Vertical Cloud Structure in a Midlatitude Cyclone from a 94-GHz Radar

Abstract

The vertical structure of clouds associated with a developing midlatitude cyclone was studied using a 94-GHz cloud radar accompanied by a host of other surface-based instruments and rawinsondes. A thickening cirrostratus deck was observed as the storm approached. As the storm drew near, low-level moisture advection increased, and a drizzle-producing stratus deck quickly developed. A rather lengthy period of light to occasionally moderate rain accompanied the passage of the storm. When the storm pulled away to the northeast and the rain ended, the character of the stratus deck changed markedly, with no drizzle production evident. Other cloud features observed included generating cells and their resultant fallstreaks and an ?eye? that apparently accompanied the passage of a negatively tilted upper-level trough, as evidenced by measurements from a 50-MHz wind profiler located near the cloud radar. Rawinsonde measurements showed that the cloud radar also traced the descent of the melting layer. Satellite observations indicated that attenuation often limited the ability of the radar to detect cloud top when precipitation was occurring. As a result, the radar-reported cloud tops were 2?5 km lower than those indicated from the satellite cloud-top temperatures during the heaviest precipitation. During very light precipitation and precipitation-free periods, the satellite brightness temperatures yielded slight underestimates of cloud-top height. In spite of the attenuation, the cloud radar revealed many detailed structures of the clouds of a fairly typical midlatitude cyclone and captured the entire 3-day event.