Measurements and Retrievals From a New 183-GHz Water-Vapor Radiometer in the Arctic

A new G-band (183.31-GHz) water-vapor radiometer, developed and built by ProSensing Inc., was deployed in Barrow, AK, in April 2005. The radiometer is part of a suite of instruments maintained by the Atmospheric Radiation Measurement program. The instrument measures brightness temperatures from four double-sideband channels centered at plusmn1, plusmn3, plusmn7, and plusmn14 GHz from the 183.31-GHz water-vapor line. Atmospheric emission in this spectral region is primarily due to water vapor, with some influence from liquid water. In this paper, data collected in November 2005, December 2005, and January 2006 are analyzed. Measurements are compared with simulations obtained by using a radiative transfer model. We show that the measurements agree well with model simulations. Precipitable water vapor (PWV) and liquid water path (LWP) are retrieved with a nonlinear physical algorithm, and results are compared with those from the colocated dual-channel microwave radiometer and radiosondes. Retrieval errors are estimated to be below 5% for PWV and of the order of 0.006 mm for LWP.