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Abstract
Development of high-rate turbulence sensors for high resolution measurements of the atmospheric boundary layer began in 1998 to augment the Cooperative Institute for Research in Environmental Sciences (CIRES) tethered lifting system (TLS). Cold-wire and hot-wire sensors measure with high accuracy and resolution the streamwise temperature and wind speed fluctuations. The temperature structure constant CT2 and energy dissipations rate ε are estimated with spectral processing and turbulence scaling laws. In addition, other important turbulence parameters such as the Reynolds number, Buoyancy Reynolds number, turbulent Froude number, gradient Richardson number, Ozmidov scale, and temperature inner scale are determined. The TLS is ideally suited for accurate measurements of the local gradients since the sensors slowly ascend through the atmosphere.
Over the past decade, major engineering efforts have improved the turbulence sensor package with the development of new circuit designs of higher bandwidth, lower instrumental noise, and better calibration signals. In March 2009, data was collected at the Boulder Atmospheric Observatory with the latest prototype instrument to investigate the turbulence structure of the nocturnal boundary layer and residual layer. The first results of the analysis of this data will be presented with a focus on investigating recent theories for stably stratified turbulence and the implications for future measurement systems, especially the very challenging low turbulence conditions. In addition, an overview of the new TLS equipment to be acquired in 2009 will be presented and new measurement configurations will be discussed.