Scintillometer fluxes of sensible and latent heat over a heterogenous area—a contribution to LITFASS-2003

Surface fluxes of sensible heat (H) and evaporation (L_vE) are important in many atmospheric processes and can be measured with reasonable accuracy over homogeneous areas. However, surface fluxes that are representative for large natural landscapes (comparable to the grid box size of numerical models or satellite remote sensing pixels) are more difficult to determine because at these scales the earth’s surface is always heterogeneous.

The scintillation technique is one of the few techniques that can provide fluxes at scales of several kilometers (10 km). For example the combination of a large aperture optical scintillometer (LAS) and a radio wave scintillometer (RWS), also known as the two-wavelength method, can provide the fluxes of both H and L_vE at kilometer scales.

So far there have been only a few experiments with (optical) scintillometers operated over heterogeneous terrain and only one experiment that systematically investigated the two-wavelength method (see Boundary-Layer Meteorology special issue on scintillomerty, volume 105, 2002).

In this study we will present the results of scintillometer measurements carried out during the LITFASS-2003 experiment using three large aperture scintillometers (LAS) and one radio wave scintillometer (RWS). All scintillometers were installed in different parts of the Lindenberg area (20 x 20 km²). The orography of the Lindenberg area has been formed by inland glaciers during the last ice age and is characterized by slight, irregular undulations and a number of small lakes. The land use consists of 42% forest, 47% farmland, 7% open water and 4% villages, making it an ideal heterogeneous area for testing the scintillation technique. The scintillometers were installed as follows:

One LAS and the RWS were installed over a path length of 4.7 km. The source area of the scintillometers consists roughly of 10% forest and 90% farmland. The second LAS was installed over a homogenous forest (path length 3 km). Finally, and extra large aperture scintillometer (XLAS) was set-up over a path length of 10 km. The source area of the XLAS consists roughly of 70% forests and 30% farmland.