Airborne multifrequency L- to Ka-band radiometric measurements over forests

Microwave radiometric measurements using airborne instruments in a frequency range from L- to Ka-band were carried out over six broad-leaved and one coniferous forest stands in Tuscany, Italy. Ground measurements of the main tree parameters were performed on the same stands. The analysis of the collected data indicated that the use of microwave emission at the highest frequencies makes it possible to identify some forest types, whereas L-band emission is more closely related to tree biomass. The relationships between emission and some significant tree parameters such as leaf area index, basal area, woody volume, and crown transparency are presented and discussed. The significant relationship between L-band emission and woody volume is further analyzed by means of a first-order radiative transfer model.