Atmospheric Surface Layer Turbulence and Profiles, Measurements from PECAN FP2 Site at Greensburg, Kansas

As part of the Plains-Elevated Convection at Night (PECAN) field campaign, we made extensive measurements at Greensburg, Kansas, the #2 fixed location PECAN Integrated Sounding Array (PISA) site (FP2), from June 1 to July 15 2015. The measurements and the analyses to be discussed in this presentation include those made from a 16-m flux tower, a nearby 6-m tripod flux tower, and 3-m tripod tower. The 16-m flux tower was outfitted with four levels of 3-D sonic anemometer and fast hygrometers to measure turbulence and scalar perturbations, six levels of mean wind measurements, and twelve levels of temperature and humidity measurements. The 6-m flux tower made similar turbulence measurements at the same two lowest levels as the 16-m tower at a nearby location. Since the 16-m tower was situated on a 1.3 m × 1.3 m concrete foundation, both near-surface temperature and humidity were sampled from a small 3-m tripod tower at six levels below 2.5 m with three levels of concurrent soil temperature and two levels of soil moisture measurements. A sonic detection and ranging (SODAR) device was also setup at FP2 together with a laser ceilometer. The SODAR measurements provided a vertical profile of mean wind and turbulence continuously up to approximately 250 m above the surface. In addition, we deployed an instrumented tethered balloon system that made profiling measurements in the atmospheric surface layers on selected evening/nights whenever balloon operation was feasible. The objective of the tethered balloon measurements was to capture the evolution of the surface layer during the transition period between the daytime convective boundary layers and the stable nocturnal boundary layers that lead to the establishment of the nocturnal low-level jet (LLJ). In this presentation, we will focus on the properties of the atmospheric surface layers seen from the suite of sensors at FP2, particularly on the evolution of turbulence fluxes and their vertical variation in the surface layer, the corresponding surface layer profiles from the surface up to 16 m and possibly to a couple of hundred meter with the measurements from the SODAR, and from the tethered balloon system. The development of the low-level Jet at night, the transition from the convective boundary layers to the stable boundary layers, and the influence of the convective systems on the surface layer physics will also be discussed using the FP2 measurements. Additionally, a thorough examination of the stable surface layer flux-profile relationship using this suite of measurements will be made and subsequently compared with empirical relationships from many previous field experiments.