The Micro Rain Radar (MRR)¹ is a compact, vertically pointed radar that is designed to measure the vertical profiles of drop size distributions. From the drop size distributions, several parameters can be derived, including the characteristic fall velocity resolved into 30 range gates, the liquid water content, the rain rate, and reflectivity. It operates at a frequency of 24.1 GHz FM-CW and has a transmit power of 50 mW. The radar system consists of an antenna dish, radar, receiver unit, and a RS-232 data transmission interface.

The MRR detects very small amounts of precipitation that are below the threshold of conventional rain gauges. Also, the MRR provides information for now-casting of precipitation, as it detects the start of rain or snow from ground level up to 6 km above the radar anywhere from several minutes to more than two hours before the onset of precipitation at ground level

The ability of the MRR to detect the bright band, or height of the freezing level above ground, during winter storms is one main reason RENCI (Renaissance Computing Institute)² acquired a MRR for testing in North Carolina. A second reason is to study MRR rainfall intensity and accumulation measurements across the state. This paper examines the MRR rainfall intensity measurements in North Carolina and compares this data to weather station (Vaisala WXT510) and disdrometer (OTT Parsivel) data. Data collected during typical stratiform and convective events are studied and special emphasis will be placed on any data collected during tropical storms that affect North Carolina during 2008. By comparing these measurements, we can determine the capability of the MRR to accurately measure rainfall. We can then use this knowledge as a basis for future work to study Z-R relationships used by National Weather Service radars in North Carolina.

One unique feature of the RENCI MRR is that it is mounted on a small trailer to allow it to be easily transportable. This mobility allows the radar to be moved to various locations around the state as determined by an approaching weather event such as a tropical storm or winter weather event. The trailer has a leveling system so that the radar is always vertical when sampling and an enclosure to protect the electronics that collect and report data in real-time. The trailer also includes a camera, the previously mentioned weather station and laser disdrometer, and a GPS to determine the location and elevation of the radar. The MRR and accompanying sensors operate continuously at various locations around North Carolina based on the season. All data collected on the trailer is sent back to RENCI in real-time using wireless broadband and posted on a live web page.

¹ Manufactured by Metek GmbH and distributed by Bristol Industrial and Research Associates Ltd. (Biral)

² RENCI is a North Carolina state organization that is a joint venture of the University of North Carolina Chapel Hill, North Carolina State University, and Duke University. RENCI works to use technology to solve multidisciplinary problems in North Carolina.