Abstract
A radio acoustic sounding system (RASS), coupled with the NOAA/Wave Propagation Laboratory 915-MHz wind profiler, observed an arctic front and arctic air mass that passed over Denver, Colorado, between 1 and 5 February 1989. The RASS temperature measurements extended to approximately 1.5 km above ground level and were taken at 15-min intervals during the frontal passage and at 1-h intervals thereafter. During the frontal passage on 1 February, the RASS documented a temperature decrease of >15°C. The succeeding cold air (∼−20° to −40°C) over Denver never exceeded 1.3 km in depth. The frontal inversion at the top of the cold air mass was 300 m in depth and possessed large static stability [−∂θ/∂p ∼ 80 K (100 mb)−1] and vertical wind shear [∂V/∂p ∼ 30 m s−1 (100 mb)−1]. Temporal fluctuations (∼3 h) in the depth of the cold air were observed by the RASS between the operational 12-h rawinsonde observing periods. Simultaneous RASS and rawinsonde measurements showed good agreement with regard to key thermal features.
