A high-resolution oxygen A-band spectrometer (HABS)

Description

An important challenge is to detect three-dimensional (3D) structures of clouds and aerosols and their effects on radiative transfer. Current ability to resolve 3D cloud structure is limited to scanning pulsed active sensors and imaging instruments, not at the scale of radiative transfer of horizontal and vertical inhomogeneity. An oxygen A-band spectrometer provides a basis for applications of path length distribution in development and validation of remote sensing and radiative transfer parameterizations that account for 3D effects. To face the challenge, a high-resolution oxygen A-band spectrometer (HABS) has been developed and well tested at State University of New York. The HABS has the capability to measure both zenith and direct-beam radiances with a field of view of 2.7 degrees. The direct-beam measurements can be used to calibrate the spectrometer and construct retrieval kernels for zenith measurements. HABS also measures polarizations of A-band spectra with four polarizers, which substantially enhances the retrieval ability for aerosols and ice clouds. Our tests indicate that HABS achieves an out-of-band rejection of 10-5, a resolution of better than 0.3 cm-1, and a high signal-to-noise ratio. It is ready for a field campaign at the ARM SGP site to demonstrate its capability in radiative transfer and remote sensing applications.