RHUBCII

Radiative Heating in Underexplored Bands Campaign 2 (RHUBC-II)

14 August 2009 - 24 October 2009

Lead Scientist: David Turner

Observatory: AMF , OSC

The Radiative Heating in Underexplored Bands Campaign (RHUBC-II) was selected for support by ACRF as an off-site campaign. Led by principal investigators David Turner and Eli Mlawer, RHUBC-II took place from August to October 2009 at a location near Cerro Chajnantor in Chile, at an altitude of more than 5,000 m. This effort was a follow-on to RHUBC-I, conducted from February 22 to March 14, 2007, at the ACRF North Slope of Alaska site in Barrow. During RHUBC-II, the same spectral band was explored; however this absorption bands was much more transparent in the dry, low pressure conditions at Chajnantor. These conditions represent the upper troposphere that is poorly observed but important for climate studies. Therefore, significant fundamental advances that are pertinent to reducing uncertainties in the radiation calculation of global climate models were gained. Science Objectives:

• To conduct clear-sky radiative closure studies in order to reduce the key uncertainties in the water vapor spectroscopy, including the foreign-broadened water vapor continuum and water vapor absorption line parameters. This campaign will provide a dataset with extremely low water vapor conditions (precipitable water vapor at the Chajnantor Plateau is generally less 1 mm) collected at nearly typical mid-tropospheric temperatures and pressures.
• The investigation of the radiative properties of cirrus in the far-infrared using the spectrally resolved observations from the ground-based interferometers. The micropulse lidar (MPL) will provide accurate cloud boundaries for the infrared calculations, as well as cirrus optical depth, which will maximize the scientific value of this data set.