High resolution modeling of the far-infrared spectra of the Earth's atmosphere

Recent studies, based upon monochromatic calculations, have established that over 40% of the thermal energy escaping from the Earth's atmosphere-surface system is emitted to space within the spectral range extending from 100 to 650 cm^-1 (100 to 15.4 microns). Known as the far-infrared, this portion of the spectrum is dominated by the line and continuum spectral features of the pure rotation band of water vapor. In addition to being the principal greenhouse gas in the Earth's atmosphere, water vapor is also one of the most spatially and temporally variable of the atmospheric trace species. Recent studies have further revealed that when compared to other spectral ranges, the far-infrared water vapor absorption and emission both provide the greatest sensitivity of the outgoing thermal radiation to perturbations in upper tropospheric humidity, and play a prominent role in determining the rate of cooling throughout the free troposphere. Despite the magnitude of this far-infrared contribution, however, very few spectrally-resolved measurements of the Earth's atmosphere-surface system have been taken from space-based instruments. As part of the National Aeronautics and Space Administration (NASA) Instrument Incubator Program (IIP), the Far-Infrared Spectroscopy of the Troposphere (FIRST) project developed an instrument capable of measuring the spectrum over the range from 100 to 1000 cm^-1 (100 to 10 microns). With a highly successful balloon flight launch from Ft. Sumner, NM on 7 June 2005, FIRST has opened a new window on the spectrum for studying atmospheric radiation and climate, cirrus, and water vapor in the upper troposphere. This talk reviews the high resolution modeling effort being done in support of the far-infrared studies at Langley Research Center.