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 ( C_T^2 ) and humidity ( C_Q^2 ), and their cross-structure parameter ( C_QT ), 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 C_T^2 along such flight legs, with values of C_T^2 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 C_Q^2 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 C_Q^2 are significantly lower over the lake than over the other surfaces. A classification of C_QT is only possible between water and land surfaces, with lower values over water. We find the correlation coefficient R_QT 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.