Observations of the Temperature and Humidity Structure Parameter Over Heterogeneous Terrain by Airborne Measurements During the LITFASS-2003 Campaign

The turbulent structure parameters of temperature ((Formula presented.)) and humidity ((Formula presented.)), and their cross-structure parameter ((Formula presented.)), are investigated using data collected with the airborne-measurement platform Helipod during the LITFASS-2003 campaign. The flights took place within the atmospheric surface layer over heterogeneous terrain including forests, a lake and farmland. We find variability in (Formula presented.) along such flight legs, with values of (Formula presented.) over forested surfaces one order of magnitude larger than over farmland, and two orders of magnitude larger than over the lake. However, a quantitative relationship between the magnitude of (Formula presented.) and the surface type is not found, most likely due to a similar surface latent heat flux between the land-use types. However, when the different flight legs are taken together and data grouped by land-use type, values of (Formula presented.) are significantly lower over the lake than over the other surfaces. A classification of (Formula presented.) is only possible between water and land surfaces, with lower values over water. We find the correlation coefficient (Formula presented.) in the range of 0.4–1.0, which is less than unity, and thus violates the assumption of unity in Monin–Obukhov similarity theory.