July 10, 19971aSerabyn/Abstract ATM-9616766 Accurately calibrated measurements of atmospheric opacity across the near-millimeter and submilimeter wavebands (3 - 0.3mm) are proposed. The measurements will be carried out using a Fourier transform spectrometer at the Caltech Submillimeter Observatory on the summit of Mauna Kea. The broadband natrue of the spectrometer will enable measurements covering up to a decade in frequency, while the high altitude site will provide access to extremely dry atmospheric conditions, allowing through-atmosphere observations at frequencies well above those possible from seal level. The goal of this project is to relate the measure braodvand atmospheric opacity curves to the atmospheric water vapor content, in order to address issues such as the collisionally broadened lineshape of the H2O molecule, the "quasi-continuum" H2O opacity contribution far from resonance, and ultimately, the dry-air contribution to the continuum opacity. A better understanding of the H2O collisionally broadened lineshape is important not only as a discriminator of collisional lineshape models, but also because of the significant impact water vapor opacity has on radiative transfer and energy balance in our atmosphere, and on the propagation of radiation in remote sensing and communications applications.
