A Tethered Lifting System (TLS) designed and operated by the University of Colorado's Cooperative Institute for Research in Environmental Sciences (CIRES) was incorporated as an in situ sampling technology during CASES-99 near Wichita, Kansas (USA) in October 1999. The TLS used both kites and aerodynamic blimps as lifting platforms for profiling a number of atmospheric variables between 0-1000 m for studying the nighttime stable boundary layer. Typical operation involved suspending up to five individual sensor packages from the TLS tether at predetermined separations between 3 m and 12 m. Each sensor package included a hotwire probe (mean wind speed and velocity turbulence structure), a coldwire probe (mean temperature and temperature turbulence structure), and additional devices to measure mean wind direction and atmospheric pressure. Calibration of both the hotwire and coldwire sensors was accomplished, respectively, by incorporating a pitot tube and a solid-state temperature sensor on each turbulence package. Additional variables (pressure, temperature, humidity, etc.) were recorded by a basic meteorological package (BMP) attached below or above the string of turbulence packages. All data were stored digitally onboard each sensor package at 200 Hz (hotwire and coldwire data) or 1 Hz (pitot tube, solid-state temperature sensor, and pressure). These data were downloaded at intervals when the TLS was brought down to ground level.

Calibration of the turbulence quantities was accomplished in subsequent analyses as follows: For the temperature fluctuations, a careful spectral matching of the coldwire data and the solid-state temperature sensor data over a reasonable range of frequencies provided temperature accuracies of a fraction of a degree (K); For the hotwire fluctuations, the low-frequency pitot tube data were merged with the hotwire data using King's law. This merging was done manually over relatively long data periods, since the King's law parameters changed slowly with changing conditions (e.g., a change of the hotwire parameters and/or other conditions with time). This careful matching yielded mean wind speed and velocity fluctuation accuracies typically better than 0.1 m/s.

We present here an example of an extremely steep temperature gradient (28 K/m) at an altitude of 180m observed as the TLS probes ascended and descended through that level on one particular night. This temperature gradient was observed to last for at least twenty minutes, although the magnitude of the gradient became less with increasing time. Concurrent profiles of the temperature structure constant (C_t²), the energy dissipation rate (e), and the temperature innerscale of turbulence (l₀) will also be shown. We also present additional evidence for a very steep turbulence gradient observed on a different night that remained fixed in altitude for many minutes. This observation was made with four turbulence probes at a constant altitude, with each probe separated from the adjacent probes by twelve meters.