The RHUBC-II Campaign: Analysis of Downwelling Infrared Radiance

David Turner National Oceanic and Atmospheric Administration
David Tobin University of Wisconsin, Madison
Eli Mlawer Atmospheric & Environmental Research, Inc.
Jennifer Delamere Tech-X Corporation

Category: Radiation

Working Group: Cloud Life Cycle

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A comparison between the AERI-observed downwelling infrared radiance from 14.3 to 20 µm during RHUBC-II and a calculation using the line-by-line radiative transfer model LBLRTM. The LBLRTM incorporates the knowledge learned during the RHUBC-I experiment in 2007. The precipitable water vapor in this case is 0.52 mm, which is about 2 times drier than the driest case observed during RHUBC-I.

Radiative heating and cooling are important drivers of Earth’s climate. In the mid-to-upper troposphere, the dominant radiative processes in both the solar and thermal regimes are due to water vapor. In order to properly model the atmospheric circulation, the radiative transfer models used within GCMs in the strong water vapor absorption bands, which are spectral regions that drive mid-to-upper tropospheric heating, must be accurate. The Radiative Heating in Underexplored Bands Campaigns (RHUBC-I and RHUBC-II) were conducted under the auspices of the ARM Climate Research Facility to collect the data needed (e.g., accurate water vapor profiles and spectrally resolved radiance observations) to evaluate and improve detailed radiative transfer models in the strong water vapor bands. This study will focus on the analysis of the radiance observations in the 6.7 µm vibrational water vapor band and the rotational water vapor band in the far-infrared (wavelengths longer than 15 µm) using data collected during RHUBC-II, which was conducted at an altitude of 5380 m in northern Chile. The precipitable water vapor was as low at 0.2 mm (approximately 100 times less than a typical SGP value), which resulted in the normally opaque far-infrared region of the spectrum being semi-transparent from 16-43 µm. This provides a unique opportunity to evaluate the water vapor absorption line parameters and the water vapor continuum absorption model in this region of the spectrum.

This poster will be displayed at ASR Science Team Meeting.

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