ISS Observations of small-scale features and an easterly wind event during T-REX

NCAR operated three ISS (Integrated Sounding System) stations for T-REX (Terrain induced Rotors EXperiment) in Owens Valley California during the spring of 2006. These systems included a surface meteorology station and wind profiler with RASS. One of the wind profilers was MAPR (Multiple Antenna Profiler Radar), and this ISS also hosted a radiosonde system, sodar, sky camera, and ceilometer. The MAPR ISS was located near the center of the valley; a second ISS was located part-way up the western slope. The third ISS was our mobile system (MISS) and this was moved around the valley for different IOPs. This presentation will discuss small-scale features observed using the MAPR system, as well as a rare easterly wind event.

The MAPR wind profiler is capable of making fast 3-D wind measurements and frequently observed fluctuating vertical and horizontal winds with periods of just a few minutes and scales of a few hundred meters. Many of these features appeared to be sub-rotors and short-scale waves. The frequency of occurrence of these small-scale features and their duration is being examined, as well as their relationship to the larger scale activity in the valley.

Most of the T-REX IOPs focused on westerly wind events across the valley, however IOP 15 examined an easterly event. During this IOP, MISS was sited on the east side of the valley in the lee of the Inyo Mountains such that the three ISS formed a line across most of the valley. All three wind profilers observed occasional periods of reverse flow (easterlies aloft and westerlies below). Reverse flow was also seen by some of the surface stations, the sodars and soundings suggesting some widespread large-scale rotor activity. MAPR also observed smaller scale sub-rotor activity prior to the development of the larger scale reverse flow.