Boulder Atmospheric Observatory - Completed in 1977, the BAO is a unique research facility for studying the planetary boundary layer and for testing and calibrating atmospheric sensors. The centerpiece of the facility is a 300-m tower instrumented at five levels with slow-response temperature and wind sensors, a variety of remote sensing systems, and a real-time processing and display capability that greatly reduces analysis time for scientists. The BAO has been the host of several large national and international experiments and numerous smaller ones.