The Desert Research Institute Atmospheric Sciences Center currently has three dual-channel microwave radiometer systems. All are passive systems operating at frequencies of 20.6 and 31.65 GHz. They are designed to measure and record the total integrated amount of liquid water and water vapor along the beam path of the instrument. The systems have been used for atmospheric research in all seasons, but have been mainly used in weather modification research and operations to detect supercooled liquid water in winter storm conditions.

All three radiometers are capable of taking long-term unattended measurements when operated in a zenith-looking mode. Two systems are capable of azmuthal scanning, with the newest system capable of rapid scans using slip ring data transfer technology. The newest system is a completely mobile radiometer (photo on the left) capable of recording data in zenith mode while traversing normal roadways, and has been used to map the distribution of supercooled liquid water over several mountain barriers during winter storms. This mobile system uses GPS to continuously record its position. The example data plot shows liquid depths measured over the Sierra Nevada.

To the right is a picture of the DRI Ka-band radar taken during a wintertime field research project in central Utah. A PC-based computer controls data acquisition and antenna funtions. The antenna control includes zenith-pointing operation, azimuthal volume scans, sector scans, range-height scans, specific elev/azimuth recording and raster scans. The primarly operating characteristics of the radar are as follows:

Antenna:	Cassegrain-1.6m		Peak Power:	100KW
System Gain:	50 dB		Wavelength:	0.86 cm
Beam Width:	0.5 deg (conical)		Pulse Width:	0.5msec
Scan Rate:	12 deg s-1		PRF:	1000 s-1
Range Gates:	512		MDS:	-101 dBm
Gate Spacing:	75 m

Data can be recorded to hard disk or to an 8 mm exabyte tape drive. The data acquisition rate is 30-60 Mbytes per hour.

The figure shows the full screen radar display with a PPI image.