux and a latent heat flux where the energy is "hidden" in the water phase and will be released in phase transition. An example of a heat flux could be sensible heat rising from a warmer lake to the overlying colder air. The fluxes between the surface and the atmosphere depend largely on the surface type and thus research concerning different land use types is needed.

The largest portion of Finland's surface area is covered by forestry land (metsätalousmaa) (77%, 26milj. ha) from which one third is covered by wetlands. The success of trees is partly based on their capability to interact with the surrounding air. The boreal forest is the most widespread vegetation type in the northern hemisphere: the forests of Eurasia cover 900milj. hectares of land. Lakes comprise a much smaller area of Finland (10%) and the boreal zone (7%). The contribution of urban areas in Finland is very minimal but it must be kept in mind that currently half of the world's population lives in cities and by 2050 the portion may have risen to 70%.

 

 

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