GLORY OF CLOUDS IN THE NEAR-INFRARED

Spectrally resolved visible and infrared images of marine stratus clou ds were acquired from the NASA ER-2 high-altitude aircraft during the 1987 First International Cloud Climatology Program Regional Experiment . The images were obtained by cross-track scanning radiometers. Data i mages at near-infrared wavelengths show frequent and readily apparent brightness features that are due to glory single scattering. The obser vations and subsequent analysis by radiative transfer calculations sho w that the glory is a significant feature of near-infrared solar refle ctance from water clouds. Glory observations and calculations based on in-cloud microphysics measurements agree well. The most dramatic diff erence from the visible glory is that the scattering angles are signif icantly larger in the near infrared. The glory is also apparently more distinct in the near infrared than in the visible, as scattering size parameters are in a range that effectively produces a glory feature, and also there is less obscuration by multiple-scattering reflectance because of absorption of radiation by droplets in the near infrared. F or both the visible and the near infrared, the principal factors that wash out the glory are dispersion and, to a lesser degree, the effecti ve radius of the cloud droplet-size distribution. The obscuration by m ultiple scattering in optically thick clouds is secondary. Rather than being a novelty, glory observations would be an accurate and unambigu ous technique to sense the droplet size of water clouds remotely.