MOAS

Microwave Oxygen Absorption Study (MOAS)

1 August 2009 - 31 October 2009

Lead Scientist: Susanne Crewell

Observatory: SDS - OSC

The RHUBC-II experiment to Cerro Toco, Chile, aimed at the validation of gas absorption models over a wide wavelength range. The microwave radiometer HATPRO measured the thermal emission of the atmosphere due to water vapour and oxygen in 7 channels from 22.2 to 30 GHz and 7 channels from 52 to 58 GHz. Special care was taken to exactly characterize the channels bandpasses and to properly caibrate the observations to brightness temperatures. The strong oxygen absorption complex in the range 55 to 65 GHz consisted of multiple absorption lines, and there was uncertainty in the absorption line parameters. This uncertainty affected water vapor and liquid water retrievals that use 23 and 31 GHz observations, as there was still significant absorption at these lower frequencies due to the wings of the oxygen lines around 60 GHz. HATPRO made observations at the greatly reduced ambient pressure (order 520 mb) to thouroughly investigate the spectroscopy of the 60 GHz oxygen absorption band in conjunction with the atmospheric state measurements from the radiosondes that were launched during RHUBC-II.