Closure Analysis Using ARM Spectral Radiation Measurements

Description

Comparisons between spectrally resolved measurements and radiative transfer model calculations are effective at improving our understanding of atmospheric gas, cloud, and aerosol properties. This presentation will provide details of recent radiative closure studies using spectral measurements from the ARM Radiative Heating in Underexplored Bands Campaign (RHUBC-II) in Chile and new shortwave instruments at SGP. The ARM Program conducted RHUBC-II in Aug-Oct 2009 to improve knowledge of emission and absorption of water vapor in the mid-to-upper troposphere, most notably water vapor transitions in the far-infrared. This campaign was situated at a site at 5400m in the Atacama Desert of Chile -- precipitable water vapor (PWV) values as low as 0.2 mm were observed during clear periods, a necessary condition for observing spectral features in the normally opaque far-IR. The methods used to retrieve accurate water vapor and temperature profiles from RHUBC-sondes and radiometric measurements will be presented, as will the results from far-IR comparisons between LBLRTM calculations and measurements from the Radiation Explorer in the Far Infrared (REFIR). This presentation will also detail clear-sky radiative closure studies performed with available measurements from the hemispheric and zenith Shortwave Array Spectroradiometers (SAS-He and SAS-Ze, respectively). Calculations with LBLRTM/CHARTS with derived and available aerosol properties will be compared with measurements from these instruments.