Flux and Profile Measurements from Towers in the Boundary Layer

Towers offer convenient platforms for observing mean and turbulent properties of flow in the atmosphere’s boundary layer. Much of what we know about the structure of this layer comes from measurements made with sensors mounted on towers. All varieties of structures, from short masts to very tall television towers, have been used for this purpose. Sensors have become more sensitive and accurate over the years, methods of recording and analyzing data have advanced dramatically, but the design of towers has not changed significantly. Many of the problems associated with tower measurements, such as flow distortion induced by the structure, are therefore still with us. The Eulerian nature of the observations may be appropriate for some studies, but for others Taylor’s hypothesis, with all its uncertainties, has to be invoked to convert the observed time scales into spatial scales. These limitations have seldom dissuaded researchers from using towers-indeed, the convenience of easy access to sensors for maintenance and of direct connection to recording facilities on the ground argues persuasively in favor of their use.