Radiation processes, such as the absorption of radiation by water vapor and clouds, must be parameterized accurately in global climate models (GCMs), as inaccurate radiation parameterizations can lead to large errors in GCM simulations. One of the largest sources of uncertainties in these radiation parameterizations is the magnitude of the water vapor continuum absorption. If the modeled continuum absorption is too strong or weak, then the model atmosphere will radiate at a different level in the vertical, which will impact the local vertical circulation and potentially the larger scale planetary circulation in the simulation.
This presentation will present a story about how ground-based spectral radiance observations were used to improve the water vapor continuum model in the far-infrared (wavelengths longer than 15 µm). The radiation emitted in far-infrared portion of the spectrum is about 40% of the total outgoing longwave radiation (OLR) emitted by the planet. Also, the absorption by water vapor in the far-infrared plays a critical role in the vertical heating of the atmosphere, which drives local vertical motions and impacts the planetary circulation. The story starts with the basic radiometric observations themselves, the subsequent improvement of the water vapor continuum model, the use of submillimeter and far-infrared spectroscopic observations to evaluate the updated radiative transfer model in a new environment, and the demonstration of the impact of the improved model on a GCM simulation.
613 Seminar Series Committee: