Investigation of the atmospheric surface layer using a novel high-resolution sensor array

Abstract

Representing land-atmosphere exchange processes as lower boundary conditions remains a challenge in numerical weather predictions. One important reason is the lack of understanding of heterogeneities in topography, land cover, stability, and their effects on all aspects of the flow field and scalar transport. Well-resolved flow measurements can shed light on these near-surface processes, yielding improved modeling approaches. Yet, it is precisely the heterogeneous characteristics in question—along with the large separation of scales—that make field measurements notoriously challenging. To address some of the difficulties encountered in probing the atmospheric surface layer, a unique and economically scalable field measurement platform was designed around the nanoscale thermal anemometry probe technology, which has previously been used successfully at high Reynolds numbers in laboratory settings. The small size of the nanoscale sensors not only provides a high spatial resolution but also allows for velocity and temperature measurements with the same constant current operating circuit. This operating mode is more economical and straightforward to construct than conventional constant temperature anemometry systems, providing a scalable platform for multi-point measurements. The measurement platform was deployed at the Surface Layer Turbulence and Environmental Science Test site in Utah’s West Desert as part of the Idealised horizontal Planar Array study for Quantifying Surface heterogeneity. Streamwise velocity and temperature data were acquired within the first meter above ground with good agreement in spectral behavior to well-known scaling laws in wall-bounded flows.