Abstract
Much progress has been made toward modeling the spectral infrared
(IR) emissivity of wind-roughened water surfaces. Existing
emissivity models explicitly calculate the ensemble mean
emissivity of the wavy surface for a given observer zenith angle
and local wind speed. However, field observations of emissivity
spectra obtained by the Marine Atmospheric Emitted Radiance
Interferometer (M-AERI) suggest that emissivity models are
deficient at larger view angles and wind speeds. In this
preliminary work, we attempt to identify and explain the sources
of error in these models using M-AERI data acquired at sea (e.g.,
during AEROSE 2004). Our results demonstrate that proper
accounting for non-unity surface emissivity must ultimately
include appropriate specification of the reflected IR radiation
field, especially in window channels. Atmospheric IR surface
reflectance becomes important for high accuracy applications
(e.g., sea surface skin temperature), that rely on window channel
observations at zenith angles 45 deg. Lookup tables of
ensemble mean effective incidence angle, rather than mean
emissivity, are generated using different published mean square
slope PDF models. These results roughly agree with recent
findings. Lookup tables of ensemble mean local zenith incidence
angle are also generated. This new approach to
emissivity/reflection modeling will be refined and validated
against M-AERI field data from several previous oceanographic
cruises, and will be the subject of a forthcoming paper.