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

At an elevation of more than 5000 meters and peaks rising to 5500 meters, the Chajnantor 
    Plateau in Chile is a popular spot for atmospheric and astronomical research.
At an elevation of more than 5000 meters and peaks rising to 5500 meters, the Chajnantor Plateau in Chile is a popular spot for atmospheric and astronomical research. The RHUBC-II field campaign will take place at an elevation of 5383 meters on Cerro Toco, a mountain near the border of Bolivia and Argentina. (Larger image.)

The second phase of the Radiative Heating in Underexplored Bands Campaign (RHUBC-II) takes place on Cerro Toco, a mountain rising from the Chajnantor Plateau in Chile. From August to October 2009, nearly a dozen instruments will operate continuously to obtain measurements—such as temperature, pressure, humidity, and incoming and outgoing energy—for characterizing the atmospheric state. In addition, a combination of several spectrometers—highly sophisticated optical instruments used to measure the properties of light over a specific portion of the electromagnetic spectrum—will obtain measurements from the infrared region of the spectrum.

Water vapor strongly absorbs solar and infrared energy in many bands throughout the electromagnetic spectrum.  In these spectral regions, the atmosphere is essentially opaque at most surface locations around the earth.  However, these spectral regions are very important to the absorption of energy in the middle-to-upper troposphere, where there is significantly less water vapor, and any errors in the strength of this absorption will result in errors in the modeling of the earth's climate.

The Chajnantor plateau, which is located high in the Atacama desert, is one of the driest places in the world.  At this location, these spectral regions where water vapor absorbs will be partially transparent. Thus, the accuracy of the models used to predict the absorption can be evaluated there.

Detailed information obtained from this field campaign is expected to greatly reduce uncertainties in the treatment of middle and upper tropospheric moisture in the radiation calculations used in global climate models. This effort is a follow-on to RHUBC, conducted in 2007 at the ACRF North Slope of Alaska site in Barrow.